纤维素接枝共聚物对聚乳酸结晶性能和拉伸流变性能的影响

Effect of Cellulosic Graft Copolymer on Crystallization and Extension Rheology Properties of Polylactic Acid

通过熔融缩聚法制备出含有聚乳酸支链的纤维素接枝共聚物(OLA-g-C),并采用溶液共混法制备一系列聚乳酸(PLA)/OLA-g-C共混物以及对比样聚乳酸/微晶纤维素(MCC)共混物.扫描电镜(SEM)结果表明聚乳酸支链的存在可以提高纤维素在PLA基体中的分散性,抑制团聚现象的出现.在非等温结晶过程中,OLA-g-C和MCC的加入都可以促进PLA的结晶,但是OLA-g-C的促进效果优于MCC,这与OLA-g-C在基体中的分散性良好有关.在等温结晶过程中OLA-g-C可以同时提高PLA的结晶度以及结晶速率,但对其成核机理和生长方式无明显影响.偏光显微镜(POM)观察的结果进一步证明OLA-g-C可以作为成核剂,有效地缩短基体的结晶时间,提高PLA的结晶能力.但是,OLA-g-C的加入却降低了体系的拉伸黏度,这与体系的缠结作用有关.

The polylactic acid （PLA） grafted cellulose copolymer （OLA-g-C） was synthesized by melt copolycondensation of lactic acid with microcrystalline cellulose （MCC）, then PLA/OLA-g-C blends and contrast samples PLA/MCC blends were prepared by solution mixing. The results of scanning electron microscopy （SEM） showed that the existence of PLA side chains improved the dispersion of cellulose in PLA matrix and inhibited the agglomeration. In non-isothermal crystallization process, OLA-g-C and MCC both promoted the crystallization ability of PLA,but the promotion effect of OLA-g-C was better than MCC due to the well dispersion of OLA-g-C in PLA matrix. In isothermal crystallization process, OLA-g-C can accelerate the crystallization rate and improve the erystallinity simultaneously, but had no influence on the growth geometry and nucleation type of the crystal of PLA. The results of polarized optical microscopy （POM） further proved that OLA-g-C as the nucleating agent, reduced crystallization time, and enhanced the crystallization ability of PLA. However, the elongational viscosity decreased with the addition of OLA-g-C, which related to the entanglement between OLA-g-C and PLA matrix.