Section
| HS Code | 633111 |
| Product Name | SILFOAM SD 168 Self-Emulsifying Polyether-Modified Silicone Defoamer |
| Product Type | Defoamer |
| Chemical Class | Polyether-modified silicone |
| Active Substance Content | 100% |
| Appearance | Clear to slightly turbid liquid |
| Color | Yellowish |
| Physical State | Liquid |
| Viscosity At 20 C | 1500-3000 mPa·s |
| Density At 20 C | Approx. 1.0 g/cm³ |
| Ph 1 In Water | Approx. 6 |
| Solubility In Water | Self-emulsifying; forms a milky dispersion |
| Ionic Character | Non-ionic |
| Solvent Content | Solvent-free |
| Thermal Stability | Stable under standard processing and storage temperatures |
As an accredited SILFOAM SD 168 Self-Emulsifying Polyether-Modified Silicone Defoamer factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | SILFOAM SD 168 is packaged in 25 kg pails, 200 kg drums, and 1,000 kg IBCs, sealed for safe transport. |
| Container Loading (20′ FCL) | 20′ FCL container loading: palletized drums or IBCs of SILFOAM SD 168, securely stowed, maximizing volume and weight within container limits. |
| Shipping | Ship as non-hazardous goods in original, sealed containers, typically drums or IBC totes. Protect from extreme temperatures, freezing, and moisture. Store upright and secure during transport to prevent leakage. Ensure proper labeling and documentation, avoiding contamination with other chemicals to maintain product stability and performance upon delivery. |
| Storage | Store SILFOAM SD 168 in its original, tightly closed container in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and freezing conditions. Recommended storage temperature is below 25°C. Avoid contamination and moisture ingress. If separation occurs, gently stir before use. Follow manufacturer’s shelf-life guidelines for best performance. |
| Shelf Life | Shelf life is typically 18 months from manufacture when stored in original containers below 40°C, avoiding freezing. |
In a semi-synthetic metalworking fluid concentrate, foam generation is not primarily a blending problem; it emerges after the concentrate is diluted to 5%–8% by volume in service water containing 150–400 ppm hardness and pumped through a central system. The air-entrainment capacity of the fluid rises when amide-based lubricity packages, sulfonate corrosion inhibitors, and fatty acid soaps are combined, especially when tramp oil is present. At a delivery pressure of 20–50 bar through nozzles and a return flow of 20–60 L/min into a 1,000 L reservoir, entrained air accumulates as a stable foam cap if the defoamer particle size distribution is incorrect. SILFOAM SD 168 is introduced into the concentrate at 0.05–0.3 wt% after the emulsion has formed and the pH has been adjusted to 9.0–9.5; addition before neutralization of alkanolamine may lead to slow droplet coalescence and hazy concentrate. The self-emulsifying polyether-modified siloxane disperses without a separate emulsification step, but excessive post-addition mixing above 3,000 rpm in a high-shear dissolver can reduce the silicone droplet diameter below the critical size required for bubble bridging. In recirculating sump tests, a modified ASTM D892-23 aeration procedure with a 60 L reservoir and 10 L/min air flow through a gas diffusion stone is used; the formulation is considered acceptable when foam collapse to 10 mm occurs within 60 s after aeration stops. Published data for this specific SILFOAM SD 168 configuration under central coolant systems is limited, and the 0.05–0.3 wt% range should be narrowed by sulfonate titration because batch-to-batch variation in sulfonate content can shift the required dose by 0.1 wt% or more.
