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Description for Dow 997 Varnish
Long service life; little tendency to bubble; flexible cure schedule.Application Type Bond, Coat 1 Part or 2 Part 1-Part Material Form Liquid Industry Electrical equipment, Transformers, Electrical coil, Motor stator coils, Motors, Solenoids, Transformers windings, Generator coils, Generators Manufacturer Dow Chemistry Xylene, Silicone resin Cure Method Solvent Cure Temperature (°C) >20, 250, 200, 200, 200, 200, 200 Cure Time (min) 360, 180, 360, 30, 240 to 480, 120, 120 Viscosity (cPs) 90 to 120 Color Dark brown Volume Resistivity (O) 2e14 (ohms/cm), 1e14 (ohms/cm) Key Specifications Mil-Spec (United States Military Standard): MIL-I-24092B -
Technical Data for Dow 997 Varnish
Overview
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1 Part or 2 Part
- 1-Part
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Material Form
- Liquid
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Industry
- Electronics - Electrical equipment, Solenoids, Generators
- Transformers - Transformers windings
- Coils - Electrical coil, Generator coils
- Motors - Motor stator coils
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Chemistry
- Other - Xylene
- Silicone - Silicone resin
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Application Method
- Dip
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Cure Method
- Solvent
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Color
- Brown - Dark brown
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Key Specifications
- Mil-Spec (United States Military Standard) : I-24092B - MIL-I-24092B
Specifications
Cure Specs
Cure Temperature (°C) >20, 250, 200, 200, 200, 200, 200 Test Method Cure Time (min) 360, 180, 360, 30, 240 to 480, 120, 120 Test Method Viscosity (cPs) 90 to 120 Test Method Bond Strength
General Bond Strength (psi) Good, 9 (lbs), 16 (lbs), 25 (lbs) Test Method Material Resistance
Moisture/Humidity Resistance Moisture/humidity resistance Conductivity
Dissipation Factor 0.01000, 0.02000, 0.00700, 0.01000 Test Method Dielectric Strength (V/mil) Good, 2,000, 1,500 Test Method Dielectric Constant 3.10, 3.20, 2.98, 3.10 Test Method Thermal Conductivity (W/m°K) 0.15 Test Method Volume Resistivity (O) 2e14 (ohms/cm), 1e14 (ohms/cm) Test Method Hardness
Flexibility Flexible Other Properties
Specific Gravity 1.000 Test Method Flash Point (°F) 80.6 Test Method % Solids (%) 50 Test Method Business Information
Shelf Life Details When stored at or below 25 C (77 F), DOW CORNING 997 varnish has a shelf life of 12 months from date of shipment from Dow Corning. Shelf Life Type From date of shipment Shelf Life (mon) 12 -
Best Practices for Dow 997 Varnish
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Curing
Curing time and temperature vary with the size and complexity of the equipment, the properties desired in the varnish film and the characteristics of the curing oven.
Curing time should be measured from the time both the oven and the impregnated equipment reach the curing temperature. When establishing curing schedules for specific equipment, follow these general rules: Final cure temperature should be at least 20 C (68 F) above the maximum operating temperature of the impregnated equipment.
When maximum bond strength is required, equipment should be given a final cure at 250 C (482 F) for at least 6 hours.
Equipment impregnated with DOW CORNING 997 varnish can usually be placed in ovens at temperatures between 150-200 C (302-392 F) without the appearance of bubbles in the varnish film. Equipment that is to be cured at 250 C (482 F), however, should be given an initial bake of 2 to 4 hours at 150-200 C (302-392 F). Small or complex equipment that will be cured at temperatures above 150 C (302 F) should be given a preliminary bake of 1 hour at 100-150 C (212-302 F).
Immersion time must be kept to a minimum to prevent solvent damage to insulating components.
