Polyurethane (yellow)

These cast blocks of polyurethane resin are reminiscent of boiled sweets in texture and colour. This yellow transparent polyurethane is produced in liquid form so it can be poured into moulds. Being highly impressionable, even the finest detail in the mould will show in the finished product. These thick, viscous and sticky liquids were named 'synthetic resins' because they change viscosity in a way that is reminiscent of naturally-occurring plant resins, like mastic, that set over time. 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. The mechanical properties of polyurethane resins are not affected greatly by UV light, but they can discolour over time when exposed to sunlight. This material contains chemical stabilizers that make it UV-resistant and non-brittle. Polyurethane resins are used to produce a huge variety of things from inks and adhesives to plastics.