| HS Code | 970232 |
| Productname | Agricultural Silicone Spreading and Penetrating Agent RH-208 |
| Chemicaltype | Polyether-modified siloxane |
| Appearance | Colorless to light yellow transparent liquid |
| Ionictype | Nonionic |
| Activecontent | ≥99% |
| Ph | 6.0-8.0 (1% aqueous solution) |
| Viscosity | 20-60 mPa·s at 25°C |
| Specificgravity | 1.00-1.05 at 25°C |
| Surfacetension | ≤21.0 mN/m (0.1% aqueous solution) |
| Watersolubility | Soluble/dispersible in water |
| Flashpoint | >100°C |
| Cloudpoint | 35-45°C (1% aqueous solution, typical) |
| Storagestability | Stable under normal storage conditions |
| Shelflife | 24 months in unopened original packaging |
| Packaging | 200 kg drum or 50 kg drum |
As an accredited Agricultural Silicone Spreading and Penetrating Agent RH-208 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | RH-208 agricultural silicone spreading/penetrating agent is supplied in 200 kg polyethylene drums and 20 kg plastic pails. |
| Container Loading (20′ FCL) | 20′ FCL container securely loaded with packaged RH-208 agricultural silicone spreading and penetrating agent for safe export shipment. |
| Shipping | `Agricultural Silicone Spreading and Penetrating Agent RH-208` is typically shipped in sealed plastic drums or IBC totes at ambient conditions. Keep containers closed, cool, dry, and protected from sunlight and freezing. Handle per the SDS; classify, label, and document according to applicable transport regulations. Avoid spills and contact. |
| Storage | Store in a cool, dry, well-ventilated place, away from direct sunlight, heat sources, and ignition. Keep containers tightly closed and upright in their original packaging. Prevent freezing and contamination by moisture, dirt, or incompatible chemicals. Store separately from food, feed, and drinking water. Ensure adequate ventilation and use secondary containment to control leaks or spills. |
| Shelf Life | Approximately 24 months when stored sealed in its original container in a cool, dry, ventilated place, away from direct sunlight. |
Agricultural Silicone Spreading and Penetrating Agent RH-208 belongs to the nonionic organosilicone surfactant class used as a tank-mix adjuvant in aqueous crop protection and foliar nutrition sprays. Published data for this specific configuration is limited; however, the operational windows below derive from the documented behavior of trisiloxane ethoxylate adjuvants with comparable wetting characteristics on waxy and hairy leaf surfaces. When diluted to 0.025%–0.1% v/v, this chemistry class typically produces equilibrium surface tension in the range of 20–23 mN/m when measured by Wilhelmy plate method according to ASTM D1331-20. Under ASTM E1519-16 terminology for agricultural tank mix adjuvants, RH-208 functions as a spreading agent and penetration modifier rather than a primary pesticide or nutrient. The product is designed for addition to spray tanks after water conditioning and after the active ingredient concentrate has dispersed. Theoretical spreading performance is not a substitute for jar tests; batch-to-batch variance in spray water hardness, pH, and active ingredient formulation type requires verification of visible homogeneity before application. The diluted spray mixture should not be stored longer than 24 h, and concentrated product should not be pre-mixed with high-pH buffers or strong acids.
| Target scenario | RH-208 use rate | Spray volume | Droplet size range | Reference standard |
|---|---|---|---|---|
| Mature citrus acaricide | 0.025–0.05% v/v | 2000–3000 L/ha | 80–150 µm VMD | ISO 25358 |
| Perennial grass herbicide | 0.05% v/v | 100–200 L/ha | 250–350 µm VMD | ISO 25358 |
| Rice sheath blight fungicide | 0.03–0.05% v/v | 300–500 L/ha | 100–200 µm VMD | ISO 25358 |
| Foliar calcium nutrition | 0.05–0.075% v/v | 500–1000 L/ha | 200–400 µm VMD | ISO 25358 |
| Tomato biofungicide | 0.025% v/v | 600–900 L/ha | 150–250 µm VMD | ISO 25358 |
| Cotton defoliation ULV | 0.05% v/v | 28–56 L/ha | 150–250 µm VMD | ISO 25358 |
On mature citrus canopies, abaxial leaf surfaces of Valencia and Navel oranges retain a dense epicuticular wax layer. Water-based sprays with conventional nonionic surfactants often form discrete droplets with contact angles above 80° on these surfaces. RH-208 is introduced at 0.025% to 0.05% v/v into a tank mix containing abamectin at 18 g a.i./ha or spirodiclofen at 240 g a.i./ha. Spray volume is maintained at 2000–3000 L/ha for mature canopy, delivered through ATR brown or ceramic hollow-cone nozzles at 1.5–2.0 MPa. The adjuvant is added after the formulation and after buffering the spray water to pH 5.5–6.5 with citric acid. Recirculation through a centrifugal pump at 120–180 L/min for 10 min is used to prevent phase separation. The resulting spray fluid remains translucent, with no visible floating silicone film. Pre-mixing RH-208 with undiluted emulsifiable concentrates is avoided because phase inversion can occur before the silicone has a chance to distribute in the aqueous phase.
