| HS Code | 380675 |
| Product Name | Silicone Defoamer RH-9208 |
| Chemical Composition | Polysiloxane-based silicone defoamer |
| Appearance | Milky white to light yellow liquid |
| Odor | Slight characteristic odor |
| Active Content | 10%–30% |
| Solid Content | 20%–40% |
| Viscosity At 25 C | 500–2000 mPa·s |
| Density At 25 C | 0.95–1.10 g/cm³ |
| Ph Value | 6.0–8.0 |
| Ionicity | Nonionic |
| Water Solubility | Dispersible in water |
| Flash Point | >100°C |
| Storage Temperature | 5°C–35°C |
| Shelf Life | 12 months in unopened container |
| Freeze Stability | Avoid freezing; restore by warming and mixing |
As an accredited Silicone Defoamer RH-9208 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Silicone Defoamer RH-9208 is packaged in 25 kg sealed plastic drums, with 200 kg drums available for bulk orders. |
| Container Loading (20′ FCL) | Container Loading (20′ FCL): Silicone Defoamer RH-9208 packed in drums, palletized and secured inside a 20-foot FCL container for ocean shipment. |
| Shipping | Silicone Defoamer RH-9208 is shipped in sealed 25/200 kg drums or IBC totes, clearly labeled according to its SDS. It is generally handled as a non-hazardous industrial chemical; keep containers closed, protect from freezing and extreme heat, and avoid contamination during transport under local regulations. |
| Storage | Store Silicone Defoamer RH-9208 in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep containers tightly closed to prevent contamination and moisture ingress. Protect from freezing and extreme temperatures. Store separately from incompatible materials, use spill containment, and follow the SDS and label instructions. |
| Shelf Life | Shelf life: typically 12 months from manufacture when stored unopened in a cool, dry, ventilated area, away from direct sunlight. |
In high-PVC waterborne architectural coatings manufactured on 5,000–10,000 L high-speed dispersers, foam stabilisation during pigment grind and final let-down frequently shifts with extender type and associative thickener package. RH-9208, as an aqueous silicone emulsion defoamer, is introduced in split-feed fashion: 50% of the selected dose is charged into the mill base before dispersed pigments and extenders, and the remaining 50% is post-added after the thickening stage under low-shear mixing. Typical addition ranges from 0.10 to 0.50 wt% of total formulation mass; formulations above 0.65 wt% tend to develop craters and gloss reduction, particularly in silk-emulsion topcoats with HEUR associative thickeners. The defoamer’s regulatory position for architectural coatings sold in the European Economic Area falls under Directive 2004/42/EC, with VOC contribution measured by ISO 11890-2; paint formulators targeting the 2010 low-VOC phase must verify that the defoamer’s solvent content does not push the finished coating above the subcategory limit. On a production line using a 450 mm cowles blade at tip speeds of 18–22 m/s, maximum foam knockdown is observed when the mill base temperature remains below 50 °C and the silicone droplet is not exposed to prolonged high-shear after 20 min, which can destabilise the emulsion and reduce knockdown performance. Downstream processing includes vacuum deaeration at 0.08 MPa for 10–15 min in closed vessels after let-down, followed by filtration through 150–250 µm mesh. Terminal products include interior matt emulsions, water-based satin enamels, exterior masonry coatings and elastomeric roof coatings. In batch records, foam carryover is most frequent when the mill base is discharged at viscosity below 0.5 Pa·s and the let-down vessel has only 10% headspace, forcing air back into the liquid on transfer.
