Dissertations / Theses on the topic 'Polymer composites'
To see the other types of publications on this topic, follow the link: Polymer composites.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Polymer composites.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Rhodes, Susan M. "Electrically Conductive Polymer Composites." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1194556747.
Full text
2
Pierini, Filippo <1981>. "Conductive Polymer Composites." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5409/1/Pierini_Filippo_tesi.pdf.
Full textAbstract:
In recent years, nanotechnologies have led to the production of materials with new and sometimes unexpected qualities through the manipulation of nanoscale components.
This research aimed primarily to the study of the correlation between hierarchical structures of hybrid organic-inorganic materials such as conductive polymer composites (CPCs).
Using a bottom-up methodology, we could synthesize a wide range of inorganic nanometric materials with a high degree of homogeneity and purity, such as thiol capped metal nanoparticles, stoichiometric geomimetic chrysotile nanotubes and metal dioxide nanoparticles. It was also possible to produce inorganic systems formed from the interaction between the synthesized materials.
These synthesized materials and others like multiwalled carbon nanotubes and grapheme oxide were used to produce conductive polymer composites.
Electrospinning causes polymer fibers to become elongated using an electric field. This technique was used to produce fibers with a nanometric diameter of a polymer blend based on two different intrinsically conducting polymers polymers (ICPs): polyaniline (PANI) and poly(3-hexylthiophene) (P3HT).
Using different materials as second phase in the initial electrospun polymer fibers caused significant changes to the material hierarchical structure, leading to the creation of CPCs with modified electrical properties. Further study of the properties of these new materials resulted in a better understanding of the electrical conductivity mechanisms in these electrospun materials.
3
Pierini, Filippo <1981>. "Conductive Polymer Composites." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5409/.
Full textAbstract:
In recent years, nanotechnologies have led to the production of materials with new and sometimes unexpected qualities through the manipulation of nanoscale components.
This research aimed primarily to the study of the correlation between hierarchical structures of hybrid organic-inorganic materials such as conductive polymer composites (CPCs).
Using a bottom-up methodology, we could synthesize a wide range of inorganic nanometric materials with a high degree of homogeneity and purity, such as thiol capped metal nanoparticles, stoichiometric geomimetic chrysotile nanotubes and metal dioxide nanoparticles. It was also possible to produce inorganic systems formed from the interaction between the synthesized materials.
These synthesized materials and others like multiwalled carbon nanotubes and grapheme oxide were used to produce conductive polymer composites.
Electrospinning causes polymer fibers to become elongated using an electric field. This technique was used to produce fibers with a nanometric diameter of a polymer blend based on two different intrinsically conducting polymers polymers (ICPs): polyaniline (PANI) and poly(3-hexylthiophene) (P3HT).
Using different materials as second phase in the initial electrospun polymer fibers caused significant changes to the material hierarchical structure, leading to the creation of CPCs with modified electrical properties. Further study of the properties of these new materials resulted in a better understanding of the electrical conductivity mechanisms in these electrospun materials.
4
Shi, Y. "Bioinspired ordered polymer-composites." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1545259/.
Full textAbstract:
In this project, clays including montmorillonite, laponite, Black Hills bentonite as well as kaolinite were used to fabricate the layered structure of nacre. A solution casting method was used to build the hierarchical nacre-like composite and in-situ photo polymerisation, vacuum impregnation and vacuum assisted filtration methods were employed for preformed clay sheets and polymers (methyl methacrylate, tri(ethyleneglycol) dimethacrylate, poly(propylene glycol) dimethacrylate as well as epoxy resin) to mimic the structure of nacre. XRD was used to indicate the intercalation of polymer and orientation function of clay sheets and SEM for microstructure detection. Tensile testing was used to investigate the properties of different volume fraction (40-70 vol. %) composites and the highest value 98 MPa came from 50 vol. % MMT/PVA composite. The mechanism of polymerisation of acrylic groups with clays present was analysed and redox polymerisation was introduced for the kaolinite/PMMA system. Kaolinite/ PMMA samples were tested via three points loading and a composite with flexural strength of (40 ± 20) MPa and flexural modulus of (30 ± 20) GPa was obtained.
5
Jezzard, Peter. "Nuclear magnetic resonance imaging of polymers and polymer-composites." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277832.
Full text
6
Kaali, Peter. "Antimicrobial Polymer Composites for Medical Applications." Doctoral thesis, KTH, Polymera material, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33393.
Full textAbstract:
The current study and discuss the long-term properties of biomedical polymers in vitro and invivo and presents means to design and manufacture antimicrobial composites. Antimicrobialcomposites with reduced tendency for biofilm formation should lead to lower risk for medicaldevice associated infection.The first part analyse in vivo degradation of invasive silicone rubber tracheostomy tubes andpresents degradation mechanism, degradation products and the estimated lifetime of thematerials.. It was found that silicone tubes undergo hydrolysis during the long-term exposurein vivo, which in turn results in decreased stability of the polymer due to surface alterationsand the formation of low molecular weight compounds.The second part of the study presents the manufacturing of composites with single, binary andternary ion-exchanged zeolites as an antimicrobial agent. The ion distribution and release ofthe zeolites and the antimicrobial efficiency of the different systems showed that single silverion-exchanged zeolite was superior to the other samples. Antimicrobial composites wereprepared by mixing the above-mentioned zeolites and pure zeolite (without any ion) withdifferent fractions into polyether (TPU), polyether (PEU) polyurethane and silicone rubber.The antimicrobial efficiency of binary and ternary ion-exchanged samples was similar whichis thought to be due to the ion distribution in the crystal structure.The changes in the mechanical and surface properties of the composites due to the zeolitecontent demonstrated that the increasing zeolite content reduced the mechanical propertieswhile the surface properties did not change significantly. The antimicrobial tests showed thatthe silver-containing composite was the most efficient among all the other samples. Thebinary and ternary ion-exchanged composites expressed similar antimicrobial efficiency as itwas seen previously for the different zeolite systems. Biocompatibility was studied byexposure to artificial body fluids to simulate the degradation of the composites in the humanbody. Significant changes were observed in the morphology, the surface properties and the chemical structure.QC 20110511
7
Guo, Molin. "PROCESSING-STRUCTURE-PROPERTY RELATIONSHIPS INCO-CONTINUOUS POLYMER BLENDS AND COMPOSITES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1593786851492932.
Full text
8
Li, Ruihua. "Single polymer composites made of slowly crystallizing polymer." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33925.
