THERMAL-STABILITY AND DEGRADATION OF AROMATIC POLYAMIDES .1. PYROLYSIS AND HYDROLYSIS PATHWAYS, KINETICS AND MECHANISMS OF N-PHENYLBENZAMIDE

A kinetic study of the reaction of N-phenylbenzamide neat and in the p resence of added water was carried out to resolve the contributions of homolytic and hydrolytic degradation mechanisms. N-Phenylbenzamide wa s reacted at 425-degree-C in the presence of added water in molar rati os of 0:1, 25:1 and 50:1. Two competing reactions occurred during the reaction of N-phenylbenzamide in water. Neat pyrolysis led to aniline and 1,2-diphenylbenzimidazole as major products, benzene, benzimidazol e, benzoic acid and benzonitrile as minor products, and high molecular weight material. The product recovery index showed that the selectivi ty to high molecular weight material during neat pyrolysis was high. H ydrolysis led to benzoic acid, aniline, benzaldehyde, and benzene whic h were easily recoverable and quantifiable products. The product recov ery index was essentially 1.0 when the molar ratio H2O:NPB was 50:1. T he conversion of the reactant dramatically increased with the addition of water as did the selectivity to aniline and benzoic acid. A superp osition of free-radical and hydrolysis elementary steps rationalized b oth the temporal variations of the product yields and the variation of the product recovery index as a function of water loading.