where Ws is the dry insoluble sample mass (g), Wi is the initial mass of the sample (g), and Wo is the mass of the metal cage.
TGA tests of the surface region of the samples were conducted (Netzsch model TG 209F1 Libra) under a nitrogen atmosphere at a flow rate of 30 mL/min and heating rate of 10 °C/min, from 30 to 800 °C. The inflection point of the thermogravimetric curve was considered as the onset of decomposition.
DSC tests were conducted using an Indian calibrated Netzsch model DSC 404 F1 Pegasus, which was coupled to a computerized analysis system as per the ASTM D3417 standard testing method [17]. Samples were collected from the surface region for each testing condition, weighing between 0.9 and 1.1 mg, and placed in aluminum crucibles. The samples were subjected to a double heating/cooling cycle ranging from -100 °C to 300 °C at a heating rate of 10 °C/min under a nitrogen atmosphere at a flow rate of 20 mL/min. Under these conditions, it was possible to calculate the degree of crystallinity of PS before and after radiation exposure using Equation 4.