Full textAbstract:
Composites are widely used in an increasing number of applications in diverse fields. However, most traditional composite materials are difficult to recycle. Because of their enhanced recyclability, thermoplastic single-polymer composites (SPCs), i.e., composites with fiber and matrix made from the same thermoplastic polymer, have attracted much attention in the recent years. High-performance polymer fibers in combination with same polymer matrices would lead to a fully recyclable single polymer composite that has major ecological advantages. However, because a single polymer is involved in the composite, thermoplastic SPCs manufacturing presents a unique set of technical problems, and different approaches from those in standard composites manufacturing are frequently needed. Two specific issues in SPCs manufacturing are how to produce distinct forms of the same polymer and how to consolidate them. So far, most investigations have been reported on a single-component hot compaction method and two-component molecular methods. However, in these methods, either the processing window is too narrow or some impure materials are introduced into the system. The key issue in thermoplastic SPCs processing is how to melt-process the matrix without significantly annealing or even melting the fiber. To overcome the above drawbacks in existing SPCs processing, particularly to widen the SPCs processing temperature window and to purify the SPCs, a novel SPCs manufacturing process utilizing the characteristics of slowly crystallizing polymers was developed and investigated. Highly oriented and highly crystalline fibers made of a slowly crystallizing polymer are mixed with the amorphous form of the same polymer and then consolidated together under heat and pressure. In this dissertation research, two slowly crystallizing polymers, poly(ethylene terephthalate) (PET) and poly(lactic acid) (PLA), were used as model systems for SPCs processing.. To study the deformation and failure mechanisms of PET and PLA SPCs, the SPCs were characterized using tensile test, tearing test, impact test, SEM, optical microscopy, and other methods. The change of crystallinity and orientation of the material forms during SPCs processing were characterized by DSC and XRD. The effects of major process conditions on the performance of the SPCs were studied. It was found that the processing temperature played a profound role in affecting the fiber-matrix bonding property. The compression molded SPCs exhibited enhanced mechanical properties. For the PET SPCs with 45% by weight fiber content the tensile strength is four folds of that of non-reinforced PET. After reinforcement, the tearing strength of the PLA SPCs is almost an order higher than that of the non-reinforced PLA.
The fusion bonding behavior of two crystallizable amorphous PET sheets was also studied. Several characterization methods including SEM, TEM and polarized microscopy (either on etched or on non-etched samples) were used to observe interfacial bonding morphology of the crystallizable amorphous PET sheets. For a bonded sample, a layer of transcrystals with a thickness of 1-2 Ým was found right at the interface. A secondary but much larger zone with a distinct morphology was observed outside the transcrystal layer. With increase of the heating time, the width of the whole interfacial region decreases. The interfacial morphology was found to significantly affect the interfacial bonding quality. The testing results further indicated that high bonding temperature with an appropriate holding time promotes interfacial bonding of two crystallizable amorphous PET.
9
MARINAKOS, EFSTATHIA (STELLA) MARIA. "SYNTHESIS OF GOLD/POLYMER COMPOSITES, MICELLE/POLYMER COMPOSITES, AND POLYMER NANOCAPSULES. DIFFUSION STUDIES AND ENCAPSULATION OF GUEST MOLECULES." NCSU, 2002. http://www.lib.ncsu.edu/theses/available/etd-08042002-195606/.
Full textAbstract:
The template synthesis of core / shell particles is described. One template employed as the core is a gold particle. Polymers employed as the shell are polypyrrole, poly(N-methylpyrrole), and poly(3-methylthiophene). The gold core of the composite particle is removed to yield a hollow polymer capsule, the core dimensions of which are determined by the dimensions of the template. Shell thickness is also controlled easily. Permeability of the shell is varied according to shell composition, oxidation state of the polymer, and incorporated counterion. Attaching rhodamine B, anthraquinone, or horseradish peroxidase to the gold particle template prior to shell formation and removal of the core results in encapsulation of the molecule. A second template employed as the core is a micelle. Micelle core / polymer shell particles may possibly be further utlilized as an encapsulation method by solubilizing a molecule in the core of the micelle prior to polymer shell formation.
10
Bühler-Paschen, Silke. "Electron transport in polymer composites /." [S.l.] : [s.n.], 1995. http://library.epfl.ch/theses/?nr=1365.
Full text
11
Repasi, Ivett. "Expanded graphite filled polymer composites." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557649.
Full textAbstract:
The aim of this project was to produce expanded graphite (EO) and modified EO-filled electrically conductive polymer composites and to investigate the effects of different additive modifications and preparation conditions on the microstructure and electrical properties of these composites. Modifications included the use of dry blending and ultrasound to reduce their size, use of various suspension media and surfactants to stabilize particle suspensions. To compare the effectiveness of different filler modification processes on electrical conductivity, unmodified and treated EO were incorporated into polypropylene (PP) by melt mixing and EO based dispersions were used to make polyvinyl alcohol (PV A) composites by solution casting. The PP composites were made using various processing methods and conditions at filler concentrations up to 12 wt%, while the polyvinyl alcohol samples contained graphite concentrations up to 8 wt%. To analyse the crystalline morphology of sample and the dispersion of the filler in the composites samples were analysed by light and electron microscopy, DSC and X-ray diffraction. TOA was also used to investigate the thermal stability of the composites. It was found that the presence of graphite, significantly changed the crystal morphology of PP. Solution mixed PVA samples showed improved dispersion and the particle size was effectively reduced.
12
Corradi, Roberto. "Conducting polymer-silica colloidal composites." Thesis, University of Sussex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263866.
Full text
13
Ramakrishna, S. "Knitted fabric reinforced polymer composites." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385354.
Full text
14
Sobeshchuk, Nina. "Microlasers based on polymer composites." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLN031/document.
