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1
Croot, Robert Arthur. "The characterisation and adsorption of vinyl alcohol vinyl acetate copolymers." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303767.
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Tongcher, Oychai. "Novel routes to stereoregular poly(vinyl acetate)." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620688.
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Cazotti, Jaime Caetano. "Síntese e caracterização de látices híbridos de poli(acetato de vinila)/montmorilonita - PVAc/MMT para aplicação como adesivos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/97/97136/tde-27082013-103950/.
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Este projeto de mestrado teve como objetivo a obtenção de látices híbridos constituídos de poli(acetato de vinila) (PVAc) e argila montmorilonita (MMT). O homopolímero de acetato de vinila foi sintetizado através da técnica de polimerização em emulsão na presença de diferentes tipos de argila, sendo empregada uma argila sódica (Na-MMT) e três argilas modificadas (o-MMT) com diferentes sais quaternários de amônio. Poli(álcool vinílico) (PVOH) foi utilizado como colóide protetor e persulfato de amônio (APS) como iniciador. Foi estudada a melhor condição para incorporação da argila na matriz polimérica, visando a esfoliação desta nanocarga, resultando desta maneira na formação de nanocompósitos com propriedades diferenciadas. A influência da presença das argilas foi avaliada em termos da velocidade de consumo de monômero, a qual foi acompanhada por gravimetria. Os látices foram caracterizados quanto ao diâmetro médio de partícula e polidispersidade pela técnica de espalhamento de luz (LS). O teor de coágulos do látex foi calculado por análise gravimétrica e a viscosidade analisada em um viscosímetro rotacional. Os filmes nanocompósitos foram caracterizados pelas técnicas de análise dinâmico-mecânica (DMA), análise termogravimétrica (TGA) e difração de raios X (DRX). A morfologia das partículas de látex foi avaliada por microscopia eletrônica de transmissão (MET).The goal of this project was the preparation of hybrids latexes constituted by poly(vinyl acetate) (PVAc) and montmorillonite (MMT) clays. The poly(vinyl acetate) homopolymer was synthesized via emulsion polymerization in the presence of different types of clay, one sodium clay (Na-MMT) and organically modified clays (o-MMT) with different ammonium quaternary salts. Poly(vinyl alcohol) (PVOH) was used as protective colloid and ammonium persulfate (APS) as initiator. It was evaluated the best condition for the incorporation of the clay in the polymeric matrix, looking forward the exfoliation of the nanofiller, resulting in the formation of nanocomposites with new and improved properties. The influence of clay type and loading was evaluated in terms of latex stability and monomer consumption rate. The latexes were characterized in terms of particle size diameter and polydispersity by light scattering (LS) technique. Coagulum content was determined by gravimetric analysis and viscosity was analyzed in a rotational viscometer. Nanocomposite films were characterized by dynamic-mechanical analysis (DMA), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Latex particles morphology was evaluated by transmission electron microscopy (TEM).
4
Oliveira, Mauricio Pinheiro de. "Síntesse de novos estabilizantes poliméricos do tipo poli(álcool vinilico-co-neo decanoato de vinila) para utilização na copolimerização em miniemulsão do acetato de vinila (VAc) com o neo-nonanoato de vinila (VEOVA-9)." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/97/97133/tde-04102012-120438/.
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Devido à importância industrial e tecnológica dos látices estabilizados com poli(álcool vinílico)/PVA e a dificuldade encontrada na etapa de polimerização em emulsão, na presença de monômeros hidrofóbicos e de PVA\'s com alto grau de hidrólise (>92%), a síntese de novos estabilizantes poliméricos derivados de PVA para utilização em reações de polimerização em emulsão e em miniemulsão se torna muito atraente e desafiadora. O objetivo principal deste trabalho foi sintetizar novos estabilizantes poliméricos do tipo poli(álcool vinílico-co-neodecanoato de vinila)/PVA-VV com alto grau de hidrólise e conseqüentemente com propriedades diferenciadas, para serem utilizados como estabilizantes nas reações de polimerização em emulsão e em miniemulsão do acetato de vinila (VAc) com o neo-nonanoato de vinila (VEOVA-9), visando a obtenção de adesivos com propriedades diferenciadas para colagem de madeiras. Os novos estabilizantes poliméricos foram obtidos em duas etapas: i) copolimerização em solução do VAc com o neo-decanoato de vinila (VEOVA-10); ii) hidrólise alcalina (NaOH/Metanol) do poli(acetato de vinila-coneodecanoato de vinila). As miniemulsões de VAc com VEOVA-9 com diferentes tipos de estabilizantes poliméricos foram preparadas em um homogeneizador de alta pressão do tipo \"Manton Gaulin\". Foi estudado o efeito dos estabilizantes poliméricos (PVA e PVA-VV) na etapa de emulsificação (diâmetro médio das gotas, polidispersão, estabilidade das miniemulsões) e na copolimerização em emulsão e em miniemulsão do VAc com o VEOVA-9, em processo batelada. O efeito do tipo de iniciador (persulfato de amônio/APS e hidroperóxido de tércio butila/TBHP e peróxido benzoato de tércio butila/TBPB, juntamente com o formaldeído sulfoxilato de sódio/SFS) na cinética da polimerização em miniemulsão do VAc com o VEOVA-9 foi estudado em processo semi-contínuo. A distribuição dos estabilizantes poliméricos (PVA e PVA-VV) entre a fase aquosa e a superfície das partículas de polímero (adsorvido/enxertado) foi determinada e correlacionada com a viscosidade e a estabilidade coloidal dos látices. Látices na condição ideal de cópia (1:1) das gotas de monômero para as partículas de polímero foram obtidos via polimerização em miniemulsão, apresentando propriedades diferenciadas, tais como, menores valores de viscosidade, menor concentração de coágulos e maior estabilidade de estocagem, em comparação com os látices obtidos em emulsão.Due to the technological and industrial importance of latexes stabilized with poly(vinyl alcohol)/PVA and the difficulties related to the emulsion polymerization of hydrophobic monomers and the use of PVA having a high degree of hydrolysis (> 92%), the synthesis of new PVA based polymeric stabilizers for use in emulsion and miniemulsion polymerizations becomes very attractive and challenging. The aim of this work was to synthesize a new class of polymeric stabilizer, poly(vinyl alcohol-co-vinyl neo-decanoate)/PVA-VV, with a high degree of hydrolysis and differentiated properties to be used as stabilizers in the emulsion and miniemulsion copolymerization of vinyl acetate (VAc) with vinyl neo-nonanoate (VEOVA-9), that can be used as adhesive for wood bonding. New PVA based polymeric stabilizers with high degree of hydrolysis (94 - 98%) were synthesized in two steps: i) solution copolymerization of vinyl acetate (VAc) with vinyl neo-decanoate (VEOVA-10) and ii) alkaline hydrolysis (NaOH/Methanol) of poly(vinyl acetate-co-vinyl neodecanoate). Miniemulsions of VAc/VEOVA-9 were prepared using the different polymeric stabilizers in a \"Manton Gaulin\" high pressure homogenizer. The effect of different initiators (ammonium persulfate/APS or tert-butyl hydro peroxide/TBHP and tert-butyl peroxide benzoate/TBPB in the presence of sodium formaldehyde sulfoxylate/SFS) in the polymerization kinetic was evaluated. The effect of the type and concentration of polymeric stabilizer, in the emulsification step (average diameter of drops, stability of miniemulsions) as well in the polymerizations (rate of consumption of monomers, particle size and particles number) was investigated in this work. The partition of the polymeric stabilizers between the aqueous phase and the polymer particle surface (grafted/adsorbed) was determined and correlated with the viscosity and colloidal stability of latexes. Latexes with differentiated properties such as low-viscosity, lower grits content and improved storage stability, were obtained by miniemulsion polymerization with an ideal condition copy (1:1) of the monomer droplets to the polymer particles.
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Oghide, Godwin O. "Miscibility studies of poly (methyl acrylate) poly (vinyl acetate) and poly (vinyl acetate)/ poly (vinylidene fluoride) blends using differential scanning calorimetry and fourier transform infra red spectroscopy." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1985. http://digitalcommons.auctr.edu/dissertations/3294.
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The miscibility of poly (methyl acrylate)/poly (vinyl acetate) (PMA/PVAc) and poly (vinyl acetate)/poly(vinylidene fluoride) (PVAc/PVF2) blends has been studied. Films of compositions 100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100 (w/w) were cast for each system. Films of PMA/PVAc were found transparent and those of the PVAc/PVf2 were slightly opaque. While all the compositions of the PMA/PVAc exhibit single sharp Tgs, as measured with the differential scanning calorimeter, almost all of those of the PVAc/PVF2 exhibit s1 ng1 e broad TgS. By the single Tg criterion, the PVA/PVAc and PVAc/PVF2 systems are miscible in all proportions. Fourier transform infra-red spectroscopy spectra indicate molecular interaction complex involvement in the two systems. Evidence for such interaction was found to be significant in the 80% PMA/20% PVAc and 20% PVAc/80% PVF2 compositions.
6
Cauich-Rodriguez, Juan Valerio. "Hydrogels based on poly(vinyl alcohol-vinyl acetate) blends for biomedical applications." Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267577.
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7
Khan, Shadeed. "Controlled Release of Fluoride from Poly(ethylene-co-vinyl acetate) Films." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1928.
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The development of aesthetically unattractive white spots is a concern for patients undergoing fixed orthodontic treatment. Due to poor oral hygiene during treatment, accumulation of plaque around orthodontic brackets causes bacterial fermentation reactions producing acids that dissolve the mineral enamel. Such dissolution results in white spot formation, an early sign of dental caries. In principal, to inhibit the appearance of these spots during treatment, fluoridated elastomeric o-rings might be employed. Once placed around brackets, these o-rings should release fluoride therapeutically for at least 30 days, after which the orthodontist may replace them. At the present time, such fluoride-releasing o-rings are not available. In this study, model materials for fluoride-releasing elastomeric o-rings were developed. These materials were fluoride-impregnated poly(ethylene-co-vinyl acetate) (PEVA) films. In vitro release studies of these films were conducted, assessing their capacity to deliver fluoride within therapeutic range (1.2 ≤ µg F/ring/day ≤ 51.4) for 30-45 days. Optimal sample and experimental parameters, including (1) fluoride loading in the film (wt% F), (2) overcoat thickness, and (3) temperature that provided therapeutic release, were determined. At 37°C, favorable release was observed for the following: (1) films with overcoat thickness of 0.14 mm and fluoride loadings of 3.9 wt% and 5.7 wt% and (2) films with overcoat thickness of 0.27 mm and fluoride loading of 5.7 wt%. These results are important in providing fundamental guidance for the development of o-rings that combat white spot formation among orthodontic patients.
8
Yao, Hongyang. "Microstructures of poly(vinyl acetate) studied by nuclear magnetic resonance spectroscopy." W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539623911.
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Carbon-13 NMR spectroscopy was used to investigate the microstructures of poly(vinyl acetate) prepared by solution polymerization in benzene. A series of aromatic compounds was synthesized in order to model the structures formed via chain transfer to solvent. The peaks near 126.5 and 128.5 ppm in the spectra of the polymer samples were assigned to a 1-phenyl-(2n + 1)-multi-acetoxyalkane (where n = 1, 2, 3, etc.) microstructure. The concentration of that structure obtained from NMR spectra was correlated with the concentration calculated from reported kinetic data.;Chain transfer to benzene was shown to occur by addition of the macroradical to benzene, followed by rearomatization involving loss of a hydrogen atom. No evidence was obtained for a transfer mechanism involving hydrogen abstraction from benzene, and the copolymerization of benzene with vinyl acetate also was shown to be absent. The transfer mechanism actually established accounts for the unexpectedly large transfer constant of benzene in vinyl acetate polymerization. General mechanisms are proposed for the solution polymerization of vinyl acetate in aromatic solvents.
9
Lange, Hanna. "Emulsion polymerization of vinyl acetate with renewable raw materials as protective colloids." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41019.
