Abstract: Poly(lactic acid)（PLA）/poly(ethylene-co-vinyl acetate)（EVA） blends were prepared by melt blending. The effects of melt flow rate of EVA （28% VA content） on the morphology，thermal properties and rheological behaviors of PLA/EVA blends were investigated. The results indicated that the EVA phase with smaller particles and better dispersion in the PLA matrix was observed when the EVA with lower melt flow rate was used. With the increase of melt flow rate of EVA，the crystallinity of blends was increased，though the Tg of PLA was hardly affected by the addition of EVA. And the complex viscosity and storage modulus of the blends were decreased. It was demonstrated by mechanical tests that with the addition of 15% EVA into PLA，an obvious increase in elongation at break was observed，and the izod notched impact strength was about two times higher than the pure PLA.

Key words: poly(lactic acid), ethylene-co-vinyl acetate, blend, melt flow rate, crystallization, visicosity

摘要： 通过熔融共混法制备了聚乳酸（PLA）/乙烯-乙酸乙烯酯共聚物（EVA）共混物，采用SEM、DSC、旋转流变仪等研究了VA质量分数为28%，熔体流动速率（MFR）不同的EVA对PLA/EVA共混物性能的影响。结果表明，EVA熔体流动速率越小，其在PLA基体中分散越均匀，EVA颗粒粒径也越小。共混物的结晶度随EVA熔体流动速率的增大而增大，但PLA的玻璃化转变温度（Tg）基本不受EVA的影响。PLA/EVA共混物的复数黏度和储能模量均随EVA的熔体流动速率的增高而减小。力学性能测试结果表明，当EVA的质量分数为15%时，PLA的断裂伸长率明显升高，冲击强度约是纯PLA的2倍。

关键词: 聚乳酸, 乙烯-乙酸乙烯酯共聚物, 共混, 熔体流动速率, 结晶, 黏度