Vinyl Silicone Resin S19160

In two-part platinum-catalysed encapsulant systems for insulated-gate bipolar transistor modules, LED leadframe arrays and automotive engine-control units, S19160 is first dispersed into the vinyl-terminated polydimethylsiloxane carrier under moderate heat and low-shear planetary mixing. A 30 L planetary mixer with a 1.5 m/s tip speed is typical for production batches: the resin is sheared at 40–60°C for 45–90 min until Phase A is visually clear and the Hegman grind is below 15 µm. S19160 does not function as a passive diluent in this system. The vinyl substituents on the MQ resin enter the hydrosilylation network as reinforcement nodes, increasing crosslink density after platinum-catalysed cure. Raising the S19160 fraction from 15 phr to 35 phr in an alumina-filled compound typically shifts the cone-plate viscosity from approximately 1,200 mPa·s to 4,800 mPa·s at 25°C by DIN EN ISO 3219:1994. The resulting viscosity increase narrows the processing window on 10:1 meter-mix dispensing equipment: incomplete edge fill occurs in 40-pin QFN frames when the mixed viscosity at the dispensing head exceeds 8,000 mPa·s. For that reason the resin loading is held at the lower end of the range when the total inorganic filler content is above 80 wt%. Published product-level data for S19160 in this exact package configuration is limited; the processing constraints given here are consistent with vinyl-functional MQ resin behaviour as a class rather than a batch-specific test report.

Cure of S19160-containing encapsulants is normally staged. A first zone at 100–120°C for 10–15 min establishes gelation and arrests filler migration, followed by a second zone at 150°C for 1–2 h to complete hydrosilylation. Residual cure exotherm measured by differential scanning calorimetry according to ISO 11357-2:2020 should fall below 5 J/g for production acceptance; a higher value indicates unreacted vinyl or hydride sites and correlates with drift in Shore D hardness after thermal cycling. Filler settling in the feed tank remains the dominant batch-to-batch failure mode on air-free dispense lines. Alumina or boron nitride fillers with median particle size below 2 µm settle when Phase A viscosity drops below 800 mPa·s at storage temperature; therefore S19160 addition is not reduced below 12 phr in filled systems unless a continuous recirculation loop with a 100 µm in-line screen is installed. Die shear strength on copper leadframes is tested before and after 1,000 h of 85°C / 85% RH storage by MIL-STD-883 Method 2019, with a pass threshold typically above 1,800 psi for power-device encapsulants. S19160-containing networks exhibit better retention of die shear than low-crosslink-density analogues, but the advantage is lost if adhesion promoter addition is skipped. A second operational boundary is pot life: the mixed compound must be consumed within 6–8 h at 25°C, and the addition of acetylene alcohol inhibitor at 0.2–0.5 wt% is required when line interruptions exceed 30 min. Avoid introducing amine-bearing epoxy constituents, sulfur-containing rubber residues or organotin stabilizers into shared mixing vessels because these species poison the platinum catalyst and produce uncured surface layers.

What Changes When Vinyl Silicone Resin S19160 Is Carried Below 1 µm Dry Film Thickness in Solventborne Release Coatings?

A solventborne addition-cure release coating containing S19160 is not a single-layer release system; the film-forming outcome depends on the ratio of vinyl silicone resin to linear vinyl polysiloxane, the platinum level, and the hydride-functional crosslinker stoichiometry. S19160 is typically introduced as a co-crosslinker at 20–55 wt% of total silicone solids. During slot-die application on corona-treated PET film at 150–250 m/min, the dry film thickness after solvent removal in a 90–140°C air-floatation oven is maintained between 0.8 µm and 1.5 µm. Corona treatment to 42–48 mN/m by ASTM D2578-23 is required before coating because a lower wetting tension produces crater defects at the thin-film edge and later anchorage failure. The specificity of S19160 lies in its ability to shift peel force from low to medium release without sacrificing smear resistance. In a standard low-release formulation, 180° peel force against a high-tack acrylic tape by FINAT FTM 3 can be held in the 5–25 cN/25 mm range; increasing S19160 fraction to 45–55 wt% moves the response into the 25–60 cN/25 mm band while retaining residual platinum-adhesion test results above 90% ink adhesion when UV-curable inks are printed. The main process conflict is hydride consumption. The resin vinyl groups consume SiH species more rapidly than linear vinyl polysiloxanes, so the hydride crosslinker feed must be recalculated by molar SiH:SiVi ratio rather than by weight. A stoichiometric imbalance that leaves unreacted SiH at the surface increases smear migration into the adhesive and causes erratic peel after 7-day storage at 50°C by FINAT FTM 11.

