| HS Code | 590618 |
| Chemical Type | methyl-terminated branched hydrogen-containing polysiloxane |
| Appearance | colorless to pale yellow transparent liquid |
| Odor | mild characteristic odor |
| Viscosity At 25 C | 30-100 mPa·s |
| Hydrogen Content | 0.60-0.90 wt% |
| Density At 25 C | 0.95-1.00 g/cm³ |
| Refractive Index At 25 C | 1.400-1.410 |
| Flash Point | ≥100 °C |
| Volatile Content | ≤2.0 wt% |
| Hydride Equivalent Weight | 112-168 g/eq |
| Terminal Group | methyl |
| Functional Group | Si-H |
| Branching Structure | branched siloxane backbone |
| Solubility | soluble in nonpolar organic solvents; insoluble in water |
| Ionic Character | nonionic |
As an accredited Methyl Terminated Hydrogen Branched Silicone Oil RH-H57 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 200 kg securely sealed steel drums, clearly labeled for safe industrial transport and storage. |
| Container Loading (20′ FCL) | Loaded in a 20-foot FCL container, Methyl Terminated Hydrogen Branched Silicone Oil RH-H57 is packed securely for safe ocean transport. |
| Shipping | Shipping description: Methyl Terminated Hydrogen Branched Silicone Oil RH-H57; not regulated as dangerous goods under DOT/IMDG/IATA (no UN number). Ship in tightly closed, moisture-resistant containers at ambient temperature, protected from water, acids, bases, and heat. Follow the SDS and local transport rules. |
| Storage | Store in a cool, dry, well-ventilated area away from heat, sparks, open flames, and direct sunlight. Keep containers tightly closed when not in use and protect from moisture, acids, alkalis, and oxidizing agents. Avoid prolonged storage above recommended temperatures. Use compatible containers and ground/bond during transfer to prevent static ignition. Maintain good housekeeping and emergency spill containment. |
| Shelf Life | Shelf life: 12 months from manufacture date when stored in the original, unopened container in a cool, dry place. |
In addition-cure liquid silicone rubber compounding, RH-H57 functions as a hydrogen donor that reacts with vinyl-functional polysiloxane in the presence of a platinum catalyst. The branched methyl-terminated architecture leaves chain termini unreactive while pendant Si-H groups participate in hydrosilylation, which reduces chain-end network defects and permits higher crosslink density at equivalent viscosity. In LSR dosing systems using a two-component static mixer feeding an injection molding machine, RH-H57 is pre-blended into the vinyl base at 0.8–2.5 phr, with final loading adjusted until the molar ratio of Si-H to Si-Vi falls within 1.2:1–2.0:1. Deviation below 1.1:1 produces under-cured surfaces and high compression set; deviation above 2.5:1 can generate hydrogen from residual Si-H and cause porosity in thick sections. Molding is performed at 120–180°C with a hold time of 20–90 s depending on part mass and mold temperature distribution; after demolding, medical components are post-cured at 200°C for 4 h to reduce volatile siloxane residues. Compliance for finished medical parts is evaluated under ISO 10993-1:2018 and ISO 10993-5:2009, with repeated-use rubber articles falling under FDA 21 CFR 177.2600. For electronic sealing components, long-term mechanical stability is assessed per ISO 37:2017 tensile properties and ISO 815-1:2019 compression set. Production equipment includes LSR-specific injection molding machines with static mixers, vacuum degassing chambers operating below 10 mbar, and closed-loop temperature-controlled molds. Finished terminal products include respiratory mask seals, syringe plunger tips, baby bottle nipples, automotive connector micro-seals, and cable grommets. Operational boundaries include the known sensitivity of platinum catalysts to amine-containing mold release agents, sulfur compounds, and organotin stabilizers; such materials must be eliminated from the line or purged before introducing RH-H57-containing formulations.
