Application Case of ThreeBond TB1211 One-Component Oxime RTV Silicone Sealant

This case focuses on two mass-production sealing projects of a domestic new energy auto parts manufacturer: automotive engine timing gear housing sealing & on-board OBC charger aluminum shell sealing, adopting original Japan ThreeBond TB1211 oxime-type solvent-free RTV silicone formed-in-place gasket to replace traditional paper/rubber solid gaskets. The new material solved three core problems: high-temperature oil seepage, leakage caused by mechanical vibration, and electronic control unit failure from water ingress after long-term service. Mass production has been launched since 2021, with annual consumption over 35,000 pieces (310ml/cartridge), marking a classic commercial application of TB1211 in auto component industryスリーボンドグループ.

ThreeBond TB1211 is a single-component, solvent-free, moisture-curing oxime-based RTV silicone sealant, off-white paste at ambient temperature. Key uncured specs (25℃): viscosity 70Pa·s, specific gravity 1.01, tack-free time 40 minutes. Under standard curing condition (23℃,50%RH,168h full cure), cured rubber features Shore A hardness 26, ultimate elongation 300%, tensile strength 2.5MPa, aluminum substrate shear strength 1.4MPa. Continuous service temperature ranges from -60℃ to +200℃ with intermittent peak up to +250℃, outstanding resistance against gasoline, engine lubricating oil and coolant immersion. It bonds excellently to aluminum, cold-rolled steel and mainstream automotive metals, with premium electrical insulation: volume resistivity 5×10¹²Ω·m, dielectric breakdown strength 20MV/m, satisfying both mechanical sealing and electronic insulation requirements as listed on official TDS document.

• Timing gear housing (aluminum flange, max assembly gap:0.2mm):Original nitrile solid gaskets suffered permanent compression set after long service under 100~135℃ engine oil temperature and alternating startup vibration; engine oil leakage appeared after 5,000km mileage with after-sales repair rate at 7.2%, plus gasket swelling after gasoline immersion worsened oil seepage.
• 3.5kW vehicle OBC aluminum enclosure:Original butyl adhesive tape peeled off under vehicle wading and extreme temperature cycling (-40℃~125℃), moisture penetrated into cavity leading to PCB short circuit with 5.8% field failure rate for outdoor vehicles; tape provided no insulation and brought hidden electric leakage risk at grounding positions.
• Diversified solid gaskets brought high inventory cost and low manual assembly efficiency, unable to fill irregular flange gaps.

1. 3.1 Substrate Pre-treatment

   Remove grease, release agent and dust from aluminum/steel flange surface via sanding and isopropanol wiping, fully air dry before gluing. Keep sealant stored at 10~25℃ and warm up to room temperature before opening package to avoid inner container condensation.

2. 3.2 Dispensing & Assembly

   Pneumatic caulking gun for continuous uniform bead application (2~3mm width):

   • Timing gear housing (0.1~0.2mm gap): TB1211 filling sealing, rated burst pressure 0.04MPa under 0.2mm clearance matching engine inner oil pressure per TDS pressure resistance data;
   • OBC enclosure (≤0.1mm gap): thin continuous bead with 0.07MPa withstand pressure for water blocking.

   Fasten all screws and close assembly within 40min tack-free window as specified on TDS. Partial surface cure takes 24h under ambient humidity, complete full cure requires 168h/7days under 23℃,50%RH before finished product delivery.

3. 3.3 Excess Sealant Removal

   Wipe uncured squeeze-out with clean cloth; remove fully cured surplus glue by ThreeBond original TB2890E cleaner. Seal leftover original container tightly and store in cool dark warehouse (10~25℃), never pour leftover glue back into original drum after repackaging.

• Engine timing housing: zero oil leakage after 100,000km road test; volume change +5% after 100℃/24h engine oil immersion, -20.2% after 50℃ gasoline soaking (official TDS lab data). 300% high elongation offsets flange thermal expansion & contraction under -60℃~200℃ temperature fluctuation, outstanding shock/vibration resistance vs traditional rubber gaskets, after-sales leakage repair rate down from7.2% to below0.3%.
• Vehicle OBC charger: 20MV/m dielectric strength eliminates electric leakage risk; only -0.5% volume shrinkage after90℃ hot water soaking, field short-circuit failure rate reduced from5.8% to below0.5% after rain & high-low temperature cycling road test.

Eliminate dozens of solid gasket SKUs to cut mold & warehousing cost; automatic dispensing replaces manual gasket placement, assembly time reduced by22%, overall sealing cost cut by15%.

Based on verified field performance, the manufacturer expands TB1211 to three new mass-production lines: generator end cover flange, construction machinery hydraulic valve thread, small water pump shell formed-in-place gasket. Important note: TB1211 oxime curing system causes corrosion to copper & copper-alloy, forbidden for copper component sealing; select alcohol-type ThreeBond sealant for copper applications.

• Automotive: Engine oil pan, valve cover, transmission flange, starter/generator housing, automotive sensor enclosure sealing (official recommended core application by ThreeBond Global)スリーボンドグループ;
• General Machinery & Electrical: Small-medium motor end cap, hydraulic pump/valve, air compressor flange, industrial equipment cabinet sealing;
• New Energy Electronics: On-board DC-DC converter, small energy storage inverter aluminum shell waterproof & insulation sealing;
• Construction Machinery & Marine: Mini marine pump flange, agricultural machinery engine housing, air compressor pipeline thread sealing;
• Reminder: TB1211 is solvent-free & low-odor, NOT compatible with bare copper/bronze substrate sealing.