The second processing risk is platinum inhibition. Trace nitrogen compounds from coexisting polyurethane films, amine-containing antistatic agents or carbon black residues reduce the activity of the Karstedt catalyst. In a solventborne release formulation with S19160, the platinum concentration is commonly raised from 80 ppm to 150 ppm of active platinum relative to silicone solids to compensate for mild inhibition. Pot life at 30°C falls below 4 h when the Pt level is raised; therefore the coating bath is continuously cooled and replenished, and viscosity is monitored by ASTM D4287-19. The addition of 0.1–0.3 wt% acetylene alcohol inhibitor increases pot life but delays cure, so the oven zone temperature must be increased by 10–20°C. S19160 can be reduced below 1 µm dry film thickness only on high-wetting substrates, because at 0.5–0.8 µm the film becomes discontinuous and release force variability exceeds ±15% across the web. Production-scale failure on reverse roll coaters usually appears as chatter lines at high line speed, corrected by increasing the coating bath solids from 15 wt% to 22 wt% or by raising the backing-roll hardness from 65 Shore A to 75 Shore A. A lower solids content tends to produce solvent trapping and blisters in the first oven zone, particularly on low-porosity PET liners.

Compounding of S19160 into liquid silicone rubber for injection-moulded pump diaphragms and medical device seals is conducted before fumed silica incorporation because premature silica wetting can mask the resin’s viscosity contribution. In a 10 L butterfly mixer, the vinyl resin is dispersed at 25–35 wt% into a vinyl-functional base polymer at 70°C under 1–5 mbar vacuum until the mixture is clear. Hydrophobic fumed silica is then added in three splits to avoid shear-induced methyl silicone degradation. The presence of S19160 shifts the balance between Shore A hardness, tensile strength and elongation at break. At a fixed silica loading, increasing the resin content raises Shore A hardness by 3–8 points and raises tear strength measured by ASTM D624-20 Die B, but elongation at break measured by ISO 37:2017 typically falls below 400% above 30 phr resin. This is the primary formulation conflict: the compound becomes stiff enough for automotive valve body seals but loses the low-modulus recovery required for peristaltic pump tubing. In injection-moulded LSR parts, the viscosity increase produced by S19160 changes cold-runner pressure from approximately 60 bar to 140 bar at 23°C, and valve-gate hesitation is observed on 64-cavity micro-moulds when the compound’s zero-shear viscosity exceeds 250 Pa·s. A screw speed reduction of 20–30% is required on an electric injection unit to prevent premature heating and scorch. Cure behaviour is monitored by moving die rheometry according to ISO 6502-2:2018; the t₉₀ at 150°C typically shifts upward by 15–30 s when the S19160 fraction increases from 10 phr to 25 phr. Compounds for medical tubing and seals must meet ISO 10993-5:2009 cytotoxicity and ISO 10993-10:2021 skin sensitisation requirements. S19160-containing formulations are usually evaluated against FDA 21 CFR 177.2600 for repeated-use rubber articles; final compliance depends on the complete formulation, not on the resin alone.

On a two-roll mill for high-consistency silicone rubber, S19160 is added at a 1.1:1 friction ratio with the front roll at 30–40°C. Mooney viscosity measured by ASTM D1646-19 rises from 35 MU to 55 MU when the resin fraction is increased from 10 phr to 30 phr, but the batch remains processable if the nip gap is opened from 0.5 mm to 1.2 mm. The reinforcing mechanism of S19160 in HCR compounds appears only after peroxide or addition cure: compression set after 22 h at 175°C by ASTM D395-18 Method B is lowered by 5–12 percentage points when compared with a silica-only reference of equal hardness. Oven-cured slab stock with 1 wt% dicumyl peroxide at 170°C for 10 min reaches tensile strength above 9 MPa by ISO 37:2017 in many vinyl-MQ-modified HCR systems, but the reported value for this specific product in a given hardness class is formulation-dependent. Temperature resistance is evaluated by dry heat aging at 180°C for 1,680 h according to IEC 60216-4-1:2013; the critical acceptance criterion is retention of tensile strength above 70% of the original value. S19160 should not be combined with acidic fillers above 2 wt% because acid residues inhibit peroxide crosslinking and produce surface tack.

