Preparation, the Chain-extending Reaction Kinetics and Thermal Degradation of Poly(D-lactide) by Reactive Extrusion Process

The chain-extended poly(D-lactide) (PDLA) was prepared from D-lactide under optimum polymerization conditions of 1 wt% stannous octoate, at 170 degrees C, 10 rpm for 15 min or 10 min with the addition of chain extender (4,4'-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI)) by reactive extrusion process. The molecular weight of PDLA-MDI and PDLA-HDI was 45376 and 47238 g/mol, respectively, which had been significantly improved compared with PDLA (M-w 20730 g/mol). Furthermore, differential scanning calorimetry (DSC) results showed that the crystallinity of PDLA-MDI and PDLA-HDI was increased by 66.04 and 78.60%, respectively, compared with PDLA. Moreover, the rheological results and thermal decomposition kinetics results showed that the MDI and HDI had restricted the mobility of PDLA chains and enhanced the apparent activation energy (E-a) of thermal degradation of PDLA.