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Emulsion polymerizations of vinyl acetate (VAc) were performed by fully or partially replacing poly(vinyl alcohol) (PVA) with renewable materials as protective colloids or by adding renewable materials, as additives or fillers, to the emulsions during or after polymerization. The purpose of the study was to increase the amount of renewable materials in the emulsion. A total of 19 emulsions were synthesized. Different recipes were used for the synthesis. The following renewable materials were studied; hydroxyethyl cellulose (HEC) with different molecular weights, starch and proteins. HEC and starch were used as protective colloids. Proteins were used as additives or fillers. Cross-linking agent A and Cross-linking agent B were used as cross-linking agents. A total of 26 formulations were pressed, either cold or hot. The synthesized emulsions were evaluated with respect to pH, solids content, viscosity, minimum film formation temperature (MFFT), glass transition temperature (Tg), particle size and molecular weight (Mw). The tensile shear strengths of the emulsions were evaluated according to EN 204 and WATT 91. It was possible to fully, or partially, replace PVA as protective colloid with renewable materials. It was also possible to use renewable materials as additives or fillers in the emulsions. The emulsions obtained properties that differed from the reference. Generally, emulsions with HEC as protective colloid showed lower viscosity and slightly higher MFFT, Tg and molecular weight than emulsions with PVA as protective colloid. Larger particle sizes than the reference were obtained for emulsions containing PVA combined with renewable materials. The emulsion with starch as protective colloid exhibited the largest particle size. 10 formulations passed the criteria for D2. The emulsions where PVA was fully or partially replaced with HEC or starch showed a water resistance similar to the reference (around D2). The addition of protein did not decrease the water and heat resistance compared to the reference. Addition of protein after polymerization increased the water resistance (D2) compared to addition during polymerization. Addition of cross-linking agents did not increase the water resistance further. Two formulations passed the criteria for D3. The emulsion in the first formulation had PVA as protective colloid and protein B was added during polymerization. The emulsion in the second formulation had HEC as protective colloid. To both of these emulsions, protein A was added after polymerization, as a filler, combined with Cross-linking agent B as cross-linking agent before hot pressing. The first formulation also showed a good heat resistance (passed the criteria for WATT 91).
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Brown, Nicole Robitaille. "Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/26446.
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This work addresses the distribution of N-methylolacrylamide (NMA) units in crosslinking poly(vinyl acetate) (PVAc) adhesives. In this case, distribution refers to the three potential locations of polymerized NMA units in a latex: the water-phase, the surface of polymer particles, and the core of the polymer particles. The objective is to identify the distribution of NMA in three latices and to determine whether NMA distribution correlates with durability related performance. NMA distribution was studied via a series of variable temperature solution NMR experiments, while the durability-related performance was studied via mode I fracture mechanics tests.
Studying the distribution of NMA required the use of isotopically labeled NMA. Both 15N-NMA and 13C, 15N-NMA were synthesized. Three NMA/vinyl acetate (VAc) latices were prepared. The NMA feed strategy was varied during each of the three emulsion copolymerizations. Latex characterization methods including differential scanning calorimetry (DSC), rheometry, particle size analysis, and scanning electron microscopy (SEM) were used to study the three latices.
The solution NMR method to identify NMA distribution was performed on untreated latices and on washed latices. Washing techniques included membrane dialysis and centrifugation. Results revealed that the three latices had different NMA distributions, and that the distributions were related to the expected differences in microstructure. Latex 3 had ~ 80% core-NMA, while Latex 2 had ~ 80% surface-NMA. Latex 1 had a high proportion of surface-NMA (~60%), but also had the highest proportion of water-phase NMA (~ 20%). This high proportion of water-phase NMA could be responsible for the unique morphology Latex 1 exhibited in SEM studies.
Mode I opening fracture mechanics studies were used to study adhesive performance. Specimens were analyzed after exposure to accelerated aging treatments. Latex 2 and Latex 3 exhibited very similar results, despite having very different NMA distributions. All three latices showed good durability related performance. In Latex 2 and Latex 3, the critical strain energy release rates (Gc) after accelerated aging treatments were statistically the same as the Gc of the control specimens. The most interesting finding was that the Latex 1 Gc values were significantly higher after accelerated aging. Latex 1 also had the highest proportion of water-phase NMA. Bondline images and SEM micrographs both indicated that the integrity of Latex 1 was least affected by the accelerated aging treatments.Ph. D.
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Collins, Stephen. "An investigation into the synthesis and characterisation of three materials based on poly (vinyl acetate)." Thesis, University of Sheffield, 2005. http://etheses.whiterose.ac.uk/3588/.
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An investigation into the synthesis of three types of material based on poly (vinyl acetate) was performed using three novel polymerisation techniques. The three techniques used were: i) the use of chain transfer to solvent; ii) the use of enzymes to catalyse the synthesis of block copolymers of vinyl acetate and c- caprolactone; iii) the synthesis of hyperbranched polymers of vinyl acetate and n- vinyl pyrrolidinone, monomers which both propagate through an unstabilised radical. The first technique has been widely used in order to synthesise polymers and oligomers with solvent derived endgroups. In this work polymers have been synthesised using isopropanol, 2-isopropoxy ethanol and 3-methyl-2-butanone as solvents. All of these have been shown to be active as chain transfer agents in previous studies. The second technique builds on previous work, performed in the field of enzymatic control of polymerisation reactions. Enzymes can be used to both synthesise monomers and catalyse the polymerisation of monomers. Hydroxy terminated poly (vinyl acetate) was used to control the polymerisation of 6- caprolactone, leading to the formation of block copolymers. The third technique involves the synthesis of hyperbranched poly (vinyl acetate) and poly (n-vinyl pyrrolidinone). This was achieved through the use of a polymerisable branching agent, also with the ability to act as a chain transfer agent. Through the use of this as a comonomer a hyperbranched polymer can be synthesised without the formation of a crosslinked gel.
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Dibbern, Deborah Nunes. "Estudo espectroscopico da fluoresceina em poli (alcool vinilico) e poli (acetato de vinila)." [s.n.], 1989. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249458.
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Orientadora : Tereza Dib Zabon AtvarsDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-07-14T09:41:19Z (GMT). No. of bitstreams: 1 Dibbern_DeborahNunes_M.pdf: 7761290 bytes, checksum: 34187bff4af4509684cffbdac636dfba (MD5) Previous issue date: 1989
Mestrado
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Krusic, Paul J. Jr, and James W. Hornbeck. "Preserving Decayed Wood Samples for Tree-Ring Measurement." Tree-Ring Society, 1989. http://hdl.handle.net/10150/261889.
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Wood disks in various states of decay can be inexpensively preserved and prepared for accurate crossdating and precise tree-ring measurement by impregnation with commercial wood glue. The technique does not affect the dimensions or physiological features of samples preserved in this manner. Dead red spruce trees on Mt. Washington, New Hampshire, remain available for dendrochronological examination as long as 29 years after their last year of stem growth.
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Savant, Deepa. "Multidimensional NMR studies of terpolymers poly(ethylene-co-vinyl acetate-co-carbon monoxide) and poly(ethylene-co-1-hexene-co-carbon monoxide)." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1153685162.
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Wittmar, Matthias. "Charge modified, comb-like graft polyesters for drug delivery and DNA vaccination synthesis and characterization of poly(vinyl dialkylaminoalkylcarbamate-co-vinyl acetate-co-vinyl alcohol)-graft-poly(D,L-lactide-co-glycolide)s /." [S.l.] : [s.n.], 2004. http://archiv.ub.uni-marburg.de/diss/z2004/0075/.
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Morel, Aurélie. "Synthèse et comportement auto-associatif des copolymères poly(acetate de vinyle)-b-poly(acide acrylique) et de leurs dérivés hydrolysés." Montpellier 2, 2004. http://www.theses.fr/2004MON20162.
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Guclu, Mehmet. "Light Stability And The Effect Of Temperature On Mechanical Properties Of Polypropylene / Poly(ethylene-vinyl-acetate) Blends." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608535/index.pdf.
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The variation in properties of Polypropylene (PP) / Ethylene Vinyl Acetate (EVA) blends upon EVA content, temperature, and light stability were followed by using tensile testing, impact testing, and differential scanning calorimetry (DSC).
Young&rsquos modulus of the blends decreased with increasing drawing temperature and EVA content. The stress at break values of the blends slightly increased with EVA whereas decreased with drawing temperature. The percent strain at break values of the blends were found to increase abruptly by increasing EVA content and drawing temperature. These changes in the mechanical properties are the indication of compatibility. The impact tests were performed only at 0°
C, 25°
C and the impact strength increased with the temperature and EVA content, but none of the samples were broken at higher testing temperatures. The effect of stabilizer was very obvious because stabilizer-free samples failed after 400 hours whereas, the samples with stabilizer resisted up to 750 hours. Elongation values of the samples decreased because of increasing brittleness by UV irradiation. We also observed chain stiffening effect by crosslinking in all samples upon UV irradiation. Thermal analysis of the blends of the drawn samples showed an increasing trend of crsytallinity with increasing drawing temperature. Increasing drawing temperature made polymer chains more flexible because of the increasing chain mobility. These flexible chains were then oriented in one direction during tensile testing and therefore uniaxial crystallization occurred. The morphology of impact and tensile tests samples were also analyzed by scanning electron microscope (SEM). The fibrillation of pure PP is higher than the fibrillation of the blends.
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Nuamthanom, Anuttra. "Multidimensional NMR studies of poly(ethylene-co-1-octene) copolymers and poly(ethylene-co-vinyl acetate-co-carbon monoxide) terpolymers." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1183614323.
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Schollin, Mårten. "Reaction Mechanism between Chitosan and Cerium(VI) Ammonium Nitrate for Production of a Greener Poly(Vinyl Acetate) Adhesive." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290297.
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Poly(vinyl acetate) (PVAc) has a major application as an indoor wood adhesive. Low water stability is however, one of the greatest drawbacks of PVAc. By grafting PVAc from a chitosan (CS) backbone (CS-graft- PVAc) water stability of adhesive is increased while good mechanical and adhesive properties are retained. Simultaneously the percentage of bio-based content is increased. This work investigates the proposed re- action mechanisms between chitosan and cerium(IV) ammonium nitrate (CAN) which is used as an initiator for the grafting reaction. Litera- ture studies showed one dominating reaction mechanism and some not as common. The reaction mechanisms and their shortcomings are pre- sented and discussed in the report.Poly(vinyl acetat)(PVAc) har ett stort användningsområde som ett trälim för möbler som ska användas inomhus. Den dåliga vatten stabiliteten är ett av de största problemen för användning av PVAc. Genom att ympa PVAc med chitosan(CS) (CS-graft-PVAc) kan vatten stabiliteten ökas samtidigt som en god limfunktion finns kvar och delen fossilbaserad monomer blir mindre och byts ut mot en biobaserad polymer. I detta arbete undersöks de föreslagna reaktionsmekanismerna mellan CS och cerium(IV) ammonium nitrat(CAN) som används som en katalysator för att grafta PVAc med CS. Litteraturstudier visade en dominerade reaktionsmekanism och några mindre förekommande. Reaktionsmekanis- merna och eventuella tillkortakommanden som finns gällande hur de fortlöper presenteras och diskuteras i detta arbete.
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Bergerbit, Cédric. "RAFT polymerization of ethylene for the synthesis of polar-apolar olefin block copolymers." Thesis, Lyon, 2019. https://n2t.net/ark:/47881/m6s181w9.
