Experimental investigation into the effect of DC glow discharge pretreatment of HDPE on tensile lap shear strength

The present investigation aims to optimise the process parameters of DC glow discharge treatment through air in terms of discharge power and time of exposure for attaining best adhesive joint of high-density polyethylene (HDPE) to mild steel. The as- received and DC glow discharge exposed HDPE surfaces have been characterised by energy dispersive spectra (EDS). It is observed that with increasing power level up to 13 W, tensile lap shear strength of adhesive (Araldite AY 105) joint of HDPE to mild steel increases and then decreases. At 13 W power level, joint strength increases up to 120 s of exposure and then decreases. At the optimised condition for the surface modification, the effect of two different adhesives Araldite AY 105 and Araldite 2011 on the strength of polymer to mild steel, polymer to polymer and mild steel to mild steel joints have been examined. It is observed that tensile lap shear strength of HDPE–HDPE joint and HDPE–mild steel joint does not change with the change of adhesive and this could be possible as initiation of fracture takes place from subsurface layer of the polymer. This is confirmed by studies under optical microscopy and EDS, which shows when the polymer has been modified by exposure under glow discharge the failure is observed to initiate from subsurface layer of the HDPE, then within the adhesive cohesively and thereafter in the mild steel to adhesive interface.