Th.--Sci. phys.--Lille 1, 1977. N°: 401.

No description available.

Bicomponent fibers consisting of nylon-6 and isotactic polypropylene were produced. In-situ, reactive compatibilization was achieved using a maleic anhydride functionalized polypropylene between the materials at the interface. The overall goal of the research was to produce a bicomponent fiber of these materials that would be suitable for use in commercial carpet applications. Carpet samples produced using nylon-6 core / polypropylene sheath bicomponent fibers displayed stain resistance comparable to a wholly polypropylene carpet. The wear characteristics of these fibers were found to be strongly dependent upon the maleic anhydride content and the molecular weight of the maleic anhydride functionalized polypropylene. Adhesion between the nylon-6 and polypropylene phases, and the mechanical properties of the polypropylene phase were affected by the addition of the functionalized polypropylene. Additional information regarding the processing conditions necessary to produce fibers of the desired cross-section from these materials was obtained using capillary rheometry. A number of analytical techniques including DSC, TGA, and SEM were used to better understand the structure of the maleated materials. / Master of Science

No description available.

Currently, extensive research in using bio‐derived polymers is being done, highlighting the importance of sustainable, green polymeric materials. Some sustainable alternatives to synthetic polymers include lignin, starch, cellulose or blends of these with petroleum‐based polymers. In New Zealand, large quantities of animal derived proteins are available at very low cost, making it ideal as a sustainable alternative to petroleum‐derived polymers. However, the processability of most proteins is very difficult, but can be improved by blending with synthetic polymers, such as polyolefins. To improve, the compatibility between these substances, a functional monomer could be grafted onto the polyolefin chain. Using an appropriate functional group, the polyolefin could then react with certain amino acids residues in the protein. Lysine and cystein are the two most appropriate amino acid residues because of their reactivity and stability at a wide pH range. In this study, free radical grafting of itaconic anhydride (IA) onto polyethylene was investigated. IA was selected because it is capable of reacting with polyethylene and amino acid residues, such as lysine. The objective of the research was to identify and investigate the effect of reaction parameters on grafting. These were: residence time, temperature, initial monomer concentration as well as peroxide concentration and type. Grafting was characterized in terms of the degree of grafting (DOG), percentage reacted and the extent of side reactions. The reaction temperature was taken above the melting point of the polyethylene, monomer and decomposition temperature of the initiator. It was found that above 160 C polymer degradation occurred, evident from sample discolouration. A higher degree of grafting can be achieved by increasing the initial monomer concentration up to a limiting concentration. The highest DOG achieved was about 1.2 mol IA per mol PE, using 2 wt% DCP. When using 2 wt % peroxide, the limiting concentration was found to be 6 wt% IA, above which no improvement in DOG was achieved. It was found that DCP is much more effective at grafting, compared to DTBP because DTBP is more prone to lead to side reactions than DCP. iv It was found that a residence time of 168 seconds resulted in the highest DOG, corresponding to 4 extrusions in series. However, it was also found that an increase in residence time resulted in an increase in polymer degradation. The tensile strength of PE decreased after two extrusions when using DTBP, and three extrusions, when using DCP. Young's modulus decreased only slightly, while all samples showed a dramatic decrease in ductility, even after one extrusion. It was concluded that degradation had a more pronounced effect on mechanical properties than cross‐linking, and residence time should therefore not exceed three extrusions in series, which corresponded to about 126 seconds. It can be concluded that a high reaction temperature and high initiator concentration lead to a low degree of grafting, accompanied by high cross‐linking and increased degradation. On the other hand, high monomer concentration and high residence time lead to a high degree of grafting. Optimising grafting is therefore a trade off between maximal DOG and minimising side reactions such as cross‐linking and degradation and optimal conditions do not necessarily correspond to a maximum DOG. Other factors, such as the use of additives to prevent degradation should also be investigated and may lead to different optimum conditions.

