Preparation And Properties Of Shape Memory Material With Rigid-flexible Structure

Shape memory polymers(SMPs)are classes of smart polymer materials that can fix one or more temporary shapes and sense external fields(such as heat,electricity,light,chemical induction,etc.)stimulation to recover to initial shape.SMPs have unique application value in fields of biomedicine,self-repair,intelligent textiles,controlled release of drugs,aerospace,etc.Because of having advantages of light weight,low cost,good processing technology,high deformation.Therefore,it is of great significance to research new shape memory polymer materials.In this paper,shape memory polyurethane,shape memory epoxy resin composites,and multi shape memory epoxy resins with rigid-flexible structures were prepared,and the effects of the material structure on their properties were studied.The specific research contents are as follows:1)Polyurethanes(PTMGUs)with pyridine rings at the ends were prepared by a two-step method.The total reflection infrared spectra showed that shape memory polyurethanes were successfully prepared.The TGA curves show that the heat-resistance of PTMGUs are good,and the initial decomposition temperature are all higher than 220?.The DSC curves confirm that the melting temperature of polyurethane are the shape memory responsive temperature.Shape memory cyclic tensile DMA tests show that the average fixation rate and recovery rate of PTMGUs are all higher than 90%.Polyurethane PTMGU₃(hard segment mass fraction is 35%)has the best shape memory property,of which average fixed rate is 96.9%and average recovery rate is 99.5%.The shape recovery process of polyurethane at 60?was recorded via video.It was found that shape memory polyurethane could recover to its original shape in 6 minutes.2)Epoxy resin EP5-60%of which shape memory fixed rate is 94.7%and recovery rate is 94.4%was selected as the matrix material,and modified Fe₃O₄ nano particles were doped with EP5-60%to prepare nano Fe₃O₄/epoxy shape memory composites.The FTIR spectra and TGA curves show that the magnetic Fe₃O₄ nano particles are successfully modified by silane coupling agent(KH550),and the thermal responsive recovery temperature is 80?according to DSC tests.Tensile experiments show that when the doped amount of modified Fe₃O₄ nano particles is 7wt%,the maximum tensile strength of the composite is 29 MPa and the maximum elongation at break is 37.3%.The bending recovery test showed that the thermal responsive shape memory fixed rate and recovery rate of the composite are all increased first and then decreased,as increasing the content of modified Fe₃O₄nano particles.The thermal responsive shape memory fixed rate(R_f)was 99%and the recovery rate(R_r)was97.9%,when the contents of modified Fe₃O₄ nano particles were 7wt%.The magnetic responsive shape recovery processes were recorded via videos,It was found that when the contents of modified nano Fe₃O₄ particles were 7wt%,the magnetic responsive recovery rate was 93.3%,continued to increasing the contents of the modified nano Fe₃O₄ particles.Although the magnetic responsive recovery rate of composites can slightly increased,the thermal responsive shape fixed rate and recovery rate of composites are reduced,and the mechanical properties of composites are also greatly reduced.3)Furan rings were introduced into the side chain of epoxy resin,and cross-linked network polymers EP-DA were prepared after Diels-Alder reaction between 1,8-bismaleimide and furan rings.The FTIR spectra shows that polymers EP-DA were successfully synthesized.The TGA curves shows that the thermal stability of cross-linked polymer did not change significantly when increase the content of the polyethylene glycol glycidyl ether(PEGDE)flexible segment.DSC tests show that the glass transition temperatures of EP-DA-10%,EP-DA-20%,and EP-DA-30%in low temperature region are 46?,42?,and 31?,respectively.The optimal temperature for DA positive reaction is 78?,and the optimal temperature for DA reverse reaction are 130?,125?,and 134?,respectively.The shape memory recovery temperature of the polymers in this paper were 60?and 90?.4)One-way shape memory bending recovery tests found that the shape memory fixed rate increased first and then decreased,and the recovery rate increased,as increasing the contents of flexible chain PEGDE.The recovery time of polymers EP-DA at 90?was shorter than that at 60?.The two-way shape memory bending angle recovery test process shows that the polymer EP-DA-30%only needs 320 s to recover to initial shape,while EP-DA-10%and EP-DA-20%need 460 s.The shape memory DMA tensile test shows that the polymer has multi shape memory effect.The higher contents of PEGDE flexible chain,the larger the amount of deformation under the same external force.the larger the amount of deformation,the greater the fixed rate and recovery rate of the polymer EP-DA.