| HS Code | 636427 |
| Product Name | Silicone Oil Rhsoft 158 |
| Chemical Type | Amino-functional polydimethylsiloxane silicone oil |
| Appearance | Clear, colorless to pale yellow liquid |
| Viscosity At 25 C | 1,000–2,000 mPa·s |
| Specific Gravity At 25 C | 0.97–0.99 |
| Refractive Index At 25 C | 1.403–1.407 |
| Flash Point | >100 °C |
| Active Content | 100% |
| Volatile Content | ≤1% |
| Water Solubility | Insoluble |
| Organic Solvent Solubility | Soluble in common organic solvents |
| Ionic Character | Weakly cationic |
| Ph As Supplied | Approximately 7 |
| Storage Temperature | 5–35 °C |
| Shelf Life | 12 months in unopened container |
As an accredited Silicone Oil Rhsoft 158 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Silicone Oil Rhsoft 158 packaging: 25 kg high-density polyethylene drum, securely sealed with chemical-resistant liner and clear identification labels. |
| Container Loading (20′ FCL) | Container Loading (20′ FCL): Silicone Oil Rhsoft 158 is packed and secured in a 20-foot full container load for shipment. |
| Shipping | Silicone Oil Rhsoft 158 ships in original, sealed drums or IBCs with proper labels and SDS. Store and transport cool, dry, and ventilated, avoiding extremes, contamination, and container damage. Use standard PPE and confirm UN/transport classification, packaging, and documentation against the current SDS and local regulations before shipment. |
| Storage | Store Silicone Oil Rhsoft 158 indoors in a cool, dry, well-ventilated area away from direct sunlight, heat, ignition sources, strong oxidizers, acids, and bases. Keep containers tightly closed, clearly labeled, upright, and free from moisture or contamination. Use secondary containment to prevent spills. Avoid extreme temperatures and freezing; maintain recommended storage conditions and inspect containers regularly. |
| Shelf Life | Silicone Oil Rhsoft 158 has a typical shelf life of 24 months from manufacture when stored unopened under recommended conditions. |
Rhsoft 158 is handled in textile wet processing as a silicone oil base for pad-dry-cure finishing of cotton, viscose, and cotton-polyester knitted and woven goods. The working bath is prepared with demineralized water at a product concentration of 8 g/L to 15 g/L. Acetic acid at 0.2 g/L to 0.5 g/L adjusts the bath to pH 5.0 to 5.5. A pad mangle applies the bath at 65% to 80% wet pick-up. Wet fabric is dried at 120°C for 90 seconds and cured at 165°C for 60 seconds. The cure step fixes the silicone film to the fibre surface. The pH window is narrow. At pH 4.5, the softener droplets develop excessive cationic charge density. This creates an uneven, patchy film on the fibre. At pH 6.5, the emulsion loses colloidal stability. Visible oil spots appear on dark dyed goods. Automatic pH correction on the pad trough reduces handle variation during an eight-hour shift. Surface friction is measured by Kawabata KES-SE surface roughness. A mean deviation of 0.25 µm to 0.35 µm indicates reduced surface friction without macroscopic oil deposition. Wet crocking is tested according to AATCC TM8. A grade below 4 suggests excessive surface lubricant or incomplete cure. Whiteness retention is tested by AATCC TM110. A ΔE CIE shift above 1.5 after 30 days at 50°C indicates amine-related yellowing. Seam slippage is measured according to ISO 13936-2. High film thickness can reduce inter-fibre friction below the level required for seam security in lightweight shirting. The bath must not be mixed with concentrated anionic optical brighteners. Such mixtures form hydrophobic aggregates that deposit on pad rollers and scratch the fabric surface. Demineralized water is preferred because calcium and magnesium ions bridge siloxane droplets. Published data for this specific configuration is limited; the processing thresholds derive from industrial practice for aminofunctional siloxane oils of comparable activity.
