Polyaramid fibre is an infusible, aromatic polymer that is manufactured only as a fibre (by solution spinning) and is characterized by high thermal stability, temperature, and flame resistance. The tensile properties of polyaramid fibre are greater than those of regular textile fibres. This is due to a high degree of molecular orientation that results from its stiff linear molecules and their tendency for forming liquid crystals in the spinning solution. Polyaramid fibre is extensively used in composites which are lighter than those based on and carbon fibre and are electrically insulating. The mechanical properties of the polyaramid fibre are usually inferior; particularly if they have a high specific tensile strength closer to that of carbon fibre composites, but relatively low strength in compression. In addition to composites, applications of polyaramid fibre include body armour and protective clothing, elastomer reinforcement, friction products, cords and ropes and as high strength high modulus fabric for example high performance sailcloth.
Vinyl ester resins are similar in their molecular structure to polyesters, but the vinyl ester resins are tougher and more resilient than polyesters. Vinyl esters exhibit better resistance to water and many other chemicals than their polyester counterparts, and are frequently found in applications such as pipelines and chemical storage tanks.
The resin matrix spreads the load applied to the composite between each of the individual fibres and also protects the fibres from damage caused by abrasion and impact. High strengths and stiffness, ease of moulding complex shapes, high environmental resistance all coupled with low densities, make the resultant composite superior to metals for many applications.