POLYURETHANE
History
Polyurethanes were developed in 1937 by the chemist O. Bayer in Leverkusen. They have been produced on a technical scale since 1940 and are now used in an extraordinary variety of applications.
Besides casting resins and elastic PUR moulding compounds, it is mainly PU foams (PUR) that we encounter everywhere. For this reason, it is not possible to show a property profile for polyurethanes as for other material groups (e.g. epoxy and polyester resins). Differentiation is rather made according to application areas.
General properties of moulded parts
- Low density (freely foamed 37 kg/m3)
- Closed cell, therefore no water absorption
- Good adhesion to all materials
- Good compressive strength
Processing
The following is essential when processing PU foam
- Cold workable down to temperatures of 0 °C
- Low self-heating during curing
- Very fast curing (approx. 140 seconds)
Areas of application
Lightweight sandwich components in GRP technology by subsequent foaming of cavities as well as for cold and heat insulation.
Curing
The PU rigid foam is two-component and therefore requires the addition of reactants for curing.
The mixing ratios are specified and should be adhered to exactly.
The curing reaction
Once the curing process has started, it continues by itself and cannot be interrupted. The curing time depends on the following factors:
- Working temperature
- Shape and size of the workpiece
The greater these parameters, the faster the curing reaction.
Storage
Suitable storage temperature 15 - 20 °C, never below 0 °C. Always close containers tightly, as the components are sensitive to moisture.
