Polymeric materials are widely used in diverse applications. However, a major weakness in the majority of the thermoplastic polymers is their lack of ability to resist fire. Most of the chemicals and additives currently used to improve fire retardancy have deleterious effects on the environment. This research focuses on developing an environmentally safe and effective fire-retardant system for high density polyethylene (HDPE), using cellulose nanocrystals (CNCs) and zinc oxide (ZnO). The effect of CNCs coated with nano ZnO has been investigated for improving the fire resistance properties of the HDPE. Improved dispersion of CNCs into HDPE matrix was achieved by employing maleic anhydride as a coupling agent. It was found that addition of CNCs-ZnO can introduce a reasonable level of flame retardancy in HDPE matrix in addition to improving the maximum tensile strength and elongation at break.

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Oxidative processes are linked to a number of major disease states as well as the breakdown of many materials. Of particular importance are reactive oxygen species (ROS), as they are known to be endogenously produced in biological systems as well as exogenously produced through a variety of different means. In hopes of better understanding what controls the behavior of ROS, researchers have studied radical chemistry on a fundamental level. Fundamental knowledge of what contributes to oxidative processes can be extrapolated to more complex biological or macromolecular systems. Fundamental concepts and applied data (i.e. interaction of ROS with polymers, biomolecules, etc.) are critical to understanding the reactivity of ROS. A detailed review of the literature, focusing primarily on the hydroxyl radical (HO•) and hydrogen atom (H•) abstraction reactions, is presented in Chapter 1. Also reviewed herein is the literature concerning high density polyethylene (HDPE) degradation. Exposure to treated water systems is known to greatly reduce the lifetime of HDPE pipe. While there is no consensus on what leads to HDPE breakdown, evidence suggests oxidative processes are at play. The research which follows in Chapter 2 focuses on the reactivity of the hydroxyl radical and how it is controlled by its environment. The HO• has been thought to react instantaneously, approaching the diffusion controlled rate and showing little to no selectivity. Both experimental and calculational evidence suggest that some of the previous assumptions regarding hydroxyl radical reactivity are wrong and that it is decidedly less reactive in an aprotic polar solvent than in aqueous solution. These findings are explained on the basis of a polarized transition state that can be stabilized via the hydrogen bonding afforded by water. Experimental and calculational evidence also suggest that the degree of polarization in the transition state will determine the magnitude of this solvent effect. Chapter 3 discusses the results of HDPE degradation studies. While HDPE is an extremely stable polymer, exposure to chlorinated aqueous conditions severely reduces the lifetime of HDPE pipes. While much research exists detailing the mechanical breakdown and failure of these pipes under said conditions, a gap still exists in defining the species responsible or mechanism for this degradation. Experimental evidence put forth in this dissertation suggests that this is due to an auto-oxidative process initiated by free radicals in the chlorinated aqueous solution and propagated through singlet oxygen from the environment. A mechanism for HDPE degradation is proposed and discussed. Additionally two small molecules, 2,3-dichloro-2-methylbutane and 3-chloro-1,1-di-methylpropanol, have been suggested as HDPE byproducts. While the mechanism of formation for these products is still elusive, evidence concerning their identification and production in HDPE and PE oligomers is discussed. Finally, Chapter 4 deals with concluding remarks of the aforementioned work. Future work needed to enhance and further the results published herein is also addressed. / Ph. D.

The primary reason for incorporating pigments into plastic materials is to impart the desired colour to finished articles. Some pigments however, may interact with the polymer leading to unexpected deleterious effects. Organic pigments, especially phthalocyanines, are favourable for their brilliant shade but are also well known for causing part distortion or warpage. This causes problems in parts which require good dimensional stability such as crates, containers, trays, caps and closures. Despite that, there are not many published studies on the root cause and mechanism of warpage induced by the pigment. Hence, the objective of this research is to study the influence of such pigments on the dimensional stability, crystallisation behaviour and morphology of polyethylenes in order to have a better understanding on the mechanism of warpage, which could possibly lead to a solution in overcoming this problem.

