**2.3. Experimental method**

In this study, we used a reactor vessel with a volume of 100ml and added 0.5g of flexible PVC crushed to a maximum particle size of 1mm and 50ml of NaOH solution. The solution was continuously agitated. The container containing the sample was set on the microwave heater and the sequence program was then started for microwave irradiation according to the preprogrammed target reaction temperature, heating time, temperature hold time, temperature elevation time and other parameters. The reaction start time was defined as the time when the solution in the vessel reached the set temperature. Then the temperature was maintained for the specified time. NaOH was prepared at concentrations of 2, 4, 6, 8 and 16mol/l, and the reaction temperature was set at 100°, 150°, 200°, 225° and 250°C. After the temperatures hold time had elapsed, agitation was stopped and the reaction products were cooled to room temperature. Then the solution was passed through a 0.45-mm polyvinylidene difluoride (PVDF) filter to separate the residue and filtrate, and then distilled water was added to the filtrate to prepare a 50-ml reaction solution. The residue was then washed with distilled water and dried by decompression; it was then weighted and underwent elementally analyzed. In the case of using NaOH/EG solution, the flexible PVC (Table 1.) with a particle size of about 1 mm was charged with 50 ml of EG were placed in the reactor vessel. NaOH was prepared at concentrations of 0.5, 1, 2, and 4 mol/l. The reaction temperature was set at 100, 120, 140, and 160°C.
