Dynamic birefringence and dynamic mechanical studies on acrylonitrile copolymers

Dynamic birefringence and dynamic mechanical studies have been done on (i) acrylonitrile/methyl acrylate copolymer and (ii) rubber‐modified copolymer, in the frequency range of 0.06–5.55 Hz (acrylonitrile/methyl acrylate copolymer only at 0.92 Hz) and temperature range of −85 to +85°C. These studies were made on a computerized dynamic birefringence apparatus. A comparison of the dynamic birefringence and dynamic mechanical properties in the rubber‐modified copolymer reveals a rubber glass transition peak, which is much more pronounced in dynamic birefringence data than in dynamic mechanical data. In addition to the glass transition of the rubber part in the rubber modified copolymer, there is a main transition of the copolymer in the vicinity of 80°C. Before the main transition there is a shoulder in the mechanical and optical loss curves. The reasons for the occurrence of the shoulder are discussed.