Dissertations / Theses: 'Polypropylene'

1

Tang, Eunice Wai Chong. "Preparation and characterization of polypropylene-polypropylene (PP-PP) composites /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?MECH%202003%20TANG.

Full text

Abstract:

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 91-95). Also available in electronic version. Access restricted to campus users.

APA, Harvard, Vancouver, ISO, and other styles

2

Slánská, Petra. "Aplikace termochromních látek v polymerních materiálech." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216383.

Full text

Abstract:

V textilním průmyslu je v dnešní době veliká konkurence. Každá novinka může znamenat velký zisk. Tato diplomová práce se bude zabývat aplikací termochromních přísad (látka reagující na teplotu změnou své barvy) do polymerní matrice, konkrétně polypropylenu, a jeho další zpracování u výrobce technického polotovaru - výroba vláken. Po výrobě vzorků bude provedeno jejich testování. Porovnají se vlastnosti polypropylenu s a bez termochromních přísad a zhodnotí se, nakolik tyto přísady ovlivňují vlastnosti polypropylenu. Ze získaných výsledků se stanoví možnost využití termochromních přísad v textilním průmyslu.

APA, Harvard, Vancouver, ISO, and other styles

3

Wang, Shi-Wei. "Controlling the structure and properties of toughened and reinforced isotactic polypropylene." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0231/document.

Full text

Abstract:

En tant que polymère de grande diffusion, les applications du polypropylène isotactique (PP) sont limitées par sa faible resistance au choc. D'après la relation structure - propriétés, sa résistance au choc peut être améliorée en contrôlant sa structure. Dans ces travaux, différents types d'agents nucléants ont été utilsés pour promouvoir la formation des cristaux de type bêta et de mélanges de deux PP de masses molaires différentes. Les propriétés mécaniques, le comportement à la rupture, et la morphologie cristalline ont été étudiés. Les influences du type et de la teneur en peroxyde et agent nucléant sur la morphologie cristalline et les propriétés mécaniques ont aussi été explorées. Un agent nucléant suporté sur des nanotubes de carbone multi-parois (MWCNT) a été utilisé pour modifier la structure cristalline du PP, ce qui a permis d'augumeter sa résistance au choc 7 fois comparée à celle du PP vierge et 3 fois comparée à celle du PP cristallisé en phase bêta. Cette importante augmentation en resistance au choc peut être attribuée à la formation des trans-cristaux de type bêta qui est favorisée par l?agent nucléant supporté sur les MWCNT
As a commodity polymer, the applications of isotactic polypropylene (PP) are limited by its low impact strength. Based on the structure-property relationship, its impact strength could be improved by controlling its structure. In this study, different kinds of nucleating agents were used to promote the formation of beta crystals of PP as well as mixtures of two PPs of different molar masses. The mechanical properties, fracture behaviour, and crystalline morphology were investigated. The effects of the type and content of the peroxide and nucleating agent on the crystalline structure and mechanical properties of the PP were also explored. A multi-walled carbon nanotude (MWCNT) supported nucleating agent was introduced to modify the crystalline structure of PP and the impact strength of the resulting PP was 7 times that of the pure PP and more than 3 times that of beta nucleated PP. The large increase in the impact strength was attributed to the formation of beta transcrystalline morphology which was promoted by the MWCT supported nucleating agent

APA, Harvard, Vancouver, ISO, and other styles

4

Wang, Xiaowei. "Adhesive bonding of polypropylene." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247559.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Işık, Kıvanç Tanoğlu Metin. "Layered silicate/polypropylene nanocomposites/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/makinamuh/T000532.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Cancelas, Sanz Aarón José. "High impact polypropylene : structure evolution and impact on reaction." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1210/document.

Full text

Abstract:

Les homopolymères à base de polypropylène isotactique (iPP en anglais) ont une rigidité plus élevée que le polyéthylène (PE), mais aussi une dureté limitée, en particulier à températures plus basses. Ceci peut être surmonté en incorporant un élastomère copolymère d'éthylène et de propylène directement dans la matrice semi-cristalline de iPP. De tels mélanges obtenus in situ dans des réacteurs successifs sont bien connus, et leur production nécessite un procédé multi-étapes. De façon succincte, un procédé industriel pour la synthèse de PP choc (hiPP, high impact PP en anglais) implique 2 zones de réaction (chaque zone peut être composée d'un ou plusieurs réacteurs). L’iPP est fabriqué dans la première zone. Les poudres encore actives sont ensuite dégazées et envoyées dans une seconde zone dans laquelle est incorporé un élastomère (généralement un copolymère de propylène et d'éthylène appelé caoutchouc éthylène-propylène (ethylene-propylene rubber (EPR) en anglais). L'homopolymère iPP peut être produit en phase gaz ou en suspension (slurry en anglais) dans un hydrocarbure, alors que l'EPR doit être fabriqué dans un réacteur en phase gaz. Dans la thèse actuelle, nous nous sommes concentrés sur les procédés intégralement en phase gaz. Par conséquent, la morphologie du polypropylène choc (hiPP) dépendra fortement de celle de l'iPP intermédiaire, qui, à son tour, dépendra de la morphologie du précatalyseur. Cependant, le même précatalyseur peut conduire à différentes morphologies d’iPP, selon le protocole d'injection suivi. L'injection de catalyseur est donc un aspect critique de la production du hiPP. Cet aspect a été étudié grâce à la réalisation d'un plan d'expériences de polymérisation du propylène. On a utilisé des catalyseurs supportés Ziegler-Natta (ZN), disponibles commercialement, dans un réacteur à cuve agitée et un réacteur phase gaz à flux stoppé. On a mis en évidence pourquoi la prépolymérisation et le mouillage du catalyseur par un hydrocarbure avant d'être introduits dans le réacteur assurent de hautes activités et un contrôle de la morphologie des particules de polymère tout en produisant l'iPP. Au cours de la production de l’hiPP, la thermodynamique de sorption de la phase gaz a un impact important sur la cinétique d'homopolymérisation et de copolymérisation du propylène. Par exemple, les hydrocarbures supérieurs améliorent la solubilité du propylène dans le polymère (phénomène de «co-solubilité») ce qui conduit à une augmentation de l'activité. De plus, la solubilité et la diffusivité des différents monomères (et de leurs mélanges) utilisés pour produire l’hiPP (propylène, éthylène et mélange éthylène / propylène) dans les poudres dépendent des températures et des pressions auxquelles le procédé est conduit. Les données expérimentales de ces quantités ont été obtenues et des modèles semi-empiriques généralement utilisés dans l'industrie des polyoléfines ont été utilisés pour comprendre leur dépendance à l'égard des conditions du procédé. Finalement, plusieurs poudres d’hiPP ont été obtenues dans le réacteur à cuve agitée avec un catalyseur ZN supporté, en suivant la voie intégrale phase gaz. La morphologie de la matrice iPP et les conditions de la copolymérisation telles que la quantité de copolymère, la température, la pression, la quantité relative d'éthylène par rapport au propylène et la présence d'hydrogène ont été systématiquement variées pour comprendre leur impact sur la répartition du caoutchouc dans la matrice PP. Ce facteur est, à son tour, crucial pour (1) un fonctionnement du procédé industriel optimal, et (2) les propriétés mécaniques recherchées de l'hiPP
Isotactic Polypropylene (iPP) homopolymers have higher stiffness than polyethylene (PE), but also limited toughness, especially at lower temperatures. This can be overcome by incorporating an elastomeric copolymer of ethylene and propylene directly in the semi crystalline iPP matrix. Such in situ reactor blends are well-known, and their production requires of multi-step reaction process. Very briefly, an industrial process for high impact polypropylene (hiPP) products involves 2 reaction zones (each zone can be composed of one or more reactors). iPP is made in the first zone, the still active powders are then degassed and sent to a second zone in which an elastomer (usually a copolymer of propylene and ethylene referred to as Ethylene-Propylene Rubber (EPR)) is made. The iPP homopolymer can be produced in the gas phase or slurry phase, whereas the EPR must be made in a gas phase reactor. In the current thesis, our focus was on an “all gas phase”process.Therefore, the morphology of hiPP will be greatly dependent on that of the intermediate iPP, which in turn, will depend on the precatalyst morphology. However, the same precatalyst can lead to different iPP morphologies, depending on the injection protocol followed. Therefore, catalyst injection is a critical aspect while producing hiPP. Such aspect has been studied by performance of a designed set of propylene polymerization reaction experiments. Commercially available supported Ziegler-Natta (ZN) catalysts along with a lab-scale stirred-bed reactor and a gas phase stopped flow reactor have been used. It is understood why prepolymerization and wetting the catalyst with hydrocarbon before being charged to the reactor ensure high activity and quality morphology while producing iPP. During the production of hiPP, sorption thermodynamics of the gas phase have a big impact on propylene homopolymerization and copolymerization kinetics. For instance, higher hydrocarbons enhance the propylene solubility in polymer (which is known as “cosolubility” phenomenon) which leads to an activity increase. In addition, the solubility and diffusivity of the different monomers used to produce hiPP (propylene, ethylene and ethylene/propylene mixtures) in the powders depend on the temperatures and pressures which the process is conducted at. Experimental data of these quantities was obtained and semi-empirical models generally used in the polyolefin industry were used to understand their dependence on the process conditions. Finally, several hiPP powders were made in the lab-scale stirred-bed reactor with a supported ZN catalyst, following the “all gas phase” route. The morphology of the iPP matrix and conditions during copolymerization such as amount of copolymer, temperature, pressure, relative amount of ethylene to propylene and the presence of hydrogen have been systematically varied to comprehend their impact on the rubber distribution among the PP matrix. The aforementioned factor is, in turn, crucial for (1) a correct industrial process operation, and (2) the mechanical properties sought-after in hiPP

APA, Harvard, Vancouver, ISO, and other styles

7

Yilmaz, Sule Seda. "Preparation And Characterization Of Organoclay-polypropylene Nanocomposites With Maleic Anhydride Grafted Polypropylene Compatibilizer." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613291/index.pdf.

