Abstract
The case study presented in this paper is a follow up of a topic already examined in previous studies relating the life cycle assessment (LCA) of a chemical treatment process used to recycle a specific type of carbon fiber (CF) reinforced thermoset composite. In the present study the LCA is coupled with the life cycle cost (LCC) analysis for the economic assessment. Furthermore, the research sought to specify the best available technology for the reuse of the materials recovered through the chemical recycling process. The new LCA results are more reliable and more current than the scenario presented in the previous LCA studies. In the previous scenario the possibility to recover long carbon fibers “ready to use” was considered. This scenario, even if under investigation by the recycling company, is still not possible for technological limitations as the fibers recovered after the chemical process require further treatments before being used in thermoset composite. Consequently, a more feasible technology was investigated and, according to our laboratory research results, one practical way to recycle the CF-thermoset composites is to shred them before the chemical treatment in order to recover shredded CFs and epoxy thermoplastic from cleavable thermosets. These materials can be easily compounded together to manufacture a CF-thermoplastic composite through injection moulding as we demonstrated herein through some laboratory experiments. The LCA and LCC were accounted for the recycling process via solvolysis up to the recovery phase of the epoxy-thermoplastic resin and the short carbon fibers. The paper presents laboratory test results of the remanufacture of the two reclaimed materials for the production of a thermoplastic CF-composite.
Highlights
This company developed several products using a remanufacturing approach focused commingling of short carbon fibers obtained by pyrolysis with virgin thermoplastics to form non-woven mats
The case study presented in this paper is a further study about new formulations of epoxy resin and hardeners developed by Connora® Technologies and provided by R*Concept (Spain) in order to obtain recyclable thermosets which can be transformed into a useable epoxy-thermoplastics
The life cycle assessment (LCA) methodology is an objective procedure for evaluating energy and environmental loads related to a process or activity, carried out through the identification of the energy and materials used and waste released into the environment
Summary
The increasing use of carbon fibers reinforced polymers (CFRP) generates an increasing amount of waste, comprising end-of-life (EOL) prepregs, manufacturing cut-offs, testing materials, production tools and EOL components (Pimenta et al, 2011). This company developed several products using a remanufacturing approach focused commingling of short carbon fibers obtained by pyrolysis with virgin thermoplastics to form non-woven mats Oxidation is another thermal process for CFRP recycling, consisting in combusting the polymeric matrix in a hot and oxygen-rich flow (e.g. air at 450e550 C). The recycling process includes two main steps: one regards the crosslink cleavage in the epoxy by means of a combination of temperature and pH (acidic) required to induce the conversion of epoxy into a thermoplastic polymer that can be separated in solution from the fibers allowing the reclamation of clean reinforcing fibers; one step regarding the remanufacturing of the reclaimed products into new composites (Banatao et al, 2014). The main advantage given by this technique is the possibility to reach the full reclamation of both components (carbon fibers and the epoxy resin) allowing to use them into the remanufacturing process for the production of new polymer reinforced composites. The present paper covers the LCA analysis of the reclamation process and on the reclaimed products, it presents the use as a novel composites obtained by reprocessing the recovered thermoplastic with the reclaimed fibers using standard compounding and injection moulding used for thermoplastic composites
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