A polyamide (PA) is a macromolecule with repeating units linked by amide bonds. It is better known by its trade name Nylon®, introduced by Dupont. It was the first purely synthetic fiber.
The aromatic polyamides (aramids) have higher strength, better solvent, flame and heat resistance and greater dimensional stability than aliphatic amides (nylon) but are more expensive and difficult to produce. The two most important aromatic amides are poly(p-phenylene terphthalamide), also known as Kevlar® and poly(m-phenylene isophthalamide). The aliphatic polyamides are the most important class of engineering thermoplastics.
The fully aromatic structure and the strong hydrogen bonds between the aramid chains result in high melting points, ultra high tensile strength at low weight, and excellent flame and heat resistance as well as good dimensional stability and solvent resistance at room and elevated temperature. The two most important aliphatic polyamides are poly (hexamethylene adipamide) (Nylon 6,6) and polycaprolactam (Nylon 6). Both have excellent mechanical properties including high tensile strength, high flexibility, good resilience, low creep and high impact strength (toughness
PA is used for mechanical parts such as machine screws, gears and other low- to medium-stress components previously cast in metal. It can be used as the matrix material in composite materials, with reinforcing fibers like glass or carbon fiber; such a composite has a higher density than pure nylon. Such thermoplastic composites (25% glass fiber) are frequently used in car components next to the engine, such as intake manifolds, where the good heat resistance of such materials makes them feasible competitors to metals.
- High durability and tensile strength
- High wear resistance
- High melting points
- Good chemical resistance
- High mechanical damping characteristics
- Low creep
- Textiles, automotive applications, carpets and sportswear
- Transportation manufacturing industry
- Composite materials
- Safety airbags