Full textAbstract:
L'objectif de la thèse est la fabrication et caractérisation de microlasers 3D à base de polymères dopés par des colorants organiques et des nanoparticules d'erbium et Ytterbium. Au début, nous avons étudié des structures polymères avec de très bons facteurs d'aspect, ainsi que le déplacement de nanoparticules lors de l'exposition à un éclairement périodique. La réalisation majeure de cette thèse est l'obtention de microlasers 3D par lithographie UV. Ensuite nous avons comparé les seuils lasers de ces structures pour différentes méthodes de fabrication. Dans des micro-cubes, nous avons identifié des orbites périodiques planes en forme de carré. L'analyse des orbites périodiques dans des microlasers Fabry-Perot 3D a montré que leur forme dépend du colorant, de la nature du substrat et de la taille de la structure (largeur et épaisseur).La dernière partie de ce travail consiste en la synthèse de nanoparticules d'oxyde d'erbium et ytterbium à basse température et en milieu anhydre. Ces nano-particules ont ensuite été introduites dans des composites à base de polymères qui ont donné lieu à la fabrication de micro-lasers 3D et à leur caractérisationThe aim of the thesis is the fabrication and optical characterization of three-dimensional organic microlasers based on organic dyes and luminescent erbium/ytterbium nanoparticles.At the beginning, we considered submicron polymer structures with high aspect ratio, as well as the phenomenon of redistribution of nanoparticles in the volume of the composite during the exposure by a periodic light field pattern.The main part of the work is devoted to obtaining three-dimensional polymer microlasers by UV-lithography. Comparison of the lasing threshold for microcavities obtained by different methods was performed. Periodic orbits in cuboid microlasers with square cross-section were identified. Analysis of possible periodic orbits in microlasers Fabry-Perot showed that the shape of the orbit depends on the dye, the type of substrate and the size of the microlaser (width, height).The last part of the work contains a study of low-temperature synthesis of luminescent nanoparticles of erbium and ytterbium oxides in a anhydrous medium, and polymer composites based on them. Three dimensional organic microlasers doped by these luminescent nanoparticles were obtained and investigated
15
Gilfillan, William N. "Developing starch-based polymer composites." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/86612/6/William_Gilfillan_Thesis.pdf.
Full textAbstract:
This project aim was to replace petroleum-based plastic packaging materials that pollute the environment, with biodegradable starch-based polymer composites. It was demonstrated that untreated sugar cane bagasse microfibres and unbleached nanofibres significantly improved the physical, mechanical and chemical properties of starch films, while thermal extrusion of starch with alcohol improved the stiffness and the addition of aconitic acid cross-linked the film making it moisture resistant and extensible.
16
MAZZANTI, Valentina. "Rheology of Wood Polymer Composites." Doctoral thesis, Università degli studi di Ferrara, 2015. http://hdl.handle.net/11392/2389015.
Full textAbstract:
Wood plastic composite (WPC) is a material composed of a thermoplastic matrix filled with wood fibers at different concentrations. This material is widely used for decking and automotive applications. With respect to wood it requires less maintenance, shows better durability in wet environment and can be obtained from recycled materials. With respects to plastics the main advantage is its lower cost.
The aim of this thesis has been to investigate the mechanical and rheological properties of PP based Wood Polymer Composites.
The mechanical characterization has shown that wood fibers make the composite stiffer without lowering strength values too much, while thermal properties have confirmed that the processing window for this material is rather narrow, being limited upwards by wood fiber degradation and downwards by the melting temperature, which is around 165°C.
Commercial PP-based WPCs filled with different filler concentration have been investigated with an off – line rheometer in oscillation mode at 170°C. Complex viscosity increases with the percentage of fibers. All materials show a shear-thinning behaviour with similar slopes of the flow curves and neat PP also displays a Newtonian plateau at low shear rates. The test temperature is imposed by the requirement of performing the test within the linear viscoelasticity region, but the data that are measured are not directly useful for processing, as a convenient processing temperature should be around 195°C.
In order to obtain the WPC viscosity at such temperatures, a model that uses the WPC viscosity measured at 170°C at various wood quantities and of neat PP viscosity measured at various temperatures is proposed. The main hypothesis of this model is that the effects of temperature and filler content on the composite viscosity are disjoint. These measurements permit to create shift factors that allow to estimate the WPC viscosity on the basis of neat PP viscosity, temperature and fibers content.
In order to validate the model, flow curve of 30%wt. and 70%wt. WPC at 195°C have been measured with an instrumented extruder slit die that allows the determination of the flow characteristics of the material in a condition that is very similar to the actual processing conditions. The slit die, connected with a single screw extruder, has a channel that is 50 mm wide and 105 mm long. Three heights are used for the Mooney procedure and three pressure transducers are flush mounted along the slit to eliminate the need for the Bagley correction.
The results show that the viscosity curve for the 30% wt. WPC validates the model presented with a reasonably good agreement. Since the agreement for the 70% wt. is less justified and such a material displays a marked yield stress, we can conclude that it is the yield stress that is probably the single issue that makes the present model questionable.
In this regard, a future work that we propose is to modify the model by selecting a Carreau-Yasuda model with an yield stress to account for the increase in the viscosity at low shear rates
17
Klug, Jeremy Hager. "High-performance adhesive systems for polymer composite bonding applications /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9883.
Full text
18
Liu, Jing. "Carbon nanotube/polymer composites and novel micro- and nano-structured electrospun polymer materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22673.
Full textAbstract:
Thesis (Ph. D.)--Textile and Fiber Engineering, Georgia Institute of Technology, 2007.Committee Chair: Kumar, Satish; Committee Member: Carr, Wallace; Committee Member: Graham, Samuel; Committee Member: Griffin, Anselm; Committee Member: Yao, Donggang.
19
Basson, Nicolaas Christiaan. "The effect of molecular composition on the properties of polyolefin-wood composites." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80222.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Polymer composites, and in particular wood-polymer composites have become commercially and environmentally important materials. Studies in polyolefin-wood composites have mostly focused on polypropylene (PP) and polyethylene (PE). To our knowledge, no study has been undertaken on advancing impact polypropylene copolymer (IPPC)-wood composites as a suitable alternative to using PP and PE. IPPC have proven to be a suitable alternative to PP at low temperatures to improve impact resistance for manufactured polymer products, and could be a great addition to improved properties for wood polymer composites. This study shows that the physical properties of IPPC-wood composites can be markedly improved when compatibilizer(s) are used to improve the distribution of the wood within the matrix, as well as improving the interaction between the wood and the polymer matrix.. The use of different compatibilizers, vi polypropylene-graft-maleic anhydride (PPgMA) and poly(ethylene-co-vinyl alcohol) (EvOH) results in different physical properties. Using simple admixtures of the PPgMA and EvOH in IPPC-wood composites result in a large spread of results, while pre-reacting the PPgMA and EvOH to form a joint compatibilizer gives reproducible results w.r.t the physical testing. A study of the fundamental interactions of the compatibilizer(s) with the molecular components of the IPPCs was undertaken. The IPPCs used were fractionated by preparative temperature rising elution fractionation, and the fractions were mixed with the compatibilizers. To this end, fluorescence microscopy was utilized to study the interaction. The results clearly indicate that the interaction of the PPgMA with the fractions differ from that of the EvOH. These differences can be explained in terms of the chemical composition distribution within the IPPC fractions. Atomic force microscopy (AFM) was used to study adhesive forces between compatibilizer, polymer and cellulose and lignin. Successful coating of AFM tips with PPgMA and EvOH was achieved. Whilst interactions based on chemical force microscopy (CFM) could not be quantified, the AFM results in conjunction with fluorescence spectroscopy provided meaningful insight in the way that compatibilizers interact with both the wood and the impact copolymers used in this study.
