Metaaramides

Metaaramids are a class of synthetic polyamides. They are characterized by the meta orientation of the amide linkages in their polymer backbone. This structural arrangement distinguishes them from paraaramids, which have para linkages. The meta arrangement results in polymers with distinct properties, generally offering good thermal stability and mechanical strength, though typically less so than their para counterparts.

The synthesis of metaaramids typically involves the polycondensation of meta-oriented diamines and diacid chlorides. A common example is the reaction between isophthaloyl chloride and m-phenylenediamine. This process yields polymers like poly(m-phenylene isophthalamide), often known by trade names such as Nomex.

Metaaramids are known for their excellent heat resistance and flame retardancy. They do not melt or drip when exposed to flame; instead, they char and self-extinguish. This property makes them valuable in applications requiring protection against high temperatures and fire. They also possess good electrical insulating properties and chemical resistance.

The primary applications for metaaramids are in protective clothing, such as firefighter suits and industrial workwear, where heat and flame protection are critical. They are also used in electrical insulation, honeycomb structures for aerospace, and filtration media. Despite their excellent thermal properties, their tensile strength and modulus are generally lower than those of paraaramids, which are favored for applications demanding extreme strength.