IEC 60554
Diamond Dotted Paper (DDP)
Electrical insulating paper from 3 mil to 10 mil, coated with heat-curable epoxy resin, for oil-immersed transformer coil insulation.
Diamond Dotted Paper is electrical insulating paper coated with a heat-curable epoxy resin. Under high temperature the resin cures, binding the electrical conductor into a single rigid unit.
DDP is also available on a high density base as DDP-HD.
This bonding behaviour makes DDP well suited to applications where the winding must remain mechanically stable under thermal and electrical stress over the life of the transformer.
Key characteristics
- Heat-curable epoxy resin coating
- Bonds the conductor into a rigid unit at temperature
Applications
- Insulation between coils in oil-immersed transformers
- Cable insulation
Technical data
Specification
Specification limits for Diamond Dotted Paper (DDP), by grade. The same data is in the PDF datasheet.
3 mil to 7 mil
IEC 60554-3 compliant| Property | Unit | 3 mil | 4 mil | 5 mil | 6 mil | 7 mil |
|---|---|---|---|---|---|---|
| pH of aqueous extract | – | 6.0–8.0 | 6.0–8.0 | 6.0–8.0 | 6.0–8.0 | 6.0–8.0 |
| Ash content | % | max 1.0 | max 1.0 | max 1.0 | max 1.0 | max 1.0 |
| Electrical strength | kV/mm | min 7.5 | min 7.5 | min 7.5 | min 7.5 | min 7.5 |
| Conductivity of aqueous extract | mS/m | max 10.0 | max 10.0 | max 10.0 | max 10.0 | max 10.0 |
| Grammage | g/m² | 60 ± 5% | 80 ± 5% | 100 ± 5% | 120 ± 5% | 140 ± 5% |
| Thickness (5 sheets) | µm | 76 ± 7% | 100 ± 7% | 127 ± 4% | 152 ± 4% | 178 ± 4% |
| Coating film thickness | µm | 10–15 | 10–15 | 10–15 | 10–15 | 10–15 |
| Density | g/cm³ | > 0.75 to ≤ 0.85 | > 0.75 to ≤ 0.85 | > 0.75 to ≤ 0.85 | > 0.75 to ≤ 0.85 | > 0.75 to ≤ 0.85 |
| Tensile index MD | N·m/g | min 93 | min 93 | min 93 | min 93 | min 93 |
| Tensile index CD | N·m/g | min 35 | min 35 | min 35 | min 35 | min 35 |
| Elongation MD | % | min 2.0 | min 2.0 | min 2.0 | min 2.0 | min 2.0 |
| Elongation CD | % | min 4.0 | min 4.0 | min 4.0 | min 4.0 | min 4.0 |
| Tear index MD | mN·m²/g | min 5.0 | min 6.0 | min 6.0 | min 6.0 | min 8.0 |
| Tear index CD | mN·m²/g | min 6.0 | min 7.0 | min 7.0 | min 7.0 | min 9.0 |
| Water absorption | mm | min 10 | min 10 | min 10 | min 10 | min 10 |
| Moisture content | % | max 8.0 | max 8.0 | max 8.0 | max 8.0 | max 8.0 |
| Bond test | psi | min 40 | min 40 | min 40 | min 40 | min 40 |
- Values are specification limits for standard supply. Where a specification has been agreed with you in writing, that specification applies.
- Thickness and grammage are nominal values with the tolerance shown. 1 mil = 25.4 µm.
- This datasheet is provided for information. It is not a warranty that the product is suitable for a particular application: confirm suitability for your design and process with us before ordering.
- Specifications may be revised without notice. Copies are uncontrolled once downloaded or printed; the current revision is published at www.tomoegawaindia.com.
- Batch test certificates can be supplied with every despatch on request.
Revision 01, issued 17 October 2026
