Foam rubber refers to rubber that has been manufactured with a foaming agent to create an air-filled matrix structure. Commercial foam rubbers are generally made of either polyurethane or natural latex. Latex foam rubber, used in mattresses, is well known for its endurance.
The main physical properties of foam rubber are generalized as being “Lightweight, buoyant, cushioning performance, thermal and acoustic insulation, impact dampening and cost reduction”. Crosslinking technology is used in the formation of EVA based foams, including LLDPE, LDPE, HDPE, PP, and TPE. Crosslinking is the most important characteristic in the production of foam rubber to obtain the best possible foam expansion and physical properties. Crosslinking is defined as chemical bonding between polymer chains, and is used for foam rubber manufacturing to stabilize bubble expansion, enhanced resistance to thermal collapse and improve physical properties.
Rates of polymerization can range from many minutes to just a few seconds. Fast reacting polymers feature short cycle periods and require the use of machinery to thoroughly mix the reacting agents. Slow polymers may be mixed by hand, but require long periods on mixing, as a result industrial application tends to use machinery to mix products. Product processing can range from a variety of techniques including, but not limited to spraying, open pouring, and molding.