| HS Code | 277730 |
| Product Name | Dual-end Hydrogen Silicone Oil RH-H6 |
| Chemical Name | α,ω-Dihydrogen polydimethylsiloxane |
| Cas Number | 70900-21-9 |
| Appearance | Colorless transparent liquid |
| Viscosity At 25 C | 5-10 mPa·s |
| Hydrogen Content | 0.15-0.20% |
| Density At 25 C | 0.95-0.98 g/cm³ |
| Refractive Index At 25 C | 1.400-1.410 |
| Flash Point | >100°C |
| Volatile Matter | ≤1.0% |
| Ph | 6-7 |
| Water Solubility | Insoluble |
| Organic Solvent Solubility | Soluble |
| Storage Temperature | 5-30°C |
| Shelf Life | 12 months |
As an accredited Dual-end Hydrogen Silicone Oil RH-H6 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | RH-H6 Dual-end Hydrogen Silicone Oil comes in 200 kg net-weight steel drums, securely sealed and labeled for industrial transport and storage. |
| Container Loading (20′ FCL) | 20′ FCL: Dual-end Hydrogen Silicone Oil RH-H6 packed in drums, palletized, tightly secured, and loaded under dry, ventilated conditions. |
| Shipping | Dual-end Hydrogen Silicone Oil RH-H6 is shipped in sealed, dry, corrosion-resistant drums or containers, protected from moisture, acids, alkalis, and oxidizers. Store in a cool, ventilated area. Follow the SDS and applicable transport regulations for classification, labeling, and documentation. |
| Storage | Store in a cool, dry, well-ventilated warehouse away from direct sunlight, heat, sparks, and open flames. Keep containers tightly closed and protect from moisture and contamination. Separate from oxidizers, acids, alkalis, and catalysts. Use explosion-proof electrical equipment and proper grounding where required. Maintain clear labels, observe shelf-life, avoid prolonged storage, and follow the SDS and local regulations. |
| Shelf Life | Shelf life is 12 months in original, unopened containers stored cool, dry, and sealed, away from moisture, heat, and direct sunlight. |
For addition-cure RTV silicone molding compounds, dual-end hydrogen silicone oil RH-H6 functions as a linear chain extender rather than a conventional multifunctional crosslinker. When compounded with vinyl-terminated polydimethylsiloxane and a Karstedt platinum catalyst, the terminal Si-H groups undergo hydrosilylation at both chain ends, inserting a linear dimethylsiloxane segment between network junctions. This mechanism reduces crosslink density without increasing the sol fraction, resulting in lower Shore hardness and higher ultimate elongation. In a 150 L planetary mixer, Part A is prepared by dispersing 2–6 wt% RH-H6 into the vinyl polymer and treated fumed silica; Part B contains the platinum catalyst and 1-ethynylcyclohexanol inhibitor. Vacuum deaeration is run at −0.095 MPa for 10 min until visible bubble collapse. Pot life at 23 °C is typically 45–90 min, depending on inhibitor loading and ambient humidity. Cure is completed in 12 h at 23–25 °C or 4 h at 60 °C. Hardness is measured with ASTM D2240-15e1, tear strength with ASTM D624-00(2020) die C, and tensile properties with ISO 37:2017. Terminal products include low-durometer silicone mold liners, prosthetic mold surfaces, and vacuum casting tools. For food-contact service, the cured article must satisfy extraction limits under FDA 21 CFR 177.2600 and EU Regulation (EC) No 1935/2004; REACH SVHC screening under EC 1907/2006 is required for the uncured silicone system. The primary processing incompatibility is water ingress: if filler moisture exceeds 0.1 wt%, terminal Si-H groups can hydrolyze and release hydrogen gas, producing bubbles in thick sections.
Thermal cure speed in platinum-catalyzed silicone encapsulants is governed by inhibitor release, heat transfer through the potting thickness, and the Si-H/vinyl stoichiometric balance. In microelectronic glob-top formulations, RH-H6 is added at 2–5 wt% of the silicone fraction to reduce modulus after cure and to absorb thermomechanical stress in wire-bonded packages. The uncured mixture is dispensed with a precision jet valve at 35–50 °C and cured in a convection oven at 100 °C for 45 min plus 150 °C for 60 min. Hardness after cure is preferably below 40 Shore A, measured by ASTM D2240-15e1, so that copper wire deformation is minimized during thermal cycling. The relevant thermal cycling protocol is JEDEC JESD22-A104; optical clarity is checked by ASTM D1003 on a 2 mm cured slab. Process boundaries are strict: a Si-H/vinyl ratio above 1.4:1 leaves unreacted hydride that can produce gas voids at sustained junction temperatures above 170 °C; a ratio below 0.6:1 produces undercure and surface tack. Published data for RH-H6 in high-power IGBT or MOSFET encapsulation is limited, so lot-specific outgassing, ionic impurity, and adhesion to silver-plated leadframes must be characterized before production release.
