Vinyl Terminated Silicone Oil RH-Vi1324

In liquid silicone rubber injection moulding, RH-Vi1324 is proportioned into a two-component platinum-catalysed formulation as the vinyl-functional polysiloxane. The Part A stream contains the vinyl polymer, a polymethylhydrogensiloxane crosslinker, and fumed silica; Part B contains the vinyl polymer, platinum-divinyltetramethyldisiloxane complex at 5–10 ppm Pt, and 1-ethynyl-1-cyclohexanol as the pot-life inhibitor. Metering of the two streams at a fixed 1:1 ratio is carried out by a gear pump, followed by static mixing with 8–12 elements. The blend is cooled to 18–25°C before injection to suppress premature gelation. On a 1,600 kN clamp-force injection moulding press, the shot is injected into a closed tool at 150–190°C; cure time is adjusted from 30 s to 90 s depending on wall thickness. The Si-H:Si-Vi ratio is held between 1.2:1 and 1.8:1. Ratios below 1.0:1 produce surface tack and low crosslink density, while ratios above 2.0:1 cause hydrogen evolution, gas entrapment, and premature embrittlement. The cured material is evaluated by ASTM D2240 for durometer, ISO 37:2017 for tensile strength and elongation, and ISO 815-1:2019 for compression set after 22 h at 175°C. For a 40 Shore A moulding composition, tensile strength typically falls between 7.0 MPa and 10.0 MPa, elongation at break between 400% and 700%, and compression set from 15% to 30% without post-cure. Process drift is observed on high-speed moulding lines when the Pt concentration is reduced below 3 ppm to extend pot life; mould release force then rises and surface cure becomes sensitive to ambient sulphur contamination. The terminal articles are infant-care nipple hoods, pump diaphragms, and electrical connector seals.

What Limits the Si-H:Si-Vi Ratio in Platinum-Catalysed Release Coatings?

Solventless silicone release coating systems are formulated with RH-Vi1324 as the vinyl donor to control crosslink density and release force. The coating bath is prepared by blending the vinyl silicone oil with a polymethylhydrogensiloxane crosslinker to an Si-H:Si-Vi ratio of 1.4:1 to 1.8:1, a platinum catalyst concentration of 30–100 ppm Pt, and a vinyl-functional MQ resin when tighter release is required. The mixture is applied by five-roll offset coating at 0.8–1.2 g/m² to polyester or glassine substrates. Thermal cure in an air flotation oven at 120–160°C with dwell times of 5–15 s produces a crosslinked film without solvent. Crosslinker starvation below 1.2:1 leaves unreacted vinyl species that migrate into acrylic or rubber pressure-sensitive adhesives and lower peel strength after lamination. Crosslinker excess above 2.0:1 generates residual Si-H groups that undergo secondary reactions with ambient moisture, raising release force over time. Release performance is tested using FINAT FTM 3 on a tensile tester at 180° peel angle and 300 mm/min; controlled addition of MQ resin shifts release from 5–10 cN/25 mm low-force release to 30–60 cN/25 mm tight release. The terminal product is a release liner for pressure-sensitive label stock, single-sided industrial tapes, and medical adhesive carriers.

Encapsulation of insulated-gate bipolar transistor modules and power converters with silicone gels uses RH-Vi1324 in a two-part addition-cure system where pot life and dielectric performance are coupled to the vinyl-hydride ratio. The A component is a blend of RH-Vi1324, a hydride crosslinker, and an alkynol inhibitor; the B component contains the same vinyl polymer and a platinum-cyclovinylmethylsiloxane complex at 5–20 ppm Pt. The components are metered at 1:1, mixed under vacuum at 30–50 mbar, and dispensed into the module housing at 50–80°C to lower viscosity. Cure is carried out at 80–120°C for 30–60 min. The Si-H:Si-Vi ratio is set at 1.5:1 to 2.0:1 to balance softness and extractables. The mixed viscosity is adjusted to 500–1,000 mPa·s at 25°C. The cured gel hardness is checked with a 1/4-scale cone penetrometer per ASTM D1403, with penetration values typically 6.0–8.5 mm. Dielectric strength is tested according to IEC 60243-1 on 2 mm sheets, with typical values 14–18 kV/mm before thermal ageing. Pot life at 25°C is extended to 4–8 h by adjusting inhibitor concentration, but adding more than 0.05 wt% of 1-ethynyl-1-cyclohexanol retards cure below 100°C and raises the coefficient of thermal expansion after gelation. Fumed silica is added at 0.5–2.0 wt% when thixotropic dispensing is needed; above 3.0 wt% filler the gel loses transparency and trapped bubbles become difficult to remove under vacuum. Fumed silica should be pre-dried at 120°C for 2 h when ambient relative humidity exceeds 60%. The encapsulant must be stored and dispensed away from amine-cured epoxy surfaces, sulphur-vulcanized rubber gaskets, and metal soaps, which poison the platinum catalyst. The terminal use is an optically clear stress-relief layer for wire-bonded power modules and automotive motor-drive electronics.

