Depol Ymerization Mechanism Of Epoxy Resin Cured With Amine And Investigation On Recovery Technology Of Cfrp

Carbon fiber reinforced composites (CFRP) have been widely applied in fields ofaerospace, automobile, shipbuilding, and sports due to their excellent properties suchas high modulus, good thermal resistance, lightweight and high-strength. However,the high output of CFRP to meet the rising market demands has produced a greatamount of CFRP wastes, which would bring serious burden to the environment.Epoxy resin (EP) are the greatest consumption in production of CFRP. But they weredifficult to be dissolved with conventional solvent or melted due to theirthree-dimensional network structure after cured. Therefore it has become animportant topic proposing a perfect recovery method to dispose the CFRP wastes.In this article, the existing and potential technologies used for the recycling ofCFRP wastes have been introduced fully. Based on this, the research program whichepoxy resin cured with amine and CFRP were degraded in nitric acid using solventrecovery method under atmospheric pressure was established. The effects ofdifferent decomposed conditions such as reaction time, the nitric acid concentrationand reaction temperature on degradation efficiency were discussed. The optimaldecomposed conditions were assessed with degradation rate and monofilamentstrength retention of recycling carbon fibers as indexes. Frontier Transform InfraredSpectroscopy (FTIR) and Scanning Electron Microscope (SEM) were employed toanalyze decomposition products and depolymerization mechanism was revealed.Based on the determination of reaction rate, the reaction kinetics was studied and thekinetic model was initially established.The results suggested that the degradation rate of resin was increased withreaction temperature, nitric acid concentration and reaction time increasing, of whichthe concentration was the most important factors. The degradation rate of resin inCFRP reached 99.18% after 23 hours in 8mol/L nitric acid at 95 degrees Celsius.Differential thermogravimetric (DTG) and Scanning Electron Microscope (SEM)analysis indicated that the surface of recycling carbon fibers were relatively pure, theresin content was little, and slight oxidation etching on the surface. Themonofilament strength of recycling carbon fiber was reduced to a certain extent, butthe retention was still up 80% which can be used for recycling and reuse.Macroscopic reaction rate and activation energy were determined and the kinetic model was established. The degradation rate increased obviously by controllingnitric acid concentration with constant and resin decomposed completely after 5hours. The degradation products were analyzed by FTIR and the depolymerizationmechanism of epoxy resin cured with amine in nitric acid was proposed. The resultsshowed that the peak of C-N bond (1112cm-1) reduced sharply and peak ofnitro-benzene (1537 cm-1) appeared in degradation products. This demonstrated thenetwork structure of cured epoxy resin was destroyed in nitric acid, C-N bonds werecleaved and the original resin was nitrated.