Polyurethane forms a major part of our everyday life. It started its life as a rigid foam for use in airplane wings way back in the World War II era. Today it has evolved into various forms and is available as resins, rubbers, plastics, adhesives, foams and paints.
Polyurethanes find numerous applications across almost all fields – from furniture, bedding and carpets to footwear and from refrigerators and freezers to automotives. It is also widely used in mold making and casting works as it is durable, resilient and flexible. It works as a binder for fiberglass and as a protective coat of paint for furniture and hardwood floors to get a sleek finish. It has good heat resistance too.
Polyurethane comes in a range of textures and hardness levels, from soft and flexible to hard and rigid. The pliable ones find common usage in the art field. Polyurethane rubbers are often used for making molds of inanimate objects that will be exposed to abrasive actions, like concrete casting and sculpture reproductions for example. They pick up minute details and can be used for making detailed and ridged casts, like in architectural restoration works.
There are different varieties of polyurethane resins that are of high quality and lend themselves well for making regular casts. But plaster casting is still preferred for making life casts as it sets quickly and is easier to work with.
How is polyurethane made and used?
Polyurethane is a polymer compound that involves a combination of a polyol and an isocyanate. The former is an alcohol-based hydroxyl compound that reacts with the latter to create polyurethane. The proportion in which both the substances are combined will dictate the properties of the resulting synthetic polyurethane – whether it will be rubber or foam or resin and so on.
Polyurethanes generally come in a liquid form, but are also available as a spray or a foam. The liquid polyurethane resin or rubber has a specified mix ratio when used for mold making or casting projects. It is easy to mix and can be poured with no trouble.
But polyurethane is quite prone to air bubbles and should be used carefully. Especially when working with polyurethane resins for making a cast, using a pressure pot or vacuum chamber is essential for eliminating the bubbles.
Polyurethane resin has a very low odor as compared to the carcinogenic producing smells of polyester resins. But bear in mind that polyurethane is highly impressionable and therefore, even the smallest crack will be clearly visible in the final piece. You also have to wear protective clothing when using polyurethane.
While some may say that polyurethane proves expensive, it is much cheaper than silicone rubber and yet lends itself well for multiple purposes.
To sum up, polyurethane is an extremely versatile product that is enjoying increasing popularity both in the art world and daily life. And the applications of polyurethanes will continue to grow as people find new uses for it!