Field-scale experience indicates batch-to-batch variance in waxy leaf deposition can be reduced when the mixture is checked by sessile-drop contact angle on a polished citrus leaf substitute. Contact angle below 30° at 1 s after deposition is typical for this chemistry class. If contact angle remains above 45°, the tank is agitated for an additional 5 min and a compatibility check with the emulsifiable concentrate is repeated. The use rate must not exceed 0.1% v/v on young flush growth at air temperatures above 32°C; published data for RH-208 in this configuration is limited, but the class risk of phytotoxicity increases at high concentration and low humidity. In the United States, silicone surfactants used as inert ingredients in formulated pesticide products may be covered by the tolerance exemption in 40 CFR 180.910. Tank additions are governed by the registered spray mixture label and state adjuvant registration requirements.
High-volume glyphosate applications on perennial grasses encounter antagonistic cations in hard water, where calcium and magnesium concentrations above 200 mg/L as CaCO₃ reduce glyphosate uptake by forming poorly absorbed metal complexes. A tank sequence is required: fill the induction hopper or main tank with half the final water volume, add ammonium sulfate at 8.5 lb/100 gal (1.0 kg/100 L) to condition the water, add the glyphosate isopropylamine salt at label rate, then add RH-208 at 0.05% v/v. The mixture is agitated for 5 min before the remaining water is added. Flat fan nozzles classified as droplet size VC to C per ISO 25358 are operated at 2.5–3.5 bar, producing a volume median diameter of 250–350 µm at the nozzle exit. The resulting post-emergence spray fluid is a systemic herbicide treatment for perennial grass and broadleaf weed control. Drift must be limited to wind speeds below 4 m/s and temperature below 28°C, because higher evaporation reduces the silicone-mediated spreading window. RH-208 should not be tank-mixed with glyphosate formulations already containing a high-load nonionic surfactant above 10% w/w unless a jar test confirms homogeneity after 30 min. Published data for RH-208 in this specific hard-water matrix is limited; the ammonium sulfate sequence is based on class-level cation complexation behavior.
Within the flooded paddy canopy, a microclimate develops in which rice leaf sheaths and lower culms remain wet, yet fungal pathogens such as Rhizoctonia solani establish on semi-submerged tissues. A tank mix with azoxystrobin at 125 g a.i./ha or propiconazole at 125 g a.i./ha is prepared with RH-208 at 0.03% to 0.05% v/v. Spray volume is reduced to 300–500 L/ha to avoid runoff from vertical leaves. The sprayer is a knapsack motorized mist blower with a 28 cm-diameter radial fan, and the discharge is operated at 2.0–3.0 L/min. Addition sequence is critical: the silicone adjuvant is added after a dispersible concentrate or suspension concentrate, not before, because instant surface tension depression can trap air bubbles in the siphon line. The resulting fungicide spray fluid is used within 6 h and is not stored overnight. Compatibility with paddy water is checked by measuring pH; if paddy water pH exceeds 7.5, a buffering agent is added before RH-208 to prevent hydrolysis of the silicone chain. At pH above 8.5, silicone ethoxylate adjuvants can undergo slow silicone-oxygen bond cleavage, reducing spreading performance within 24 h.
When calcium-based foliar fertilizers are combined with sulfate salts, precipitation of gypsum can obstruct nozzles and reduce spray uniformity. A spray-grade calcium nitrate solution containing 150 kg/ha equivalent calcium, mixed with magnesium sulfate at 5 kg/ha, is pre-diluted in water to below 5% total salt concentration before adding RH-208 at 0.075% v/v. The silicone adjuvant is not added to the concentrated fertilizer stock solution because high ionic strength above 10,000 mg/L may reduce its cloud point and produce a hazy two-phase system. The working solution is adjusted to pH 5.0–6.0 with dilute nitric acid or citric acid and recirculated through a diaphragm pump at 40–60 L/min for 15 min. The finished foliar nutrient spray is applied at 500–1000 L/ha using axial-fan airblast sprayers with a forward speed of 4–5 km/h. Batch-to-batch variance in the fertilizer's cation exchange capacity can shift the cloud point; a visual clarity check at ambient temperature is performed before each tank batch, and any persistent haze triggers a reduction in RH-208 to 0.05% v/v or a switch to a lower-hardness water source. REACH compliance for the adjuvant and the fertilizer remains separate under Regulation (EC) No 2003/2003 for the fertilizer and Regulation (EC) No 1907/2006 for the silicone product.
