Chemical Recycling of Polycarbonate Based Wastes Using Alkaline Hydrolysis Under Microwave Irradiation

In this study, depolymerization of polycarbonate with water, in a microwave reactor, is proposed as a recycling method. The objective was to investigate if depolymerization of PC could be carried out using microwave irradiation in relative mild experimental conditions. Reaction with water (hydrolysis) was investigated in an alkaline (NaOH) solution and using a phase transfer catalyst (1-hexadecyl trimethyl ammonium bromide). After proper treatment of the hydrolysis product the monomer bisphenol-A was obtained in each case. All experiments took place in a sealed microwave reactor in which the reaction pressure and temperature, as well as the microwave power were continuously controlled and recorded. Experiments under constant temperature were carried out at several time intervals. The depolymerization product was analyzed and identified by FTIR measurements. It was found that depolymerization is favoured by increasing temperature, time and alkali concentration. Complete PC degradation can be obtained at 160 °C, after 40 or 10 min of microwave irradiation time using a 5 or 10 % w/v NaOH solution. Finally, higher-than-90 % degradation was achieved in waste CDs after alkaline hydrolysis under microwave irradiation at 160 °C for 10 min. These results, confirm the importance of the microwave power technique as a recycling method of PC-based waste plastics resulting besides to monomer recovery in substantial energy saving.