Vinyl Terminated Silicone Oil RH-Vi1311

In Class 2 power-electronics potting, RH-Vi1311 is metered as the vinyl-bearing component of a two-part addition-cure silicone filled with fused spherical alumina to balance thermal impedance and low-stress adhesion. The A-side is prepared by dispersing 70–85 wt% spherical α-alumina having D50 5–10 µm into RH-Vi1311 under vacuum at 60–80°C; the B-side contains a methylhydrogensiloxane crosslinker at 1.2–1.8 mol Si-H per 1 mol terminal vinyl. A platinum(0)-divinyltetramethyldisiloxane complex is added at 5–15 ppm Pt. 2-methyl-3-butyn-2-ol or tetramethyltetravinylcyclotetrasiloxane inhibitor is adjusted so that the mixed compound shows a 25°C pot life of 60–120 min. Hydrosilylation liberates no volatile reaction byproduct, but low-molecular-weight cyclic oligomers may remain if the feed is not stripped. Cured hardness is controlled by the Si-H:Vi ratio and filler loading rather than by plasticizer addition: a formulation with 1.4:1 Si-H:Vi and 75 wt% alumina typically yields Shore A 60–70 and elongation at break above 100% when tested according to ASTM D412. For thermal management, the composite is compressed to a bondline thickness of 0.25–0.50 mm and tested by ASTM D5470; effective thermal conductivity is generally 1.5–2.5 W/(m·K) in this filler range, but published data for this specific RH-Vi1311 configuration is limited.Processing uses a two-component cartridge or drum pump feeding a static mixer, with vacuum deairing at 5–10 mbar. The mixed compound is dispensed into preheated aluminium housings at 70–90°C, then cured at 80°C for 30 min and post-cured at 150°C for 1 h. Adhesion to aluminium and copper requires a silane primer; primerless adhesion should not be assumed because low-stress silicones pull away at sharp metal-polymer interfaces. Terminal products are insulated-gate bipolar transistor modules, onboard charger potting, and inverter busbar insulation.

Standard or regulation	Method or clause	Requirement applied to cured RH-Vi1311 compound
RoHS Directive 2011/65/EU	Annex II restricted substances	Pb, Hg, Cr(VI), PBB, PBDE each ≤ 0.1 wt%; Cd ≤ 0.01 wt% in homogeneous material
REACH Regulation (EC) No 1907/2006	SVHC Candidate List	No intentionally added SVHC above 0.1 wt% in article
UL 94	V-0 vertical burn, 2 × 10 s flame applications	Cured potting compound must self-extinguish without cotton ignition
ASTM D5470	Guarded heat flow meter method	Thermal impedance and effective thermal conductivity of filled material
IPC-CC-830B	Conformal coating qualification	Cured coating hardness, hydrolytic stability, flammability class

What Limits Cure Time in a Cold-Runner Liquid Silicone Rubber Mould When RH-Vi1311 Is the Low-Viscosity Vinyl Component?

The limiting parameter in liquid silicone rubber injection moulding is not the platinum hydrosilylation rate alone but heat transfer through the steel cavity to the core of a thick section. RH-Vi1311 is blended at 5–15 wt% with a high-molecular-weight vinyl-functional gum and 20–35 wt% fumed silica to lower mixed viscosity to 80–150 Pa·s at 10 s⁻¹, measured by DIN 53019. The A and B components are pumped at a 1:1 volumetric ratio; actual stoichiometry is set by a separate Si-H crosslinker in B. Mould temperature is held at 160–190°C. At 180°C, a 2 mm plaque reaches 90% of ultimate torque in 60–90 s, but demoulding before 30 s can cause tear at the parting line because the low-viscosity fraction lowers green strength. If the RH-Vi1311 loading exceeds 20 wt%, Durometer A hardness may fall below 30 and tensile strength may fall below 5 MPa, measured by ASTM D412, and the part tends to bubble when cavity pressure falls below 0.3 MPa. The processing window for RH-Vi1311 as a diluent is therefore 5–15 phr in this configuration. Cure time can be shortened to 20–30 s with 200°C post-cure for 4 h to complete crosslinking and remove residual volatile cyclics.

Terminal products include automotive connector seals, oxygen mask valves, infant bottle nipples, and medical respiratory diaphragms. Medical grades must pass ISO 10993-5 and USP Class VI extraction; food-contact articles are evaluated under FDA 21 CFR 177.2600 and EU 1935/2004. Platinum catalyst activity is sensitive to sulfur, amines, and tin salts; any release agent or pigment containing these species should be excluded from the moulding area because zero-cure patches cause high reject rates.

