Kevlar is an amarid fibre, these are polymers made by weaving liquid 'threads'. This gives them
a regular, crystalline structure which contribute to their incredible strength. Aramid fibres are also incredibly
resistant to heat and very difficult to corrode.
In order to weave a liquid into a solid, you first need a liquid. A liquid can be formed either by melting or,
more realistically, dissolving into solution. The two monomers from which Kevlar is synthesized are Phenylenediamine
(PPD) and Terephthaloyl chlorine when they react hydrochloric acid is formed as a by-product; this is illustrated in
the diagram below. When they are produced the molecules are aligned amorphously so the structure lacks strength however
when they are spun and woven together they form a crystalline structure which is much stronger.
However, PPD and Terephthaloyl chlorine are very insoluble so highly concentrated sulphuric acid is required to
keep them in solution. This makes the process very expensive.
