Effect of cold plasma pretreatment on biodegradation of high-density polyethylene (HDPE) and polystyrene (PS)

Cold atmospheric plasma (CAP) pretreatment of high-density polyethylene (HDPE) and polystyrene (PS) was investigated to evaluate its effect on biodegradation. Weight and wettability measurement, surface topography, and roughness analysis were examined for physical properties evaluation. Fourier-transform infrared spectroscopy (FT-TR) analysis was conducted to understand the possible chemical transformation. Based on biofilm formation, the highest microbial colonisation was observed on the sample treated with CAP pretreatment + biotreatment, which was 0.56 and 0.19 (at OD 595 nm) for HDPE and PS, respectively. A biodeterioration effect characterised by weight loss and changes of hydrophobicity in which hydrophobicity reductions of 5.1 ± 0.64% and 12° ± 0.35° were observed with the pretreated HDPE within 50 days, respectively. No physical weight loss was detected in the PS sample, but significant surface corrosion was observed. Atomic force microscopy (AFM) also showed a higher surface degradation of 10 and 35% for CAP pretreated HDPE and PS incubated with microorganisms compared to virgin samples incubated in the same condition. Moreover, chemical transformation indicated a new peak (C–O) in CAP-pretreated PE samples before and after 50 days of biodegradation. The experiments with virgin HDPE and PS demonstrated a positive effect of the pretreatment on the biodegradation process.