Technologies for Polymeric Cord / Rubber Adhesion in Tire Applications

Introduction Composites made of rubber and reinforcing cords are very common and versatile goods. Well-known examples of these goods are carand bicycle tires, as well as several types of belts and hoses. Clearly, car tires are by far the most important product group within all areas of application. Key element is the reinforcement of the product with cords to prevent large deformations of the rubber and, therefore, loss of the actual product function when high loads are applied in demanding situations. In order to do so, sufficiently high adhesive forces between the composite materials are necessary. A reinforcing effect is only achievable if the load forces can efficiently be transferred from the rubber to the cord. The better the interfacial bond within the composite, the better the product properties will be. In case of lack of adhesion, the cord will not contribute at all to the composite performance, as it will simply slip in the rubber matrix with only minor work required. However, the adhesion phenomenon is affected by several different types of interfacial adhesion, which all have a certain contribution to the overall observed adhesion. Polymeric cords and rubber are not very well adhering as there is a lack of compatibility between them. In general, polymeric cords have a smooth and inert surface as well as a polar character. Therefore, the interactions with non-polar rubber are weak. The compatibility of both materials is important in order to enable a proper wetting of the cord with rubber, which is necessary for adhesion phenomena like surface effects, mechanical interlocking and chemical bonding. None of the cords used for reinforcing applications feature a compatibility with rubber which is sufficient without a treatment: A treatment of the polymeric cord is performed in order to enhance the compatibility and form a physical or chemical bond.