Application Of Two Dimensional Material MXene In The Improvement Of The Crystallization And Tensile Mechanical Properties Of Polylactic Acid

In recent years,the environmental pollution and petroleum consumption caused by petroleum based polymer materials have attracted worldwide attention.Polylactic acid(PLA)is a natural synthetic polymer material with excellent biodegradability and biocompatibility,but its poor crystallinity,poor heat resistance and "hard and brittle" mechanical properties limit its application.MXene is a two-dimensional inorganic carbon-nitrogen compound with excellent mechanical properties,and it can be used as nucleating agent to enhance the crystallization rate.Polybutanediol terephthalate(PBAT)is an environmental friendly material with better heat resistance and ductility.Polyethylene Glycol(PEG)has good water solubility and is highly compatible with PLA.It is also a good plasticizer for PLA.So MXene is chosen as nucleating agent,PBAT as toughening agent and PEG as plasticizing agent to study the effect of PBAT,PEG and MXene on PLA properties.In this paper,MXene is prepared by etching MAX phase,and the dense layered structure of MAX phase is found to be interstitial by SEM.The effect of MXene on PLA performance is studied.The results of X-ray diffractometer(XRD)show that MXene as nucleating agent do not affect the crystal form of PLA;MXene is found to increase the nucleation density of PLA by POM;MXene is found to decrease the cold crystallization temperature of PLA but decrease the total crystallization rate by DSC;the tensile mechanical properties of PLA are found to increase the tensile strength and elongation at break of PLA.Secondly,in order to solve the problem of poor compatibility between MXene and PLA,the silane coupling agent is used to modify MXene to improve its dispersion in PLA matrix.The appearance of Ti-O-Si bond characteristic peaks in Fourier infrared spectroscopy(FTIR)indicates that the modification is successful.The effect of OTES-MXene on the properties of PLA is study.The results show that the modified MXene can still be used as nucleating agent to promote the nucleation of PLA,but the nucleation effect is not as good as before.The cold crystallization temperature of the composites decreases and the crystallization rate do not increases.The effect on thermal stability and mechanical properties is similar to that of MXene,but the effect on thermal stability and mechanical properties is slightly lower.Then,the effect of PBAT and MXene on PLA performance is studied by adding PBAT with10 wt% in PLA/MXene.The results show that the cold-crystallization temperature of PLA decreases with the addition of PBAT,and further decreases with the synergistic effect of MXene.The results of TGA show that the maximum decomposition temperature of PLA/MXene composites increases with the introduction of PBAT.The addition of PBAT as toughening agent increases the elongation at break of PLA and PLA/MXene composites,but decreases the tensile strength.Finally,the effect of PEG and MXene on the properties of PLA is studied by adding plasticizer PEG with 10 wt% in PLA/MXene.The introduction of PEG improves the fluidity of PLA molecular chain,reduces the cold crystallization temperature,improves the crystallization property of PLA/MXene composite,shortens the time to complete crystallization and accelerates isothermal crystallization.The tensile strength of PLA/PEG/MXene composites decreases significantly,but the elongation at break of PLA/PEG/MXene composites is 23 times higher than that of PLA/MXene composites.In terms of heat resistance,PEG makes the maximum decomposition temperature of PLA/MXene composites increase as a whole.