Polyaramide

Polyaramide refers to a class of synthetic polymers in which amide linkages (-CONH-) connect aromatic (benzene-ring-containing) monomer units. Commonly called aramids (aromatic polyamides), these materials are typified by high molecular orientation and strong interchain hydrogen bonding, which give them exceptional mechanical strength and thermal stability relative to aliphatic polyamides. Well-known examples include para-aramids such as poly(p-phenylene terephthalamide) (Kevlar) and meta-aramids such as poly(m-phenylene isophthalamide) (Nomex).

Polyaramides are typically produced by step-growth polycondensation of diacid chlorides with diamines or by other condensation routes; some commercial processes use concentrated sulfuric acid or interfacial polymerization to manage solubility during polymerization and spinning. The resulting fibers and films show high tensile strength, high modulus, low elongation at break, good resistance to heat and many chemicals, and limited flammability. Para-aramids are noted for ballistic resistance and high tensile performance, while meta-aramids offer better thermal insulation and flame resistance.

Applications include personal protective equipment, body armor, ropes and cables, composite reinforcements, electrical insulation, and specialty fabrics. Polyaramides are resistant to biodegradation and present recycling challenges; manufacturing and processing can involve hazardous chemicals and fine fibers that may irritate skin or respiratory tissues, so industrial controls and protective measures are standard. Research continues into improved processing, recycling methods, and novel aramid-based composites.