Vinyl Terminated Silicone Oil RH-Vi305

Before addition-cure LSR elastomer is mixed on a production line, RH-Vi305 is charged as the difunctional vinyl macromonomer that reacts with methylhydrogensiloxane through a platinum-catalyzed hydrosilylation addition mechanism. The working stoichiometry is set at an Si-H:Si-Vi molar ratio between 1.4:1 and 1.7:1; a ratio of 1.5:1 is preferred for compounds targeting Shore A 30 because lower ratios leave unreacted terminal vinyls that depress final crosslink density and raise compression set after 22 h at 175 °C when tested according to ASTM D395 Method B. The vinyl oil is blended with hexamethyldisilazane-treated fumed silica at 15–30 phr, using a 1.5 L planetary mixer running at 35 rpm for 4–6 min followed by 30 mbar vacuum degassing for 10 min; the same procedure can be scaled to a 25 mm co-rotating twin-screw extruder with an L/D 40:1 profile, but the vacuum degassing unit must maintain 50 mbar or below to prevent air occlusion in the liquid silicone feed. Platinum-cyclovinylmethylsiloxane complex is metered at 5–10 ppm Pt relative to the vinyl component; below 3 ppm the cure at 120 °C becomes sluggish and parts retain surface tack after 10 min in a 1,800 kN clamping force injection molding machine with a barrel set at 180 °C. Ethynyl cyclohexanol inhibitor is split-fed at 0.05–0.15 phr to extend pot life beyond 8 h at 25 °C without suppressing the fast-cure window. A 20 phr fumed silica compound post-cured for 2 h at 200 °C typically develops tensile strength 5–8 MPa and elongation 400–700 % per ASTM D412, with tear strength 20–35 N/mm per ASTM D624. Batch-to-batch viscosity drift in RH-Vi305 is screened at 25 °C using ASTM D445, and vinyl content is checked by FT-IR peak ratio at 990–1010 cm⁻¹ against the supplier certificate of analysis before crosslinker ratio adjustment.

What Happens When RH-Vi305 Replaces Dimethylvinylsiloxy-Terminated PDMS in Solventless Release Coatings?

The replacement of dimethylvinylsiloxy-terminated PDMS with RH-Vi305 in solventless thermal release coatings on corona-treated PET and BOPP alters hydrosilylation stoichiometry because the vinyl-functional oil is blended with a trimethylsiloxy-terminated methylhydrogensiloxane crosslinker and platinum catalyst at Si-H:Si-Vi molar ratios between 2.0:1 and 2.5:1, as the film surface consumes silicon hydride through competitive oxidation and hydrolysis at the interface. A 5-roll solventless coater running at 150 m/min and 0.8–1.2 g/m² dry coat weight applies the formulation; cure is completed in a 3 m hot air oven at 155 °C for 12–15 s. Release force after lamination with a solvent acrylic adhesive is measured per FINAT FTM 3 at 300 mm/min and controlled between 5 cN/25 mm and 50 cN/25 mm by adding vinyl-MQ resin at 10–30 phr. Subsequent adhesion of the laminate to a stainless steel panel is tested per FINAT FTM 1 and must retain ≥80 % of the uncoated control. The main process failure mode occurs when RH-Vi305 migrates into the film surface before curing, producing a bond-stripping defect on the silicone rubber; this is corrected by increasing the hydride-functional crosslinker to a Si-H:Si-Vi ratio of 2.5:1 and adding 0.1–0.3 wt% of a phenyl- or fluorosilicone release-control additive. Platinum catalyst loadings of 80–120 ppm are necessary on corona-treated PET grades because nitrogen-containing slip additives poison the metal complex; pot life at 35 °C falls below 4 h on lines running without chilled doctor rolls, and the accelerated gelation appears as a viscosity rise beyond 300 mm²/s on a Brookfield viscometer at 25 °C. Residual unreacted vinyl oil extracted from the cured film is quantified by GC-MS after 2 h at 150 °C and should remain below 0.5 wt% to avoid transfer to the adhesive. For food-contact release liners, Article 3 of Regulation (EC) No 1935/2004 and FDA 21 CFR 175.300 apply to the total system, not to RH-Vi305 alone.

Inside sealed power converter modules and high-voltage transformer assemblies, RH-Vi305 functions as the liquid vinyl component of a two-part addition-cure dielectric gel in which the crosslinker is a low-molecular-weight methylhydrogensiloxane. The Si-H:Si-Vi molar ratio is reduced to 0.8:1–1.2:1 to produce a Shore 00 hardness of 10–40 when measured on a Shore 00 durometer; the cured gel must remain tacky enough to absorb thermal expansion mismatch but stiff enough to resist creep under 85 °C continuous load. Mixing is performed in a 0.5 L planetary mixer at 25 °C and 1:1 ratio tolerance ±2 %, followed by vacuum degassing below 50 mbar for 10 min in a vacuum encapsulation chamber with 1,500 L/s pump capacity. Cure schedules of 80 °C for 60 min or 100 °C for 30 min are used; processing below 80 °C extends pot life but yields incomplete catalyst activation on thermally massive coils, while temperatures above 120 °C create bubbling at the gel surface because residual water and low-molecular-weight siloxanes volatilize. Dielectric strength after post-cure at 150 °C for 4 h is measured per ASTM D149 at 18–25 kV/mm, volume resistivity is specified above 1 × 10¹⁵ Ω·cm per IEC 62631-3-1, and the dielectric constant at 1 MHz is controlled at 2.7–2.9 per ASTM D150. Partial discharge inception voltage is screened per IEC 60270, and thermal shock from -40 °C to 150 °C is run per IEC 60068-2-14. Extractable chloride must remain below 2 ppm and sodium below 1 ppm by ion chromatography to prevent electrochemical migration under biased humidity testing at 85 °C/85 % RH per JESD22-A101.