Full text

Abstract:

The aim of this study was to improve the mechanical properties &ldquo
Moplen&rdquo
EP300L which is a heterophase copolymer. Polymer blends and nanocomposites were prepared by melt compounding method in a twin screw extruder. Nanofil®
5 (N5) and Nanofil®
8(N8) were used as the organoclays, and maleic anhydride grafted polypropylene (M) was used as the compatibilizer. The effects of additive concentrations and types of organoclays on the morphology, mechanical and thermal properties were investigated. Organoclay loading over 2 wt% prevented the intercalation mechanism resulting in large aggregates of clay, thus the material properties became poor even in the presence of compatibilizer. Compatibilizer addition improved the intercalation ability of the polymer, however a substantial increase in mechanical properties was not obtained up to 6 wt % loading of the compatibilizer. XRD analysis revealed that intercalated structures were formed with the addition of compatibilizer and organoclay. The nanocomposites that were prepared with N5 type organoclay showed delaminated structures at 6 wt % compatibilizer loading. v Nanofill ®
5 exhibited the highest improvements in mechanical properties, since the degree of organoclay dispersion was better in Nanofill ®
5 containing nanocomposites in comparison to Nanofill ®
8 containing ones. The DSC analysis indicated a insignificant reduction in the melting temperature of the ternary nanocomposites.

APA, Harvard, Vancouver, ISO, and other styles

8

Lepoutre, Priscilla. "The microstructure of polypropylene blends with ethylene vinyl alcohol copolymer and maleated polypropylene /." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61816.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Njoroge, Daniel [Verfasser]. "Thesis: Preparation and characterization of modified-graphene oxide/polypropylene nanocomposites : polypropylene nanocomposites / Daniel Njoroge." Berlin : epubli, 2016. http://www.epubli.de/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Köller, Frank. "Modifizierte Polypropylene durch Metallocen-Katalyse." [S.l. : s.n.], 1998. http://deposit.ddb.de/cgi-bin/dokserv?idn=961143738.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Can, Semra. "Characterization Of Serpentine Filled Polypropylene." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609434/index.pdf.

Full text

Abstract:

ABSTRACT CHARACTERIZATION OF SERPENTINE FILLED POLYPROPYLENE Can, Semra Ph.D., Department of Polymer Science and Technology Supervisor: Prof. Dr. Teoman Tinç
er March 2008, 158 pages In this study, the aim is to prepare polypropylene (PP)/serpentine composites and study their mechanical, thermal and morphological properties. Another objective is to explore whether it is possible to have PP/serpentine nanocomposites with melt intercalation method by using the advantage of the layer silicate structure of serpentine. The most widely used fillers in PP are talc and mica which belong to the phyllosilicates group of silicate minerals. So far, there has been almost no study employing serpentine as filler in either any polymers or PP, although it also belongs to the same group of minerals as talc and mica. Accordingly, it was planned to divide the work into the study of two groups. In group 1, for the compositions with 2, 5, 10 and 20 wt% serpentine, the particulate filler effects of serpentine both alone and in the presence of surface treatments with hydrochloric acid (HCl) and silane coupling agent (SCA) were investigated. The most impressive results in terms of static and dynamic mechanical properties were achieved with SCA rather than HCl. When the effect of serpentine without any treatment is considered, reinforcing effect of it can easily be observed without deteriorating the composite properties even at high filler loadings. In group 2, the nanofiller effects of serpentine in 2 and 5 wt% filled compositions by modification of both the filler and the matrix were aimed to be examined with melt intercalation method. In addition to HCl and SCA treatments, maleic anhydride grafted polypropylene (PP-g-MA) and quaternary ammonium salt (QAS) of cetyl-trimethyl-ammonium bromide were used as compatibilizer and intercalating agent, respectively. While the amount of QAS was kept constant, different percentages of compatibilizer were employed. The presence of QAS and PP-g-MA further improved the properties with respect to group 1 members. Interestingly, the percentage strain at break values did not decrease as much as group 1 compositions with the same filler content. It can be concluded that partial intercalation of group 2 compositions was achieved, according to the X-ray and TEM results. Keywords: Serpentine, PP/serpentine composites, SCA, PP-g-MA, serpentine nanocomposites

APA, Harvard, Vancouver, ISO, and other styles

12

Mizutani, T., E. Nakane, K. Kaneko, and M. Ishioka. "Space Charge Dynamics in Polypropylene." IEEE, 2004. http://hdl.handle.net/2237/7166.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Sura, Ravi Kishore. "Oriented crystallization of syndiotactic polypropylene." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/8293.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

GIROIS, STEPHANE. "Photooxydation du polypropylene : aspects cinetiques." Paris, ENSAM, 1995. http://www.theses.fr/1995ENAM0041.

Full text

Abstract:

Nous avons porte un nouveau regard sur la photooxydation du polypropylene homopolymere et d'un copolymere ethylene-propylene en utilisant des outils cinetiques pour decrire le mecanisme de photooxydation dans un but de prediction de duree de vie. La demarche consiste a identifier les produits d'oxydation formes par irtf en fonction de la duree d'exposition aux uv a differentes temperatures sous differentes intensites lumineuses, et se basant sur un mecanisme cinetique en boucle fermee, de proposer un modele qui caracterise la photoodegradation du materiau en fonction des conditions d'exposition. Le vieillissement photochimique de films minces ou l'oxydation n'est pas controlee par la diffusion de l'oxygene suggere un mecanisme efficace de coupure de chaine des le debut de l'exposition. La prise de masse des films dans la periode initiale caracterise une certaine homogeneite macroscopique de l'oxydation. Le caractere autoaccelere de l'accumulation des produits d'oxydation dans cette periode initiale et lineaire par la suite est compatible avec le schema cinetique en boucle fermee, c'est a dire une reaction en chaine dans laquelle la seule source de radicaux est la decomposition des hydroperoxydes par voie monomoleculaire. La vitesse elevee du processus de perte de masse ne peut etre expliquee que par un mecanisme de retroscission en cascade identique a une depolymerisation. L'etude de la photooxydation de pieces epaisses se traduit par la formation d'un profil d'oxydation dans une couche superficielle caracteristique d'un regime controle par la diffusion de l'oxygene. Les resultats suivent un comportement qui s'ecarte du modele theorique qui voudrait que l'epaisseur de la couche oxydee (eco) soit inversement proportionnelle a l'intensite. Nous avons attribue cette ecart a la microfissuration de surface qui permet a l'oxygene de penetrer dans les couches internes du materiau. Neanmoins, conformement au mecanisme cinetique en boucle fermee, eco varie peu avec l'intensite lumineuse. L'analyse par chromatographie d'exclusion sterique confirme la predominance d'un processus de coupure de chaine tres efficace qui s'accompagne neanmoins d'actes de reticulation en quantite significative. Le fait que la polymolecularite diminue avec l'oxydation est compatible avec l'hypothese d'un processus de coupure de chaine pseudo aleatoire a relative petite echelle

APA, Harvard, Vancouver, ISO, and other styles

15

Hoza, Adam. "Effect of Ethylene and Propylene on Performance of Ziegler - Natta Catalyst in Stopped - Flow Polymerization." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-320775.

Full text

Abstract:

Výzkum v této práci byl zaměřen na přípravu a charakterizaci blokových kopolymerů typu polypropylen-blok-poly(propylenu-co-ethylenu) (dále jen PP-blok-EPR). Tyto materiály jsou považovány za účinné kompatibilizátory mezi semi-krystalickou polypropylenovou (PP) matricí a amorfními doménami statistického kopolymeru propylenu a etylenu (EPR) v rázuvzdorném sekvenčním kopolymeru (ICP) a proto byl výzkum zaměřen na zkoumání vlivu přídavku blokového kopolymeru PP-blok-EPR na vlastnosti komerčního ICP. Blokové kopolymery byly připraveny za použití techniky „stopped-flow“. Pro tento účel byla zkonstruována vysokotlaká polymerační „stopped-flow“ aparatura, která umožňuje syntézu kopolymerů PP-blok-EPR za podmínek blízkých podmínkám v průmyslových reaktorech pro výrobu komerčních ICP materiálů. Aparatura umožňuje vyrábět PP-blok-EPR polymer v množství dostačující na jeho charakterizaci a následnou přípravu směsí s komerčním ICP. Velmi krátké polymerační časy (obvykle kolem 0.2 s) kterých bylo dosaženo v kapilárním reaktoru aparatury „stopped-flow“ zajišťuje, že aktivní centra Ziglorova-Nattova katalyzátoru produkují polymer řetězce skládající se z bloku semikrystalického polypropylenu a bloku amorfního EPR kopolymeru. Takovéto molekuly jsou v literatuře popsány jako „skutečné blokové kopolymery PP-blok-EPR“. Kopolymery syntetizované v aparatuře „stopped-flow“ byly frakcionovány preparativní TREF (Temperature Rising Elution Fractionation) metodou a získané frakce byly následně analyzovány pomocí DSC, 13C-NMR a GPC/SEC. Tyto analýzy odhalily přítomnost amorfního EPR ve vysoce krystalické frakci (100-140 °C). Toto zjištění potvrdilo, že významná část polymerních řetězců, připravených v aparatuře „stopped-flow“ jsou blokové kopolymery skládající se z bloku semikrystalického PP homopolymeru a bloku amorfního EPR kopolymeru v jednom polymerním řetězci. Kopolymery získané metodou „stopped-flow" byly v tavenině smíchány s komerčním rázuvdorným kopolymerem ICP. U takto připravených směsí byly vyhodnoceny mechanické vlastnosti, DTMA a reologické vlastnosti a výsledky byly srovnány s vlastmi původního komerčního ICP kopolymeru. Dále byly studovány rozdíly v morfologii a umístění EPR domén v matrici PP prostřednictvím SEM. Zřetelný vliv kopolymeru PP-blok-EPR na vlastnosti ICP byl pozorován zejména v morfologických změnách EPR domén dispergovaných v PP matrici. Tyto změny mají pozitivní vliv na rovnováhu mezi modulem v ohybu a rázovou pevností ICP materiálu. Vliv kopolymeru PP-blok-EPR na reologické vlastnosti ICP byl nevýznamný. Podobně také v případě DTMA nebyl pozorován významný vliv kopolymeru PP-blok-EPR na vlastnosti ICP.

