PC Recycling
PC Recycling
(Polycarbonate)
The discovery of Polycarbonate dates back to 1898 when Einhorn, a German chemist, observed the formation of an insoluble, infusible solid, while endeavouring to prepare cyclic carbonates by reacting hydroquinone with phosgene. In 1902, Bischoff and Hedenström obtained similar cross-linked, high-molecular-weight Polycarbonate; Dr WH Carothers extended work on the product. It was not, however, until 1953 that Bayer laboratories produced linear thermoplastic Polycarbonate of high molecular weight. In 1957 Bayer and General Electric announced independent development of PC and in the summer of 1960 both companies began commercial production.
Polycarbonates are strong, stiff, hard, tough, transparent engineering thermoplastics that can maintain rigidity up to 140oC and toughness down to -20°C or special grades even lower. The material is amorphous (thereby displaying excellent mechanical properties and high dimensional stability), is thermally resistant up to 135oC and rated as slow burning. Special flame retardant grades exist which pass several severe flammability tests.
Constraints to the use of PC include limited chemical and scratch resistance and it's tendency to yellow upon long term exposure to UV light. However these constraints can be readily overcome by adding the right additives to the compound or processing through a co-extrusion process.
Polycarbonate is available in a number of different grades dependent on the application and chosen processing method. The material is available in a variety of grades such as film, flame retardant, reinforced and stress crack resistant, branched (for applications requiring high melt strength) and other speciality grades. Also blends of PC are available with e.g. ABS or Polyesters, widely used in automotive industry.
Polycarbonate remains one of the fastest growing engineering plastics as new applications are defined; global demand for PC exceeds 1.5 million tons.
There are various methods to recycle PC. One method of recycling polycarbonate waste resin, comprises: subjecting a polycarbonate waste component to one or both of a transesterification reaction and a polycondensation reaction, wherein the polycarbonate waste component has an OH group concentration and comprises polycarbonate resin waste; and adjusting the OH group concentration of the polycarbonate waste component. Another method of recycling polycarbonate resin waste, comprises: introducing a dihydroxy compound and a carbonate diester to a mixing tank to form a mixing tank composition; directing the mixing tank composition to a prepolymerization tank to form a prepolymerization composition; melting a polycarbonate waste component, wherein the polycarbonate waste component has an OH group concentration and comprises polycarbonate resin waste; combining the prepolymerization composition with the melted polycarbonate waste component to form a combination; adjusting the OH group concentration of the polycarbonate waste component; polymerizing the combination to form a polycarbonate product; and extruding the polycarbonate product.
The process of PC recycling is a developed process, but has not finished evolving. As PC is used more and more as a raw material in various industries, it’s recycling process will be perfected through time.
Heathland searches to recycle plastics, including PC, in ways that are best suitable for people and environment. Recycling happens in-house and at partner companies in Europe and/or Asia. Since the market for plastic recycling is very international, often it is difficult to keep track of how and where scrap plastics are recycled. Heathland works with partners who are qualified, have sufficient certification, and have set quality standards for the circumstances in which plastic materials are processed. This way, the company can keep as much control as possible on the circumstances in which it’s plastics are recycled. If you are interested in this way of recycling, whether your company is a collector, manufacturer, servicer or end-user, please contact us for possibilities.