Dehydrogenative gas evolution is the primary blowing mechanism when terminal Si-H silicone oil is used in two-part platinum-catalyzed silicone foam. Water or silanol groups present on aluminum hydroxide flame retardant and fumed silica react with Si-H groups to release hydrogen gas; the platinum complex accelerates the reaction. In a continuous static-mixer dispensing line, RH-H6 is dosed at 1.5–4.0 wt% of the total silicone matrix, while filler moisture content is controlled below 0.2 wt% by pre-drying at 110 °C for 3 h. The mixed material is dispensed into a compression mold or directly onto a battery module gap; gel time at 23 °C is typically 6–12 min. Foam density is measured by ISO 845, compression set by ISO 815-1:2019, and flame resistance by UL 94 V-0 on 3 mm specimens. Terminal products include flame-retardant gap fillers for electric vehicle battery packs and thermal interface pads. The critical process conflict is that excess moisture raises gas yield beyond the target density and can collapse closed-cell structure; insufficient moisture leaves the foam under-blown and too hard for low-pressure gap filling. Crosslinking must proceed fast enough to trap gas bubbles but not so fast that flow length drops below the required 80–120 mm in a 6 mm gap.
| Process parameter | Lower threshold | Upper threshold | Observed effect outside threshold |
|---|---|---|---|
| Filler moisture content | 0.05 wt% | 0.20 wt% | Below: viscosity exceeds 250 Pa·s and static mixer pressure rises; above: open-cell collapse and density below 0.35 g/cm³ |
| Si-H/vinyl molar ratio | 0.8:1 | 1.3:1 | Below: surface tack and incomplete network; above: residual hydride gas evolution above 120 °C |
| Static mixer L/D ratio | 10:1 | 16:1 | Below: striation uneven and density variation; above: shear heating reduces pot life below 5 min |
| Dispensing pressure | 0.8 MPa | 2.5 MPa | Below: air entrainment at nozzle; above: premature gelation in static mixer |
Solventless thermal release coatings based on addition-cure silicone are processed on five-roll coaters at line speeds of 120–400 m/min. RH-H6 is used as a chain-extending component within the crosslinker package to tune peel force without increasing silicone laydown. The coating bath is blended continuously with vinyl-functional siloxane, platinum catalyst, and inhibitor; terminal Si-H is dosed at 1.2–2.0 wt% of formulation solids. Typical silicone deposition on glassine or PET liner is 0.8–1.2 g/m², cured in a hot-air oven at 140–160 °C for 8–15 s. Release force is tested according to FINAT FTM 3 low-speed peel and FINAT FTM 4 high-speed peel; subsequent adhesion is measured by ASTM D3330/D3330M or FINAT FTM 1. Terminal products include label release liners, graphic film liners, and medical tape backings. The coating formulation must avoid catalyst poisons such as nitrogen-containing slip agents on film and residual peroxide on corona-treated PET. Unreacted Si-H can oxidatively crosslink during storage and raise peel force; therefore forced aging at 50 °C for 7 days is used to verify release stability before commercial rollout.
Soft silicone gel pads and scar care sheets are processed from two-part platinum-catalyzed formulations in which RH-H6 serves as a linear hydride donor. The component is metered into a dual-cartridge static mixer at a 1:1 ratio, with the silicone gel formulation adjusted to a pre-cure viscosity of 150–400 Pa·s at 23 °C. Cure at 80 °C for 60 min is typical; if the oven temperature drops below 70 °C, residual platinum activity may remain, and extractable cyclosiloxane levels can exceed the acceptance threshold. Final gel hardness is often 0.1–5 Shore 00 per ASTM D2240; elongation is not a primary specification for gel products. Biocompatibility is evaluated by ISO 10993-5 for cytotoxicity and ISO 10993-10 for skin sensitization; extractables are screened according to USP <467> for residual solvents and volatile methylsiloxanes. Terminal products include breast prostheses, scar therapy sheets, and orthopedic cushioning. The operational boundary is the post-cure step: steam autoclaving at 121 °C can degrade the gel if not fully post-cured; radiation sterilization above 25 kGy may increase crosslink density and raise hardness beyond specification limits.
Screen-printing pastes formulated with terminal Si-H silicone oil require high shear recovery and controlled thixotropy to maintain print definition on elastic textile substrates. In a solvent-free silicone ink system, RH-H6 is compounded at 1.0–3.0 wt% of the base polymer to adjust crosslink density and to improve film elongation after flash curing. The paste is printed through a 80–120 threads/cm polyester mesh onto pretreated nylon, cotton, or elastane fabric; blade pressure is set at 0.6–1.2 MPa and flash cure at 120 °C for 60–90 s. Final crosslinking is completed at 150 °C for 3 min in a conveyor oven. Elongation of the cured print is tested by ISO 13934-1 or ASTM D4964; wash fastness is assessed by ISO 6330; chemical safety of the finished textile is verified under Oeko-Tex Standard 100 class I for infant articles or class II for direct skin contact. Terminal products include grip socks, non-slip apparel prints, and garment labels. The main incompatibility is with aminopropyl silane adhesion promoters: amine-functional additives can poison the platinum catalyst and produce incomplete cure at the fabric interface.
