Long chain branched poly(butylene succinate-co-terephthalate) copolyesters using pentaerythritol as branching agent: Synthesis, thermo-mechanical, and rheological properties

摘要

Incorporating long chain branching (LCB) structure into biodegradable copolyesters can effectively improve their melt strength and film blowing processability. However, branching also results in deterioration of crystallizability which is also important for copolyester properties and processing. In this study, pentaerythritol (PER) was used as branching agent (BA) instead of previous used in-situ BA, diglycidyl 1,2,3,6-tetrahydrophthalate (DGT), to synthesize LCB poly(butylene succinate-co-terephthalate) (PBST) copolyesters. The chain structure was characterized and the effects of branching on thermal transition, mechanical, and rheological properties were investigated. Similar to DGT, copolymerizing small amount of PER (0.1-0.4 mol %) generates LCB structure and, therefore, improves the melt elasticity or strength and tensile modulus but reduces the elongation at break. Differing from DGT, PER showed higher branching efficiency, and PER-branched PBSTs exhibited unchanged or even improved crystallization ability compared with linear PBST. The improved melt strength coupled with good crystallizability will endow PER-branched PBSTs with better film blowing processability. (C) 2016 Wiley Periodicals, Inc.