AFRIKAANSE OPSOMMING: Polimeer saamgestelde material, en meer spesifiek hout-polimeer saamgestelde material het die afgelope tyd belangrike produkte geword, beide kommersieel en in verband met omgewingvriendelikheid. Navorsing op die gebied van poli(olefien)-hout komposiete het tot op hede meestal gefokus op die grbruik van poli(propileen) (PP) en poli(etileen) (PE). Sover dit on kennis strek is daar nog geen studie gedoen om die gebied van impak polipropileen kopolimere (IPPK)-hout komposiete uit te bou nie. IPPKs is ‘n geskikte alternatief vir PP in veral laetemperatuur aanwendings. Die gebruik van IPPKs as matriks vir die hout komposiete kan ‘n groot staqp vorentoe beteken. Hierdie studie wys dat die fisiese eienskappe van iPPK-hout komposiete merkwaardig verbeter kan word waneer versoeningmateriale gebruik word om die verspreiding van die hout in die polimeermatriks sowel as die interaksie tussen die hout en polimeer te verbeter. Die gebruik van verskillende versoenings material, t.w poli(propileen-ent-maleinsuur anhidried) (PPeMA) en pol(etlieen-ko-viniel alkohol) (EVOH). Deur gebruik te maak van eenvoudige mengsels van PPeMA en EVOH in IPPK-hout composite het ‘n geweldige wye verpreiding van resultate tot gevolg gehad, terwyl ‘n voorafgaande reaksie tussen die PPeMA en die EVOH om ‘n saamgestelde versoeningmateriaal te maak tot gevolg gehad het dat reproduseerbare resultate verkry kon word. ‘n Studie van die fundamentele interaksies van die versoeningsmateriale met die molkulêre komponente van die IPPKs is uitgevoer. Die IPPKs is gefraksioneer deur preparatiewe temperatuur-stygende uitloog frakasionering en die fraksies is gemeng met die versoeningmateriale. Fluoressensie mikroskopie is gebruik om hierdie interaksies te bestudeer. Die resultate dui duidelik daarop dat die interaksie van die PPeMA met die fraksies verskil met die van die EVOH. Die verskille kan verduidelik word aan die hand van die chemiese samestelling verspreiding van die IPPK fraksies. Atoomkrag mikroskopie (AKM) is gebruik om die adhesive-kragte tussen die versoeningmateriale, polimere, sellulose en lignien. AKM tippe is suksesvol bedek met PPeMA en EVOH, onderskeidelik. Alhoewel interaksies gebaseer op chemiese krag mikroskopie (CKM) nie gekwantifiseer kon word nie, lewer hierdie resultate tesame met die fluoressensie spektroskopie unieke insig in die manier wat versoeningmateriale met beide die hout en die polimeer reageer.
20
Batra, Saurabh. "Creep rupture and life prediction of polymer composites." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10381.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains xix, 195 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 193-195).
21
Le, Guilly Marie O. "Development of ionic polymer actuator arrays /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/7078.
Full text
22
Chakraborty, S. "Structural, dynamical properties of polymers and polymer composites from multiscale simulations." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2016. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2072.
Full text
23
Kuriakose, Maju. "Thermal investigations on polymer dispersed liquid crystal composites and thermo-electric polymer composites using photothermal techniques." Phd thesis, Université du Littoral Côte d'Opale, 2013. http://tel.archives-ouvertes.fr/tel-00982712.
Full textAbstract:
Primarily, newly developed, high sensitive and accurate methods for thermal characterization of liquids using photothermal radiometry are presented. Two experimental configurations are suggested, tested and validated with usual liquid materials. These methods are used to study polymer dispersed liquid crystal samples. Dynamic thermal properties of samples are analysed verses amplitude varying applied electric field with constant frequency as well as versus frequency varying electric field with constant amplitude. Our results clearly show the thermal properties of the samples are prone to depolarizing field effects at the lower frequencies of the applied electric field. The experimental results are modeled against existing theories to predict electric properties of the sample composites. Second part of the manuscript describes the development of a novel photothermal technique based on thermoelectric effect. This technique is particularly useful for thermally characterizing thermoelectric materials without using a separate sensor for measuring induced temperature changes. A theoretical and experimental study is presented. The experiments are done on polyaniline - carbon nanotube composite pellets by measuring Seebeck voltage generated by the samples upon heating by a modulated laser beam. Additional infrared radiometry experiments are done on the same samples and the results are in good agreement with those previously found. Later on, the possibility of photothermoelectric materials to be used as sensors for finding thermal transport properties of materials with a thermal wave resonant cavity is suggested.
24
Such, Georgina School of Chemical Engineering & Industrial Chemistry UNSW. "The investigation of novel polymer-photochromic conjugates." Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/32750.
Full textAbstract:
My research has focussed on the development of a technique to tailor photochromic switching rates by creating a customised local environment for the dye within an otherwise rigid host matrix. Living radical polymerisation offers the potential to design such a system. A living radical initiator based on a spirooxazine compound was used to polymerise a polymer chain of well controlled molecular weight and polydispersity. This technique facilitated the construction of a conjugate with every photochromic moiety convalently attached to a polymer chain with uniform characteristics. The photochromic behaviour of these new polymer-spirooxazine conjugates were investigated in a cross-linked polymer matrix with a Tg of approximately 120??C. It is well known that photochromic switching is susceptible to local environment effects such as rigidity, free volume and polarity.1, 2 The goal of these systems was to create a uniform local environment which would facilitate controlled changes in the photochromic switching rates. The photophysical investigation of these systems demonstrated the success of this technique. The photochromic rates were directly related to the characteristics of the polymer conjugate. It was postulated the conjugates acted as a customised local environment for the photochromic moiety, encapsulating it from the host matrix. Consequently systematic tailoring of the photochromic switching rates was achieved by changes in the characteristics of the attached polymer. To our knowledge this is the first technique to control local environment of a photochromic compound and thus the first example of systematic tuning of photochromic switching rates. Throughout this research, several characteristics of the attached polymer were modified to give a series of rules for the tuning of photochromic switching rates using this technique. The largest variation in switching speed is achieved through variation of Tg. A range of photochromic rates from extremely slow to near solution-like can be easily achieved. The necessary variations in Tg can be achieved easily using living radical polymerisation techniques. The use of different homopolymers, block and random copolymers were all demonstrated successfully in this work. For finer tuning of the photochromic rates, changes in chain length can be used. It was also found the best living radical polymerisation method for this work was ATRP due to the bulky or incompatible halogen which contributed to efficient encapsulation. However this endgroup effect is only important in systems which do not have a low Tg component. The incorporation of such a component overrides all other contributions to the overall behaviour.