For external mold release, Rhsoft 158 is diluted with an aliphatic or aromatic hydrocarbon solvent to 1 wt% to 3 wt% silicone active. Application to steel or aluminum cavities is performed by manual wipe, air-assisted spray, or robotic misting. Solvent flash-off leaves a low surface energy film. The film depresses cavity surface energy to 22 mN/m to 25 mN/m when measured with DIN 55660-2 test liquids. This is the direct cause of post-mold adhesion failure. Urethane and polyester coating resins generally require a substrate surface energy above 30 mN/m for wetting. Post-mold painting of unsaturated polyester or epoxy parts therefore fails unless the residue is removed. Removal uses solvent wiping, alkaline washing, or low-pressure plasma treatment. In polypropylene injection molding, a mold temperature of 40°C to 60°C and a clamping force of 1,500 kN permit lower ejection force. Deep ribs and textured SPI D-2 surfaces show early sticking because the silicone film is consumed unevenly. Reapplication every 20 to 50 shots is common for external release agents. Hot runner gates accumulate volatile low-molecular-weight cyclic siloxanes. This causes plate-out on cavity surfaces and may block mold venting. The use of low-volatile silicone oil grades reduces the deposit rate. The oil should not be used in cleanroom medical device molding where silicone migration requires extraction testing under ISO 10993-1 biological evaluation. The mold release layer also prevents in-mold labeling adhesion. Label adhesion is tested by ISO 2409 cross-cut after molding; a rating worse than Gt 1 indicates excessive release residue at the label interface.
Silicone defoamer compounding with Rhsoft 158 as the oil phase is built by loading hydrophobic fumed silica at 4 wt% to 8 wt% relative to oil. The silica-oil mixture is processed in a rotor-stator mixer at 3,000 rpm for 30 minutes at 140°C to 160°C. Shear and temperature build the dispersed silica network responsible for bubble film rupture. The resulting compound is then emulsified with a nonionic alkoxylate surfactant package. In pulping black liquor, cooling tower circulating water, and jet dyeing machines, the emulsion is dosed at 0.1 wt% to 0.3 wt% active silicone. Dynamic foam height in a bubble column is reduced by 60% to 80% within 30 seconds when evaluated by ASTM E2407. Overdosing above 0.5 wt% active silicone in a closed cooling loop can cause oil carryover. Carryover deposits on heat exchanger tubes lower the overall heat transfer coefficient. In polyester jet dyeing at 130°C, residual defoamer can redeposit on fabric and cause dye resist spots. A laboratory circulation rig should be used to titrate the minimum effective dose before full-scale injection. Accelerated storage at 40°C for 14 days must not show creaming or visible oil droplets. The compound should be stored in stainless steel or polyethylene. Copper and brass fittings must be avoided because copper ions catalyse silicone gelation.
In tenter frame chains and oven conveyor pins, Rhsoft 158 is metered directly into the pin and bush interface at operating temperatures between 180°C and 230°C. The oil forms a boundary film between the steel pin and the sintered bronze bush. Chain stretch is controlled because the coefficient of friction in the link is reduced. Viscosity at 40°C is measured by ASTM D445. Viscosity index is calculated by ASTM D2270. A polydimethylsiloxane oil of this type retains a viscosity index above 380. At 250°C, thermal oxidation of the methyl groups begins. The oxidation pathway converts the silicone oil to silica-like deposits inside the chain link. The deposit increases friction and accelerates pin wear. For ovens operating above 250°C, a phenyl-modified silicone or a solid lubricant dispersion is required. Metering uses a positive-displacement pump with a needle valve. A dosing rate of 0.5 mL/h per chain link row is maintained. Low ambient humidity increases static charge on the chain. Static discharge can ignite solvent vapours in adjacent finishing lines. The chain and the dosing unit must be earthed. Rhsoft 158 should not be mixed with lithium soap greases in the same tensioning unit. The two lubricant chemistries can separate and leave unprotected metal at the contact zone.
