Aramid tire cord

Introduced in 1972, the whoUy aromatic polyamide, poly i ra-phenylene teraphthalamide), termed aramid, was the subject of extensive evaluation as a tire cord in all types of tires (8,14). As of the late 1990s, however, only specialized appHcations have emerged for aramid tire cord that draw on their high strength-to-weight ratio to produce tires with lower weight (16). 

Polymers are real and all around us. We can look at giant molecules on a micro or atomic level or on a macroscopic level. The PET bottles we have may be composed of long chains of poly(ethylene terephthate) (PET) chains. The aramid tire cord is composed of aromatic polyamide chains. Our hair is made up of complex bundles of fibrous proteins, again polyamides. The polymers you study are related to the real world in which we live. We experience these large molecules at the macroscopic level everyday of our lives and this macroscopic behavior is a direct consequence of the atomic-level structure and behavior. Make pictures in your mind that allow you to relate to the atomic and macroscopic worlds. 

Aramid tire cords have been treated by argon plasma etching and plasma polymerization of acetylene. The combination of argon plasma etching and acetylene plasma polymerization results in a greatly improved pull-out force of 91 N in comparison to 34 N with the untreated aramid tire cord. Thus, the plasma treatment improves the adhesion to rubber compounds. " ... 

H. M. Kang, T. H. Yoon, and W. J. Van Ooij. Enhanced adhesion of aramid tire cords via argon plasma etching and acetylene plasma polymerization. J. 

Standard Test Methods for Tire Yarns, Cords, and Woven Fabrics. ASTM standard D885M-94 includes test methods for characterizing tire cord twist, break strength, elongation at break, modulus, tenacity, work-to-break, toughness, stiffness, growth, and dip pickup for industrial filament yams made from organic base fibers, cords twisted from such yams, and fabrics woven from these cords that are produced specifically for use in the manufacture of pneumatic tires. These test methods apply to nylon, polyester, rayon, and aramid yams, tire cords, and woven fabrics. 

Aramids are also widely used as the fibers that are part of space-age composites and in the manufacture of tire cord and tread. (See Figure 7.) see ALSO Carothers, Wallace AIaterials Science Polymers, Synthetic. 

Aramid polymers are much more expensive than the aliphatic polyamides. The use of aramid polymers is limited to those applications that justify the high cost. The present U.S. market is about 20 million pounds per year. The applications are those where one needs very high flame resistance (clothing for firefighters and welders, welder s protective shield, upholstery and drapes), heat resistance (ironing board covers, insulation film for electrical motors and transformers, aerospace and military), dimensional stability (fire hose, V- and conveyor belts), or strength and modulus (circuit boards, bulletproof vests, fiber optic and power lines, ship mooring ropes, automobile tire cord, puncture-resistant bicycle tires). 

Tire cord n. A textile material used to impart the flex resistance necessary for tire reinforcement. Tire yarns of polyester, rayon, nylon, aramid, glass, or steel are twisted to 5-12 turns/in. Two or more of these twisted yarns are twisted together in the opposite direction to obtain a cabled tire cord. The twist level required depends on the material, the yarn linear density, and the particular application of the cord. Normally, tire cords are twisted to about the same degree in the S and Z directions, which mean that the net effect is almost zero twist in the finished cord. 

Since belted radial tires were introduced in 1948 by Michelin, steel as well as polyester and aramid have been used to make the tire cord for the radial belt. Steel has historically also been used to make the bead wire in tire construction. In addition, steel has been used to manufacture the cable that is used in making rubber mining conveyor belts. Lastly, in the automotive industry, many times rubber parts are made that are composites of rubber and steel. Examples of these parts are seen with motor mounts and bushings. 

High modulus fibers from lyotropic aromatic polyamides, poly(p-phenylene terephthalamide) (PPTA), first commercialized under the Kevlar trademark by DuPont [614], find major applications as fibers in tire cords and heat and chemical resistant fabrics. Other fibers in this class of materials are used in important applications such as firefighter and military uniforms, gloves, and in many other hazardous applications. The aromatic polyamides, or aramids, are produced by a dry jet-wet spinning process where the nematic structure in solution is responsible for the high modulus fiber performance [615-619]. Another class of lyotropic fibers, also produced by dry jet-wet spinning, are the rigid-rod... 

The tire cord fabric is pulled of woven fabric and passes through an impregnating bath with a resorcinol-formaldehyde-latex solution that improves the adhesiveness on the rubber. This impregnating is sufficient for viscose and polyamide, but polyester and aramid have to be pretreated additionally with bonding agents based on epoxy resin. 

---