Study On The Effect Of Microcapsule And Carbon Fiber Modification On The Properties Of Unsaturated Polyester Composites

Unsaturated polyester?UP?composites have been widely used in aerospace,electronics and architecture because of their excellent mechanical properties,good heat resistance and fatigue resistance.However,the material will produce micro cracks in the long-term use,if the micro cracks are not healed in time,which will lead to changes in the mechanical properties and dimensional stability of the material and affect the performance of the material.The micro encapsulated functional materials can not only improve the toughness of the composites,but also can realize the function of automatic response and self-healing.However,due to the differences of the microcapsule formulation system and the synthesis process lead to the great difference of microstructure and the degree of interface bonding with the substrate,which affects the basic properties of the composites.Carbon fiber?CF?has high specific strength,high modulus,low coefficient of friction properties and has been widely used in composites.However chemically inert,low surface energy,and poor resin adhesion of it limits development in composites.Therefore,it is urgent to solve the problem that how to realize the self-healing function of the composites is the long-term stability and meanwhile to reduce the performance degradation of the composites due to the introduction of microcapsules and carbon fibers.In this study,the microcapsules?MUF?were synthesized with melamine urea formaldehyde resin as wall material and epoxy resin?E-51?as core material by in-situ polymerization,which were used in carbon fiber reinforced unsaturated polyester?CF/UP?composites.The surface morphology of MUF was observed by OM and SEM.FTIR was used to characterize the chemical structure of MUF,CF/UP composites and MUF/CF/UP composites.TGA,DMA,izod impact device and universal tensile testing machine were used to test the thermodynamic properties and self-healing properties of the composites.The results show that when the content of CF and MUF is 1wt% respectively,MUF/CF/UP composites have better thermal properties,mechanical propertiesand self-healing efficiency.However,due to the poor compatibility of MUF and CF with UP matrix,the addition of MUF and CF has an impact on the properties of composites.In order to solve the above problems,CF and MUF were modified by surface treatment and chemical grafting.The effects of modification agent,modification and modification on the microstructure,thermal and chemical properties of CF and MUF were investigated.The effects of different modification process of CF and MUF on the thermal properties,mechanical properties and self-healing efficiency of MUF/CF/UP composites were studied.FTIR was used to characterize the chemical structure of MUF,CF and composites before and after modification.SEM was used to observe the surface morphology of MUF and CF before and after modification,and the dispersion of MUF and CF in the composites.SEM was used to observe the surface morphology of MUF and CF before and after modification,and the dispersion of MUF and CF in the composites.The effects of self-healing components on the thermodynamic properties and self-healing properties of UP composites were studied by using TGA,DMA,impact testing machine,hardness tester and universal tensile testing machine.The results show that the surface roughness and active functional groups content of CF treated by H₂O₂ and HNO₃ for 20min?OCF and OCF2?and KH-570 grafting modification of CF?KCF?have increased,which improved the interfacial compatibility between CF and UP matrix.Among them,the mechanical properties of MUF/OCF_/UP composites are better than those of MUF/OCF2/UP composites.The mechanical properties of MUF/KCF/UP composites are the best among the three,and the self repairing efficiency is high,up to 67.03%.Indicating that after modification of carbon fiber can improve the interface compatibility and improve the properties of the composites.KH-151 and KH-570 surface treated microcapsules at 60??MUF1 and MUF2?and KH-570 graft modified microcapsules?MUF₃?have regular shape,rough surface,and more compact binding with UP matrix.It can be concluded that the mechanical properties of MUF2/OCF_/UP composites are better than those of MUF1/OCF_/UP composites,and the mechanical properties of MUF₃/OCF_/UP composites are the best among the three.The self-healingefficiency is high,which can reach 70.77%.Indicating that the modification of microcapsules can improve the interfacial bonding force between the microcapsules and the unsaturated polyester matrix material.