In closed white water systems on paper and board machines, RH-9208 is metered not as a batch additive but as a continuous dilution feed into the wire pit or silo at 0.05–0.20 kg per t dry fibre, with diluted material prepared at 1–5% active emulsion in water. The addition point is placed upstream of defoamer-friendly screens and downstream of the save-all, because turbulent discharge from the fan pump can shear the emulsion if retentate levels exceed 45 °C. Compliance for food-contact paper and board intended for dry and aqueous foodstuffs is governed by FDA 21 CFR 176.170 and FDA 21 CFR 176.180, while European converters often require conformity to BfR Recommendation XXXVI and harmonised migration limits under Regulation EC 1935/2004; the defoamer must not introduce substances that cause non-compliance after sheet drying. In production, foam-related breaks on high-speed gap formers are most commonly observed when the white water chest receives broke with high starch loading; RH-9208 addition can suppress visible air entrainment but does not remove the underlying cationic demand imbalance. Overuse above 0.3 kg/t can create deposition on forming fabrics and press felts, especially in machines running higher recycled fibre load with stickies. Terminal output includes printing and writing papers, coated folding box board, gypsum board liner and white-top testliner. Published data for this specific configuration is limited; the feed point and dose are typically validated by monitoring first-pass retention and wire pit foaming during an 8 h trial.
Where mechanical surface aerators entrain air into mixed liquor at municipal plants, RH-9208 is applied by diaphragm metering pump into the aeration lanes or influent channel at 2–10 mg/L as supplied, with the lower value used for low-MLSS oxidation ditches and the upper value for intensively mixed activated sludge basins exceeding 4,000 mg/L MLSS. The main regulatory boundary is local discharge consent under the Industrial Emissions Directive 2010/75/EU, rather than a product-specific defoamer standard; plant operators must confirm that organic loading from the defoamer does not raise final effluent COD beyond permit limits. Terminal products are treated effluent suitable for discharge or tertiary reuse and stabilised waste sludge. Because excessive dosing increases interfacial oxygen transfer resistance, continuous feed is preferred over slug addition. Published data for this specific configuration is limited.
In agrochemical suspension concentrates containing high loads of technical active ingredients, RH-9208 is added to the mill base before wet grinding at 0.05–0.20 wt% of the formulation mass, because foam generated during horizontal bead milling increases chamber pressure and reduces the energy transferred to particle size reduction. The standard milling line comprises a horizontal stirred-media mill charged to 75–85% with 0.6–1.0 mm yttria-stabilised zirconia beads, operated at tip speeds of 10–14 m/s with jacket outlet temperature held at 20–30 °C. Defoamer performance is assessed under CIPAC MT 47.3 foam characterisation and accelerated storage at 54 °C for 14 days, with final formulations also checked for wet sieve retention using a 75 µm screen according to CIPAC handbook methods. Regulatory anchors include FAO/WHO pesticide specifications for the formulated product and REACH Regulation (EC) No 1907/2006 for the defoamer as a co-formulant. At doses above 0.30 wt%, emulsion droplets can coalesce into visible surface oiling and may interact with dispersants such as sodium lignosulfonate, causing flocculation of the suspended active. Terminal products include 250–500 g/L aqueous suspension concentrates, suspoemulsions and flowable seed treatment formulations. Published data for this specific configuration is limited; formulation transfers across active ingredients require wet milling trials rather than extrapolation from simple foam-height reduction.
Continuous defoaming in fed-batch bioreactors becomes process-critical when foam probes trigger addition loops at 50–200 m³ working volume under 0.5–1.5 vvm air sparging and 150–300 rpm agitation. RH-9208 is introduced via a peristaltic pump at 0.01–0.10% v/v of initial working volume, usually sterilised by autoclaving or aseptically filtered if the emulsion tolerates the selected sterilisation membrane. In food-grade fermentations, the defoamer must comply with FDA 21 CFR 173.340 as a defoaming agent used in food processing, and relevant FCC monographs apply to raw materials and residual limits. The production issue most often encountered in yeast extract and amino acid plants is late-stage foam stabilisation by high protein concentration and cell debris; the defoamer reduces foam height but can foul downstream crossflow microfiltration membranes when residual silicone exceeds the membrane manufacturer’s tolerance. Terminal products include L-lysine, sodium glutamate, citric acid, yeast extract and enzyme preparations. Foam control in animal-cell culture is not recommended due to cell sensitivity and downstream purification; RH-9208 is applicable only to microbial submerged aerobic systems and not to microcarrier-based or serum-containing processes without specific qualification. Published data for this specific configuration is limited; pilot-scale evaluation under identical sparge and agitation conditions is required before full-scale feed settings are modified.
