PEN UF (Unfilled / Natural)
Grade · default condition
Baseline PEN homopolyester resin for moulded parts, sheet and film precursor when maximum barrier/heat over PET is wanted.
Values for the UF condition
Other PEN grades and fills
PEN is listed in 5 conditions; see the grade overview at PEN.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
PEN/PET copolyester or blend | Cost-down route: 10–50 % naphthalate in a PET backbone lifts Tg and barrier partway to PEN while keeping PET-like processing. | 65 | 70 | 90 | 82 Shore D |
UFDefaultThis page Unfilled / Natural | Baseline PEN homopolyester resin for moulded parts, sheet and film precursor when maximum barrier/heat over PET is wanted. | 78 | 80 | 40 | 85 Shore D |
Bottle / blow-moulding grade | High intrinsic-viscosity resin for stretch-blow-moulded refillable beer/hot-fill bottles where CO₂-O₂ barrier, caustic-wash and 85–95 °C fill resistance beat PET. | 80 | 85 | 60 | 84 Shore D |
15 % glass-fibre reinforced | Moderate stiffness/heat upgrade with still-usable toughness for thin-wall electrical parts. | — | 120 | 4 | — |
30 % glass-fibre reinforced | Choose for stiff, dimensionally stable parts needing HDT well above Tg (connectors, coil bobbins, SMT-adjacent hardware). | — | 160 | 2.5 | — |
What is PEN UF?
PEN UF is PEN in the UF grade — baseline PEN homopolyester resin for moulded parts, sheet and film precursor when maximum barrier/heat over PET is wanted. PEN UF has a yield strength of 78 MPa (11.3 ksi) and a tensile strength of 80 MPa (11.6 ksi) — stronger than 86% of polymer grades. Elongation at break is 40% and the elastic modulus is 2.8 GPa (0.406 Msi). PEN UF has a density of 1.36 g/cm³ (0.0491 lb/in³), heavier than 75% of polymer grades. Its glass-transition temperature is 122°C (252 °F).
Advantages
- High strength — 78 MPa (11.3 ksi), better than 86% of polymer grades
- Good UV / weathering resistance — 80/100, better than 86% of polymer grades
- Tough — resists crack growth — 3.5 MPa·√m (3.19 ksi·√in), better than 81% of polymer grades
- 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
- Heavy — 1.36 g/cm³ (0.0491 lb/in³), worse than 75% of polymer grades
PEN UF properties
Typical room-temperature values for PEN UF; 26 are specific to this condition. Other listed values are PEN reference data and may not represent this condition. Bars are the position among polymer grades.
Physical7
PEN UF has a density of 1.36 g/cm³ (0.0491 lb/in³), heavier than 75% of polymer grades. Its glass-transition temperature is 122°C (252 °F).
Mechanical17
PEN UF has a yield strength of 78 MPa (11.3 ksi) and a tensile strength of 80 MPa (11.6 ksi) — stronger than 86% of polymer grades. Elongation at break is 40% and the elastic modulus is 2.8 GPa (0.406 Msi).
Thermal11
PEN UF is rated for continuous service to 155°C (311 °F). It conducts heat at 0.24 W/m·K (0.139 BTU/hr·ft·°F), better than 67% of polymer grades. Thermal expansion is 60 µm/m·K (33.3 µin/in·°F).
Electrical7
PEN UF is an electrical insulator with a dielectric strength of 30 kV/mm (762 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (76/100), worse than 64% of polymer grades. UV resistance is very good.
Sustainability4
Producing a kilogram of PEN UF takes about 110 MJ of energy and emits 5.5 kg of CO₂ — more than 64% of polymer grades. Typical recycled content is 0%.
Manufacturability7
PEN UF's machinability is good (60/100, better than 51% of polymer grades); weldability good (60/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with PEN UF
Is PEN easy to machine?
