According to the degree of hardness, that is, the load-bearing performance, polyurethane flexible foam can be divided into ordinary soft foam, super soft foam, high-load-bearing soft foam, high-resilience foam plastic, etc. Among them, high-resilience foam and high-load-bearing soft foam are generally used to make cushions and mattresses.
Polyurethane soft foam can be divided into block foam and molded soft foam according to the production process. The former is a large volume of foam produced by a continuous process and then cut into foam products of the required shape. Molded foam (produced in a mold) can be divided into hot-cured soft foam and cold-cured soft foam according to the curing method.
The earliest flexible polyurethane foam was produced by box foaming process using polyester polyol and TDI-65. Now, the output of polyester soft foam is very small, and it has been replaced by polyether soft foam with better elasticity. However, polyester PU soft foam is still produced for some special occasions. For example, high elongation soft foam made of low-branching polyester polyol and TDI-65 or TDI-80 is mainly used in the interlayer of textiles.
Currently, 90% of polyurethane soft foams are produced with polyether polyols, most of which are general-purpose soft foams (mainly block foams) and high-resilience soft foams. There are also a small number of special soft foams such as super-soft foam plastics, high-load-bearing foam plastics, slow-resilience foam plastics, hydrophilic soft foams, sound-absorbing foam plastics and soft foams for filtration (including reticulated foams).