Improvement of the Coating Properties of Polypropylene by Ozone Treatment

In order to improve the coating properties of polypropylene (PP) surfaces, three types of polypropylene--homopolymer (JHH-G), block copolymer with ethylene (BJH-G), and random copolymer with ethylene (GFL-G)--were ozonized at ozone concentrations of 1.38, 0.64, 0.41mol%. The ozonized samples were ultrasonically washed with chloroform and coated with various paints. Adhesion strengths of the coatings were evaluated by the peeling test method. The following results were obtained: 1) The adhesion of paints onto polypropylenes was greatly improved. 2) The increase in adhesion strength was dependent on the substrates in the order of BJH-G>GFL-G>JHH-G. 3) Optimum ozonization conditions were found to exist for each of the polypropylenes. 4) Reactive paints such as epoxy and acryl urethane resins afford better adhesion strength than conventional ones (acryl or PVC resin).