APA, Harvard, Vancouver, ISO, and other styles

16

Pauvert, Olivier. "Stabilité de la vincristine dans les seringues en polypropylène." Paris 5, 1995. http://www.theses.fr/1995PA05P231.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Tam, Mei San. "Study of sisal fiber-reinforced polypropylene, polyethylene and polypropylene/polyethylene blend composites prepared by compression molding." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21175123a.pdf.

Full text

Abstract:

Thesis (M.Sc.)--City University of Hong Kong, 2005.
At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.

APA, Harvard, Vancouver, ISO, and other styles

18

Pedrazzoli, Diego. "Understanding the effect of nanofillers on the properties of polypropylene and glass fiber/polypropylene multiscale composites." Doctoral thesis, Università degli studi di Trento, 2014. https://hdl.handle.net/11572/368547.

Full text

Abstract:

In this study, polypropylene (PP) based nanocomposites were prepared by incorporating different kinds and amounts of silica nanoparticles and graphite nanoplatelets (GNP). The role of various percentages of compatibilizer polypropylene grafted with maleic anhydride (PPgMA) into PP nanocomposites was also investigated. In order to analyze the effect of the manufacturing process on the materialâ€™s properties, the samples were produced by (i) melt compounding and compression molding and (ii) extrusion and injection molding. It was found that injection molding provides significantly greater stiffness and strength compared to compression molding for all types of PP nanocomposites. Several characterization techniques were used in order to correlate the microstructure to the physical and mechanical properties of the materials. Both silica and GNP were found to be effective nucleating agents, significantly increasing the crystallization rate during isothermal crystallization and favoring the nucleation of the the Î²- phase, which manifests superior impact strength and toughness compared to the most common Î±-form crystals. Graphite nanoplatelets were found more efficient in inducing polymorphism and favoring the formation of a transcrystalline phase on the filler surface. A significant correlation between the tensile modulus, glass transition temperature and the amount of constrained phase, as assessed through tensile and DMA analyses, revealed the presence of a secondary reinforcing mechanisms, which, concurrently to the primary stiffening effect of the high modulus filler, contributes to the enhancement of the bulk properties. A complex constrained phase, responsible for providing a secondary reinforcing mechanism, was modeled as immobilized amorphous and transcrystalline regions located at the filler surface. The non-linear viscoelastic creep of the composites, successfully studied by the application of the time strain superposition principle (TSSP), showed a considerable enhancement of the creep stability in nanocomposites with respect to unfilled PP, especially for higher creep stresses. The study of creep dependance on the temperature showed that the stabilizing effect provided by the nanoparticles was more effective at high temperatures and, considering the time temperature superposition principle (TTSP), at long loading times. The equivalence between the time strain- and time temperature- superposition principle was substantiated by comparing the correspondent superimposed master curves. The nanofilled PP matrices have also been used for the preparation of microcomposites reinforced with short glass fibers (GF). Interfacial shear strength (ISS) was measured by means of the single fiber fragmentation test on various PP/GF microcomposites. Results show that the strength at the fiber/matrix interface can be remarkably increased when using nanocomposite systems, especially in the case of dimethyldichlorosilane-functionalized silica nanoparticles and GNP platelets, and that the improvement is further increased when the nanoparticles are used in combination with PPgMA. The thermodynamic fiber/matrix work of adhesion, estimated by contact angle measurements, showed a good correlation with the ISS values. Hybrid composites reinforced with short glass fibers and nanofillers were produced and characterized in order to investigate how the morphology and the mechanical properties of the composites were affected by the combined effect of two fillers of rather different size scales (i.e. micro- and nano- scale). The stronger fiber/matrix adhesion combined with the enhancement of the matrix properties resulted in superior tensile properties and impact resistance and improved viscoelastic behavior. As means of comparison, thermosetting hybrid composites based on epoxy resin were also produced by incorporation of GNP and short GF.

APA, Harvard, Vancouver, ISO, and other styles

19

Pedrazzoli, Diego. "Understanding the effect of nanofillers on the properties of polypropylene and glass fiber/polypropylene multiscale composites." Doctoral thesis, University of Trento, 2014. http://eprints-phd.biblio.unitn.it/1322/1/Thesis_PhD_Pedrazzoli_2014.pdf.

Full text

Abstract:

In this study, polypropylene (PP) based nanocomposites were prepared by incorporating different kinds and amounts of silica nanoparticles and graphite nanoplatelets (GNP). The role of various percentages of compatibilizer polypropylene grafted with maleic anhydride (PPgMA) into PP nanocomposites was also investigated. In order to analyze the effect of the manufacturing process on the material’s properties, the samples were produced by (i) melt compounding and compression molding and (ii) extrusion and injection molding. It was found that injection molding provides significantly greater stiffness and strength compared to compression molding for all types of PP nanocomposites. Several characterization techniques were used in order to correlate the microstructure to the physical and mechanical properties of the materials. Both silica and GNP were found to be effective nucleating agents, significantly increasing the crystallization rate during isothermal crystallization and favoring the nucleation of the the β- phase, which manifests superior impact strength and toughness compared to the most common α-form crystals. Graphite nanoplatelets were found more efficient in inducing polymorphism and favoring the formation of a transcrystalline phase on the filler surface. A significant correlation between the tensile modulus, glass transition temperature and the amount of constrained phase, as assessed through tensile and DMA analyses, revealed the presence of a secondary reinforcing mechanisms, which, concurrently to the primary stiffening effect of the high modulus filler, contributes to the enhancement of the bulk properties. A complex constrained phase, responsible for providing a secondary reinforcing mechanism, was modeled as immobilized amorphous and transcrystalline regions located at the filler surface. The non-linear viscoelastic creep of the composites, successfully studied by the application of the time strain superposition principle (TSSP), showed a considerable enhancement of the creep stability in nanocomposites with respect to unfilled PP, especially for higher creep stresses. The study of creep dependance on the temperature showed that the stabilizing effect provided by the nanoparticles was more effective at high temperatures and, considering the time temperature superposition principle (TTSP), at long loading times. The equivalence between the time strain- and time temperature- superposition principle was substantiated by comparing the correspondent superimposed master curves. The nanofilled PP matrices have also been used for the preparation of microcomposites reinforced with short glass fibers (GF). Interfacial shear strength (ISS) was measured by means of the single fiber fragmentation test on various PP/GF microcomposites. Results show that the strength at the fiber/matrix interface can be remarkably increased when using nanocomposite systems, especially in the case of dimethyldichlorosilane-functionalized silica nanoparticles and GNP platelets, and that the improvement is further increased when the nanoparticles are used in combination with PPgMA. The thermodynamic fiber/matrix work of adhesion, estimated by contact angle measurements, showed a good correlation with the ISS values. Hybrid composites reinforced with short glass fibers and nanofillers were produced and characterized in order to investigate how the morphology and the mechanical properties of the composites were affected by the combined effect of two fillers of rather different size scales (i.e. micro- and nano- scale). The stronger fiber/matrix adhesion combined with the enhancement of the matrix properties resulted in superior tensile properties and impact resistance and improved viscoelastic behavior. As means of comparison, thermosetting hybrid composites based on epoxy resin were also produced by incorporation of GNP and short GF.

APA, Harvard, Vancouver, ISO, and other styles

20

Psarreas, Alexandros. "Nitroxide-mediated controlled degradation of polypropylene." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2832.

Full text

Abstract:

Nitroxide-mediated Controlled Degradation of Polypropylene
Controlled-rheology polypropylene resins (CRPP) have been produced industrially for years using reactive extrusion processes employing peroxides as free radical initiators. The molecular weight characteristics of CRPP materials can be tailor-made depending on the final application in a very efficient and economic manner.

A PP-based nitroxide (NOR) with the trade name Irgatec CR76 has been recently developed by CIBA Chemicals, as a source of radicals and it is currently being evaluated for the production of CRPP. NORs are well-known as powerful stabilizers to protect plastics from the negative influence of light and heat, and easy in handling during processing. Preliminary experimental results exhibit a qualitative difference between Irgatec CR76 and other commonly used peroxides.

The purpose of this research work is to evaluate this new material as a potential replacement of commonly used peroxides in the production of CRPP. CRPP will be produced by reactive processing using varying amounts of Irgatec CR76 and the rheological properties of the materials produced will be investigated. By comparing results with Irgatec CR76 to those from other typical initiators, the effectiveness of Irgatec CR76 as an initiator will also be assessed.

The results of this research will have an impact not only on the potential extension of uses of the specific PP-based NOR (Irgatec CR76), but also, more generally, on the wider application of additives during degradation of PP. Potentially new materials can be produced with enhanced heat and light protection along with the other benefits inherent to standard CRPP.