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La synthèse de copolymères à blocs, comprenant un bloc semi-cristallin de polyéthylène (PE) apolaire et un bloc polaire (poly(acétate de vinyle) (PAcV), poly(méthacrylate de méthyle) (PMAM), poly(oxide d’éthylène) (POE)) a été étudiée par polymérisation RAFT. L’étude préliminaire de l’homopolymérisation de l’éthylène en conditions relativement douces (T = 70 – 80 °C, P = 200 bar) a révélé que l’utilisation d’agents de transfert de chaîne (ATC) de type xanthates aromatiques conduit à une perte de fonctionnalité des extrémités de chaînes au cours de la polymérisation, conséquence directe de réactions de terminaison se produisant sur le radical intermédiaire. L’utilisation de dithiocarbamates aromatiques a permis de s’affranchir de ce mécanisme parasite et pour la première fois des chaînes de PE présentant une fonctionnalité de bout de chaîne proche de 100%. Des ATCs macromoléculaires polaires, obtenus avec les agents de transfert de chaînes identifiés au cours de l’étude préliminaire, ont ensuite été utilisés pour la synthèse de copolymères à blocs dans le carbonate de diméthyle (DMC), un solvant organique peu transférant. Le rôle clé de la thermodynamique du milieu de polymérisation (mélange DMC/éthylène supercritique à 200 bar) a alors été mis en évidence. En effet, les macro-ATCs sont insolubles dans un tel milieu, ce qui a conduit à la formation d’un mélange d’homopolymères. La diminution de la pression de polymérisation (P < 100 bar) a toutefois permis d’éviter ce phénomène et les copolymères PVAc-b-PE, PMMA-b-PE et PEO-b-PE attendus ont été obtenus. Des propriétés d’auto-assemblage ont été mises en évidence et des morphologies de type fibre ont été obtenues pour les copolymères PMMA-b-PE et PEO-b-PE synthétisés dans le DMC, permettant d’envisager un mécanisme de type auto-assemblage induit par la polymérisation (PISA). Le passage en milieu aqueux en utilisant le macro-ATC hydrosoluble PEO a permis l’observation de morphologies de type sphériques, vésicules ou encore ellipsoïdes selon le rapport molaire macro-ATC/amorceur utiliséThe synthesis of polar-apolar olefin block copolymers, combining a semi-crystalline polyethylene (PE) block and a polar block (poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO)) was investigated by RAFT polymerization. A preliminary study on ethylene homopolymerization revealed parasite cross-termination reactions happening at the intermediate radical, resulting in the loss of chain-end fidelity when using aromatic xanthates as chain transfer agents (CTA) under relative mild conditions (T = 70 – 80 °C, P = 200 bar). The extent of cross-termination was greatly reduced with aromatic dithiocarbamates, and for the first time, PE chains with a high livingness were obtained. These first results were used to equip polar macromolecular CTAs (PVAc, PMMA, PEO), with selected aromatic xanthates and dithiocarbamates, that were further used for block copolymerization with ethylene in a low-transferring organic solvent (dimethyl carbonate, DMC). A critical influence of the ethylene pressure was evidenced as block polymerization at 200 bar could not be achieved due to solubility issues in the resulting supercritical DMC/ethylene mixture. This was circumvented by performing the block copolymerization below the supercritical point of the mixture (P < 100 bar) and well-defined PVAc-b-PE, PMMA-b-PE and PEO-b-PE copolymers were eventually obtained. The block copolymers were found to feature self-assembly properties and worm-like morphologies were observed for PMMA-b-PE and PEO-b-PE synthesized in DMC, hinting at a plausible polymerization-induced self-assembly (PISA) mechanism. The successful switch from DMC to water for the synthesis of PEO-b-PE copolymers enabled the observation of various particle morphologies: spheres, vesicles and ellipsoidal particles, depending on the initial macro-CTA:initiator molar ratio
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Steinmacher, Fernanda Regina. "Síntese de nanopartículas de Poli(Acetato de Vinila) via polimerização em miniemulsão." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/94152.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2010Made available in DSpace on 2012-10-25T07:05:22Z (GMT). No. of bitstreams: 1 277394.pdf: 3434968 bytes, checksum: 7619623bf18a1a98673c0f49b310f62b (MD5)
Nanopartículas poliméricas, tais como nanocápsulas e nanoesfe-ras, apresentam grande potencial de aplicação em diversas áreas, como por exemplo, na liberação controlada de fármacos. Para tanto, diversas técnicas para obtenção de nanopartículas poliméricas podem ser aplica-das. Entretanto, o processo de polimerização em miniemulsão apresenta diversas vantagens, entre elas, a encapsulação de compostos hidrofóbi-cos em apenas uma etapa. Dessa forma, este trabalho propõe o estudo da polimerização em miniemulsão de acetato de vinila a 70oC aplicando-se diferentes agentes hidrofóbicos para retardar a degradação difusional, tais como Miglyol 812, óleo de castanha do Pará e hexadecano. Para aumentar a estabilidade da miniemulsão contra coalescência, diferentes surfatantes e procedimentos de adição destes foram avaliados. Os surfa-tantes aplicados apresentam valores distintos de balanço hidrofílico-lipofílico, HLB, sendo a lecitina, surfatante hidrofóbico e Tween 80, hidrofílico. A combinação destes surfatantes apresenta resultados satis-fatórios na obtenção de nanopartículas estáveis. Adicionalmente, foi estudado o efeito de diferentes iniciadores, tais como 2,2'-azo-bis-isobutironitrila e peróxido de potássio. Os resultados obtidos evidenciam que a cinética da reação depende fortemente do tipo de iniciador aplica-do. O uso de um estabilizador polimérico também foi avaliado, diversos tipos de poli(álcool vinílico) com diferentes graus de hidrólise e massa molar foram aplicados. A concentração ótima de estabilizador poliméri-co foi encontrada, sendo que acima desta, observou-se a formação de agregados de poli(álcool vinílico). Análises por microscopia eletrônica corroboram tais resultados. Com objetivo de aumentar a resistência me-cânica do polímero, monômero trifuncional foi aplicado. Análises de teor de gel comprovaram que o mesmo reticula o poli(acetato de vinila) satisfatoriamente. Finalmente, a encapsulação de progesterona em nano-partículas poliméricas foi realizada adicionando-se o hormônio na for-mulação da miniemulsão. Os resultados obtidos revelam que a polimeri-zação de acetato de vinila em miniemulsão se apresentou versátil na encapsulação de componentes hidrofóbicos em apenas uma etapa.
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Miriyala, Sethu M. "Effect of composite microstructure on electrical and mechanical properties of poly(vinyl acetate) composites with carbon black and clay." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1566.
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Karsten, Irene Frances. "The light stability of silk adhered to sheer silk and polyester backing fabrics with poly(vinyl acetate) copolymer adhesives." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0003/MQ34382.pdf.
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Moraes, Eduardo Aparecido de. "Estudo da influência do teor de acetato de vinila na morfologia e biodegradabilidade de blendas poli(ácido lático)/polietileno-co-acetato de vinila." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-20022018-081224/.
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O descarte inadequado de embalagens poliméricas tem gerado uma grande preocupação mundial. O alto consumo, atrelado ao curto tempo de uso dessas embalagens tem ocasionado um grande passivo ambiental. Diferentemente dos usuais polímeros empregados para este propósito, o poli(ácido lático) ou PLA é de fonte renovável e pode ser degradado no meio ambiente por ação de microrganismos como bactérias e fungos. Possui grande potencial para produzir sustentavelmente novos tipos de embalagens que sejam ambientalmente amigáveis. No entanto, para isso é preciso modificar algumas propriedades mecânicas para satisfazer sua aplicação, como a ductilidade e tenacidade. Uma boa alternativa para superar essas limitações é misturá-lo mecanicamente a um segundo polímero, produzindo blendas com propriedades melhoradas. Neste trabalho foram preparadas blendas poliméricas entre o PLA e o copolímero aleatório poli[(etileno)-co-(acetato de vinila)] (EVA), com teores de acetado de vinila (VA) de 65% (EVA65) e 90% (EVA90). As blendas foram preparadas por extrusão em dupla rosca co-rotacional interpenetrante. A morfologia e miscibilidade das blendas PLA/EVA foram estudadas por microscopia eletrônica de varredura (MEV), calorimetria exploratória diferencial (DSC) e análise termodinâmico-mecânica (DMTA). As propriedades mecânicas foram avaliadas por ensaios de tração, flexão em três pontos e resistência ao impacto Izod com entalhe. A influência do teor de VA na biodegradabilidade do PLA foi avaliada por perda de massa e por propriedades mecânicas em tração dos corpos de prova que foram submetidos ao teste de biodegradação em solo e ficaram enterrados por 0, 30, 90, 120 e 150 dias. As curvas DSC e os resultados de DMA mostram que as blendas PLA/EVA90 apresentam uma única temperatura de transição vítrea (Tg), sendo, portanto, miscíveis. Entretanto, as blendas PLA/EVA65 apresentam duas Tg e nítida separação de fases comprovando que são imiscíveis em todas as frações testadas. Mudanças como deslocamento da temperatura de cristalização do PLA são influenciados pelo aumento do teor de EVA nas blendas. Todas as blendas apresentam melhora nos resultados de flexibilidade e deformação na ruptura, destaque para amostra contendo 20% de EVA65 onde a deformação na ruptura foi 350% maior que o PLA puro. A resistência ao impacto da blenda contendo 30% de EVA65 representou um aumento na tenacidade aproximadamente 2400% em relação ao valor obtido pelo PLA puro. A taxa de biodegradação do PLA foi reduzida com o aumento do teor de EVA nas blendas. Blendas com EVA90 obtiveram maiores perdas de massa que as equivalentes contendo EVA65, revelando também a influência da miscibilidade na taxa de biodegradação do PLA. No entanto, ao final de 180 dias todos os corpos de provas sofreram variação negativa da massa, ou seja, foram biodegradados no solo.The inadequate disposal of packaging materials has led to a major worldwide concern. The high consumption, together with the short usage time of packaging materials, has created a serious environmental issue. Unlike conventional polymers, poly(lactic acid) or PLA comes from a renewable source and can be degraded by microorganisms (e.g., bacteria and fungi) in the environment. PLA has a great potential for the sustainable development of environmentally friendly materials intended for packaging applications. To do so, however, some of its mechanical properties (e.g., ductility and toughness) must be modified to meet the technical requirement for such applications. A feasible alternative of overcoming these limitations is mechanically blending PLA with a second polymer, producing blends featuring improved properties. In this study, we prepared polymer blends by mixing PLA and the random copolymer poly[(ethylene)-co-(vinyl acetate)] (EVA) comprising vinyl acetate (VA) contents of 65% (EVA65) and 90% (EVA90). The blends were prepared through interpenetrating co-rotating twin screw extrusion. PLA/EVA blend morphology and miscibility were investigated through scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic thermomechanical analysis (DMTA). Mechanical properties were determined through tensile, three-point bending, and notched Izod impact strength tests. The influence of VA content on PLA biodegradability was assessed by weight loss measurements as well as tensile tests in specimens submitted to biodegradation in soil, wherein they remained covered for 0, 30, 90, 120, and 150 days. DSC curves and DMTA data showed that the PLA/EVA90 blends presented a single glass transition temperature (Tg), indicating miscibility. On the other hand, the PLA/EVA65 blends presented two Tg as well as marked phase separation, corroborating the immiscibility of all tested fractions. Shifts on the crystallization temperature of PLA are influenced by increased EVA contents in the blends. All blends showed improved flexibility and deformation at break, particularly that comprising 20% EVA65, which presented an elongation at break 350% higher than pristine PLA. The impact strength of the blend comprising 30% EVA65 evidenced a ca. 2400% increase in toughness in comparison with pure PLA. PLA biodegradation rate was reduced by increased EVA contents. EVA90-containing blends displayed greater weight losses than their EVA65-containing counterparts, also revealing the influence of miscibility on PLA biodegradation rate. Nevertheless, after 180 days, all specimens presented weight loss, that is, were biodegraded in soil.
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Ramarad, Suganti. "Improving the properties of reclaimed waste tire rubber by blending with poly(ethylene-co-vinyl acetate) and electron beam irradiation." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/31278/.
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Non-degradable waste tire generation around the world is growing at an alarming rate. Diversifying the recycling route of these waste tires is essential to solve the problem. One way is to incorporate them into polymers and convert them into new products. However, incorporation of ground tire rubber into thermoplastics has been hampered due to lack of toughness and adhesion between phases. To address the issue, this study utilized reclaimed waste tire rubber (RTR) instead; and evaluated the properties of RTR and poly(ethylene-co-vinyl acetate) (EVA) blends. The properties of the RTR/EVA blends were further enhanced by compatibilization and electron beam irradiation. Processing, mechanical, thermal and dynamic mechanical properties of RTR were tremendously improved by blending with EVA. However, the interfacial adhesion was found to lack in the blends. Compatibilization by reactive, physical and combination strategies were explored utilizing (3-Aminopropyl)triethoxy silane (APS), liquid styrene butadiene rubber (LR) and maleated EVA (MAEVA), respectively. APS and MAEVA were found to be the most and least favourable compatibilizer, respectively. Apart from functioning as reactive compatibilizer, APS also reclaimed the RTR phase further. These lead to improved dispersion of smaller RTR phase in EVA matrix and enhanced the interfacial adhesion. Electron beam irradiation revealed the presence of radical stabilizing and scavenging additives within RTR which retards the crosslinking process in RTR and RTR/EVA blends. Though chain scissions were predominant; study showed the replacement of S-S and S-C bonds with stronger and stiffer C-C bonds ensures the retention of RTR and RTR/EVA blends properties upon irradiation. Compatibilization of RTR/EVA blend by APS (50RTR/5APS) also improved the crosslinking efficiency. However, the blend still suffered from oxidative degradation from irradiation in air. Radiation sensitizers, trimethylol propane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA) and N,N-1,3 Phenylene Bismaleimide (HVA2), were used to accelerate the irradiation induced crosslinking in RTR and 50RTR/5APS blends. Presence of radiation sensitizers leads to simultaneous improvement in toughness and tensile strength of RTR and 50RTR/5APS blends. Elastic capacity of RTR phase was restored and interfacial adhesion enhanced in the presence of radiation sensitizers.
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Zaccaron, Claudia Menegaz. "Blendas de hidroxipropilmetilcelulose/poli(1-vinilpirrolidona-co-acetato de vinila) ou alginato de sódio." Florianópolis, SC, 2005. http://repositorio.ufsc.br/handle/123456789/102335.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química.Made available in DSpace on 2013-07-16T00:40:47Z (GMT). No. of bitstreams: 1 221572.pdf: 1395947 bytes, checksum: 0446ee630fc4eed6f0dd0f8b6aa7f9e5 (MD5)
Neste trabalho estudou-se a miscibilidade, as propriedades mecânicas e a estabilidade térmica de filmes formados por hidroxipropilmetilcelulose (HPMC) e poli(1-vinilpirrolidona-co-acetato de vinila) - P(VP-co-VAc) ou alginato de sódio (SA). Análises (infravermelho, térmicas e morfológicas) sugeriram interações nas blendas HPMC/P(VP-co-VAc). Ensaios mecânicos revelaram o comportamento dúctil dos filmes com maiores quantidades de HPMC. Análises termogravimétricas indicaram que a blenda com 70% de HPMC é a mais estável termicamente. Os valores de energia de ativação, obtidos pelo método de Ozawa, sugeriram que a degradação do HPMC ocorreu por cisão das ligações fracas da cadeia. A degradação térmica dos filmes sugeriu a formação de álcoois e hidrocarbonetos insaturados. Em relação ao HPMC, CO2, CO, aldeídos, álcoois e éteres foram detectados como produtos voláteis. Já para o P(VP-co-VAc) foram detectados como voláteis ácido acético, amidas e NH3. Em relação ao sistema HPMC/SA, as análises sugeriram pouca interação entre os polímeros. Os valores de tensão de ruptura e alongamento são menores nas blendas que nos polímeros puros. A adição de alginato diminuiu a estabilidade térmica em relação ao HPMC puro. Os valores de energia de ativação foram maiores nas blendas. A degradação térmica do SA sugeriu a formação hidrocarbonetos insaturados e, como voláteis, CO2, CO e álcoois.
