The Uses of Polyurethane in Cars
Polyurethane is a term used for any polymer; that is a long chain of multiple bonded molecules; comprising a chain of organic units which are joined by a urethane (a carbamate) link. They are formed through a process known as step growth polymerisation, which refers to the process of becoming a large chain of molecules one step at a time: first a double bonded compound known as a dimer (hence the prefix di), then a trimer etc. To produce polyurethane through step growth polymerisation, one must react a monomer (a singular molecule, which in this case must have two or more isocyanate functional groups) with another monomer (with at least two OH/alcohol groups) in the presence of a catalyst.
The industrial applications of polyurethane polymers include high resilience, flexible foam seating such as can be found in many forms of transport; foam insulation panels; wheels and tyres; suspension bushings for automobiles; surface coatings and sealants; and hard plastic parts, among many other things. As we can see, polyurethane is extremely useful, particularly in the automotive industry.
Polyurethanes were developed in the early to mid twentieth century by German industrial chemist Otto Bayer and his co-workers. Bayer realised that by using the step growth polymerisation method, not only could special applications be conceived, but the new product could circumvent existing copyright laws. Work initially focused on the production of flexible foams and fibres, with polyurethanes becoming commercially available in the 1950s.
Polyurethane applications continued to develop. In 1969 initial inventor Bayer exhibited a car made entirely of plastic. Large portions of the car were created using a then new process known as RIM: Reaction Injection Moulding. The way RIM works is by holding back reactive liquid components under high pressure until they can be rapidly injected into the mould cavity, where the process is almost instantaneous. RIM can be used to create large parts, particularly used in car production today, such as doors and body panels. The first plastic bodied production car was produced almost fifteen years later in the United States; the Pontiac Fiero, which was introduced in 1983.
Since the introduction of polyurethane as a component in cars, market share has greatly increased due to increasing energy prices and the pressures to remove PVC (polyvinyl chloride) from automotive applications. Today, polyols such as polyurethane are gaining public attention again, as the potential increases for creating them from vegetable oils and other organic compounds, with the Ford Motor Company perhaps being among the most vocal supporters of this.
Polyurethane is regularly used in the automotive industry, along with moulding techniques such as injection moulding. Today, many cars are made primarily of plastics for economy reasons.