APA, Harvard, Vancouver, ISO, and other styles

21

Derakhshandeh, Maziar. "Crystallization of polypropylene : experiments and modeling." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55605.

Full text

Abstract:

In this study, the quiescent crystallization of several polypropylenes (PPs) with different molecular characteristics was first examined using Differential Scanning Calorimetry (DSC) and Polarized Optical Microscopy (POM). The Avrami/Nakamura equation was employed to fit and predict crystallization kinetics under isothermal and non-isothermal conditions. The Avrami/Nakamura model was found to predict the non-isothermal crystallization data of the various PPs very well over a range of cooling rates. POM was used in line with a rotational rheometer to further examine the behaviour under quiescent condition at different temperatures and/or cooling rates. The growth rate of crystals was impeded exponentially with increase of temperature. To study the effect of flow on crystallization behaviour of PPs, the Anton Paar MCR-502 rotational rheometer equipped with various fixtures including parallel-plate and POM to induce shear flow was used. Generally, an increase in strain and strain rate or decrease of temperature is found to decrease the thermodynamic barrier for crystal formation and thus enhancing crystallization kinetics at temperatures between the melting and crystallization points. Popular models based on suspension theory, which are often used to relate the degree of crystallinity to normalized rheological functions are validated experimentally. It is found that the constant(s) of various suspension models should be dependent on the flow parameters in order for the suspension models to describe the effect of shear on FIC, particularly at higher shear rates. Finally, a capillary rheometer was used to investigate flow-induced crystallization (FIC) of various resins at high shear rates relevant to polymer processing. It is found that the crystallization kinetics are enhanced with increasing molecular weight indicating the importance of high-end tail of MWD on FIC. Various dies with different physics were used to investigate the effect of flow on FIC. The Cogswell analysis was applied on the capillary data to obtain the apparent extensional strain rate and strain as well as the apparent extensional viscosity. FIC was found to depend strongly on the L/D ratio of the capillary die. Finally, temperature impacted the FIC behaviour extensively since it alters the activation energy needed for the formation of macroscopic structures.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

APA, Harvard, Vancouver, ISO, and other styles

22

Wang, Xiao Chuan. "Branching of polypropylene through reactive extrusion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21396.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Laihonen, Sari J. "Polypropylene : Morphology, defects and electrical breakdown." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-268.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Wu, Xiang. "Quantitative infrared dichroism of isotactic polypropylene." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/9382.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Shindo, Nobuhiko. "Structural analysis of thick polypropylene moldings." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/10251.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Ahmed, Syed Iqbal. "Coloration of polypropylene : prospects and challenges." Thesis, Heriot-Watt University, 2006. http://hdl.handle.net/10399/2023.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Khan, Shahid Wahab. "Rheological properties of talc-filled polypropylene." Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/7567.

Full text

Abstract:

In this study polypropylene was modified by a range of talc (Mg3(OH)2Si4OlO) fillers. Three different types of surface modifiers were also used, two types of silanes (octyltriethoxysilane and y-aminopropyltriethoxysilane) and maleic anhydride modified polypropylene plus polyethylene wax as an external lubricant. A series of compounds were prepared in an APV twin screw compounder, based on talc addition level, morphology, particle size, surface coatings and coupling agents. The study showed that addition of talc to PP increases the shear viscosity and the blend system generally follows the power law in the shear rate range studied. The experimental values obtained with talc-filled PP were compared with theoretical data obtained from the Maron-Pierce type equation. It was found that theory predicts a higher value of relative viscosity for some talc fillers. A model equation is proposed for talc-filled PP that predicts accurately relative viscosity of the compound for different volume fractions of talc filler. PP-filled with talc having predominantly acicular particles (high surface area), shows a highest shear viscosity values, since high surface area fillers tend to increase the occluded polymer increasing the effective filler volume. The addition of a high level of coating decreasess hearv iscosity of the system,a ddition of a reactivec oupling systems lightly increasess hearv iscosity. Wall slip for unfilled PP was consistently evident. The slip velocity increases systematically with shear stress, but there is a critical value below which slip velocity was negligible. Addition of talc decreased the slip velocity at a given stress. A mechanism of slip has been proposed whereby a 'slip layer' on the die surface provides a sharp, low energy interface over which, at sufficiently high shear stress, the fluid PP can slip. A new empirical model has been proposed to predict the slip velocity of filled PP, as a function of talc volume fraction. PP filled with 10 % wt. talc having predominantly acicular particles, showed a higher slip velocity than PP filled with talc of other morphologies. It was observed that slip velocity increased by coating talc (either by use of coating or coupling agents) due to modification of velocity distributions in the flow channel. Extrudate swell increases with increasing shear rate for unfilled and talc-filled PP compounds. Inclusion of talc generally decreases the swell over the entire range of shearr ates studied,b ecauset he addition of talc to PP increasesth e shear/extensional modulus and thereby decreasede lastic strain recovery. No appreciablei nfluence of particle size on swell ratio was observed. Coating talc with octyltriethoxysilane produces higher swell relative to uncoated filled PP, and higher coating levels consistently produced higher swell values. However, coupling agent 7- aminopropyltriethoxsilane and maleic anhydride modified polypropylene both reduced the swell of the filled polymer system, with a more pronounced effect in extension than in shear. Swell decreased with an increase in capillary length-todiameter ratio and increased with increase in shear rate, (or shear stress) with or without coating/coupling agent. Addition of talc fillers delayed the onset of melt fracture and higher loadings of talc completely suppressed the melt fracture in the range of shear rate studied. Melt fracture for unfilled and filled PP has been studied and quantified by the frequency of the melt distortion. A mechanism for polymer melt fracture has been proposed to explain the results, based on the tensile failure of the material in extensional deformation. It was found that shear rate and die L/D ratio were the major causes of changesin severity of melt fracture for the unfilled and talc-filled compoundss tudied. However, talc morphology and particle size did not have significant effects on the severity of melt fracture.

APA, Harvard, Vancouver, ISO, and other styles

28

Jodoin, Jeffrey Joseph. "The production of polypropylene microcellular foam." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/14857.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Zeng, Fuquan. "Investigation into the colouration of polypropylene." Thesis, University of Manchester, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557624.

Full text

Abstract:

Polypropylene (PP) offers many advantages to the textile processor in terms of its durability and end use properties. However, a major technical flaw of PP is its inability to be dyed due to its relative lack of dye adsorption sites and high crystallinity. Therefore it is primarily mass pigmented, with pigment incorporated into the polymer melt prior to extrusion. While this approach offers a successful commercial route it does lack process flexibility. Some research has focused on modifying the polymer structure by incorporating dyeable copolymers or chemically degrading the base polymer by aqueous treatments to create polar groups for dye adsorption. However, both of these approaches have had little success due to processing difficulties, excessive deterioration of polymer properties and cost. In this study the primary thrust of the research has been to evaluate the use of dry gaseous fluorine treatments to modify the PP fibre and create dyeability and better colour fastness. XPS and FTIR indicate reaction between fluorine and the polypropylene fibre and the introduction of carboxyl groups and fluorine into the polymer. The introduction of these carboxyl groups and strongly electronegative negative fluorine leads to the fibre's enhanced basic dyeability. SEM analysis showed the impact of fluorine exposure on fibre surface morphology is relatively small. The effectiveness of pre-treatments on pigment dyeing and printing has also been evaluated. Colour fastness was significantly improved by a gaseous fluorine pretreatment of the textile substrate. The Helizarin Binder UDR pigment dyed system showed better performance in terms of colour fastness than other commercial binder systems evaluated. Optimisation of the binder to pigment ratio has been achieved in order to obtain good colour fastness. The dycability of moulded polyacetal zips was also examined in order to potentially replace the current mass pigmentation process. Fluorine pre-treatments showed no benefits in the overall colouration. properties in terms of long liquor dyeability or pigment dyeing. Of the disperse dyes evaluated the "high performance" SF and XF classes had the best colour fastness, in particular Dispersol Red CBN-SF, Dispersol Blue XF and Dispersol Flavine XF. A range of after-treatments were evaluated and a "reduction cleae, significantly improved the colour fastness. The polyacetal/polyester zip construction offered significant colouration difficulties due to the inherent problem of achieving a uniform, compatible, "soliX' dye shade. Although some success was achieved, commercial utilisation is less likely due to increasing process complexity.

APA, Harvard, Vancouver, ISO, and other styles

30

Gupta, Saloni. "Physico-chemical properties of polypropylene glycols." Thesis, University of Greenwich, 2015. http://gala.gre.ac.uk/21538/.

Full text

Abstract:

Poly(propylene glycol) (PPG) samples of different molecular mass were characterized using differential scanning calorimetry, modulated differential scanning calorimetry, thermogravimetry and thermally stimulated current (TSC) spectroscopy. It was shown, by TSC, that the glass transition temperature and the degree of molecular mobility increased with increasing molecular mass of PPG. Additional experiments showed that PPGs of molecular mass 425, 1000 and 2000 Da undergo one global relaxation process; however, PPG 2700 (Da) undergoes an additional relaxation process after the glass transition which has been attributed either to the release of the excess charge delocalised in the polymer structure or a liquid-liquid transition. Thermally induced phase separation in aqueous solutions of PPG has been examined using a variety of techniques including high sensitivity scanning calorimetry (HSDSC), hot stage microscopy, small angle neutron scattering, and turbidity measurements. The data suggest that phase separation is a consequence of PPG aggregation (droplets); the aggregates grow in size, as the temperature is raised further. It is postulated that phase separation occurs via nucleation and growth, which is corroborated by model fitting the calorimetric data using a mass action aggregation model. It is concluded that phase separation of PPG occurs as a result of the disruption of a hydrogen bonded network between water and PPG. The effect of five sugars (mannitol, maltose, raffinose, sucrose and trehalose) on the Tm (transition temperature) of aqueous PPG 1000 solutions was studied by HSDSC and turbidity measurements. All the sugars decreased the phase separation temperature of the PPG solutions, with trehalose and maltose showing the greatest effect. A series of experiments, using HPLC, showed that phase separated PPG (1000 Da) increased the apparent aqueous solubility of naphthalene.

