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Good extrusion foaming performance of long‐chain branched PET induced by its enhanced crystallization property
Author(s) -
Yao Shun,
Guo Tianhao,
Liu Tao,
Xi Zhenhao,
Xu Zhimei,
Zhao Ling
Publication year - 2020
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.49268
Subject(s) - materials science , crystallization , reactive extrusion , extrusion , nucleation , supercritical fluid , blowing agent , branching (polymer chemistry) , chemical engineering , rheology , pyromellitic dianhydride , oligomer , polymer chemistry , composite material , chemistry , organic chemistry , polyimide , layer (electronics) , polyurethane , engineering
Poly(ethylene terephthalate) (PET) was modified by regulating different contents of branching agent epoxy‐based multifunctional oligomer and chain extender pyromellitic dianhydride in reactive extrusion process. The modified PET with better long‐chain branched (LCB) structure boosted its rheological properties, and its enhancement of melt viscoelasticity resulted in excellent foamability in molten‐state foaming process using supercritical CO 2 as blowing agent. More importantly, the branched structures acted as crystal sites to accelerate the crystallization kinetic of LCB PET whether under atmospheric pressure or high‐pressure CO 2 . The shear and elongation flow inside die further quickly induced the crystallization of LCB PET. The rapidly generated fine crystals could both introduce heterogeneous cell nucleation and suppress CO 2 escape, so the cell morphology of LCB PET in continuous extrusion foaming process exhibited a three‐fold increase in cell density and smaller uniform cell size with respect to those of other foam‐grade PET with long‐chain structure.