Vinyl Terminated Silicone Oil RH-Vi301

In injection-molded liquid silicone rubber for infant feeding closures, vinyl-terminated silicone fluid RH-Vi301 functions as the difunctional reactive diluent and crosslinkable chain extender in the A-component. The fluid is supplied with a terminal vinyl content of 0.18–0.26 mmol/g and a neat viscosity of 1,000–5,000 mPa·s at 25°C. This viscosity permits filler wetting at shear rates below 100 s⁻¹ while retaining low pressure drop through the cold runner. The compound is prepared in a planetary mixer with a vacuum of -0.095 MPa for 45–60 min, using 15–25 wt% untreated fumed silica with a BET surface area of 200–300 m²/g and a hydride-functional siloxane with a Si-H content of 0.5–1.0 mmol/g. The B-component is metered to maintain a Si-H:Si-Vi molar ratio between 1.4:1 and 1.8:1. Below 1.3:1 the cured network retains surface tack and shows low tear strength. Above 2.0:1 excess hydride increases crosslink density, raises 100% modulus above 0.8 MPa, and reduces elongation at break below 400%. The mixed material is injected on an all-electric injection molding machine with a clamp force of 1,500–2,500 kN, a shut-off nozzle, and a cold-runner block held at 18–22°C. Mold temperature is set at 110–130°C in the cavity plate. Cure time for a 2.0 mm wall thickness part is 40–70 s; a 0.5 mm membrane cures in 20–35 s. On-line failure modes include cold-runner slugging, flash formation at the tear strip, and static mixer scorch when the mixed material temperature exceeds 40°C. Post-curing in a forced-convection oven at 160–180°C for 4 h reduces volatile siloxanes. Residual extractables are evaluated by water reflux for 6 h and must comply with FDA 21 CFR 177.2600 and the overall migration limits specified in Regulation (EU) No 10/2011 for food-contact articles. Tensile properties are measured according to ISO 37:2017, and tear resistance is measured according to ASTM D624 die C.

The following property gradient is observed after curing 2.0 mm sheets at 120°C for 10 min followed by post-cure at 180°C for 4 h:

What Limits Platinum Activity in Solventless Release Coatings on Clay-Coated Kraft?

Solventless release coating for pressure-sensitive label liners is prepared with RH-Vi301 as the lower-viscosity vinyl partner in a two-part addition-cure system. The fluid is blended at 40–60 wt% of the coating solids with a vinyl-functional MQ resin at 20–35 wt% and a hydride crosslinker at 10–20 wt%. The target Si-H:Si-Vi molar ratio is 1.8:1 to 2.5:1 because the porous clay-coated kraft surface consumes hydride at exposed mineral edge sites and must be saturated before the siloxane network closes. Platinum complex concentration in the bath is held at 80–120 ppm. Below 60 ppm, cure inhibition on acidic clay is visible as a carbon-solvent extractable silicone fraction above 5%. Application is performed with a five-roll offset gravure coater at line speeds from 300 m/min to 600 m/min. Coat weight is maintained at 0.8–1.2 g/m² by controlling the differential speed between the metering roller and the application roller. The coated web passes through a three-zone air float dryer with zone temperatures set at 120°C, 150°C, and 170°C. Residence time in the final zone is 2–5 s. Release force is measured according to FINAT FTM 4 on a 25 mm wide strip at 300 mm/min peel speed after 24 h aging at 20°C and 50% RH. A premium-grade liner is specified at 8–20 cN/25 mm. Operational limitations include platinum poisoning by residual sulfides from the kraft sheet and starry speckle defects when the bath temperature exceeds 35°C for 6 h. The coating bath is jacketed to 18–22°C and kept under nitrogen to limit moisture uptake, because water at 0.05% in the bath shortens pot life from 24 h to 6 h.

For high-voltage IGBT module encapsulation gels, RH-Vi301 is selected as the low-viscosity vinyl donor because the absence of free silanol chain ends reduces post-aging dielectric loss. The gel is formulated at a Si-H:Si-Vi molar ratio of 0.9:1 to 1.15:1. The deliberate vinyl excess prevents progressive hardening when the module operates at 150°C junction temperature for 1,000 h. The uncured mixed viscosity is adjusted to 400–900 mPa·s at 25°C by controlling chain extender length and blending with a low-vinyl dimethyl siloxane. The two components are transferred through a 24-element static mixer into a vacuum degassing chamber at -0.098 MPa. Pot life under vacuum is 20–30 min at 25°C. Dispensing into the module housing is performed with a needle valve at a feed pressure of 0.6 MPa to avoid air entrapment. Thermal cure is staged at 70°C for 30 min followed by 120°C for 60 min. The cured gel has a Shore 00 hardness of 20–50 by ASTM D2240-15 and a dielectric breakdown strength of 18–22 kV/mm on a 2.0 mm sheet tested according to IEC 60243-1:2013. Ionic extractables are controlled by washing the silicone precursor with propylene carbonate and by specifying platinum catalysts with no residual amine ligands. The gel is incompatible with polyimide flexible circuits that contain free amine-based adhesion promoters; even 50 ppm of freely migrating amine can quench platinum activity and leave a tacky interfacial layer. Production-scale dispensing lines monitor the gel height in the module via laser triangulation. Voids larger than 0.5 mm are rejected because they reduce partial discharge inception voltage under IEC 60664-1.

