PTT UNF
Reinforced grade · default condition
also Sorona, Corterra
UNF = unfilled / Natural injection-molding resin
General-purpose PTT for tough, glossy, dimensionally stable parts where service temperature stays below ~90 °C.
Values for the UNF condition
Other PTT grades and fills
PTT is listed in 9 conditions; see the grade overview at PTT.
Compare all 9 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Impact-modified (toughened) PTT | Elastomer-toughened compound for snap-fits, sporting goods and cold-impact parts where ductility beats stiffness. | 40 | 44 | 150 | 68 Shore D |
Flame-retardant, unfilled | Halogen-containing or halogen-free FR compound for electrical enclosures needing V-0 at 1.5 mm. | 50 | 52 | 8 | 79 Shore D |
Mineral (talc) filled, 20–30 % | Choose when low warpage, isotropic shrinkage and a smooth painted surface matter more than peak strength. | 52 | 52 | 4 | 82 Shore D |
Heat-stabilized | Antioxidant-boosted compound for long-term thermal ageing (e.g. 1000 h+ at 120–140 °C) in automotive electrical parts. | 57 | 60 | 20 | 78 Shore D |
UNFDefaultThis page Unfilled / Natural injection-molding resin | General-purpose PTT for tough, glossy, dimensionally stable parts where service temperature stays below ~90 °C. | — | 62 | 25 | — |
15 % glass-fiber reinforced | Entry-level stiffening with much higher heat distortion temperature while keeping reasonable toughness and surface appearance. | — | 100 | 3.5 | — |
GF30 + flame retardant | Structural FR grade for connectors, relay bases and breaker parts requiring V-0 plus high HDT. | — | 120 | 2 | 88 Shore D |
30 % glass-fiber reinforced | Workhorse structural grade: HDT above 200 °C, high stiffness and low shrinkage for connectors, housings and under-hood parts. | — | 138 | 2.5 | — |
45 % glass-fiber reinforced | Maximum stiffness/creep resistance PTT for metal-replacement brackets and load-bearing electrical parts. | — | 165 | 2 | — |
What is PTT UNF?
PTT UNF is PTT in the UNF grade — general-purpose PTT for tough, glossy, dimensionally stable parts where service temperature stays below ~90 °C. PTT UNF has a yield strength of 58 MPa (8.41 ksi) and a tensile strength of 62 MPa (8.99 ksi) — stronger than 66% of polymer grades. Elongation at break is 25% and the elastic modulus is 2.7 GPa (0.392 Msi). PTT UNF has a density of 1.32 g/cm³ (0.0477 lb/in³), heavier than 72% of polymer grades. Its glass-transition temperature is 50°C (122 °F).
Advantages
- Low embodied carbon — 3 kg CO₂/kg, better than 83% of polymer grades
PTT UNF properties
Typical room-temperature values for PTT UNF; 13 are specific to this condition. Other listed values are PTT reference data and may not represent this condition. Bars are the position among polymer grades.
Physical6
PTT UNF has a density of 1.32 g/cm³ (0.0477 lb/in³), heavier than 72% of polymer grades. Its glass-transition temperature is 50°C (122 °F).
Mechanical16
PTT UNF has a yield strength of 58 MPa (8.41 ksi) and a tensile strength of 62 MPa (8.99 ksi) — stronger than 66% of polymer grades. Elongation at break is 25% and the elastic modulus is 2.7 GPa (0.392 Msi).
Thermal11
PTT UNF is rated for continuous service to 90°C (194 °F). It conducts heat at 0.21 W/m·K (0.121 BTU/hr·ft·°F), better than 55% of polymer grades. Thermal expansion is 80 µm/m·K (44.4 µin/in·°F).
Electrical7
PTT UNF is an electrical insulator with a dielectric strength of 22 kV/mm (558.8 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (78/100), worse than 61% of polymer grades. UV resistance is fair.
Sustainability4
Producing a kilogram of PTT UNF takes about 70 MJ of energy and emits 3 kg of CO₂ — less than 93% of polymer grades. Typical recycled content is 0%.
