Preparation of poly(p-phenylene terephthalamide) in a microstructured chemical system

Abstract

A microstructured chemical system, mainly including a micro-sieve mixer, a delay loop and a stirring tank, was designed to implement the polycondensation of p-phenylenediamine (PPD) and terephthaloyl chloride (TPC) for the preparation of poly(p-phenylene terephthalamide) (PPTA). A two-step method was exhibited, which consisted of fast conversion of more than 90% of the reactive groups in the delay loop and further chain growth in the stirring tank. This new polycondensation method had several advantages, such as continuous operation at higher temperature and out of pyridine, which made the process more controllable and environmentally friendly. PPTA particles with a weight-average molecular weight (M_W) from 4000 to 16 000 were obtained at different synthesis conditions, and their structures were characterized by XRD, POM, IR, EA and SEM. The apparent reaction kinetics in the delay loop was also studied, which showed that the apparent activation energy was 12 kJ mol⁻¹ with a pre-exponential factor of 5.4 × 10³ L (mol⁻¹ s⁻¹).