These engineering polymers are thermoplastics that repeat amide groups on the molecular chains. They have good chemical and temperature resistance; provide strength, toughness, and stiffness; and resist wear and abrasion.
The largest nylon market today, with more than 40% of the total demand, is in automobiles and transportation equipment. Recently, the use of plastics in underhood parts increased dramatically, and nylon is by far the most widely used plastic for this purpose, thanks to its temperature and chemical resistance.
Automobile intake manifolds, formerly made of metal, have been replaced rapidly by glass-fiber reinforced PA 6. The deciding factors in the selection of PA 6 for such applications are its excellent mechanical properties, moldability, and ease of secondary processing such as vibration welding, an important process for the production of intake manifolds.
Along with underhood parts, one of the most important application areas for PA is in fuel systems. The use of PA in fuel pipes is expected to expand soon. Many multilayer fuel pipes use PA 12 as a base material, adding EVOH or a fluorocarbon resin as a barrier. In response to growing public awareness of environmental issues, vehicle producers are making multilayer fuel pipe systems that avoid halogen-containing polymers in favor of nylon-clay hybrid (NCH) materials, which provide barrier against vapor emission.
In recent years, nanotechnology has attracted attention in a number of fields. Materials technology is no exception, as the control of material structure at the nano level is sure to lead to the development of new properties. In fact, nylon was the first material to which nanotechnology was applied.
Using basic technology from Toyota Central R&D Labs. Inc., UBE Industries partnered with Toyota Motor Corp. to develop and commercialize NCH. This nanocomposite technology enables stratified silicate to be distributed at the molecular level in ways that never before had been feasible. By enabling inorganic filler to be distributed on the order of a few microns, additives thus can be supplied in extremely small quantities to affect dramatic improvements in rigidity, heat-resistance, and barrier property against gases and automobile fuel.
NCH found its first commercial application in engine block timing-belt covers for Toyota. In the future, due to its superb blocking properties, NCH is expected to be adopted in barrier film applications. As automobile manufacturers face increasingly stringent regulations on volatile components in fuel, the barrier properties of NCH are expected to assume a valuable role as a material for fuel pipes.
Another recent technological development is the creation of new thermoplastic elastomer (TPE) materials based on nylon grades. TPEs are flexible and highly amenable to molding. These thermoplastic resins can serve as substitutes for rubber in many applications. Polyamide elastomers combine the friction and chemical resistance of nylon with the flexibility of rubber. These materials offer good flexural fatigue resistance and hydrolysis resistance. A variety of applications are expected including, for example, sporting goods where resilience and durability are demanded, or in industrial tubing to provide both flexibility and chemical resistance.
Nylon enjoys wide use because of its excellent balance of properties. Automobile manufacturers are concentrating on meeting challenging environmental problems, such as improvement of fuel efficiency by weight reduction and, correspondingly, reduction of fuel penetration. The further adoption of nylon for new vehicle parts is expected to grow. Ongoing development will likely surround nanocomposites, offering many new opportunities for processors around the world.