In EPDM and EPDM-grafted polyolefin extrusion, addition of Rhsoft 158 at 0.5 phr to 2.0 phr functions as an internal lubricant. The oil is added during the filler dispersion stage. Early addition reduces compound Mooney viscosity by 3 to 8 ML units when retested under ISO 289-1:2015. The additive migrates to the screw root and die land surfaces. Extrudate surface smoothness is rated by ASTM D2230. A rating of A10 to A8 indicates smooth surfaces with minimal melt fracture. Addition of the oil during the final curatives stage is not recommended. The silicone film can delay incorporation of sulfur and accelerators. Vulcanizate tensile properties are measured by ASTM D412-16. Compression set is measured by ISO 815-1:2019. At silicone oil levels above 2 phr, crosslink density can decrease because the additive dilutes the polymer matrix and migrates to filler interfaces. Filler type alters the threshold. Published data for the specific Rhsoft 158 and EPDM grade combination is limited. Formulators should therefore run a rheometer curve under ISO 6502 for each filled compound. The oil also reduces die drool in talc-filled polyolefin extrusion. At die head temperatures below 190°C, the oil does not generate visible fumes. Above 230°C, local extraction at the die is required because volatile siloxane cyclics may collect on cold tooling surfaces.
Rhsoft 158 is incorporated into solvent-borne alkyd and acrylic topcoats at 0.05 wt% to 0.3 wt% based on total liquid paint. The additive migrates to the coating-air interface during solvent evaporation. Surface enrichment reduces the slip coefficient in inclined-plane tests. Slip is measured by DIN 51130. Mar resistance is measured by ISO 1518-1. A drop in surface energy from 38 mN/m to 24 mN/m is measured by DIN 55660-2. Recoat adhesion is assessed by ISO 2409 cross-cut. At 0.3 wt%, the cross-cut rating may fall from Gt 0 to Gt 3 if the surface is not sanded or solvent-wiped. The additive is therefore limited to final topcoats where recoatability is not required. Primer intercoat adhesion is reduced. On plastic substrates requiring Gt 0 adhesion, the concentration should remain below 0.1 wt%. Silicone-free slip additives are preferred where a second coat is applied after service. Spray booths handling silicone-containing coatings must be isolated from automotive clearcoat lines. Airborne silicone mist can contaminate adjacent parts and cause cratering. The coating should not be applied over uncured amine-epoxy primers because trace amines accelerate silicone oil diffusion to the interface and weaken intercoat adhesion.
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Silicone Oil Rhsoft 158 is supplied as a linear trimethylsilyl-terminated polydimethylsiloxane fluid. The product designation is associated with a nominal kinematic viscosity of 158 mm²/s at 25 °C, although the supplier certificate of analysis remains the controlling document for each production lot. The fluid belongs to the nonpolar dimethylsilicone oil class, which exhibits a relatively flat viscosity-temperature coefficient, low surface tension, and general chemical inertness under neutral and dry conditions. Typical applications include internal lubrication in polymer melts, release-agent formulations, damper fluids, high-temperature heat-transfer media, and non-reactive viscosity adjustment in silicone sealants. Published data for this specific configuration is limited; therefore, the numerical values that follow are drawn from typical ranges for linear dimethylsilicone fluids of equivalent nominal viscosity and should not be read as a certificate of analysis. The polymer is generally identified by CAS 63148-62-9. Where food-contact use is contemplated, compliance with 21 CFR 178.3570 or an equivalent regulatory reference must be confirmed against the specific lot and end-use conditions.