APA, Harvard, Vancouver, ISO, and other styles

31

liu, lei. "Polypropylene block copolymer synthesis by metathesis." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1625523936334755.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Thiraphattaraphun, Linda. "Structure/property relationships in polypropylene nanocomposites." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/structureproperty-relationships-in-polypropylene-nanocomposites(388eafc0-a98e-4a78-be0d-4d647a122d87).html.

Full text

Abstract:

In this work, structure/property relationships in polypropylene (PP) nanocomposites have been investigated for different nanofillers. Nanofillers of modified clay based on montmorillonite (MMT) and multi-wall carbon nanotubes (MWNTs) have been selected and incorporated to the PP matrix as either single nanofillers or hybrid nanofillers. Melt mixing via a twin screw extruder and further moulding by injection moulding have been used to prepare PP nanocomposites. Moreover, the dilution of MWNT masterbatch has been used to prepare PP/MWNT and PP/clay/MWNT nanocomposites. Three types of the PP nanocomposites have been obtained: PP/clay, PP/MWNT and PP/clay/MWNT nanocomposites. In all three types of the PP nanocomposites, α- and -PP crystals were observed in the wide angle X-ray diffraction (WAXD) patterns. Furthermore, the addition of nanofillers to the PP did not appear to affect the PP orientation. Slight PP orientation in the PP nanocomposites was shown in the two-dimensional X-ray diffraction (2D-XRD) patterns. Mixed clay layers were combined in the PP/clay and PP/clay/MWNT nanocomposites and investigated by WAXD as well as transmission electron microscopy (TEM). In addition, the aggregated and individual MWNTs were present in both the PP/MWNT and PP/clay/MWNT nanocomposites TEM images. A rough fracture surface with cracks was revealed from the scanning electron microscopy (SEM) images of the three types of PP nanocomposites. Polarized optical microscopy (POM) micrographs were taken at different temperatures during cooling in a hot stage and revealed the limitation of PP spherulite growth upon adding the nanofillers to the PP. The incorporation of nanofillers was found not to affect the glass transition temperature (Tg) of PP which investigated by dynamic mechanical analysis (DMA). However, the increase of both the peak melting temperature (Tm) and the peak crystallization temperature (Tc) of PP with adding the nanofillers was shown by differential scanning calorimetry (DSC) thermograms. In addition, the nanofillers also have been shown to act as nucleating agents. The thermal stability of PP in a nitrogen atmosphere was enhanced by the nanofillers when examined by thermogravimatric analysis (TGA). DMA and tensile testing were performed and showed that the nanofillers act as reinforcement for the PP. The distribution, orientation and deformation of MWNTs in the PP/MWNT and PP/clay/MWNT nanocomposites have been followed by Raman spectroscopy. Significant shifts of the Raman G'-band from the MWNTs was obtained during deformation of the MWNT nanocomposites and the hybrid clay/MWNT nanocomposites as the stress transfer from the PP matrix to the MWNTs has occurred. A correlation between calculated modulus from deformation and measured modulus from DMA and tensile testing has been found for PP/MWNT and PP/clay/MWNT nanocomposites. Finally, the PP nanocomposites have been considered for use in packaging applications.

APA, Harvard, Vancouver, ISO, and other styles

33

Metin, Dildare Tıhmınlıoğlu Funda. "Interfacial enhancement of polypropylene-zeolite composites/." [s.l.]: [s.n.], 2002. http://library.iyte.edu.tr/tezler/master/kimyamuh/T000132.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Barroso, Gago Luísa. "Création in situ d'une phase thermodurcissable dans une matrice polyoléfine par extrusion réactive." Electronic Thesis or Diss., Lyon, 2021. http://www.theses.fr/2021LYSE1031.

Full text

Abstract:

Cette thèse a pour objectif d’exploiter une gamme de thermoplastique/thermodurcissable à base de polyoléfines et en particulier le polypropylène (PP). Deux types de systèmes thermodurcissables ont été retenus : un système type époxy/amine et un système époxy/durcisseur phénolique, compatibilisés avec la phase thermoplastique par un polypropylène greffé anhydride maléique (PP-g-MA). Le but de ce travail de thèse est de comprendre les mécanismes de réaction et leurs avancements au cours de l’étape de dispersion dans la matrice polyoléfine pendant l’opération d’extrusion réactive ainsi que le lien entre morphologies finales obtenues, les propriétés macroscopiques, en particulier mécaniques, et la cristallinité du matériau. Pour ce faire, les principaux axes à développer sont tout d’abord, l’étude complète des systèmes thermodurcissables et leur réaction en présence de PP hors extrusion (déduire des tendances, des mécanismes de compréhension pour pouvoir les généraliser) ainsi que l’étude de la miscibilité des différents systèmes. De plus, nous avons transposé ces observations au matériau extrudé. Par la suite, une étude complète de ce matériau nous a permis de relier morphologie, propriétés mécaniques et apparition d’une nouvelle phase cristalline b grâce à la création in situ de thermodurcissable. Finalement, l’utilisation de ce nouveau matériau développé dans des composites renforcé fibre de verre, s’est avérée être une excellente solution pour la tenue au fluage
This thesis aims to exploit a range of thermoplastic / thermosetting based on polyolefins and in particular polypropylene (PP). Two types of thermosetting systems were selected: an epoxy / amine type system and an epoxy / phenolic hardener system, compatibilized with the thermoplastic phase by a polypropylene grafted with maleic anhydride (PP-g-MA). The purpose of this thesis work is to understand the reaction mechanisms and their advancements during the step of dispersion in the polyolefin matrix during the reactive extrusion as well as the link obtained between final morphologies, the macroscopic properties, in particular mechanical, and the crystallinity of the material. In order to do this, the main axes to be developed are, first of all, the complete study of thermosetting systems and their reaction in the presence of PP outside extrusion (deducing trends, understanding mechanisms to be able to generalize them) as well as the study of the miscibility of the different systems. In addition, we have transposed these observations to the extruded material. Subsequently, a complete study of this material allowed us to link morphology, mechanical properties and the appearance of a new crystalline b-phase thanks to the in situ creation of thermosets. Eventually, the use of this new material developed in fiberglass reinforced composites, proved to be an excellent solution for creep resistance

APA, Harvard, Vancouver, ISO, and other styles

35

Lee, Tiehong. "A study of miscibility, morphology, crystallization and melting behavior of isotactic poly(propylene) in blends of poly(propylene) and poly(1-butene)." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07292009-090250/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Msuya, Winston Filipo Seth. "The influence of physical ageing and morphology on yield in polypropylene." Thesis, [Hong Kong] : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12434036.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Manji, Aminmohamed. "Electro synthesis of propylene oxide in a bipolar trickle bed reactor." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25117.

Full text

Abstract:

The synthesis of propylene oxide by electrolysis of dilute sodium bromide solution with propylene gas was investigated in an electrochemical bipolar reactor consisting of six parallel fixed beds of graphite particles separated by polypropylene felt diaphragms. One reactor was operated in single pass and recycle mode with two phase co-current flow of propylene and sodium bromide solution through the beds of graphite particles. The maximum pressure in the system was 2.22 atmospheres absolute. The effects of superficial current density* (413 - 2687 A/m²), electrolyte (sodium bromide solution) concentration (0.2 M and 0.5 M), electrolyte flow rate (100 and 300 cm³ /min), propylene gas flow rate (100/1000/1500/2000 cm³/min at STP), reactor outlet temperature (30° and 60°C), bed thickness (six beds - 8.57/4.29/3.07 cm) and different carbon types (Union Carbide and Ultra Carbon) on the space time yield and selectivity for propylene oxide were measured. Depending on the condition for single pass runs, the space-time yield for propylene oxide was between 5.5 kg/hr m³ and 97.2 kg/hr m³, and the selectivity was between 54.5% and 87.3%. The current efficiency and the specific energy consumption varied from 14.0 to 58.2 percent and 5.7 to 59.9 Kwh/kg of propylene oxide. The space-time yield for propylene oxide increased with decreasing bed thickness. For the recycle mode the space-time yield decreases with time. The highest space time yield obtained after one hour of operation was 127.8 kg/hr m³ with a selectivity of 95.9%. The current efficiency for hydrogen, oxygen and dibromopropane was also determined. *Superficial current density = applied current/electrode area.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

APA, Harvard, Vancouver, ISO, and other styles

38

Amanabadi, Seyed Hassan Jafari. "Impact toughening and crystallization studies on binary blends of polypropylene." Thesis, IIT Delhi, 1998. http://localhost:8080/xmlui/handle/12345678/3113.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Al-Shehri, Abdulhadi S. "Tensile and fracture behaviour of isotropic and die-drawn polypropylene-clay nanocomposites : compounding, processing, characterization and mechanical properties of isotropic and die-drawn polypropylene/clay/polypropylene maleic anhydride composites." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/5223.

