Influence of the concentration of trimethylol propane triacrylate on the electron beam-induced surface modification of EPDM rubber

EPDM rubber has been surface- and bulk-modified with varying concentrations of trimethylol propane triacrylate (TMPTA) in the presence of an electron beam at a constant irradiation dose of 100 kGy. The surface properties of the modified rubber have been characterized by contact angle measurements, surface energy and thermodynamic work of adhesion, infrared spectroscopy (IR), and X-ray photoelectron spectroscopy. The surface energy of EPDM increased from 44.8 to 53.8 mJ/m2 on modification with 10% TMPTA, due to the increased contribution of γs (-) and γs AB. With increasing TMPTA concentration, γs and γs AB showed an optimum value at 10% concentration. The IR studies indicated increased peak absorbances at 1730, 1260, 1120 and 1019 cm-1 and hence increased -C(=O)- and C-O-C concentrations. These results are further supported by XPS data.