During horizontal bead milling of a suspension concentrate, air is not introduced deliberately; foam is generated by the high surface area of the millbase, the mechanical vortex in the premix vessel, and the surfactants required for wetting and dispersion. A typical 20 L batch in a horizontal bead mill with 0.6–1.0 mm zirconium oxide beads and tip speed 10–14 m/s can develop a persistent froth in the feed hopper, causing air ingestion into the milling chamber and loss of grinding efficiency. SILFOAM SD 168 is added to the millbase at 0.1–0.5 wt% before the active ingredient and dispersing agents are fully hydrated, then a second portion at 0.05–0.2 wt% is added after viscosity adjustment to 200–800 mPa·s at 25°C. The self-emulsifying siloxane is selected because high-shear milling can destroy a conventional polydimethylsiloxane emulsion, but overdosing above 0.5 wt% may produce wet-sieve retention failure under CIPAC MT 59 due to microfoam coating of the active particles. Foam persistence is measured per CIPAC MT 47.3 in a 250 mL graduated cylinder after 30 inversions; a suspension is typically accepted when initial foam height does not exceed 20 mL after 1 min. In tank mix, the product is diluted 1:5 in water before introduction to avoid localized silicone-rich phases; compatibility with ammonium sulfate and potassium chloride carriers must be tested because high ionic strength can reduce the cloud point of the polyether block and cause silicone separation.
Alkaline cleaning lines operating at 60–85°C with air-assisted spray bars generate foam volumes that are not predicted by static Ross-Miles measurements at 25°C. The thermally activated desorption of dissolved air from the cleaning solution and the high shear of nozzles produce microfoam that persists in recirculated wash tanks. In a concentrated detergent containing 5–15 wt% sodium hydroxide, 2–8 wt% sodium metasilicate, and 3–10 wt% of a mixed anionic/nonionic surfactant package, SILFOAM SD 168 is prediluted 1:3 in cold process water and added at 0.01–0.1 wt% of the concentrate after neutralization of the builder system. Addition directly to 15 wt% sodium hydroxide at >50°C can trigger hydrolysis of the siloxane backbone and reduce defoamer longevity; the operational boundary is therefore to maintain the formulation pH below 12.5 during storage or to dose the defoamer into a nonionic surfactant premix before alkaline ingredients are incorporated. Foam performance is measured in a Ross-Miles apparatus per ASTM D1173-07 with 200 mL test solution at 50°C and 0.2 wt% linear alkylbenzene sulfonate in 150 ppm hardness water; initial foam height after 30 s is recorded. Formulations containing hypochlorite above 5% active chlorine are outside the recommended operating window because oxidative cleavage of the siloxane backbone eliminates the defoaming activity within 24–48 h.
| Application segment | Test standard or instrument | Process condition | Typical addition |
|---|---|---|---|
| Metalworking fluid concentrate | ASTM D892-23 modified | 60 L sump, 24°C, 10 L/min air | 0.05–0.3 wt% concentrate |
| Agrochemical suspension concentrate | CIPAC MT 47.3 | 250 mL cylinder, 30 inversions | 0.1–0.5 wt% millbase |
| Alkaline cleaning concentrate | ASTM D1173-07 | Ross-Miles, 50°C, 200 mL | 0.01–0.1 wt% concentrate |
| Polyester jet dyeing | Internal recirculation rig | 130°C, 3–5 bar nozzle pressure | 0.05–0.2 g/L bath |
| Kraft weak black liquor | Dynamic foam analyzer with G2 frit | 80°C, pH 12.5, 1 L/min nitrogen | 0.05–0.2 kg/t dry solids |
| Water-based ink and overprint varnish | ASTM D1003, ASTM D523 | Blade coater, >400 m/min | 0.1–0.3 wt% total ink |
When a polyester jet dyeing machine recirculates a foamy dye bath at 130°C and 3–5 bar nozzle pressure, fabric transport becomes uneven because foam cushions the reel and reduces the hydraulic drag that keeps the rope moving. In a typical high-temperature jet with a liquor ratio of 1:8 to 1:15 and fabric speed of 200–400 m/min, air entrainment is generated by turbulence in the venturi and by the release of dissolved air during heating. SILFOAM SD 168 is pre-diluted 1:5 with water and injected into the feeder tank at 0.05–0.2 g/L, preferably after the dye has dispersed and the bath has reached 60°C. The upper limit of 0.3 g/L should not be exceeded because excess silicone can deposit on polyester as hydrophobic spots and reduce dye uptake, particularly with high-energy disperse dyes. Colorfastness to laundering under AATCC TM61-2010 Test 2A is typically used to confirm that no surfactant or defoamer residue remains after the wash-off stage. Self-emulsifying polyether-modified siloxane droplets migrate to the air-water interface rather than to the fiber-water interface, but the process window is narrow in package dyeing machines with high liquor-swelling, because flow reversal through the yarn package increases shear and may overdisperse the defoamer.
