The Fabrication,Structures And Mechanical Properties Of Polylactide/Graphene Oxide And Aliphatic Polycarbonate Modified Polylactide/Graphene Oxide Composites

Polylactide as a kind of renewable biodegradable materials can solve the shortages caused by the plastic products and environmental pollution problems.But the poor toughness,heat resistance and low crystallization rate limited its widespread use.Copolymerization,blending,and nano composite were the effective measures to improve its performances.Thus the polyphase system structures brought by modification of polylactide provide good research objects for the study of its crystallization behaviors,phase structures and interface structures.In this work,the crystal structure,phase structure,interface structure and mechanical properties of polylactide/graphene oxide and aliphatic polycarbonate modified polylactide/graphene oxide composites were studied.FGO was obtained through grafting octadecylamine onto the surface of GO.Then,PLLA/GO and PLLA/fGO nanocomposites were prepared by the method of solution blending.And the different effects of GO with polar groups and functionalized GO(fGO)with nonpolar groups on the isothermal crystallization behaviors of PLLA were researched.It was found fGO with larger interlamellar spacing dispersed better in PLLA and provided more points of nucleations than that of GO.Therefore,fGO improved the PLLA crystallization rate more significantly than GO.PLLA-PTMC/PDLA and PLLA-PTMC/PDLA/GO nanocomposites were prepared by introducing PDLA and GO into PLLA-PTMC throughsolution blending.Non-isothermal crystallization kinetics,crystal morphology and crystallization activation energy showed that all of the two systems could form stereocomplex crystallization.In the process of stereocomplex formation,GO promoted the nucleation and limited the crystal growth at the same time Therefore,the crystallization activation energy of PLLA-PTMC/PDLA/GO is higher than that of PLLA-PTMC/PDLA.Mechanical properties tests showed that the loading of Sc and GO caused tensile strength significantly improved and the elongation at breakdecreased simultaneously.Dynamic thermal mechanical properties tests showed that the E’ of PLLA-PTMC/PDLA and PLLA-PTMC/PDLA/GO were higher than PLLA-PTMC at 70℃,which suggested that the introduction of PDLA and PDLA/GO could improve the heat resistance of the composites.In addition,when stereocomplex content is similar,introducing GO can effectively improve the tensile strength,modulus and heat resistance.PLLA was grafted onto the GO through esterification reaction,and then PLLA/PPC/PLLA-g-GO nanocomposites were prepared by the method of solution blending.The investigations of microstructures of nanocomposites showed that after introducing PLLA-g-GO into PLLA/PPC blends,GO transferred from PPC phase to the interfaces of PLLA and PPC,which prompted composite formed a network-like structure.The network-like structure significantly improved the tensile strength and elongation at break of the nanocomposite.And the PLLA-g-GO located at the interface of PLLA and PPC could promote the interface crystallization,which enhanced the interaction between two phases and significantly increased the tensile strength and elongation.