A REVIEW ON RECYCLING OF THERMOSETS

Abstract

Thermosets are a type of plastics that pose a major problem when it comes to easy reusability and recycling because they become irreversibly rigid when subjected to progressive increase in temperatures. Epoxy resins, Phenol Formaldehyde, and Polyurethanes are a few of the many thermosets that are widely employed in several different fields. The rigid, brittle, opaque thermosets, in general, possess qualities like good mechanical strength at elevated temperatures, good chemical resistance in addition to even being self-extinguishing at times (mostly with the help of additives), with low smoke emissions, as highlighted by the British Plastics Federation. However, these properties which serve as an advantage to the end product also affect their recyclability, which is difficult and limited, because of their ability to undergo cross-linking on heating, which ultimately results in the formation of strong covalent bonds that cannot be broken easily. Several commercial techniques are now available for recycling thermosets, which include - Mechanical Processing, Thermal Processing and Chemical Processing. These methods demand higher amount of energy for offering feasible results. There are several studies that have focused on degradation (which is the essential first step that progressively leads to recycling) of thermosets. This review highlights the importance of such studies, techniques and methodologies on aspects including feasibility, cost, sustainability and technological innovation.