2.4. Gel Permeation Chromatography (GPC)

Weight average molecular weight (M_w), weight average molecular number (M_n), and molecular weight distribution (M_w/M_n) of polymers were measured using gel permeation chromatography (EcoSEC HLC-8320GPC, Tosoh Bioscience, Tokyo, Japan) equipped with a refractive index detector. GPC calibration was conducted using PS standards (Agilent EasiVial PS-H 4mL, Santa Clara, CA, USA).

Virgin and recycled polymers were dissolved in tetrahydrofuran solvent (THF) with a final concentration of 1 mg/mL. Polymer solutions were pre-filtered using a 0.22 μm syringe filter. The column temperature was 40 °C, and the solvent flow rate was set at 0.35 mL/min. Moreover, the average number of random chain scissions per unit mass of each polymer (n_t) was calculated according to the following Equation (1).

where, n_t is the number of chain scission at a given reprocessing cycle, M_n0 and M_nt represent the number average molecular weight of samples after the initial and a given processing cycle, respectively.