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Salajkova, Michaela. "Wood Nanocellulose Materials and Effects from Surface Modification of Nanoparticles." Doctoral thesis, KTH, Biokompositer, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-131469.
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Nanocellulose is an interesting natural material thatis gaining interest in the field of materials science, particularly nanocomposites. Depending on the disintegration route, nanocellulose can be isolated either in the form of long and flexible fibres (nanofibrillated cellulose, NFC), or stiff, rod-like crystals (cellulose nanocrystals, CNC). Nanocellulose can be utilized in nanocomposites either as a reinforcement element or as a network matrix due to its ability to form a strong network. In this thesis, nanocellulose based materials are prepared by evaporation of a liquid medium. The key step in this processing route is a good dispersion of the nanoparticles in the selected matrix. Therefore the importance of surface modification in order to ensure favourable nanocellulose dispersion is clarified in avariety of materials systems. In Paper I, poly(methyl methacrylate) (PMMA) based fibres prepared by electrospinning were reinforced with nanofibrillated cellulose. Native NFC appeared to show a good compatibility with PMMA matrix in the electrospinning solution and resulting fibres. Furthermore, a new method for mechanical testing of mats with random fibre orientation as well as aligned fibres was developed. In Paper II, commingled nanopaper structures with carbon nanotubes (CNTs) were prepared. Several surfactants were used to disperse hydrophobic CNTs in water. A nonylphenol phosphate ester (NPPE) was found to work well for both dispersing CNTs in water and providing compatibility with NFC through electrostatic repulsion between the phosphate ester groups of the surfactant and the carboxylate groups of NFC. In Paper III, a new water based route for functionalization of cellulose nanocrystals was developed. In this approach, inspired by organo-modified layered silicates, quaternary ammonium salts were adsorbed. It was demonstrated that different functionalities (alkyl, phenyl, glycidylor diallyl) can be introduced onto the cellulose and the dispersibility in organic solvents was studied. Subsequently, in Paper IV, nanocomposites with poly(vinyl acetate) (PVAc)were prepared. The effect of modification on the degree of dispersion of the CNC within the matrix was studied as well as the strong effects on the properties of the resulting nanocomposites. In Paper V, taking advantage of the entangled NFC network and the possibility to tailor the pore size and surface chemistry, lubricant-infused slippery films and coatings based on NFC were prepared for the first time.QC 20131016
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Müller, Cláudio Luís. "Modificação química do EVA com óxido de limoneno para utilização como agente interfacial na adesão de filmes de nylon com poli(etileno-co-acetato de vinila)." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2006. http://hdl.handle.net/10183/7877.
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Neste trabalho foi realizada a modificação química de poli(etileno-coacetato de vinila) (EVA com 8 mol% de acetato de vinila), pela introdução de óxido de limoneno, através de reação via radical livre, para posterior utilização como agente promotor de adesão em filmes multicamadas em sistema EVA-8/poliamida. As reações foram realizadas em câmara de mistura tipo Haake, durante 15 minutos, a 160ºC e com velocidade dos rotores de 40 rpm. O iniciador de radicais livres foi o peróxido de benzoíla. Foi verificado que o processamento do EVA não acarretou processos de degradação ou reticulação do polímero. Filmes de EVA modificado foram prensados durante 3 minutos, sob pressão de 200 Kgf a 150 ºC, contra substrato de poliamida. Os filmes foram submetidos ao ensaio de delaminação para verificar a adesividade. Diferentes teores de óxido de limoneno e de peróxido de benzoíla foram utilizados para avaliação do melhor teor de agente modificante. Os resultados obtidos são similares aos obtidos com EVA-8 mol% modificado por metacrilato de glicidila, agente largamente utilizado para produção de adesivos industriais. O óxido de limoneno é baseado numa matéria-prima natural e abundante, apresentando potencial como adesivo para polímeros que apresentem grupamentos co5 reativos à função orgânica “óxido”, podendo sofrer reação, como no caso das aminas (nas poliamidas) e das hidroxilas (nos polímeros com grupos “-OH” livres na cadeia principal).Poly(ethylene-co-vinyl acetate) (EVA-8 with 8 mol% of vinyl acetate) was modified by reaction with limonene oxide, for subsequent use as agent adhesion promoter in multi-layers EVA-8/polyamide films. The reactions were accomplished in a blender type Haake, by 15 minutes, at 160ºC and rotor’s speed of 40 rpm. It was verified that EVA-8 processing did not produced degradation or crosslinks reactions in the polymer structure. Films of modified EVA were pressed for 3 minutes, under 200 kgf of pressure at 150 ºC, against polyamide layers. The films were submitted to the delamination test to verify the adhesiveness. Different limonene oxide and benzoil peroxide tenors were used for the modification of EVA and evaluation of the best relation between the components. The results were similar to the obtained with EVA-8 modified by glycidyl methacrylate, a broadly agent used for production of industrial stickers. The limonene oxide is based on a natural and abundant raw material, presenting an adhesive potential for reacting systems, where polymers that present co reactive groups to the oxide organic function can react, as in the case of the amines (in the polyamides) and of the hydroxyl (in the polymeric ones with groups "-OH" in the main chain).
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Delattre, Émilie. "Fonctionnalisation de polymères et applications en cosmétique." Phd thesis, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00918532.
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L'alcool polyvinylique a été fonctionnalisé avec des aldéhydes et des acides boroniques dans le but d'obtenir des polymères pouvant apporter de la brillance tout en étant solubles dans les formulations de rouges à lèvres ou de vernis à ongles. De bons taux de fonctionnalisation ont été obtenus permettant d'avoir une bibliothèque de poly(vinyl acétals) et de poly(vinyl esters boroniques) d'une cinquantaine de polymères. Une multi-fonctionnalisation du PVA a été effectuée pour obtenir des polymères alliant ces deux propriétés. Cinq poly(vinyl acétals) ont ainsi permis d'apporter une forte brillance à des rouges à lèvres. La E-poly-L-lysine a également été fonctionnalisée avec diverses cétones afin d'obtenir de nouvelles poly-4-imidazolidinones. Ces polymères sont prometteurs pour des applications dans des produits cosmétiques tels que des soins. Ils ont également été utilisés en catalyse organique asymétrique.
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Basso, Glaucia Grazielli [UNESP]. "Síntese e caracterização de partículas esféricas de poli(álcool vinílico) e poli(acetato vinílico) para utilização em embolização." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/87503.
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Financiadora de Estudos e Projetos (FINEP)
Partículas poliméricas com tamanho e morfologia controlados e propriedades físico-químicas adequadas são amplamente utilizadas em aplicações médicas, como na embolização, uma técnica cirúrgica utilizada para tratar malformações arteriovenosas (MAVs), conter hemorragias, tratar localmente tumores hipervascularizados (THVs) e outras doenças vasculares. Este procedimento é realizado com materiais de diferentes formas e composições, sendo as partículas de poli(álcool vinílico) (PVA) freqüentemente utilizadas por apresentarem um alto grau de desempenho. Elas estão disponíveis no mercado nas morfologias esférica e não-esférica, sendo que as esféricas apresentam uma maior eficácia no tratamento. O presente trabalho objetivou desenvolver e aprimorar partículas esféricas de PVA e poli(acetato vinílico) (PVAc) para serem utilizadas em embolização. Suas sínteses foram realizadas em duas etapas: a polimerização em suspensão do monômero acetato vinílico (VAc) em PVAc e a saponificação do polímero PVAc em PVA, com variações na velocidade de agitação e na concentração da solução de hidróxido de sódio (NaOH), na etapa da saponificação. As partículas foram caracterizadas por microscopia eletrônica de varredura (MEV), difração de raios-X (DRX), calorimetria diferencial de varredura (DSC) e ressonância magnética nuclear de 13 C - cross polarization / magic angle spinning (13 C RMN CP/MAS). Foram analisadas a distribuição de tamanhos, a dimensão fractal, a determinação da biocarga, que determinou os parâmetros de esterilização por radiação gama, e a citotoxicidade, pelo teste de “Reatividade Biológica in vitro”. Os resultados indicaram que a morfologia esférica foi obtida durante a primeira etapa da síntese e que essa morfologia não foi afetada pelo segundo processo. A velocidade de agitação e a concentração de NaOH influenciaram...
Polymeric particles with controlled size and morphology and appropriated physicochemical properties are widely used in medical applications, such as embolization, a surgical technique used to treat arteriovenous malformations (AVMs), stop bleedings, treat locally hypervascular tumors (HVTs) and other vascular diseases. This procedure is performed with materials of different shapes and compositions, and the poly(vinyl alcohol) (PVA) particles are often used for presenting a high degree of performance. They are commercially available in spherical and non-spherical morphologies, and the spherical particles have a greater efficacy in the treatment. This study aimed to develop and improve spherical PVA and poly(vinyl acetate) (PVAc) particles for use in embolization. Their syntheses were performed in two stages: the suspension polymerization of vinyl acetate (VAc) monomer in PVAc and the saponification of PVAc polymer in PVA, with variations in the stirring speed and the concentration of sodium hydroxide (NaOH) solution, at the saponification step. The particles were characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and 13 C nuclear magnetic resonance - cross polarization / magic angle spinning (13 C NMR CP/MAS). We analyzed the size distribution, the fractal dimension, the determining of the bioburden, which determined the parameters of sterilization by gamma irradiation, and the cytotoxicity, by the “Biological Reactivity in vitro”. The results indicated that the spherical morphology was obtained during the first stage of the synthesis and that this morphology was not affected by the second process. The stirring speed and the NaOH concentration influenced the size of the particles. The commercial particles have a fractal dimension greater than the synthesized particles... (Complete abstract click electronic access below)
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Yamaki, Sahori Barbosa. "Espectroscopia de fluorescencia de sondas e marcadores aplicada ao estudo de processos de relaxações em polietileno, poli(acetato de vinila) e copolimeros de etileno-co-acetato de vinila." [s.n.], 2002. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249479.
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Orientador : Teresa Dib Zambon AtvarsTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado
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Severgnini, Vanderlei Luis Sitta. "Estudo da degradação térmica do poli(cloreto de viníla-co-acetato de viníla-co-2-hidróxipropil acrilato) e seus homopolímeros." Florianópolis, SC, 2002. http://repositorio.ufsc.br/xmlui/handle/123456789/82844.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química.Made available in DSpace on 2012-10-19T18:49:26Z (GMT). No. of bitstreams: 0Bitstream added on 2014-09-26T02:28:37Z : No. of bitstreams: 1 193859.pdf: 11871460 bytes, checksum: 12e20eff43b4dba1612a4c9166a796ba (MD5)
Neste trabalho estudou-se a degradação térmica do poli(VC-co-VA-co-2-HPA) e seus homopolímeros em atmosfera de N2. Foram utilizadas técnicas de análise térmica e espectrofotometria para caracterização e análise do processo. A degradação do copolímero e seus homopolímeros ocorrem em duas etapas. Na primeira etapa observa-se dois mecanismos distintos para o PVC, o primeiro refere-se à eliminação de HCl e benzeno e o segundo a eliminação de HCl e formação de ligações cruzadas entre as cadeias enquanto que no PVA ocorre simplesmente eliminação de ácido acético. A segunda etapa ocorre com a eliminação de metano e compostos com ligações C-H com prováveis complexidades no mecanismo para ambos os casos. A aplicação dos métodos de Freeman-Carroll e Ozawa aos dados termogravimétricos do copolímero não indica mudanças de mecanismo durante a primeira etapa Ea= 174,9 kJ/mol e n= 1,46 e Ea= 109,6 kJ/mol, respectivos aos métodos. Porém na etapa em questão observa-se primeiramente a eliminação de propan-2-ol oque parece provocar uma mudança de mecanismo, possivelmente pela presença de carbonos radicalares na cadeia oque ocasionaria uma desestabilização de ligações dos grupos presos à mesma provocando a eliminação de HCl, acido acético, benzeno e CO2 simultaneamente. Já para a segunda etapa (com produtos semelhantes à degradação do PVC e PVA) os parâmetros cinéticos obtidos pelos dois métodos são respectivamente: Ea=226,6 kJ/mol, n=1,34 e Ea= 224,33 kJ/mol.
