Study On The Structure And Properties Of Biodegradable Poly(Propylene Carbonate) Blends

Poly(propylene carbonate)(PPC)is an amorphous thermoplastic aliphatic polycarbonate,alternating copolymer formed by copolymerization of CO₂ gas and propylene oxide.Due to its excellent biodegradable,biocompatibility,high transparency,good processability,excellent gas barrier properties and mechanical flexibility,it has been widely used in food packaging materials,biological tissue engineering,barrier materials and other fields.The research and development of PPC can not only reduce people's over-dependence on oil resources,but also avoid the white pollution caused by waste plastics and the greenhouse effect caused by CO₂.However,in view of the low glass transition temperature,low strength,and poor thermal stability of PPC,which severely limits the use of PPC in the packaging material industry,it is necessary to improve its performance.In this paper,aiming at the disadvantages of low glass transition temperature,low strength,and poor thermal stability of PPC,the melt blending method was used to prepare PPC-based blends with excellent properties.The microstructure and macroscopic properties of PPC-based blends were characterized by DSC,DMA,TGA,rheology,tensile testing,SEM and other technical methods,and the relationship between the structure and properties of PPC-based blends were analyzed and summarized.The results and conclusions obtained in this paper are as follows:(1)PPC/ESO blends with different component ratios were prepared by melt blending,and the phase morphology,thermal properties,rheological properties and mechanical properties of the blends were studied in detail.SEM showed that the ESO droplets were dispersed in the PPC matrix,showing a two-phase structure,and there were strong interfacial interactions between the two phases.The T_g of the PPC component in the blend increased with the increase of the ESO content,and the T_gincreased from 26.3 ? to 27.5 ?.With the increase of ESO content,the strength and elongation at break of the PPC/ESO blend had been improved.When the ESO content was 7 wt%,the yield strength,breaking strength and breaking elongation of the PPC/ESO blend were 13.8 MPa,12.7 MPa,and 848.9%,respectively.Compared with neat PPC,it had increased by about 16.9%,25.7%and 13.7%,respectively.In the low frequency region,the G',G'',and|?*|of the PPC/ESO blend were significantly improved through rheological tests.The disappearance of the epoxy groups in FTIR indicated that the interfacial interaction between the two phases was caused by the ring-opening reaction between the terminal hydroxyl groups of PPC and the epoxy groups of ESO.With the addition of ESO,the thermal stability of PPC/ESO blends had also been significantly improved.The temperature corresponding to the onset temperature of decomposition(T_onset)and the temperature corresponding to the maximum rate of weight loss(T_max)increased from 264.2 ? and 280.5 ? to 271.8 ? and 289.0 ?,respectively.The above results indicated that the ring-opening reaction between ESO and PPC increased the interfacial interaction between the two phases,thereby improving the performance of PPC.(2)The PPC/PHBV fiber composites were prepared by melt blending,and the microstructure,thermal properties,rheological properties and mechanical properties of the composites were studied in detail.The tensile test showed that with the increase of PHBV fiber content,the Young's modulus and tensile strength of PPC/PHBV fiber composite materials increased and when the PHBV fiber content was 40 wt%,the Young's modulus and tensile strength were 995 Mpa and 20.6 Mpa,respectively.,indicating that PHBV fiber could effectively improve the mechanical properties of PPC.The T_g of the PPC component in the composite material increased with the increase of the PHBV fiber content,and the T_g increased from 25.4 ? to 28.7 ?.The VST of PPC/PHBV fiber composites increased with the increase of PHBV fiber content.When the PHBV fiber content was 40 wt%,the VST value was 63.3 ?,which was 31.4 ? higher than that of neat PPC,indicating that PHBV fiber could effectively improve the heat resistance of PPC matrix.According to the rheological test,with the increase of PHBV fiber content,the G',G''and|?*|of PPC/PHBV fiber composites had increased significantly throughout the test frequency range.This was because on the one hand,PHBV fibers had a reinforcing effect on PPC,and on the other hand,because PHBV fibers formed a network structure in the PPC matrix.SEM results show that PHBV fibers were uniformly dispersed in the PPC matrix,and the interface between PPC and PHBV fibers had good bonding..In short,PHBV fiber was a better reinforcing agent,which could effectively improve the properties of PPC and maintain the biodegradability of the material.