Have you ever wondered just exactly what those magical plastic like substances that can be very soft or very hard, yet still the same substance called polyurethans actually were?.
Polyurethanes are very versatile plastics that were originally developed for military use by Otto Bayer in the late 1930's. They are so versatile that they can be made into a compound as soft as bubble-gum, or they can also be formed into compounds that are as hard as a soft metal. This is why they are so common in our everyday life's. Today a wide variety of polyurethanes are used for many different applications, such as flexible polyurethanes used to make sofas, cushions, carpet backs, and car seats. Rigid foams are used for insulation in freezers, refrigerators, and roofs. Many shoe companies also use tough elastomeric polyurethanes for shoe soles. The auto industry also uses polyurethanes for a variety of reasons, including dashboards, bumper covers, moldings and fenders. These are just a few of the many use for polyurethanes.
The base material used to form polyurethane compounds is actually a by-product of the oil refining process. The end product, polyurethane, is made with two basic ingredients: a Isocyanate and Polyol. This is shown in the reaction below:.
Isocyanate + Polyol = Polyurethane.
Reacting an isocyanate and a polyol of various types produces polyurethanes. Almost all commercial grade polyurethanes available are based on two different isocyanates; TDI (toluenediisocyanate) and MDI (methylenebisdiphenyl diisocyanate). Both of these isocyanates give different properties to the polyurethane and have varying types of processing systems. The polyol, which is the other reactant in the polyurethane, is available in three different types: PTMEG (polyetetramethylene ether glycol), PPG (polypropylene ether glycol) and polyester. There are other isocyanates and polyols that can be used in the manufacturing of polyurethanes, but these are the most common.