In high-temperature jet dyeing of woven and knitted goods, RH-9208 is dosed at 0.05–0.20 g/L of bath volume immediately after the bath is raised to 50 °C and before the temperature ramp to 130 °C for polyester blends. The addition is made through the chemical dosing tank under circulation, not directly into the nozzle where high shear can break the emulsion and deposit silicone on fabric surfaces. Compliance in branded textile supply chains is usually evaluated against OEKO-TEX Standard 100 Annex 4 restrictions and screening against ZDHC MRSL V3.1; the defoamer has no intended textile finishing function but must not contain listed solvent impurities. Production machines with nozzle pressures of 2–4 bar and rope circulation speeds of 250–400 m/min can develop foam-related rope marking and pump cavitation when residual scouring surfactants are not rinsed before dyeing. Terminal articles include finished polyester-cotton shirting, lyocell-blend garment fabrics, and technical knit fabrics. At dosing above 0.30 g/L, silicone spotting can be difficult to remove and may interfere with subsequent water-repellent finishing. During pad-batch pre-treatment of cotton knits, residual defoamer can reduce fabric absorbency if not removed by alkaline scouring; because RH-9208 is not a wetting agent, dye houses should verify capillary rise after finishing when enzymatic desizing is followed by one-bath peroxide bleaching. Published data for this specific configuration is limited.
Competitive Silicone Defoamer RH-9208 prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please contact us at +8618005193850 or mail to sales8@bouling-chem.com.
We will respond to you as soon as possible.
Tel: +8618005193850
Email: sales8@bouling-chem.com
Flexible payment, competitive price, premium service - Inquire now!
Silicone Defoamer RH-9208 is a water-dilutable, non-ionic silicone emulsion formulated from a polydimethylsiloxane active component and dispersed hydrophobic silica. The product designation places it among emulsion-type defoamers intended for aqueous processing streams rather than solventborne or mineral-oil formulations. The carrier water and non-ionic emulsifiers allow the product to be added without pre-dispersion in many aqueous applications, but the same emulsifier system makes the product sensitive to high-shear and freeze-thaw aging. In a two-minute nitrogen sparge test based on ASTM E2407-04, the product is evaluated at 0.1% to 0.3% by total batch mass; published data for this specific model is limited, and users are advised to benchmark performance against a reference defoamer under identical sparge-column geometry. The primary operational distinction from mineral-oil and polyether defoamers is the low equilibrium surface tension of the siloxane phase, typically 21 mN/m to 24 mN/m when measured by ASTM D1331-14. This low surface tension enables spreading at foam lamellae at lower addition rates, but it also increases the risk of surface defects in clear or high-gloss coating systems if overdosed.
Release specifications for the emulsion are normally expressed in terms of pH, Brookfield viscosity, density, non-volatile content, and particle-size distribution. Typical quality-control limits include pH 6.0–8.0 measured by glass electrode according to ASTM E70-19, viscosity at 25 °C of 500–3000 mPa·s at 20 rpm using a Brookfield RVT viscometer per ISO 2555:2018, and density 0.98–1.02 g/cm³ at 25 °C by ISO 2811-1:2016. Non-volatile matter is determined at 105 °C for 2 h per ISO 3251:2019; batch-to-batch variation in non-volatile content greater than ±1.0 percentage point can shift defoamer efficiency in viscosity-sensitive acrylic and alkyd formulas. Laser diffraction particle sizing per ISO 13320:2020 is used to control median particle size below 20 µm and D90 below 50 µm; larger droplets increase the risk of filter plugging in fine filtration steps. Because the product is a dispersion rather than a solution, shipment and storage history influence these values more than they influence solvent-based defoamers.