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Basso, Glaucia Grazielli. "Síntese e caracterização de partículas esféricas de poli(álcool vinílico) e poli(acetato vinílico) para utilização em embolização /." São José do Rio Preto : [s.n.], 2011. http://hdl.handle.net/11449/87503.
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Resumo: Partículas poliméricas com tamanho e morfologia controlados e propriedades físico-químicas adequadas são amplamente utilizadas em aplicações médicas, como na embolização, uma técnica cirúrgica utilizada para tratar malformações arteriovenosas (MAVs), conter hemorragias, tratar localmente tumores hipervascularizados (THVs) e outras doenças vasculares. Este procedimento é realizado com materiais de diferentes formas e composições, sendo as partículas de poli(álcool vinílico) (PVA) freqüentemente utilizadas por apresentarem um alto grau de desempenho. Elas estão disponíveis no mercado nas morfologias esférica e não-esférica, sendo que as esféricas apresentam uma maior eficácia no tratamento. O presente trabalho objetivou desenvolver e aprimorar partículas esféricas de PVA e poli(acetato vinílico) (PVAc) para serem utilizadas em embolização. Suas sínteses foram realizadas em duas etapas: a polimerização em suspensão do monômero acetato vinílico (VAc) em PVAc e a saponificação do polímero PVAc em PVA, com variações na velocidade de agitação e na concentração da solução de hidróxido de sódio (NaOH), na etapa da saponificação. As partículas foram caracterizadas por microscopia eletrônica de varredura (MEV), difração de raios-X (DRX), calorimetria diferencial de varredura (DSC) e ressonância magnética nuclear de 13 C - cross polarization / magic angle spinning (13 C RMN CP/MAS). Foram analisadas a distribuição de tamanhos, a dimensão fractal, a determinação da biocarga, que determinou os parâmetros de esterilização por radiação gama, e a citotoxicidade, pelo teste de "Reatividade Biológica in vitro". Os resultados indicaram que a morfologia esférica foi obtida durante a primeira etapa da síntese e que essa morfologia não foi afetada pelo segundo processo. A velocidade de agitação e a concentração de NaOH influenciaram... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: Polymeric particles with controlled size and morphology and appropriated physicochemical properties are widely used in medical applications, such as embolization, a surgical technique used to treat arteriovenous malformations (AVMs), stop bleedings, treat locally hypervascular tumors (HVTs) and other vascular diseases. This procedure is performed with materials of different shapes and compositions, and the poly(vinyl alcohol) (PVA) particles are often used for presenting a high degree of performance. They are commercially available in spherical and non-spherical morphologies, and the spherical particles have a greater efficacy in the treatment. This study aimed to develop and improve spherical PVA and poly(vinyl acetate) (PVAc) particles for use in embolization. Their syntheses were performed in two stages: the suspension polymerization of vinyl acetate (VAc) monomer in PVAc and the saponification of PVAc polymer in PVA, with variations in the stirring speed and the concentration of sodium hydroxide (NaOH) solution, at the saponification step. The particles were characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and 13 C nuclear magnetic resonance - cross polarization / magic angle spinning (13 C NMR CP/MAS). We analyzed the size distribution, the fractal dimension, the determining of the bioburden, which determined the parameters of sterilization by gamma irradiation, and the cytotoxicity, by the "Biological Reactivity in vitro". The results indicated that the spherical morphology was obtained during the first stage of the synthesis and that this morphology was not affected by the second process. The stirring speed and the NaOH concentration influenced the size of the particles. The commercial particles have a fractal dimension greater than the synthesized particles... (Complete abstract click electronic access below)
Orientador: José Geraldo Nery
Coorientador: Ana Paula Marques de Lima Oliveira
Banca: Rosa Sayoko Kawasaki Oyama
Banca: Moacir Fernandes de Godoy
Mestre
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Bergamaski, Franciele de Oliveira Freitas. "Preparação e caracterização das propriedades luminescentes de blendas de poli(3-ácidotiofenoacético) com acetato de celulose ou poli(vinil álcool)." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/6173.
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Previous issue date: 2010-11-19Universidade Federal de Minas Gerais
We have studied the optical properties of Poly(3-Thiopheneacetic Acid) (PTAA) by absorption, emission, and infrared measurements. We have observed, on the contrary of what broadly reported in the literature, that the intensity of the PTAA luminescence increased with time exposition of the Laser beam. The results have been shown that luminescence was highly dependent of the power of Laser beam excitation and of the polymeric (blends) film thickness. To evaluate the chemical changes in the course of luminescence increasing, absorption measurements in the infrared range were done. A decrease in the band of 1560 cm-1 was observed after Laser beam irradiation, what could be related with a decrease in the number of C=C bonds, and it is a possible explanation for the luminescence intensification. The PTAA photoluminescence was studied under high vacuum showing that the increase of luminescence was not dependent of oxygen presence in the polymeric film. Besides, we have done photoluminescence measurements at temperature of 10 K and compared with that at room temperature, 298 K. In the irradiation of the films at 10 K it was observed a suppressing effect that could be related to conformational changes in the polymer structure. Finally, we have measured the time resolved photoluminescence (TRPL) of PTAA and AC/PTAA blends in picoseconds in two temperatures regime. It was investigated the TRPL transients for different samples of PTAA in several solvents and for blends with cellulose acetate (AC) or poly(vinyl alcohol) (PVA). In all samples (the pure polymer and in the blends) the PL transients have presented behavior mono- and biexponentials. However, the mono-exponential model, in most cases, was not sufficient to describe adequately all PL decays. So, it was used a function in the form of two exponentials sum.
Inicialmente foram estudadas as propriedades ópticas de filmes de Poli(3-ácidotiofenoacético) (PTAA) por medidas de absorção, emissão e infravermelho. Verificou-se, ao contrário do extensivamente descrito na literatura, que a intensidade da luminescência do PTAA aumentava com o tempo de exposição ao Laser. Os resultados mostraram que a luminescência é fortemente dependente da intensidade da luz de excitação e da espessura dos filmes. Para avaliar as mudanças químicas geradas durante o aumento da luminescência, realizaram-se estudos de absorção na região do infravermelho. Observou-se uma diminuição na banda em 1560 cm-1 depois da irradiação com Laser, o que pode estar relacionado com um decréscimo no número de ligações C=C e é uma possível explicação para a intensificação da luminescência. A fotoluminescência do PTAA foi estudada em alto vácuo e os resultados mostraram que o aumento da luminescência é independente da presença de oxigênio. Além disso, com a realização de medidas de fotoluminescência à 10 K, observou-se um efeito supressivo na irradiação dos filmes que pode estar relacionado com a mudança na conformação do polímero. Finalmente, realizaram-se medidas de fotoluminescência resolvida no tempo, PLRT. Foram estudados filmes de PTAA e de blendas AC/PTAA e PVA/PTAA utilizando-se PLRT em picosegundos a temperatura ambiente e a baixa temperatura. Investigaram-se os transientes de PLRT para diferentes amostras de PTAA de diferentes solventes e de blendas com Acetato de celulose (AC) ou Poli(vinil álcool) (PVA). No polímero puro e nas blendas os transientes de PL apresentaram comportamento mono e biexponenciais, entretanto o modelo monoexponencial na maioria dos casos não foi suficiente para descrever adequadamente todos os decaimentos de PL. Utilizou-se então, uma função na forma de uma soma de duas exponenciais.
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Falcone, Daniele Maria Bruno. "Modificação do Poli(hidroxibutirato) PHB com nucleantes e com o copolímero (etileno-co-acetato de vinila) - EVA." Universidade Federal de São Carlos, 2008. https://repositorio.ufscar.br/handle/ufscar/655.
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Previous issue date: 2008-03-19Financiadora de Estudos e Projetos
In this work, we sought to modify PHB, processing it in the melted state, and to evaluate the effect of the modifications on its mechanical properties and biodegradation characteristics. The following systems were therefore studied: a PHB/EVA blend, in a 90/10 ratio, with an ethylene-co-vinyl acetate copolymer containing 28% of VA; a PHB and PHB/EVA blend with 1% of Boron Nitride (BN) nucleant; a PHB and PHB/EVA blend with 0,35% of HPN nucleant ( Hyperform Nucleant ); and a PHB/EVA blend with 5% of Elvaloy PTW, which was used as a compatibilizer. These systems were characterized by thermal, mechanical, morphological and biodegradation analyses using the following techniques: Melt Flow Index (MFI), Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), Dynamic Mechanical Thermal Analysis (DMTA), Size Exclusion Chromatography (SEC), Tensile Mechanical and Izod Impact (notched) Tests, Wide-Angle X-ray Diffraction (WAXD), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The biodegradability test involved burying the samples in a suitable compost for 60, 120 and 180 days. The DCS analysis indicated that Boron Nitride was an effective nucleating agent for the PHB. However, the HPN did not act as a nucleant on this polymer, but instead, induced degradation of the PHB upon heating, as indicated by MFI, DSC and TG. Moreover, the addition of BN or even EVA did not improve the mechanical properties of PHB, and Elvaloy PTW did not act as a compatibilizing agent for the PHB/EVA blend. The HPN was found to interact antagonically with the PHB, which displayed extremely low impact strength values and widely dispersed results. The SEM and AFM analyses revealed poor distribution and inadequate dispersion of EVA in the PHB matrix. In addition, the AFM technique indicated that the PHB topography displayed the presence of pores, which undoubtedly, combined with the other factors, hindered its modification. Biodegradation was found to be strongly composition-dependent, since the addition of 10% of EVA to the PHB significantly accelerated the degradation of the PHB in this blend. In other words, the PHB probably exhibited disordered chain packing in the proximities of the EVA, facilitating the process of biodegradation by microorganisms. Hence, this study demonstrated the difficulty of modifying PHB, since it involves a variety of factors, as well as the possibility of developing PHB-based materials that biodegrade more or less rapidly according to the needs of a specific application.
Neste trabalho, buscou-se modificar o PHB utilizando-se do processamento no estado fundido, e avaliar o efeito das modificações sobre as propriedades mecânicas e características de biodegradação. Assim, os seguintes sistemas foram estudados: blenda PHB/EVA, na razão 90/10, com um copolímero etileno-co-acetato de vinila contento 28% de VA; PHB e blenda PHB/EVA com 1% do agente nucleante Nitreto de Boro (BN); PHB e blenda PHB/EVA com 0,35% do agente nucleante HPN ( Hyperform Nucleant ); blenda PHB/EVA com 5% de Elvaloy PTW, o qual foi utilizado como compatibilizante. Com estes sistemas foram efetuadas caracterizações térmicas, mecânicas, morfológicas e de biodegradação utilizando-se várias técnicas: medidas de Índice de Fluidez (MFI), Calorimetria Exploratória Diferencial (DSC), Termogravimetria (TG), Análise Térmica Dinâmico-Mecânica (DMTA), Cromatografia de Exclusão por Tamanho (SEC), Ensaios Mecânicos de Tração e de Impacto Izod com entalhe, Difração de Raio-X de Alto Ângulo (WAXS), Microscopia Eletrônica de Varredura (MEV), Microscopia de Força Atômica (AFM). O ensaio de biodegradabilidade foi efetuado enterrando-se as amostras em um composto apropriado por 60, 120 e 180 dias. Como evidenciado por DSC, o Nitreto de Boro mostrou-se como um agente nucleante efetivo para o PHB. Já o HPN não atuou como tal para este polímero, e conforme comprovado por MFI, DSC e TG, induziu à degradação do PHB mediante aquecimento. Em relação às características mecânicas, a adição de BN ou mesmo EVA não propriciou melhora nas propriedades mecânicas do PHB, e o Elvaloy PTW não atuou como agente compatibilizante para a blenda PHB/EVA. O HPN mostrou interação antagônica com o PHB, que exibiu valores de Resistência ao Impacto extremamente baixos e com grande dispersão dos resultados. Conforme demonstrado por MEV e AFM, não houve boa distribuição e adequada dispersão do EVA na matriz de PHB. Além disto, a técnica de AFM evidenciou que o PHB exibiu uma topografia com a presença de alguns poros, o que certamente em conjunto aos demais fatores dificultou a sua modificação. Em relação à biodegradação, esta mostrou-se fortemente dependente da composição, visto que a adição de EVA ao PHB, no teor de 10%, induziu a um aumento significativo na velocidade de biodegradação do PHB nesta blenda. Ou seja, provavelmente o PHB exibiu um empacotamento de cadeia desordenado nas proximidades do EVA, facilitando o processo de biodegradação por microrganismos. Assim, este estudo mostrou a dificuldade na modificação do PHB, visto que vários fatores estão envolvidos, e além disto, a possibilidade de desenvolver materiais baseados em PHB que se biodegradem mais ou menos rapidamente de acordo com a necessidade de uma aplicação específica.
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Alvares, Giulia Maria Rodrigues. "Desenvolvimento e caracterização de fibras de poli(acrilonitrila-co-acetato de vinila) obtidas por meio de eletrofiação." reponame:Repositório Institucional da UFABC, 2015.