A solventless thermal release coating line running at 300–800 m/min imposes a narrow cure window, and RH-H57 is metered into the coating bath at 2–8 wt% of the total formulation to establish an Si-H/Si-Vi molar ratio of 1.3:1–2.5:1. The branched structure provides multiple hydrogen sites per molecule, which increases crosslink density without increasing bath viscosity to levels that would destabilize a 5-roll offset gravure or multi-roll coating head. Coat weight is controlled between 0.8–1.5 g/m², and the web passes through a three-zone oven with zone temperatures of 100°C, 140°C, and 160–180°C for a total dwell time of 5–15 s. Release performance is measured according to FINAT FTM 3 and FTM 4, with target peel forces typically 5–300 cN/25 mm depending on adhesive type and coat weight. Compliance for food contact applications requires conformity to FDA 21 CFR 175.320 and EU 1935/2004; the absence of heavy metals is verified under RoHS 2011/65/EU. PET films require corona pre-treatment to 38–42 mN/m surface energy; insufficient treatment produces skip-coat defects. Terminal finished products include glassine release liners for pressure-sensitive adhesive labels, PET release films for die-cut tapes, and in-mold label release films. The main processing conflict is catalyst poisoning from substrate-borne amines or sulfur-containing primers; when converting paper substrates with unknown pre-coatings, a primer or additional platinum catalyst spike may be required.
On a heated high-speed mixer or ploughshare mixer, RH-H57 is sprayed or metered onto fumed silica, precipitated silica, calcium carbonate, or magnesium hydroxide at 0.5–2.0 wt% of filler mass. The Si-H groups react with surface hydroxyls in a condensation reaction that evolves hydrogen; therefore the mixer must operate under an inert gas purge and the fill level is kept below 70% of vessel volume to prevent flammable gas accumulation. Process temperature is maintained at 80–140°C for 60–120 min, and mixing speed is set between 700–1,400 rpm depending on vessel diameter. Batch-to-batch variance is most commonly caused by residual moisture above 0.5% in the filler, which consumes Si-H before surface hydroxyls can react; a pre-dry step at 120–150°C for 2–4 h is required when relative humidity exceeds 60% in the plant environment. Compliance is evaluated under REACH (EC) No 1907/2006 and RoHS 2011/65/EU; for fillers intended for indirect food contact, migration limits are checked against FDA 21 CFR 175.300. Hydrophobicity is measured by methanol wetting tests or advancing contact angle under ASTM D7334-08(2022). Terminal products include hydrophobic fumed silica for silicone sealants, cosmetics, cable compounds, and anti-settling additives; treated magnesium hydroxide is used in low-smoke halogen-free cable compounds where moisture uptake must remain below 0.3%. A key operational boundary is that complete surface coverage may not be achieved below 0.5 wt% on high-surface-area fumed silica above 200 m²/g BET, while addition above 2.0 wt% can leave free hydrogen silicone oil that affects downstream bond strength.
Pad-dry-cure systems in continuous textile finishing employ RH-H57 as a water-repellent finish after emulsification with a nonionic emulsifier at 5–20 g/L working concentration. The fabric is passed through a padding mangle with 60–80% wet pickup, then dried and cured on a stenter frame at 150–170°C for 60–120 s. A branched hydrogen silicone oil provides a silicon-based hydrophobic film without relying on perfluorinated side chains; however, the finish is usually combined with a metal catalyst or an amino-functional silicone to improve wash fastness, because a standalone low-molecular-weight Si-H film has limited durability under repeated mechanical laundering. Compliance is verified against Oeko-Tex Standard 100 Annex 4 limits, ZDHC MRSL V3.1, and REACH (EC) No 1907/2006. Water repellency is measured using AATCC 22-2017 spray test or ISO 4920:2012, with water/alcohol resistance determined by AATCC 193-2018 for technical outerwear. A process conflict arises when the pad bath pH falls below 4; acidic conditions can destabilize the emulsion and produce deposition on pad rolls, so buffering to 5–6 is recommended. Terminal finished products include outdoor jackets, tent fabric, awning cloth, and automotive interior technical textiles.
| Standard / Designation | Test or Scope | Application to RH-H57 Finish |
|---|---|---|
| Oeko-Tex Standard 100 Annex 4 | Residual substance limits | Finished fabric safety for skin contact |
| ZDHC MRSL V3.1 | Prohibited substances in chemical formulations | Input formulation conformity |
| AATCC 22-2017 | Spray rating | Initial water repellency after stenter cure |
| ISO 4920:2012 | Resistance to surface wetting | Comparative fabric spray performance |
| AATCC 193-2018 | Water/alcohol solution repellency | Technical outerwear durability grading |
Semi-permanent release agents generate mold build-up on high-temperature rubber molding lines; RH-H57 is formulated into a water-dilutable emulsion at 1:50–1:200 dilution and applied by air-assisted or electrostatic spray to mold surfaces at 150–200°C. The active silicone oil concentration in the ready-to-use spray is 0.5–2.0 wt%. Hydrogen functional groups crosslink on the hot metal surface to form a thin release film, and repeated cycles create a conditioned mold layer that reduces sticking in compression, transfer, and injection molding of EPDM, NBR, and HNBR compounds. Mold release performance is evaluated by the number of release cycles between reapplication, with typical intervals between 20 and 50 demoldings depending on compound sulfur level and mold geometry. Compliance for food-contact rubber goods is assessed under FDA 21 CFR 177.2600 and EU 1935/2004 where applicable; industrial parts are checked against REACH (EC) No 1907/2006. The main operational boundary is that sulfur-containing rubber compounds can interfere with Si-H crosslinking; when high-sulfur compounds are run, the mold must be cleaned and re-seasoned more frequently. Finished terminal products include O-rings, gaskets, sealing profiles, and automotive rubber mounts.
Compounding a defoamer starts with hydrophobic silica made from RH-H57 or with direct addition of RH-H57 into a silicone oil carrier; the mixture is homogenized in a kneader at 80–120°C for 1–3 h until the Si-H groups react with silica surface silanols and release hydrogen. The resulting silicone compound is then emulsified with nonionic surfactants at 50–70°C, producing a water-dilutable defoamer. In final metalworking fluid or paper machine whitewater formulations, the active defoamer addition is 0.05–0.5 wt%. Foam collapse and persistence are evaluated by ASTM E2407 or internal sparge tests over 24 h in recirculating metalworking fluid at 40–60°C. For paper machine whitewater, compliance is controlled under FDA 21 CFR 176.170 and FDA 21 CFR 173.340 where the defoamer contacts food-grade paper and paperboard; industrial formulations are checked under REACH (EC) No 1907/2006. Terminal finished products include soluble oil metalworking fluid defoamers, paper machine whitewater defoamers, and wastewater treatment antifoams. The main process conflict is that shear above 1,000 rpm during emulsification can destabilize the silicone compound and reduce defoaming persistence; therefore the compound is added slowly under controlled rotor-stator conditions.
Vacuum degassing is the controlling step when RH-H57 is incorporated into two-part LED encapsulant and power module potting formulations. The component is blended into Part A at 1–5 wt% based on the vinyl silicone matrix, with the Si-H/Si-Vi molar ratio adjusted to 1.1:1–1.6:1 to achieve visible-light transmittance and a Shore A hardness between 40–70 as measured by ASTM D2240-15(2021). The mixed encapsulant is degassed under 0.5–1.0 kPa for 10–30 min, dispensed into LED module housings, and cured in a two-step program of 100°C for 1 h followed by 150°C for 2 h. Thermal conductivity is tested according to ASTM D5470-17, and flammability is classified under UL 94 with V-0 requirements for optical encapsulants. Electronic insulating properties are evaluated by IEC 60243-1:2013 dielectric strength. Compliance with RoHS 2011/65/EU and REACH (EC) No 1907/2006 is declared. Terminal finished products include LED strip encapsulant, COB LED domes, power module potting, and optical sensor encapsulation. A key limitation is that residual Si-H can reduce adhesion to silver-plated lead frames if the Si-H/Si-Vi ratio exceeds 1.8:1; therefore ratio control and post-cure are critical.
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Methyl Terminated Hydrogen Branched Silicone Oil RH-H57 is supplied as a low-viscosity, clear organosilicon fluid in which the polysiloxane backbone carries a controlled density of hydride-functional siloxane units and the chain termini are occupied by methyl groups. The grade designation identifies a branched hydrogen silicone oil rather than a conventional linear methyl hydrogen silicone oil. In RH-H57, the reactive silicon-hydrogen sites are distributed along the main chain and at branch junctions, while methyl termination removes most condensation-active silanol end groups. This molecular configuration defines the principal application behavior of the product: it functions as a hydride donor, crosslinker, surface hydrophobe, and reactive intermediate without introducing terminal hydroxyl condensation kinetics. The product is typically handled as a reactive diluent or crosslinking co-reactant in addition-cure silicone formulations, textile and release-coating baths, and silicone-modified resin syntheses.
At the molecular level, RH-H57 is characterized by a poly(methylhydrosiloxane-co-dimethylsiloxane) structure with a deliberate fraction of trifunctional and tetrafunctional siloxane branch sites. The hydride equivalent mass is the controlling parameter for formulation stoichiometry, not the total molecular weight or the nominal viscosity alone. The branched architecture increases the average number of silicon-hydrogen groups per molecule at a given kinematic viscosity compared with a linear methyl hydrogen silicone oil of similar chain length. This has direct consequences for crosslink density in addition-cure elastomers and for the continuity of the hydrophobic film formed on mineral, metal, and glass substrates. A representative lot-release profile for RH-H57 is summarized in Table 1; the data are indicative of a low-volatile, low-viscosity reactive fluid with a measurable hydride concentration suited to precise metering in continuous coating lines.
| Property | Test method | Representative value |
|---|---|---|
| Appearance | Visual inspection | Clear, colorless to pale yellow liquid |
| Kinematic viscosity at 25 °C | ISO 3104 / ASTM D445 | 25–40 mm²/s |
| Hydride content | Gasometric or titration method | 7.0–10.0 mmol/g as Si-H |
| Density at 25 °C | ISO 2811 | 0.98–1.02 g/cm³ |
| Refractive index at 25 °C | ISO 5661 | 1.400–1.410 |
| Volatile matter, 2 h at 105 °C | ISO 3251 | ≤1.0 wt% |
| Flash point | ISO 2719, Pensky-Martens closed cup | ≥160 °C |
The tabulated values define the material at the point of release rather than a universal specification. Users in moisture-sensitive addition-cure systems should verify the current certificate of analysis because hydride content and residual moisture can shift with batch age and storage conditions. RH-H57 is normally stored under dry inert gas and protected from strong alkali, transition metal powders, and high-humidity air. Prolonged contact with atmospheric moisture at relative humidity above 60% may produce slow hydrogen evolution and a corresponding reduction in active hydride.
The central difference is architectural. Linear methyl hydrogen silicone oil consists of a predominantly unbranched siloxane chain with pendant silicon-hydrogen groups. The hydride functionality in a linear fluid is therefore diluted by chain length and is limited by the maximum permissible hydride substitution along the polymer backbone. RH-H57 introduces branch points that elevate the number of hydride-bearing siloxane units per molecule without an equivalent increase in viscosity. This means that at equal active hydride content, a branched architecture can deliver a higher crosslink density contribution per mole of silicone oil, a property particularly relevant in addition-cure systems where the formulation is balanced on Si-H to vinyl stoichiometry.
Unlike silanol-terminated silicone fluids, the methyl-terminated structure of RH-H57 minimizes the condensation-active hydroxyl population at the chain ends. This reduces the risk of pre-gelation in moisture-sensitive formulations and improves compatibility with hydrophobic organic matrices. Compared with dimethyl silicone oil, which lacks reactive silicon-hydrogen groups, RH-H57 provides reactivity while retaining a broadly similar methylsiloxane compatibility profile. The comparative behavior is summarized in Table 2.
| Feature | RH-H57 branched hydrogen silicone oil | Linear methyl hydrogen silicone oil | Methyl-terminated dimethyl silicone oil |
|---|---|---|---|
| Backbone architecture | Branched | Linear | Linear |
| Terminal group | Methyl | Methyl | Methyl |
| Reactive Si-H | Present, pendant and branch-associated | Present, predominantly pendant | Absent |
| Functionality per molecule at equal viscosity | Higher | Moderate | Not applicable |
| Typical primary use | Crosslinker, hydrophobing agent, resin intermediate | Chain extender, crosslinker, water repellent | Diluent, lubricant, release aid |
In platinum-catalyzed addition-cure silicone elastomers, RH-H57 is metered as a silicon-hydride crosslinker at a hydride-to-vinyl molar ratio commonly maintained between 1.2:1 and 2.0:1. The branched architecture permits the formulator to reduce the mass fraction of hydride donor required to reach a target network modulus because each molecule contributes a higher average number of junction-forming sites. The cure response is therefore more sensitive to mixing accuracy than in linear methyl hydrogen silicone oil systems; an error in hydride metering can shift the network from desirably tough to brittle or leave residual unreacted vinyl groups that degrade heat aging. In compounding trials using a planetary mixer at 25 °C and subsequent coating on a continuous line, the pot life of a vinyl-functional silicone containing RH-H57 was found to be governed primarily by the platinum catalyst complex concentration and the inhibitor level, not by the initial hydride content alone. The working time can fall below 2 h at room temperature if the formulation contains no alkyne-based inhibitor, which is a processing constraint on long batch runs.
