XX
Grade · default condition
ASTM D709 Grade XX
XX = general-purpose mechanical/electrical paper-phenolic sheet
Default machining grade: best balance of strength, electrical properties and cost for milled or drilled insulation parts.
Values for the XX condition
Other XX grades and fills
XX is listed in 7 conditions; see the grade overview at XX.
Compare all 7 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Thin cold-punch paper-phenolic | Thin-sheet grade that cold-punches cleanly at 0.8–1.6 mm; historic single-sided PCB substrate. | — | 85 | 2 | 95 HRM |
Cold-punching mechanical paper-phenolic | Use where room-temperature punching of gaskets/washers is the priority and electrical values are secondary. | — | 90 | 2 | 95 HRM |
Flame-retardant paper-phenolic, UL 94 V-0 | Specify when a V-0 rating is mandatory (consumer electronics, appliance insulation) in a paper-phenolic price class. | — | 95 | 1.8 | 100 HRM |
Hot-punching paper-phenolic | Choose when thin blanks must be punched at 80–130 °C without cracking, while keeping near-XX insulation values. | — | 105 | 1.7 | 100 HRM |
High-electrical punching grade paper-phenolic | Best combination of low dielectric loss and clean punching; classic terminal-board and coil-form material. | — | 105 | 1.6 | 100 HRM |
High-humidity electrical paper-phenolic | Pick for radio-frequency / high-humidity insulation where lower loss and lower moisture pickup matter more than strength. | — | 110 | 1.4 | 105 HRM |
XXDefaultThis page General-purpose mechanical/electrical paper-phenolic sheet | Default machining grade: best balance of strength, electrical properties and cost for milled or drilled insulation parts. | — | 120 | 1.5 | 105 HRM |
What is XX?
XX is XX in the XX grade — default machining grade: best balance of strength, electrical properties and cost for milled or drilled insulation parts. XX has a tensile strength of 120 MPa (17.4 ksi), weaker than 61% of composite grades. Elongation at break is 1.5% and the elastic modulus is 8 GPa (1.16 Msi). XX has a density of 1.35 g/cm³ (0.0488 lb/in³), lighter than 75% of composite grades. Its glass-transition temperature is 145°C (293 °F).
Advantages
- Easy to machine — 80/100, better than 85% of composite grades
- Low embodied carbon — 4.5 kg CO₂/kg, better than 79% of composite grades
- Lightweight — 1.35 g/cm³ (0.0488 lb/in³), better than 75% of composite grades
Limitations
- Low fracture toughness — 1.8 MPa·√m (1.64 ksi·√in), worse than 90% of composite grades
- Degrades in UV without stabilisers — 25/100, worse than 86% of composite grades
- Needs corrosion protection — 60/100, worse than 79% of composite grades
- Limited service temperature — 120°C (248 °F), worse than 78% of composite grades
- Poor heat conductor — 0.25 W/m·K (0.144 BTU/hr·ft·°F), worse than 76% of composite grades
XX properties
Typical room-temperature values for XX; 19 are specific to this condition. Other listed values are XX reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
XX has a density of 1.35 g/cm³ (0.0488 lb/in³), lighter than 75% of composite grades. Its glass-transition temperature is 145°C (293 °F).
Mechanical12
XX has a tensile strength of 120 MPa (17.4 ksi), weaker than 61% of composite grades. Elongation at break is 1.5% and the elastic modulus is 8 GPa (1.16 Msi).
Thermal8
XX is rated for continuous service to 120°C (248 °F). It conducts heat at 0.25 W/m·K (0.144 BTU/hr·ft·°F), worse than 76% of composite grades. Thermal expansion is 25 µm/m·K (13.9 µin/in·°F).
Electrical7
XX is an electrical insulator with a dielectric strength of 15 kV/mm (381 V/mil) and a resistivity of 1×10¹⁰ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (60/100), worse than 79% of composite grades. UV resistance is poor.
Sustainability3
Producing a kilogram of XX takes about 80 MJ of energy and emits 4.5 kg of CO₂ — less than 84% of composite grades. Typical recycled content is 0%.
Manufacturability2
XX's machinability is very good (80/100, better than 85% of composite grades).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with XX
Is XX easy to machine?
Cuts, drills and taps easily with carbide tooling and high rake; dust is abrasive and irritating, so use vacuum extraction and back-up plates to avoid exit-side delamination.
Can XX be welded?
Not weldable — thermoset; join by bolting, riveting or epoxy/phenolic adhesive bonding after abrasion and solvent wipe.
Can XX be formed, bent or molded?
Supplied fully cured and cannot be post-formed; blanking is done by punching (warm the sheet to 80–130 °C for XX/XXP, room temperature only for XP/XPC/thin stock).
What surface finishes work on XX?
Sanded or scraped to thickness; edges deburr readily; may be sealed with varnish or epoxy to limit moisture pickup, but plating and anodizing do not apply.
XX 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 |
|---|---|---|
| cellulose paper (kraft/alpha) reinforcemlayered paper webs, resin-impregnated | 45 – 60 | 55 |
| processing aids / plasticizer / release | 0 – 3 | 2 |
| phenol-formaldehyde (resole/novolac) resthermoset matrix, fully cured | ≥ 38 (balance) | — |
XX — frequently asked
What is XX used for?
XX is typically used for punched insulating washers, terminal strips and low-voltage PCB substrates. In short: cleanest-punching paper phenolic; pre-FR-4 board material; low-cost punched insulation.
What is the tensile strength of XX?
XX has a typical tensile strength of 120 MPa (17.4 ksi) — weaker than 61% of composite grades. Strength varies by condition: see the 7 listed tempers.
Is XX easy to machine?
Yes — machinability is rated very good (80/100, better than 85% of composite grades). Cuts, drills and taps easily with carbide tooling and high rake; dust is abrasive and irritating, so use vacuum extraction and back-up plates to avoid exit-side delamination.
Can XX be welded?
Not weldable — thermoset; join by bolting, riveting or epoxy/phenolic adhesive bonding after abrasion and solvent wipe.
What surface finishes work on XX?
Sanded or scraped to thickness; edges deburr readily; may be sealed with varnish or epoxy to limit moisture pickup, but plating and anodizing do not apply.
Can XX be formed, bent or molded?
Supplied fully cured and cannot be post-formed; blanking is done by punching (warm the sheet to 80–130 °C for XX/XXP, room temperature only for XP/XPC/thin stock).
What is the maximum service temperature of XX?
XX is rated for continuous use to about 120°C (248 °F), and briefly to 150°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D709 — Standard Specification for Laminated Thermosetting Materials — ASTM International (2017)
- NEMA LI 1 — Industrial Laminated Thermosetting Products — NEMA (1998)
- Paper-phenolic laminate grade data (XX, XXP, XXX, XXXP, XPC) — Norplex-Micarta (2022)
- Engineered Materials Handbook, Vol. 2: Engineering Plastics — ASM International (1988)
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.