Chemical Properties
Poly(p-phenylene terephthalamide) is an extraordinarily strong material.
The specific tensile strength (tensile strength/density) of the fibre is higher
than that of any other continuous fibre commercially available. The polymer
does not melt but begins to carbonize at about 425°C. The material retains its
mechanical properties over a wide temperature range for prolonged periods.
There is little change up to about 180°C and even at 250°C approximately
half of the initial tensile strength is retained after 100 hours. The material is
attacked by mineral acids and alkalis and is also sensitive to ultraviolet light.
Uses
Poly(p-phenylene terephthalamide) fibres currently have three major applications,
namely as reinforcement in radial tyres and mechanical rubber
goods, in ballistic protective fabrics and ropes, and as reinforcement in
polymer (particularly epoxy) composites for aircraft and aerospace components.
Preparation
Poly(p-phenylene terephthalamide) is produced by reaction of terephthaloyl
chloride and p-phenylenediamine:
Full details of the manufacture of the polymer have not been disclosed. The
reaction is reported to be carried out in a solvent mixture of hexamethylphosphoramide
and N -methylpyrrolidone. The polymer is supplied in fibre form.
Poly(p-phenylene terephthalamide) is an extraordinarily strong material.
