Crystallization, Melting and Morphology of Syndiotactic/Atactic Polystyrene Blends: Molecular Weight Effects of Atactic Polystyrene

✍ Scribed by Chi Wang; Ming-Ling Wang; Yong-Da Fan

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 304 KB
• Volume: 206
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200500116

✦ Synopsis

Abstract

Summary: Molecular weight (MW) effects of atactic polystyrene (aPS) on the morphologies and crystallization kinetics of syndiotactic polystyrene (sPS) blends have been investigated, and miscibility was confirmed for all the sPS/aPS blends. Addition of aPS(M) or aPS(L) leads to a significant increase in the entropy of mixing and gives rise to a pronounced decrease in the equilibrium melting temperature of the blends. On heating from the glassy state, the crystallization peak temperature of the sPS/aPS(H) blend increased with increasing aPS content due to a dilution effect, whereas those of sPS/aPS(M) and sPS/aPS(L) decreased mainly due to enhanced chain mobility. On cooling from the melt state, the crystallization peak temperature decreased with increasing aPS content regardless of the aPS MW. A higher activation energy is required for the sPS component transport from the miscible melt to the growth front in the sPS/aPS(L), suggesting that extra energy is required for the demixing process. Interspherulitic segregation of aPS diluents was evident in the sPS/aPS(L) blends, while interfibrillar segregation morphology was obtained in the sPS/aPS(H) as well as the sPS/aPS(U) blends.

SEM images of sPS/aPS blends 50/50(L) at 230 °C (C) and 70/30(L) at 250 °C (D).

magnified imageSEM images of sPS/aPS blends 50/50(L) at 230 °C (C) and 70/30(L) at 250 °C (D).