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Chemical recycling of fiber-reinforced epoxy resin using a polyethylene glycol/NaOH system

A polyethylene glycol/ NaOH system has been used for chemical recycling of fiber/epoxy resin composites. Solvolysis of the composites based on different fibers, i.e. two PAN-based carbon fibers (Torry T300, T700S) and two glass fibers (non-alkali glass fiber and medium-alkali glass fiber), have been compared. The solubilization degree increases with rising reaction temperature, reaction time, as well as NaOH amount. After reacting at atmospheric pressure for 4 h at 200℃ with 0.1 g NaOH/g composite, a high decomposition efficiency of 84.1–93.0% has been obtained. Scanning electron microscopy analysis shows that the two recovered carbon fibers and the non-alkali glass fiber have a texture similar to the as-received fibers, except that some residual resin adheres to the surface, while the medium-alkali glass fiber is damaged during recycling. Accordingly, the recycled carbon fibers and the non-alkali glass fiber retain 94–96% of their original strength, while the tensile strength of the recycled medium-alkali glass fiber decreases to below 90% of this value. The two carbon fibers were further characterized using X-ray photoelectron spectroscopy and X-ray diffraction. The carbon structure is slightly oxidized and the degree of graphitization of the recovered carbon fibers slightly decreases.