GMNA - 9986495
Adhesive/Sealant, Silicone, Room Temperature Vulcanizing, Oxime Cure for Engine Sealing
|Publication Date:||1 July 2018|
Note: The words must, shall or will as used in this document mean a mandatory requirement.
Material Description. This silicone adhesive/sealant requires no catalyst or heat to cure. When applied wet (uncured) it reacts with moisture in the air (condensation cure) releasing an alcohol (methanol) by-product and fully cures to an elastomeric product adhering to most clean surfaces without need of a primer. Adhesively bonded and fully cured adhesive/sealant acts as a barrier against oil migration across mating surfaces. The curing reaction releases methyl ethyl ketoxime (two (2)-butanone) and is not acceptable for use in Europe.
Symbols. Not applicable.
Applicability. Formed-in-Place Gasket (FIPG) for sealing engine covers, pans or mating of other components for oil seal integrity or to restrict dust or unwanted air and water intrusion.
Application Temperature and Assembly Sequence. Unless otherwise specified by the adhesive/sealant manufacturer, apply this adhesive/sealant on the intended surface whose temperature is from 18 °C to 40 °C (65 °F to 104 °F). Below 20 °C, adhesion and cure rate slows. It is the responsibility of the applicator and the adhesive/sealant manufacturer to establish the accepted conditions, e.g., process time from applied bead to assembly to air test, temperature and adhesive/sealant cure rate to provide acceptable adhesion and leak test performance. See the Assembly, Sealing and Fastening Bill of Materials (BOM) Level II for minimum process time.
Other Surface Treatments. The adhesive/sealant approved to this standard must be applied after paint or coated part treatments (e.g., electrodeposition (ELPO)/Uniprime coatings of stamped steel covers). It is the responsibility of the applicator and the adhesive/sealant manufacturer to establish the accepted conditions, e.g., time, temperature and coating cure to provide acceptable adhesion and leak test performance. Use standard test panels if available.
Cleanliness of Mating Joint Surfaces. It is the responsibility of the applicator and the adhesive/sealant manufacturer to establish the accepted surface conditions, e.g., washer cleaner concentrations, drying time, and storage protection from airborne contaminants to provide acceptable adhesion and leak test performance.
Gap Limitations. Adhesive/sealant capable of sealing a gap from 0.1 mm to 1.0 mm (the blowout test determines the maximum gap).
Unlike silicone sealant chemistry, silicone sealant poses no contamination risk to oxygen sensors or increased oil foaming due to oil absorption and extraction during curing.
Cost. Unless otherwise specified, pricing shall be based on 20 kg (5 gal) pails compared with existing products. Material cost comparison is sealant price per mass (grams) times specific gravity. The quantity of sealant per pail varies with manufacturer. Cost comparison for decision making must be from engine specific use (grams per component, engine) and annual volumes.
Sealant unit cost increases with decreasing container size. When conducting cost studies, remember that sealant cost will vary with the global region.
Methyl ethyl ketoxime (MEKO) sealants are a 0.40 United States Dollar (USD) less per engine cost versus non-MEKO containing sealants. Unless your application region regulations (not product engineering) requires MEKO free sealant, a MEKO product is more cost effective.
Cure Rate. This adhesive/sealant has a lower viscosity, faster cure and higher elongation than 9986493 MEKO-free alcohol adhesive/sealant from 10% to 100% relative humidity (RH). Depth of cure inward from an exposed 1 mm edge for 7 days at 20 °C, 50% RH is 2.3 mm (see 188.8.131.52 and 7.1 Glossary; Cure Speed).