Foam silicone stabilizer is a category of surfactant and can be classified into non-silicone compound and organosilicon compound. Currently, the most widely used foam stabilizer in the industry is polyether-modified organosilicon surfactants (commonly named as "silicone oil"). Its primary structure consists of block or graft copolymers of polysiloxane and polyalkylene oxide. Due to their broad range of structural variations, with excellent performance, polyether-modified organosilicon surfactant have been widely adopted as foam stabilizer in the polyurethane foam industry.

There are various structures of organosilicon foam stabilizer, the structure of silicone stabilizer which used in flexible foam, rigid foam, and high-resilience (HR) foam system is different. However, they generally contain repeating dimethylsiloxane units, ethylene oxide (EO) units, and propylene oxide (PO) units. One of the key functions of polyether-modified siloxane surfactants is to enhance the compatibility between PPU and the foam matrix, ensuring uniform dispersion of polyuria. This function is achieved through their polyether segments. The linkage between siloxane and polyalkylene oxide can take various forms, such as:

• AB-type linear block structure
• ABA-type linear block structure
• Single-branched and multi-branched structure

In the above structural formulas:

• R represents H, CH₃, C₂H₅, etc., most are methyl group.
• R" represents H or an organic group.
• (CH₂O)ₙ typically refers to random copolymers of ethylene oxide (CH₂CH₂O) and propylene oxide [CH(CH₃)CH₂O].
• R' represents an alkyl group or may be absent.

Based on the nature of the chemical bond connecting the polysiloxane and polyalkylene oxide segments—the linkage between silicon, oxygen, and carbon atoms—organosilicon surfactants can be classified into two types:

• Si-O-C type (silicon-oxygen-carbon chain)
• Si-C type (silicon-carbon chain)

• The Si-C bond does not undergo hydrolysis, allowing the product to be stored for long periods without deterioration. Therefore, silicone stabilizer used in rigid foam, high resilience foam is the Si-C type. Rigid foam stabilizer is typically polyether-polydimethylsiloxane copolymers, which are water-insoluble, non-hydrolyzable, and have emulsifying and nucleation effects. High-resilience foam stabilizers are also generally water-insoluble, non-hydrolyzable.
• The potency of polyester-based silicone surfactant should be significantly lower than polyether-based silicone surfactant. For cold-cured high-resilience foam systems and microcellular elastomers.
• Silicone stabilizers are generally colorless to pale yellow transparent liquids at room temperature.
• The dosage of silicone stabilizer ranges from 0.1% to 2.5%, typically between 0.5% and 1.5%. Higher dosages, finer cells, but may lead to closed-cell structures. In the same system, the dosage of silicone stabilizers for low density foam is generally higher than high density formulation. For HR foams with high TDI content system, a combination of foam stabilizers and foam modifiers may be used.
• In recent years, silicone stabilizers with low fogging, flame retardancy, low emission are very popular.