Thermal Degradation And Modified Chain Extended Of PLA

PLA, as a biodegradable material has received more and more attention, has been applied in the field of medical, packaging, and has good prospects. In this paper, it was focused on studying the thermal stability and extruding chain extension.The change of molecular weight was studied with different water content, and melting temperatures. The results indicated that when PLA contained water, the averaged viscosity molecular weight decreased rapidly, the final balance of weight was related to moisture and melting temperature closely. The molecular weight of PLA which was drying completely decreased slowly. PLA with different moisture was dried to determine the appropriate drying temperature and drying time. The regulation of PLA degradation was estimated by TGA, and the effect factors of degradation were determined.The extrusion was tested in the use of the material of vacuum dried PLA. The temperature of the extrusion and screw are the main factor for the PLA molecular weight. The result show that the decreasement of vacuum dried PLA is driven by the shear in the extruder and then the chemical degradation. The molecular weight distribution is narrowed when the situation of molecular weight decreasing is happening.MDI, TGIC were used as chain extender, and chain extender were prepared with IPDI and small molecules which containing hydroxyl terminated. The molecular weight of PLA which changed with the addition of chain extender and compared with the changes of mechanical properties which joined flexible chains were studied. Averaged viscosity molecular weight increased and melting index lowed with the addition of chain extender increased. The polyether was good at improving mechanical properties of PLA compared with the polyester which contained the same chain length.