Aramid Types and Chemical Structure
topic
Para-aramid: poly(p-phenylene terephthalamide) or PPTA with para-oriented aromatic rings creating rigid-rod structure (Kevlar by DuPont, Twaron by Teijin, Heracron by Kolon). Meta-aramid: poly(m-phenylene isophthalamide) or MPIA with meta-linkages creating flexible chain (Nomex by DuPont, Teijinconex by Teijin). Other aramids: Technora (copolymer of para and 3,4'-diaminodiphenyl ether, higher modulus), Vectran (liquid crystal polymer aromatic polyester with aramid-like properties).
Role
Para vs. meta orientation fundamentally determines properties: para-aramid's rigid-rod structure enables high tenacity/modulus and anisotropy, while meta-aramid's flexibility provides better textile processability and isotropic thermal protection.