Flexible polyurethane foam (FPF) is a polymer produced from the reaction of polyols and isocyanates, a chemical process pioneered in 1937. FPF is characterized by a cellular structure that allows for some degree of compression and resilience that provides a cushioning effect. Because of this property, it is a preferred material in furniture, bedding, automotive seating, athletic equipment, packaging, footwear, and carpet cushion. It also plays a valuable role in soundproofing and filtration. In all, over 1.5 billion pounds of foam are produced and used every year in the U.S. alone.
Foam is most commonly produced in large buns called slabstock, which are allowed to cure into a stable solid material and then cut and shaped into smaller pieces in a variety of sizes and configurations. The slabstock production process is often compared to bread rising–liquid chemicals are poured onto a conveyor belt, and they immediately begin foaming and rise into a large bun (typically about four feet high) as they travel down the conveyor.
Raw materials for foam can also be poured into molds, where the cured foam assumes the size and shape of the mold. The processes for producing slabstock and molded foam are covered in a PFA training tutorial on Foam Production.
The basic raw materials for FPF are often complemented with additives that yield desired properties. These range from the comfort and support needed for upholstered seating to the shock-absorption used to protect packaged goods, to the long-term abrasion resistance demanded by carpet cushion. Some applications call for composites of FPF and other materials. For examples, headliners (the padded ceiling of an auto interior) typically consist of a nonwoven fabric laminated to a thin foam backing using heat.
The properties of foam can be measured and specified very precisely to allocate the right grade of foam to the right application. Foam performance is discussed on our Foam Performance page, and the test methods used to specify foam are covered under Industry Standards.