| HS Code | 169040 |
| Appearance | Colorless to pale yellow transparent liquid |
| Chemical Composition | Hydrogen-terminated polydimethylsiloxane |
| Terminal Functional Group | Si-H at both chain ends |
| Viscosity At 25 C | 20-100 mPa·s |
| Hydrogen Content | 0.10-0.20 wt% |
| Density At 25 C | 0.95-0.98 g/cm³ |
| Refractive Index At 25 C | 1.400-1.410 |
| Volatile Matter | ≤2.0 wt% |
| Flash Point | >100 °C |
| Ph | 6-8 |
| Solubility | Soluble in toluene, xylene, ether and other organic solvents; insoluble in water |
| Storage Stability | Stable under sealed, dry conditions away from light |
As an accredited Dual-end Hydrogen Silicone Oil RH-H518 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Dual-end Hydrogen Silicone Oil RH-H518 is supplied in 200 kg net iron drums with inner plastic liners for safe storage and transport. |
| Container Loading (20′ FCL) | Dual-end Hydrogen Silicone Oil RH-H518 is loaded in a 20′ FCL container, securely packed in drums for safe international sea transport. |
| Shipping | Dual-end Hydrogen Silicone Oil RH-H518 is shipped in sealed, moisture-proof drums or IBCs under cool, dry, ventilated conditions. Avoid heat, sunlight, water, and contamination; prevent leakage and comply with the SDS and local transport regulations. |
| Storage | Store RH-H518 in a tightly closed original container in a cool, dry, well-ventilated area protected from direct sunlight and moisture. Keep away from heat, ignition sources, and incompatible materials such as strong oxidizers, acids, and alkalis. Maintain clear labeling, avoid freezing, keep out of reach of unauthorized personnel, and do not store with food or feed. Follow local regulations and SDS guidance. |
| Shelf Life | Shelf life is 12 months in original unopened packaging, stored cool, dry, well-ventilated, away from direct sunlight and moisture. |
In addition-cure liquid silicone rubber (LSR) feeding a liquid injection molding (LIM) cell with a cooled static mixer and reciprocating screw unit, dual-end hydrogen silicone oil RH-H518 is metered into the B-side as a chain-extending crosslinker rather than a pendant Si-H fluid. The terminal Si-H architecture lengthens the vinyl-functional PDMS network between pendant vinyl sites before three-dimensional crosslinking, which permits a reduction in Shore A hardness without increasing plasticizer content and without the high post-cure volatile content associated with unreacted short-chain siloxanes. For infant-care and food-contact articles such as silicone nipples, the compliance matrix is EN 14350-1:2020, 21 CFR 177.2600, EU 1935/2004, and BfR XV; if the same compound is used in medical skin-contact parts, ISO 10993-5:2009 in vitro cytotoxicity and ISO 10993-10:2010 skin sensitization are also applied. RH-H518 is added at 2.0–5.0 wt% relative to vinyl-functional PDMS gum, with total Si-H/Si-Vi molar ratio maintained at 1.1–1.6:1; a platinum catalyst is introduced at 5–15 ppm Pt, an alkyne or vinyl siloxane inhibitor at 0.02–0.08 phr, and the mixed material is kept below 25 °C to preserve pot life. The production process uses a 25:1 L/D injection screw, barrel sections held at 18–24 °C, static mixer, and mold temperature 120–160 °C; cure time for 2 mm wall thickness is 30–60 s, followed by demolding and a 4 h post-cure at 200 °C to reduce volatile cyclic siloxanes below applicable migration limits. Amine-containing release agents, sulfur-vulcanized rubber residues, and tin-catalyzed silicone contamination in tooling must be excluded because these species inhibit the Pt-hydrosilylation catalyst. Terminal finished products are infant feeding nipples, anti-colic valve membranes, and reusable pump diaphragm seals requiring repeated steam sterilization at 121 °C without hardness drift.
High-refractive-index phenyl-containing vinyl silicone resin systems for chip-on-board LED encapsulation use RH-H518 as a terminal Si-H chain extender to suppress the dense short-chain nodal domains that raise storage modulus and accelerate thermal yellowing under continuous 85 °C / 85% RH aging; the terminal Si-H architecture produces a more uniform crosslink distribution and reduces the required loading of low-molecular-weight pendant crosslinker. Optical compliance is established through ASTM D1003-13 transmittance ≥98% at 450 nm through a 2 mm cured specimen, ASTM E313-10 yellowness index ≤1.5 after 1000 h at 150 °C, and UL 94 V-0 flammability classification of the cured encapsulant; automotive LED packages additionally reference AEC-Q102 qualification and JEDEC JESD22-A101C steady-state temperature-humidity bias. RH-H518 is incorporated at 5–12 wt% of the phenyl vinyl resin solids, with Si-H/Si-Vi molar ratio kept at 1.0–1.4:1, platinum catalyst at 2–8 ppm Pt, and viscosity adjusted to 3,500–5,500 mPa·s at 25 °C to permit precision needle dispensing without stringing. Downstream production involves dispensing onto leadframe trays under vacuum below 100 Pa to eliminate microvoids at the die surface, followed by staged thermal cure of 100 °C for 1 h and 150 °C for 4 h; the staged profile allows stress relaxation and prevents wire sweep in fine-gauge gold or copper wire bonds. Incompatibility with sulfur-containing die-attach materials requires a barrier layer or complete solvent removal before encapsulation. Terminal finished products are COB LED modules for downlights, automotive headlamp arrays, and backlight bars specified for luminous-flux maintenance after 6000 h at 105 °C.
