A new acid absorbent of calcium hydride was used in the synthesis of high molecular weight poly(p-phenylene terephthalamide) (PPTA) and compared with the traditional acid absorbent of pyridine.Pyridine utilized as acid absorbent in terephthaloyl chloride and p-phenylenediamine condensation polymerization is helpful to get high molecular weight product

however

it is difficult to separate pyridine with other agents in further agent recycling process

which is unacceptable in PPTA industrial production.This work investigates the effect of calcium hydride replacing pyridine as acid absorbent on the PPTA synthesis process and the chemical structure of resulted PPTA.Multiple instrumental measurements such as element analysis

Fourier transform infrared spectrometry(FTIR)

X-ray diffraction(XRD) and thermogravimetric analysis (TGA) were carried out in the characterization of the yielded products.Inherent viscosity data showed that high molecular weight PPTA could be obtained with calcium hydride as acid absorbent.On the other hand

there existed an optimum addition amount of calcium hydride at which high molecular weight PPTA with inherent viscosity high over 6.5 could be obtained.Element analysis

infrared spectroscopy and XRD gave that no difference in element content

molecular structure and crystal structure could be recognized from the products using the two acid absorbents.TGA curves showed that the products using both acid absorbents degraded at approximately 550℃.All the results demonstrate it is feasible to synthesize high molecular weight PPTA using calcium hydride as acid absorbent in large scale production of PPTA.