Sponge: Polyurethane and polyethylene condensate, white or yellowish amorphous solid. Its softening point is higher than that of its homologous acetals (140-150 C). Its strength, rigidity and hardness are larger, and it has good bonding properties. It has good oil resistance, electrical insulation, water resistance, alkali resistance and acid resistance. Flammable, black smoke. Melt dripping and has a special odor.

Bubble foam: high density, stronger liquid absorption, more tough and elastic foam, good wear resistance, will not scratch wiped devices, will not chip. Particles and liquids will not fall out or extrude easily when they enter foam holes, so they have good locking ability.

Foam is a porous elastomer obtained by crosslinking reaction of a specific water-soluble resin. It has strong water absorption ability because of its hydrophilicity in molecular structure. PVA foam is different from ordinary methylcarbamate sponge in that it has very high hydrophilicity and capillary phenomenon with crisscross micro-pore, which exerts super-group water absorption and water retention performance. When water is in contact, it is adsorbed at high speed and stored in the body of the sponge. Generally, the water absorption rate is 8-10 times of its own weight.