When Alumina Particle Size Distribution Narrows Below 5 μm in Gap-Filler Mixing

Thermally conductive gap filler for automotive ECU housings is formulated with RH-Vi301 as the reactive binder and a bimodal alumina filler system. Filler loading is maintained between 82 wt% and 92 wt%. The coarse alumina has a D50 of 30 μm, and the fine alumina has a D50 of 2.0 μm. The fine fraction raises uncured complex viscosity. At 1 s⁻¹ batch viscosity exceeds 1,200 Pa·s when the fine fraction is above 55% of total filler. Dispersion is executed in a planetary mixer with a jacket temperature of 25–30°C, a vacuum of -0.09 MPa, and a blade tip speed limited to 2.5 m/s to avoid breaking the hydride coupling agent shell. Mixing time is 60–90 min. Batch size influences frictional heat and requires water cooling to prevent local gelation at 45°C. The two-part mixture is dispensed through a progressive cavity pump with a 12-element static mixer. Shot sizes in ECU housings range from 30 cm³ to 120 cm³. Cure is 80°C for 30 min plus 120°C for 60 min. The cured gap filler has thermal conductivity of 2.5–5.0 W/m·K by ASTM D5470-17 and a flame retardancy rating of UL 94 V-0 at 1.5 mm thickness. Finished pads are cut to thicknesses between 0.5 mm and 5.0 mm and are placed between power semiconductor modules and liquid cooling plates. Pump stator wear is the dominant failure mode. The abrasive alumina fraction causes rotor/stator clearance growth after 500–800 shots, detectable as a drop in shot-weight repeatability from ±0.15 g to ±0.40 g. Formulators counter this by specifying carbide-coated rotors and by replacing stator elastomers after 2,500 shots. The addition of an internal release agent is limited to 0.2–0.5 phr; higher levels migrate to the interface and reduce thermal contact conductance.

Before specifying RH-Vi301 in lithium-ion battery pack compression foam, the hydrogen evolution profile must be matched to the open-cell formation window. Low-density silicone foam is produced from a two-part addition-cure composition containing RH-Vi301, a hydride-functional siloxane, water at 0.3–1.0 phr, a platinum inhibitor, and fine fumed silica. The vinyl fluid is used to control the initial mixed viscosity between 4,000 mPa·s and 12,000 mPa·s, which sets the foam rise rate and cell size. Mixing is performed in a low-pressure meter-mix dispense system with a disposable static mixer. The material is deposited into aluminum compression molds held at 60–90°C. Demolding occurs at 20–40 min. Foam density is controlled at 0.18–0.35 g/cm³ by adjusting water concentration and mold fill ratio. The finished foam compression pads sit between prismatic cells and the battery pack wall. They maintain a compression force of 0.5–2.0 N/cm² over 30% deflection and provide thermal insulation and mechanical isolation. Compression set after 22 h at 100°C is ≤ 5.0% per ISO 1856:2018. Flame retardancy is rated UL 94 V-0 at 2.0 mm, and limiting oxygen index is 28–34% by ISO 4589-2:2017. When the hydride ratio exceeds 2.0:1, the foam develops a closed-cell content above 60%, increasing compression load deflection and reducing cell gas diffusion. This causes permanent compression set to exceed 12% after 1,000 load cycles.

Filler Dispersion and Coupling Agent Demand in Extruded Silicone Profiles

High-consistency silicone rubber for automotive charge-air hose liners uses RH-Vi301 as a reactive viscosity modifier and co-curing plasticizer in a methyl vinyl gum matrix. Addition level is 3–8 phr. At 3 phr the compound Mooney viscosity, ML 1+4 at 100°C, drops from 70 MU to 52 MU; at 8 phr the drop is to 45 MU. Compounding is carried out in a kneader with a fill factor of 70% and a ram pressure of 0.4 MPa. Precipitated silica is added at 35–45 phr with 3–5 phr of phenyltrimethoxysilane coupling agent. The water byproduct from coupling agent hydrolysis is vented under vacuum below -0.09 MPa. The compounded stock is extruded on a single-screw extruder with L/D 20:1, feed zone temperature 20–30°C, compression zone 35–45°C, and die head 45–55°C. Addition cure is completed in a hot-air vulcanization tunnel at 250–300°C for 1–2 min. The extruded charge-air hose liner is tested for compression set after aging at 175°C for 22 h; the specification is ≤ 25% per ISO 815-1:2014. Elongation at break is ≥ 500% by ISO 37:2017. When the fluid level exceeds 10 phr, low-viscosity material migrates to the surface during storage, producing a visible bloom and reducing tack-free adhesion to the reinforcement layer. Surface exudation is measured by wiping a 100 cm² sample with a white lint-free cloth and weighing the nonvolatile residue. Acceptable residue is below 0.5 mg.