Durostone® EPC 203
Durostone EPC 203 is an epoxy (EP) resin composite reinforced with E-glass fine fabric, delivering 16 kV/mm electric strength under oil and a Temperature Index of 155 with Insulation Class F. The material provides 450 MPa flexural strength perpendicular to lamination, 350 MPa tensile strength parallel to lamination, and water absorption below 0.1%. Engineered for transformers, motors, generators, and electrical insulation components.
Key Properties
- Density: 1.85 g/cm³ (ISO 1183)
- Tensile Strength ∥: 350 MPa (ISO 527)
- Flexural Strength ⊥: 450 MPa (ISO 178)
- Electric Strength 90°C Under Oil ⊥: 16 kV/mm (IEC 60243)
- Temperature Index: 155 (IEC 60216) — Insulation Class F (IEC 60085)
- Water Absorption (4 mm): < 0.1% (ISO 62)
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- Specifications
- Applications
- General Info
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Mechanical Properties
| Property | Value | Test Method |
| Density | 1.85 g/cm³ | ISO 1183 |
| Flexural Strength ⊥ | 450 MPa | ISO 178 |
| Flexural Strength ⊥ +150°C | 230 MPa | ISO 178 |
| Modulus of Elasticity in Flexion ⊥ | 23,000 MPa | ISO 178 |
| Modulus of Elasticity in Flexion ⊥ +150°C | 18,000 MPa | ISO 178 |
| Compressive Strength ⊥ | 500 MPa | ISO 604 |
| Tensile Strength ∥ | 350 MPa | ISO 527 |
| Impact Strength ∥ (Charpy) | 100 kJ/m² | ISO 179 |
Thermal Properties
| Property | Value | Test Method |
| Temperature Index | 155 (T.I.) | IEC 60216 |
| Insulation Class | F | IEC 60085 |
Physical Properties
| Property | Value | Test Method |
| Water Absorption (4 mm thickness) | < 0.1% | ISO 62 |
Electrical Properties
| Property | Value | Test Method |
| Electric Strength 90°C Under Oil ⊥ | 16 kV/mm | IEC 60243 |
| Electric Strength 90°C Under Oil ∥ | 70 kV/25 mm | IEC 60243 |
| Insulation Resistance | 10¹⁴ Ω | IEC 60167 |
| Specific Surface Resistance | 5 × 10¹⁰ Ω | IEC 60093 |
| Comparative Tracking Index | 180 (CTI) | IEC 60112 |
| Insulation Resistance After 24 h Water Immersion | 10¹² Ω | IEC 60167 |
⊥ = perpendicular to the lamination | ∥ = parallel to the lamination
Compliance
- ISO 1183, ISO 178, ISO 604, ISO 527, ISO 179, ISO 62 — Compliant (test standards)
- IEC 60216 — Compliant (Temperature Index 155)
- IEC 60085 — Compliant (Insulation Class F)
- IEC 60243, IEC 60167, IEC 60093, IEC 60112 — Compliant (test standards)
- Oil-filled transformer insulation components
- Dry transformer insulation components
- Generator and motor insulation parts
- Electrical insulating components for the electrical industry
- Structural insulation laminates for electrical assemblies
Common industries: electrical, generator and motor manufacturing, and transformer manufacturing.
Durostone EPC 203 is an epoxy resin composite reinforced with E-glass fine fabric, sitting within the Durostone family of fiber-reinforced electrical insulation laminates. It is engineered for service in transformers (oil-filled and dry), motors, generators, and general electrical insulating components, where good mechanical performance must be paired with reliable dielectric behavior.
Mechanical performance includes 1.85 g/cm³ density, 450 MPa flexural strength perpendicular to the lamination (230 MPa retained at +150°C), 23,000 MPa modulus of elasticity in flexion (18,000 MPa at +150°C), 500 MPa compressive strength perpendicular to lamination, 350 MPa tensile strength parallel to lamination, and 100 kJ/m² Charpy impact strength parallel to lamination.
Thermally, the material carries a Temperature Index of 155 and is rated Insulation Class F per IEC 60085. Dielectrically, EPC 203 provides 16 kV/mm electric strength perpendicular and 70 kV/25 mm parallel under oil at 90°C, 10¹⁴ Ω insulation resistance (10¹² Ω after 24 h water immersion), 5 × 10¹⁰ Ω specific surface resistance, and a Comparative Tracking Index of 180. Water absorption at 4 mm thickness is below 0.1%.
Compliant with the listed test standards: ISO 1183, ISO 178, ISO 604, ISO 527, ISO 179, ISO 62, IEC 60216, IEC 60085, IEC 60243, IEC 60167, IEC 60093, and IEC 60112.
What differentiates Durostone EPC 203 from other glass-reinforced electrical laminates?
EPC 203 uses an epoxy (EP) resin matrix reinforced with E-glass fine fabric, delivering a balance of good mechanical and electrical properties at Insulation Class F. Compared to coarser reinforcement constructions, the fine fabric supports higher flexural strength (450 MPa ⊥) and higher dielectric performance (16 kV/mm ⊥ under oil at 90°C) while maintaining water absorption below 0.1% — characteristics that suit transformer, motor, and generator insulation work.
Why does dielectric strength matter for this material?
The defining function of an electrical insulation laminate is to withstand applied voltage without breakdown. EPC 203 is qualified at 16 kV/mm perpendicular and 70 kV/25 mm parallel under oil at 90°C per IEC 60243, with insulation resistance of 10¹⁴ Ω that remains 10¹² Ω after 24 h water immersion. Those numbers are what make the material specifiable for oil-filled transformers and similar high-voltage service.
What is the operating temperature classification for EPC 203?
The material has a Temperature Index of 155 per IEC 60216 and is rated Insulation Class F per IEC 60085. Flexural strength of 230 MPa and modulus of 18,000 MPa are retained at +150°C.
Is EPC 203 suitable for electrical and transformer-rated environments?
Yes. The material is qualified to IEC 60216 (Temperature Index 155) and IEC 60085 (Insulation Class F), with documented IEC 60243, IEC 60167, IEC 60093, and IEC 60112 dielectric performance, making it suitable for electrical insulation in oil-filled transformers, dry transformers, generators, and motors.
How should EPC 203 be specified?
Specify grade (Durostone EPC 203), thickness, sheet dimensions, dielectric performance requirements (electric strength, insulation resistance, CTI), thermal class (Insulation Class F / Temperature Index 155), dimensional tolerances, and finished format.