25
Tahhan, May. "Carbon nanotubes and conducting polymer composites." Intelligent Polymers Research Institute - Faculty of Science, 2004. http://ro.uow.edu.au/theses/407.
Full textAbstract:
A nanocomposite is defined as a material of more than one solid phase, where at least one dimension falls in the nanometer range. The combination of carbon nanotubes (CNT) and conducting polymers offers an attractive route for the production of novel compounds that can be used in a variety of application such as sensors, actuators, and molecular scale electronic devices. The ultimate goal of this work is to develop and investigate CNT composites that provide a structural functionality together with one or more other key functions. A variety of novel CNT dispersions were prepared using commercially available CNT systems such as Rice single-walled carbon nanotubes (RCNT), HiPco single-walled carbon nanotubes (HCNT), and Multi-walled carbon nanotube (MWCNT). This study explored the application of novel functional dispersing agents. Deoxyribose Nucleic Acid (DNA) a biological molecule, N- sopropylacrylamide 2-acrylamido-2-methyl-1-propanesulfonic acid (NIPPAm-AMPS) a polyelectrolyte, Didodecyldimethyl ammonium bromide (DDAB) a polymerizable compound, Poly(methoxyaniline-5-sulfonic acid) (PMAS) an inherently conducting polymer, and PVA an insulating polymer were some of the agents used to disperse the CNT. These dispersions were then evaluated in term of their stability and ability to effectively disperse the CNT. Solid-state CNT composites (mats) were then prepared by means of pressure filtration of the CNT/dispersant solutions. These mats were characterized using a variety of different techniques to determine their viability to be used as mechanical actuators or electrochemical devices. The characterization methods included cyclic voltammetry, conductivity, capacitance, atomic force microscopy, scanning electron microscopy, Young’s modulus, and actuation measurements. Abstract RCNT/conducting polymer composites were prepared by the electropolymerization of Pyrrole with a range of different dopant anions in the presence of different RCNT dispersions. In these composites, the RCNT were completely covered by the polymer, consequently the electrochemical responses of these composites were dominated by the electrochemistry of the polymers with the CNT functioning as a conductor element. Polypyrrole was also electropolymerized using functionalized multi-walled carbon nanotubes (FMWCNT) as dopant. Electropolymerization was carried out using galvanostatic and potentiostatic techniques on gold-coated Mylar and ITO-glass. It was determined that PPy/FMWCNT composites deposited on either electrode using potentiostatic deposition exhibited redox peaks. This redox behavior was not observed when the galvanostatic deposition was employed. HCNT/Polyaniline (PAn) composites were prepared by either casting a film from a solution of HCNT and PAn in 1,2-Dichlorobenzene, or by casting a film of PAn onto an existing HCNT mat. The latter exhibited the highest conductivity. The actuation behavior of these CNT composites was investigated and it was determined that the PAn component contributes to the actuation strain while the HCNT component contributes to Young’s modulus. The combination of the HCNT (with their mechanical properties) and PAn (with its actuator behavior) offers and attractive route not only to reinforce the polymer film but also to introduce new electronic properties based on morphological modifications or electronic interactions between the two components giving a robust blend of optimum properties. These results open the door for these composites to be used in a variety of applications that require a combination of the above characteristics such as mechanically reinforced actuator devices, robotics, optical fiber switches, prosthetic devices, and anti-vibration systems. In addition, PPy with a range of dopant anions was electrodeposited galvanostatically, potentiostatically, and potentiodynamically on the surface of four different carbon electrodes, RCNT mat (unannealed), RCNT mat (annealed), glassy carbon, and carbon foil. It was found that the method of electrodeposition was crucial to the electroactivity of the deposited polymers, particularly when deposited onto a RCNT mat due to the different interaction between the deposited polymer and the RCNT mat. Finally, HCNT/SDS, HCNT/PMAS, and HCNT/DNA fibers were prepared using the Particle Coagulating Spinning method (PCS). The annealing process resulted in a dramatic increase in conductivity of up to 2600 times higher compared to the unannealed fibers. However, the annealing process did not play any role in keeping the fibers together or modifying the alignment of the carbon nanotubes ropes within the fibers. The HCNT/DNA fibers, with their biocompatibility, high conductivity, and good mechanical properties can be used as artificial muscles, bioelectronic sensors, or even as platforms to support the growth of nerve cells. This thesis delineates the methods of successful production of solid sate CNT mats and fibers, utilizing traditional polymeric and more novel multi- functional dispersant materials. Thereby, providing a series of new framework for which future device structures can be fabricated.
26
Diccar, Unmesh Vilas Ahmed Ikramuddin. "Plasma spray coatings for polymer composites." Diss., A link to full text of this thesis in SOAR, 2006. http://soar.wichita.edu/dspace/handle/10057/643.
Full textAbstract:
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."December 2006." Title from PDF title page (viewed on Oct. 29, 2007). Thesis adviser: Ikramuddin Ahmed. Includes bibliographic references (leaves 68-71).
27
Liu, Qing. "Hydroxyapatite/polymer composites for bone replacement." Enschede : University of Twente [Host], 1997. http://doc.utwente.nl/586.
Full text
28
Bleach, Nicola Clare. "Optimisation of degradable bioactive polymer composites." Thesis, Queen Mary, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271820.
Full text
29
Robinson, I. M. "Optomechanics of polymer fibres and composites." Thesis, Queen Mary, University of London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339799.
Full text
30
Knowles, Jonathan Campbell. "Polymer glass composites for surgical implants." Thesis, Staffordshire University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292250.
Full text
31
Hu, Mingyang. "Designing polymer-tethered membrane-nanoparticle composites." Research Showcase @ CMU, 2013. http://repository.cmu.edu/dissertations/287.
Full textAbstract:
This thesis proposes a novel design of nanoparticles for drug delivery. By tethering a bilayer membrane vesicle to a solid nanoparticle core at its center using hydrophilic soft polymers, this structure is expected to exhibit improved stability, narrowed size distribution, and a variety of functionalization possibilities. Various aspects of this design will be examined from a theoretical perspective using physico-chemical knowledge and computer simulations. The aim is to significantly reduce the size of the fairly large parameter space and shed light on experimental protocols for how to effectively assemble such nanoparticles in the laboratory.
