Structure And Characterization Of P(AN-AM-MAA) Copolymer

The pre-oxidation process is a very important step in the entire process of preparing carbon fiber.During the pre-oxidation process,the molecular chain undergoes a cyclization reaction,an oxidation reaction and a dehydrogenation reaction,and the linear molecular chain is converted into a conjugated ladder structure,thereby improving the thermal stability of the polymer.The reaction mechanism of PAN homopolymer in the heat treatment process is free radical polymerization,the radical polymerization reaction is rapid,and the heat cannot be discharged in time,so that the temperature is accumulated,and the temperature is too high to cause the fiber filament to break.In order to obtain high performance carbon fibers,it is currently preferred to add the first or second comonomer.The addition of comonomer changes the reaction mechanism into ionic polymerization,which relaxes the exothermic heat of the PAN precursor in the pre-oxidation process,makes the reaction exotherm controllable,and accelerates the cyclization reaction of the linear molecules of the polymer.In this thesis,two copolymers of acrylamide(AM)and methacrylic acid(MAA)were used to study P(AN-AM)copolymer,P(AN-MAA)copolymer and P(AN-AM-MAA)copolymer.Structural evolution and thermal behavior during pre-oxidation.(1)The P(AN-AM)copolymer and the P(AN-MAA)copolymer reduce the onset temperature of the exothermic peak of the polymer compared to the PAN homopolymer,and the exothermic peak is more broadened.By calculating the kinetic parameter Ea during the cyclization reaction using the Kissinger and Ozawa equations,the Ea values obtained by the two methods are almost the same,indicating that the kinetic parameters we obtained are credible.(2)By calculating the degree of cyclization of P(AN-AM)copolymer and P(AN-MAA)copolymer and PAN homopolymer in the pre-oxidation process,the binary copolymer is treated at the same heat treatment temperature for the same time.The degree of cyclization of the P(AN-MAA)copolymer is higher than that of the P(AN-AM)copolymer and the PAN homopolymer,indicating that the MAA monomer promotes the cyclization reaction higher than AM monomer.(3)Compared with the binary copolymer,the P(AN-AM-MAA)terpolymer has a lower starting temperature of the exothermic peak of the P(AN-AM-MAA)terpolymer,Although the heat release is increased,the heat release rate is lowered.The degree of cyclization reaction is higher at the same heat treatment temperature and the same heat treatment time,indicating that the simultaneous addition of the two monomers is more favorable for the cyclization reaction.