Polyester foam and polyether foam are both derived from the polyurethane family of polymers. Polyurethanes are polymers (large molecules made up of monomer units) that contain urethane groups in the main chain of molecules. Polyester foam was developed first, but polyether foam eventually became the better known of the two. Nevertheless, they each have their strengths and weaknesses. These must be considered when deciding between these two foams.
Polyether Foam Manufacturing
Polyether foam is typically manufactured by mixing together a collection of chemicals with water. In addition to water, the mixture contains diisocyanate, polyol, catalysts and surfactant. As they are mixed together, the foam begins to emerge. As this happens, the mixture begins to rise in height. Between one and two minutes later, the foam will have reached its maximum height. The final mixture should 100 parts by weight of polyether triol, 40 parts tolylene diisocyanate, three parts water, 0.5 parts triethylenediamine, 0.3 parts stannous octoate and one part silicone block copolymer.
Polyether Foam Properties
Both polyether and polyester foam are flexible and are typically produced with densities between 1.5 and 3 pounds per cubed foot. Because ester, amine and urethane groups are susceptible to hydrolytic attack (and the ether groups are not), polyether foam is generally more resistant to hydrolysis than polyester foams. This means that polyether foams are preferable in moist or wet environments.
Polyester Foam Manufacturing
Polyester foams are most commonly produced in a slabstock form in basically the same way as polyether foam. Polyester foams use different chemical in their manufacturing. A finished batch of polyester foam should be 100 parts by weight of polyester, 33 parts tolylene diisocyanate, four parts water, two parts N-methylmorpholine, 2 parts N-Dimethylcetylamine and two parts ammonium oleate.
Polyester Foam Properties
Compared to polyether foams, polyester foam has a higher tensile strength, meaning it is more resistant to being pulled apart, superior elongation at break and a higher degree of hardness. This makes polyester foams preferable to polyether foams in textile applications. Polyester foam is also more resistant to hydrocarbons and alcohols compared to polyether foam.