Modification Research Of Copolymer Derived From Carbon Dioxide And Propylene Oxide

Poly（propylene carbonate）（PPC） is a kind of completely biodegradable aliphatic polycarbonate which was synthesized from carbon dioxide and propylene oxide. PPC is a class of very promising environmentally friendly materials. However, the amorphous structure, flexible molecular chain and small interaction force of PPC lead to its relatively low glass transition temperature（Tg）, poor mechanical performance, greatly limiting its application scope. This thesis mainly job is to improve the thermal properties, mechanical properties and processing properties of CO₂ and PO copolymer（one is alternating PPC, the other is PPC with a double bond and ether chain segment）, through grafting modified PPC. The main research results are summarized as follows:1、Terpolymer（PPCNA） which had a small amount of double bond was synthesized though utilizing DMC catalyst as the catalyst for the single-step terpolymerization of norbornene anhydride（NA）, propylene oxide, and carbon dioxide. PPCNA successful y grafted on N-Vinyl-2-pyrrolidone（NVP） 、 Butyl acrylate（BA） 、Acrylonitrile（AN） and Poly（ethylene glycol） diacrylate（PEGDA） under the action of free radical initiator in the gas phase carbon dioxide medium. The influences of various reaction conditions such as different grafting monomers and free radical initiator, the content of grafting monomers and free radical initiator,reaction pressure,the content of endo-NA on PPCNA grafting modification were investigated.The thermal stability of PPCNA and its graft copolymer were characterized by TGA. The results showed that the initial thermal decomposition temperature of the graft copolymer compared with PPCNA had obvious enhancement.2、The graft copolymerization of terpolymer（PPCNA） and N-Vinyl-2-pyrrolidone（NVP） was carried out by using 2,2’-Azobis（2-methylpropionitrile）（AIBN） as the free radical initiator at temperatures of 80 oC, speed of 30r/min, in the Haake torque rheometer. Graft copolymer（PPCNA-NVP） was synthesized. PPCNA and PPCNANVP were characterized by FT-IR, TGA and tensile test measurements. The results showed that solvent resistance, thermal stability and mechanical properties of the graft copolymer（PPCNA-NVP） compared with the unmodified PPCNA were improved.3、PPC end-capped with anhydride（PPC-A） was prepared through melt compounding. The graft copolymer containing polyvinylpyrrolidone（PVP） and poly（propylene carbonate）（PPC） was synthesized by using N-Vinyl-2-pyrrolidone（NVP） to graft PPC end-capped with anhydride（PPC-A） under the action of free radical initiator in the Haake torque rheometer. PPC and its graft copolymer were characterized by FTIR, DSC, TGA, SEM and tensile test. Experimental investigation shows that solvent resistance, thermal performance and mechanical properties of the graft copolymer compared with the unmodified PPC were improved, and the application range of PPC was greatly widened.