Study of multiple melting behaviour of syndiotactic polystyrene in beta-crystalline form

A series of syndiotactic polystyrene (SPS) samples in beta -crystalline for m were prepared by cooling from the melt at various rates. The effects of c ooling rate from the melt, DSC heating rate and annealing on the multiple m elting behaviours of beta crystals were investigated by differential scanni ng calorimetry (DSC) and temperature modulated differential scanning calori metry (TMDSC), from which the nature of the multiple melting behaviour was determined. The two melting endotherms of beta -form crystals were consider ed to arise from the occurrence of simultaneous melting, recrystallization and remelting processes in the melting region. It is suggested that the low er melting endotherm is due to the melting of imperfect beta crystals origi nally present in the sample, whereas the higher melting endotherm comes fro m the melting of recrystallized SPS crystals, ie more perfect beta crystals that formed during the DSC scanning process. (C) 2000 Society of Chemical Industry.