Effect of plasma treatment on the degree of AAm grafting for high-density polyethylene

The aim of this article was to determine a suitable method and optimal conditions for grafting of acrylamide (AAm) monomer onto the surface of high-density polyethylene (HDPE). We studied argon plasma treatment of HDPE (PHDPE) and AAm graft copolymerization (AAm-g–PHDPE) using thermal induction with or without adding an initiator, benzoyl peroxide (BPO) [AAm-g (BPO)–PHDPE]. The 1,1-diphenyl-2-picrvlhydrazyl (DPPH) method was adopted to estimate the concentration of peroxide, and consequently the appropriate plasma treatment conditions were determined according to its optimal concentration. ATR-FTIR spectroscopy and ESCA analysis were used to evaluate the degree of grafting copolymerization. The maximum degree of grafting was 0.55 and 2.41 as evaluated by total-reflectance Fourier-transform IR (ATR-FTIR) spectroscopy and electron spectroscopy for chemical analysis (ESCA), respectively. The degree of grafting shows similar trends by ATR-FTIR and ESCA analysis and the optimal grafting time is 4 h. The result also shows that the degree of grafting is also affected by the plasma treatment time. DPPH measurements showed that the maximum peroxide introduced onto HDPE sheets by plasma treatment at 40 W for 3 min and air exposure for 1 h is 5.2×10−8 mol cm−2. In this investigation, the best graft copolymerization conditions for HDPE are plasma treatment at 40 W for 3 min and thermally induced grafting for 4 h with an initiator (2×10−3 M).