Surface modification of textile tire cords by plasma polymerization for improvement of rubber adhesion

Aramid cords and fibers and polyester tire cords were treated by means of plasma polymerization techniques. Coatings of plasma-polymerized pyrrole or acetylene were deposited on the surface of cords and fibers in a custom-built semicontinuous reactor operated on a pulsed DC glow discharge. The deposition conditions of the plasma-polymer coatings were varied within wide limits. The cords were tested for adhesion in rubber in a industrial pull-out test. It was found that the plasma polymer coating can significantly increase pull-out forces. Coatings deposited under low power and high pressure conditions performed better than the coatings prepared under high power and low pressure conditions. The plasma-polymerized coatings were characterized by a range of analytical techniques and the performance results are explained in a tentative model based on the molecular structure of the films. The structure was found to be strongly dependent on the deposition conditions.