A comparative study of plasma-induced polymerization and plasma-state polymerization of acrylonitrile for modification of cellophane

Research in the area of bio-based composite materials has increased significantly in recent years because materials can be tailored for specific end-use applications. Using lignocellulosic fibers in composite structures allows the production of a whole new range of moldable materials. These materials are good replacements for plastics because they are a renewable resource. However, the strength of the composite material can only be maximized if there is good adhesion between the two components. The incompatibility of the hydrophilic natural fiber with the hydrophobic synthetic matrix does not provide for this adherence across the interface. Two different plasma polymerization techniques were evaluated, plasma-induced polymerization and plasma-state polymerization, to graft polyacrylonitrile to cellophane. Subsequent adhesion improvement between the modified surfaces and polypropylene was measured by t-peel tests.; The plasma-induced polymerization technique requires a two-stage reaction procedure. In the first stage, an argon capacitively-coupled cold plasma generates free radicals on the surface of cellophane cooled to {dollar}-10spcirc{dollar}C. The argon plasma preferentially ablates the amorphous regions of the cellulose and exposes the crystalline regions of this semicrystalline polymer. In the second stage, a gas-phase vinyl monomer floods into the chamber, and the exposed crystalline regions of the cellulose act as templates far growth of a crystalline polyacrylonitrile film. We viewed the crystalline structure of the polyacrylonitrile-grafted cellophane by AFM. The grafted film increases adhesion of cellophane to polypropylene, particularly for longer argon treatment times, most likely due to strengthening of a weak boundary layer as well as chemical adhesion between the grafted polyacrylonitrile film and polypropylene.; The plasma-state polymerization is carried out in one step during which the monomer generates a plasma and deposits primary fragments that recombine on the cellophane surface. The plasma-state polymer was found to form a very strong, heat-resistant film on the surface of a variety of substrates. The polymer appears to have a unique inorganic structure, primarily of carbon and nitrogen. The cyano group of the acrylonitrile is modified in the plasma such that it is not detectable by FTIR. The surface is more hydrophilic than cellophane and the macromolecular structure imaged by AFM replicates the cellophane structure.