Preparation And Properties Of TPI-based Triple Shape Memory Composite

Shape memory polymers are a typical intelligent material.With the development of science and technology,people’s pursuit of intelligence is getting higher and higher,so this kind of materials are more and more widely used in aerospace,construction equipment,biomedical,intelligent construction and other levels.At present,the research of double shape memory composite material has many,but because the double shape memory material can only change from a temporary shape to the initial shape,there are certain limitations in the application,so the need to urgently develop multiple shape memory reply shape memory material,to meet the growing application needs.In this thesis,trans-1,4-polyisoprene（TPI）and polyethylene glycol（PEG）were intermixed.A series of composites with triple shape memory functions were successfully prepared by introducing crystalline polyethylene glycol into the Trans-1,4-polyisoprene network.In order to improve the shape memory performance and mechanical properties of shape memory composite materials.（1）Shape memory composites based on mixing TPI and PEGIn this part,crystalline PEG and TPI were used to construct a triple shape memory system with different T_m through physical mixing.The crystallization behavior and micro morphology of the composites were analyzed by XRD,DSC and SEM.Testing the shape memory performance of the composites showed that the fixation effect of the temporary shape of the composite was more obvious with the increase of PEG content.When the addition of PEG was 40 phr,the R_fof the composite can reach 70.01%and 95.57%,and the R_r was 50.87%and 93.84%,respectively.According to the mechanical properties test,the mechanical properties of composites decreased significantly after PEG addition.The observation of the composite section by SEM showed the obvious separation of TPI and PEG phase and a significant decrease in the mechanical properties of the composites.After 40 phr PEG of addition,the composite tensile strength and fracture elongation decreased to7.36 MPa and 191.89%,respectively.（2）Shape memory composites of PEG/GO and TPIIn this part,PEG and GO were combined by solution mixing,and then formed a triple shape memory system with TPI.The results showed that PEG and GO were bonded by van der Waals force and hydrogen bond,and the two could be uniformly bonded.PEG/GO still had obvious crystallization behavior,and its T_m and T_c were still obviously different from TPI,which could be used to realize the triple shape memory behavior of TPI composites.The shape memory performance test results showed that with PEG/GO addition of 30 phr,the R_f of the composites could reach51.04%and 97.45%,respectively,and the R_r was 34.50%and 85.27%,respectively.Through the mechanical performance test,GO played a role in strengthening the mechanical properties of composites.The tensile strength and fracture elongation of TPI/30PEG94%were 14.12 MPa and 382.16%,respectively,leading up to 12.1%and 36.9%improvement compared to TPI/30PEG.（3）Shape memory composites of Si O₂@PEG and TPIIn this part,the Si O₂@PEG composite was prepared by the sol-gel method and was mixed as a filler with TPI.FTIR,XRD test results showed that PEG coated the Si O₂ surface and both are bound by physical action.PEG in the Si O₂@PEG of XRD was still crystalline.The observation of the changes of the Si O₂@PEG sample by the camera showed that the Si O₂@PEG can still maintain its relatively stable structure when the outside temperature rose above the PEG melting temperature.Mechanical properties test results showed that when the amount of Si O₂@PEG was 30 phr,the mechanical strength of the composites was the best,and the tensile strength could reach 19.6 MPa,it was 55.6%higher than the 12.6 MPa of TPI/30PEG,and the R_f of the composite could reach 34.48%and 95.40%,and the R_r was 30.48%and 66.60%,respectively.