IS 8570 / IEC 60554
Electrical Grade Insulation Kraft Paper
Insulation kraft paper in a thickness range of 1.5 mil to 10 mil, made to your specified thickness from 100% imported virgin fibre under de-mineralised process conditions.
We offer Electrical Grade Insulation Kraft Paper across a thickness range of 1.5 mil to 10 mil, made to the thickness your specification calls for rather than a fixed list of grades. For higher density, see High Density Kraft Paper, available from 3 mil. All production is dual-ply as standard.
All grades are processed in controlled conditions, maintaining conformity at every stage. Production follows a daily and monthly plan, and the processes involved include Pulping & Refining, Paper Machine process (Wire, Press part and Dryers), Calendering & Supercalendering, and Re-winding.
Every process is identified and mapped. The process mappings document the activities involved and the records generated, and the documented process specifications ensure smooth implementation and consistent record-keeping.
Key characteristics
- 100% imported virgin fibre from Europe and North America
- De-mineralised process water throughout
- Dual-ply (twin layer) construction as standard
- Offline calendering and supercalendering
- Guaranteed not to tear in edgefolding
Applications
- Transformer interleaving
- Conductor covering
- Conductor winding and covering
- Bushings
- Distribution transformers
- Power transformers
Technical data
Specification
Specification limits for Electrical Grade Insulation Kraft Paper, by grade. The same data is in the PDF datasheet.
1.5 mil to 2.5 mil
| Property | Unit | 1.5 mil | 2.0 mil | 2.5 mil |
|---|---|---|---|---|
| pH of aqueous extract | – | 6.0–8.5 | 6.0–8.5 | 6.0–8.5 |
| Ash content | % | max 1.0 | max 1.0 | max 1.0 |
| Electrical strength (in air) | kV/mm | min 7.0 | min 7.0 | min 7.0 |
| Conductivity of aqueous extract | mS/m | max 4.0 | max 4.0 | max 4.0 |
| Grammage | g/m² | 32 ± 3% | 40 ± 4% | 50.8 ± 5% |
| Thickness (5 sheets) | µm | 40 ± 4% | 50 ± 5% | 63.5 ± 6% |
| Density | g/cm³ | > 0.60 to ≤ 0.85 | > 0.60 to ≤ 0.85 | > 0.60 to ≤ 0.85 |
| Tensile index MD | N·m/g | min 59 | min 59 | min 59 |
| Tensile index CD | N·m/g | min 11 | min 13 | min 13 |
| Elongation MD | % | min 1.5 | min 1.5 | min 1.5 |
| Elongation CD | % | min 1.8 | min 2.7 | min 2.7 |
| Tear index MD | mN·m²/g | min 2.5 | min 3.0 | min 3.0 |
| Tear index CD | mN·m²/g | min 7.0 | min 7.0 | min 7.0 |
| Air permeability | µm/(Pa·s) | max 1.0 | max 1.0 | max 1.0 |
| Water absorption | mm | min 2.0 | min 3.0 | min 4.0 |
| Moisture content | % | max 8.0 | max 8.0 | max 8.0 |
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% |
| 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 |
- 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
