Studies of the Thermal Stability and Degradation Mechanisms of Terephthalate Polyesters and Telechelic Poly(Methyl Methacrylates)

The preparation of polymers of improved stability requires an understanding of the relationship between structure and mechanism of decomposition. In this project, this relationship is explored for several classes of polymer. The main degradation techniques which have been used, described in Chapter 2, are thermogravimetry (TG), thermal volatilisation analysis (TVA) and differential thermal analysis (DTA). Degradation products have been separated and analysed using subambient TVA, and GC-MS, IR and MS spectroscopy. The preparation and spectroscopic analysis of poly(alkylene terephthalates), poly(ether-esters), polyarylates and alpha,o-bifunctional poly(methyl methacrylate) described in Chapter 3. In Chapters 4 and 5,studies of the thermal degradation of poly(alkylene terephthalates) and poly(ether-esters) made by melt polymerisation of terephthaloyl chloride with aliphatic diols and poly(ethylene glycols) (Mw 200, 1000) are reported. In order to achieve a detailed analysis of the degradation products, both temperature programmed and isothermal experiments were performed on these polymers. From the results obtained, the general mechanism of decomposition has been established. In Chapter 6, a similar investigation of nine different polyarylates, including fire retardant polyarylates, made by interfacial polycondensation from aromatic diols and terephthaloyl chloride is reported and the effects of fire retardant incorporated to the backbone of polymer are discussed. It is clear there are many close similarities in mechanism, especially in the sense that similar radicals are usually involved. In Chapter 7, the results of a comprehensive study of the thermal degradation of four different o,o-bifunctional poly(methyl methacrylates) made by the anionic route are analysed and the general mechanism of decomposition has been proposed. The effect of the functional end groups on the thermal stability and mechanistic behaviour are discussed

Iterative Schemes for Nonconvex Quasi-Variational Problems with V

In this paper, we propose an extension of quasi-equilibrium problems from the convex case to the nonconvex case and from Hilbert spaces to Banach spaces. The proposed problem is called quasi-variational problem. We study the convergence of some algorithms to solutions of the proposed nonconvex problems in Banach spaces

Iterative Schemes for Nonconvex Quasi-Variational Problems with V-Prox-Regular Data in Banach Spaces

In this paper, we propose an extension of quasi-equilibrium problems from the convex case to the nonconvex case and from Hilbert spaces to Banach spaces. The proposed problem is called quasi-variational problem. We study the convergence of some algorithms to solutions of the proposed nonconvex problems in Banach spaces

Existence Results for Second Order Nonconvex Sweeping Processes in q-Uniformly Convex and 2-Uniformly Smooth Separable Banach Spaces

We prove an existence result, in the separable Banach spaces setting, for second order differential inclusions of type sweeping process. This type of differential inclusion is defined in terms of normal cones and it covers many dynamic quasi-variational inequalities. In the present paper, we prove in the nonconvex case an existence result of this type of differential inclusions when the separable Banach space is assumed to be q-uniformly convex and 2-uniformly smooth. In our proofs we use recent results on uniformly generalized prox-regular sets. Part of the novelty of the paper is the use of the usual Lipschitz continuity of the set-valued mapping which is very easy to verify contrarily to the ones used in the previous works. An example is stated at the end of the paper, showing the application of our existence result

Physicochemical properties and biological activities of novel blend films using oxidized pectin/chitosan

International audiencePectin has been widely used in a variety of biomedical applications. In this study, it was modified with sodium periodate as an oxidant and characterized by physicochemical methods Periodate oxidation increased the contents of dialdehyde units and carboxyl groups in pectin, and a decrease in pectin viscosity was measured. The oxidization reaction led to a significant decrease in all values of molecular weight and size (Mn, Mw, [η] and Rh) as determined by size exclusion chromatography (SEC), which allowed the selection of the oxidized pectin to be added to chitosan. Chitosan-based films were characterized by infra-red spectroscopy (FTIR), X-ray diffractometry (XRD), and differential scanning calorimetry (DSC) measurements. Thermal behaviour studies demonstrated that interactions existed between chitosan and oxidized pectin. The haemolysis percentages of films were found to be less than 5%, which indicated their good blood compatibility. Finally, the antibacterial activity was clearly improved. Cross-linking reactions between pectin and chitosan through ionic bonds and amide bonds and between chitosan and oxidized pectin through Schiff base formation were evidenced, which opens the way to extend applications of these polysaccharides; notably, the biocompatibility and biodegradability of these new networks is convenient for pharmaceutical, biomedical or cosmetic applications

Thermal characterization of polyester-melamine coating matrices prepared under nonisothermal conditions

Thermal analysis methods (differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis) were used to characterize the nature of polyester-melamine coating matrices prepared under nonisothermal, high-temperature, rapid-cure conditions. The results were interpreted in terms of the formation of two interpenetrating networks with different glass-transition temperatures (a cocondensed polyester-melamine network and a self-condensed melamine-melamine network), a phenomenon not generally seen in chemically similar, isothermally cured matrices. The self-condensed network manifested at high melamine levels, but the relative concentrations of the two networks were critically dependent on the cure conditions. The optimal cure (defined in terms of the attainment of a peak metal temperature) was achieved at different oven temperatures and different oven dwell times, and so the actual energy absorbed varied over a wide range. Careful control of the energy absorption, by the selection of appropriate cure conditions, controlled the relative concentrations of the two networks and, therefore, the flexibility and hardness of the resultant coatings. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Cbem 41: 1603-1621, 2003