Preparation And Characterization Of Triple Shape Memory TPI Elastomer Based On Crystal

Shape memory elastomer is a typical intelligent material,which possesses broad application prospects in the field of aerospace,biomedicine,intelligent robots,etc.Although the current dual shape memory materials can be repeatedly used,they can only realize one-step memory recovery from a temporary fixed shape to a unique permanent shape for once.The actual operation is not flexible enough,which greatly limits the scope of application.Although bi-directional shape memory materials can perform shape memory recovery in the opposite direction,the shape deformations of bi-directional shape memory are all low,which is not suitable for the requirement in some fields.Therefore,how to construct a material that can realize multiple shape memories,as well as reverse recovery and considerable deformation amount has become an urgent problem to be solved.In this thesis,small crystallizable molecules such as paraffin and rice bran wax were introduced into the trans-polyisoprene cross-linking network by physically blending and chemically cross-linking.A series of heat-induced two-component crystalline triple shape memory elastomers were prepared.(1)Shape memory elastomer based on paraffin and TPI blendingIn the second chapter of the thesis,low-cost paraffin is selected as the raw material.Based on the great difference between the melting temperature and crystallization temperature between TPI and paraffin,the obtained polymer materials exhibit triple shape memory behavior.The materials with different paraffin content and TPI crosslink density were observed by DSC,XRD,SEM and DMTA,and their crystallization behavior,micro-morphology and mechanical properties were analyzed.By controlling the content of the cross-link density of the stationary phase and the crystallizable content of the recovery phase,the shape memory properties of the material were tunable,and the comprehensive performance is obtained for the 1.0S-TPI/60P sample,with blending ratio of 60%paraffin,exhibiting the first and second stage fixed rate of 88.0%and 96.9%,respectively,and the first and second stage recovery rate of 85.0%and 99.3%,respectively.(2)Reverse reply programming and flexible application based on triple shape memoryThe third chapter of the thesis innovatively proposes a reverse triple shape memory recovery programming method.Based on the materials in Chapter 2,through the simulation experiments conducted on the glass stopper,the small area experiment(thumb)and large area experiment(torso)conducted on the surface of the human body,it was confirmed that the body temperature of the human body can trigger the shape memory recovery of the material.In the macro application,it exhibits excellent performances such as rapid recovery time and good recovery fit.It can also be detached intelligently at a higher temperature,can completely restore its original shape at a higher temperature and can be stably reused.It has broad application prospects,and can be especially applied to medical fixing materials outside the human body.(3)Shape memory elastomer based on blending of rice bran wax and TPIIn the fourth chapter of the thesis,the bio-based material rice bran wax is introduced to the materials in the second chapter instead of the paraffin.Because the melting temperature of rice bran wax is higher than that of paraffin,it can be more separated from the melting temperature of TPI.Then the mechanism and performance of triple shape memory elastomer can be further explored.It is expected that its triple shape memory performance will be further improved improvement.