Discovery of Polyurethane
Discovery of Polyurethane
Originally two German chemists named Wurtz, in 1848, and Hentschel, in 1884 made the first Isocyanates, one of the building blocks of Polyurethane. Originally polyurethane was developed for military use by Otto Bayer, in the late 1930's, and was the first to make polyurethane commercially available.
Molecular Structure
Polyurethane is a polymer that consists of repeating units [__ROOCNH__R'__]n. 'R' can represent a different alkyl group, which is obtained by removing a hydrogen atom from a hydrocarbon. Polyurethane's are mostly thermoset plastics meaning the resins cross-link and cannot be melted and remolded. Some polyurethane's are Linear Aliphatic Polyurethane which are thermoplastics. This means the resins are linear and do not cross-link, subsequently they can be reprocessed. Thermoplastic polyurethane is not only linear but has highly crystalline structures. It is because of this that it forms an abrasion resistant material. The diagram above shows the molecular structure of complex polyurethane. Complex polyurethane is considered this because it is made from an isocyanate base. This type of urethane is created through the reaction between an isocyanate and a polyol (Alcohol).
Types
There are many different types of polyurethane’s to include the following: rigid foams, flexible foams, adhesives, sealants, coatings, cast elastomers, and spandex fibers. All polyurethane’s have one thing in common: they contain urethane linkages formed by the chemical reaction between the isocyanate and the polyol. These various forms make polyurethane a very versatile plastic in liquid and solid form.
Applications
Rigid foams or hard foams are used as insulation for buildings, water heaters, refrigeration, and floatation devices. Flexible foams or soft, open-celled polyurethane foams are used as cushion padding under carpets, furniture cushioning, mattresses, and packaging material. Adhesives and sealants are used where high strength, moisture resistance and durability is needed such as construction, automotive and marine applications. Mainly in the automotive field you will see polyurethane as the paint or clear coat on your car, and the glue used to assemble items in your vehicle, and the soft cushions that make up your seat backs and bottoms you sit on. Some foams are also used as the soft cushioning on your dashboard, headliner, steering wheel, and gearshift handles.
Most urethanes used in the automotive field are paints and coatings, as well as, foam rubbers. Thermoplastic elastomers...