Unlike any other product, polyurethane is a unique material that offers the elasticity of rubber, combined with the durability of metal. Polyurethane is a polymer composed of organic units joined by a carbamate link. With a broad range of hardness, urethane can range from as soft as an eraser to as hard as a bowling ball.
First developed in 1937 by Otto Bayer and his coworkers at IG Farben in Leverkusen Germany, this new polymer had some advantages over existing materials of the time. Bayer's early work focused on the production of fibers, and flexible foams, which were applied as aircraft coating during World War II. Following this early development, soon many other major chemical companies began to work to develop their own versions of this revolutionary material. In 1956, DuPont introduced polyether polyols, this new material was cheaper, easier to handle and more water resistant than previously used polyester polyols. By 1960, over 45,000 metric tons of polyurethane foam was being produced each year, the superior qualities of this product allowed it to be used as high performance insulation, and by 1967 modified polyurethane based foams were introduced, offering even better thermal stability and flammability resistance, making it ideal for the automobile industry. Speaking of the automobile industry, in 1969 Bayer would use his polyurethane to create an all plastic car, yet not just a car came out of his idea. Bayer also developed reacting injection molding. This new manufacturing process would become almost as popular as the material he developed. And his plastic car idea would later be used as the model for the Pontiac Fiero in 1983.
The excellent qualities of polyurethane make it the superior product it is known for. First off, polyurethane is very abrasion resistant, and will often outwear other materials by a factor of 50 to 1, when severe abrasion is a factor. Along with that, the material is also very tear resistant, with a tear strength ranging between 100-500 lbs/linear inch. On top of its abrasion resistance and tear strength, polyurethane also has a high flex life and is also great for electrical insulation.
Today, polyurethane is used in many different applications including high-resilience foam seating, microcellular foam seals and gaskets, durable elastomeric wheels and tires, for things such as roller coasters, escalators and skateboards. Polyurethane is also used in automotive suspension bushings, electrical potting compounds, surface coatings and sealants, high performance adhesive as well as synthetic fibers used in clothing, such as spandex.
Here at Stern Rubber, we put urethane to good use through two different kinds of molding. The most commonly used is thermoset urethane. This process is like any other type of rubber molding, in which it goes through a curing process with a great deal of pressure, and high temperature. This form of material is typically chosen for situations where the rubber needs to be stronger than average. This type of material is used to produce some very specialized parts, including high strength tie rod boots for the military, specialty seals for light fixtures, and high strength motor mounts. Along with thermoset urethane, we also use another form called cast urethane. This material is a two part liquid that is mixed together and then either poured or injected into a tool. After the material is inserted into the tool, we put the molds into the oven overnight and unload the next day. The particular types of cast urethane that we use, cure very slowly, and results in producing only one part per day, so is only used for very low volume products. Here at Stern, this is primarily used to produce seals for leak test machines that test aluminum casting.
Now, although this type of material is very effective, we also use many other types of rubber to produce our products. So, remember, Stern Rubber is always available to help with your material selection. Check out the engineering resources section for more information on materials, which includes a material selection guide.