长支链聚乳酸与凝胶成核剂共混物的结晶行为

Crystallization of Long Chain Branched Poly( lactic acid) with Nucleating Agent

在聚乳酸中引入长支链结构季戊四醇三丙烯酸酯(PETA),并与成核剂1,3∶2,4-二苯亚甲基山梨醇(DBS)/聚乙二醇(PEG)凝胶混合,研究了聚乳酸的结晶行为.结果表明,加入成核剂后长支链聚乳酸的结晶速率加快,在熔体降温过程中即发生结晶,起始结晶温度高于130℃,在升温过程中的冷结晶消失,于125℃等温结晶的半结晶时间小于1 min.结晶速率加快的原因是成核密度的大幅度增加,这主要是DBS纳米纤维的成核作用、产生长支链的PETA与DBS纤维的氢键相互作用以及PEG增塑作用相互协同的结果.

The crystallization behavior of poly （lactic acid） （PLA） was investigated. It was found that the crystallization rate of PLA was increased by induced long chain branching structure （LCB） with pentaerythritol triacrylate （PETA） and additional dibenzylidene sorbitol （ DBS ）/poly （ ethylene glycol ） （ PEG ） （ DBS/PEG ） gel nucleating agent. There is obvious exothermic peak on the cooling curve but no cold crystallization peak appears on the second heating curve. The crystallization onset temperature is higher than that of 130 ℃ during cooling and the haft-crystallization time under isothermal condition at 125 ℃is less than 1 rain. The signifi- cant increase of nucleation density is the reason for fast crystallization, which is ascribed to the cooperative effect of the nucleating effect of DBS nanofibrils, the plasticizing effect of PEG in the gel, and the strong hydrogen bonding interaction between PETA molecules and DBS nanofibfils.