Polyurethan

– sous forme de mousse comme isolation de bâtiment, isolation d’électoménager
– ils sont à la base de la fabrication des colles
– combinaison de natation
– préservatifs et gants chirugicaux

Polyurethanes, also known as polycarbamates, are some of the most versatile polymers. First developed in late 1930s,they are used in building insulation, surface coatings, adhesives, and solid plastics. Polyurethanes can be produced in four different forms including elastomers, coatings, flexible foams, and cross-linked foams. Each one has specific uses based on theirs properties.

Polyurethanes are produced by reacting an isocyanate and apolyol of various types (most common isocyanates: TDI (toluenediisocyanate) and MDI (methylenebisdiphenyldiisocyanate); mostcommon polyols: PTMEG (polyetetramethylene ether glycol), PPG (polypropylene ether glycol)).

During this process, the raw materials are pumped from their own storage tank to a common mixing vessel kept under controlled pressure and temperature. Here, additives are incorporated in accordance with a specific recipe.The temperature control inside the reacting vessels is usually made by a recirculating system such as the one illustrated in figure 1.

Figure 1.Schematic of a high-pressure vessel with re-circulation system (a: feed tanks, b: metering pumps, c: mixhead, d: safety valve, e: recirculation throttle, f: low-pressure recirculation valve, g: filter, h: hydraulics for mixhead, M: drive motor)

Polyurethane foam is the most widely used flexible foam plastic. It is produced by adding a blowing agent such as carbon dioxide and methylene chloride. Hard polyurethane plastic can be formed if the polymerization reaction is carried out without blowing agent. In some applications, continuous systems are a good alternative to the batch polyurethane production process, as it can reduce the risk of failed batches.