No abstract

Correlation between hydrogen-bonding self-association and sequence distribution in poly(vinyl acetate-co-vinyl alcohol) copolymers (ACA) with different degrees of basic hydrolysis and sequence distributions has been studied by thermal analysis and NMR spectroscopy. 13C NMR spectroscopy has also been used to elucidate the blocky nature, branching, and tacticity of the copolymers. Thermal analytical studies indicate that hydrogen bonding distribution in block alcohol and vinyl acetate copolymers strongly depend on the sequence distribution wherein hydroxyl-hydroxyl self-association is preferred.

SYNOPSISFilms of high-density polyethylene (HDPE) have been sulfonated by solid-gas phase reaction using gaseous sulfur trioxide (SO,) of different concentrations in nitrogen. The effect of concentration of SO3 in an SO3 + N2 gas mixture and time of sulfonation on solvent and gas barrier properties of sulfonated HDPE films was studied by determining toluene and oxygen permeability of HDPE films sulfonated with different concentrations of SO3 for different times. The color developed in sulfonated HDPE films during sulfonation could be bleached by aqueous sodium hypochloride solution. The effect of sodium hypochloride solution treatment on oxygen permeability of sulfonated HDPE films was also studied.

Correlation between hydrogen‐bonding self‐association and sequence distribution in poly(vinyl acetate‐co‐vinyl alcohol) copolymers (ACA) with different degrees of basic hydrolysis and sequence distributions has been studied by thermal analysis and NMR spectroscopy. 13C NMR spectroscopy has also been used to elucidate the blocky nature, branching, and tacticity of the copolymers. Thermal analytical studies indicate that hydrogen bonding distribution in block alcohol and vinyl acetate copolymers strongly depend on the sequence distribution wherein hydroxyl–hydroxyl self‐association is preferred. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 123–133, 1999

ABSTRACT:In a study of the surface morphology of commercial poly(vinyl acetate-co-vinyl alcohol) (ACA copolymer) with different percents of hydrolysis, different structures like fibrils, spherulites, micelles, vesicles, and spheroids were seen. The copolymer was crystallized by annealing at two different temperatures. The morphology of the polymer after crystallization and also without crystallization was studied. A decrease in the melting temperature just by heating to the melting temperature was observed, and for a detailed study, repetitive heating of the copolymer was carried out and changes in the mass and heat of fusion after every heating was recorded. The morphology of the copolymer after repetitive heating was studied.

The degradation behaviour of Kodar [poly(1,4‐cyclohexylene dimethyl‐eneterephthalate)] was investigated in air using thermogravimetry, differential thermal analysis and wide angle X‐ray diffraction studies. The rates of crystallization and degradation were influenced by thermal exposure and polychromatic irradiation (Λ > 290 nm) for different time intervals. The crystallinity changes (Xc%) and activation energies (ΔE) for the systems have been determined.