Structure development in powder processing of polyphenylene sulfide

The thermal and crystallization behavior of polyphenylene sulfide (PPS) in the context of its structure development in solid‐state processing is reported. The solid‐state processing of polymers involves cold compaction of the powder, followed by sintering. Since this process comprises of heat treatment at high temperatures for extended periods, the structure of PPS would be expected to be affected. An attempt has been made to elucidate the effect of compaction and sintering process parameters on the physical and chemical structures of the polymer. The changes in the structure of the polymer were monitored by characterizing its melting and crystallization behavior. It was observed that compaction resulted in changes only in the physical structure, leading to destruction of the smaller/less stable crystallities. The thermal treatment at high temperatures led not only to physical changes involving crystal growth and perfection but also to chemical changes in the structure, resulting in modification of crystallization behavior. The extent of change was found to be different for PPS in the powder form and in the pellet form, which is explained on the basis of the restricted diffusion of air in pellet form as compared to the powder. Such changes observed in the samples were also dependent on the type of sintering medium. The sintering in presence of nitrogen did not show significant changes in the crystallization or melting behavior. Thus, the structure development in solid‐state processing of PPS was influenced by the sintering time, temperature, and sintering medium, leading to physical and/or chemical changes.