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Orientador: Prof. Dr. Everaldo Carlos Venancio.Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2015.
O processo de eletrofiação é conhecido por ser uma técnica eficiente para a fabricação de micro e nanofibras poliméricas. As fibras provenientes do processo de eletrofiação podem ser aplicadas em diversos setores tecnológicos, como engenharia de tecidos, sensores, liberação controlada de fármacos, catálise, compósitos entre outras. Este trabalho consiste na obtenção e caracterização de micro e nanofibras a partir de uma solução polimérica de um copolímero de Poli(acrilonitrila) (PAN), o Poli(acrilonitrila-co-acetato de vinila) (PANVA). A amostra de PANVA é composta de 94 % em massa do monômero acrilonitrila e 6% em massa do monômero acetato de vinila. Foi estudada a influência dos parâmetros de processamento como distância de trabalho entre a agulha e o coletor, concentração do polímero, vazão e potencial elétrico aplicado. Observou-se com esse estudo que ao diminuir a distância de trabalho, mantendo-se uma tensão constante de 20 kV, houve um aumento na quantidade de fibras de PANVA depositadas no coletor. Porém, quando a distância de trabalho foi mantida constante em 10 cm e variou-se a tensão aplicada (10-20 kV), ocorreu um aumento na quantidade de fibras formadas. Para valores de tensão inferiores a 20 kV foi observada a presença de uma grande quantidade de estruturas globulares de PANVA. O estudo do efeito da viscosidade da solução de PANVA foi realizado mantendo-se a tensão aplicada constante e igual a 20 kV e uma distância de trabalho constante e igual a 10 cm. Para baixos valores de viscosidade 7,34 mPa.s(2 % m/v) não foi observada a formação de fibras. Para valores de viscosidade entre 14,50 e 49,65 mPa.s (4 e 6 % m/v respectivamente) foi observada a formação de nanofibras. Para viscosidades acima de 111,30 mPa.s (8 % m/v) o processo de eletrofiação somente ocorre quando os valores de tensão aplicada forem maiores ou iguais a 25 kV. O diâmetro médio das fibras obtidas variou de 99,4 (±22,6) a 123,5 (±19,5) nm. Portanto, realizando-se um controle adequado da tensão aplicada, da distância de trabalho e da viscosidade da solução polimérica foi possível obter micro e nanofibras de PANVA.
The electrospinning process is known as being an efficient technique to produce polymer micro- and nano-fibers. The fibers obtained from electrospinning process are can be used in different technological áreas, as for example in tissue engineering, sensors, drug delivery, catalisis, composite materialas. In this work it was studied the production and characterization of micro- and nano-fibers by using a polyacrylonitrile (PAN) copolymer polymeric solution, poly(acrylonitrile-co-vinyl acetate) (PANVA). The PANVA used in this work is a copolymer containing 6 wt.% of polyvinylacetate. It was studied the electrospinning processing parameters effect, such as working distance from the needle and colector, polymer concentration and applied DC electric potential. When the working distance was increased from 10 to 20 cm (at constant applied electric potential, 20 kV) it was observed a decrease in the amount of fibers deposited on the colector. However, when the working distance was kept constant and the applied electric potential was increased from 10 to 20 kV, it was observed a increase in the amount of fibers deposited on the colector as well as a decrease in the amount of beads of PANVA in the sample. The study of the effect of the polymer solution viscosity was carried out at a constant applied eletric potential (20 kV) and working distance (10 cm). For low viscosity values, i.e. 7.34 mPa.s (2 wt.%) it was not observed the formation of fiber, i.e. only beads was formed. For viscosity values of 14.50 and 49.65 mPa.s (4 and 6 wt.%, respectively) it was observed the formation of nano-fibers. For viscosity values higher than 111.30 mPa.s (8 wt.%), the electrospinning process only occur for applied electric potential equal to (or higher than) 25 kV. The fibers mean diameter changed from 99.4 (±22.6) to 123.5 (±19.5) nm. Thereforte, by using the optimized electrospinning process conditions, i.e. applied DC electric potencial, working distance and PANVA solution viscosity it was possible to control the diameter of the PANVA fibers from microfibers to nanofibers.
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Cavalli, Letícia Riboldi. "Mistura polimérica de poli(ácido lático)/poli(etileno-co-acetato de vinila) com incorporação de polietilenoglicol e quitosana como agentes modificadores de propriedades." reponame:Repositório Institucional da UCS, 2015. https://repositorio.ucs.br/handle/11338/1180.
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O poli(ácido lático)(PLA) tem sido utilizado no campo das embalagens, contudo, visando melhorar as características processuais e a tenacidade deste polímero, misturas poliméricas de PLA com poli(etileno-co-acetato de vinila)(EVA), polietilenoglicol (PEG) e quitosana(QUI) foram desenvolvidas por processo de extrusão, injeção e por moldagem por compressão foram produzidos filmes, utilizados no estudo. As propriedades de mistura com PLA foram investigadas pelas propriedades morfológicas, térmicas e mecânicas e os filmes desenvolvidos foram aplicados a produtos alimentícios como pão de forma, sendo avaliadas as propriedades antimicrobianas, umidade, atividade de água, textura e cor, e em maçã minimamente processada, sendo avaliadas as propriedades antimicrobianas, atividade antioxidante, polifenóis, textura, pH, sólidos solúveis e cor. As misturas de PLA/EVA/PEG e PLA/EVA/PEG/QUI, quando comparadas ao PLA, mostraram miscibilidade parcial, diminuição na temperatura de transição vítrea (Tg), redução da resistência à flexão e do módulo de elasticidade, evidenciando a diminuição de rigidez molecular e aumento na capacidade de deformação do polímero, propriedades estas de interesse para processar PLA e para a produção de embalagens. A exposição do produto alimentício pão de forma às misturas poliméricas com quitosana promoveu efeito inibitório do crescimento de bolores e leveduras, em torno de 50% (com a mistura polimérica contendo 5 pcr de quitosana, quando comparado a mistura sem quitosana), sem afetar os teores de umidade, atividade de água e textura, do produto, e contribui para a manutenção da cor durante o armazenamento. A exposição de maçãs minimamente processadas às misturas poliméricas com quitosana promoveu uma diminuição no crescimento de bolores e leveduras, em torno de 54% (com a mistura polimérica contendo 5 pcr de quitosana, quando comparado a mistura sem quitosana), sem afetar a os teores de sólidos solúveis, pH, textura e perda de peso. A adição de quitosana também evitou o escurecimento enzimático, aumentou os teores de polifenóis totais, em torno de 20% e triplicou a atividade antioxidante, após 10 dias de armazenamento, nas frutas que ficaram em contato com a mistura polimérica PLA/EVA/PEG/5,0QUI. Conclui-se, por fim, que a mistura de EVA, PEG e quitosana ao PLA possibilitou a modificação das propriedades de rigidez e processabilidade e que o emprego da quitosana comprovou ter eficiente ação antimicrobiana e antioxidante, permitindo atender, com os resultados apresentados, o objetivo proposto no estudo.Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-06-21T16:17:24Z No. of bitstreams: 1 Dissertacao Leticia Riboldi Cavalli.pdf: 4432263 bytes, checksum: fe47f3b1dcc48301024685464eb37fc3 (MD5)
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Poly (lactic acid) (PLA) has been employed in the packaging area, however, in order to improve its processing features and tenacity. Polymer blends of PLA with poly(ethylene-co-vinyl-acetate) (EVA), polyethylene glycol (PEG) and chitosan (QUI) were developed by extrusion and injection process while films were obtained by compression on this work. Morphological, thermal and mechanical properties of PLA blends have been investigated and films have been developed and put in contact with a nutritional product, the loaf bread, analyzing then its antimicrobial properties, humidity, water activity, texture and color and on the minimally processed apple, analyzing then its antimicrobial properties, antioxidant activity, polyphenols, texture, pH, soluble solids as well as color. The PLA/EVA/PEG and PLA/EVA/PEG/QUI blends when compared to PLA, showed partial miscibility, reduction of glass transition temperature (Tg), lower flexural strength and of the modulus of elasticity, evidencing then a reduction in molecular hardness and an increase in the deformation ability of the polymer, properties of interest to process PLA and for packaging manufacture. The exposure to a nutritional product, the loaf bread, to the poly blends with chitosan promoted an inhibitory effect in the growing of molds and yeasts of around 50% (with poly blend containing 5 phr of chitosan when compared to chitosan-free blend), without affecting the humidity levels, water activity and texture of product, supporting the maintenance of the color during its storage. The contact of films with chitosan on minimally processed apples have promoted a decrease in the growing of molds and yeast of around 54% (with poly blends containing 5 phr of chitosan when it was compared to chitosan-free bled), without affecting the soluble solids levels, pH, texture and weight loss. It has contributed also to avoid the enzymatic browning and increased the total polyphenols levels by 20% and triplicated the antioxidant activity recorded after 10 days of storing the fruits that had been in contact with the poly blends PLA/EVA/PEG/QUI. Finally, it can be concluded that EVA/PEG and chitosan blends added to PLA have allowed modifications on the hardness and processability properties and that the application of chitosan proved to be an efficient action antimicrobial and antioxidant allowing the results obtained here and purpose of this study.
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Intharapat, Punyanich. "Thermoplastic natural rubbers based on natural rubber (NR) and ethylene vinyl acetate copolymer (EVA) with natural rubber-graft- poly(dimethyl(methacryloyloxymethyl)phosphonate) (NR-g-PDMMMP) as compatibilizer." Le Mans, 2009. http://cyberdoc.univ-lemans.fr/theses/2009/2009LEMA1005.pdf.
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Des copolymères greffés à base de caoutchouc naturel (NR) et de poly(acryloyloxyméthylphosphonate de diméthyle) (NR-g-PDMAMP), de poly(méthacryloyloxyéthylphosphonate de diméthyle) (NR-g-PDMMEP) et de poly(méthacryloyloxyméthylphosphonate de diméthyle) (NR-gPDMMMP), ont été synthétisés en milieu latex selon la méthode dite « grafting from » à partir de sites amorceurs photosensibles N ,Ndiéthyldithiocarbamate préalablement introduits le long des chaînes 1,4-polyisoprène du caoutchouc naturel. Des études de compatibilisation des mélanges caoutchouc naturel (NR) / copolymère d'éthylène - acétate de vinyle (EV A) ont par la suite été envisagées avec le copolymère NR-gPDMMMP, choisi comme agent compatibilisant. Elles ont été effectuées sur des mélanges simples 50/50 NR/EV A, mais aussi des mélanges dynamiquement vulcanisés 40/60 NR/EVA. Dans les deux cas,les influences du taux de greffage du NR-g-PDMMMP (71, 80, 89, et 95%) et du taux de chargement en compatibilisant (0, 1,3,5,7,9,12, et 15 % en poids par rapport au NR) sur les propriétés rhéologiques, dynamiques, mécaniques, morphologiques, et thermiques, ont été étudiées. Les meilleurs effets de compatibilisation ont été observées avec un copolymère NR-g-PDMMMP ayant un taux de greffage de 80 %, pour un taux de chargement de 7 % dans le cas du mélange simple 50/50 NR/EV A et de 9 % dans celui du mélange dynamiquement vulcanisé 40/60 NR/EV A. Les études microscopiques par SEM des mélanges ont montré une réduction de la taille des domaines. Il a aussi été noté que la stabilité thermique du mélange NR/EVA se trouve renforcée avec l'incorporation du NR-g-PDMMMPGraft copolymers of natural rubber and poly(dimethyl(acryloyloxymethyl)phosphonate) (NR-g-PDMAMP), natural rubber and poly(dimethyl(methacryloyloxyethyl)phosphonate) (NR-g-PDMMEP), and natural rubber and poly(dimethyl(methacryloyloxymethyl)phosphonate) (NR-g-PDMMMP), were prepared in latex medium via a "grafting from" methodology based on the photopolymerization of vinyl monomers initiated from N,N-diethyldithiocarbamate groups previously bound in side position of the 1,4-polyisoprene chains of natural rubber. Thereafter, compatibilization studies of natural rubber (NR) / ethylene vinyl acetate copolymer (EV A) blends were considered using NR-g-PDMMMP as a blend compatibilizer. The investigations were carried out on two categories of blends : uncured 50/50 and dynamically cured 40/60 NR/EV A blends. Ln the two cases, the influences of NR-g-PDMMMP grafting rates (i. E. , 71, 80, 89, and 95 %) and of loading level in compatibilizer (i. E. , 0, 1,3,5,7,9,12, and 15 wt% compared to NR) on rheological, dynamical, mechanical, morphological, and thermal properties, were studied. The best compatibilization effects were observed with a NR-g-PDMMMP having a grafting rate equal to 80 %, at a loading level of 7 wt% for 50/50 uncured blend and 9 wt% for 40/60 dynamically cured blend. In these conditions, the highest complex viscosity (positive deviation), tensile strength, and elongation at break, as well as the lowest values of tension set and tan d (damping factor), were observed. SEM micrographs of compatibilized blends showed a size decrease of the domains. It was also noted that the thermal stability of NR/EV A blends was improved by incorporating NR-g-PDMMMP
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Atanase, Léonard-ionut. "Contribution à l'étude des complexes Poly (vinyle alcool - vinyle acétate) / tensioactifs anioniques : caractéristiques colloïdales des nanogels et extension aux copolymères à blocs." Thesis, Mulhouse, 2010. http://www.theses.fr/2010MULH3728.
