There are two main types of foam rubber molding: open cell and closed cell. Open cell foam products are characterized by their interconnected networks of pores.
Closed cell foam products are the opposite; their pores are not connected, which makes closed cell foam products denser. Both varieties are used in a wide range of applications. Open cell foam rubber molding is used in the automotive industry for seat padding and trim material.
Other kinds of furniture like mattresses and pillows can also be made of open cell foam rubber. In industrial manufacturing, open cell foam rubber can be used in packaging and noise control applications.
Closed cell foam rubber molding is also used in the automotive industry but for thicker products. Construction companies make use of closed cell foam rubber for insulation and other thermal management applications. They are also used in sporting activities as knee and elbow pads, wetsuits and gloves. In healthcare settings, they can be used as orthopedic braces, surgical scrubbers and x-ray positioning pads.
Foam rubber molding is created through a polymerization process. At the beginning of this process, chemicals are placed into two large holding tanks. Then they are pumped into smaller, heated mixing tanks, and from there they are pumped into mixing heads which allow the blending of chemicals to occur.
The manner in which the chemicals are dispensed influences the type of foam rubber formed. For example, the use of continuous dispensing helps to form low-density foams in both rigid and flexible varieties. After the mixing, the foam must be cured before it can withstand further fabrication processes. Foam rubber is typically fabricated through a specialized injection molding process.
In this process, an inert gas such as nitrogen or carbon dioxide is introduced into the heated rubber material. Next, the foamable rubber composition, which now consists of a single phase polymer/gas solution, is then injected into the mold cavity; this allows for shaping of the foam into specific shapes for parts. A more recent development in foam fabrication is structural foam molding.
In this process, instead of utilizing high pressure to force the foam to fill up the mold cavity, the foaming action is instead caused by an inert gas that is distributed in the raw rubber material in order to assist flow.