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RH-H6 is a linear dual-end hydrogen silicone oil supplied as a clear, low-viscosity poly(methylhydridosiloxane) in which reactive Si–H groups are positioned at both α,ω chain termini. The methyl-substituted siloxane backbone contains no pendant hydride functionality; this structural arrangement is the principal distinction from side-chain polymethylhydridosiloxane fluids and from random methylhydridodimethylsiloxane copolymers. Representative specification limits are batch-dependent and are verified against the certificate of analysis before release. The analytical profile in Table 1 uses the test designations listed.
| Property | Representative Range | Test Method |
|---|---|---|
| Appearance | Clear, colorless to pale straw liquid | Visual |
| Kinematic viscosity at 25 °C | 4.0–8.0 mm²/s | ISO 3219:2013 / ASTM D4287-19 |
| Active hydrogen content | 0.06–0.16 wt% | Internal iodometric titration |
| Volatile content | ≤ 0.5 wt% | ASTM D4559-19 |
| Density at 25 °C | 0.960–1.010 g/cm³ | ISO 2811-1:2016 / ASTM D4052-22 |
| Refractive index at 25 °C | 1.395–1.410 | ISO 280:1998 |
| Flash point, closed cup | ≥ 130 °C | ISO 2719:2016 / ASTM D93-20 |
| Water content | ≤ 200 mg/kg | ISO 15512:2019 Karl Fischer |
Batch acceptance is tied to the test designations above, not to nominal values. Where water-sensitive platinum catalysts are used, moisture removal is required before dosing; the material is considered dry when the water content is below 200 mg/kg by Karl Fischer titration. The terminal architecture separates RH-H6 from side-chain methylhydridosiloxane fluids. A fluid with pendant Si–H groups forms branch points during addition cure, while RH-H6 forms linear extensions. A single-end hydride species acts as a chain stopper. This distinction is used to formulate low-hardness and high-elongation silicone articles without changing vinyl polymer content.
In addition-cure liquid silicone rubber, hydrosilylation between Si–H and vinyl-terminated polydimethylsiloxane is catalysed by Karstedt platinum. The position of the hydride group determines whether the network grows by linear chain extension or by branch formation. When total Si–H:Si–vinyl molar ratio is held between 1.20:1 and 1.45:1 with platinum loading between 3.0 ppm and 6.0 ppm, terminal Si–H in RH-H6 produces longer inter-crosslink segments than a random side-chain hydride fluid of equivalent active hydrogen content. The resulting vulcanizate shows lower hardness and higher elongation without proportional changes in cure time.
| Cured Property | Side-Chain PMHS Reference | RH-H6 Terminal | Test Method |
|---|---|---|---|
| Shore A hardness | 55–60 | 45–50 | ISO 48-4:2018 |
| Tensile elongation | 300–360 % | 420–500 % | ISO 37:2024 |
| Type 1 tear strength | 10–14 N/mm | 16–22 N/mm | ISO 34-1:2022 |
| Compression set, 22 h at 175 °C | 18–24 % | 12–16 % | ISO 815-1:2022 |
| Pot life at 25 °C | < 4 h | 72 h | Rheometric viscosity doubling |
The reduction in hardness is achieved without adding unreactive dimethyl silicone oil, which can migrate to the surface over time. In a vacuum compression press with 50-ton clamp force and molding at 130 °C for 8 min, the terminal hydride slab reached Shore A 48 after post-cure at 150 °C for 4 h, while the side-chain control measured Shore A 57. Terminal hydride does not eliminate cure; ATR-FTIR spectra collected after cure showed no detectable Si–H absorption at 2150 cm⁻¹. If the total Si–H:Si–vinyl ratio exceeds 1.50:1, unreacted terminal Si–H may remain and can react with atmospheric moisture to form silanol species, increasing compression set after 22 h at 175 °C per ISO 815-1:2022.
In closed-loop LSR metering units with 12–20-element static mixers and feed-line temperatures between 25 °C and 40 °C, terminal Si–H functionality reduces the viscosity of the mixed compound. A 70 Shore A reference compound prepared with a 30 Pa·s vinyl polymer and side-chain hydride fluid was reformulated with RH-H6 to target 55 Shore A without changing base polymer. Mixed material viscosity decreased from 235 Pa·s to 190 Pa·s at 25 °C and 10 s⁻¹ shear rate on an Anton Paar MCR 302 rheometer with a 50 mm 1° cone per ISO 3219:2013. Injection molding trials on an 1,100 kN clamp-force LSR machine with a 12-cavity cold-runner mold used a barrel temperature of 30 °C and a cavity temperature of 140 °C; the RH-H6 formulation completed cure in 25 s, while the side-chain control required 32 s. The shorter cycle is attributed to a lower concentration of unreactive hydride-bearing oligomers and more efficient terminal Si–H accessibility.
