Study Of Montmorillonite Modified Poly(Propylene Carbonate) Matrix Nanocomposites

Poly(propylene carbonate)(PPC) was produced by a catalytic copolymerization of carbon dioxide and propylene epoxide. It had attracted more widely attentions owing to its characteristics of good large elongation at break, biodegradable properties and biocompatibility.The application of PPC was greatly limited because of high melt viciosity, low thermal stability and poor mechanical strength. In order to solve this problem, PPC as matrix, two kinds of organic modification Montmorillonite(MMT-DK2, MMT-DK5) and Polylactic(PLA) were used to produce PPC/MMT and PPC/PLA/MMT nano-composites in this paper.Three kinds of industrial PPC were mersuresed to determine the appropriate matrix. The results showed that the carbonate group contents of DOW PPC and SABIC PPC were very low. And it is difficult for PPC to degrade at a low content of carbonate group. As a result, DOW PPC and SABIC PPC were not environmentally friendly. So the Tianguan PPC was the appropriate matrix. Then the glass transition temperature of Tianguan PPC was 30.6℃. And when the temperature higher than 110℃, the thermo degradation of Tianguan PPC would be happened. Furthermore normal rheological splines were found in 140~170℃. So the processing temperature range was 140~170℃.Tianguan PPC and two kinds of MMT were used to prepare PPC/MMT nano-composites. The results showed: PPC molecular chains had intercalated into MMT interlayer and MMT layers were dispersed in PPC matrix in nano scale. In addition, it is more easily that the MMT-DK2 layers were inserted into PPC. Moreover the tensile strength and thermal stability of nano-composites tended to increase with increasing the MMT, while elongation at break decreased greatly,compared with pure PPC. At same time, the melt viscosity decreased with MMT addition. To sum up, the most appropriate addition was 4wt%MMT-DK2.Tianguan PPC, MMT-DK2 and PLA were used to produce PPC/PLA/MMT nano-composites. The results showed that the nano-composites are "Sea Island" structure. The thermal stability, tensile strength and rheological properties were improved with the addition of PLA. When the content of PLA was 40wt%,the overall performance of blends was best.