Recent Developments with Tire Cords and Cord-to-Rubber Bonding

The first pneumatic tire was made in 1888 by J. B. Dunlop with Irish flax as reinforcing material. This fiber was one of the strongest at that time. It was gradually replaced by cotton since Irish flax was expensive. Cotton tire fabrics in the early stages, about 1910, were plain fabrics. As requirements imposed by the severity of tire operating conditions increased, these fabrics were gradually replaced by the present tire cord fabrics, which type of fabric was first devised by J. F. Palmer in 1892. Prior to World War II, cotton was the sole textile used to any large extent in pneumatic tires. However, this cotton tire cord fabric also failed to meet requirements imposed by further increasing severity of tire operations so that tire engineers began to pay attention to man-made fibers. The first rayon tire cord, tenacity about two grams per denier, was produced in 1923. Du Pont started to manufacture high tenacity rayon, Cordura, in 1933, and Courtaulds also started to manufacture high tenacity rayon, Tenasco, in 1936, but by 1940, high tenacity rayons had only a small portion of the total tire cord market. In the late 1940's, use of high tenacity rayon tire cords increased rapidly in the United States and Europe. In Japan, rayon truck tires were first manufactured in 1951. Initially rayon cords were used only for truck tires. The rayon cord tire had improved carcass performance and its life was increased 30 to 60%. This improvement of tire quality was utilized more for truck tires than for passenger car tires. Increased power of automobile vehicles, however, gave birth to troubles in rayon cord (truck) tires. New, tougher materials were required for tire cords especially for heavy duty tires. In 1947, nylon cords (nylon 66) were examined as reinforcing materials for truck tires in the United States, and it was confirmed that nylon truck tires have excellent properties especially under severe operating conditions. In the late 1950's, rayon cords were gradually replaced by nylon cords, especially in the United States. Japanese tire manufactures made extensive efforts to use nylon 6 for tire cords. Nylon 6 was available from domestic suppliers, (nylon 66 was more costly) and nylon 6 tires, when post cure inflation was used, showed no difference from nylon 66 tires in practice. Mass production of nylon tires in Japan started in 1958. In the first five years, 60% of all tire cords had been replaced by nylon cords. In 1967, per cent nylon cord use was up to 90% in Japan. On the other hand, in Europe, rayon cord still has a greater portion of the tire cord market. Goodyear started to produce polyester tires as passenger car tires in 1962. In recent years, production of polyester tires is gradually increasing and their future seems to be promising. Mass production of polyester tires in Japan started in 1967. In both countries, polyester tire producers seemed to desire to penetrate into original equipment tires for passenger cars where rayon cords have been used for many years. Steel cords, which made their appearance in France in 1936, have been used extensively in Europe in radial tires. Glass fiber cords, one of the most promising types for the belt ply of radial tires or belted bias tires, recently appeared in tires in the United States.