Decomposition Of Carbon Fibre Reinforced Polymer Composites And Characterization Of Decomposition Products

Carbon fibre reinforced polymers(CFRPs)have been extensively used in the aerospace,automobile and sports industries due to their outstanding mechanical properties,low weight and corrosion resistance.As the usage of CFRPs increased,a soaring amount of waste CFRPs generates.The sovolysis process is a better recovery method,which is not just using the depolymerized epoxy resin as material but does little harm to mechanical properties of carbon fibre(CF).However,the high operation pressure nature of many solvent systerms brings the problem of batch-type operations and makes them difficult to scale up.In order to realize the controlled and commercialized degradation of epoxy resin,the solvent system under atmospheric condition is a candidate,but the degradation rate of epoxy resin is slow in organic solvent at atmospheric pressure.The addition of catalysis can increase the reaction rate,but the catalysis is difficult to remove after the reaction.Therefore,two types of atmospheric decomposition reaction systems on epoxy resin cured with imidazolium and acid anhydride compounds were designed,and the effects of reaction systems and conditions on the decomposition of epoxy resin as well as the properties of recycled CFs were evaluated in this thesis.To begin with,the decomposition behavior of the CFRPs cured with 1-cyanoethyl-2-ethyl-4-methylimidazole was investigated in molten potassium hydroxide at 285-300 ?.The decomposition rate of epoxy resin increased with a rise of temperature.The decomposition products of epoxy resin in KOH was separated and analyzed by X-ray diffraction(XRD),fourier transform infrared spectroscopy(FTIR),gel oermeation chromatography(GPC)and matrix-assisted laser desorption/ionization time-of flight(MALDI-TOF).A possible thermolysis mechanism for the decomposition of epoxy resin was proposed.The recovered CFs were characterized by scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS)and single fibre tensile test.The surface of recovered CFs was clean and no obvious damage of fibres was observed on the surface.The surface C—OH decreased and COOH increased with increasing temperature.More than 97% of the tensile strength of the virgin CFs was retained,and the tensile modulus of the fibres was also not evidently degraded.Meanwhile,the real-world CFRP wastes containing various fillers such as thermoplastics,paints,sealants and glass fibres were also decomposed in the molten KOH.The decomposition reaction of the epoxy resin cured with methyl tetrahydrophthalic anhydride was studied in organic base/ethylene glycol under a moderate condition(180 ? and atmospheric condition).N-methyl-4-piperidinol with good catalytic efficiency could be distilled off together with ethylene glycol after the reaction.Re-using experiment verified that the yield of decomposed epoxy resin was still up to 90.3 wt % in the third recycled fraction.The possible decomposed mechanism of epoxy resin was that the ester bonds were scissored under the role of alcohol oxygen anions.