Full text

Abstract:

As a preliminary starting point for the present study, physical and mechanical properties of polypropylene nanocomposites (PPNCs) for samples received from Queen's University Belfast have been evaluated. Subsequently, polymer/clay nanocomposite material has been produced at Bradford. Mixing and processing routes have been explored, and mechanical properties for the different compounded samples have been studied. Clay intercalation structure has received particular attention to support the ultimate objective of optimising tensile and fracture behaviour of isotropic and die-drawn PPNCs. Solid-state molecular orientation has been introduced to PPNCs by the die-drawing process. Tensile stress-strain measurements with video-extensometry and tensile fracture of double edge-notched tensile specimens have been used to evaluate the Young's modulus at three different strain rates and the total work of fracture toughness at three different notch lengths. The polymer composite was analyzed by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, wide angle x-ray diffraction, and transmission electron microscopy. 3% and 5% clay systems at various compatibilizer (PPMA) loadings were prepared by three different mixing routes for the isotropic sheets, produced by compression moulding, and tensile bars, produced by injection moulding process. Die-drawn oriented tensile bars were drawn to draw ratio of 2, 3 and 4. The results from the Queen's University Belfast samples showed a decrement in tensile strength at yield. This might be explained by poor bonding, which refers to poor dispersion. Voids that can be supported by intercalated PP/clay phases might be responsible for improvement of elongation at break. The use of PPMA and an intensive mixing regime with a two-step master batch process overcame the compatibility issue and achieved around 40% and 50% increase in modulus for 3% and 5% clay systems respectively. This improvement of the two systems was reduced after drawing to around 15% and 25% compared with drawn PP. The work of fracture is increased either by adding nanoclay or by drawing to low draw ratio, or both. At moderate and high draw ratios, PPNCs may undergo either an increase in the size of microvoids at low clay loading or coalescence of microvoids at high clay loading, eventually leading to an earlier failure than with neat PP. The adoption of PPMA loading using an appropriate mixing route and clay loading can create a balance between the PPMA stiffness effect and the degree of bonding between clay particles and isotropic or oriented polymer molecules. Spherulites size, d-spacing of silicate layers, and nanoparticles distribution of intercalated microtactoids with possible semi-exfoliated particles have been suggested to optimize the final PPNCs property.

APA, Harvard, Vancouver, ISO, and other styles

40

Badji, Célia. "Vieillissement de matériaux composites renforcés de fibres naturelles : étude de l’impact sur les propriétés d’aspect et sur les émissions dans l’air intérieur." Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3022/document.

Full text

Abstract:

Les biocomposites sont des matériaux renforcés de fibres issues de ressources renouvelables. Ces matériaux sont une solution alternative aux composites renforcés de fibres de verre ou de carbone. En effet, leur légèreté et leurs propriétés mécaniques intéressantes leur confèrent un intérêt grandissant dans les secteurs tels que la construction (terrasse, meubles de jardin) ou l’automobile (panneaux de porte, tableaux de bord). Toutefois, les milieux humides, la température et le rayonnement UV sont des paramètres pouvant compromettre la stabilité physico-chimique des biocomposites. L’objectif principal de cette thèse a été d’évaluer la durabilité des biocomposites sous leurs conditions d’usage principales. Pour cela, ces matériaux ont été exposés pendant une année à l’extérieur (lames de terrasse) et sous vitre pare-brise (tableaux de bord). Les résultats ont montré que, bien que la performance mécanique des biocomposites ait été affectée, celle-ci n’a pas été grandement influencée par le type d’exposition. Par contre, les différences de variations de couleur et de cristallinité différant entre les deux expositions suggèrent des mécanismes de dégradation différents et très dépendants des conditions d’usage.Puisque les biocomposites peuvent être utilisés dans des environnements clos tels que les habitacles d’automobile, ils peuvent être également des sources de polluants dans l’air intérieur. L’étude des émissions de composés organiques volatils (COV) par les biocomposites au cours de leur vieillissement sous vitre pare-brise, a permis de générer des données nécessaires à l’évaluation de l’impact sur la qualité de l’air intérieur de véhicule de ces nouveaux matériaux. Cependant, l’augmentation drastique de la concentration de surface en COV au cours du vieillissement suggère que l’exposition a fortement affecté les biocomposites à cause de la sensibilité des composants structurant les fibres végétales face aux conditions d’exposition.La compréhension des mécanismes de dégradation peut s’effectuer à travers l’interprétation des liens de causalité entre les propriétés mécaniques et de microstructure, les émissions de COV, et l’apparence visuelle. Un traitement statistique par analyse en composantes principales (ACP) a ainsi permis de dégager les relations entre les paramètres quantitatifs.Le vieillissement naturel nécessite souvent une durée d’exposition longue pour apercevoir une dégradation effective des matériaux. De ce fait, le vieillissement accéléré en enceinte de laboratoire est de plus en plus réalisé en industrie permettant un gain de temps. Afin de vérifier la représentativité des mécanismes de dégradation en environnement extérieur par l’enceinte, une étude comparative entre le vieillissement naturel extérieur et un vieillissement accéléré en enceinte a été menée
Biocomposites are fiber-reinforced materials from renewable resources. These materials are an alternative to fiberglass or carbon reinforced composites. Indeed, their lightweight and interesting mechanical properties give them a growing interest in sectors such as building (decking, garden furniture) or automobile (door panels, dashboards). However, humidity, temperature and UV radiation are parameters that can compromise the physicochemical stability of biocomposites.The main objective of this thesis is to assess the biocomposites durability in their main conditions of use. For this purpose, these materials have been exposed for one year outdoors (deck boards) and under windshield glass (dashboards). The results showed that the mechanical performance of biocomposites was affected and greatly influenced by the type of exposure. On the other hand, the differences in color and crystallinity variations that differ between the two exposures suggest different degradation mechanisms that are very dependent on the conditions of use.Since biocomposites can be used in environments such as the passenger cabin, they can also be sources of pollutants in indoor air. The study of emissions of volatile organic compounds (VOCs) by biocomposites during their ageing under windshield glass allowed generating data necessary for the evaluation of the impact on the car indoor air quality of these new materials. However, the drastic increase of VOCs surface concentration during exposure suggests that weathering strongly affected biocomposites due to the sensitivity of the structural components of plant fibers to exposure conditions.Understanding of the degradation mechanisms can be carried out through the interpretation of the causal links between mechanical and microstructural properties, VOC emissions and visual appearance. Statistical treatment by Principal Component Analysis (PCA) revealed the links and relationships existing between the quantitative parameters.Natural weathering often requires long time of exposure for an efficient perception of the materials degradation. Thus, accelerated ageing in laboratory is more and more carried out in industry for time saving. In order to verify the representativeness of the degradation mechanisms occurring during exterior weathering by weathering chambers, a comparative study between the exterior aging and the artificial aging was carried out

APA, Harvard, Vancouver, ISO, and other styles

41

Ecevit, Tuba Safiye. "Synthesis And Characterization Of Surface Sulfonated Polypropylene." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/3/12604846/index.pdf.

Full text

Abstract:

ABSTRACT SYNTHESIS AND CHARACTERIZATION OF SURFACE SULFONATED POLYPROPYLENE FILMS Ecevit, Safiye Tuba M.S., The Department of Polymer Science and Technology Supervisor: Leyla Aras, Prof. Dr. Co- Supervisor: Teoman Tinç
er, Prof. Dr. March 2004, 44 pages The basic reseach on the surface sulfonation of the polypropylene is very important due to the surface design for higher functionalization. For this purpose, liquid-phase sulfonation of the polypropylene surfaces at various temperatures for different time periods were performed by concentrated sulphuric acid. The physical and chemical changes formed by the effect of the sulfonation on the polypropylene surfaces were determined by contact angle measurement, mechanical analysis, UV-Vis spectrometer, differential scanning calorimeter (DSC) and scanning electron microscopy (SEM). The surface polarity and wetting properties of the samples were evaluated by contact angle measurement. It is seen that, sulfonation at low temperatures and short time periods improve these two properties of the polypropylene surfaces. Sulfonation at high temperatures and long time periods however, cause the partial breakdown of the polymer by degradation. Noticeable color change due to the degradation and carbonization of the polypropylene films sulfonated at high temperature and long time were supported by the UV-Vis spectra of the samples. Mechanical properties of sulfonated PP films were investigated. Consequently, after the sulfonation process the mechanical properties of the PP films showed a general trend of decrease with sulfonation time for a given temperature and a very fast decrease at high temperature of sulfonation. Thermal characteristics were found by differential scanning calorimeter (DSC). Thermal analysis revealed that sulfonated PP film samples displayed an additional endothermic peak. The physical effects of the sulfonation were examined by scanning electron microscopy (SEM) which showed a hexagonal hole formations due to the bursting of the air bubbles within the PP films by the effect sulfonation. The lamelae formations were also seen around these holes.

APA, Harvard, Vancouver, ISO, and other styles

42

Yayla, Saniye. "Production And Characterization Of Polypropylene/organoclay Nanocomposites." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12608485/index.pdf.

Full text

Abstract:

Polypropylene, PP, based nanocomposites were produced via melt blending method by using twin-screw extrusion in this study. The effects of organoclay type, compatibilizer type, and mixing order of components on the morphology, thermal, mechanical and flow properties of ternary nanocomposites were investigated. Terpolymer of ethylene/butyl acrylate/maleic anhydride, ethylene/methyl acrylate/glycidyl methacrylate, and copolymer of ethylene/glycidyl methacrylate elastomers were used as compatibilizer, whereas Cloisite®
30B, Cloisite®
15A, and Cloisite®
25A were used as organoclay. iv In order to determine the optimum amount of compatibilizer, PP/compatibilizer blends were produced with different compositions. The content of compatibilizer was determined as 5 wt % based on the mechanical tests. Then, ternary nanocomposites were prepared with 5 wt % compatibilizer and 2 wt % organoclay contents. In addition, neat PP and PP/organoclay composites were prepared in order to make comparison. After that, the samples were characterized. According to the XRD analysis, the highest increase in the interlayer spacings of organoclays were observed in the PP/E-MA-GMA/Cloisite®
15A (23%) and PP/E-MA-GMA/ Cloisite®
25A (88.3%) ternary systems. SEM micrograms revealed that compatibilizer E-MA-GMA is the most compatible elastomer with PP. Thus, it was decided to investigate the effect of mixing order on the properties of these nanocomposites with E-MA-GMA. DSC analysis showed that the melting behavior of the nanocomposites does not change significantly with the presence of organoclay and compatibilizer. In addition, compatibilizers and organoclays have no significant nucleation activity in PP. The systems PP/E-MA-GMA/Cloisite®
15A and PP/E-MA-GMA/Cloisite®
25A have the highest improvements according to the results of mechanical tests. The results of mechanical tests showed that the mixing sequence (PEC), in which PP, organoclay and compatibilizer were compounded simultaneously in the first extrusion run, is the best sequence.

