Hydrogen and oxygen plasma treatment of two cellulose materials, a filter paper of pure cellulose and a greaseproof paper with a fairly high surface content of wood resin, has been studied with ESCA as well as by contact angle or water absorption. The hydrogen plasma treatment reduces the hydroxyl groups on the cellulose and creates low molecular weight materials. Due to the lower polarity, water absorption is reduced. The oxygen plasma treatment of the pure cellulose both oxidizes and reduces the surface. The resin-rich paper, which has a hydrophobic nature, shows improved water wettability after both hydrogen and oxygen plasma treatments.

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The adhesion between plasma-modified polyethylene (PE) and Merent polar polymers, as well as aluminium and steel, has been studied. The PE was modified by either oxygen plasma treatment or plasma polymerization of acrylic acid. The results show the importance of introducing polar groups on the surface of the non-polar PE in order to improve the adhesion to polar polymers as well as metals. Laminates made of plasma-modi6ed PE and polyamide 6 (PA-6) or poly(ethy1ene vinyl alcohol) (EVAL-G) showed failure in P A 4 or EVAGG when delaminated. Poly(ethy1ene terephthalate) (PET), which is not as polar as P A 4 or EVAIPG, showed an adhesive failure when the PE was treated with either of the plasma methods. However, when both the PET and the PE were modified, the failure occurred in the PET upon delamination. Oxygen plasma treatment of PE resulted io an increased adhesion when laminated with cellophane, with no observed material failure. The laminates composed of plasma-mdied PE and aluminium or steel showed cohesive failure in the PE.

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Filter paper and greaseproof paper have been exposed to hydrogen or oxygen plasma. The paper surface c o m p ition was determined by ESCA measurements. The unmodified and modified papers then were laminated with polyethylene and the adhesive strength was measured. The hydrogen plasma treatment reduces the cellulose surface and forms low-molecular-weight degradation products. It is shown that the reduction of the ceUulose surface has no influence on the adhesion, but the degradation products strongly decrease the adhesion. Oxygen plasma treatment increases adhesion, probably by removing low-molecular-weight wood resin from the surface and by forming covalent bonds across the interface.