Preparation And Characteriazation Of Polylactic Acid Based Composites With Shape Memory Effect

With the development of society,people quality of life is getting higher and higher,Information,energy and materials have become an important symbol of modern society.In this case,people can not meet the traditional materials,so they are eager for new shape memory materials.It is often said that the first thing people can think of is the shape memory alloy,such as Fe Mn alloy,Ti Ni alloy.But in fact,in addition to the well-known shape memory alloy,polymer is also a good shape memory materials.Compared with the alloy,shape memory polymers have the following characteristics:?1?Shape memory effect is obvious,the stimulation temperature is low,easy to process into various devices,the cost is relatively low?2?With a variety of incentives,in addition to stimulating the traditional source,also can be prepared with optical,electrical and magnetic stimulation,pH,solution of memory materials,and these stimuli can exist at the same time with a variety of stimulus materials forming;?3?With flexible molecular design,different memory characteristics can be designed according to different molecular structure characteristics;?4?Compared with the alloy,the polymer has obvious characteristics of light weight;?5?The utility model has the advantages of high controllability,and can make the material multifunctional through the combination of different nano materials or controlled synthesis method;?6?Many polymers have good biocompatibility and biodegradability,and have wide application and prospect in the field of biomedicine.In this paper,polylactic acid?PLA?was used as the matrix,and the blends were prepared by blending and hot pressing.In the second chapter,we mainly with polylactic acid?PLA?and polymethyl methacrylate?PMMA?as the research object,by differential scanning calorimetry?DSC?,dynamic mechanical analysis?DMA?,X ray diffraction analysis,we discuss the fixation and recovery of the system under different ratios,compared the tensile and bending condition of material recovery ability,and the stability of the materials with multiple shape memory processes,and the shape memory effect of the double shape memory effect and the degradation process were investigated.In the third chapter,in order to change the way of material stimulation,TPU and multi walled carbon nanotubes?CNTs?were used to replace PMMA,and the PLA/TPU/CNTs composites were prepared by two step blending method.The system can make the carbon nanotubes as dispersed as possible in TPU,enhance the conductivity and save the use of carbon nanotubes.The basic properties of the material were determined by DSC analysis,rheological analysis and resistivity measurement.Finally,the shape memory properties of the materials were tested by two ways of thermal and electric.In the fourth chapter,we continue to use the PLA/TPU system of the third chapter to prepare the magnetic shape memory material.Because of the heat loss and the slow heat transfer in the presence of the magnetic shape memory material,the memory effect is not good,to this end,we have made some improvements.Multi walled carbon nanotubes?CNTs?have good thermal conductivity,and by the method of grafting maleic anhydride and beta cyclodextrin,and coprecipitation method,.the magnetic filler is prepared.Finally,the magnetic CNTs-Fe₃O₄ was compounded in the polymer by blending and hot pressing,the shape memory material with magnetic effect is formed.