APA, Harvard, Vancouver, ISO, and other styles

43

Vange, Kjetil. "Validation of material model for polypropylene (PP)." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18517.

Full text

Abstract:

Polymers are the up and coming engineering material. The number of possibleapplications is increasing fast and so is the need for a good polymer material model. Thescientists at SIMLab at NTNU have developed such a material model. In this thesis is thematerial model calibrated to represent an impact modified polypropylene used by Toyota.The validation started with the calibration. A review of the theoretical background of thematerial model and a detailed explanation of the calibration procedure are given todescribe the derivation of the calibrated material model. The model is then applied in FEsimulationsof the material tests and the two validation tests. The first validation test is aquasi-static tension test using a specimen with a centric hole. This test resembles thematerial tests but the centric hole makes the load response slightly more complex. Theother test is an impact test using a drop tower. This test validates the material modelsability to represent dynamic problems and also tests the representation of the strain ratedependency.The material model proves that it is capable of representing all the tests in this thesis quite accurately.

APA, Harvard, Vancouver, ISO, and other styles

44

Sælen, Kristin. "Validation of material model for polypropylene (PP)." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18793.

Full text

Abstract:

A hyperelastic-viscoplastic material model intended for thermoplastics has been developed by SIMLab at NTNU. This model formed the basis of the thesis, where a material model for the polymer polypropylene was calibrated and validated. Four rounds of material testing were carried out. Tension and compression tests formed the basis for a calibration of the material model. Two different component tests were used for validation; stretching of a plate with a hole and plate impact tests.The calibrated model was implemented as a user-defined material model in the non-linear finite element code LS-DYNA, and numerical simulations of the tension and compression tests were carried out in order to verify the calibrated parameters. The component tests were numerically simulated with the purpose of controlling the ability of the model to predict the behaviour of the material when subjected to more complex loading cases.The calibrated material model was able to capture the main characteristics of the experimental tests. The model does, however, have limitations, as it was not able to correctly predict all strain rate effects of the material at high strain rates, like viscoelasticity. A partly recalibration of the material model was carried out to enable the model to predict the material’s behaviour at high strain rates.

APA, Harvard, Vancouver, ISO, and other styles

45

Khoshkava, Vahid. "Polypropylene (PP) nanocomposites incorporating nanocrystalline cellulose (NCC)." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121442.

Full text

Abstract:

The main objective of this dissertation is to evaluate the feasibility of preparation of well dispersed polypropylene (PP)/nanocrystalline cellulose (NCC) nanocomposites by melt processing. There has been growing interest in using NCC as reinforcement in polymer systems because of its interesting properties and the abundant and renewable sources of cellulose. Preparation of polymer nanocomposites incorporating NCC has been mainly carried out using solution or water-assisted mixing. Only few attempts have been made to prepare it using melt mixing. Polypropylene (PP) is a commodity polymer with wide application in the automotive, pharmaceutical and packaging industries. In the first phase of this project, physical properties (shape, size and surface energy) of NCC are evaluated. An equation was introduced to estimate the dispersion energy of NCC in polymer matrices based on room and high temperature surface energy data. The influence of NCC surface modification on its interaction with a polar polymer (polylactic acid (PLA)) and non-polar polymer (PP) was evaluated.In the second phase of this project, the relationship between NCC agglomerate structure and its dispersion in polymer matrices is considered. The effect of various drying techniques on NCC agglomerate structure is investigated. It was found that spray drying and freeze drying of NCC aqueous suspensions result in dense and compact NCC aggregates. On the other hand, spray freeze drying of NCC aqueous suspensions could form agglomerates with more open or porous structures. The structure of the agglomerates depends on the initial concentration of the NCC aqueous suspension before spray freeze drying. In the low concentration regime (below ca. 2 wt.%), a web-like structure of inter-connected nano-scale fibers is formed. On the other hand, micron sized spherical-foam structure particles are formed at higher concentration (ca. 2 wt.% and above). The specific surface area of NCC powder produced using spray freeze drying increased by more than 30 times.Polypropylene nanocomposites containing spray dried NCC, freeze dried NCC, and spray freeze dried NCC (NCCSFD) were prepared in an internal batch mixer. Polarized light microscopy (PLM) and scanning electron microscopy (SEM) showed better dispersion of NCCSFD particles. The results of dynamic mechanical analysis (DMA) and tensile tests showed a considerable improvement in modulus and tensile strength of samples containing NCCSFD particles. Rheological measurements, including linear and non-linear viscoelastic tests, were performed on PP/NCC samples. Small amplitude oscillatory (SAOS) tests showed a large impact of NCCSFD incorporation on rheological characteristics of PP samples. Steady shear results revealed strong shear thinning and a yield stress for PP samples containing NCCSFD particles. The magnitude of yield stress and the degree of shear thinning increased with NCCSFD concentration. The effects of NCC structure (web-like and spherical-foam structure) on rheological properties were examined.
Le principal objectif de cette dissertation consiste à évaluer la faisabilité de la préparation de polypropylène bien dispersé (PP) / la cellulose nanocristalline du (NCC) nanocomposites par traitement par fusion. Il ya un intérêt croissant à utiliser du (NCC) comme renforcement dans les systèmes de polymère à cause de ses propriétés intéressantes et les sources de cellulose abondante et renouvelable. La préparation de nanocomposites polymères incorporant du NCC a été principalement effectuée en utilisant une solution ou un mélange d'eau-assistée. Seulement quelques essais ont été faites à préparer en utilisant un mélange à l'état de fondre. Le polypropylène (PP) est un polymère produit à de larges applications dans l'industrie de l'automobile, produits pharmaceutiques et les industries d'emballage.Dans la première phase de ce projet, les propriétés physiques (forme, taille et d'énergie de surface) du NCC sont évaluées. Une équation a été présentée pour estimer l'énergie de la dispersion du NCC dans les matrices à base de polymère dans une la pièce et les données d'énergie de surface à haute température. L'influence de la modification de surface du NCC et son interaction avec un polymère polaire (acide polylactique (PLA)) et un polymère non polaire (PP) a été évaluée.Dans la deuxième phase de ce projet, la relation entre la structure d'agglomérat du NCC et sa dispersion dans des matrices de polymère est considérée. L'effet des diverses techniques de séchage sur la structure des agglomérats du NCC est examiné. On a constaté que séchage par pulvérisation et par lyophilisation du NCC, les suspensions aqueuses se traduisent dans les agrégats du NCC denses et compactes. D'autre part, la pulvérisation par lyophilisation des suspensions aqueuses du NCC pourrait former des agglomérats ou des structures poreuses plus ouvertes. La structure des agglomérats dépend de la concentration initiale de la suspension aqueuse du NCC avant la pulvérisation par lyophilisation. Dans le régime à faible concentration (en dessous de2%environ en poids), une structure en forme de bande de fibres interconnectée à l'échelle nanométrique est formée. D'autre part, le micron dimensionné des particules de structure sphérique est formé à une concentration plus élevée (ca. 2 wt.% et au-dessus). La surface spécifique de la poudre du NCC produite en utilisant le séchage par atomisation ou lyophilisation a progressé de plus de 30 fois. Les nanocomposites contenant du polypropylène séché par pulvérisation du NCC, et lyophilisés à froid du NCC (NCCSFD) ont été préparé dans un malaxeur discontinu interne. La microscopie en lumière polarisée (PLM) et la microscopie électronique à balayage (SEM) ont montré une meilleure dispersion des particules de NCCSFD. Les résultats de l'analyse mécanique dynamique (DMA) des tests de traction ont démontré une amélioration considérable de modules de résistance à la traction des échantillons contenant des particules de NCCSFD. Des mesures rhéologiques, y compris les tests de viscoélasticité linéaire et non linéaire, ont été effectuées sur des prélèvements des PP/NCC. De petits tests oscillatoires d'amplitude (SAOS) ont montré un impact considérable d'incorporation de NCCSFD sur les caractéristiques rhéologiques des échantillons de PP. Des résultats réguliers de cisaille ont révélé une forte fluidification par cisaillement et une limite d'élasticité pour les échantillons de PP contenant des particules de NCCSFD. La magnitude de la limite de stress et le degré de rhéofluidification a augmenté avec la concentration de NCCSFD. Les effets de la structure du NCC (sous forme de bande et la structure en mousse sphérique) sur les propriétés rhéologiques ont été examinés.

APA, Harvard, Vancouver, ISO, and other styles

46

Francois, heude Alexandre. "Kinetic modeling of the polypropylene photothermal oxidation." Phd thesis, Ecole nationale supérieure d'arts et métiers - ENSAM, 2014. http://pastel.archives-ouvertes.fr/pastel-01069008.