SOLUTION AND MELT BEHAVIOUR OF HIGH-DENSITY POLYETHYLENE - Successive Solution Fractionation mechanism - Influence of the molecular structure on the flow In the field of polyethylene characterization, one of the most challenging research topic is certainly an accurate molecular structure determination of industrial products, in terms of molar mass distribution (MMD), corresponding average-molar masses and molecular architecture (branching nature, content and heterogeneity). Solution to this long-term problem necessarily calls for a multi-disciplinary approach. Therefore, respective advantages of molecular structure characterization in solution and in the melt are exploited. In solution, chromatographic and spectroscopic methods allow determination of MMD, average branching content and intermolecular heterogeneity within their detection limits. Rheological testing in the melt could be a very powerful molecular structure investigation tool, due to its extreme sensitivity to high molar mass (MM) tailing or long chain branching (LCB) traces. But when the rheological tests results are in hand, we often still wonder what kind of molecular structure gives rise to such results. Indeed, melt signal depends on MM, MMD and LCB presence. MMD determination and LCB quantification by melt approach is impossible as long as respective effects of these molecular parameters are not clearly quantified. The general purpose of the present work is to contribute to a better molecular structure characterization of high-density polyethylene by developing, in a first time, a preparative fractionation method able to provide narrow-disperse linear and long chain branched samples, essential to separate concomitant effects of MM, MMD and LCB on rheological behaviour. Once such model fractions isolated, influence of MM and LCB on both shear and elongational flow behaviours in the melt is studied. /Dans le domaine du polyéthylène, un des sujets de recherche les plus investigués à l'heure actuelle est la détermination précise de la structure moléculaire de résines industrielles, en termes de distribution des masses molaires (MMD), de masses molaires moyennes correspondantes et d'architecture moléculaire (nature, teneur et hétérogénéité). La résolution de cette problématique nécessite une approche multi-disciplinaire, afin d' exploiter simultanément les avantages d'une caractérisation en solution et à l'état fondu. En solution, certaines méthodes chromatographiques et spectroscopiques permettent de déterminer une MMD, une teneur moyenne en branchement et leur distribution, dans leurs limites de détection. La mesure du comportement rhéologique à l'état fondu pourrait s'avérer un formidable outil de caractérisation de la structure moléculaire en raison de son extrême sensibilité à certains détails moléculaires, tels que la présence de traces de LCB ou de très hautes masses molaires (MM). Malheureusement, le signal rhéologique dépend de manière conjointe de la MM, MMD et de la présence ou non de LCB, de telle sorte que la détermination d'une MMD ou d'une teneur en LCB par cette voie est impossible aussi longtemps que les effets respectifs de ces paramètres moléculaires sur le comportement rhéologique n'ont pas été clairement et distinctement établis. L'objectif global de cette thèse est de contribuer à une meilleure caractérisation de la structure moléculaire du polyéthylène haute densité en développant, dans un premier temps, une méthode préparative de fractionnement capable de produire des échantillons, linéaires ou branchés, à MMD la plus étroite possible, indispensables en vue de séparer les effets concomitants de la MM, MMD et LCB sur le comportement rhéologique à l'état fondu. Une fois de tels objets modèles isolés, l'influence de la MM et du LCB sur le comportement rhéologique, en cisaillement et en élongation, sera étudié.

The monomer, p-acryloyloxybenzoic acid (ABA) was synthesized by condensation reaction of acryloyl chloride and p-hydroxybenzoic acid in alkaline medium. Polymerization of the monomer and grafting of the produced polymer (PABA) onto high density polyethylene (HDPE) were expected to be carried simultaneously in melt mixing at high temperature. The graft copolymerization was studied at varying concentrations of the monomer in the reaction mixture at constant temperature (200 0C). Grafted HDPE samples were investigated by several techniques such as DSC, FTIR, MFI and mechanical testing. The tensile tests of PABA-g-HDPE showed an improvement particularly in stress at yield and Young&rsquo / s modulus whereas the strain at break values showed a decrease for all compositions compared to neat HDPE.

The effects of polyethylene, (PE), type, compatibilizer type and organoclay type on the morphology, rheological, thermal, and mechanical properties of ternary low density polyethylene (LDPE), high density polyethylene (HDPE), and linear low density polyethylene (LLDPE), matrix nanocomposites were investigated in this study. Ethylene &ndash / Methyl acrylate &ndash / Glycidyl methacrylate terpolymer (E-MAGMA) and Ethylene &ndash / Butyl acrylate- Maleic anhydrate terpolymer (E-BA-MAH) were used as the compatibilizers. The organoclays selected for the study were Cloisite 30B and Nanofil 8. Nanocomposites were prepared by means of melt blending via co-rotating twin screw extrusion process. Extruded samples were injection molded to be used for material characterization tests. Optimum amounts of ingredients of ternary nanocomposites were determined based on to the mechanical test results of binary blends of PE/Compatibilizer and binary nanocomposites of PE/Organoclay. Based on the tensile test results, the optimum contents of compatibilizer and organoclay were determined as 5 wt % and 2 wt %, respectively. XRD and TEM analysis results indicated that intercalated and partially exfoliated structures were obtained in the ternary nanocomposites. In these nanocomposites E-MA-GMA compatibilizer produced higher d-spacing in comparison to E-BA-MAH, owing to its higher reactivity. HDPE exhibited the highest basal spacing among all the nanocomposite types with E-MA-GMA/30B system. Considering the polymer type, better dispersion was achieved in the order of LDPE&lt / LLDPE&lt / HDPE, owing to the linearity of HDPE, and short branches of LLDPE. MFI values were decreased by the addition of compatibilizer and organoclay to the matrix polymers. Compatibilizers imparted the effect of sticking the polymer blends on the walls of test apparatus, and addition of organoclay showed the filler effect and increased the viscosity. DSC analysis showed that addition of compatibilizer or organoclay did not significantly affect the melting behavior of the nanocomposites. Degree of crystallinity of polyethylene matrices decreased with organoclay addition. Nanoscale organoclays prevented the alignment of polyethylene chains and reduced the degree of crystallinity. Ternary nanocomposites had improved tensile properties. Effect of compatibilizer on property enhancement was observed in mechanical results. Tensile strength and Young&rsquo / s modulus of nanocomposites increased significantly in the presence of compatibilizers.