Kraft weak black liquor at 15%–18% dissolved solids and 70–90°C contains tall oil soaps, lignin fragments, and residual cooking liquor that stabilize a dense foam blanket in washing, screening, and evaporator feed tanks. The primary problem is not simple foam height but foam that entrains black liquor solids and reduces evaporator heat transfer and storage tank working volume. SILFOAM SD 168 is split-dosed at 0.05–0.2 kg/t dry solids into the weak black liquor line and at 0.1–0.5 kg/t dry solids into paper machine white water or broke systems where starch, retention aid, and latex from coated broke increase foam stability. A dynamic foam analyzer with a nitrogen sparge rate of 1 L/min through a G2 sintered frit is used to measure foam height at 80°C and pH 12.5; the defoamer is considered spent when foam height reaches 50% of the initial defoamer-free value. In food-contact paper applications, the formulation must reference 21 CFR 176.210, and the supplier’s technical documentation must confirm that the polyether-modified siloxane and any emulsifier fall within the listed substance conditions; no food-contact clearance should be assumed without reviewing the specific lot certificate. Operation above 90°C in black liquor can reduce service life because the siloxane backbone undergoes hydrolytic cleavage at high pH, and the resulting species are less surface-active at the air-liquor interface.
Blade coaters shift the required defoamer dosage when substrate speed exceeds 400 m/min because the shear zone under the blade and the open transfer pan generate microfoam that is not visible as a foam cap but appears as pinholes and haze in the dried film. In water-based flexographic and gravure inks based on acrylic and polyurethane dispersions, SILFOAM SD 168 is incorporated during letdown at 0.1–0.3 wt% of total ink weight, after the pigment dispersion step and before the final viscosity adjustment to 25–40 s on a DIN EN ISO 2431:2019 cup with a 4 mm orifice at 25°C. High-speed dispersing above 1,500 rpm after addition is avoided because the defoamer droplet size becomes too small and wetting tension on corona-treated polyethylene drops below 38 mN/m as measured by ASTM D2578. In overprint varnish, the maximum addition is 0.5 wt%; beyond this level haze increases above 2% as measured by ASTM D1003, and 60° gloss measured by ASTM D523 can decline by more than 10 GU due to surface silicone migration. An alternative addition point is the fountain solution in offset lithography, but this requires a separate compatibility test because the acid pH of 4.5–5.5 in the fountain solution may hydrolyze the siloxane backbone over 24 h.
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SILFOAM SD 168 Self-Emulsifying Polyether-Modified Silicone Defoamer is a 100 % active nonionic polyether-modified polysiloxane liquid supplied for direct introduction into aqueous manufacturing processes. The product does not require the separate pre-emulsification step that conventional silicone emulsions demand, because polyether substitution on the siloxane backbone imparts spontaneous emulsifiability when the material contacts water under low shear. Typical incoming quality-control data include a viscosity range of 800–2500 mPa·s at 25 °C and a density of approximately 1.00 g/cm³ at 25 °C, measured by rotational viscometry and pycnometric or oscillating U-tube density methods aligned with ISO 3219 and ISO 2811-1. The product appears as a turbid, yellowish liquid and, when diluted to 1 % in deionised water, forms a milky dispersion without external surfactants. This delivery mechanism distinguishes SILFOAM SD 168 from mineral-oil defoamers, hydrophobic silica-silicone compounds, conventional silicone emulsions, and polyether block-copolymer defoamers in terms of active content, storage behaviour, and defect profile. Primary application fields include waterborne architectural coatings, printing inks, emulsion polymerisation, and waterborne adhesives, where mechanical shear, recirculation, spray application, or gas evolution generates persistent foam and entrained air.
