Structure, Characterization Of Stereocomplex Poly(Lactic Acid) And It’s Application In The Poly(L-lactic Acid) Modification

A series of Poly(L-lactide) and Poly(D-lactide) was synthesized via ring opening polymerization. Binary blends of PLLA/PDLA were obtained through solution cast. XRD, DSC, POM and rheology mesurement were taken to investigate the influence of optical purity on the stereocomplex polylactide. The results show that high optical purity leads to finely structured stereocomplex crystallite and higher crystallinity. The hydrogen bond between PDLA and PLLA results to a high complex viscosity in melt state.Materials of PLLA/PDLA blends were subjected to hydrolytic degradation in buffer solution in50℃. Thermal gravity analysis (TGA) was also made in order to investigate the enhancement effect of sc in the blends. The degradation processes in buffer solution were monitored by following mass loss, water uptake, thermal properties, surface changes and pH of the aging medium. The results show that blends with higher optical purity have more stable degradation properties. The existence of sc can well control the degradation step of PLA. TGA results suggest that blends with high optical purity are more resistant to pure PLLA and those with lower optical purity. The activation energy was calculated from the TGA data, it’s value is more closely related to molecular weight but not the optical purity.PDLA was added to the PLLA/POE-GMA blends and the effect of the addition of PDLA was discussed. By adding1-2wt%PDLA, the ternary system has the best tensile and impact properties. The results of DSC. XRD and SEM show that the addition of PDLA leads to a better surface compatibility between PLLA and POE-GMA, it also decreases the diameter of elastomer in the matrix and has an acceleration effect on the materials’crystallization.