Adhesion of PE modified by capacitively coupled radio frequency plasma-induced graft polymerization of glycidyl methacrylate

Abstract

A graft polymerization of glycidyl methacrylate (GMA) on the pretreated polyethylene (PE) sheet samples by oxygen capacitively coupled radio frequency (RF) plasma was carried out to improve the adhesive properties of PE. The PE samples were treated with a RF power of 200 W for a treatment time of 40 s and then exposed to an oxygen atmosphere for a saturation time of 10 min. The grafting of the plasma pretreated PE performed in an aqueous GMA solution with the monomer concentration from 20 vol.% to 100 vol.% at a temperature from 20°C to 90°C for a reaction period up to 50 h. The optimum wettability of the graft polymerized PE surface with the concentration of 40 vol.% at the temperature of 70°C and for the time of 24 h was obtained as the static contact angle decreased from 104.2° for the original PE to 67.6° for the graft polymerized. After the graft polymerization, a strong absorption peak of C-O bonding was shown at 1050 cm−1 in Fourier transform infrared spectrum, indicating an introduction of epoxy groups on the graft polymerized surface. Correspondingly, the surface roughness (Ra) increased from 0.137 μm for the original PE to 1.660 μm for the graft polymerized. The maximal lap adhesive strength of the graft polymerized PE samples lapped using a mixture of epoxy resin and curing agent was achieved to about 160 N·cm−2. The fractured surfaces by tearing of the PE sheet matrix were observed on the tensioned PE samples due to the higher adhesive strength than that of the PE matrix.