Air-assisted sprayers operating in dense tomato canopies require droplet size control because fines below 100 µm VMD drift from the target and droplets above 400 µm VMD roll off the waxy adaxial leaf surface. RH-208 at 0.025% v/v is added to a biofungicide suspension containing Bacillus subtilis QST 713 at 2.0 kg/ha. The adjuvant is added after the biological inoculant to avoid bacterial cell membrane disruption during high-shear mixing. A hydraulic air-shear nozzle with an air velocity of 18–22 m/s and liquid pressure of 2.0 bar produces a droplet spectrum of 150–250 µm VMD. Spray volume is 600–900 L/ha, and the mixture is applied within 4 h to maintain spore viability. The resulting biofungicide spray fluid is used for early blight and powdery mildew suppression. The silicone wetting agent reduces relative surface tension, increasing stream-bank retention on hairy tomato leaflets. No additional wetter is required, and non-target aquatic exposure is minimized by a droplet size class of Coarse per ISO 25358. Do not combine with copper hydroxide at pH above 7.0; alkaline copper complexes can accelerate silicone hydrolysis and reduce bacterial viability. Use rate must not exceed 0.05% v/v on tomato seedlings at temperatures above 30°C due to risk of leaf margin burn; published data for this specific configuration is limited.
Cotton harvest aid programs that rely on thidiazuron at 150 g a.i./ha plus diuron at 75 g a.i./ha are applied when 60% to 70% of bolls are open. RH-208 is added at 0.05% v/v in aerial ULV sprays with a total spray volume of 28–56 L/ha. The adjuvant is added last to the mix tank after the suspension concentrate has fully dispersed. Spray aircraft are equipped with rotary atomizers set to 150–250 µm VMD and swath width 15–18 m. The finished defoliant spray must reach the abaxial side of mature cotton leaves; silicone spreaders reduce the contact angle on hairy leaf surfaces and increase the effective contact area of each droplet. Operational limits include wind speed 2–4 m/s and temperature 20–30°C. At temperatures above 30°C and relative humidity below 30%, the spray droplet may dry before leaf absorption, reducing the penetration benefit. Do not apply RH-208 with defoliant mixes containing ethephon above pH 4.0; the elevated ethylene release can cause premature boll abscission. The adjuvant must comply with aerial application restrictions under 40 CFR Part 156 and state aerial pesticide rules.
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Agricultural Silicone Spreading and Penetrating Agent RH-208 is supplied as a 100% active polyether-modified trisiloxane copolymer liquid for post-emergence tank-mix use with water-dispersible granules, suspension concentrates, emulsifiable concentrates, and soluble liquid crop protection formulations. Manufacturer release specifications include density 1.01–1.03 g/cm³ at 25°C by ASTM D1475-13, Brookfield LV viscosity 20–40 mPa·s at 25°C at spindle 1 60 rpm, pH of 1% aqueous dispersion 5.0–7.0 by ISO 4316:1977, and water content not exceeding 0.5% by ASTM D1364-02. The equilibrium surface tension of a 0.1% aqueous dilution is reported within 20.0–22.5 mN/m at 25°C by ASTM D1331-14. The liquid is clear to slightly hazy, with pour point below 0°C. Production-scale batches are manufactured in 5,000 L stainless steel vessels with low-shear pitched-blade impellers; batch-to-batch variability in equilibrium surface tension is controlled within 0.5 mN/m at release. Localized overheating above 60°C during dilution is avoided because it accelerates polyether oxidation and siloxane rearrangement.