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Les copolymères poly (acétate de vinyle-co-alcool vinylique), désignés par PVA, sont des tensioactifs macromoléculaires obtenus par hydrolyse partielle de poly (acétate de vinyle)(PVAc). Si les propriétés tensioactives des PVA ont pu être corrélées aux caractéristiques moléculaires il n'en est par de même en ce qui concerne les associats du type nanogels présents dans les solutions aqueuses. L'objectif de cette thèse était de caractériser les nanogels par des techniques telles que la diffusion dynamique de la lumière, la chromatographie d'exclusion stérique et la viscosimétrie. 9 PVA, de degrés d'hydrolyse de 73 à 88 mole% et de degrés de polymérisation de 650 à 2500 ont été étudiés. Il est apparu que les nanogels présent dans les PVA de DH =73 mole% et formés par interactions hydrophobe-hydrophobe entre séquences acétate ont des tailles entre 20-40 nm, avec des fractions volumiques de l'ordre de 20-30%. La désagrégation des nanogels par formation de complexes avec des tensioactifs anioniques du type SDS et SDBS a ensuite été démontrée. En faisant appel à la technique de fractionnement par « point de trouble » il est apparu que les chaînes les plus riches en acétate et en particulier celles ayant des longueurs des séquences acétate importantes complexent plus de SDS.Des « copolymères modèles » du type copolymères diblocs PVAc-b-PVOH comportant une séquence hydrophobe PVAc et une hydrophile PVOH ont pu être préparés par polymérisation RAFT, suivie par une réaction click. Une étude préliminaire de la micellisation de tels copolymères a permis de montrer la très grande analogie entre micelles de copolymères à blocs PVAc-b-PVOH et les nanogels de PVA examinés précédemmentPoly (vinyl acetate-co-vinyl alcohol) copolymers, designated by PVA, are macromolecular surfactants obtained by partial hydrolysis of poly (vinyl acetate) (PVAc). If the surfactant properties of PVA have been correlated with molecular characteristics it is not the same for the colloidal aggregates in aqueous solutions so-called nanogels. The objective of this thesis was to characterize the nanogels using techniques such as dynamic light scattering, size exclusion chromatography and viscometry.9 PVA with degrees of hydrolysis between 73 and 88 mole% and polymerization degrees of 650 to 2500 were studied. It appeared that the nanogels, formed by hydrophobic-hydrophobic interactions between acetate sequences, are the size in the range of 20 to 40 nm with volume fractions between 20 and 30%. The disaggregation of nanogels by complex formation with anionic surfactants such as SDS and SDBS was further demonstrated. By using the "cloud point" fractionation technique it appeared that SDS is complexed by the sequences with high acetate content and in particular those with significant lengths of acetate sequences.As a model system diblock copolymers PVAc-b-PVOH containing a PVAc hydrophobie sequence and a PVOH hydrophilic sequence were prepared by RAFT polymerization, followed by a click reaction. A preliminary micellization study of these copolymers showed a very strong analogy between PVAc-b-PVOH block copolymer micelles and PVA nanogels discussed above
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Königsmann, Martin. "Modification of Wood Surfaces via controlled Polymerization Methods." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E4BA-1.
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Debnáriková, Michaela. "Krystalizace dvousložkových směsí polylaktidu a jejich morfologie." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-444214.
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Master thesis deals with the influence of polyvinylacetate, polycaprolactone, poly(butylene-adipate-co-terephtalate) and talc, ethylenevinylacetate, polyethylene glycol and monosodium citrate on the flow properties, mechanical properties and crystallization ability of PLA. The flow properties were studied using the melt flow index and mechanical properties were studied using a tensile test. The crystallinity was studied by differential scanning calorimetry and on a polarization optical microscope equipped with hot stage. Isothermal crystallization was performed at 95 and 105 °C for 3 h and non-isothermal crystallization was performed with a calorimeter at two cooling rates (1 and 10 °C/min). Upon the isothermal crystallization at 95 °C, the formation of denser crystalline structure was observed and the content of crystalline phase increased in most of the samples. The formation of spherulitic structure was observed at 105 °C in samples with 30 % PVAc, 30 % EVA and PEG. Reducing the cooling rate to 1 °C/min at non-isothermal crystallization had nearly no effect on the crystallization process of the most samples; the content of crystalline phase increased in the samples containing PBAT and PEG, which revealed double melting peak during subsequent heating. The crystalline fraction was the most significantly affected by the addition of PEG. All added polymers except PVAc affected the mechanical properties; PBAT, PCL, EVA and PEG increased the strain and decreased the strength and modulus of elasticity. The samples containing monosodium citrate showed unsatisfactory mechanical properties and could not be measured. The samples containing higher concentration of EVA copolymer showed the phase separation.
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Pöllinger-Tieg, Catherine [Verfasser], K. [Akademischer Betreuer] Mäder, J. [Akademischer Betreuer] Siepmann, and J. [Akademischer Betreuer] Kressler. "Development and investigation of Propranolol HCl pellets coated with poly(vinyl acetate) based polymer films for sustained release applications / Catherine Pöllinger-Tieg. Betreuer: K. Mäder ; J. Siepmann ; J. Kressler." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2012. http://d-nb.info/1029083649/34.
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Atanase, Léonard-Ionut. "Contribution à l'étude des complexes Poly (vinyle alcool - vinyle acétate) / tensioactifs anioniques : caractéristiques colloïdales des nanogels et extension aux copolymères à blocs." Phd thesis, Université de Haute Alsace - Mulhouse, 2010. http://tel.archives-ouvertes.fr/tel-00562063.
Full textAbstract:
Les copolymères poly (acétate de vinyle-co-alcool vinylique), désignés par PVA, sont des tensioactifs macromoléculaires obtenus par hydrolyse partielle de poly (acétate de vinyle)(PVAc). Si les propriétés tensioactives des PVA ont pu être corrélées aux caractéristiques moléculaires il n'en est par de même en ce qui concerne les associats du type nanogels présents dans les solutions aqueuses. L'objectif de cette thèse était de caractériser les nanogels par des techniques telles que la diffusion dynamique de la lumière, la chromatographie d'exclusion stérique et la viscosimétrie. 9 PVA, de degrés d'hydrolyse de 73 à 88 mole% et de degrés de polymérisation de 650 à 2500 ont été étudiés. Il est apparu que les nanogels présent dans les PVA de DH =73 mole% et formés par interactions hydrophobe-hydrophobe entre séquences acétate ont des tailles entre 20-40 nm, avec des fractions volumiques de l'ordre de 20-30%. La désagrégation des nanogels par formation de complexes avec des tensioactifs anioniques du type SDS et SDBS a ensuite été démontrée. En faisant appel à la technique de fractionnement par " point de trouble " il est apparu que les chaînes les plus riches en acétate et en particulier celles ayant des longueurs des séquences acétate importantes complexent plus de SDS.Des " copolymères modèles " du type copolymères diblocs PVAc-b-PVOH comportant une séquence hydrophobe PVAc et une hydrophile PVOH ont pu être préparés par polymérisation RAFT, suivie par une réaction click. Une étude préliminaire de la micellisation de tels copolymères a permis de montrer la très grande analogie entre micelles de copolymères à blocs PVAc-b-PVOH et les nanogels de PVA examinés précédemment.
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Zimmermann, Matheus Vinicius Gregory. "Desenvolvimento de compósitos expandidos de poli(etileno-co-acetato de vinila) - eva reforçados com pó de madeira e com fibra de bananeira." reponame:Repositório Institucional da UCS, 2013. https://repositorio.ucs.br/handle/11338/814.
Full textAbstract:
Compósitos expandidos ou compósitos celulares reforçados com fibras vegetais são uma
classe emergente de materiais que combinam boas propriedades mecânicas com densidade
reduzida e capacidade superior de absorção de energia a impacto, isolamento térmico e
acústico, quando comparados aos compósitos convencionais não expandidos. Os compósitos
expandidos são constituídos basicamente de três fases, (1) a matriz polimérica, (2) o agente de
reforço e (3) os espaços vazios no interior do compósito, que são denominados células. Nesse
sentido, o presente estudo tem por objetivo o desenvolvimento de compósitos expandidos de
poli(etileno-co-acetato de vinila) (EVA) reforçado com dois tipos de reforços de origem
vegetal: a fibra de bananeira (FB) e o pó de madeira (PM), em diferentes concentrações e
tamanhos de partícula. Inicialmente, foi avaliada a influência do tratamento alcalino em
diferentes concentrações, nas propriedades térmicas (TGA), químicas (FTIR), físicas e
morfológicas (MEV) da FB, e as propriedades mecânicas (rasgamento e tração) dos
compósitos produzidos com a FB tratada. Para a produção dos compósitos expandidos,
inicialmente, foi inserido na matriz do EVA o agente compatibilizante polietileno graftizado
com anidrido maleico (PEgMA) em uma extrusora monorrosca. A FB, o PM e os aditivos
foram incorporados ao EVA/PEgMA em um moinho de rolos, e o composto foi conformado e
expandido por compressão em uma prensa térmica com moldes de volumes variados. Os
compósitos expandidos foram avaliados quanto às propriedades físicas (densidade e absorção
de água), mecânica (resistência ao rasgamento, resistência à compressão e dureza), térmica
(TGA), química (FTIR) e morfológica (MEV e MO). Os resultados demonstraram que os
compósitos expandidos apresentaram redução de densidade de 70 a 30%, de acordo com o
molde utilizado no processo de expansão. O uso de ambos os reforços vegetais interferem na
estrutura morfológica das células nos compósitos expandidos, promovendo a formação de
células de tamanho e formato heterogêneo, compostas por células abertas e fechadas. Os
reforços também atuam como agentes de nucleação na formação das células, proporcionando
redução do tamanho e aumento na densidade das células com o aumento do teor de carga. A
resistência ao rasgamento tende a diminuir com a diminuição da densidade e aumento do teor
de carga, enquanto as propriedades mecânicas de resistência à compressão e dureza aumentam
com o aumento do teor de carga. Em todos os compósitos desenvolvidos, na região da
interface polímero-fibra, os compósitos apresentam regiões com boas e fracas propriedades de
adesão.Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-07-10T17:21:11Z No. of bitstreams: 1 Dissertacao Matheus Vinicius Gregory Zimmermann.pdf: 4275549 bytes, checksum: 8a3ddad83d9ea350108ccc795409de2b (MD5)
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Expanded composites or vegetable fiber-reinforced cell composites are a new emerging class of materials combining good mechanical properties of reduced density, having superior ability of energy absorption at impact, as well as thermal and acoustic isolation. Expanded composites are basically constituted of three phases, the polymeric matrix, the reinforcing agent and the void spaces in the interior of the composite, called cells. In this context, the present study aims at the development of expanded poly (ethylene-co-vinyl acetate) (EVA) composites reinforced with two kinds of vegetable fibers, banana fiber (BF) and wood flour (WF) at different concentrations and particle sizes. Initially the influence of sodium hydroxide-based (NaOH) alkaline treatment at different concentrations was evaluated as regards thermal (TGA), chemical (FTIR), physical and morphological (SEM) properties of BF as well as mechanical properties (tear and tensile) of the composites obtained from treated BF. For the production of the expanded composites initially the compatibilizing agent maleic anhydride grafted polyethylene (PEgMA) was inserted into the EVA matrix with the aid of a single screw extruder. The BF and WF fibers were incorporated into EVA/PEgMA using an open roll mill and the composite was shaped and expanded using a thermal press having variable volume dies. The expanded composites were evaluated as for physical (density, water absorption), mechanical (tear strength and hardness), thermal (TGA), chemical (FTIR) and morphological (SEM) properties. The results demonstrated that the expanded composites attained between 70 and 30% reduction in density according to the die utilized in the expansion process. The use of both fibers affect the morphological structure of cells in the composites, promoting the formation of heterogeneous structures made up of open and closed cells. Vegetable fibers work as nucleating agents in the formation of cells, providing size reduction and increased density of the cells as a result of the increased filler content. Mechanical properties of tear strength tend to diminish with reduced density and increased filler content, while mechanical properties of compression strength and hardness increase with increased filler content. In the polymer-fiber interface all composites exhibit some regions of good adhesion and other ones of poor adhesion between the matrix and the vegetable fiber.