Where lot-level certification is not available, the following table provides representative property data for linear polydimethylsiloxane fluids having a nominal midpoint viscosity near 158 mm²/s. These values are useful for first-pass formulation and equipment selection but are not a substitute for mill certificates. Kinematic viscosity is determined by capillary viscometry under ASTM D445-21 or ISO 3104:2020, and density is measured by oscillating U-tube densitometry under ASTM D4052-22. Refractive index is commonly reported at the sodium D line at 25 °C and is influenced by low-molecular-weight cyclic siloxane content. Volatile content is a batch-sensitive property because depolymerization during high-temperature finishing can leave measurable quantities of octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane.
| Property | Typical value | Reference test method |
|---|---|---|
| Appearance | Clear, colourless liquid | Visual inspection |
| Kinematic viscosity at 25 °C | 158 mm²/s with common lot tolerance ±5 % | ASTM D445-21 / ISO 3104:2020 |
| Density at 25 °C | 0.970 g/cm³ | ASTM D4052-22 |
| Refractive index nD25 | 1.403 | ASTM D1218 / DIN 51423-1:2010 |
| Flash point, Cleveland open cup | >300 °C | ASTM D92-18 / ISO 2592:2017 |
| Pour point | -50 °C | ASTM D97-17a / ISO 3016:2019 |
| Volatile content, 24 h at 150 °C | ≤0.3 wt% | Supplier internal method / DIN 53249:1995 |
| Surface tension at 25 °C | 21.0 mN/m | ISO 304:1985 Wilhelmy plate |
| Thermal conductivity at 25 °C | 0.16 W/m·K | Transient hot-wire method |
The precision of ASTM D445-21 for homogeneous transparent liquids can be near 0.26 % repeatability, while inter-laboratory reproducibility may exceed 1.5 %. Batch-to-batch variation in refractive index is typically within ±0.001. However, residual catalyst residues, low-molecular-weight cyclic siloxanes, and moisture ingress can shift viscosity and volatile content without changing visual appearance. Therefore, incoming inspection should include at least viscosity, moisture, and volatile content when Rhsoft 158 is used in closed-loop dosing systems, because low-level gels can accumulate on filter elements and cause gravimetric feeder drift.
In high-shear twin-screw compounding of glass-fiber-reinforced polyamide 66, linear polydimethylsiloxane fluids are introduced at 0.2–0.5 wt% by liquid injection or gravimetric feeder to reduce melt viscosity, screw torque, and die pressure. Published data for Rhsoft 158 under this exact configuration is limited, but the mechanism of internal lubrication is governed by migration of the nonpolar silicone phase to the polymer-metal interface. On co-rotating twin-screw extruders with L/D ratios between 40:1 and 48:1 and barrel temperatures from 285 °C to 300 °C, silicone oil addition can lower specific energy input in polyamide systems. Above 1.5 wt%, screw slip may occur in partially filled zones, reducing distributive mixing and producing surface defects in pelletized feedstock. For moisture-sensitive resins, drying to <0.02 % residual moisture is required before high-shear processing to avoid hydrolysis-induced molecular weight loss, independent of silicone oil use.
In two-roll mill processing of high-consistency silicone rubber, addition of 1.0–2.0 phr linear polydimethylsiloxane fluid can reduce mill sticking and improve filler incorporation. In molded articles, excess free silicone oil can bloom to the surface, lowering durometer and increasing compression set after aging under ASTM D395-21 or ISO 815-1:2019. The addition level is therefore bounded by post-cure extractable content and by Shore A hardness retention after 24 h at 200 °C. Avoid combination with amine-based processing aids and strong Lewis acid catalysts because these can catalyze siloxane bond cleavage at temperatures above 150 °C. In tin-catalyzed condensation-cure systems, Rhsoft 158 is not to be used as a reactive diluent without preliminary stability testing, because moisture plus residual tin catalyst can accelerate depolymerization and produce tacky low-molecular-weight fractions.
