Research On The Blend Of HA-g-PDLA And PLLA

Hydroxyapatite (HA) is clinically recognized as a kind of bone substitute material, however, owning to low-strength, brittleness and easiness to fatigue, it is difficult to be used as bone substitute materials separately. Blending HA with degradable polymer is a useful method to improve the properties of HA. Polylactide (PLA) is one kind of these polymers because of its biodegradability and biocompatibility. PLA can improve the fragile, low-toughness and other defects of HA, conversely HA can neutralize acidic products produced by the degradation of PLA. Due to poor dispersion in the polymer, grafting polymerization method is often used to modify the HA surface preventing the aggregation of HA nanoparticles. When poly(D-lactide) (PDLA) is grafted onto the surface of HA, it may improve interfacial compatibility between HA and poly(L-lactide) (PLLA), and also it can form stereocomplex crystals (sc) with PLLA matrix, improving the crystallization properties of overall composite materials, thus HA-g-PDLA has the potential to further enhance mechanical properties of HA composite and has favorable application foreground.This work focuses on the crystallization behavior of HA-g-PDLA/PLLA, it mainly includes the following parts:To improve the poor dispersion of HA nano-particles in PLLA matrix, PDLA was grafted on HA surface, TGA, IR and XPS results show that the reaction was successful, and then the experiment conditions were optimized. SEM results show that the interfacial compatibility between HA and PLLA was improved.The influence of HA-g-PDLA content on the crystallization of HA-g-PDLA/PLLA was studied by changing the ratio of HA-g-PDLA to PLLA in the blend;Comparing the crystallization behavior of HA-g-PDLA/PLLA with PLLA, HA/PLLA, PDLA/PLLA, HA/PDLA/PLLA and HA-g-PLLA/PLLA, the reason for the best nucleation effect of HA-g-PDLA was analyzed.The crystallization of PDLA/PLLA was studied at the presence of HA and HA-g-PDLA respectively, the effect of HA or HA-g-PDLA on the formation of stereocomplex crystals was studied, and the mechanism of nucleation was explained.