| Parameter | Typical value or range | Method or instrument |
|---|---|---|
| Active content | 100 % | Non-volatile content determination |
| Viscosity | 800–2500 mPa·s at 25 °C | Rotational viscometer, ISO 3219 alignment |
| Density | Approximately 1.00 g/cm³ at 25 °C | Pycnometer or oscillating U-tube, ISO 2811-1 alignment |
| Appearance | Turbid, yellowish liquid | Visual inspection |
| Self-emulsification | Milky dispersion at 1 % in deionised water | Low-shear jar test |
The defoaming mechanism of a self-emulsifying polyether-modified silicone depends on the ability of the dispersed droplets to enter and spread on bubble lamellae. In an aqueous foam stabilised by surfactants, the low surface tension of the siloxane phase creates a surface tension gradient that destabilises the thin liquid film. The polyether side chains are essential for controlled spreading; without them, a pure polydimethylsiloxane fluid can over-spread and create surface craters in the target coating. The product can therefore function as both an anti-foam and a deaerator: it reduces surface foam at the liquid-air interface and accelerates the rise of entrained microbubbles in viscous media. In latex paints, the latter property is important because stirred cans can retain air bubbles that later appear as pinholes after drying. The efficiency of deaeration is often evaluated by measuring the density recovery of a freshly mixed coating after high-shear air entrainment; the time required to return to a foam-free density is a formulation-dependent indicator of defoamer performance.
Conventional silicone emulsion defoamers are supplied as aqueous emulsions with active silicone contents frequently in the 10–30 % range. Their droplet size distribution is fixed during manufacturing and can shift during storage, particularly after freeze-thaw cycles, electrolyte exposure, or prolonged exposure to ambient air. SILFOAM SD 168 is a 100 % active liquid that forms an emulsion at the point of use, so the emulsion droplet size is controlled by the shear field of the target process rather than by the stability of a preformed emulsion. This distinction is operationally significant in automated dosing systems: a separated conventional emulsion can block filters, create inconsistent dosing, and require recirculation or mixing before use. The self-emulsifying polyether-modified silicone also avoids the introduction of the external surfactant load that accompanies conventional silicone emulsions. The polyether substituents on the siloxane chain orient toward water and provide interfacial anchoring, while the siloxane core supplies low surface tension and film-spreading characteristics. This balance reduces the cratering tendency relative to a fully hydrophobic polydimethylsiloxane fluid, but it does not eliminate defect risk when the product is dosed above the compatibility window of a given paint or ink. Compared with mineral-oil defoamers, SILFOAM SD 168 introduces no volatile mineral oil into the formulation, which aligns with low-VOC coating designs. Compared with polyether defoamers, the silicone backbone typically provides more rapid foam knockdown at lower dosage, although published side-by-side data in waterborne alkyd systems are limited.
During latex paint manufacturing, the product is typically split between the pigment-grind stage and the let-down stage. In a high-speed dissolver operating with a peripheral tip speed of 10–20 m/s, the defoamer can be post-added to the mill base to collapse air bubbles entrained during the wetting of titanium dioxide and extenders. A further portion, added after thickener and binder let-down, controls can foam and air release in the final formulation. The effective dose in architectural paints generally spans 0.05–0.5 wt% of total formulation; however, the lower end is typical for binder-rich gloss paints and the upper end for highly filled flat paints or formulations with high free-surfactant levels. Foam control is evaluated by high-shear laboratory mixing with a rotor-stator device at 8000 rpm for 60 s, followed by foam-height measurements at 1 min, 5 min, and 60 min, as well as by drawdown application on sealed Leneta charts using a 100 µm wet-film bar. Craters, pinholes, and film discontinuities are counted after 24 h of drying at 23 °C and 50 % relative humidity. Over-addition is typically detectable as an increase in surface depressions and intercoat adhesion loss, but the precise threshold is not fixed and depends on coalescent level, latex particle size, and rheology modifier chemistry.
