Preparation And Modification Of Biodegradable Poly(Propylene Carbonate) And Its Melt Blending Fibers

Poly(propylene carbonate)(PPC), synthesized by CO2as the main raw material, is a fully biodegradable polymer. Its development and practical application not only largely alleviate the "White Pollution" and "Greenhouse Effect" two serious environment problems, and at the same time also can improve the current situation of energy crisis and thus become the hotpots of scientific research. PPC has excellent biocompatibility and gas barrier properties (oxygen resistance), high molecular chain flexibility and elongation of its products. However, low glass transition temperature, poor mechanical performance and degradation in thermal processing, greatly limit its applications. It is economical as well as effective method to take chemical end-capping modification of PPC and melt blending modify it with the help of biodegradable materials. Meanwhile, exploring the application of PPC in fiber field by researching and developing PPC blends fibers is also very meaningful.The main work of this paper was aiming to enhance the processing and mechanical performance of industrial PPC to take the end-capping modified treatment with the help of ZeMac. Meanwhile, Poly(lactic acid)(PLA), another kind of biodegradable polymer, was used for melt blending with PPC to prepare PPC/PLA composite materials. Zemac was used as reactive compatibilizer for PPC/PLC composite system to get composite blends with superior overall performance. PPC blends were melt spun into fiber and the mechanical properties were studied. The specifics of the issues were shown as follows:1. With the catalyst ash remained in the system, industrial PPC material was end-capping modified through melt compounding. The blends were characterized by using FTIR, DSC, TGA, SEM and tensile test. The effects of ZeMac on the thermal stability, glass transition temperature and mechanical properties of PPC were studied. The results showed that the end-capping modified reaction could effectively occur between PPC and ZeMac. When the content of ZeMac reached to 0.7%, the5%decomposition temperature (T5%) of pure PPC increased from157.4℃to253.8℃. As a result, the processing windows of temperature and time were largely extended, and the heat resistance of composites was improved remarkably. Meanwhile, when the content of ZeMac reached to1%, the tensile strength increased from1.72MPa to12.56MPa. This occurred might be due to extender chain effect and some physical cross-linking structure when the PPC was modified by ZeMac, which could largely improve the tensile strength of the material.2. Through the methods of Kissinger, Flynn-Wall-Ozawa, Costs-Redfern, the thermal decomposition kinetics of non-isothermal of pure PPC and modified PPC were analyzed respectively. Then the possible thermal decomposition reaction mechanism and kinetic parameter were studied. The results showed that under the function of catalyst, end hydroxyl group of pure PPC at lower temperature was liable to be unzipping degraded, and then bited back to form a five-membered ring as the first stage weight-lost at TGA curve. While the catalyst had no effect on random fracture, random fracture occurred to PPC at higher temperature, as shown the second stage weight-lost at TGA curve. Since the end hydroxyl groups of PPC modified by ZeMac accomplished end-capping reaction and unabled to bite back and form the five-membered ring, so there was only one random fracture degradation stage at TGA curce. The thermal degradation activation energy of pure PPC and modified by ZeMac were89.36kJ·mol-1and165.52kJ·mol-1respectively.3. Through melt blending with PLA, different proportions of PPC/PLA composites were prepared successfully. These composites were characterized by using FTIR, DSC, TGA, SEM and tensile test. The results showed that the mechanical properties and thermal stability of pure PPC were effectively improved by adding of PLA, and also the compatibility between PLA and PPC was greatly improved.4. To enhance the interfacial bonding between PLA and PPC further, ZeMac was added to PPC/PLA composite to take reactive blending. The blends were characterized by FTIR, DSC, TGA, SEM and tensile test. On this basis, PPC-based blends fibers were prepared. The results showed that ZeMac could be bridging agent enable graft reaction occurred between PPC and PLA. The interfacial bonding between matrix PPC and PLA was enhanced by the grafted PPC, and as a result the compatibility was promoted, the mechanical property and thermal stability were further improved. The tensile strength of PPC blend fibers could reach1.98cN. dtex-1after heated drawing, and its biodegradation property was excellent as well under different circumstances.