Forming Process And Micro Structure Of Self-bonding Mesophase Pitch Based Fibers

Self-bonding material based on mesophase pitch fiber is prepared by press forming rely on the bond prosperity of pitch fibers and the forming technology is simple.It has broad application prospects.However,there is less literature reported the factors affecting the forming process,such as the oxidation weight gain,the hot-pressing condition,and the thermal deformation prosperity of pitch fibers.Therefore,the forming process and microstructure of self-bonding material based on mesophase pitch fiber are studied in this paper.The peroxidation of three kinds of pitch fiber(MP-1,MP-2 and MP-3)was simulated by Thermo Gravimetric Analysis(TGA).On this basis,five kinds of oxidized fibers of three different mesophase were prepared.Experiments show that the oxidation weight gain of pitch fiber has little different with it simulated by TGA,so the pitch-based peroxided fibers of different oxidation weight gain can be prepared with the help of TGA.The effect of mould and pressure on the preparation of self-bonding board based on mesophase pitch fiber were studied by The Mechanical Analysis(TMA),and the deformation behavior of pitch fiber with different oxidation weight gain and section structure were investigated by TMA.The results showed that under 0.092MPa pressure,the crack in self-bonding board is small;the self-bonding board had a good molding effect.The fiber arranged closely and the self-bonding board had a good molding effect which was prepared by "U" mould.When the oxidation weight gain is about 2%,the deformation degree is about 36%,the fibers have a good bonding condition.The finding by TMA is that:With the oxidation weight gain increasing,the deformation degree of fiber in radial direction decrease,the porosity of self-bonding board increase,and the fiber is difficult to deform.When the fibers have a high oxidation weight gain,the deformation in radial direction has something to do with section structure of fiber,and the order is radial structure<edge-random and core-wrinkle structure<random structure.The microstructure of self-bonding board was investigated by Scanning Electron Microscopy(SEM).Result showed that for the fiber of MP-1,when the oxidation weight gain is 2.1%,the surface of self-bonding board is smooth,and fibers are arranged closely and adhered together perfect,but after the self-bonding board is carbonized,it would result in remarkable trends of cracking of self-bonding board based on carbon fiber.For the fiber of MP-2,when the oxidation weight gain is 1.8%,the self-bonding board had good cohesiveness,nevertheless,after the carbonization,the molecular orientation structure formed during the spinning process cannot be fixed because of the low oxidation during the peroxidation.However for the fiber of MP-3,the self-bonding board based on pitch fiber had a good molding effect with the oxidation weight gain of 1.9%and 2.8%,after carbonization the surface of self-bonding board based on carbon fiber with the oxidation weight gain of 1.9%had many micro holes,and yet the board with the oxidation weight gain of 2.8%had little and the crack between fibers is small.