| Property | Test method | Typical range | Unit |
|---|---|---|---|
| Nonvolatile content | ASTM D2369-20 | 99.0–100.0 | % w/w |
| Density at 25°C | ASTM D1475-13 | 1.01–1.03 | g/cm³ |
| Viscosity at 25°C | Brookfield LV 60 rpm | 20–40 | mPa·s |
| pH 1% aqueous | ISO 4316:1977 | 5.0–7.0 | — |
| Water content | ASTM D1364-02 | ≤0.5 | % w/w |
| Equilibrium surface tension 0.1% | ASTM D1331-14 | 20.0–22.5 | mN/m |
Organosilicone spreading agents based on trisiloxane ethoxylates are subject to hydrolytic degradation once diluted into aqueous carrier. For RH-208, manufacturer handling guidance states that spray solutions should be prepared and used within 24 h; prolonged storage of diluted solution at ambient temperature can produce silanol condensation products that reduce spreading efficacy. Hydrolysis rate increases outside pH 5.0–8.0, with rapid loss of surface activity above pH 9.0 and below pH 4.0. In hard water, calcium and magnesium ions above 500 mg/L as CaCO₃ may reduce dynamic surface tension performance by competing for the air-liquid interface. Ammonium sulfate at 1–2% w/v in the same tank is generally acceptable if RH-208 is added after buffering agents and pH is rechecked. The recommended addition sequence is: fill the spray tank to half volume with carrier, add water conditioners, add crop protection product, then add RH-208 as a pre-diluted 1:10 stock solution under agitation. Recirculation should remain continuous to avoid localized high concentration in the induction bowl.
Recommended use rates fall between 0.025% and 0.1% v/v for ground boom sprayers operating at 2–5 bar and 100–300 L/ha. For aerial application, the manufacturer’s technical bulletin indicates carrier volumes of 20–50 L/ha and a rate of 0.05–0.1% v/v should not be exceeded because super-spreading films may coalesce and run off non-waxy leaf surfaces. The product is not a standalone surfactant for oil-based ultra-low-volume systems; it is formulated for water-based tank mixes. Laser diffraction measurements with a Malvern Spraytec at 0.1% addition show a reduction in median volume diameter of 10–18% relative to water alone through conventional XR flat-fan nozzles, but this effect is nozzle-dependent and should be confirmed on the application rig. Turbulence in the tank can generate foam under high shear; persistent foam measured by CIPAC MT 47.2 after 1 min is typically below 20 mL for 0.1% solutions, whereas conventional nonionic adjuvants may exceed 80 mL under identical conditions.
Compatibility with concentrated fertilizer solutions is not unlimited. Ammonium sulfate at 1–2% w/v can decrease dynamic surface tension but also increase ionic strength; RH-208 remains soluble up to 30% urea ammonium nitrate by volume under constant agitation, but phase separation may occur in hard water above 300 mg/L CaCO₃. Jar tests using 1 L graduated cylinders and CIPAC MT 23.1 are recommended before tank-mixing with micronutrient EDTA chelates, as trace iron and manganese can catalyze oxidative degradation of the polyether chain. When the carrier pH is adjusted with citric acid below 5.0 for acidifying adjuvants, RH-208 should be added last and the spray discharged within 8 h to limit hydrolysis.
RH-208 lowers dynamic surface tension to allow droplet impingement and wetting on waxy or pubescent leaf surfaces. In comparative goniometer tests on polypropylene film and wheat leaf cuticle, a 10 µL droplet of 0.1% aqueous RH-208 produces a contact angle below 5° within 30 s; the same droplet volume with a 0.1% nonylphenol ethoxylate remains above 50°. Dynamic surface tension measured by maximum bubble pressure tensiometry at 100 ms is reported at 22–24 mN/m, indicating rapid migration to freshly generated interfaces. The critical micelle concentration of trisiloxane ethoxylates is typically below 0.01% w/w, so the spreading response is nonlinear with concentration; above 0.15% v/v the wetted area can decrease due to micellar relaxation and film drainage changes. Spray impingement studies using high-speed videography at 10,000 fps show that droplet rebound from hydrophobic leaf surfaces is suppressed with RH-208 at 0.025% v/v, while rebound persists for water and many non-silicone adjuvants. The mechanism involves Marangoni-driven surfactant transport to the expanding droplet edge during the 1–5 ms impact window.
| Parameter | RH-208 | Nonylphenol ethoxylate 9 EO | Branched alcohol ethoxylate |
|---|---|---|---|
| Equilibrium surface tension, ASTM D1331-14 | 21.0 mN/m | 28.5 mN/m | 26.7 mN/m |
| Dynamic surface tension at 100 ms | 23.0 mN/m | 34.0 mN/m | 31.0 mN/m |
| Contact angle on wheat leaf after 30 s | <5° | 55° | 42° |
| Spreading diameter, 10 µL on polypropylene film | 42 mm | 8 mm | 12 mm |
| Persistent foam, CIPAC MT 47.2 1 min | 15 mL | 85 mL | 60 mL |
The principal difference between RH-208 and conventional nonionic adjuvants is the equilibrium surface tension floor. Nonylphenol ethoxylates and branched alcohol ethoxylates typically reach 26–30 mN/m at use rates, whereas the trisiloxane structure in RH-208 stabilizes 20–22 mN/m. This expands the wetted area on a hydrophobic surface by an order of magnitude. However, organosilicone adjuvants are not high-HLB oil emulsifiers; RH-208 does not provide robust emulsification for paraffinic or methylated seed oil concentrates. It should not be used as a replacement for anionic/nonionic blend adjuvants where emulsification of esterified oil carriers is required. In comparison with other silicone adjuvants, RH-208 is supplied as a 100% active product, whereas some commercial organosilicones are sold as 50–80% active solutions in propylene glycol or water. The absence of glycol co-solvent reduces viscosity buildup at low temperatures but requires exact dosing; small additions of 0.025% v/v correspond to 2.5 mL per 100 L spray volume, and direct pouring without pre-dilution can cause localized concentration spikes.