For incoming quality assurance, a simple oven method at 105 °C is insufficient to distinguish active siloxane from non-volatile emulsifier degradation products; gravimetric solids by ISO 3251:2019 should be supplemented by Fourier-transform infrared spectroscopy or extraction to confirm active concentration. Production-scale tanks should be sampled at the top, middle, and bottom after a 24 h settling period because creaming can produce a viscosity differential of 200–800 mPa·s between the upper and lower zones. Homogenization before use in a diaphragm or piston pump may be required when the product has been stored for more than 6 months.
Knockdown efficiency in high-solid waterborne coatings is not governed solely by active content or surface tension; it is strongly affected by the surface age of the foam and the presence of associative thickeners. In formulations thickened with hydrophobically modified ethoxylated urethane polymers, the rheology modifier can compete with the defoamer at the air/water interface and stabilize microfoam even when macrofoam has collapsed. A dosage of 0.2% by total formulation mass may provide acceptable air release after 15 min high-speed disperser mixing at 5,000 rpm, but the same dosage can fail in a low-shear roller-applied formulation because air bubbles become trapped in the film after application. To detect microfoam-induced haze, the sparge test of ASTM E2407-04 is combined with drawdown application and 20° gloss measurement per ISO 2813:2014; a loss of more than 10 units from the defoamer-free control is usually assigned to surface irregularity rather than bulk opacity. In production-scale latex paint manufacture using a Cowles blade, the defoamer is split between the grind and letdown: 60% of the total dosage is charged before high-speed pigment dispersion and 40% after letdown. This split addition prevents the foam generated during pigment wetting from entraining air into the final formulation and avoids exposing the silicone droplets to the highest shear for the entire grind cycle.
In paper coating formulations based on calcium carbonate and styrene-butadiene latex, the dosage window is narrower than in architectural coatings. Blade runnability is sensitive to defoamer-induced surface tension reduction, with fisheyes and skip coat defects appearing when the emulsion is added above 0.05% by dry coating mass. In a typical size press circulation system with a 50 L working tank and centrifugal pump recirculation at 200 L/min, hard water containing more than 200 ppm CaCO₃ can destabilize the non-ionic emulsifier layer and increase deposit formation on rolls. A circulation test with a 100 µm inline filter is therefore run before production to measure pressure rise across the filter; a rise above 0.5 bar within 2 h is considered unacceptable for continuous operation. For starch-based size press operations, the product is dosed at 0.01% to 0.03% by wet starch mass and injected upstream of the storage tank to allow low-speed mixing to distribute the silicone phase without generating additional foam.
Because RH-9208 is a water-based emulsion, freeze-thaw stability, storage shear history, and ionic load define the operational boundary. Supplier handling guidance for silicone emulsion defoamers of this class typically specifies storage between 5 °C and 40 °C and avoidance of repeated freeze-thaw cycling. Accidental freezing can produce phase separation; after thawing, the product should be re-homogenized with a low-shear propeller mixer at 300 rpm to 500 rpm for 30 min. If the median particle size after thawing exceeds 50 µm by ISO 13320:2020, the thawed batch is not recommended for applications using fine inline filters. Emulsion creaming can be accelerated by storage above 40 °C or by prolonged contact with air; tanks should be blanketed or fitted with low-speed recirculation. In waterborne adhesive compounding, dosing lines should avoid extended contact with bronze or brass fittings because trace copper ions can accelerate destabilization of the emulsifier film. The product is not recommended for anhydrous or solventborne systems, because the water carrier can create haze or phase separation when mixed with nonpolar solvents.