Machines like rigid polyester with sharp carbide tools, high speed and light feed; notch-sensitive, so avoid sharp internal corners and anneal near 130–150 °C to relieve stress.
Can PEN be welded?
Ultrasonic, heat-seal, hot-plate and laser welding all work; adhesive bonding needs corona/plasma or primer because the film surface is low-energy.
Can PEN be formed, bent or molded?
Dry to <0.02 % moisture (150 °C, 4–6 h), melt at 285–315 °C and hold moulds at 90–140 °C for crystallisation; slower crystallisation than PET means longer cycles or nucleated grades.
What surface finishes work on PEN?
Not paintable without pretreatment; films are supplied corona-treated, metallised (Al/Cu) or hard-coated, and the natural UV absorption gives good outdoor colour retention.
PEN 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 |
|---|---|---|
| 2,6-naphthalenedicarboxylate unit (from wt% of repeat unit C14H10O4; 1:1 mole with the glycol | 85 – 90 | 88.4 |
| Sb / Ti / Ge polycondensation catalystresidual catalyst + phosphorus stabiliser | 0.01 – 0.05 | 0.03 |
| glass fiber0 for the default unfilled grade; 15–40 % in GF variants | 0 – 40 | 0 |
| ethylene glycol unitdiol residue; small amounts of DEG form in situ | ≥ 10 (balance) | — |
PEN UF — frequently asked
What is PEN UF used for?
PEN UF is typically used for high-performance flexible circuit film, hot-fill and premium beverage bottles, photographic/industrial film, capacitor film and solar backsheet film. In short: highest-temperature standard polyester; better barrier than PET; costlier PET upgrade.
What is the yield strength of PEN UF?
PEN UF has a typical yield strength of 78 MPa (11.3 ksi) and a tensile strength of 80 MPa (11.6 ksi) — stronger than 86% of polymer grades. Strength varies by condition: see the 5 listed tempers.
Is PEN UF easy to machine?
Reasonably — machinability is rated good (60/100, better than 51% of polymer grades). Machines like rigid polyester with sharp carbide tools, high speed and light feed; notch-sensitive, so avoid sharp internal corners and anneal near 130–150 °C to relieve stress.
Can PEN UF be welded?
Yes — weldability is rated good (60/100). Ultrasonic, heat-seal, hot-plate and laser welding all work; adhesive bonding needs corona/plasma or primer because the film surface is low-energy.
What surface finishes work on PEN UF?
Not paintable without pretreatment; films are supplied corona-treated, metallised (Al/Cu) or hard-coated, and the natural UV absorption gives good outdoor colour retention.
Can PEN UF be formed, bent or molded?
Dry to <0.02 % moisture (150 °C, 4–6 h), melt at 285–315 °C and hold moulds at 90–140 °C for crystallisation; slower crystallisation than PET means longer cycles or nucleated grades.
What is the maximum service temperature of PEN UF?
PEN UF 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.
What is the difference between PEN UF and PEN COPO?
UF is the default condition — baseline PEN homopolyester resin for moulded parts, sheet and film precursor when maximum barrier/heat over PET is wanted. COPO: cost-down route: 10–50 % naphthalate in a PET backbone lifts Tg and barrier partway to PEN while keeping PET-like processing. Yield strength is 78 MPa in UF versus 65 MPa in COPO.
Sources
- Teonex PEN Film — technical and electrical properties — DuPont Teijin Films (2021)
- Teijin PEN resin (TN8065S etc.) processing and property data — Teijin (2020)
- Engineered Materials Handbook Vol. 2: Engineering Plastics — ASM International (1988)
- Polymer Handbook (thermal/optical data for poly(ethylene 2,6-naphthalate)) — Wiley (1999)
- ISO 527 / ISO 178 / ISO 75 / ASTM D256 test methods — ISO / ASTM (2019)
- CAMPUS / UL Prospector polyester datasheets — CWFG / UL (2023)
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.