Polymer pipes, typically high density polyethylene (HDPE), can be pulled-into-place, avoiding traditional cut-and-cover construction, using pipe bursting and horizontal directional drilling (HDD) pipe installation techniques. Of particular interest, are the ground displacements, induced by cavity expansion, associated with these techniques and the strains that develop in existing pipes in response to these displacements. Further, the axial stress-strain response of the new HDPE pipe during and after the cyclic pulling force history required to pull the pipe into place is of interest. Surface displacements and strains in an adjacent polyvinyl chloride (PVC) pipe induced by static pipe bursting were measured during the replacement of a new unreinforced concrete pipe. For the pipe bursting geometry tested, the maximum vertical surface displacement measured at the ground surface was 6 mm, while the distribution of vertical surface displacements extended no more than 2 m on either side of the centreline. The maximum longitudinal strain measured in the PVC pipe was less than 0.1% and its vertical diameter decreased by only 0.5%, suggesting that pipe bursting did not jeopardize the long-term performance of the water pipe tested. In addition, results from identical stress relaxation and creep tests performed on whole pipe samples and coupons trimmed from a pipe wall were compared, and these demonstrated that the coupons exhibited higher modulus than the pipe samples. Therefore, isolated pipe samples, as opposed to coupons, were tested to quantify the stress-strain response of HDPE pipe during the simulated installation, strain recovery, and axial restraint stages of HDD. Axial strains were found to progressively accumulate when an HDPE pipe sample was subjected to the cyclic stress history used to simulate an HDD installation. It was shown that existing linear and nonlinear viscoelastic models can serve as predictive design tools for estimating the cyclic strain history of HDPE pipe during installation. For the specific conditions examined, the tensile axial stresses redeveloped in the pipe samples, once restrained, were not large enough to lead to long-term stress conditions conducive to slow crack growth even when the short-term performance limits were exceeded by a factor of 1.5. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2009-04-01 18:19:24.434

