Chemical recycling of poly(bisphenol A carbonate)
Plastics are excellent materials: they are light weight, long-lasting, easy to manufacture, and relatively cheap. The ongoing development of new polymers and their production technology has produced a vast range of plastics with properties ranging from soft to strong, from brittle to ductile, and from flexible to rigid. Thus, they make our life versatile and convenient in many areas, e.g. transportation, home appliances, and digital devices. However, once their designated job is finished, they become a problem because they do not degrade on their own. Since the 1990s, the problem associated with cumulated plastic wastes has been addressed and various solutions have been proposed. Among various kinds of plastics, this review is focused on the recycling of poly(bisphenol A carbonate) (polycarbonate or PC), a leading engineering plastic with high strength and transparent properties for application in electronics, containers, automobiles, safety, and optics. Considering its production quantity of over 5 million tons a year and the health concern on bisphenol A as a possible xenoestrogen, its collection and recycling should gain more attention. Over 30 years, considerable research effort has been exerted on polycarbonate recycling. Among many methods, in this review, research studies on the chemical recycling of poly(bisphenol A carbonate) are collected and summarized, which may turn after-use plastics into valuable chemical feedstocks. With suitable process development, circulation between the monomer and polymer can be achieved, which could successfully maintain the current industries and potentially eliminate waste. Various methods for polycarbonate degradation into useful materials are categorized according to the type of pyrolysis, hydrolysis, alcoholysis, aminolysis, and reduction to understand the present and the future of PC degradation recycling.