Copolyesters were prepared by melt condensation of poly(ethylene terephthalate) (PET) with poly(hexamethylene terephthalate), poly(octamethylene terephthalate), and poly(decamethylene terephthalate). These polymers were characterized by 13C- NMR and intrinsic viscosity measurements. The PET and the copolyesters were spun into fibers using the conventional melt spinning technique. The fibers were drawn to ratios of 3, 4, and 5. Decreases in Tg, Tc, Tm, density, birefringence, crystallinity, and orientation were observed in the copolyester fibers, with an increase in the number of methylene groups in the PET backbone.

Epoxy resins of different molecular weights were prepared from epichlorohydrin and 4,4'-sulfonyldiphenol (SDP) and from epichlorohydrin and bisphenol A (BA). They were cured at high temperatures with four different crosslinking agents, including aliphatic and aromatic amines. The thermal behaviour of these cured epoxy resins was studied. From the IPDT and IDT data it was observed that sulfone epoxy resins were thermally more stable than bisphenol A epoxy resins. The activation energies of thermal degradation of the resins were calculated and the implications of these results are discussed. ZUSAMMENFASSUNG :Es wurden Epoxidharze mit unterschiedlichen Molekulargewichten aus Epichlorhydrin und 4,4'-Sulfonyldiphenol (SDP) und aus Epichlorhydrin und Bisphenol A (BA) hergestellt . Sie wurden bei hohen Temperaturen mit vier verschiedenen Vernetzern, einschlieBlich aliphatischer und aromatischer Amine, gehktet. Das thermische Verhalten dieser geharteten Epoxidharze wurde untersucht. Aus den Zersetzungstemperaturen wurde entnommen, dalj Sulfon-Epoxidharze thermisch stabiler als Bisphe-no1 A-Epoxidharze sind. Die Aktivierungsenergien des thermischen Abbaus dieser Harze wurden berechnet, und die Folgerungen aus diesen Ergebnissen werden diskutiert .

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Copolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (Tg). melting points (Tm) and crystallisation temperatures (Tc) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in Tg, Tm and Tc. The as‐prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation.

The paper describes the effect of structure on moisture regain and dye uptake of copolyester fibers of poly(ethylene terephthalate) and poly(hexamethylene terephthalate), poly(octamethylene terephthalate), and poly(decamethylene terephthalate). The increase in the methylene groups per repeat unit of copolyesters resulted in an increase in moisture regain and dye uptake. The diffusion coefficient values for dye uptake in copolyester fibers containing decamethylene groups were exceptionally high.Water absorption and dyeability are important fiber properties that depend on the chemical nature and the fine structure of the fiber. The main factors governing , the dyeing behavior of polymers are crystallinity, orientation, and size of crystalline region, as well as the mobility of the polymer chains characterized by the glass transition temperature. Thus the total number of amorphous regions and the accessibility of these regions control the dye uptake and moisture absorption in hydrophobic fibers such as poly(ethylene terephthalate) [2].In our earlier papers, we have reported the changes in the Tg, T & d q u o ; & d q u o ; and fine structure of PET by incorporating a low mole fraction of a comonomer in the backbone [5,6,7,8,9,11 ]. The comonomer unit disturbs the packing of molecular chains, thereby decreasing the crystallinity and orientation and increasing the amorphous regions. Copolymerization is a convenient way for improving the dyeability and moisture regain of PET. Several attempts have been made to add a comonomer as a block or in a random manner [1,3,4, 10] to obtain better properties in polymers. In this paper we report the changes in the dyeability and moisture sorption of PET by the incorporation of poly(alkylene terephthalate) units in the backbone. Six copolyester samples were prepared by melt fusion of high molecular weight PET with oligomeric poly-(hexamethylene terephthalate) (PHT), poly(octamethylene terephthalate) (POT), and poly(decamethylene terephthalate) (PDT). The backbone structure of these copolyesters can be depicted as where m = 6 (FH) or 8 (FO) or 10 (FD). (Figures in parentheses indicate the letter designations for these copolyesters.) The copolyesters were prepared by melt fusion of 0.05 mole fraction of PHT/POT/PDT (samples FHI/ / FO,/FD,) with PET. Samples FH2 and F02 were obtained by melt fusion of 0.07 mole fraction of PHT/ POT with PET, while sample FH3 was prepared by melt fusion of 0.10 mole fraction of PHT with 0.9 mole fraction of PET. The details of preparation and characteristics of these copolyesters and of their spinning into fibers have been reported elsewhere [7].Experimental ' Moisture regain of 5DR heat set copolyester fibers was measured by the vacuum desiccator method. Relative humidities of 65 ± 2% and 84 ± 2% were maintained using saturated salt solution. The fibers were kept for 48 hours at these humidities and then weighed. The dry weight of the fibers was obtained by placing in a vacuum desiccator over phosphorus pentaoxide for 5 days till a constant weight was ...