When a Low-Viscosity Vinyl Fluid Replaces a Long-Chain Vinyl Polymer in Solventless Release Coatings

Solventless release coating of machine-glazed kraft or PET liner becomes feasible when the vinyl polymer is diluted with 10–30 parts RH-Vi1311 per 100 parts high-molecular-weight vinyl silicone polymer. The oil reduces coating bath viscosity to 400–800 mPa·s at 25°C, permitting transfer-based coating at 100–300 m/min without solvent recovery. The coating is compounded with a methylhydrogen crosslinker at an Si-H:Vi molar ratio of 1.5–2.0:1 and a platinum catalyst level of 80–120 ppm, then cured in forced air at 150–180°C for 5–10 s. Excess Si-H above 2.5:1 may raise crosslink density but can increase extractable methylhydrogen content and cause unstable release force after ageing. Release force against a pressure-sensitive acrylic adhesive is typically 10–40 cN/25 mm, measured by FINAT FTM 3 at 180° peel. Bath stability at 25°C is 8–24 h depending on inhibitor selection; a pre-gelled layer forms in the return pan if the coating head is exposed to heat above 35°C. Published data for this specific RH-Vi1311 grade in a PET release liner is limited; the cited release range represents general solventless silicone systems. Finished liners are slit for hygiene, label, and PSA tape applications. Compliance for food packaging liners requires the cured coating to meet FDA 21 CFR 175.320 for resinous and polymeric coatings, and EU 10/2011 where food contact is declared.

Two-Roll Mill Compounding and Filler Wetting with Reactive Vinyl Oil

On a two-roll mill with a 0.4–0.7 mm nip gap and a roll temperature of 30–40°C, high-consistency silicone rubber containing RH-Vi1311 is compounded by adding the oil at 5–10 phr relative to a high-molecular-weight vinyl-containing gum before fumed or precipitated silica is incorporated. The low-molecular-weight telechelic chains adsorb onto silica silanol groups and reduce hydrogen-bonding structuring during storage; this effect is measured as a lower Mooney viscosity ML 1+4 at 100°C according to ISO 289-1. A formulation with 5 phr RH-Vi1311 and 35 phr fumed silica typically shows a Mooney drop of 15–25 units relative to the same silica loading without the oil, but this value depends on silica surface area and residual moisture. The compound is peroxide-cured with 1.0–2.0 phr dicumyl peroxide or 0.8–1.5 phr 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane at 165–175°C in a compression mould. Because RH-Vi1311 has terminal vinyl groups, it is not a fugitive plasticizer; it is co-crosslinked into the network, so extraction in n-hexane is lower than with trimethylsilyl-terminated dimethylsilicone oil. Tensile strength and tear resistance are measured according to ASTM D412 and ISO 34-1 Die C; compression set is measured under ISO 815-1 at 150°C for 22 h. If the amount of RH-Vi1311 exceeds 15 phr, tear strength may decline below 8 kN/m and the mill band may become too tacky to process at ambient humidity above 60%.

Finished products include extruded door seals, oven gaskets, vibration dampers, and keypads. Food-contact gaskets require FDA 21 CFR 177.2600; automotive grades are assessed under ISO 3795 or FMVSS 302 for flammability. Batch-to-batch variance in silica moisture changes the measured Mooney drop by ±5 units; silica must be pre-dried at 150°C for 2 h when relative humidity exceeds 60%.

Published data for RH-Vi1311 in wound-contact silicone gel sheeting is sparse; the following processing boundaries are therefore limited to general addition-cure gel chemistry of vinyl-telechelic oils. A two-part gel is formulated at an Si-H:Vi ratio of 0.45–1.00:1 to give a soft tacky network with a penetrometer depth of 3–8 mm on a standard 1/4-scale cone. The platinum catalyst loading is reduced to 2–5 ppm to avoid excessive exotherm in thin-section casting at 100–120°C for 10–20 min. Part A contains RH-Vi1311 and a vinyl-functional MQ resin; Part B contains the Si-H crosslinker and the catalyst, but the inhibitor must be selected to avoid skin-sensitizing residues. The cured gel is post-cured at 150°C for 4 h under forced ventilation to reduce residual cyclic siloxane below 0.1 wt%, a level relevant to ISO 10993-18 chemical characterization. Residual platinum can cause discolouration under ethylene oxide sterilization if not removed. Cytotoxicity is evaluated under ISO 10993-5, sensitization under ISO 10993-10, and implantation under ISO 10993-6 where the gel remains in contact with breached skin. Crosslinker incompatibility with amine-containing drugs or antiseptics must be checked, because amines can poison the platinum catalyst and leave uncured wet vinyl oil on the surface. Terminal products are wound contact layers, scar treatment sheets, and silicone interface dressings.

Directly pre-treating fumed silica with RH-Vi1311 in a horizontal ploughshare mixer at 110–140°C for 2–4 h under nitrogen reduces the oil absorption number and stabilizes the thixotropic index of an RTV-2 silicone sealant. The silica charge is 150–200 m²/g BET surface area; the RH-Vi1311 addition is 20–30 parts per 100 parts silica. The mixer tip speed is 40–60 m/s. After cooling, the treated silica is dispersed into a methoxy-terminated or hydroxy-terminated polydimethylsiloxane base at 8–12 wt% to achieve a paste viscosity of 400,000–800,000 mPa·s at 0.1 s⁻¹. Because RH-Vi1311 is non-alkoxy, it is not chemically bonded to the silica surface at these temperatures; a portion remains physically adsorbed, which can migrate to the bulk during storage and alter slump after three months. For this reason the treated filler must be aged at 25°C for 24 h before rheological testing. The terminal product is a neutral alkoxy RTV-2 adhesive for construction glazing and electronic edge bonding. Sealants for food-contact use are not recommended with this pre-treatment unless extraction is verified under FDA 21 CFR 177.2600. High humidity above 70% during filler discharge may cause re-adsorption of water onto residual silanol groups, reducing the hydrophobization effect.