What Is Considered Foam

1. Polyurethane (PU) sponge foaming is to mix the raw materials, such as polyol, isocyanate (MDI/TDI), catalyst, foaming agent (such as water or physical foaming agent), silicone oil (to stabilize the foam cells), etc. in proportion.

In a chemical foaming reaction, water and isocyanate react to generate CO₂ gas, forming bubbles. Alternatively, a low-boiling point solvent (such as pentane) is added to the foam and evaporated into gas after heating to form foam.

2.Rubber sponge foaming: natural rubber or synthetic latex is mixed with a foaming agent (such as sodium bicarbonate) and a vulcanizing agent through latex mixing. During the mechanical foaming process, air is injected with high-speed stirring to form foam. This is then vulcanized and shaped, and the rubber is cross-linked and solidified by heating to stabilize the pore structure.

3. EVA (ethylene vinyl acetate) foaming, which is done by molding or injection, adding a chemical foaming agent (such as AC foaming agent), and heating and decomposing to produce gas.

In short, sponge foaming is a technique that creates a porous structure within a material through physical or chemical methods. It is widely used in the home, automotive, and medical fields. Different materials (such as PU, rubber, and EVA) use different foaming methods, but the core goal is to control cell size, uniformity, and stability to meet the performance requirements of different products.