Vinyl Terminated Silicone Oil RH-Vi1324

In two-component addition-cure liquid silicone rubber (LSR) injection molding, low-viscosity vinyl-terminated polydimethylsiloxane is introduced as a reactive diluent in both Part A and Part B to reduce dynamic viscosity below 500 Pa·s at 25 °C and enable filling of 0.2 mm wall sections in multi-cavity cold-runner tooling. When RH-Vi1324 replaces 15–30 phr of a high-viscosity vinyl-terminated gum, the mixed viscosity measured by rotational rheometry at 10 s⁻¹ decreases from approximately 1,900 Pa·s to 450–620 Pa·s, while Shore A hardness after 10 min at 150 °C falls from roughly 55 at 0 phr to 36–44 at 15–25 phr and to 30 at 35 phr, depending on the SiH/SiVi molar ratio. Addition above 35 phr produces measurable surface tack and lowers tensile strength below 5 MPa because the sol fraction in the cured network rises above 8%, a level associated with high extractables and increasing compression set. Batch-to-batch viscosity variation of ±10% in the incoming vinyl fluid shifts the mixed LSR viscosity by ±5–8%; on a 40-cavity cold-runner mold this produces shot weight drift of 2.5% and intermittent flash at the parting line when injection pressure is held constant. If the oil contains residual moisture above 150 ppm, the addition cure can foam during the 150 °C cavity dwell because water is released at the melt front; pre-drying at 80 °C for 2 h under 20 kPa is required when storage conditions exceed 60% relative humidity. The metered mixing step uses a static mixer with 8–12 elements to deliver shot volume repeatability of ±0.8%; the compound is injected into a cold-runner mold held at 120–160 °C, with cure times of 30–90 s/mm of wall thickness. In continuous production on 150–250 t vertical LSR machines with 18:1–22:1 plasticating units and 40–80 °C water-cooled barrels, pot life at 25 °C is maintained at 48 h by adding 0.05–0.15 wt% 1-ethynyl-1-cyclohexanol inhibitor; material held beyond 72 h shows a 10–15% increase in injection pressure at the same shot size because of progressive crosslinking on the hydride side. Amine-based mold release agents and sulfur-containing residues inhibit the platinum catalyst and leave glossy uncured patches. Food-contact parts require FDA 21 CFR 177.2600; medical parts are evaluated under ISO 10993-5 and USP Class VI. The finished moldings are supplied as automotive connector seals, baby bottle teats, sanitary diaphragms, insulin pump gaskets, and electronic module seals. Representative formulation data are summarized in the following table; values were determined after post-curing 4 h at 200 °C.

What changes when 1,000 mPa·s vinyl PDMS is compounded into peroxide-cured HCR on a two-roll mill?

The shift from a high-molecular-weight vinyl gum to a 1,000 mPa·s vinyl-terminated fluid changes mill behaviour because the low-viscosity oil acts as a processing plasticizer before the free-radical crosslinking reaction fixes it into the siloxane network. In peroxide-cured high-consistency silicone rubber (HCR), RH-Vi1324 is added at 3–10 phr during the two-roll mill compounding step. At this addition level, the Williams plasticity of a 40 Shore A base compound drops by approximately 20–40 mm under ASTM D926 conditions, but mill roll temperatures must stay below 50 °C to prevent the silane-modified fumed silica surface from developing bound structures prematurely. If the addition exceeds 10 phr, the cured sheet shows a 20–30% increase in volume swell in ASTM D471 reference fuel B, and compression set measured to ISO 815-1:2014 may exceed 35%. The downstream production process typically involves a 40–60 °C two-roll mill for masterbatch preparation, followed by a single-screw extruder with an L/D ratio of 12:1–16:1 and a crosshead die for wire insulation or a pin-and-cylinder die for tubing. Continuous hot air vulcanization at 200–250 °C cures the 0.5–1.2 phr 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane peroxide system within 60–120 s depending on wall thickness. Flame-rated applications require UL 94 V-0 testing on the finished insulation wall; thermal endurance is assessed by IEC 60216-1 at 200 °C for 20,000 h. The primary downstream articles are silicone-insulated appliance wire, oven door gaskets, charge air cooler sleeves, and high-temperature protective tubing.

