GMNA - 9985990
Adhesive, Room Temperature Vulcanizing (RTV), Silicone, One-Part
|Publication Date:||1 May 2017|
Note: The words must, shall or will as used in this document mean a mandatory requirement.
Material Description. This specification covers a one-part, room temperature vulcanizing (RTV), oxime cure silicone rubber, formed-in-place gasket (FIPG).
The system must be capable of being, dispensed with current production equipment. It shall be compatible with production systems.
Limitations (ASTM D1329, SAE J1497). Functional temperature environment is -55 °C to 150 °C. Material requires no catalyst or heat to cure. When applied, it reacts with moisture in the air and fully cures to an elastomeric product, adhering to most clean surfaces without need of a primer. Further information can be found in SAE J1497. Not recommended for water/glycol applications.
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. This sealant contains methyl ethyl ketoxime (MEKO) (2-butanone) and is restricted from GM Europe use. 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. 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 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 220.127.116.11 and Table 3). Upper 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, do not 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 18.104.22.168 and Table 1).
Sealant unit cost increases with decreasing container size. When conducting cost studies remember that sealant cost will vary with the global region.
This specification is, maintained at the request of China engine operations. As a legacy sealant, it does not contain any fuel dilution in oil requirements or foam stability in GMW17332 engine oils.
Cure Rate. The higher the humidity is, 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 acetoxy adhesive/sealants but faster than alkoxy cure systems from 10% to 100% relative humidity (RH).
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 100% of the fasteners tightened to the final torque with no, two (2) adjacent fasteners untightened
In 2016 the total oxime crosslink production for all Henkel Loctite oxime cure RTV sealant switched exclusively to China. The table test data in this standard is from the China oxime crosslink source. This manufacturing site change did not affect fit, form or function (GMW17205) so no part number change is required
Two viscosity Types (Type I High, Type II Low) were, permitted in the previous version of this standard. Only the Type I High production properties were, retained in this 9985990. The Type II Low, lower service viscosity (if needed) will require a new 998 number.
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) 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 (on-set of sealant tear), tensile and shear strength is lower than amine 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 glossary, 7.1) 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 adhesion conditions; (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 seven (7) day cure period). Note: seven days is the industry standard for all cured test conditions) shall be considered, for testing the adhesion robustness of a sealant.
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 liquid (see 9986499) to maximize bond performance. These are not cleaners, as they 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 except where Methyl Ethyl Ketoxime (MEKO) is not permitted.