RH-208 differs from silicone polyether copolymers with longer siloxane backbones by its trisiloxane architecture, which provides higher spreading at low concentration but lower hydrolytic stability. Longer-chain silicone polyethers may be more stable in alkaline conditions but do not achieve the same low equilibrium surface tension in the 0.1% range. The selection of RH-208 is therefore justified where rapid wetting and stomatal infiltration are required and where the tank solution is used immediately; it is not the preferred adjuvant for tank mixes that must be held overnight under high pH.
When RH-208 is used as a direct replacement for a 0.25% v/v nonylphenol ethoxylate adjuvant in contact herbicide sprays targeting broadleaf weeds with waxy cuticles, the required organosilicone rate is typically lower by a factor of 2.5–5. The manufacturer recommends starting at 0.05% v/v for contact actives, and only increasing to 0.1% v/v where canopy wetting is incomplete. At higher rates, runoff and reduced deposition on strongly hydrophobic surfaces may occur because the spreading coefficient becomes negative in some droplet drying regimes. For systemic actives, the penetration enhancement of RH-208 can increase uptake velocity; this may reduce the rain-free period required after application, but it can also increase crop sensitivity under high temperature and low humidity. In test plot evaluations conducted under 35°C and 40% relative humidity, the addition of RH-208 at 0.1% to a registered pinoxaden formulation produced faster leaf penetration than a conventional nonionic adjuvant; published data for this specific formulation configuration, however, is limited. Operators should conduct strip trials before full-field tank replacement.
Nozzle selection interacts with RH-208 because super-spreading modifies droplet size distribution and sheet breakup. Air induction nozzles operating at 3 bar produce coarse droplets that may not wet easily without an organosilicone; RH-208 at 0.05% v/v restores coverage on waxy leaves without necessarily increasing driftable fines. Conversely, hollow-cone nozzles at higher pressure may produce fines that remain airborne longer; the surface tension depression at 100 ms does not eliminate all fine droplet formation. Spray drift models such as AGDISP or DRIFTSIM require measured droplet spectra for each adjuvant and nozzle combination; generic surface tension input alone is insufficient.
Penetration enhancement data generated for trisiloxane ethoxylate adjuvants indicate that 0.05% addition can increase permeation of a model systemic active through isolated tomato fruit cuticle by 1.5–2.5-fold over a water-only control in a 24 h Franz cell study at 25°C. The enhancement is temperature-dependent and may be less pronounced on stomatous abaxial leaf surfaces where stomatal infiltration contributes. The trisiloxane surfactant lowers surface tension sufficiently to promote infiltration into stomatal pores; the threshold surface tension for stomatal infiltration is described in the literature as below 25 mN/m. RH-208 at 0.05% achieves this threshold, but stomatal infiltration is also governed by droplet size, leaf surface morphology, and carrier pH. Published data for RH-208 in this specific assay configuration is limited.
Safety and regulatory compliance statements for RH-208 should be verified against the current Safety Data Sheet and local pesticide adjuvant registration. The product is intended for use as an inert adjuvant in agricultural sprays; it is not a standalone pesticide and should not be applied without a registered crop protection product. Storage stability under sealed conditions is specified by the manufacturer as 24 months from date of manufacture in original unopened containers at 5–40°C. Opened containers should be purged with dry nitrogen to minimize moisture ingress, as the trisiloxane linkage is moisture-sensitive. The product is incompatible with concentrated oxidizing agents and strong acids; mild steel and aluminum equipment should not be used for long-term storage because trace acidity can catalyze siloxane rearrangement. For application equipment, downstream cleaning with water and a nonionic detergent is sufficient after use; cross-linking residues are not expected under normal agricultural spray conditions. Environmental fate data for RH-208 as a specific commercial product are not fully published; the organosilicone class is known to hydrolyze in soil and water to silanol and polyether degradation products, but site-specific persistence depends on pH, temperature, and microbial activity.
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