Study on the Crystallization Kinetic and Characterization of Poly(lactic acid) and Poly(vinyl alcohol) Blends

In this study, poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) blends, with PLA/PVA mass ratios of 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, and 40/60, were prepared by means of the melt blending method. The result of torque measurements and thermal gravimtric analysis tests showed that the addition of PLA can decrease the melt viscosity of PVA and that the second degradation step of PVA nearly disappeared for the PLA80/PVA20 blend. The absorbance peaks of the carbonyl group and the hydroxyl group in the Fourier transform infrared spectra of PLA/PVA blends had significant shifts to lower wave numbers, indicating that there were interactions between these two groups. Combined with the result of the differential scanning calorimetry curves, this interaction would be favorable for improving miscibility. The X-ray diffraction patterns and the polarized light microscope (PLM) micrographs showed that PVA can serve as a nucleating agent to promote the crystallization of PLA in PLA/PVA blends. Moreover, the PLA80/PVA20 blend gave the highest growth rate of PLA spherulite.