Full text

Abstract:

Developing numerical tools for polymer lifetime prediction constitutes a promising opportunity for shortening the duration of material certification procedures in the automotive industry without decreasing their reliability. This PhD thesis aims at modeling the photothermal oxidation of isotactic polypropylene (iPP), which is responsible for the alteration of both its mechanical and aspect properties. The adopted approach consists in coupling the kinetics of photo- and thermo-oxidation reactions with physical phenomena, such as oxygen transport and UV-light attenuation in the material thickness, in order to describe all the physico-chemical changes. Upper-scale properties, from which will be defined the end-of-life criteria, will be calculated afterwards by applying the suitable structure-property relationships. The main challenge was to extend the pre-existing kinetic model of thermal ageing to photothermal ageing by taking into account initiation reactions of photolysis. Heavy campaigns of ageing and characterization tests made on a reference iPP, as well as an exhaustive capitalization of literature data of other iPPs, have allowed elaborating a kinetic model of photothermal oxidation and to generalize it to the whole iPP family in large domains of oxygen partial pressure (from 0.2 to 50 bars), temperature (from 40 to 230°C) and UV-light exposure (variable intensities and light sources) describing both natural and accelerated ageing conditions. The experimental validation of the model has allowed substantiating the kinetic approach and showing its limitations, as well as highlighting some numerical issues. The model has been designed in order to be an upgradable numerical tool which will allow, at term, optimizing the representativeness of the ageing testing devices and the performance of commercial iPP formulations. All these theoretical and numerical developments are prone to be applied to the photothermal degradation of other types of polymer substrates, but also in other application fields of the macromolecular photochemistry such as UV-photopolymerization.Keywords: Polypropylene, photothermal oxidation, oxygen diffusion control, screen effect, kinetic modeling, lifetime prediction.

APA, Harvard, Vancouver, ISO, and other styles

47

Ohno, Sadatoshi. "Stress transfer in polypropylene fibre reinforced cement." Thesis, University of Surrey, 1990. http://epubs.surrey.ac.uk/849/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Badr, Atef Samir M. "Performance of advanced polypropylene fibre reinforced concrete." Thesis, University of Leeds, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437106.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Amer, Ismael. "Molecular weight effects on crystallization of polypropylene." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6649.

Full text

Abstract:

Thesis (PhD)--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: The crystallization of polyolefins is an important parameter in determining the properties of such materials. The crystallization phenomenon generally depends on the molecular symmetry (tacticity) and molecular weight of the material. In this study, a series of polypropylenes was prepared using heterogeneous MgCl2-supported Ziegler catalysts with two different external donors, diphenyldimethoxysilane (DPDMS) and methyl-phenyldimethoxysilane (MPDMS), and two different homogeneous metallocene catalysts, racethylene- bis(indenyl) zirconium dichloride, Et(Ind)2ZrCl2 (EI), and rac-ethylene-bis(4,5,6,7- tetrahydro-1-indenyl) zirconium dichloride, Et(H4Ind)2ZrCl2 (EI(4H)). Molecular hydrogen was used as terminating agent. In order to establish a correlation between the molecular weight and the crystallization of these polymers, fractionation of the materials according to crystallizability was performed by means of temperature rising elution fractionation (TREF). This affords the opportunity of blending materials of different molecular weights but similar symmetry. These materials were characterized using various analytical techniques: differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), 13C nuclear magnetic resonance spectroscopy (13C-NMR), high temperature gel permeation chromatography (HT-GPC) and Fourier-transform infrared spectroscopy (FT-IR). DSC was used to study the bulk crystallization of different polypropylene blends, most of which showed only one melting peak. The latter is usually associated with a high degree of cocrystallization. Turbidity analysis of the different polypropylene polymers, obtained using solution crystallization analysis by laser light scattering (SCALLS), provided good crystallization information – similar to that provided by crystallization analysis fractionation (CRYSTAF) and TREF. It was also possible to differentiate between polypropylenes with similar chemical structure but different tacticity and molecular weight. SCALLS results also showed that the blends of different isotactic polypropylene polymers were miscible and cocrystallization had occurred, whereas, the blends of syndiotactic polypropylene and different isotactic polypropylenes were not miscible and some interaction between phases had occurred. Optical microcopy (OM) and scanning electronic microscopy (SEM) were used to study the morphological properties of different isotactic polypropylenes. Results revealed a welldefined and large spherulitic morphology of mixed a1 (disordered) and a2 (ordered) crystal form structures. OM and SEM images also clearly showed an effect of molecular weight and tacticity on the crystal structure of the different polypropylene samples. Finally, various homopolymers and blends were studied to investigate the effect of molecular weight on the mechanical properties of these materials. This was done using microhardness testing and dynamic mechanical analysis.
AFRIKAANSE OPSOMMING: Die kristallisasie van poliolefiene is ‘n belangrike faktor wat die eienskappe van hierdie tipe materiale bepaal. In die algemeen hang kristallisasie af van die molekulêre simmetrie (taktisiteit) en molekulêre massa van die materiaal. ‘n Reeks polipropilene is berei deur gebruik te maak van heterogene MgCl2-ondersteunde Ziegler-kataliste met twee verskillende elektron donors, difenieldimetoksisilaan (DPDMS) en metielfenieldimetoksisilaan (MPDMS), en twee verskillende homogene metalloseenkataliste, rac-etileen-bis(indeniel) sirkoniumdichloried, Et(Ind)2ZrCl2 (EI), en rac-etileen-bis(4,5,6,7-tetrahidro-1-indeniel) sirkoniumdichloried, Et(H4Ind)2ZrCl2 (EI(4H)). Molekulêre waterstof is gebruik as termineringssagent. Ten einde ‘n verband te bepaal tussen die molekulêre massa en kristallisasie van hierdie polimere is hulle gefraksioneer op die basis van hulle kristallisseerbaarheid deur gebruik te maak van temperatuurstyging-elueringsfraksionering (TREF). Deur hierdie tegniek verkry ons materiale van verskillende molekulêre massa maar met dieselfde taktisiteit wat ons kan vermeng. Verskeie tegnieke is gebruik om hierdie materiale te karakteriseer: differensiële skandeerkalorometrie (DSC), wyehoek X-straal diffraksie (WAXS), 13C-kernmagnetiese resonansspektroskopie (13C-KMR), hoë-temperatuur gelpermeasiechromotagrafie (HT-GPC) en Fourier-transform-infrarooispektroskopie (FT-IR). DSC is gebruik om die vaste-toestand kristallisasie van verskeie vermengde polipropilene te bestudeer., en net een smeltpunt is in meeste gevalle waargeneem. Laasgenoemde word gewoonlik verbind met ‘n hoë mate van kokristallisasie. Oplossingkristallisasie analise, dmv laserligverstrooiing (SCALLS), is gebruik om die turbiditeit van die verskillende polipropileen kopolimeervermengings te bepaal. Goeie inligting aangaande die kristallisasie in oplossing – soortgelyk aan dié wat dmv die kristallisasie-analise-fraksioneringstegniek (CRYSTAF) en TREF bepaal is, is verkry. Dit was ook moontlik om te onderskei tussen polipropilene met soortgelyke chemiese strukture maar verskillende taktisiteit en molekulêre massas. SCALLS data het ook getoon dat die vermengings van verskeie isotaktiese polipropileen polimere versoenbaar was en dat kokristallisasie plaasgevind het, terwyl vermengings van sindiotaktiese polipropileen en verskeie isotaktiese polipropilene nie versoenbaar was nie en dat ‘n mate van fase-skeiding plaasgevind het. Optiese mikroskopie (OM) en skandeer-elektronmikroskopie (SEM) is gebruik om die morfologiese eienskappe van verskillende isotaktiese polipropilene te bepaal. Goed gedefineerde en groot sferulitiese morfologie van gemengde a1 (onordelike struktuur) en a2 (ordelike struktuur) kristal-strukture is waargeneem. OM en SEM beelde het ook gewys dat molekulêre massa en taktisiteit ‘n effek het op die kristalstruktuur van die verskillende polipropileenmonsters. Laastens is die meganiese eienskappe van ‘n verskeidenheid homopolimere en vermengde materiale bestudeer, deur gebruik te maak van mikro-hardheid metings en dinamiesmeganiese analise (DMA).

APA, Harvard, Vancouver, ISO, and other styles

50

McConville, Eileen. "Investigation of the thermoforming of polypropylene packaging." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675461.

Full text

Abstract:

Packaging is one of the major fields for plastic materials, with extruded polypropylene (PP) sheet widely used in the production of thin gauge tubs and containers for the food and beverage industry using the thermoforming process. In an increasingly competitive market understanding the fundamental material properties and the effect of thermoforming process settings can help a company deliver material and efficiency savings allowing them to reduce production, manufacturing and development costs. The main aim of this work was to advance the practical understanding of the processing of PP for packaging applications, by linking the fundamental material behaviour to the industrial thin gauge thermoforming process. During this work investigations were carried out into the basic properties of commercial grades of PP and the affect of blending on material and end container properties. The effect of extrusion and thermoforming process conditions on end container properties were also investigated along with large strain mechanical stretching using lab equipment capable of replicating the industrial process settings. Investigations into both the affect of extrusion settings and thermoforming settings have shown that the PP material grade selected can have a greater effect than changes in process settings; with changes in settings having a different degree of effect on the different PP material grades. Therefore it is important for a thermoformer not just to consider the material type but the material grade or percentage blend during product development. This work has also highlighted the fact that complex blends can be created everyday in the industrial thin gauge thermoforming process and these blends will greatly affect t,he behaviour of the material during processing, and the end container properties. Overall the work demonstrates how susceptible PP is to changes in blends and processing conditions and will be particularly relevant to the developing recycled materials area.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Polypropylene'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles