3M 251
Harmonization Code : 3907.30.00.40 | Epoxy Mold Compounds containing by weight more than 70 % silicon dioxide
Main features
- Balanced One-to-One Mixing
- Defined Oven-Cure Handling
- Rigid Class F Insulation
Product Description
3M Scotchcast Electrical Resin 251 is a two-part, oven-curing, filled epoxy liquid resin for insulating, potting, filling, and patching electrical and electronic components. Parts A and B mix 1:1 by weight or 50:50 by volume; the mixed resin has typical viscosity of 19,000 cP at 23 deg C and gels in 20 minutes at 121 deg C. The cured rigid Class F system combines 40 Barcol hardness with typical electric strength of 425 V/mil (16.8 kV/mm) on a 1/8 in (3.75 mm) sample. It is used on coils, transformers, motors, modules, and related electrical assemblies requiring physical strength and elevated-temperature electrical performance.
Key features
- Balanced two-part mixing: Parts A and B mix 1:1 by weight or 50:50 by volume.
- Defined oven-cure handling: Typical mixed viscosity is 19,000 cP at 23 deg C with 20-minute gel time at 121 deg C.
- Rigid Class F insulation: The cured filled epoxy provides typical 40 Barcol hardness and 425 V/mil electric strength under the stated conditions.
Applications
Applications include coating, filling, patching, insulating, and potting coils, transformers, motors, modules, and electrical or electronic components.
TDS, SDS & Technical Documents
Technical Specifications
General Properties
Mechanical Properties
Other Properties
Additional Information
As-supplied / before-processing properties
Component and mixed-material values remain separated, and mix ratios retain their stated basis.
| Property | Value | Unit | Method / condition |
|---|---|---|---|
| Mix ratio by weight (A:B) | 1:1 | - | Before processing |
| Mix ratio by volume (A:B) | 50:50 | % | Before processing |
| Part A viscosity | 175,000 | cP | Typical at 23 deg C |
| Part B viscosity | 10,000 | cP | Typical at 23 deg C |
| Mixed viscosity | 19,000 | cP | Typical at 23 deg C |
| Density (A / B) | 1.53 / 1.48 | kg/L | Typical |
| Gel time | 20 | min | Typical at 121 deg C |
| Cure guide | 15 to 20 h / 6 to 8 h / 2 to 3 h | - | 75 deg C / 95 deg C / 120 deg C |
Final-state / after-processing properties
Cured properties are typical, not specification limits, and are measured at 23 deg C unless stated otherwise.
| Property | Value | Unit | Method / condition |
|---|---|---|---|
| Cured color | Brown | - | Typical |
| Hardness | 40 | Barcol | Typical at 23 deg C |
| Specific gravity | 1.50 | - | Typical; cured |
| Compressive strength | 17,500 | psi | Typical; 10% compression |
| Tensile strength | 5,280 | psi | Typical |
| Elongation at break | 0.7 | % | Typical |
| Electric strength | 425 (16.8) | V/mil (kV/mm) | Typical; 1/8 in (3.75 mm) sample |
| Heat distortion point | 130 (266) | deg C (deg F) | Typical; 264 psi |
