Silicone Emulsion (PDMS Emulsion)

Chemistry and Structure

Silicone emulsion — also called PDMS emulsion or dimethicone emulsion — is an oil-in-water (O/W) dispersion in which polydimethylsiloxane (PDMS) droplets are stabilized by a shell of nonionic or anionic emulsifiers. The continuous aqueous phase allows the product to be diluted with water, pumped through standard aqueous processing equipment, and applied by conventional textile padding, spray, or bath exhaust methods without the handling concerns of neat silicone oil or organic solvent-based silicone systems.

Emulsification is achieved through high-shear homogenization of PDMS oil with emulsifier blends — typically combinations of ethoxylated fatty alcohols, polyoxyethylene sorbitan esters (Tweens), or sodium lauryl sulfate (for anionic grades). The resulting droplet size is a key quality parameter: microemulsions have droplet size below 0.15 µm and are optically transparent or translucent, whereas conventional macroemulsions have droplet sizes of 1–5 µm and appear milky white. Microemulsions penetrate fiber bundles more uniformly and deposit more evenly on hair surfaces, while macroemulsions provide higher active content per application volume and are preferred for release coating and industrial mold release applications.

Active (solid) content ranges from 30% to 60% by weight. At 30%, the product is easy to dilute but requires higher application volumes; at 60%, it offers cost efficiency in high-throughput textile finishing and paper operations. The base PDMS viscosity inside the emulsion affects final film properties: low-viscosity PDMS (50–200 cSt) gives lighter, more fluid films suitable for hair care; high-viscosity PDMS (500–10,000 cSt) gives more substantive, lubricious films for textile softening and heavy-duty mold release.

Properties and Performance

Water-based delivery system: The fundamental advantage of silicone emulsion over neat PDMS is the ability to use water as the carrier. This eliminates organic solvents, reduces VOC emissions, simplifies regulatory compliance, and enables use in water-sensitive processing environments such as food manufacturing, pharmaceutical production, and textile exhaust baths. Dilution with water is straightforward — simply add water under gentle agitation to achieve the required bath concentration.

Broad application compatibility: Nonionic emulsions are compatible with most anionic, cationic, and nonionic auxiliaries used in textile, paper, and personal care processing, making them versatile additions to complex formulation baths. Anionic emulsions work alongside other anionic surfactant systems without breaking.

Uniform PDMS deposition: The fine droplet size of emulsion grades (0.1–5 µm) allows PDMS particles to penetrate deeply into yarn bundles and fibrous structures, depositing a uniform, thin PDMS film on individual fiber surfaces. This is critical for textile softening — non-uniform deposition leads to patchy hand feel. In hair care, fine droplet size allows the PDMS to reach the hair cortex beneath the cuticle during conditioning.

Scalable active content grades: The 30%, 40%, and 60% active grades provide flexibility across applications: dilute 30% grades are used in spray applications and personal care rinse-off products; concentrated 60% grades are used in high-throughput padding mangle operations and industrial release systems where minimal water addition is desired.

Formulation stability: Well-formulated PDMS emulsions maintain stability at pH 4–8, temperatures up to 50 °C, and in the presence of electrolytes at moderate concentrations. They should not be subjected to freeze-thaw cycles, which cause irreversible droplet coalescence and cream separation.

Primary Applications

Textile finishing softener: PDMS emulsion is the foundational component of aqueous textile softener formulations. Applied by padding (5–30 g PDMS active/L bath, pick-up 70–100%) or exhaust (2–10% owf) to polyester, cotton, nylon, and blend fabrics, it deposits a coherent PDMS film that reduces inter-fiber friction, imparting the "silky" and "peach-skin" tactile effect consumers associate with premium fabric finishing. Unlike amino silicone, plain PDMS emulsion does not provide wash durability beyond 1–3 machine washes, but is effective for fast-fashion and commodity textile markets where cost per treatment is prioritized.

Paper and cardboard release coating: In the paper industry, diluted PDMS emulsion (0.5–2% active) is applied to the dryer section felts and press rolls of paper machines to prevent fiber adhesion and enable smooth sheet release. For release papers and silicone-coated label stock, PDMS emulsion provides the base release layer before specialized crosslinked silicone topcoats are applied.

Personal care — hair conditioning: In rinse-off conditioners and 2-in-1 shampoos, PDMS microemulsion (0.5–2% active) deposits a fine film on hair during contact time, reducing combing force and adding shine. Unlike amino silicone conditioners, plain PDMS emulsion washes out readily, providing immediate slip without long-term build-up — preferred for fine hair types and daily-use conditioners where build-up is a concern.

Personal care — skin moisturization: In body lotions, hand creams, and after-sun products, PDMS emulsion is incorporated at 1–5% to provide a non-greasy, smooth skin feel and form a light occlusive barrier. The water-in-oil feel on skin is cleaner than mineral oil at equivalent concentrations.

Concrete formwork release agent: Diluted PDMS emulsion (1–3% active in water) applied to concrete forms (timber, steel, fiberglass) before casting prevents concrete adhesion, allows clean strip-off, and leaves a minimal residue on the concrete surface. The aqueous format is preferred over solvent-based mold release in enclosed construction sites where VOC limits apply.

Industrial mold release and processing aid: In rubber molding, plastics processing, and food equipment lubrication, diluted PDMS emulsion replaces solvent-based silicone sprays, offering equivalent release performance with lower environmental impact.

Supply Chain Notes

PDMS emulsion is produced by established silicone manufacturers including Dow (DC 1953 series), Wacker (Finish CT series), Momentive, and numerous Chinese producers (Zhejiang Runhe, Shandong Dayi). Chinese-produced emulsions have improved significantly in stability and consistency over the past decade and now represent the majority of the global supply for textile and paper applications.

Grade selection parameters: (1) active PDMS content (30/40/60%); (2) PDMS base viscosity (50–10,000 cSt); (3) ionic character (nonionic vs. anionic); (4) droplet size (micro vs. macro emulsion). Request a Certificate of Analysis (CoA) specifying solid content (ISO 3251), pH, droplet size (laser diffraction), and accelerated stability test results (48h at 50 °C, centrifuge test).

Storage: sealed containers, 5–40 °C, avoid freezing. Shelf life: 6–12 months depending on grade. Drum agitation before use to redisperse any creamed material.

FAQ

What is the difference between 30%, 40%, and 60% active silicone emulsion? All three grades contain the same PDMS oil — only the concentration differs. A 30% grade requires three times more product volume to deliver the same PDMS active as a 60% grade. Higher active content reduces shipping cost and storage volume but may require more careful dilution. The 60% grade is favored in industrial and textile finishing operations; the 30% grade is more common in personal care formulations where precise dosing in small quantities is required.

Can silicone emulsion replace amino silicone emulsion in textile finishing? Plain PDMS emulsion provides good softness and lubricity but poor wash durability (1–3 washes). Amino silicone emulsion provides durable softness surviving 5–10+ washes due to ionic bonding to fiber surfaces. For commodity textiles or single-treatment garments, PDMS emulsion is cost-effective. For premium textiles and activewear requiring wash durability, amino silicone emulsion is the appropriate choice.

How do I prevent silicone emulsion from breaking in the application bath? Maintain pH within 4–8. Avoid adding strong acids, bases, or high concentrations of electrolytes to the bath simultaneously. Pre-dilute the emulsion in cold to warm water (not hot) before adding to the main bath. Incompatible auxiliaries (particularly cationic surfactants with anionic emulsions) should be added separately or replaced with a compatible ionic type.