The cure temperature window is a critical threshold. Below approximately 80 °C, the addition-cure reaction slows substantially unless a highly active platinum complex is used. Above approximately 140 °C, side reactions such as dehydrogenative coupling between silicon-hydride and silanol or moisture become more significant, producing hydrogen and destabilizing the network. For RH-H57, the preferred cure zone in thin-section elastomer coatings is therefore between 100 °C and 130 °C, with the optimum usually near 120 °C for short oven dwell times. The allowed deviation is narrow in fast-cure lines because a temperature excursion of more than ±5 °C around the set point can alter gel time sufficiently to affect coating thickness and surface tack. Published data for this specific configuration is limited; the stated window is derived from process experience with branched hydride-functional silicone fluids of comparable hydride equivalent mass.
Vulcanization kinetics in RH-H57-crosslinked systems follow the expected hydrosilylation dependence on hydride-to-vinyl ratio, catalyst loading, and temperature. The branch points create a more rapidly developed elastic modulus during the early stages of cure because the branched hydride donor can form multiple crosslinks from a single molecule. This reduces the time to gel point at equivalent platinum concentration compared with a linear methyl hydrogen silicone oil of equal hydride content. However, the same dense network formation can lower elongation at break and increase Shore hardness. Mechanical testing according to ISO 37 on cast sheets of a representative addition-cure formulation showed that replacing a linear hydride donor with RH-H57 at constant Si-H to vinyl ratio shifted tensile strength upward while reducing elongation, consistent with higher crosslink density. The exact balance is formulation-specific and must be determined by gradient testing.
RH-H57 is incompatible with deliberate additions of tin carboxylate condensation catalysts or strong amines in hydrosilylation systems. Tin compounds and amines can promote side reactions of the silicon-hydride group, including hydrogen evolution and premature viscosity build. In production equipment, the material should not be mixed with filter media or piping components containing elemental copper, zinc, or iron in a finely divided form because these metals can catalyze uncontrolled dehydrogenation. Stainless steel, glass-lined, and polytetrafluoroethylene-lined equipment are generally suitable.
In surface hydrophobic treatment, RH-H57 functions by covalent attachment of siloxane segments to hydroxyl-bearing substrates such as glass, silica, alumina, and cellulose. The branched hydride density permits the formation of a crosslinked siloxane film with a lower tendency to desorb compared with a linear dimethyl silicone oil film that lacks reactive bonding sites. On fabric lines, the fluid is typically applied from an aqueous emulsion or solvent-based bath and cured at 120–150 °C. The use of a methyl-terminated branched hydride fluid reduces the quantity of residual silanol available for post-treatment secondary condensation, which in turn reduces the stiffness development sometimes observed with silanol-terminated silicone water repellents.
High-shear dispersion of RH-H57 emulsions requires attention to the sequence of addition. The oil phase should not be mixed with alkaline water at pH above 9 for prolonged periods because alkaline conditions accelerate silicon-hydride hydrolysis and hydrogen release. A more stable emulsion is obtained when the aqueous phase is adjusted to pH 6–8 and the silicone oil is added slowly under a rotor-stator mixer at moderate tip speed. In a continuous padding operation, the bath concentration is typically adjusted by refractive index or hydride titration rather than by viscosity alone because RH-H57 has a low viscosity and small concentration changes can be masked by temperature fluctuations.
Cellulosic substrates treated with RH-H57 exhibit hydrophobicity after cure as the silicon-hydride groups react with substrate hydroxyls and atmospheric moisture. The performance depends on the extent of surface coverage and on the removal of unreacted fluid by washing or solvent extraction. Residual hydride can be decomposed by a mild alkaline rinse, but this operation must be controlled because rapid hydrogen evolution can create foam in the wash bath. Published data for this specific configuration is limited outside of supplier application bulletins; users should evaluate the treated substrate by contact angle measurement and, where applicable, by the AATCC spray rating method.
In silicone-modified organic resin synthesis, RH-H57 is used as a hydride-functional siloxane intermediate. Its methyl termination permits incorporation into isocyanate-free and solventborne systems where terminal silanol groups would cause uncontrolled condensation. The branched structure provides a higher reactive site density for hydrosilylation grafting onto allyl or vinyl groups of acrylic and polyether backbones. In such syntheses, the hydride equivalent mass rather than the nominal molecular weight is the correct basis for calculating reagent stoichiometry. The reaction is carried out under dry inert gas, and the reagent should be added after the reactor has been purged to remove oxygen because oxygen can degrade platinum catalysts and produce side products.
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