When solventless addition-cure silicone is knife-over-roll coated onto 470 dtex polyamide 6.6 airbag fabric, RH-H518 is introduced as a modulus-lowering chain extender to reduce inter-yarn slippage and improve seam burst resistance at deployment strain rates. Coated fabric compliance is normally established under FMVSS 302 and ISO 3795 burn-rate performance, ISO 13934-1:2013 tensile strength of coated woven fabric, ASTM D751-19 coating adhesion and scuff resistance, and automaker-specific deployment tests requiring cushion inflation time ≤30 ms. RH-H518 is added at 2.0–4.5 wt% of the vinyl silicone base polymer, with Si-H/Si-Vi molar ratio maintained at 1.2–1.8:1; terminal Si-H chain extension lowers the cured coating’s tensile modulus to 1.5–4.0 MPa at 100% elongation under ISO 37:2017 and raises elongation at break to 400–700%, which is required to absorb the shock of pyrotechnic inflation without seam fracture. On a typical airbag fabric coater, a reverse roll or knife-over-roll head applies 20–80 g/m² of silicone onto the woven fabric at line speed 20–60 m/min; the coated fabric is passed through a hot-air oven at 160–190 °C for 40–90 s. Ambient relative humidity above 60% RH requires fabric pre-drying at 120 °C for 20 s before coating to prevent microbubbles at the fiber interface. Terminal finished products are driver, passenger, knee, and side-curtain airbag cushions with silicone-coated fabric retaining low-temperature deployability at -35 °C.
In solventless thermal-cure silicone release coatings for PET and polypropylene film substrates, dual-end hydrogen-terminated silicone oil RH-H518 is introduced as a controlled-reactivity crosslinker that maintains the Si-H/Si-Vi cure at the coating-air interface while permitting reduced platinum catalyst loading. For release liners used in food-contact adhesive applications, the relevant compliance standard is 21 CFR 175.300; EU compliance follows Regulation 10/2011/EU with overall migration ≤10 mg/dm²; release-force testing is performed according to FINAT FTM 3 at 180° peel angle and 300 mm/min, with typical targets of 5–25 cN/50 mm depending on the adhesive family. RH-H518 is blended at 1.0–3.0 wt% of total silicone solids, giving an Si-H/Si-Vi molar ratio of 1.5–2.5:1; platinum catalyst is maintained at 50–120 ppm, and the inhibited bath shows a pot life beyond 8 h at 25 °C. A five-roll direct gravure coater with a chrome-plated gravure cylinder applies 3–6 µm wet film thickness to corona-treated PET at 48 mN/m minimum surface energy and web speed 300–800 m/min; the film then passes through high-velocity hot-air ovens at 140–180 °C with dwell time 2–6 s to achieve the required degree of cure. Residual Si-H after cure is monitored by ATR-FTIR at 2160 cm-1 to prevent post-cure peel drift and liner blocking. Terminal finished products include release liners for pressure-sensitive adhesive labels, medical wound-care tape, and double-sided graphic films, where downstream converting and die-cutting occur at line speeds that require low and stable release force.
High-consistency silicone rubber (HCR) compounding with addition-cure systems uses RH-H518 as a dual-end hydrogen silicone oil chain extender to reduce residual cyclic siloxane volatiles in molded automotive gaskets, because terminal Si-H reaction sites bind linear vinyl silicone chains more completely than pendant Si-H fluids and thereby lower extractable D4/D5/D6 cyclics after post-cure. Material specifications for automotive coolant and oil sealing gaskets include heat aging per ISO 188:2023 at 150 °C for 168 h, compression set per ASTM D395-18 method B ≤15% after 22 h at 175 °C, Shore A hardness 50–65 per ASTM D2240-15, and volatile condensable content ≤0.2% after 4 h at 200 °C under OEM internal standards. RH-H518 is mixed on a two-roll mill at 1.0–2.5 phr into a methyl vinyl silicone polymer compound, with Si-H/Si-Vi molar ratio held at 1.2–1.6:1 and platinum catalyst at 5–10 ppm Pt; sulfur-containing release agents and amine-based antiozonants are excluded because they cause platinum inhibition or unintended hydrosilylation cure drift. The downstream process begins in a 50 L kneader at 60–100 °C, followed by strainer filtering through 325-mesh screens, then transfer molding or injection molding at 160–180 °C for 120–300 s; post-cure in forced-air ovens at 200 °C for 4 h removes residual volatile oligomers and stabilizes compression set. Terminal finished products are molded O-rings, coolant pipe gaskets, and oil pan gaskets requiring sealing force retention in glycol/water mixtures at 125 °C without excessive cyclosiloxane volatilization.