When RH-Vi1324 is used as the base polymer in a hydrosilylation-curing soft gel for power electronics, the formulation is prepared from 100 parts by weight of the vinyl-terminated fluid, 4–8 parts of a poly(methylhydrogen)siloxane crosslinker, and 1–3 ppm of platinum delivered as a Karstedt catalyst complex. Pot life at 25 °C is 8–12 h without additional inhibitor; with 0.02–0.05 wt% 1-ethynyl-1-cyclohexanol, pot life extends to 48 h while the exotherm peak measured by differential scanning calorimetry shifts from 55 °C to 73 °C. The vacuum deaeration step at 20–50 Pa removes air bubbles that would otherwise create partial discharge sites under 3–5 kV test conditions. Potting is performed at 1–5% absolute chamber vacuum, followed by a cure cycle of 2 h at 65 °C for large modules; lower-temperature 24 h room-temperature cure is used for temperature-sensitive substrates. The cured gel typically exhibits a cone penetration of 60–100 × 0.1 mm by an adapted penetrometer method and a dielectric strength above 18 kV/mm by ASTM D149; conductive residues from solder flux and certain nitrogen-containing epoxy compounds can inhibit the platinum catalyst and produce a tacky surface layer. Electrical protection requires IPC-CC-830B for conformal coating qualification, UL 94 V-0 for flammability of the final assembly, and IEC 60068-2-14 thermal cycling from -40 °C to 125 °C for 1,000 cycles. End-use assemblies comprise EV onboard charger modules, IGBT driver potting, LED drivers, and industrial power supply units.

Solventless release coating cure window, misting threshold, and adhesion loss across 1.0–2.5 g/m² deposits

On a five-roll solventless coater running a polyethylene-coated kraft liner, the cure window is set by the molar ratio of silicon hydride to silicon vinyl, not solely by oven temperature. RH-Vi1324 is used as the primary vinyl-functional component at 100 parts by weight, with a methylhydrogen polysiloxane crosslinker at 12–20 parts to maintain an SiH/SiVi ratio of 1.4–1.8. Platinum catalyst concentration is 80–120 ppm based on total bath weight. The coating is applied at 1.0–2.5 g/m² and cured in a 120–150 °C forced-air tunnel with a residence time of 8–20 s; line speeds up to 400 m/min are possible only when the formulation contains a mist-control additive and the roll gap is adjusted to avoid shear stress above 15,000 s⁻¹. A deposit below 1.0 g/m² creates pinholing and adhesive z-displacement; above 2.5 g/m², unreacted silicone can transfer to the pressure-sensitive adhesive and reduce 180° peel force by more than 35% after 7 days of ageing at 40 °C. For food-contact release liners, the finished coating must comply with FDA 21 CFR 176.170 and EU 10/2011 where applicable; industrial release liners are typically evaluated by FINAT FTM 3 for peel and FINAT FTM 10 for subsequent adhesion. Commercial outputs from this process include pressure-sensitive label liners, double-sided tape release films, hygiene article backing films, and transfer tape carriers.

Textile-grade silicone ink requires controlled hydrosilylation rate, not merely a fast flash cure

The observable failure on a production screen-printing line is not incomplete cure but a rise in surface fibrillation and a drop in elongation after repeated laundering. In textile silicone ink, RH-Vi1324 is used at 55–75 wt% of the total formulation together with 5–10 wt% hydride crosslinker, 0.5–1.0 wt% platinum catalyst, 5–12 wt% fumed silica matting filler, and 0.05–0.2 wt% inhibitor. Flash cure at 110–130 °C for 30–60 s is sufficient only for skin-over; full crosslink density requires a tunnel cure at 150 °C for 3–5 min. Printing through 48–80 mesh screens provides a deposit weight of 200–400 g/m² on cotton and polyamide fabrics. Oeko-Tex Standard 100 Class I compliance is required for infants and toddlers, and the final printed article must meet REACH EC 1907/2006 Annex XVII and CPSIA lead and phthalate limits for children’s products. Published data for RH-Vi1324-specific adhesion to nylon 6,6 after 50 domestic wash cycles is limited; however, the open time/temperature relationship follows hydrosilylation kinetics typical for 1,000 mPa·s vinyl PDMS. The printed textile articles produced are sports sock grip prints, silicone garment patches, bra strap anti-slip strips, and decorative wearable labels.

When a soft skin adhesive is coated on polyurethane liners, the platinum cure may fail without a barrier tie layer

During pilot coating trials on a 500 mm wide knife-over-roll coater, platinum cure inhibition was observed when a soft skin adhesive based on RH-Vi1324 was coated directly onto polyurethane liners without a fluorinated release interface. The adhesive formulation comprises 100 parts by weight RH-Vi1324, 30–60 phr MQ silicate resin, 1.5–3.0 phr poly(methylhydrogen)siloxane crosslinker, and 20–40 ppm platinum. The mixture is stirred in a swept-blade mixer at 80 °C for 30 min, then vacuum-stripped at 20–50 Pa to remove volatiles before coating at 100–500 g/m² onto a fluorinated release liner. Cure is completed at 100 °C for 10 min; exposure of the unreacted adhesive to polyurethane laminating films containing organotin catalysts can leave a tacky gel surface and would fail the cytotoxicity evaluation under ISO 10993-5 because of elevated extractables. Medical-grade qualification includes ISO 10993-5 for cytotoxicity, ISO 10993-10 for skin sensitization, and USP <88> Class VI systemic injection testing. The cured adhesive is designed for low skin trauma removal, with a 180° peel force to steel of 1–6 N/25 mm by FINAT FTM 1. Representative medical device outputs are scar treatment silicone sheets, ostomy appliance flanges, wearable sensor adhesive rings, and kinesiology tape edge strips.