Study Of Thermal Decomposition Behavior Of Carbon Fibre Reinforced Epoxy Resin Composites At Different Oxygen Concentration

With the increasing use of CFRP, substantial waste is generating during manufacture as well as at the end of the service life of the composite. In order to reclaim the valuable carbon fiber in CFRPs and to avoid landfill of CFRPs, various recycling techniques have been developed. Pyrolysis is a common method for recycling CFRP. However, carbonized residue is preferred to form on fiber surface. Thermal processing in air could eliminate the carbonized residue but the mechanical strength of the inherent fiber tends to be damaged by oxidation.For the purpose of reclaiming clean carbon fibers without severe reduction in tensile strength,we investigated the influence of the oxygen concentration in nitrogen on the thermal decomposition of carbon fiber reinforced 4, 4'-diaminodiphenylmethane cured epoxy resin composites.A kinetic study on the thermal degradation of CFRP was presented. The gas 5%O2 was a mixture of high purity nitrogen and high purity oxygen at a volume ratio of 95 : 5. The gas 10%O2 was a mixture of high purity nitrogen and high purity oxygen at a volume ratio of 90:10. The degradation behavior was investigated by means of dynamic thermogravimetric analysis ( TG ) in 5%O2, air and inert atmosphere at heating rates from 5 to 20 ?/min. The overall rate equation can be modeled by an Arrhenius-type equation, from which the kinetic parameters such as the activation energy and the pre-exponential factor were determined by using Kissinger method and FWO method. The probable decomposition mechanism function of CFRP was also obtained by Coats Redfern method. The information about the kinetic parameters based only on thermal degradation data has been used for a quick estimation of lifetime of CFRP at different temperatures and atmosphere. The pyrolysis pocess of CFRP in oxygen-containing gas also included the process in nitrogen. The increase of oxygen concentration accelerate the oxidation of carbonized residue.The pyrolysis experiments were conducted in a fixed bed reactor. 5%O2, 10%O2 and air were used as reactant gas. Temperature was proved to be most critical to the decomposition of CFRP. Oxygen concentration should be carefully designed. The properties of the recycled carbon fiber were characterized using single-filament tensile test, SEM and XPS. With the increase of oxygen concentration, reaction time and temperature, the mechanical properties of recovered fibers decreased and the deposited char on the fiber was removed. The recovered fibers in 5%O2 show much better mechanical properties than that of the fibers recovered in 10%O2 and air. Tensile strength of 650-5%-45 was about 83% of the strength of virgin fiber.The content of the oxygenated functional groups increased after treating in oxygen containing atmosphere. The surface energy of fibre recycled had no obvious change. The end of this paper includes the mass balance of the decomposition reaction and a detailed characterization of the decomposition products of epoxy resin. The components were identified by GC and GC/MS. The decomposition products in nitrogen were different from that in oxygen-containing gas, which indicated the oxidation of epoxy resin.