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

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 crystallinity 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.