Poly (Propylene Carbonate) Modified By Polymer Powder

In the recent years, biodegradable materials have received much attentions owing to the short of resoures and environment problems. Among them, Poly(propylene carbonate)(PPC), is a new type of polymer material originated from the alternative copolymerization of carbon dioxide(CO2) and propylene epoxide(PO). In the synthesis process of PPC, CO2 was effectively utilized. Moreover, PPC have some excellent properties such as good biocompatibility, biodegradability, transparency, ductility and barrier properties. So PPC have many potential applications in many fields. However, PPC has flexible molecular chain and is an amorphous polymer with weak interchain interaction, leading to low glass transition temperature(Tg) and poor mechanical properties. Since, PPC is apt to degrade to PC via backbiting mechanism when processing temperature is over 170 °C, and its melting temperature is about 160°C, its processing temperature is typically narrow, which restricts the wide application of PPC. To broaden the applications of PPC, it is necessary to modify its physical properties. In this dissertation, cellulose powder(CP), wool powder, nylon 3 powder, nylon 6 powder and polyphenol powder were chosed to modify the physical properties of PPC using the solution mixing methods. The main results were list as follows:(1) When CP was used as filler to modify the physical properties of PPC, the effect of the content and particle size of CP on the properties of PPC/CP composties was investigated. The results show that CP was dispersed well in PPC matrix when the content of CP was lower. When the content of CP was increased to 0.5wt%, the partial aggregation of CP was observed in the composites, indicating the dispersion of CP becomes worse.The result of Fourier transform infrared(FTIR) indicated that that the strong interfacial interactions including the hydrogen bonding interactions and the possible chemical bonds exist between CP and PPC matrix. When the CP content is 2 wt%, the resultant composites exhibits the best thermal and mechanical properties. Tg of the composites increased from 28℃ to 35℃, but did not be influenced by the content of cellulose powder. The maximum weight loss temperature(Tmax) increased from 243℃to 285℃. The tensile strength and storage modulus of the composites would also be improved from 21 MPa to 35 MPa and from 1401 MPa to 2389 MPa with the addition of CP. In addition, the CP with the small size has better modification effect for PPC.(2) PPC/WP composites were prepared by solution blending. WP is well dispersed in PPC matrix, as evidenced by scanning electron microscopy(SEM) observations. FTIR measurements indicate that the strong interfacial interactions including the hydrogen bonding interactions and the possible chemical bonds exist between WP and PPC matrix. In terms of thermal properties, the incorporation of WP results to the increase of the Tg and the decomposition temperature of PPC. Furthermore, WP has an obvious effect on improving the tensile strength and the storage modulus from 21 MPa, 2184 MPa of pure PPC to 38 MPa and 2193 MPa, respectively. However, the addition of WP leads to the decrease of the elongation at break of PPC and the composites still remain somewhat ductile. When the WP content is 2 wt%, the resultant composites exhibits the best thermal and mechanical properties.(3) PA6 powder could disperse well in PPC matrix. There are strong interfacial interactions including the hydrogen bonding interactions and the possible chemical bonds exist between PPC and PA6 powder. When the PA6 powder content is 1 wt%, Tg of the composites increased from 28.3℃ to 37.6℃; and Tmax increased from 243℃to 263℃; Furthermore, the tensile strength and storage improved from 21 MPa and 1401 MPa to 37 MPa and 2797 MPa. The hardness of the composites was improved at different temperature. However, the addition of PA6 powder leads to the sharp decrease of the elongation at break of PPC.(4) PA3 was synthetized from acrylamide by the “Hydrogen transfer”polymerization. PPC/PA3 powder composites were made using the same method as mentioned above. PA3 powder is well dispersed in PPC matrix. There is no chemical reaction between PA3 powder and PPC. When the PA3 powder content is 1wt%, the resultant composites exhibits the best thermal and mechanical properties. Tg and Tmax improved from 28.3℃ to 35℃ and from 243℃ to 259℃; PA3 powder has an obvious effect of improving the tensile strength from 21 MPa to 37 MPa, storage modulus from 1401 MPa to 3182 MPa. The hardness of the composites was improved respectively at different temperature.(5) PPC/polyphenol powder composites were prepared by solution blending method. Polyphenol powder was well dispersed in PPC matrix when the content is lower. The result of Fourier transform infrared(FTIR) indicated that that the strong interfacial interactions including the hydrogen bonding interactions and the possible chemical bonds exist between Polyphenol and PPC matrix. In terms of thermal properties, the incorporation of polyphenol powder results to an increase of the Tg from 28℃ to 40℃ and the Tmax from 243℃ to 268℃ of the composites.The mechanical strength of the composites was obviously improved by the addition of polyphenol powder, the tensile strength from 21 MPa to 38 MPa and the storage modulus from 1401 MPa to 3204 MPa. However, the ductility of the composites decreased sharply by the addition of polyphenol powder.