For battery pack perimeter seal applications, two-component addition-cure liquid silicone rubber dispensing onto aluminum or polycarbonate enclosure flanges uses RH-H518 as a chain extender to reduce elastic modulus and prevent delamination during differential thermal expansion between the cast aluminum cover and composite battery tray. The compliance set includes UL 94 V-0, REACH, RoHS 2011/65/EU, ISO 6469-1:2017 for electric-vehicle safety, and IEC 60529:2013 for IP67/IP68 enclosure integrity; compression set according to ASTM D395-18 method B is specified at ≤10% after 1000 h at 85 °C, and damp heat adhesion is tested per IEC 60068-2-78:2012 at 85 °C / 85% RH for 1000 h. RH-H518 is metered at 3–6 wt% of the vinyl polymer component, with Si-H/Si-Vi molar ratio 1.3–1.7:1, adhesion promoter at 0.5–1.5 wt%, and rheology adjusted to 70–120 Pa·s at 10 s−1 for robotic bead application width 3–8 mm. A servo-driven two-component dispenser with a static mixer applies a continuous bead along the flange, followed by thermal cure at 120–160 °C for 10–30 min in a convection oven or 2–5 min under in-line infrared heating; final assembly compression is set at 20–40% of bead height to generate the sealing force without overstressing the elastomer. Terminal finished products are battery pack perimeter gaskets, cover seal profiles, and high-voltage connector seals that must maintain leak-tight integrity after 1000 h damp heat without adhesion loss or compression-set-induced gap formation.
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RH-H518 is supplied as a linear telechelic polydimethylsiloxane carrying silicon-hydride groups at both terminal silicon atoms, with the general structure H–Si(CH₃)₂–O–[Si(CH₃)₂–O]ₙ–Si(CH₃)₂–H and CAS registry number 70900-21-9. The reactive terminal Si-H functionality is intended for platinum-catalyzed hydrosilylation with vinyl-functional silicones. In this architecture the hydride is not distributed along the siloxane backbone; the product therefore behaves as a chain-extending telechelic reactive fluid rather than as a pendant hydrogen crosslinker. Model RH-H518 is controlled for low volatile content, defined terminal Si-H concentration, and narrow viscosity distribution to permit reproducible addition-cure formulation.
The specification profile shown below is representative of hydride-terminated polydimethylsiloxanes in this viscosity class. Exact lot acceptance values are reported on the certificate of analysis and should be used for production batch calculations.
| Property | Test method or reference | Representative range/value |
|---|---|---|
| Appearance | Visual inspection | Colorless to pale-yellow transparent liquid |
| Viscosity at 25 °C | ISO 3104:2023 / ASTM D445 | 10–30 mm²/s |
| Terminal silicon-hydride content | Gas displacement after sodium butoxide digestion | 0.18–0.26 wt% as hydrogen |
| Volatile content | ASTM D4559 at 105 °C / 3 h | ≤1.5 wt% |
| Refractive index at 25 °C | ISO 2807 | 1.401–1.409 |
| Specific gravity at 25 °C | ASTM D891 | 0.97–0.99 |
| Flash point, closed cup | ASTM D93 | ≥120 °C |
The terminal hydrogen content expressed as weight percent hydrogen is the primary specification for stoichiometry control. It is determined by digestion with excess sodium butoxide followed by gas displacement rather than estimated from nominal molecular weight alone. Volatile content is controlled at ≤1.5 wt% because unconverted cyclic or low-molecular-weight siloxanes can deposit on processing equipment or contribute to extractable matter in cured articles.
In a pendant methylhydrogen polysiloxane, multiple Si-H sites are distributed along the polymer chain. One molecule can react with several vinyl groups to form trifunctional or tetrafunctional junction points, leading to high crosslink density and increased Shore A hardness. In RH-H518, the reactive sites are confined to the two chain ends. Reaction with an α,ω-divinyl polydimethylsiloxane at an Si-H:vinyl ratio near 1.0:1.0 produces predominantly linear chain extension, with lower junction density and a lower plateau modulus in the cured network. The structural difference is evaluated by dynamic mechanical analysis according to ISO 6721-1:2019 and by tensile testing under ASTM D412 or ISO 37:2017. Compared with pendant hydrogen fluids of equivalent active hydrogen content by weight, terminal hydrogen architecture tends to reduce crosslink density without requiring addition of non-reactive silicone oil diluents, which can migrate or lower long-term mechanical stability.