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Cure Temperature Test Methods
Cure Temperature | Cure Time Test Method |
---|---|
>20°C | |
250°C | |
200°C | |
200°C | |
200°C | 4 to 8 hours at 200 C (392 F). |
200°C | 2 hours at 200 C (392 F), followed by 3 to 7 hours at 225 C (437 F) |
200°C | 2 hours at 200 C (392 F), followed by 2 to 6 hours at 250 C (482 F) |
Cure Time Test Methods
Cure Time | Test Method |
---|---|
360 min | |
180 min | |
360 min | |
30 min | |
240 to 480 min | 4 to 8 hours at 200 C (392 F). |
120 min | 2 hours at 200 C (392 F), followed by 3 to 7 hours at 225 C (437 F) |
120 min | 2 hours at 200 C (392 F), followed by 2 to 6 hours at 250 C (482 F) |
Viscosity Test Methods
Viscosity | Test Method | Temperature |
---|---|---|
90 to 120 cPs | CTM 0050 | 25°C |
General Bond Strength Test Methods
General Bond Strength | Cure Time | Cure Temperature | Test Temperature | Test Method |
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Good | 360 min | 150°C | 25°C | Helical wound coils of No. 18 AWG aluminum wire were impregnated with Dow Corning 997 varnish. The bond strength was determined as the number of pounds required to break this coil as a simple beam. This test is a functional measure of the varnish film strength. |
9 (lbs) | 360 min | 200°C | 25°C | Helical wound coils of No. 18 AWG aluminum wire were impregnated with Dow Corning 997 varnish. The bond strength was determined as the number of pounds required to break this coil as a simple beam. This test is a functional measure of the varnish film strength. |
16 (lbs) | 360 min | 250°C | 25°C | Helical wound coils of No. 18 AWG aluminum wire were impregnated with Dow Corning 997 varnish. The bond strength was determined as the number of pounds required to break this coil as a simple beam. This test is a functional measure of the varnish film strength. |
25 (lbs) |
Dielectric Constant Test Methods
Dielectric Constant | Temperature | Test Method |
---|---|---|
3.10 | 25°C | Dielectric constant, 100 Hz, CTM 0112, 6 hours at 200 C (392 F), as supplied |
3.20 | 25°C | Dielectric constant, 100 Hz, CTM 0112, 6 hours at 200 C (392 F), after 24 hrs immersion in distilled water |
2.98 | 25°C | Dielectric constant, 100 KHz, CTM 0112, 6 hours at 200 C (392 F), as supplied |
3.10 | 25°C | Dielectric constant, 100 KHz, CTM 0112, 6 hours at 200 C (392 F), after 24 hrs immersion in distilled water |
Dielectric Strength Test Methods
Dielectric Strength | Temperature | Test Method |
---|---|---|
Good | ||
2,000 V/mil | 200°C | CTM 0114, 6 hours at 200 C (392 F), as supplied |
1,500 V/mil | 200°C | CTM 0114, 6 hours at 200 C (392 F), after 24 hrs immersion in distilled water |
Dissipation Factor Test Methods
Dissipation Factor | Temperature | Test Method |
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0.01000 | 25°C | Dissipation factor, 100 Hz, CTM 0112, as supplied, 6 hours at 200 C (392 F) |
0.02000 | 25°C | Dissipation factor, 100 Hz, CTM 0112, after 24 hrs immersion in distilled water, 6 hours at 200 C (392 F) |
0.00700 | 25°C | Dissipation factor, 100 KHz, CTM 0112, as supplied, 6 hours at 200 C (392 F) |
0.01000 | 25°C | Dissipation factor, 100 KHz, CTM 0112, after 24 hrs immersion in distilled water, 6 hours at 200 C (392 F) |
Thermal Conductivity Test Methods
Thermal Conductivity | Temperature | Test Method |
---|---|---|
0.15 W/m°K | 200°C | CTM 0224 |
Volume Resistivity Test Methods
Volume Resistivity | Temp (°C) | Test Method |
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2e14 (ohms/cm) | 200°C | CTM 0249, as supplied, 6 hours at 200 C (392 F) |
1e14 (ohms/cm) | 200°C | CTM 0249, after 96 hrs at 23 C (73 F) and 96 percent RH., 6 hours at 200 C (392 F) |
Flash Point Test Methods
Flash Point | Test Method |
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27.0°C | CTM 0021A |
% Solids Test Methods
% Solids | Test Method |
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50 % | CTM 0208, after 3 hrs at 135 C (275 F), percent |
Specific Gravity Test Methods
Specific Gravity | Temperature | Test Method |
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1.000 | 25°C | CTM 0001A |