Polyurethane (PMC-790)

This is an industrial urethane rubber used for a number of industrial applications, including making concrete stamping pads and moulds for casting decorative concrete sound-barriers for motorways. Regardless of the end-product or even type of polyurethane you are using, the way in which you use polyurethane resins is always the same: the raw materials come in two parts, a liquid isocyanate (a very reactive chemical derived from petroleum) and a polyol (a long-chain alcohol), which are mixed to a specified ratio to create a reacting liquid, which is then poured into a mould or onto a surface and left until it cures to form a solid object. This relatively low-tech process makes it a useful material for tinkering and making prototypes.