SUPERCRITICAL ANTISOLVENT PROCESS FOR SUBSTITUTED PARA-LINKED AROMATIC POLYAMIDES - PHASE-EQUILIBRIUM AND MORPHOLOGY STUDY

Poly crystalline spherulites and microfibrils are obtained from a subs tituted para-linked aromatic polyamide in a supercritical antisolvent (SAS) process. Carbon dioxide is contacted with 0.03-0.12 wt % polymer in dimethyl sulfoxide and in N,N-dimethylformamide solutions in both batch and continuous modes of operation. Slow expansion of the solutio n produces polycrystalline spherulites in the 1-10 mum-diameter range, and the degree of crystallinity is affected by turbulence caused by c arbon dioxide injection. A microfibrillar structure is obtained by spr aying the polymer solution through a small orifice into cocurrently fl owing supercritical carbon dioxide. This morphology is suggestive of s hear-induced chain orientation during nucleation. In addition, phase b oundaries of the polymer + solvent + antisolvent ternary and the solve nt + antisolvent binary systems are determined up to 120-degrees-C and 300 bar.