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Alberton, Josué. "Preparação e caracterização de compósitos de polipropileno, carbonato de cálcio e poli(etileno-co-acetato de vinila) utilizados na produção de chapas termoplásticas." Florianópolis, SC, 2008. http://repositorio.ufsc.br/xmlui/handle/123456789/91059.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Ciências e Engenharia de Materiais.Made available in DSpace on 2012-10-23T18:23:47Z (GMT). No. of bitstreams: 1 259875.pdf: 5087120 bytes, checksum: 59d3b0064204d6ec0cbef0d163323cec (MD5)
No mercado cada vez mais competitivo, a sobrevivência das indústrias depende da redução dos custos de produção e do aumento significativo da produtividade. Estudar as propriedades de compósitos poliméricos utilizados em processos de transformações de polímeros é uma das maneiras encontradas para reduzir os custos. Por outro lado, a possibilidade de empregar tecnologias como a co-extrusão, também apresenta vantagens econômicas. A produção de compósitos poliméricos não pode ser realizada sem que sejam previstos ou calculados os impactos gerados no processamento e as modificações provocadas nas propriedades físicas, químicas, térmicas, mecânicas, morfológicas e reológicas dos materiais. A adição de 30% de CaCO3-EVA aumentou a estabilidade térmica do polipropileno na ordem de 32,6ºC, reduzindo a propriedade referência para projetos de embalagens plásticas, o DTUL em 15ºC. Volumes mássicos até o limite de 20% da composição de CaCO3-EVA podem ser utilizados nas formulações dos compósitos de polipropileno. Acima desse valor, podem ocorrer problemas com a estabilidade do fluxo do material fundido nos processos de extrusão ou co-extrusão, prejudicando, consequentemente, as propriedades mecânicas dos compósitos. Para preservar a integridade durante e após o envasamento de produtos, sugere-se que a composição de CaCO3-EVA seja utilizada na linha de embalagens projetadas para atender a solicitações mecânicas entre 20 MPa e 30 MPa e térmicas na faixa de 20ºC a 50ºC.
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Lim, Henry C. A. "The influence of reactive modification on the compatibility of polyolefins with non-olefinic thermoplastics." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8372.
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Polyethylene (PE) resins being non-polar in nature and having a high degree of crystallinity have limited miscibility and compatibility when blended with polar polymers. The miscibility and compatibility of these blends are generally worsened when they are prepared by direct injection moulding without a precompounding process. Such situations are commonly encountered in particular by polymer converters when blending colour and/or additive concentrates, commonly known as masterbatches. Typically, masterbatches are mixtures containing high loading of pigments and/or additives predispersed in a suitable solid vehicle (commonly known as carrier) such as a polyethylene resin. These masterbatches are usually used for the colouration of a wide range of polymers and the carrier used must therefore be compatible with these matrix (host) polymers. The preliminary stage of this study involved the investigation of the properties of blends based on high density polyethylene (HDPE) and a range of engineering thermoplastics (ABS, PC, PBT, PA6), prepared by injection moulding. Five different types of compatibilisers namely, ethylene-vinyl acetate (EVA) copolymer, ethylene-methyl acrylate (EMA) copolymer, ethylene-glycidyl methacrylate (E-GMA) copolymer, ethylene-methyl acrylateglycidyl methacrylate (E-MA-GMA) terpolymer and maleic anhydride grafted HDPE (HDPE-g-MAH) copolymer were evaluated with respect to their efficiencies in compatibilising HDPE with the four engineering polymers. The pre-compounded HDPE/compatibiliser binary blends at 2 different blend ratios (1:1 and 3:1) were added at 15 wt% concentration to each engineering thermoplastics and test samples were produced directly by injection moulding. Results of mechanical testing and characterisation of the blends showed that glycidyl methacrylate compatibilisers, E-MA-GMA, in particular have the most universal compatibilising effectiveness for a range of engineering thermoplastics including ABS, PC, PBT, and PA6. Blends compatibilised with E-MA-GMA compatibiliser had the best notched impact performance irrespective of matrix polymer type. The presence of an acrylic ester (methyl acrylate) comonomer in E-MA-GMA resulted in increased polarity of the ii compatibiliser leading to improved miscibility with the polar matrix polymers demonstrated by fine blend morphologies, melting point depression and reduction in crystallinity of the HDPE dispersed phase. The second stage of this study involved the reactive modification of HDPE using a low molecular weight di-functional solid diglycidyl ether of bisphenol A (DGEBA) type epoxy resin compatibilised with HDPE-g-MAH in an attempt to improve its compatibility with ABS, PBT and PA6. The maleic anhydride moieties in HDPE-g-MAH served as reactive sites for anchoring the epoxy moieties while the HDPE backbone was miscible with the HDPE resin. An excessive amount of reactive groups resulted in the formation of crosslinked gels while the addition of EVA co-compatibiliser helped in the reduction of gel content and further improved the dispersion of the epoxy. The effectiveness of epoxy grafted HDPE (with and without EVA co-compatibiliser) in compatibilising ABS/HDPE, PBT/HDPE, and PA6/HDPE was investigated by injection moulding of 5 wt% functionalised HDPE with these matrix polymers into test bars for mechanical testing, and characterisation by differential scanning calorimtery (DSC) and optical microscopy. The reactively functionalised HDPE blends, improved the mechanical properties of ABS and PA6 blends especially with EVA as co-compatibiliser. However, the mechanical properties of PBT blends were unmodified by the functionalised HDPE which was believed to be due to end-capping of the PBT chain-ends by ungrafted epoxy resins.
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Dekyndt, Bérengère. "La libération modifiée de principes actifs, développement de deux approches." Thesis, Lille 2, 2015. http://www.theses.fr/2015LIL2S005.
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Les thérapeutiques individualisées et ciblées se développent actuellement, les formes galéniques évoluent donc en parallèle pour contrôler la libération des principes actifs (PA) et les conduire au plus proche des sites d’intérêts. Les formes orales solides représentent les formulations galéniques les plus utilisées, faciles d’emploi, indolores et réduisant le risque d’infection. Lors de leur conception, il est aussi possible de moduler la libération du PA.Deux approches sont étudiées dans ce manuscrit, l’une correspond au ciblage de la libération d’un PA vers son site d’action thérapeutique qui est le colon, la seconde consiste à contrôler la libération du PA pour maintenir une concentration constante, minimiser les effets indésirables et les périodes de présence de concentrations sub-thérapeutiques au niveau du site d’action.Première approche :Les traitements des Maladies Inflammatoires Chroniques de l’Intestin (MICI) peuvent être significativement améliorées par une libération localisée du PA. Une des approches est l’utilisation d’enrobages composés de polysaccharides dégradés par les enzymes sécrétées par la microflore colique. Mais l’absence d’une méthode in vitro reproductible simulant les conditions physiologiques du colon et l’impact potentiel des traitements antibiotiques associées qui pourraient affecter la quantité et la qualité des bactéries présentes et des enzymes sécrétées est un obstacle à sa mise au point. L’objectif de l’étude était d’effectuer un screening de polysaccharides ayant un intérêt dans le développement de nouvelles formulations à libération colique. Après cette sélection, la libération des formulations retenues ont été évaluées par une méthode utilisant des selles de patients atteints de MICI traités ou non par antibiothérapie. Enfin, l’utilisation de mélanges bactériens pour un éventuel remplacement de l’utilisation de selles fraiches a été évaluée.Seconde approche : Les formes orales enrobées présentent un grand potentiel pour la libération contrôlée de PA. Néanmoins, il est difficile d’obtenir une libération à vitesse constante avec ce type de formulation. Ceci est généralement dû au rôle prédominant du transport de masse par diffusion, ce qui entraine, avec le temps, une diminution de la concentration en PA au cœur du système, donc une réduction du gradient de concentration qui est la force motrice de la libération du PA. Ce type de cinétique de libération peut être inapproprié pour un traitement médicamenteux sûr et efficace. Malgré l’importance pratique de ce défi crucial de formulation, étonnamment, peu de stratégies efficaces sont connues. Dans cette étude, une nouvelle approche, basée sur une succession de couches de PA et de polymères (initialement dépourvu de PA) présentant une distribution initiale de PA non homogène, associé à un effet de temps de latence et à une diffusion partielle initiale à travers le noyau de la minigranule. Des variations de type, de quantité, d’épaisseur et de séquence des couches de PA et de polymères ont été testées. Un système assez simple composé de quatre couches (deux couches de PA et deux couches de polymère) permettait d’aboutir à une libération relativement constante durant 8hIndividualized and targeted therapies are currently developed, therefore the dosage forms move in parallel to control the drug release and drive it nearest to interest sites. Solid oral dosage forms are the pharmaceutical formulations the most common, easy to use, painless and reducing the infectious risk. In these formulation designs, it is also possible to adjust the drug release.Two approaches are discussed in this manuscript, the first one targets the drug release to the therapeutic site of action which is the colon, and the second one consists on controlling the drug release to maintain a constant concentration, minimize side effects and periods of presence of sub-therapeutic concentrations at the site of action.The first approach:The treatment of colonic disease like Inflammatory Bowel Diseases (IBD), can be significantly improved via local drug delivery. One approach is to use polysaccharide coatings, which are degraded by enzymes secreted by the colonic microflora. However, the lack of a reliable in vitro test simulating conditions in a living colon and the potential impact of associated antibiotic treatments that could affect the quality and quantity of bacteria and enzymes secreted is an obstacle to its development. The aim of the study was to perform a screening of polysaccharides suitable for the development of new colonic release formulations. After this selection, the drug release of selected formulations were evaluated by a method using the stools of IBD patients treated or not with antibiotics. Finally, the use of bacterial mixtures substituting fresh fecal samples has been evaluated.The second approach: Coated pellets offer a great potential for controlling drug delivery systems. However, constant drug release rates are difficult to achieve with this type of dosage forms if the drug is freely water-soluble. This is because diffusional mass transport generally plays a major role and with time the drug concentration within the system decreases, resulting in decreased concentration gradients, which are the driving forces for drug release. This type of release kinetics might be inappropriate for an efficient and safe drug treatment. Despite the great practical importance of this potentially crucial formulation challenge, surprisingly little is yet known about efficient formulations. In this study, a novel approach is presented based on sequential layers of drug and polymer (initially free of drug) to provide a non-homogeneous initial drug distribution, combined with lag-time effects and partial initial drug diffusion towards the pellet’s core. By changing the type, number, thickness and sequence of the drug and polymer layers, a rather simple 4 layers system (2 drug and 2 polymer layers) allowed an about constant drug release during 8 h
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KUMAR, NITESH. "MODIFICATION IN MECHANICAL & THERMAL PROPERTIES OF EPOXY THROUGH BLENDING WITH POLY (VINYL ACETATE)." Thesis, 2016. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15009.
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Epoxy resins are a class of thermoset materials used extensively in structural and specialty composite applications because they offer a unique combination of properties that are unattainable with other thermoset resins. Available in a wide variety of physical forms from low-viscosity liquid to high-melting solids, they are amenable to a wide range of processes and applications.
Epoxies offer high strength, low shrinkage, excellent adhesion to various substrates, effective electrical insulation, chemical and solvent resistance, low cost, and low toxicity. They are easily cured without evolution of volatiles or by-products by a broad range of chemical specie. Epoxy resins are also chemically compatible with most substrates and tend to wet surfaces easily, making them especially well-suited to composites applications.
Epoxy resin are characterized by more than one 1, 2- epoxy group per molecule. Three-membered epoxy ring is highly reactive to many substances, particularly by with proton donor (eg: amine, anhydride).
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Ting, Chin Jou, and 丁振洲. "Study the effect of poly(starch-g-vinyl acetate) on the mecha- nical properties of poly(vinyl cholride-ran-vinyl acetate)." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/29364460100088624424.
Full textAbstract:
碩士中原大學
化學工程研究所
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Vinyl chloride-Vinyl acetate copolymer, generally is proc- essed for product in rigid or in flexual formula. When starch or its derivatives is filled in the formula will promote an effective biodegradable copolymer. In the rigid copolymer containning 12% vinyl acetate, wit- hin 15% of filler containned, tensile strength increase as following seqence of starch < graft copolymer < coarse graft copolymer. In the case of plasticizer added, flexual copolymer conta- inned 8% vinyl acetate, within 10% of filler containned, tens- ile strength increase as following sequence of starch = graft copolymer < coarse graft copolymer, and with containning 12% vinyl acetate,within the same 10% of filler containned, coarse graft copolymer was better than starch in both tensile streng- th and elongation. Under the same quantity of polyvinyl acetate side chain, rigid copolymer containning 12% vinyl acetate, generally shows higher water absorption than those containning 8% vinyl acet- ate, and under the case of same filler, more quantity of the filler, there are an higher water absorption. In the case of flexual copolymer, with same quantity of filler and the more the polyvinyl acetate side chain, the hig- her the water absorption, and the water absorption increased as following sequence of starch < coarse graft copolymer < graft copolymer.
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金家鳳. "Studies on chhitosan-g-poly(vinyl acetate)and chitosan-g-poly(vinyl alcohol)copolymers." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/89607313990826351109.
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