Reusing Bisphenol—A Type of Epoxy Polymer Recyclates from the Solvolysis of CFRP

Abstract

Carbon fiber-reinforced polymer (CFRP) composites are highly functional composites which comprise two major components: the polymer matrix and the carbon fiber. Lightweight and having high strength, CFRPs have been used heavily in various industries such as wind, aerospace and automobile. The increasing demand and extensive use led to a huge quantum of CFRP waste from both end-of-life and during manufacturing. Out of this waste, only 2% is recycled, the rest are disposed of via incineration and/or landfill. This has raised significant environmental and sustainability concerns. The current state-of-the-art way of recycling CFRPs is by pyrolysis. However, through the pyrolysis process, the polymer used in the CFRPs, which accounts for around 65–75 wt.%, cannot be recovered and reused. In most publications, the focus on CFRP recycling was on the recovering of the more valuable carbon fiber. The polymer matrix is mostly burnt off, in the case of pyrolysis, or disposed. To obtain full circularity, recovering and reusing both the carbon fiber and polymer is necessary. In this paper, we primarily focus on the recovered bisphenol-A type of epoxy polymer (REP) obtained from solvolysis digestion of CFRP and explore the feasibility of reusing this REP by blending it with pristine epoxy in various compositions to create new materials. The physical and mechanical properties, including decomposition temperatures (Td), glass transition temperatures (Tg), storage modulus, loss modulus, flexural and tensile strength, were characterized using thermal gravity analyzer (TGA), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA) and Instron universal tester. The results indicate a decrease in glass transition and decomposition temperature, and mechanical properties as the blending composition increases. This suggests that the total blending composition should not exceed 10 wt.%, with an optimal range potentially falling between 5 to 6 wt.%.