The mechanistic difference from mineral-oil and polyether defoamers is the low surface tension of the siloxane phase and its ability to spread rapidly across foam lamellae. This spreading pressure can be estimated from surface tension data obtained by ASTM D1331-14; silicone active materials typically measure 21–24 mN/m, mineral-oil carriers measure 30–35 mN/m, and polyether defoamers often exceed 35 mN/m in aqueous solution. The lower surface tension produces more rapid film rupture, but the same thermodynamic driving force can promote over-spreading in coatings and create craters, fisheyes, or intercoat adhesion loss. The following table summarizes comparative technical performance across the three defoamer chemistries.
| Parameter | Silicone emulsion RH-9208 | Mineral-oil defoamer | Polyether/polyol defoamer |
|---|---|---|---|
| Typical surface tension at use concentration | 21–24 mN/m (ASTM D1331-14) | 30–35 mN/m (ASTM D1331-14) | 35–42 mN/m (ASTM D1331-14) |
| Typical dosage in aqueous coatings | 0.05–0.5% by total mass | 0.1–1.0% by total mass | 0.2–2.0% by total mass |
| Foam rupture mechanism | Spreading and hydrophobic silica dewetting of lamellae | Oil droplet spreading with solid particle dewetting | Reduced surface elasticity and lamella drainage |
| Compatibility risk | Cratering and gloss reduction above 0.5% | Oil exudation, yellowing, water sensitivity | Lower knockdown with high-surfactant loads |
| Water sensitivity | Water carrier, suited to aqueous systems | Hydrophobic carrier may cause film defects | Generally water-compatible but may raise VOC |
When selecting RH-9208 over a mineral-oil defoamer, the formulator should evaluate not only foam knockdown but also gloss retention and intercoat adhesion. In a waterborne acrylic clearcoat, a split addition of 0.1% RH-9208 can preserve 20° gloss within 5 units of the defoamer-free control, while overdosing above 0.3% can create cratering that is difficult to distinguish from substrate contamination. For high-temperature aqueous processes, polyether defoamers may lose activity above 60 °C, whereas the silicone active component continues to function at process temperatures up to 90 °C in many aqueous systems, although specific data for this model at continuous high-temperature operation is limited. Compared with a 100% active silicone fluid, RH-9208 can be incorporated without high-shear pre-emulsification, but the active content is lower, so it may require higher wet dosage to equal the active dosage of a 100% silicone concentrate. If the active content is 20%, a dosage of 0.5% is required to deliver the same 0.1% active silicone. In clear polyether siloxane molecular defoamers, the absence of hydrophobic silica improves clarity but often reduces knockdown; RH-9208 contains dispersed silica and can generate haze if filter clarity is critical.
Regulatory clearance must be verified before the product is used in food-contact, potable-water, or pharmaceutical process streams. The dimethylpolysiloxane component may fall under 21 CFR 173.340 when used as a defoaming agent in specified food-processing applications, but the complete emulsion including emulsifier and preservative must be reviewed against the relevant migration limits and good manufacturing practice requirements. Under REACH Regulation EC 1907/2006, the user must confirm registration status and any Annex XVII restrictions; under EU Regulation 528/2012, the preservative package may be classified as a biocidal active substance if used at concentrations that trigger treated-article or biocidal product obligations. The water carrier does not contribute to volatile organic content under EU Directive 2004/42/EC; however, a product-specific VOC test should be performed by the formulator using the applicable method for the target coating category, such as ISO 11890-2:2020.
For metalworking fluid concentrates, RH-9208 is typically added at 0.05% to 0.2% by mass before emulsification into water. The diluted fluid at 5% concentration is then evaluated in a high-speed recirculation test using a 10 L sump and a gear pump at 2.5 bar back pressure; foam height is recorded after 30 min circulation. Direct addition to the diluted sump without pre-dilution can produce local high concentration and destabilize the metalworking fluid emulsion. In wastewater aeration basins, dosing is site-specific and usually falls between 2 ppm and 20 ppm by volume; the product is injected into the basin return channel or upstream of the aeration zone to break foam with minimum impact on dissolved oxygen transfer. Published data for this exact model in full-scale wastewater operation is limited; pilot testing with a portable sparge apparatus is recommended.
Dedicated to excellence in chemistry — serving industries worldwide with integrity and innovation.
