EPN Tough
Grade
Tough = rubber-toughened (CTBN / core-shell modified) novolac epoxy
Choose when crack resistance, thermal-shock survival or structural adhesive peel strength matters more than peak Tg and modulus.
Values for the Tough condition
Other EPN grades and fills
EPN is listed in 8 conditions; see the grade overview at EPN.
Compare all 8 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
ToughThis page Rubber-toughened (CTBN / core-shell modified) novolac epoxy | Choose when crack resistance, thermal-shock survival or structural adhesive peel strength matters more than peak Tg and modulus. | — | 60 | 5 | 95 HRM |
Flame-retardant grade (brominated novolac / phosphorus-modified), UL 94… | Choose where UL 94 V-0 and high LOI are required in electrical encapsulation, laminates or transformer castings. | — | 68 | 1.7 | 89 Shore D |
O-Cresol novolac epoxy | Pick the cresol-novolac chemistry for solid-state moulding powders and EMC binders — higher softening point, lower melt tack and slightly higher Tg than phenol-novolac EPN. | — | 70 | 1.6 | 89 Shore D |
NEATDefault Unfilled / neat cast resin | Baseline cured novolac epoxy casting or coating film — choose for chemical linings, adhesives and general high-Tg castings where stiffness demand is modest. | — | 72 | 2 | 108 HRM |
Fused-silica filled epoxy molding compound | Pick for IC/discrete encapsulation and transfer-molded electronics where low CTE, low ionic content and low moisture uptake are mandatory. | — | 85 | 0.7 | 90 Shore D |
Glass-fabric reinforced novolac epoxy laminate | Choose for high-Tg PCB substrates, electrical insulation parts and structural panels needing 180 °C service with good dielectric behaviour. | — | 330 | 1.8 | — |
Carbon-fibre prepreg laminate, novolac-epoxy matrix | Choose for aerospace/motorsport structures needing 160–190 °C hot-wet capability beyond standard 120 °C-cure DGEBA prepregs. | — | 1,900 | 1.5 | — |
Thermally conductive mineral filled | Choose for potting power electronics and LED modules where heat removal plus electrical isolation is required. | — | — | — | — |
What is EPN Tough?
EPN Tough is EPN in the Tough grade — choose when crack resistance, thermal-shock survival or structural adhesive peel strength matters more than peak Tg and modulus. EPN Tough has a tensile strength of 60 MPa (8.7 ksi), stronger than 68% of polymer grades. Elongation at break is 5% and the elastic modulus is 2.7 GPa (0.392 Msi). EPN Tough has a density of 1.18 g/cm³ (0.0426 lb/in³), heavier than 50% of polymer grades. Its glass-transition temperature is 160°C (320 °F). NEAT is the default condition FabDigit quotes; Tough is available on request or by drawing note.
Advantages
- High service temperature — 155°C (311 °F), better than 81% of polymer grades
- Polishes to a fine finish — 70/100, better than 77% of polymer grades
Limitations
- Degrades in UV without stabilisers — 22/100, worse than 83% of polymer grades
- High embodied carbon — 6.8 kg CO₂/kg, worse than 75% of polymer grades
EPN Tough properties
Typical room-temperature values for EPN Tough; 12 are specific to this condition. Other listed values are EPN reference data and may not represent this condition. Bars are the position among polymer grades.
Physical5
EPN Tough has a density of 1.18 g/cm³ (0.0426 lb/in³), heavier than 50% of polymer grades. Its glass-transition temperature is 160°C (320 °F).
Mechanical15
EPN Tough has a tensile strength of 60 MPa (8.7 ksi), stronger than 68% of polymer grades. Elongation at break is 5% and the elastic modulus is 2.7 GPa (0.392 Msi).
Thermal10
EPN Tough is rated for continuous service to 155°C (311 °F). It conducts heat at 0.2 W/m·K (0.116 BTU/hr·ft·°F), worse than 56% of polymer grades. Thermal expansion is 60 µm/m·K (33.3 µin/in·°F).
Electrical7
EPN Tough is an electrical insulator with a dielectric strength of 19 kV/mm (482.6 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 74% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of EPN Tough takes about 135 MJ of energy and emits 6.8 kg of CO₂ — more than 79% of polymer grades. Typical recycled content is 0%.