HTV Extrusion Lines Running RH-Vi1324-Modified Silicone Compounds

High-consistency silicone rubber compounds for extruded profiles and automotive coolant seals are prepared with RH-Vi1324 as a reactive processing fluid to lower compound viscosity and adjust crosslink density. On a two-roll mill at 35–45°C, 100 phr high-consistency vinyl-terminated silicone gum is blended with 20–40 phr fumed silica, 3–6 phr precipitated calcium carbonate, and RH-Vi1324 at 5–15 phr. The addition-cure package includes a methylhydrogenpolysiloxane crosslinker at an Si-H:Si-Vi ratio of 1.3:1 to 1.6:1 and a platinum-alkenyl complex at 0.5–1.0 ppm Pt. The compound is fed through a cold-feed extruder with L/D 24:1 and a barrel temperature profile from 20°C at the feed zone to 40°C at the head, then through a salt-bath or hot-air tunnel at 250–400°C for 20–60 s. Crosslink density is increased by post-curing at 200°C for 4 h to remove volatile by-products. Hardness is controlled by the ratio of RH-Vi1324 to filler and measured by ASTM D2240, with typical values from 25 Shore A to 50 Shore A. Tensile strength is tested to ISO 37:2017, and tear strength to DIN ISO 34-1. For a 30 Shore A coolant-seal compound, tensile strength is generally 6.0–8.0 MPa, elongation 350–550%, and tear strength 12–18 N/mm. A process conflict arises when RH-Vi1324 loading exceeds 15 phr in filled compounds: the extrudate swells and loses green strength before curing, requiring screw speed below 30 rpm on a 45 mm extruder. The terminal products are radiator seals, oven-door gaskets, and ignition cable jackets.

When Hydrogen-Blow Foaming Shifts Density and Cell Structure in Silicone Sealing Profiles

Silicone foam tapes and gaskets are produced with RH-Vi1324 as the vinyl-terminated fluid in an addition-cure, hydrogen-blown system. The formulation combines 100 parts vinyl silicone oil, 5–20 parts hydride-terminated or pendant-hydride polysiloxane, 0.5–2.0 parts distilled water or short-chain hydroxy silicone fluid, and a platinum catalyst at 10–20 ppm Pt. The onset of hydrogen evolution begins when the mixed compound reaches 40–60°C; simultaneous crosslinking and gas nucleation must be balanced to avoid coalescence. The material is dispensed into closed or open moulds and cured at 80–120°C for 10–30 min. Density is controlled from 0.25 g/cm³ to 0.60 g/cm³ by varying the hydride-to-hydroxyl ratio and the mixing vacuum level; density is measured by ASTM D792 or ISO 1183-1:2019. Cell structure is characterized by cross-section microscopy, and compression set is evaluated according to ISO 815-1:2020 after 50% compression at 100°C for 22 h. For flame-retardant sealing profiles, alumina trihydrate is added at 40–80 phr, but the formulation becomes shear-thinning and requires a rotor-stator mixer at 1,000–2,000 rpm before compounding. The foam meets UL 94 V-0 at 3 mm thickness when the alumina trihydrate loading is above 60 phr, although tensile strength drops below 0.8 MPa. The main process failure is cell collapse caused by adding water above 2.0 phr or by curing below 80°C, which leaves unreacted Si-H groups that continue to evolve hydrogen during storage. Terminal goods are cell-closed edge-seals for battery enclosures, HVAC gaskets, and railcar window profiles.

RH-Vi1324 is used in compression moulded silicone keypad compounds where durometer, contact fatigue, and residual peroxide content are controlled simultaneously. The compound is mixed in a kneader at 30–40°C with 100 phr vinyl polymer, 25–40 phr fumed silica, 2–5 phr MQ resin, and a platinum cure package at 0.5–1.0 ppm Pt. The Si-H:Si-Vi molar ratio is held at 1.4:1 to 1.7:1; higher hydride levels produce compression set below 15% but reduce elongation below 250%. The compound is sheeted to 2–5 mm thickness and compression moulded at 150–170°C for 5–10 min under 8–12 MPa moulding pressure. Durometer is checked by ASTM D2240, with typical values between 30 Shore A and 60 Shore A. Tear strength is measured by DIN ISO 34-1, elongation by ISO 37:2017, and rebound resilience by ISO 4662:2017. Keypad buttons produced from the compound are subjected to 1,000,000 cycles of actuation at 25°C; the force-displacement curve retains 80% of initial peak force when the Si-H:Si-Vi ratio is above 1.4:1. A production bottleneck occurs with high-hardness formulations above 60 Shore A: filling the microcavities requires mould temperatures above 160°C and prolonged flow time, but the compound skin-cures on the heated tool after 60 s, causing knit lines. The terminal articles are membrane switches, calculator keypads, and industrial control-panel buttons.