Emulsion polymerisation reactors impose a different shear and temperature environment than paint let-down tanks. In a stirred reactor with a jacket temperature of 70–85 °C during acrylate or vinyl acetate polymerisation, the defoamer must remain active without generating volatile low-molecular-weight species that contribute to reactor fouling. SILFOAM SD 168 is introduced at 0.1–0.5 wt% based on total monomer, either as a single pre-polymerisation charge or as a split charge during the monomer feed. The optimum point of addition depends on reactor geometry; in a vessel with a 3:1 height-to-diameter ratio and a pitched-blade turbine at 40–80 rpm, injection into the agitator vortex disperses the defoamer rapidly, whereas injection into a low-velocity recirculation line may produce local concentrations that exceed the dispersion capacity of the latex and generate oily nodules. During vacuum stripping of residual monomer, foam can enter the condenser and cause carry-over. For this operation, a diluted stream of 1–10 % SILFOAM SD 168 in water is metered into the stripping column or reactor recirculation loop at 0.05–0.2 wt% per hour, with the dilution prepared fresh and consumed within one shift. The product is a chemical foam-control aid and is not a substitute for vacuum deaeration or condenser mist elimination. Published data for this specific reactor configuration is limited; therefore, dose titration and foam-sensor response monitoring are required before inclusion in a control strategy.
Compatibility boundaries are most evident in high-gloss latex enamels, clear wood coatings, and water-based overprint varnishes, where surface defects are visible under oblique lighting. In these systems, additions above 0.3 wt% of total formulation are more likely to produce craters, pinholes, or loss of distinctness of image because the defoamer can remain as discrete low-surface-energy droplets in the wet film. The threshold is lower in low-PVC formulations, where there is less pigment surface area to adsorb excess defoamer, and in systems using associative thickeners, because hydrophobic interactions between the thickener and the polyether-modified silicone can alter low-shear rheology. Staged addition is therefore employed: the defoamer is introduced before final thickener adjustment, and the formulation is allowed to mix at low speed for 15–30 min before testing. A production-scale dissolver with a variable-frequency drive can be used to maintain controlled tip speed during defoamer incorporation; high-shear post-dispersion after thickener addition may reduce defoamer droplet size and increase the risk of surface defects. In high-gloss coatings intended for roller application, manual evaluation of foam during rolling and drying is supplemented by 20° gloss measurements and by ASTM D5767 distinctness-of-image measurements where available. Published correlations between wet-film defect counts and dry-film distinctness of image are formulation-specific; no universal pass-fail dosage can be derived from the product specification alone.
Water-based flexographic and gravure inks create microfoam when the ink pump recirculates through the doctor chamber and anilox roll. SILFOAM SD 168 can be added directly to the ink sump at 0.1–0.3 wt% of ink weight; the addition should be made under continuous stirring to avoid local concentration gradients. In high-speed printing trials on corona-treated polyethylene and polypropylene films, over-addition is detected as pinholes, motting, or wetting failure in solid print areas. The self-emulsifying behaviour is advantageous in ink systems that are heavily pigmented and contain little free water; the product disperses without a high-shear pre-emulsion step that can alter pigment dispersion stability. Mineral-oil defoamers in water-based inks may contribute to printability defects and are restricted where low migration is required; SILFOAM SD 168, as a high-molecular-weight polysiloxane, is not volatile but must still be assessed for specific packaging migration requirements under the applicable regulation. Published data for specific pigment and polymer combinations are limited, so a drawdown series with 0.05 %, 0.1 %, and 0.3 % additions is recommended before a press trial.
Storage and handling boundaries for SILFOAM SD 168 are defined by its 100 % active, self-emulsifying character. Containers should remain sealed and protected from moisture ingress; prolonged exposure to humid air can increase haze and viscosity without indicating microbial spoilage. The product should be stored at 5–30 °C, and frost exposure below 0 °C may create non-uniform viscosity that requires warming to 25 °C and gentle mixing before use. If a pre-diluted feed solution is necessary for continuous metering, it should be prepared at 1–10 % concentration in deionised water and consumed within one production shift; the dilution is not a stabilised emulsion and will separate if stored. SILFOAM SD 168 is designed for aqueous systems and is generally unsuitable for anhydrous solvent-borne formulations or for water-miscible co-solvent blends above formulation-specific critical concentrations. It should not be mixed with strong oxidising agents or used as a replacement for mechanical deaeration equipment. Bulk handling in epoxy-lined or stainless steel equipment is preferred; compatibility with hoses, gaskets, and metering pumps should be verified because silicone fluids can permeate certain elastomers. Regulatory compliance, including REACH registration status and food-contact suitability, must be confirmed against current supplier documentation for the intended application.
