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GMNA - 9986350

Adhesive/Sealant, Room Temperature Vulcanizing, Alkoxy Cure for Engine Sealing

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Organization: GMNA
Publication Date: 1 May 2019
Status: active
Page Count: 16
scope:

Note: The words must, shall or will as used in this document mean a mandatory requirement.

Material Description. This standard describes the material and performance requirements of a one component, room temperature vulcanizing (RTV), silicone rubber formed-in-place gasket (FIPG) for use in GM assembly plant operations and service.

This adhesive/sealant requires no catalyst or heat to cure. When applied, it reacts with moisture in the air 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 no methyl ethyl ketoxime (MEKO).

Symbols. Not applicable.

Applicability. 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. This sealant complies with MEKO-free requirements. It is intended for oil use only.

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 20 °C to 40 °C. At temperatures < 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 Assembly, Sealing and Fastening Bill of Materials (BOM) Level II for minimum process time.

Continuous Upper Temperature. Up to 165 °C as defined by SAE J2236 (see 3.2.2.1 and Table 3). Use temperature is a material strength measurement, not related to adhesion performance.

Other Surface Treatments. The adhesive/sealant approved to this standard must be applied after paint or coated part treatments (e.g., cathodic electrodeposition paint operation (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.

Monitoring Cleaning/Washing System Changes on Adhesion. It is the responsibility of the sealant applicator to evaluate changes in chemical cleaning/washing systems over time for parts where sealant is applied. Changes must be supported by lap shear data to evaluate the effect on sealant adhesion. Run the appropriate Table 2 test panels through the relevant washer system changes in production scale or in a pilot size operation. The values must meet or exceed Table 3 values. Any joints receiving plasma treatment as a surface preparation method in production don't require data monitoring of a change in cleaner/washer.

Gap Limitations. Adhesive/sealant is capable of sealing a gap from 0.1 mm to 1.5 mm. This is a design control limit determined from the pressure blowout resistance (see Table 1).

Remarks.

Cost. For North America this MEKO-free sealant is more expensive ($0.45 USD to $0.62 USD cents per engine) than MEKO containing adhesive/sealants (e.g., 9986495) based on regional pricing of drums in 2017 for the Cylinder Set Strategy (CSS) engine program. See 1.4.1.2.

Cost Applicability. Cost content information is intended to prevent widespread use of MEKO-free sealants for regions where no regulations require it. Contact the Global Purchasing and Supply Chain fluids buyer for current regional cost. Compliance to MEKO-free regulations is a cost driver with little significance to long term exposure risk as supported by airborne measurement and sealant dispensing in well ventilated areas.

Sealant unit cost increases with decreasing container size. When conducting cost studies, remember that sealant cost for the same container size will vary with the global region because the supplier has no global unitized pricing for this sealant and currency value fluctuations at the time of purchase.

International MEKO limits. At the time of publication, Brazil, Canada, China, Korea and the USA have no MEKO requirements. Only Europe at 1% maximum and Mexico at 2% have airborne limits.

Process Behavior.

Cure Rate. The higher the humidity, the faster the cure. Faster cure is desired for narrow flanged joints where air leak pressure is applied soon after the final sealant joint is completed. This adhesive/sealant is slower than ketoxime or acetoxy adhesive/sealants from 10% to 100% relative humidity (RH). Depth of cure inward from an exposed edge for 7 d at 20 °C is 5.7 mm versus 7.1 mm for 9982257.

Open Time to Joint Assembly. All RTV sealant joints must be closed and clamped within 8 minutes of the sealant application to the mating flange. Clamped is defined as having a minimum of 80% of the fasteners tightened to the final torque with no two adjacent fasteners untightened (see 7.1, Lateral Joint Movement).

Joint Performance. Measured by lap shear strength (ISO 4587), this sealant has sufficient elongation to maintain adhesion in joints with moderately different rates of thermal expansion. At 1.5 mm it has excellent gap sealing capability. This adhesive/sealant has comparable lateral joint movement (onset of cohesive or adhesive failure) to other alkoxy cure sealants (e.g., 9986493) and good shear strength to metals, however, adhesion to plastics is weak with 100% adhesive separation to nylon. Once the lateral joint movement limit is exceeded (onset of sealant tear), tensile and shear strength is lower than ketoxime and acetoxy cure systems on all metal substrates.

Proper Use of Test Methods. Testing for this standard is based on coupon surfaces and conditions different from those of assembly or service. Standard tests permit comparison between products while attempting to represent a worse case condition related to end use. Testing actual production processes and surfaces is necessary before actions are taken. Use the test matched with the desired property/definition.

For example: Lap Shear strength may be used to measure the effect of sealant and/or process variation (e.g., ineffective surface cleanliness, build variations, etc.) on bond strength provided it mimics the actual production application with all its known variables. Lap shear is a cured property, not a wet uncured characteristic. It shall not be used to set individual process conditions such as open time because tack free time as tested and defined (see 7.1; Cure Speed, Certificate of Analysis, Lateral Joint Movement, Tack Free Time, etc.) is the proper test and can be measured immediately on site under changing conditions.

Worst Case Test Conditions. Since bondline adhesion is the most essential sealant property, the following conditions shall be considered for testing the robustness of a sealant.

Adhesion: Worst finish (e.g., smooth or as cast surface finish); worst contaminated surface (e.g., oily or washer residue), maximum recommended gap, slowest cure speed (e.g., lowest temperature and humidity for 7 d cure period). Seven (7) days is the industry standard for all cured test conditions.

Surface Treatments to Promote Joint Adhesion. Demanding and enforcing part cleaning control through cleaning process specifications is necessary for optimum sealant to joint bond life. Surface treatment chemicals (e.g., Henkel BONDERITE) formulated for specific base metals are applied in washer systems or by liquidsoaked applicator to maximize bond performance. These are not cleaners, as maximizers are only effective on a washed surface, but properly applied and protected may be globally shipped and perform long after the application.

Regulatory Restrictions. This sealant is approved for use in every global region.

Fuel Dilution in Engine Oil. This sealant lap shear testing to GMW16678, Condition A, Solution E fuel dilution (see Table 3, Note 1) produced adhesive not cohesive separation from the test panel substrates. Testing of production surfaces for adhesion evaluation is mandatory for engine joints where the fluid level is above the joint whether the engine is on or off. The results on engine joints exposed to measured fuel dilution conditions will dictate use.

Foam Stability. The curing sealant has a tendency to foam in GM Dexos® 0W20 oil. The 0W20 oil by itself foams in ASTM D892, Sequence II and III tests. The values after 5 minutes and 10 minutes in Table 1 represent the sealant contribution portion of the foaming limits. The sealant contribution to foaming will not dissipate until the sealant is fully cured and the oil changed.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Document History

9986350
May 1, 2019
Adhesive/Sealant, Room Temperature Vulcanizing, Alkoxy Cure for Engine Sealing
Note: The words must, shall or will as used in this document mean a mandatory requirement. Material Description. This standard describes the material and performance requirements of a one component,...
February 1, 2016
Adhesive/Sealant, Room Temperature Vulcanizing, Alkoxy Cure for Engine Sealing
Note: The words must, shall or will as used in this document mean a mandatory requirement. Material Description. This standard describes the material and performance requirements of a one component,...
July 1, 2010
Adhesive/Sealant, Room Temperature Vulcanizing, Alkoxy Cure for Engine Sealing
This standard describes the material and performance requirements of a one component, room temperature vulcanizing (RTV), silicone rubber formed-in-place gasket (FIPG) for use in GM assembly plant...

References

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