苯乙烯-丙烯酸甲酯共聚物对聚苯乙烯/聚乳酸共混物力学性能和流变性能的影响

采用无皂乳液聚合法合成了苯乙烯-丙烯酸甲酯共聚物(PSMA)(n(St)∶n(MA)=75∶25),将PSMA与聚苯乙烯(PS)和聚乳酸(PLA)熔融共混制备了PSMA含量不同的PS/PLA共混物(m(PS)∶m(PLA)=1∶4),利用扫描电子显微镜、电子拉力机和转矩流变仪对共混物的相结构、力学性能以及流变行为进行了表征。结果表明,加入少量PSMA即能有效提高PLA与PS的相容性,减小PS/PLA共混物中分散相的相尺寸,提高PLA与PS两相间粘接作用;加入质量分数为0.5%的PSMA时,PS/PLA共混物的力学性能达到最佳;未加PSMA时,PS/PLA共混物在高剪切速率下剪切变稀显著,甚至低于纯PS,加入PSMA后,在高剪切速率下的剪切变稀程度与纯PLA相当。

Effect of Poly(Stylene co Methyl Acrylate) on Mechanical and Rheological Properties of Polystyrene/Poly(lactic acid) Blends

Surfactant-free emulsion polymerization was used to synthesize poly (styrene-ran-methyl acrylate) (PSMA) at the mole ratio of styrene/(methyl acrylate) 75/25,which,at different contents,was then melt-blended with a polystyrene (PS)/poly(lactic aicd) (PLA) tumble-mixture (mass ratio of 1/4) to prepare PSMA-modified PS/PLA blends,of which the phase morphology,mechanical properties and rheological behavior were characterized through scanning electron microscopy (SEM),tensile testing and rotational rheometry,respectivelye.It is revealed that addition of a small amount of PSMA effectively improves the compatibility and thus the interfacial adhesion of the PS/PLA blend,thereby reducing the size of the PS dispersed phase;there exist an optimum PSMA-content of ～0.5％ that gives rise to the maximum mechanical properties of the PS/PLA blend.At high shear rates,the PS/PLA blend exhibits a significant shear-thinning behavior in absence of the PSMA modifier,with its melt viscosity even lower than that of the neat PS,while the extent of shear-thinning is comparable to that of the neat PLA upon incorporation of PSMA.