Reaction kinetics of degradation of carbon fiber-reinforced plastic in supercritical n-butanol

The high performance carbon fiber (CF) can be recycled from CF/epoxy resin (CF/EP) composites by supercritical n-butanol under the action of KOH. Influences of reaction temperature and reaction time on degradation rate of EP in CF/EP composites were analyzed, and mechanical properties of the recycled CF reinforced polypropylene (PP) composites were investigated. Catalytic degradation process of the EP curing system in supercritical n-butanol was investigated based on analysis for components of degradation liquid phase products, and the degradation kinetics model was established. The catalytic degradation kinetics equation was proposed based on the calculation of the kinetics parameters. The results indicate that reaction temperature and reaction time show obvious positive correlation to degradation rate of EP. In comparison with the original CF reinforced PP composites, the tensile strength of the recycled CF reinforced PP composites decreases by 9.2%, the bending strength decreases by 20.9%, the bending modulus decreases by 10.9%, and the impact strength decreases by 7.4%. Degradation reactions of CF/EP composites are mainly the scission of linear chains such as C—C, —O—, etc. and the scission of C—N at the cross-linked segment in the molecule segment of EP curing system, and catalytic degradation reaction order of CF/EP composites is 2, reaction activation energy is 165.2 kJ·mol^-1, pre-exponential factor is 3.62×10¹³ min^-1, and the established kinetics equation can solve the problem that the reaction temperature and reaction time can not be estimated.