Plasma modification of polymeric single end cords as an alternative to RFL treatment

Adhesion between reinforcing fibers and the matrix is crucial for a good performance of a wide variety of elastomeric products. RFL treatment is most commonly used to achieve rubber-fiber adhesion for decades; however, there are health concerns related to this method. Therefore, alternative methods to partly or completely replace the RFL treatment are currently developed. A new approach for adhesion enhancement is plasma treatment of the fiber/cord. This process allows to physically and chemically modify the cord surface and thus to increase compatibility with and reactivity towards the elastomeric matrix. In this study, an atmospheric plasma jet was used to coat polymeric cord surfaces with an adhesive layer in a pilot-scale continuously operating line. The precursors used for the chemical surface modification of the cords carried sulfuric moieties and/or unsaturated carbon-carbon bonds, to result in functional groups reactive towards the polymer after the plasma polymerization and deposition on the cord surface. The crucial components of the equipment, process parameters, and pre- as well as post-treatments were elaborated. The results in terms of cord properties as well as adhesion strength of different types of cords to an elastomeric compound will be discussed. Furthermore, an overview of the advantages and disadvantages of the resulting cord/rubber interface in comparison to the industrial standard will be given