To study the properties of this design, coarse-grained molecular simulations are introduced in Chapter 2 as one of the major tools employed in this work, thanks to their computational efficiency and the possibility of obtaining important generic insights of the system being modeled. The general philosophy of coarse-graining (CGing) will be outlined, followed by an introduction to the CG models used in this work. Then, it will be illustrated how to connect length, energy, and time scales in CG simulations to reality. This chapter is concluded by applying the CG concepts and techniques described earlier on to obtain a CG model for PEGylated linker molecules, which is one of the two major components of the system of polymer-tethered nanocomposites studied in this work.
After the second chapter on coarse-graining, this thesis will spend three chapters focusing on either one of the two major components of the system we proposed, namely the polymeric linkers and the lipid bilayers. In Chapter 3, to understand the mechanical properties of the polymer linkers which tether the membrane vesicle to the nanoparticle core, a theoretical model for polymer brushes confined by two concentric spheres will be derived based on single-chain theories and scaling concepts. Using the CG linker model parameterized in Chapter 2, it will be demonstrated that this theoretical polymer model quantitatively predicts the force-extension relation of the polymers. This provides an efficient way to estimate both the size distribution and the stability of the tethered membrane-nanoparticle composites.
Following the chapter on polymers, this thesis will proceed to investigate the other major component in the proposed nanocomposites, namely the lipid membrane. Hence, computational methods to determine the two curvature elastic moduli in Helfrich theory, namely the bending modulus and the Gaussian curvature modulus, will be elaborated upon in the next two chapters. To be more specific, a method to measure the bending modulus by simulating membrane buckles will be proposed and validated in Chapter 4. Compared to other existed ways for measuring the bending modulus, the buckling method will turn out to be computationally efficient, and it can be applied to almost all types of membrane models.
In Chapter 5, a novel method for determining the Gaussian curvature modulus in simulations will be developed. The interplay between the bending energy and the edge tension in the membrane vesiculation process provides an efficient and robust way to pinpoint the Gaussian curvature modulus. As a comparison, another time-honored method to determine this modulus by measuring the lateral stress profile of flat bilayers is discussed. Based on the results measured in this alternative technique, as well as a comparison with the vesiculation protocol, it is argued that the stress profile method in fact fails to produce trustworthy values for the Gaussian curvature modulus. This unexpected result suggests caution when attempting to extract bilayer properties from the stress profile.
The models and knowledge which have been developed in this thesis will then be linked together in Chapter 6. The study of planar polymer-tethered bilayer membranes in this chapter serves as an intermediate step towards the membrane-nanoparticle composites in a spherical geometry. Simulations of the assembly process of tethered bilayers mimicking the rapid solvent exchange and the vesicle fusion protocols are qualitatively consistent with experimental observations found in the literature, supporting the reliability of our CG model. Moreover, the polymer theories discussed in Chapter 3 prove sufficient in semi-quantitatively describing the structural properties of such tethered membranes.
Bringing everything together, this thesis concludes with a study of the polymertethered membrane-nanoparticle composites proposed in Chapter 1. Theoretical constraints on the design parameters of this structure are first outlined and tested in simulations, with a major focus on the plausible range of the nanocomposite size. Then, a number of practical aspects regarding such nanocomposites, including their assembly process, solvent conditions, and the effect of the polydispersity in the linker chain lengths, are investigated.
32
Gardham, Louise Marie. "Dynamic mechanical properties of polymer composites." Thesis, University of Leeds, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395322.
Full text
33
Hugo, Annie-May. "Recycled polymer composites for structural applications." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/9520/.
Full textAbstract:
This thesis documents the development and testing of recycled, immiscible polymer blends for structural applications. The project was a Knowledge Transfer Partnership co-funded by Innovate UK and a Plastic Lumber manufacturer, who had a development contract with Network Rail. Network Rail contributed towards a permanent fatigue testing facility for full-size sleepers. Recycled plastic lumber converts lower grade, recyclate waste streams into products for decking, fencing, etc. The aim was to create formulations capable of carrying significant in-service, dynamic loads over a wide spectrum of outdoor temperatures and conditions with 50 years minimum service life for railway sleepers. Mixed polyethylene/polypropylene recyclates were tested in iterative laboratory trials reinforced with polystyrene, mineral fillers and glass fibre. Flexural properties and impact resistance amongst other tests aided formulation design for production trials. A synergistic reinforcing effect was found between glass fibre and mica within an immiscible recycled polymer blend. Polymer blends and fibre reinforced grades were manufactured by intrusion moulding into profiles up to 2800x250x130 mm. Profiles of four trial and two production grades were tested in flexure, compression and thermal expansion. Large statistical sample sizes were required due to waste stream batch-to-batch variability. Strength and modulus were found to change with manufacturing technique, profile size, profile orientation, test type, and test parameters. Strengths were good, though lower than predicted due to premature failure. The fracture process was found to initiate at inclusions, ductile crack growth continued to a critical size followed by brittle facture. Glass fibre significantly improved strength, modulus, maximum operating temperature and thermal expansion. In 2012, two major product approvals were attained after extensive qualification testing that included fatigue testing equivalent to 20 years in service. British Board of Agrément accredited a crib earth retaining wall system. Network Rail approved for track trial sleepers made from the glass fibre reinforced grade.
34
Medeiros, Araujo Thiago. "Single Polymer Micro- and Nano- Composites." Doctoral thesis, University of Trento, 2013. http://eprints-phd.biblio.unitn.it/972/1/Medeiros_Thesis_Final_Revised_Version.pdf.
Full textAbstract:
Due to an increasing attention to environment preservation and the need to accomplish new regulations, a general interest to improve the recyclability of composite materials has recently emerged. In order to fulfill this new requirements, a possible strategy could be represented by the development of so-called "single polymer composites" (SPCs), i.e. composite materials in which both matrix and reinforcement have the same chemical composition. The main advantage of SPCs is that, unlike traditional heterogeneous composites (such as glass- or carbon reinforced polymer composites), they can be entirely melted down at the end of the product life for recycling.
After an optimization of the annealing treatment to improve the mechanical properties and thermal stability of the reinforcing phase, SPCs containing Vectran® micro- and nano- fibers as a reinforcement were prepared, and their thermo-mechanical properties and recyclability were investigated using a multidisciplinary approach.
