Improving the adhesion of glass/polypropylene (glass-PP) and high-density polyethylene (HDPE) surfaces by open air plasma treatment

The objective of this study was to investigate the bonding between glass reinforced polypropylene (glass-PP) and high-density polyethylene (HDPE) surfaces. As glass-PP and HDPE surfaces possess low surface energy inherently, atmospheric plasma treatment enhances the adhesion characteristics between the surfaces by increasing their surface energies. Both the materials were subjected to atmospheric/air plasma by varying parameters such as plasma intensity and number of treatments. Optimal plasma treatment conditions were determined based on the bond strength of the materials. Various characterization techniques such as FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), DSC (differential scanning calorimetry) and surface energy determination via wettability inks, were employed to understand the surface modification following plasma treatment. Furthermore, the effect of plasma treatment on glass-PP surface versus a neat polypropylene (neat PP) surface was characterized to understand and establish a baseline. Improvement in bond strength of glass-PP-HDPE panels was observed, GΙc (Mode 1 interlaminar fracture toughness) value of glass-PP- HDPE panels increased from 0.1 N/mm to 5.5 N/mm (after plasma treatment) whereas, the GΙc value of neat PP- HDPE panels increased from 0.4 N/mm to 2.8 N/mm (after plasma treatment). Enhancement in the surface energy of glass-PP and HDPE surfaces was observed, surface energy of glass-PP increased from 28 mN/m to 58 mN/m and the surface energy of HDPE surface increased from 28 mN/m to 72 mN/m.