支化(高分子化学)
聚合
结晶度
结晶
材料科学
层状结构
成核
高分子化学
化学工程
聚乙烯
退火(玻璃)
聚合物
聚合度
化学
复合材料
有机化学
工程类
作者
Jing‐Gang Gai,Sijia Zhu,Jian Kang,Ya Cao,Ming Xiang
标识
DOI:10.1080/00222348.2011.629900
摘要
In the present study, we investigated the influences of polymerization and crosslinking technologies on the branched-chain structures, crystallization behaviors, and gel networks of two types of low-density polyethylenes, LDPE1 and LDPE2, polymerized under different polymerization conditions in commercial large-capacity production lines. High temperature 13C NMR analysis suggests that the molar contents of both long-chain branches and short-chain branches of LDPE2 were markedly higher than those of LDPE1 due to a higher polymerization temperature for LDPE2. The high content of chain branches of LDPE2 leads to its relatively higher storage modulus, entanglement density, and gel content, as indicated by dynamic mechanical analysis. In addition, when the crosslinking temperature reached 180°C, the LDPE2 crosslinked with 2 wt% dicumylperoxide (XLPE2-D2) displayed a relatively wider processing time window and a faster crosslinking rate than XLPE1-D2. Successive self-nucleation and annealing fractionation indicated that increasing the concentration of dicumylperoxide can improve the crosslinking degree, but resulted in lower crystallinity and thinner lamellar crystals.
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