Single polymer micro composites (SPMCs) containing up to 30 wt% of reinforcing microfibers showed a outstanding improvement of tensile modulus (up to 160 %) compared with the unfilled matrix. FESEM observations evidenced some pull-out phenomena, indicating a poor interfacial adhesion. After a surface treatment on the reinforcement, a composite containing up to 20 wt% showed a remarkable improvement of almost 180% in the tensile modulus compared with the unfilled matrix. FTIR and thermal analysis evidenced its recyclability.
Single polymer nano composites (SPNCs) containing up to 10 vol% of reinforcing nanofibers showed an increase by almost 20% of their tensile modulus and strength in comparison with the unfilled matrix. Optical observations revealed a consolidation problem in the unfilled matrix due to the adapted film-stacking process used. However, the addition of the nanofibers in the composite eliminated the problem. Thermal analysis was used to ensure the SPNCs recyclability.
Vectran® single polymer micro- and nano- composites have been proven to be possible candidates to substitute traditional heterogeneous composites materials, with enhanced recyclability features.
35
Li, Wei. "Composite polymer/graphite/oxide electrode systems for supercapacitors." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439309266.
Full text
36
Johnson, Jack Royce III. "POLYMER BLENDS, COMPOSITES AND AEROGEL MODIFICATION BY INNOVATIVE APPROACHES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1317409667.
Full text
37
Zhang, Xiefei. "Studies on Single Wall Carbon Nanotube and Polymer Composite Films and Fibers." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7610.
Full textAbstract:
Single wall carbon nanotubes (SWNT) have been extensively studied over the last decade due to their excellent comprehensive properties for a variety of applications. This study is focused on the applications of SWNTs as reinforcement for polymer matrices. Due to van der Waal interactions, SWNTs form bundles of about 30 nm diameters. In order to take full advantage of the SWNT mechanical properties, SWNT must exfoliate or at least disperse in small diameter bundle size. Optical microscopy and SEM only give qualitative information of dispersion. Quantitative characterization through TEM or AFM can be time consuming in order to get statistical result. In this study, simple method is developed to quantitatively estimate the size of SWNT bundle in dispersion based on the geometry controlled electrical percolation behavior. The SWNTs can be dispersed /exfoliated via PVP wrapped SWNT aqueous dispersion assisted by surfactants such as sodium dodycel sulfate. PVA / SWNT composite films prepared through PVP wrapped SWNTs exhibit improved mechanical properties as well as the evidence of load transfer from the polymer matrix to the SWNT as monitored by the Raman spectroscopy. SWNT can also be well dispersed into PVA/DMSO/H2O solution. Gel spinning of PVA/SWNT composite fiber has been successfully carried out with improved mechanical properties. Functionalized tubes can be used to enhance SWNT dispersion and exfoliation. Oxidation in strong acids is one method used for functionalizing nanotubes. SWNTs have been functionalized in nitric acid. The structure and properties of films (buckypaper) processed from nitric acid functionalized tubes have been studied exhibiting high tensile strength and high electrical conductivity. Nitric acid treatment results in selective degradation of the small diameter tubes.
38
Olea, Mejia Oscar Fernando. "Micro and nano composites composed of a polymer matrix and a metal disperse phase." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5135/.
Full textAbstract:
Low density polyethylene (LDPE) and Hytrel (a thermoplastic elastomer) were used as polymeric matrices in polymer + metal composites. The concentration of micrometric (Al, Ag and Ni) as well as nanometric particles (Al and Ag) was varied from 0 to 10 %. Composites were prepared by blending followed by injection molding. The resulting samples were analyzed by scanning electron microscopy (SEM) and focused ion beam (FIB) in order to determine their microstructure. Certain mechanical properties of the composites were also determined. Static and dynamic friction was measured. The scratch resistance of the specimens was determined. A study of the wear mechanisms in the samples was performed. The Al micro- and nanoparticles as well as Ni microparticles are well dispersed throughout the material while Ag micro and nanoparticles tend to form agglomerates. Generally the presence of microcomposites affects negatively the mechanical properties. For the nanoparticles, composites with a higher elastic modulus than that of the neat materials are achievable. For both micro- and nanocomposites it is feasible to lower the friction values with respective to the neat polymers. The addition of metal particles to polymers also improves the scratch resistance of the composites, particularly so for microcomposites. The inclusion of Ag and Ni particles causes an increase in the wear loss volume while Al can reduce the wear for both polymeric matrices.
39
Kanelidis, Ioannis [Verfasser]. "Polymer-Nanocrystal Composites: Copolymers, Polymeric Particles and Hybrid Systems / Ioannis Kanelidis." Wuppertal : Universitätsbibliothek Wuppertal, 2012. http://d-nb.info/1022590464/34.
Full text
40
Hajatdoost, Sohail. "Vibrational spectroscopy studies of interdiffusion in polymer laminates and diffusion of water into polymer membranes." Thesis, Sheffield Hallam University, 1996. http://shura.shu.ac.uk/19741/.
Full textAbstract:
Confocal Raman microspectroscopy has been used to study the interdiffusion in polymer laminates at the interfacial region between the constituent polymer layers. The effects of the polymer molecular weight, annealing temperature, and annealing time have been studied. Three different laminates with various PMMA molecular weights have been examined, with a view to studying the hydrogen bonding interaction between the alcohol and ester groups of PVOH and PMMA layers. It has been found that v(C=O) band shows no apparent frequency shift due to hydrogen bonding. However, considerable broadening of the v(C=O) band has been observed at the interfacial region. In order to study the effect of annealing temperature, a PAN/PVOH laminate has been chosen. It has been shown that the degree of hydrogen bonding is reduced if the polymer laminate is annealed at a higher temperature than the glass transition temperature of both of the constituent polymers. No significant change has been observed after annealing the laminate for various lengths of time. It has been shown that Raman imaging and Raman microscopy can provide invaluable information about the molecular distribution and chemical interactions of various phases in polymer blends. The diffusion of pure water and also water from some ionic solutions into sulphonated polyetherethersulphone/polyethersulphone, SPEES/PES has been studied using Fourier transform infrared-attenuated total reflectance, FTIR-ATR spectroscopy. The effects of sulphonation level, annealing temperature, ionic concentration, and presence of some ionic species on diffusion of water into SPEES/PES has been examined. In addition the sorption and desorption processes, and diffusion into a laminate of SPEES/PES-PVOH has also been studied. It was found that the above diffusion processes are not Fickian nor Case II and is best described by a dual-mode sorption model. The diffusion coefficient for H2O in various cationic solutions into SPEES/PES has a descending order of Li[+] > Cs[+] > Na[+] > K[+]. Increasing the ionic concentration results in a decrease in the water diffusion coefficient. It was found that an increase in annealing temperature caused the diffusion curve to become more sigmoidal in shape with a decreases in diffusion coefficient.
