Surface Free Energy Modification of Crude Rubber Using Oxygen Plasma and UV Laser Treatment

A study has been made of the surface properties of nitrile-butadiene rubber and ethylene-propylene-diene monomer crude rubber, basic raw materials for offset lithographic printing blankets manufacturing. Increased surface free energy of the crude rubber was achieved by treatment with the low-pressure oxygen plasma. After plasma activation, samples were treated using a UV laser to deactivate the surface layer. The surface free energy was calculated on the basis of contact angles with different liquids. Plasma-treated samples had higher surface free energy, especially the polar component, and the effect was larger for nitrile-butadiene rubber samples. This surface free energy decreased after exposure to UV laser light. FTIR-ATR spectroscopy was used to detect possible changes in chemical structure of the surface, but no differences were obtained. Changes of surface free energy were thus most likely a consequence of changes in the surface structure.