At ambient relative humidity above 60 %, pre-drying is required. Terminal Si–H can hydrolyse to silanol in the presence of residual moisture or alkaline filler surfaces. Storage under nitrogen with desiccant breathers is recommended; exposure to open air at 25 °C and 60 % relative humidity for more than 4 h can increase water content above 200 mg/kg. Carbon steel vessels are unsuitable for prolonged storage because dissolved iron salts accelerate Si–H decomposition and gaseous hydrogen evolution.
Surface treatment of precipitated silica with terminal hydride fluid is performed in a Henschel-type high-shear mixer at 800–1,400 rpm and jacket temperature 70–90 °C for 8–15 min. Under these conditions, terminal Si–H reacts with surface hydroxyl groups to form Si–O–Si bonds and releases hydrogen gas. The α,ω architecture leaves a polydimethylsiloxane-like methyl segment between the surface bonds, which lowers the surface energy of the treated filler. In a lab-scale treatment using 2.5 wt% RH-H6 on precipitated silica with a BET surface area of 180 m²/g, the water contact angle increased from 0° for untreated silica to 138–142° after treatment, measured by DIN 55660-2:2011. The treated filler retained 165–170 m²/g BET surface area to ISO 9277:2022, indicating that the fluid did not substantially block mesopores.
Dispersion in a 25 mm co-rotating twin-screw extruder with 36:1 L/D ratio and 30 wt% filler loading was assessed by Mooney viscosity and tear strength. The RH-H6-treated silica compound gave Mooney viscosity ML(1+4) 24 MU at 100 °C per ISO 289-1:2018, compared with 38 MU for untreated silica. Type 1 tear strength of the cured compound increased from 18 N/mm to 24 N/mm per ISO 34-1:2022. Published data for this specific extruder configuration is limited; the observed trend is consistent with reduced filler-filler network formation after terminal hydride treatment. Amine-based release agents should be avoided because residual amines accelerate Si–H hydrolysis and can increase hydrogen pressure in closed mixing vessels.
Residual low-molecular-weight cyclosiloxanes in hydride fluids influence platinum catalyst activity. RH-H6 is stripped by wiped-film evaporation at jacket temperature 120–140 °C and vacuum ≤ 1 kPa to reduce octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane combined content below 300 mg/kg. In platinum-catalysed LSR, cyclosiloxane concentrations above 600 mg/kg act as fugitive inhibitors and increase platinum demand. A side-chain hydride fluid with 800 mg/kg D4/D5 required 6.0 ppm platinum to reach 12 s T90 at 140 °C in a moving die rheometer per ISO 13145:2012, whereas RH-H6 at 200 mg/kg D4/D5 reached the same T90 with 3.5 ppm platinum. The lower platinum demand reduces residual platinum content in cured parts and narrows cure time variation in high-speed molding. Storage should be in 316L stainless steel under nitrogen at 5–30 °C; prolonged contact with copper, zinc, or iron alloys should be avoided because transition metals catalyse Si–H condensation and hydrogen evolution.
If low-hardness optical encapsulants require a cured Shore OO hardness below 20 and high optical clarity without phenyl monomers, the terminal hydride fluid supplies a chain-extension route that avoids adding excess unreactive dimethyl fluid. In a two-part platinum-cured encapsulant cured at 100 °C for 1 h, RH-H6 produced Shore OO hardness 18–22 and elongation at break 150–200 % measured per ASTM D412-16, while a side-chain hydride fluid at the same Si–H:Si–vinyl ratio produced Shore OO 32–38 and elongation below 90 %. The difference arises because terminal Si–H creates linear polydimethylsiloxane segments between crosslink sites, whereas pendant hydride creates a denser multi-armed network.
Optical transmittance at 400 nm through a 5 mm path length remained above 97 % by ASTM D1003-21 for the RH-H6 encapsulant. The refractive index was 1.402 at 25 °C by ISO 280:1998. Pot life of the mixed formulation at 25 °C was 72 h before viscosity doubled, compared with 24 h for the side-chain control, because terminal Si–H reduces early branching gelation. Terminal hydride fluids do not provide inherent UV stabilisation; formulations exposed to UV radiation above 380 nm require separate stabiliser packages. If the encapsulant contacts copper alloy lead frames, Si–H groups may dehydrocouple on copper surfaces, and cuprous ions may poison platinum catalysts.
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