Manufacturability8
PTT UNF's machinability is good (65/100, better than 66% of polymer grades); weldability very good (70/100); formability fair (50/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with PTT UNF
Is PTT easy to machine?
Machines like PBT/PET — sharp positive-rake tools, high speed, low feed and air cooling; glass-filled grades are abrasive and need carbide or PCD.
Can PTT be welded?
Joins well by ultrasonic, vibration, hot-plate and laser welding; solvent bonding is poor, so use epoxy or cyanoacrylate for adhesive joints.
Can PTT be formed, bent or molded?
Dry to <0.02 % moisture (120–130 °C, 3–4 h) before molding; melt 240–265 °C, mold 40–90 °C (higher for filled grades), fast crystallization gives short cycles and low warpage.
What surface finishes work on PTT?
Takes high-gloss mold finishes and disperse dyes readily; paint/print after flame or plasma treatment, and avoid hot alkaline cleaning which hydrolyzes the surface.
PTT 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 |
|---|---|---|
| 1,3-propanediol (PDO)diol residue in repeat unit; bio-PDO from corn sugar in Sorona | 34 – 39 | 37 |
| Ti/Sn polycondensation catalysttitanate or tin catalyst residue | 0 – 0.02 | 0.01 |
| heat/UV stabilizer packagegrade dependent | 0 – 1 | 0.3 |
| glass fiber0 for the default unfilled grade; 15/30/45 % in reinforced variants | 0 – 45 | 0 |
| terephthalic acid (PTA/DMT) residuediacid residue, ~63 wt% of repeat unit C11H10O4 | balance | — |
PTT UNF — frequently asked
What is PTT UNF used for?
PTT UNF is typically used for carpet and textile fiber, apparel fabric with stretch recovery, engineering resin for connectors and automotive interior trim fiber. In short: elastic-recovery polyester; between PET and PBT; fast cycles, low warpage.
What is the yield strength of PTT UNF?
PTT UNF has a typical yield strength of 58 MPa (8.41 ksi) and a tensile strength of 62 MPa (8.99 ksi) — stronger than 66% of polymer grades. Strength varies by condition: see the 9 listed tempers.
Is PTT UNF easy to machine?
Reasonably — machinability is rated good (65/100, better than 66% of polymer grades). Machines like PBT/PET — sharp positive-rake tools, high speed, low feed and air cooling; glass-filled grades are abrasive and need carbide or PCD.
Can PTT UNF be welded?
Yes — weldability is rated very good (70/100). Joins well by ultrasonic, vibration, hot-plate and laser welding; solvent bonding is poor, so use epoxy or cyanoacrylate for adhesive joints.
What surface finishes work on PTT UNF?
Takes high-gloss mold finishes and disperse dyes readily; paint/print after flame or plasma treatment, and avoid hot alkaline cleaning which hydrolyzes the surface.
Can PTT UNF be formed, bent or molded?
Dry to <0.02 % moisture (120–130 °C, 3–4 h) before molding; melt 240–265 °C, mold 40–90 °C (higher for filled grades), fast crystallization gives short cycles and low warpage.
What is the maximum service temperature of PTT UNF?
PTT UNF is rated for continuous use to about 90°C (194 °F), and briefly to 140°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between PTT UNF and PTT IM?
UNF is the default condition — general-purpose PTT for tough, glossy, dimensionally stable parts where service temperature stays below ~90 °C. IM: elastomer-toughened compound for snap-fits, sporting goods and cold-impact parts where ductility beats stiffness. Yield strength is 58 MPa in UNF versus 40 MPa in IM.
Sources
- Sorona EP thermoplastic polymer product & processing guides — DuPont / Covation Biomaterials (2022)
- Corterra PTT polymer technical bulletins — Shell Chemicals / Zhejiang PTT producers (2005)
- Handbook of Thermoplastic Polyesters (PTT chapters) — Wiley-VCH (S. Fakirov, ed.) (2002)
- CAMPUS / UL Prospector polyester (PTT) datasheets — CWFG / UL Solutions (2024)
- ISO 527 / ISO 178 / ISO 75 / ASTM D256 test methods for thermoplastics — ISO / ASTM (2019)
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.