Foam Blowing

Foam rubber and plastics are products of a cellular form which may be either flexible or rigid. Flexible foams may be polyurethane, rubber latex, polyethylene or vinyl polymers. Rigid foams are chiefly polystyrene polyurethane, epoxy, and polyvinyl chloride. Sodium bicarbonate is commonly used as a "blowing agent" in the manufacture of these products.

A blowing agent is a substance incorporated in the melted plastic or rubber compound for the purpose of producing gas bubbles to form the foam structure as it cools.

Sodium bicarbonate, mixed with the plastic or rubber raw material, releases the required CO₂ gas bubbles upon application of heat in the mold or extruder. The cellular structure can be controlled by the amount of bicarbonate added or by the size and structure of the bicarbonate crystals.