Surface Modification of Polymeric Materials By Photocured Coatings or Photografting

摘要

The surface properties of UV-cured coatings have been modified by copolymerizable fluoro and silicone acrylic monomers. These additives have rather a positive effect on the cure kinetics of the various polyurethane acrylate formulations tested. They were shown to increase considerably the hydrophobic character of the surface in contact with air, at monomer concentrations as low as 1 wt %. The silicone acrylate monomers proved to be more efficient than the fluoro acrylate monomer tested, while they increase at the same time the slipperiness of the UV-cured coatings. The results make it possible to design the formulation of UV-curable urethane acrylates used in a variety of industrial applications, in particular to control surface properties, such as the hydrophobicity, slipperiness and chemical resistance. Polypropylene and polyethylene foils have been superficially modified by photoinitiated grafting of acrylic acid and hydroxypropyl acrylate. With these polar monomers, the hydrophilicity and wettability of PP and PE has been drastically increased within seconds, upon UV exposure in the presence of a hydrogen abstraction-type photoinitiator. The grafting reaction was performed by a continuous process, in the presence of air, by lamination of the liquid monomer, or an aqueous solution of it, between two polypropylene films. Grafting has been characterized by IR spectroscopy analysis and surface energy measurements, after solvent development of the irradiated sample. By this simple process, polyolefin foils can be made suitable for printing. The surface modification processes reported in this work are based on a well-established UV-technology. They show the distinct features of photochemical initiation, namely an ultrafast reaction of a solvent-free resin occurring in well-defined areas at ambient temperature. These processes should be of particular interest in the modification of many polymer surface properties such as wettability, adhesion, biocompatibility, friction and wear. This process could open the field to some new applications requiring the use of smart polymers with well-designed properties.