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-26T15:00:31Z No. of bitstreams: 1 RENATA BARBOSA - TESE (PPGEP) 2009.pdf: 13292645 bytes, checksum: e1d1eb846f17881cd108a8bad8f924ec (MD5) / Made available in DSpace on 2018-09-26T15:00:31Z (GMT). No. of bitstreams: 1 RENATA BARBOSA - TESE (PPGEP) 2009.pdf: 13292645 bytes, checksum: e1d1eb846f17881cd108a8bad8f924ec (MD5) Previous issue date: 2009-06-19 / Nanocompósitos de PEAD/argila bentonítica modificada e sem modificação foram preparados por meio do processo de intercalação por fusão. Realizou-se, previamente um estudo sistemático com quatro sais quaternários de amônio e em três tipos de argilas bentoníticas. Em seguida, fez-se a escolha de um sal quaternário de amônio e de uma argila bentonítica para dar continuidade ao trabalho. A argila escolhida foi organofilizada usando-se diferentes percentuais de sal quaternário de amônio 100%, 125% e 150% baseados na capacidade de troca de cátions (CTC) da argila. Ficou evidente por difração de raios- X (DRX) que os sais foram incorporados à estrutura da argila confirmando assim sua organofilização. Em princípio, todos os sais poderão ser usados para a organofilização da argila e, consequentemente nos sistemas de nanocompósitos PEAD/argila organofílica. Porém, foi verificado que o tipo de ânion presente pode influenciar a estabilidade térmica do sal quaternário de amônio. Os nanocompósitos foram preparados em uma extrusora de rosca dupla contrarrotacional e, em seguida, corpos de prova foram moldados por injeção. Para a avaliação da inflamabilidade dos sistemas foi utilizado o teste de queima na posição horizontal segundo a norma (UL-94HB) e o método do Calorímetro de Cone. O comportamento térmico dos nanocompósitos foi avaliado por temperatura de deflexão térmica (HDT) e termogravimetria (TG). As técnicas de DRX e microscopia eletrônica de transmissão (MET) foram utilizadas para caracterizar a morfologia e analisar o grau de expansão das argilas preparadas bem como o grau de esfoliação dos nanocompósitos. As propriedades mecânicas de tração e impacto também foram analisadas. Para efeito de comparação, determinadas composições foram extrudadas utilizando-se duas configurações de roscas da extrusora ZSK-30 corrotacional, com objetivos de variar as condições de processo e melhorar as propriedades dos nanocompósitos obtidos. Observou-se que o percentual de sal de amônio e o tipo de compatibilizante polar influenciam nas propriedades finais dos nanocompósitos. / High Density Polyethylene (HDPE) nanocomposites containing unmodified and modified bentonite clay were prepared by melt intercalation technique. Initially, four quaternary ammonium salts and three types of bentonitic clays were studied. Afterwards, one type of salt and one type of clay were chosen for the study. The clay was organophilized using 100,125 and 150wt% of quaternary ammonium salt based on cationic exchange capacity (CEC) of the clay. It was evident from the X-ray diffraction (XRD) that the salts were incorporated into the clay structure confirming its organophilization. In general, all salts may be used for clay organophilization and hence, on HDPE/Organophilic clay nanocomposites. However, it was verified that the type of anion present may influence the thermal stability of the quaternary ammonium salt. The nanocomposites were prepared in a counter-rotating twin screw extruder and the samples were prepared by injection molding. For the evaluation of the flammability, horizontal burn (UL-94HB) and cone calorimeter methods were used. The thermal behavior of the nanocomposites was analyzed by Heat Distortion Temperature (HDT) and Thermogravimetry (TG). XRD and Transmission Electron Microscopy (MET) techniques were used to characterize the morphology and analyze the degree of expansion of the prepared clays, and also the degree of exfoliation of the nanocomposites. Mechanical properties (Tensile and Impact strength) were also analyzed. Some compositions were extruded using two screw configurations of ZSK-30 co-rotacional extruder with the aim of improving the properties of the nanocomposites obtained by varying the processing conditions. It was observed that the percentage of the ammonium salt and the type of polar compatibilizer influence the final properties of the nanocomposites.

Made available in DSpace on 2016-03-15T19:36:55Z (GMT). No. of bitstreams: 1 Jessyka Meierjurgen Melo.pdf: 1463151 bytes, checksum: b96ae4642ea3139b9e867598e3bba7c1 (MD5) Previous issue date: 2015-06-15 / The present work aimed to highlight the study of polymeric composite development to be responsible with the environment and with the growth of the recycling of materials, from the use of high-density polyethylene (HDPE) with eucalyptus wood dust from the manufacturing furniture. The study started from a literature search where were analyzed the factors involving the subject in question, highlighting the concept of polymer, synthetic fibers, wood dust presence, and composites to identify and understand the problem in issue. Mechanical, morphological and rheological tests were done with composites with concentrations of 5, 10 and 20% of wood dust in relation to the polymer matrix in order to characterize and compare the obtained materials. It was noted that during the study samples with wood dust had higher mechanical performance compared to pure HDPE sample. Based on this context, this study was developed to analyze the possibilities ahead so the production of HDPE composite from different wood dust fractions. / O presente trabalho teve como objetivo destacar o estudo de desenvolvimento de compósito polimérico responsável com o meio ambiente e com o crescimento da reciclagem de materiais, a partir da utilização de polietileno de alta densidade (PEAD) com pó de madeira de eucalipto, proveniente da fabricação de móveis. O estudo iniciou a partir de uma pesquisa bibliográfica onde foram analisados os principais fatores que envolvem o tema em questão, destacando o conceito de polímero, das fibras sintéticas, a presença do pó de madeira, seus compósitos a fim de identificar e conhecer o problema em questão. O estudo desenvolveu-se a partir de ensaios mecânicos, morfológico e reológico, dos compósitos com as concentrações de 5, 10 e 20% de madeira em relação à matriz polimérica, a fim de caracterizar e comparar os materiais obtidos. Notou-se que durante os estudos as amostras com pó de madeira apresentaram maior desempenho mecânico comparado a amostra de PEAD puro. Baseado neste contexto, este estudo foi desenvolvido visando assim analisar as possibilidades frente a produção do compósito de PEAD a partir de diferentes concentrações de pó de madeira.