Includes bibliographical references (leaves 43-46; leaves 52-55). / v, 55, leaves

Epoxy resins are widely used as coatings, encapsulations, structural composites, castings, and adhesives in a number of electrical applications. Recently, novel uncatalyzed co-anhydride cured epoxy formulations that exhibit a high performance property profile, have been introduced. The objective of this thesis was to perform a comprehensive material characterization of these new resin/hardener combinations, which are potentially used as electrical insulation material in medium and high voltage engineering. The thermal cure behaviour of commercial tetraglycidyl-diamino-diphenylmethane (TGDDM) and a co-anhydride mixture consisting of maleic anhydride (MA) and hexahydrophthalic anhydride (HHPA) was extensively studied. Different analytical real-time methods, such as FT-Raman spectroscopy, differential scanning calorimetry, and chemo-rheological methods were applied to investigate the principal polymerization mechanism and the related curing kinetics. It was demonstrated that kinetic parameters that were based on isothermal measurements provided consistent and reliable results. On the other hand the general limitations of different dynamic methods for kinetic parameter calculations were outlined and discussed. Temperature modulated differential scanning calorimetry provided a powerful technique to confirm a TGDDM/MA and TGDDM/HHPA sub-network structure of the co-anhydride cured epoxy. A generalized time-temperature-transformation-diagram was developed in order to predict the complex material transformations (e.g. gelation and vitrification) occurring during the entire isothermal curing process. In the selected system, the mechanical deformation and fracture behaviour as a function of temperature, strain rate, inorganic filler fraction, particle size, and filler/matrix-adhesion were thoroughly studied by using compression-, tension- and double torsion fracture-tests. The potential of hyperbranched polymers (HBPs) as low viscosity toughening modifiers for highly crosslinked anhydride-cured epoxy networks was experimentally evaluated. The effects of the HBP molecular structure, in particular the specific shell chemistry, on thermo-mechanical properties, final morphology, and blend concentration, were assessed. For the neat investigated epoxy-system the most efficient toughening modifier was obtained for a molecular HBP-design that provided a pseudo-homogeneous blend morphology. Thus, by using suitable HBPs in a concentration of 20% w/w, the fracture toughness, expressed by the critical stress intensity factor (Klc) of 0.58 MPam(to the power of)0.5, was increased by over 50% to 0.88 MPam(to the power of)0.5. The corresponding Young's modulus and glass transition temperature were only affected to a limited extent by the addition of the HBP-additive. The toughest epoxy blend (critical stress intensity factor of about 1.6 MPam(to the power of)0.5) was achieved by the incorporation of 60% w/w inorganic silica particles. The application of hybrid concepts by utilizing synergistic toughening mechanisms (HBP and silica), revealed only moderate benefits within the investigated highly crosslinked materials. As the examined epoxy/anhydride formulations are generally considered for high temperature applications, it was essential to determine their long-term thermooxidative ageing performance. The long-term thermo-oxidative ageing behaviour has been investigated by means of thermo-gravimetric analysis (TGA), dynamic mechanical analysis (DMA) and vibrational infrared spectroscopy (FT-IR) methods with special emphasis on fundamental understanding of the ageing mechanism. Effects of the thermal ageing on the characteristic viscoelastic and flexural behaviour, weight-loss and oxidation susceptibility of the examined epoxy networks were assessed and discussed, thus providing an understanding of the principal material endurance properties. The thermo-mechanical behaviour and the related structural changes with thermal ageing were examined by Cole-Cole plots in combination with a molecular theory previously developed by Perez. It was demonstrated that this new methodology provides a connection between conversion, glass transition temperature, and mechanical relaxation data and allows a fundamental molecular interpretation with respect to physical and chemical ageing phenomena. A variety of thermo-gravimetric experiments were carried out in order to determine and model the specific weight-loss profile as a function of anhydride nature and ageing temperature. The influence of different inorganic fillers on the thermooxidative response was systematically studied. Different models were applied to extract meaningful kinetic parameters in order to describe the thermo-oxidative degradation and to facilitate an extrapolation of weight-loss data outside the experimental time- and temperature-scale. FT-IR micro ATR-spectroscopy was used to identify, localize and quantify the complex oxidation behaviour. A thermo-oxidative degradation mechanism, that involved predominantly radical oxidation processes and C-N as well as C-O chain scissions, was proposed to account for the experimental observations. Specific oxidation-front profiles were constructed to describe the heterogeneous oxidation processes. Finally, the comprehensive material characterization of these novel co-anhydridecured amino-glycidyl resins in terms of curing mechanism and kinetic, deformation and fracture behaviour, and thermo-oxidative ageing performance, allows the assessment of the potential of these materials for demanding applications in electrical and electronic industries.

Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2009. / Vita. Includes bibliographical references.

No description available.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.