A Review of Recyclable Thermoset (Circular Economy)

Abstract

Because thermosets become irreversibly inflexible when exposed to gradual temperature increases, they present a significant challenge to easy reusability and recycling. Among the various thermosets that are widely used across different industries are epoxy resins, polyurethanes, and phenol-formaldehyde. According to the British Plastics Federation, rigid, brittle, opaque thermosets generally have low smoke emissions, good mechanical strength at high temperatures, good chemical resistance, and the ability to occasionally self-extinguish (mostly with the aid of additives). But because of their capacity to undergo cross-linking upon heating, which ultimately results in the development of strong covalent bonds that are difficult to break, these qualities that benefit the final product also have an impact on their recyclability, which is limited and challenging. To recover valuable reinforcing fibers, the article aims to provide an overview of the most popular thermoset composites and the state of the art in thermoset recycling. In this review, the focus is on economic and environmental implications as well as the creation of reusable composites made from glass and plant fibers, which increases their applications in biomedical devices, coatings, paints, and sustainable transportation. Thermoset materials and their composites have a long service life and therefore are used as insulators in wind turbines, aircraft, and building constructions.