Investigation of degradation products produced by recycling the solvent during chemical degradation of fiber-reinforced composites

Abstract

Recycling of fiber-reinforced thermoset composites using chemical solvolysis has been investigated thoroughly in recent years, where solvents such as water, alcohols and ketones have been used. However, high costs are related to the use of organic solvents, decreasing the sustainability of the process. In this study, acetone has been used as the organic solvent. To increase the sustainability of the process, the solvent was recycled in eight consecutive batches using new glass fiber-reinforced composites in each recycling. No additional amount of acetone was added, resulting in a reduction of solvent consumption by 88%. It was found that the recycled solvent became increasingly more concentrated with degradation products from the epoxy resin and compounds produced by acetone aldol reactions. These degradation products promoted and enhanced the degradation of the composite. Among the compounds produced by acetone aldol reaction, the industrially important bulk chemical mesityl oxide accounted for 68–79% of the total chromatographic peak area. Simultaneously, with the optimization of a process for converting composite waste into its constituent (fibers and resin), valuable bulk chemicals can be produced to increase the overall commercial interest.

Evaluation of the presence of potential hazardous substances from plastic and textile fibre recycling

“…In chemical recycling a liquid medium is used to degrade and dissolve the thermoset matrix so the reinforcing carbon fibres can be regained. Similar as to pyrolysis, the degraded and dissolved organic substances can be reclaimed from the solvent and be re-used as molecular building blocks (Kuang et al, 2018: Sokoli et al, 2017. The cracking of the thermoset matrix, mostly flexible or rigid foam mixtures, produces a polyol which can be reintroduced into the PU raw material cycle.…”

Life Cycle Perspective of Liquid Epoxy Resin Use in the Automotive Industry

“…One of the most important tasks of producers is decreasing vehicle weight, which leads to the increasing use of materials such as plastics, aluminum, and composites instead of ferrous metals. Aluminum recycling is technologically easier and economically more feasible than plastics recycling [33]. Car designers consider plastics one of the critical components, as only larger parts get recycled.…”

“…This is related to efforts toward decreasing the many different kinds of plastics used. Marking their type also makes identification during dismantling easier [33]. After dismantling, the vehicle is broken and crushed in a shredder.…”

“…Among the other technologies that can process ASR are pyrolysis or gasification. However, the benefits of processing ASR in these technologies are very little documented [33,38]. Pyrolytic processing is especially suitable for the heavy fraction of ASR.…”

“…Reinforced epoxy resin is used in thermosets [25] in a number of applications [26][27][28][29][30]. These materials are very difficult to recycle [31][32][33], and research on recycling thermosets is still current [34]. In this paper the possibilities for epoxy resin usage in the automotive industry and its environmental consequences using life cycle assessment are analyzed.…”