When Pt Catalyst Activity Is Lost in LED Encapsulant Blends

High-power LED encapsulant dispensing lines using RH-Vi305 to reduce phenyl-silicone prepolymer viscosity encounter a refractive-index boundary: at 10–30 phr the blend viscosity drops from 8,000 mm²/s to 2,500 mm²/s at 25 °C, but the dimethyl polysiloxane chain reduces the cured refractive index from 1.54 to below 1.50 when loading exceeds 30 phr, which appears as a lumen drop due to internal reflection at the phosphor interface. The blend is platinum-catalyzed at 5–15 ppm and cured at 150 °C for 1 h followed by 180 °C for 4 h under nitrogen; catalyst activity is lost when phosphor slurries carry trace amine or tin residues, causing surface tack and a Shore D hardness below 40 instead of the specified 55–65 when measured per ASTM D2240. Added 1–2 wt% of a cyclic methylvinyl siloxane inhibitor restores 70–80 % of the catalyst activity, but excess inhibitor raises the minimum cure temperature to 160 °C and limits the usable production window to ±10 °C. Thermal aging at 150 °C for 1,000 h under IEC 60068-2-2 is used to screen for yellowing: optical transmittance at 450 nm per ASTM D1003 should remain above 95 %, and yellowing index per ASTM E313 should not exceed ΔYI 2.0. In gold-wire-bonded packages, the low hardness of RH-Vi305-modified gels reduces wire-sweep damage during transfer molding, but the same softness lowers red dye penetration resistance; the 85 °C/85 % RH biased humidity test per JESD22-A101 can show anodic migration when extractable ionic impurities exceed 2 ppm chloride and 1 ppm sodium, so the raw oil must meet ion chromatography limits before use.

During two-roll mill compounding of high-consistency silicone rubber, RH-Vi305 is introduced at 2–5 phr on a 60-inch two-roll mill with a roll speed ratio of 1.2:1 and nip gap 2 mm to reduce Mooney viscosity ML 1+4 at 100 °C from approximately 55 to 35 when measured per ASTM D1646. The vinyl oil also raises the gum's effective vinyl content, shifting dicumyl peroxide cure toward higher crosslink density and lower compression set after 22 h at 175 °C in ASTM D395 Method B. On a 90 mm vented extruder operating at 40 rpm and 80 °C barrel temperature, compound containing 3 phr RH-Vi305 exhibits reduced die swell and lower extrudate roughness compared with a neutral paraffinic oil at the same loading, but peroxide-cure compounds must be pre-blended below 60 °C to prevent premature vinyl addition reactions with dicumyl peroxide. Published data for this specific configuration is limited; plant trials on a 5 L internal mixer show batch-to-batch Mooney variation is controlled within ±3 units when RH-Vi305 is temperature-conditioned to 25 °C before addition.

Medical-Grade LSR and Skin-Contact Elastomer Compliance Checkpoints

Medical-grade LSR produced from RH-Vi305 requires low volatile cyclic siloxane content because D4, D5 and D6 are restricted under REACH Annex XVII Entry 70a for wash-off cosmetic products, and medical device converters frequently apply a tighter limit of <0.1 wt% total volatiles by headspace GC-MS after post-cure for 4 h at 200 °C in a forced-air oven. The final cured article is tested for cytotoxicity per ISO 10993-5:2009 using L929 cells and for skin irritation per ISO 10993-10:2010; these tests are performed on the fully formulated elastomer, not on RH-Vi305 alone, because platinum catalyst residues and fumed silica surface treatment can influence the biological response. For rubber articles intended for repeated food contact, the final compound must comply with FDA 21 CFR 177.2600 and, in the EU, with Regulation (EC) No 1935/2004 as well as Regulation (EC) No 2023/2006 on good manufacturing practice. Residual platinum after extraction is controlled below 5 mg/kg by ICP-MS in converter specifications. It is an operational boundary that RH-Vi305 should not be combined with amine-containing internal mold-release additives in medical compounds because amine groups complex with the platinum catalyst and produce undercure that fails both hardness and extractables testing. Furthermore, the compounded LSR must be processed at relative humidity <60 % or the silica filler adsorbs surface moisture and releases water during injection molding, causing bubbles and lower dielectric/skin-contact surface quality.