Preparation And Properties Of Self-healing SMPI/ZnO And SMPI/POSS Composites

Many materias in production and life will produce various cracks and damages due to external forces or temperature changes during use,and the mechanical properties of the materials will be reduced,which will limit the service life of the materials.The self-healing polymer material simulates the self-repair principle of natural organisms after injury.At present,research reports focus on self-healing materials at low temperatures,so it is of great strategic significance to improve the self-healing properties of materials under high temperature environments.Shape memory polyimide(SMPI)is a smart polymer material with high mechanical properties,chemical resistance,high and low temperature resistance,and is used in high-temperature actuators and civil aviation,industrial and military fields.Among the metal oxides,zinc oxide(ZnO)is a multifunctional inorganic semiconductor with high thermal conductivity and a common chemical additive.POSS is a new type of nanomaterial with high molecular rigidity,high thermal stability,and oxidation resistance,and is often used for material modification.In this paper,SMPI is compounded with zinc oxide and POSS to maintain the excellent performance of polyimide,while preparing a polymer material that can adapt to high temperature environment and can self-repair quickly and repeatedly.It is expected to be used in forward-looking fields such as aerospace and electronic equipment.In this paper,SMPI matrix was prepared by in situ polymerization with 4,4'-bis(4-aminophenoxy)biphenyl(BAPB)and 3,3',4,4'-diphenyl ether tetraformic dianhydride(ODPA)as monomers.Zinc oxide(ZnO)was introduced into the matrix by adding zinc acetylacetone in situ synthesis method to avoid the agglomeration of particles in the matrix.SMPI/ZnO composites were prepared by introducing it into polyamidoic acid(PAA)after gradient curing and heating.Compared with SMPI matrix,the T_gof the composite increases to 283?,the hardness increases to 25.547hv,and the thermomechanical properties and shape memory properties are improved obviously.SMPI/3wt%ZnO has excellent self-healing properties at high temperature.The qualitative observation under polarized light microscope shows that the composite material can be scratched and repaired for 6 times consecutively,and the self-healing time is as short as 1s,and the composite material has high recovery stress after repair.The mechanism of self-healing properties was attributed to shape memory assisted self-healing(SMASH)and the migration of zinc oxide nanoparticles in SMPI.In this paper,SMPI/EP-POSS materials were prepared by adding POSS containing different R groups into SMPI by direct introduction method,and the characterization test was carried out.The results show that the thermal mechanical properties and shape memory properties of the composites are significantly enhanced than those of SMPI matrix.The storage modulus of the composites increases to 3270.00 MPa,which is15.5%higher than that of pure SMPI.In this paper,it is proved that the introduction of EP-POSS nanoparticles into SMPI matrix can significantly enhance the self-healing property of SMPI.When the content of EP-POSS is 5mass%,the composite has the best self-healing property.Qualitative observation under polarized light microscope showed that the composite could be repaired for up to 20 times continuously,and the self-healing time was short,and the composite had high recovery stress after multiple repairs.The self-healing mechanism of SMPI/5wt%POSS-1 is achieved by the shape memory assisted self-healing(SMASH)and the migration of POSS-1 nanoparticles.