For mold release, a 1–3 wt% dilution in odorless mineral spirits or a water-based emulsion is applied to tool surfaces maintained between 120 °C and 180 °C by airless spray or flood-and-wipe methods. A thin visible film of 0.1–0.5 µm is generally sufficient to reduce part ejection force in polyurethane and epoxy casting. Thicker deposits increase the risk of transfer to painted surfaces and must be removed with alkaline aqueous cleaners before bonding or coating. Tool temperatures above 200 °C accelerate oxidative degradation of dimethylsilicone films, producing silica-like deposits that adhere to ejector pins and vent grooves. In such cases, periodic cleaning with 5–10 wt% sodium hydroxide solution at 60 °C is used, followed by neutralization with dilute acetic acid.
In ambient-cure sealant formulations, a linear dimethylsilicone fluid of this viscosity grade can function as a plasticizer and viscosity modifier in oxime- or alkoxy-cure RTV systems. The addition range of 5–15 wt% is typical in filled systems, but migration of the nonreactive silicone fluid can reduce lap shear strength and increase dirt pickup. Mechanical boundaries are established by ISO 8339:2005 or ASTM C1135-21. Because Rhsoft 158 is a non-reactive diluent, it does not enter the crosslinked network; extraction in toluene after vulcanization should be performed to quantify free silicone content. In damping applications, the viscosity-controlled resistance to flow provides reproducible shear force, but sustained cyclic loading above 100 Hz may generate heat and reduce damping performance if the fluid is not housed in a heat-dissipating chamber.
Where Rhsoft 158 is compared with other dimethylsilicone oils, the nominal viscosity controls handling, volatility, and surface coverage. A 50 mm²/s dimethyl fluid has a lower flash point and higher volatile content, which can be advantageous for spray atomization but a limitation in long-term high-temperature aging. A 1,000 mm²/s fluid provides lower volatility but greater pump resistance and slower air release in compounded rubber. High-viscosity grades can produce surface tack if not adequately dispersed. Phenyl-modified silicone oils exhibit higher refractive index and superior low-temperature flow, but cost and UV yellowing tendency limit them to optics and electronics applications. Amino-functional silicone oils offer adhesion and softness, but can cause yellowing and are incompatible with some platinum-cured silicone systems. Rhsoft 158, as a non-functional dimethyl fluid, is generally neutral in platinum-catalyzed addition-cure systems, provided residual water is controlled. Alkyl-modified and polyether-modified silicone oils provide organic compatibility and emulsification; they are selected when the fluid must dissolve in oils or water, and they generally exhibit higher coefficients of friction than linear polydimethylsiloxane.
| Fluid type | Nominal viscosity at 25 °C | Relative volatility | Refractive index nD25 | Primary limiting difference |
|---|---|---|---|---|
| Rhsoft 158 dimethylsilicone | 158 mm²/s | Moderate | 1.403 | Nonpolar; potential mold surface buildup above 200 °C |
| Low-viscosity dimethylsilicone | 50 mm²/s | Higher | 1.402 | Evaporative loss above 120 °C |
| High-viscosity dimethylsilicone | 1,000 mm²/s | Lower | 1.404 | Higher pump viscosity; slower air release |
| Phenyl-modified silicone oil | 100–500 mm²/s | Low to moderate | >1.50 | Higher cost; UV yellowing potential |
| Amino-functional silicone oil | 100–300 mm²/s | Moderate | 1.405–1.410 | Reactivity with acidic catalysts; yellowing |
| Polyether-modified silicone | 100–500 mm²/s | Moderate | 1.440–1.450 | Water dispersible; higher surface tension |
Selection of Rhsoft 158 over a functionalized silicone therefore depends on whether a non-reactive, non-emulsifying dimethyl fluid is required, whether the process temperature remains below the oxidative degradation threshold, and whether the end use can tolerate migration of the free silicone phase to the surface. In reactive polymer systems, the absence of silanol, vinyl, or amino groups allows use as an inert processing aid, but this same chemical inertness means the fluid cannot be anchored into the polymer network and will remain extractable in nonpolar solvents.
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