Addition-cure liquid silicone rubber compounding incorporates RH-H518 at low addition rates to modify elongation, hardness, and compression set. In high-consistency rubber or LSR systems, the fluid is typically premixed with vinyl-functional polymer and silica before addition of the platinum catalyst. Typical evaluation formulations use 0.5–5.0 phr RH-H518 relative to vinyl-functional gum or LSR base; the precise addition level is adjusted by cured-hardness targets measured with ISO 48-4 and tensile properties measured under ISO 37:2017. The hydrosilylation reaction proceeds at 80–150 °C with Karstedt catalyst at 1–10 ppm platinum. Without an inhibitor, the mixed compound can gel at 25 °C within 4–8 h; addition of 1–10 ppm 1-ethynyl-1-cyclohexanol extends pot life to 24–72 h in typical formulations. High-shear mixing is carried out in planetary mixers or in twin-screw devices with L/D ratios above 40:1. Vacuum degassing at −0.09 MPa and 25–40 °C is used before mold filling, but degassing time must be limited because moisture-induced Si-H hydrolysis can generate hydrogen gas in closed mixer headspace.
Solventless thermal release coating systems replace a portion of the pendant hydrogen fluid with RH-H518 to shift the cured film from a highly branched network toward a more linear, chain-extended network. Release force stability is evaluated from cured films on polyethylene terephthalate or biaxially oriented polypropylene using FINAT FTM 3 at 300 mm/min peel speed. Typical coat weights are 0.8–1.5 g/m², with web temperatures of 120–160 °C and dwell times of 20–60 s. In this application the lower volatile content of RH-H518, controlled at ≤1.5 wt% at 105 °C / 3 h by ASTM D4559, reduces the tendency for volatile deposition on curing ovens and backside transfer in high-speed coating lines. Soak extraction is quantified by ISO 6427:2013; film extractables must be confirmed after cure because residual Si-H or vinyl species directly affect subsequent lamination bond strength.
In optical encapsulant formulations, terminal Si-H architecture is selected when stoichiometric curing with vinyl-functional siloxanes is intended to leave fewer unreacted pendant hydride moieties in the cured encapsulant. Optical transmission is measured on cured specimens according to ASTM D1003, and yellowing after thermal aging is assessed with ASTM D1925 after 150 °C / 1000 h aging. Final transmittance depends on siloxane refractive index, catalyst residues, and thermal history; published data for RH-H518 in highly filled optical encapsulant matrices is limited, and direct formulation screening is required.
Electronics potting and conformal coating formulations use terminal Si-H functionality to achieve low-stress encapsulation with reduced modulus after cure. In comparison with side-hydrogen fluids at equivalent active hydrogen content by weight, RH-H518 yields a higher average molecular weight between crosslinks, which can be characterized by solvent swelling using ASTM D2765 or ISO 1817:2015. This property is used to reduce stress on wire bonds in power modules. Cured specimens are evaluated for volume resistivity under IEC 62631-3-1 and dielectric strength under IEC 60243-1. The terminal Si-H fluid should be dried under vacuum at 60–80 °C for 30–60 min before compounding if container headspace moisture exceeds 1000 ppm; otherwise microvoids may form from hydrogen release during cure.
Storage and handling boundaries for RH-H518 require sealed containers under dry nitrogen at 0–30 °C. Terminal silicon hydride groups react slowly with water to release hydrogen and form silanol; material stored beyond 6 months should be retested for hydrogen content and volatiles before use. The product should not be mixed with amine-functional silanes, organotin compounds, sulfur-containing additives, or acetylene inhibitors above the concentrations required for pot-life control, because these species can poison platinum catalysts or reduce hydrosilylation conversion. Equipment previously used for condensation-cure tin-catalyzed silicones must be cleaned to trace-metal levels before RH-H518 is introduced. Exposure to strong oxidizers and strong bases is incompatible because alkaline media can generate flammable hydrogen gas. Regulatory compliance for RH-H518 is typically supported by supplier declarations under EU REACH EC 1907/2006 for SVHC content below 0.1 wt% and under RoHS EU 2011/65/EU for homogeneous material restrictions. Food-contact use is not established for the uncured fluid; if cured silicone elastomers are intended for repeated food-contact applications, the final article must satisfy FDA 21 CFR 177.2600 extraction limits or EU 10/2011 overall migration limits, which are article-specific.
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