CYCLIZATION REACTION OF POLYACRYLONITRILE AND POLY(STYRENE-CO-ACRYLONITRILE) STUDIED BY PVT MEASUREMENTS

Pressure, volume, temperature (PVT) measurements reveal that during th e intramolecular cyclization reaction of poly(acrylonitrile) (PAN) and poly(styrene-co-acrylonitrile) (SAN) the volume decreases. This volum e contraction becomes smaller with increasing styrene content in the r andom copolymers and should be related to the simultaneous decrease of longer acrylonitrile home-sequences. The onset temperature of the cyc lization reaction is raised with higher styrene contents in the random copolymers. Thus, it can be excluded that the cyclization reaction ha s a major influence on the discoloration process of SAN samples having relatively small acrylonitrile contents (less than 50 mol-%) during t hermal annealing below 300 degrees C.