Properties and Morphology of Poly(Lactic Acid)/Calcium Carbonate Whiskers Composites Prepared by a Vane Mixer based on an Extensional Flow Field

Abstract

ABSTRACTBinary composites of poly(lactic acid) (PLA)/calcium carbonate whiskers (CCW) with different weight fractions were prepared with a vane mixer based on extensional rheology. The mechanical properties, thermostability, crystallization behavior, rheology behaviors and micromorphology of the composites were analysed to study the effect of the CCW fibers on the composite's properties; a pure PLA sample was also prepared for comparison. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) revealed that the CCW fibers had excellent compatibility with the PLA matrix and the CCW fibers were dispersed and distributed evenly in the PLA matrix under the action of the extensional flow field produced by the vane mixer. Differential scanning calorimetric (DSC) analysis showed that introducing a vane mixer into the PLA processing could increase the degree of crystallization (χc) of the composites significantly, and moderate CCW fibers adding could further increase its χc value. Thermogravimetric analysis (TGA) revealed that adding the CCW fibers reduced the thermostability of the composites. The G′, G″, η* and the torque, TN, of the composites, obtained from rheology analyses, declined obviously, because of the hydrolysis and chains scission induced by residual water and fatty acid when the CCW content less than 4%. Tensile tests proved that filling moderate amounts of CCW fibers into PLA could increase its tensile strength and strain at break, increasing by 5% and 29.6%, respectively.