Polyurethane foams come in two basic types: polyether and polyester. Both are flexible and typically come in densities between 1.5 and 3 lbs. per cubic foot. Each has specific attributes that make them useful in certain applications. This short blog post can help you determine which is best for your application.
Polyether urethanes typically contain a polyol (a reactive compound), a diisocyanate (one that reacts very well with the polyol), a catalyst, and a surfactant. These compounds react quickly and the mixture “foams” quickly.
Polyester urethanes are the older of the two types and are still fairly similar chemically.The “ester” is a class of compound derived from an acid and it is reacted with an alcohol. This reaction produces a long chain polymeric foam.
Properties and Applications
Polyester foams are generally stronger than polyether foams. They are more rigid and exhibit higher tensile strength. They are readily compatible with functional additives, such as fire-retardants, if unique properties are required. They are also more resistant to corrosive gases and chemicals than the polyether foams. They do have an Achilles’ heel, though, and that is hydrolytic stability. The polyesters are more expensive and susceptible to deterioration in damp or wet conditions. Polyether foams are generally softer, offer good cushioning capabilities, and exhibit superior resistance to moisture than the polyester based foams.
If your application involves any type of cushioning in moist or wet conditions, then polyethers are the better choice. If you need more tensile strength and support, the polyesters are typically a better way to go.