Molecular composites of poly(p-phenylene benzobisthiazole) with thermoplastics: coagulation studies

Abstract

The solubility limits of solutions of poly (p-phenylene benzobisthiazole) (PBZT), poly(ether-ether-ketone), and two nylons (du Pont, Zytel®42 and Zytel®330) in methane sulphonic acid (MSA) were determined by turbidimetric titration with water. The solubilities rank as follows: Zytel®42 > Zytel®330 > PEEK > PBZT. The coagulation of solutions of these polymers was examined in two limiting case: very slow (exposure to water vapour) and very fast (immersion in a water bath) coagulation rates. The slow coagulation of ternary solutions shows that PBZT may either precipitate first from the composite solutions or coprecipitate with the thermoplastic depending on their relative solubility. The immersion coagulation process can be described by a simple diffusion model and the diffusion coefficient of water in the polymer solution is determined to be on the order of 10−5 cm2s−1. Our results suggest that PBZT will coagulate first from ternary solutions of PBZT, nylon, and MSA during wet-spinning, resulting in a continuous microfibrillar network structure of PBZT followed by the precipitation of nylon.