To reconcile these contradicting each other characteristics, many manufacturers made seat on the principle of a sandwich, using different foam characteristics (eg, 2 layers of foam of various brands). In Depending on the values of hardness and density of foam used in furniture, are divided into Standard, soft, hard and highly elastic. Standard foam made on the basis of a single chemical component (polyols). The remaining foam may be based polyol with the addition of several different components that change properties in one direction or another, compared with the standard. Each manufacturer of upholstered furniture solves the problem of comfort in their own way.
Sometimes these solutions are the basis of success of a specific furniture. Top international companies make furniture not only multi-layered, but also with various zones of rigidity (different brand of foam around the perimeter and center), a combination of foam and latex, latex and springs, etc. For the manufacture of seats and mattresses are recommended foam density of at least 30 kg / cubic. However, most manufacturers Furniture economy class (both domestic and imported) uses the standard 25 th foam density. The most popular brand of the furniture is the ST 2534 – the cheapest. Unfortunately, this brand is fast enough loses its properties.
The service life of the foam, as the seats – no more than 1.5 years. Then the foam and cease prosyadet recover its shape. Another important indicator of foam – its recoverability (Permanent deformation). Recoverability – the percentage of characterizing permanent deformation of foam after repeated exposure to a load.