The Study On Modification Of Fully Biodegradable Poly (Propylene Carbonate)

Poly (propylene carbonate)(PPC) is a new thermoplastic biodegradable polymers derived from carbon dioxide and propylene oxide. Due to its remarkable wet and gas resistibility, biodegradability and biocompatibility,it is widely applied in packaging materials as well as in medical field. Compared with other bidegradable polymers, PPC has some blemishes such as poorer mechanical properties and lower thermal stability, which limites its wider application. In this paper, chain extension and blending modification were two methods utilized to improving the comprehensive properties of PPC.First, MDI, the chain extender, reacted with PPC in a singl-step melt. The effects of MDI on the molecular weight distributions (MWD), branching and gel-like structures of modified PPC were investigated by FTIR,TG, torque and rotation rheological analyses. The results show that the MWD, the branch degree, melt strength, intrinsic viscosity and solid-like behavior of the modified PPC were enhanced with the increasing amount of MDI. But the thermal stability weaked by the chain extension.With an amount of 2.0 wt% MDI, the strucute of modified PPC came to the sol-gel transition point.Second, the PBS/PPC blend was first prepared by melt mixing.The phase morphology and the viscoelastic behavior of the blend were then studied by FYIR,TG,SEM and strutural rheology.The results show that PPC was immiscible with PBS; With the increasing amount of PBS, the morhology of disperse phase changed from spherical droplet to fibrous and the co-continuous structures.The phase inversion appeared when the PBS increased to 40%. The interfaces of blends were found to be clearly separated, and the conjunction zone of two phase was loose.Third, the PBS-g-MAH was prepared and used as a compatibilizer to improve the compatibility of PPC/PBS blends. Characterized by IR, SEM, torque and rotation rheological analyses, PBS-g-MAH was found to be an efficient compatibilizer for PPC/PBS blends at a proper concentration, it could enhance the interface adhesion and improve the mechanical properties of PPC/PBS blends. Compared with the uncompatibilized blend,the tensile strength was improved 30% when the concentration of PBS-g-MAH was optimized to 15 wt%.