Manufacturability5
EPN Tough's machinability is good (55/100, worse than 64% of polymer grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with EPN Tough
Is EPN easy to machine?
Machines like a hard brittle thermoset — sharp carbide or PCD tools, high speed, low feed, no coolant needed but strong dust extraction; chipping at exits and drill breakout must be controlled with backing.
Can EPN be welded?
Not weldable — thermoset; join by structural epoxy bonding, mechanical fasteners or co-cure of uncured plies.
Can EPN be formed, bent or molded?
Processed hot (resin softens 60–100 °C): casting, RTM/infusion, prepreg autoclave cure (180 °C typical) or transfer moulding at 165–185 °C with 60–180 s gel; a 180–200 °C post-cure is needed to reach full Tg, and high exotherm plus ~1–2 % cure shrinkage require thin sections or filler loading.
What surface finishes work on EPN?
Surfaces sand and polish well and take epoxy or PU paint after light abrasion; pigmented or UV-blocking topcoat is recommended outdoors because the aromatic backbone chalks and yellows.
EPN chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| epoxy phenol-novolac resin (phenol–formaEEW ≈ 170–185 g/eq, functionality 2.2–6; ECN variant EEW ≈ 195–220 | 55 – 100 | 65 |
| curing agent (phenolic novolac / anhydristoichiometric to epoxy equivalents; determines Tg | 0 – 45 | 34 |
| accelerator (imidazole, TPP, tertiary am | 0.1 – 2 | 0.5 |
| hydrolysable chlorine≤300 ppm for semiconductor-grade resin | ≤ 0.05 | 0.02 |
| fused silica / mineral filler0 for the neat default variant; 70–88 wt% in EMC | 0 – 88 | 0 |
| glass or carbon fibrereinforced variants only | 0 – 65 | 0 |
EPN Tough — frequently asked
What is EPN Tough used for?
EPN Tough is typically used for semiconductor encapsulation, high-temperature composite matrices, corrosion-resistant coatings and printed circuit board resin. In short: higher Tg than bisphenol-A epoxy; standard chip encapsulation resin; brittle at 2 % elongation.
What is the tensile strength of EPN Tough?
EPN Tough has a typical tensile strength of 60 MPa (8.7 ksi) — stronger than 68% of polymer grades. Strength varies by condition: see the 8 listed tempers.
Is EPN Tough easy to machine?
Reasonably — machinability is rated good (55/100, worse than 64% of polymer grades). Machines like a hard brittle thermoset — sharp carbide or PCD tools, high speed, low feed, no coolant needed but strong dust extraction; chipping at exits and drill breakout must be controlled with backing.
Can EPN Tough be welded?
Not weldable — thermoset; join by structural epoxy bonding, mechanical fasteners or co-cure of uncured plies.
What surface finishes work on EPN Tough?
Surfaces sand and polish well and take epoxy or PU paint after light abrasion; pigmented or UV-blocking topcoat is recommended outdoors because the aromatic backbone chalks and yellows.
Can EPN Tough be formed, bent or molded?
Processed hot (resin softens 60–100 °C): casting, RTM/infusion, prepreg autoclave cure (180 °C typical) or transfer moulding at 165–185 °C with 60–180 s gel; a 180–200 °C post-cure is needed to reach full Tg, and high exotherm plus ~1–2 % cure shrinkage require thin sections or filler loading.
What is the maximum service temperature of EPN Tough?
EPN Tough is rated for continuous use to about 155°C (311 °F), and briefly to 220°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Epoxy phenol novolac resin (EPN-type) technical data — Huntsman Advanced Materials (2020)
- Novolac epoxy resins EPICLON N-770 / N-680 series — DIC Corporation (2022)
- Phenol/cresol novolac epoxy KD-211 / F-51 series — Kukdo Chemical / (2023)
- Engineered Materials Handbook Vol.3: Adhesives and Sealants / Vol.1 Composites — ASM International (1990)
- Epoxy Resins: Chemistry and Technology, 2nd ed. — Marcel Dekker (1988)
- GB/T 13657 Solid epoxy resin / GB/T 2567 Test methods for cast resin properties — SAC (2021)
- ISO 527 / ISO 178 / ISO 75 / IEC 60243 / UL 94 — ISO, IEC, UL (2019)
- Semiconductor epoxy molding compound (EMC) property tables — Sumitomo Bakelite / Hysol (2021)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.