41
Liang, Ya Palmese Giuseppe R. Lowman Anthony M. "Functional polymer-polymer composites by nano/meso-fiber encapsulation : applications in drug delivery systems and polymer toughening /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3316.
Full text
42
BHARGAVA, SUMEET. "TEMPERATURE AND GAS SENSING CHARACTERISTICS OF GRAPHITE/POLYMER (PEO) BASED COMPOSITE STRUCTURES." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1152821559.
Full text
43
Kelnar, I. "Polymer-polymer Microfibrillar Composites: Effect of Nanofillers on Structure and Properties." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35451.
Full textAbstract:
Microfibrillar composites (MFCs) are advantageous polymer-polymer composites with in situ formed reinforcing fibrils. The range of applications of MFCs is limited by their low thermal resistance and me-chanical parameters of polymeric microfibres, which are formed by melt or cold drawing of the polymer blend. This study addresses improving MFCs based on HDPE matrix with 20% polyamide 6 microfibrils using organophilized montmorillonite. The complex effect of the nanofiller on the structure and parameters of the MFCs is investigated.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35451
44
Zhou, Jian. "Study of Anchoring Behavior of Nematic Fluids at The Interface of Polymer-Dispersed Liquid Crystals." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5121.
Full textAbstract:
A liquid crystal (LC) at its boundary surface adopts a preferential alignment, which is referred to as anchoring. The direction of this alignment (i.e., anchoring direction) may be perpendicular, parallel or tilted with respect to the surface. Transitions from one anchoring condition to another may occur when the parameters (e.g., temperature) charactering the surface change, as referred to as anchoring transitions. In the LC-polymer composite systems under our study, the anchoring and temperature- driven anchoring transitions of nematic fluids is very sensitive to the structure of the side chain of poly (alkyl acrylate) matrixes that encapsulate the LC. We have shown that the anchoring transition temperature of these systems can be tuned far below the nematic-to-isotropic transition temperature, by varying either the length, branching structure of the side chains of homopolymers, or the composition of copolymer of two dissimilar monomers. Both sharp and broad anchoring transitions with respect to the temperature range over which a transition occurs were observed. It is postulated that microscopic interactions between the polymer side chains and LC molecules play an important role in determining the anchoring. In particular, the conformation of the polymer side chain is proposed to have important control over the anchoring. Anchoring strength and tilt angle as a function of temperature during the anchoring transitions were also experimentally investigated, which contribute to understanding of the microscopic mechanism for such transitions.
Based on the LC-polymer composites with controlled anchoring, a LC display with reverse switching mode and a novel electrically switchable diffraction grating have been demonstrated. The advantages of these devices are ease of manufacturing, low operation voltage, and mechanical stability offered by polymer matrix.
Moreover, a detailed study of the director configuration of wall defects found in these composite films was carried out using fluorescence confocal polarized microscopy.
45
Prystaj, Laurissa Alia. "Effect of carbon filler characteristics on the electrical properties of conductive polymer composites possessing segregated network microstructures." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31667.
Full textAbstract:
Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.Committee Chair: Rosario Gerhardt; Committee Member: Gleb Yushin; Committee Member: Hamid Garmestani. Part of the SMARTech Electronic Thesis and Dissertation Collection.
46
Wright, Richard J. "Bolt bearing creep behavior of highly loaded polymer matrix composites at elevated temperatures." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17362.
Full text
47
Ren, Xianjie ren. "Improving sustainability of rubber composites with renewable additives and epoxidized guayule natural rubber." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574440536318129.
Full text
48
Winchester, Stuart. "Composite modification by preformed polymer particles." Thesis, University of Surrey, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267411.
Full text
49
Annapragada, Sriram Kiran. "Mechanism of Foaming on Polymer-Paperboard Composites." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19790.
Full textAbstract:
This thesis addresses a new technique of foaming on polymer-paperboard composites which combines the advantages of traditional polymeric foam with the environmental benefits of paperboard. Paperboard is sandwiched between two extruded polymeric layers of different densities. On application of heat, one face is foamed by the evaporating moisture in the board; the other face serves as a barrier. This work is directed at gaining a better understanding of the fundamental processes in foaming polymers on paperboard. The ultimate goal is to be able to produce uniform bubbles of a predetermined size on the surface so as to give optimum heat insulation and good tactile properties. Bubble growth was studied as a function of paperboard properties, polymer melt index, extrusion speed, polymer thickness, temperature and moisture content. The foam quality (thickness) is also related to the cell size distribution and various factors affecting it are identified. A combination of experimental techniques such as high speed imaging, infrared thermography and scanning electron microscopy is used for this purpose. Foaming on paper-polymer composites is caused by water vapor escaping through the pores present in the paperboard substrate and then foaming the polymer. The vapor driving force which dominates foaming and overcomes the less significant viscoelastic and surface tension opposition forces depends on the paperboard properties as well as on the ability of the polymer to bond with the paperboard. It was found that the bubble size distribution directly relates to the pore size distribution on the paperboard. The bubble size was also controlled by the thickness of the polymer layer and its ability to bond with the paperboard. Coalescence subsequently led to thicker foams due to the formation of larger sized bubbles.
50
Oka, Mihir Anil. "PLA and cellulose based degradable polymer composites." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33829.
Full textAbstract:
We studied PLA-microcrystalline cellulose composites, focusing on the effects of processing, particle size and surface modification. The thermal and mechanical properties of these PLA based composites were studied and the effect of cellulose addition on PLA degradation was analyzed. For our system, the degradation rate was found to depend on initial sample crystallinity, pH of the degradation media and cellulose content of the composite. Composites were prepared using solution processing and melt mixing methods. The processing methods influenced the polymer's ability to crystallize affecting the mechanical properties. Isothermal crystallization studies carried out to study the kinetics of crystallization showed melt processed samples to have lower half time for crystallization and higher value for the Avrami exponent. The crystallization rate of PLA was also found to depend on surface chemical composition of cellulose particles and the particle size. Influence of filler surface modification on the composite properties was studied via grafting of lactic acid and polylactic acid to cellulose particles and the effect of filler size was studied using hydrolyzed microcrystalline cellulose particles. A simple esterification reaction that required no external catalyst was used for surface modification of cellulose particles. Surface modification of cellulose particles enhanced the static and dynamic mechanical properties of the composite samples due to improvement in the PLA-cellulose compatibility that resulted in better interfacial interactions. The utility of cellulose, available from a renewable resource, as an effective reinforcement for PLA is demonstrated.