CO 2-Pulsed laser induced surface grafting of acrylamide onto ethylene-propylene-rubber (EPR)—I

Abstract

For improved bio and water compatibility laser induced graft copolymerization of acrylamide (AAm) onto the surface of EPR vulcanizates has been attempted using a line-tunable pulsed CO 2 laser. This operates at wavelengths of 9.1–10.6 μm at which EPR is neither ablated nor photodegraded. Grafting has been carried out in 20% aqueous solution of acrylamide. The effectiveness of different photosensitizing systems has been evaluated. The degree of both laser grafting and polymerization of this monomer has been studied. Surface morphology was also investigated by SEM and staining technique. Attenuated Total Reflectance infrared (ATR-IR) and energy dispersive X-ray analysis (EDXA) were performed on the modified samples. Water compatibility (evaluated by measuring water drop contact angle) increase for the modified samples and is found to depend upon surface morphology. Acrylamide is grafted onto EPR by CO 2-laser providing it is irradiated by pulses having wavelengths where acrylamide has strong absorption. Grafting was enhanced by adding sensitizers which have strong absorption band within the working wavelength. The peculiarity of the laser pulsed-induced surface grafting of acrylamide is the formation of fractals. The size and shape of fractals was found to depend upon the exciting wavelength and therefore the degree of excitation of either monomers or photosensitizer (as well as the repetition rate). We believe that infrared laser induced polymerization and grafting of acrylamide with EPR occurs by vibrational excitation of acrylamide or the added photosensitizer through multiphoton absorption mechanism.