Glass Cloth Sleeving and Class H Winding Impregnation

Vertical tower dip-coating of glass cloth with S19160-modified silicone resin solutions places stringent limits on solvent removal and cure-induced film shrinkage. The resin is dissolved in xylene or toluene at 30–40 wt% solids and applied to 0.20 mm glass braid in 3–5 passes. Each pass is flash-dried at 80–120°C and cured at 180–200°C for 60–90 s in a forced-air vertical tower operating at 1.5–4 m/min. The function of S19160 in this application is to raise the cohesive strength of the cured sleeving without excessive resin pickup. A high resin pickup increases dielectric strength but reduces flexibility and causes cracking during winding of small-radius motor slots. Dielectric breakdown strength is tested by ASTM D149-20 on 0.25 mm sleeving; typical acceptance thresholds for Class H applications are above 7 kV/mm after 96 h at 25°C and 50% RH. Thermal classification is assigned through IEC 60085:2007, with Class H indicating continuous service at 180°C. S19160 improves retention of dielectric strength after thermal aging at 180°C for 1,000 h, but the gain is reduced if the impregnation bath moisture content exceeds 0.1 wt%, because water reacts with residual silanol groups and accelerates film embrittlement. Production-scale failures in this operation typically occur as dielectric pinholes caused by dust contamination in the dip bath; filtration through a 25 µm bag filter is required, and the bath viscosity is maintained at 200–400 mPa·s by DIN EN ISO 3219:1994. The system must also satisfy UL 1446 for electrical insulation systems when the sleeving is used in motor construction; testing is performed on the full insulation system, not on the sleeving alone.

Without solvent stripping control, condensation of S19160 into silanol-terminated PDMS for a silicone pressure-sensitive adhesive will generate a high-viscosity gel that cannot be transferred to polyimide film. S19160 is first condensed at 100–120°C under 1–3 kPa vacuum with an ammonia or lithium hydroxide catalyst, after which the reaction mass is diluted with xylene to 45–55 wt% solids. The vinyl resin raises the crosslink density of the adhesive after peroxides or addition-cure promoters are introduced, shifting tack, peel and high-temperature shear into a usable window for masking tapes and splicing tapes. Peel adhesion from stainless steel is measured by ASTM D3330-04(2020) at 180°; typical silicone PSA systems range from 8 N/25 mm to 30 N/25 mm depending on resin-to-gum ratio. S19160 inclusion at 40–60 wt% of total solids increases the shear adhesion failure temperature above 230°C by PSTC-17. The operational boundary of this route is condensation control: if the reaction is stopped too early, the adhesive will contain residual silanol groups that cause clouding after 30 days at 40°C and 90% RH. If the reaction is allowed to progress too far, the adhesive loses tack and cannot wet stainless steel or polyimide. Coating is performed on a comma coater at 25–75 µm dry thickness and cured at 150–180°C for 2–5 min. Residue after removal from steel panels is tested by ASTM D6862-11; visible residue indicates undercrosslinking or excessive low-molecular-weight siloxane fractions. S19160 formulations intended for aerospace masking tape should be tested against AMS 3637 for silicone tape suitability, and absence of corrosion on titanium is verified by ASTM F1110-20.

When Crosslink Density Is Increased by S19160 Before Gas Evolution in Silicone Foam

Platinum-catalysed silicone foam expansion with S19160 in the polymer matrix requires the crosslink density to be established before the blowing agent decomposes, but not so early that cell walls rupture. In closed-cell silicone foam for EV battery gaskets, the resin is compounded at 15–30 phr into a vinyl polysiloxane base with 1–3 wt% water or a low-temperature blowing agent. The onset of hydrosilylation is set at 80–100°C, while gas evolution occurs at 100–120°C; the 10–20°C separation between the two events determines whether the foam collapses. S19160 narrows this processing window by increasing the cure rate at lower temperature, so platinum inhibitor dose is raised to 0.3–0.5 wt% to delay gelation. Density is measured by ISO 845:2006; compression set after 22 h at 100°C is measured by ASTM D1056-20. S19160 additions shift compression deflection at 25% strain upward, which is required where the foam must retain a sealing force above 10 kPa after automotive thermal cycling. The limiting factor is cell uniformity: at resin loadings above 35 phr the foam develops large voids because the matrix elasticity rises too fast and the expanding gas tears cell walls during the expansion plateau. Production-scale evaluation should include cross-sectional imaging of the foam with a minimum cell count of 25 cells per linear cm for classification as fine-celled. Published data for S19160 in this exact foam configuration is limited; the processing boundary is inferred from the cure-rheology and decomposition behaviour of vinyl MQ resin-containing polysiloxane batches rather than from a product-specific design of experiments. Silicone foams intended for automotive sealing must meet low outgassing requirements by VDA 278:2011 and flammability requirements by FMVSS 302, with the complete gasket assembly tested because the resin alone does not confer a rating.