POM-H HI ST (Solution annealed)
Heat-treated state · default condition
also Delrin 100ST, Tenac-C 4520
Pick when maximum notched impact and ductile failure down to -40 °C matter more than stiffness (Delrin 100ST class).
Values for the ST condition
Other POM-H HI grades and fills
POM-H HI is listed in 6 conditions; see the grade overview at POM-H HI.
Compare all 6 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Internally lubricated toughened grade | For toughened parts that also slide: lower friction and wear against steel, at the cost of some strength and weld-line integrity. | 40 | 40 | 120 | 71 Shore D |
STDefaultThis page Solution annealed | Pick when maximum notched impact and ductile failure down to -40 °C matter more than stiffness (Delrin 100ST class). | 45 | 45 | 220 | 72 Shore D |
Carbon-black pigmented toughened grade | Standard black colour version; carbon black gives moderate light screening at no property penalty. | 45 | 45 | 200 | 72 Shore D |
Heat-stabilized / low-emission toughened grade | For long-term hot-air or hot-oil service (automotive interiors, fuel systems) where formaldehyde emission and thermal ageing must be controlled. | 46 | 46 | 190 | 73 Shore D |
Moderately toughened homopolymer | Best compromise grade: roughly 5x the notched impact of standard POM-H while keeping useful stiffness and HDT (Delrin 100T/500T class). | 52 | 52 | 130 | 76 Shore D |
High-flow toughened injection grade | Choose for thin-wall, multi-cavity or long-flow-path parts where fill pressure limits the low-MFR super-tough grades. | 53 | 53 | 90 | 78 Shore D |
What is POM-H HI ST?
POM-H HI ST is POM-H HI heat treated to ST — pick when maximum notched impact and ductile failure down to -40 °C matter more than stiffness (Delrin 100ST class). POM-H HI ST has a yield strength of 45 MPa (6.53 ksi) and a tensile strength of 45 MPa (6.53 ksi) — weaker than 58% of polymer grades. Elongation at break is 220% and the elastic modulus is 1.4 GPa (0.203 Msi). POM-H HI ST has a density of 1.34 g/cm³ (0.0484 lb/in³), heavier than 74% of polymer grades. Its glass-transition temperature is -60°C (-76 °F).
Advantages
- Tough — resists crack growth — 6.5 MPa·√m (5.92 ksi·√in), better than 100% of polymer grades
- Ductile — tolerates forming and impact — 220%, better than 77% of polymer grades
- Easy to machine — 72/100, better than 76% of polymer grades
Limitations
- Needs corrosion protection — 68/100, worse than 85% of polymer grades
- High mold shrinkage — 2%, worse than 81% of polymer grades
POM-H HI ST properties
Typical room-temperature values for POM-H HI ST; 27 are specific to this condition. Other listed values are POM-H HI reference data and may not represent this condition. Bars are the position among polymer grades.
Physical5
POM-H HI ST has a density of 1.34 g/cm³ (0.0484 lb/in³), heavier than 74% of polymer grades. Its glass-transition temperature is -60°C (-76 °F).
Mechanical16
POM-H HI ST has a yield strength of 45 MPa (6.53 ksi) and a tensile strength of 45 MPa (6.53 ksi) — weaker than 58% of polymer grades. Elongation at break is 220% and the elastic modulus is 1.4 GPa (0.203 Msi).
Thermal11
POM-H HI ST is rated for continuous service to 85°C (185 °F). It conducts heat at 0.25 W/m·K (0.144 BTU/hr·ft·°F), better than 72% of polymer grades. Thermal expansion is 125 µm/m·K (69.4 µin/in·°F).
Electrical7
POM-H HI ST is an electrical insulator with a dielectric strength of 18 kV/mm (457.2 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is good (68/100), worse than 85% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of POM-H HI ST takes about 92 MJ of energy and emits 4.4 kg of CO₂ — less than 74% of polymer grades. Typical recycled content is 0%.
Manufacturability8
POM-H HI ST's machinability is very good (72/100, better than 76% of polymer grades); weldability fair (45/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with POM-H HI ST
Is POM-H HI easy to machine?
Machines cleanly with sharp positive-rake tools and high speed, but the rubber phase makes it gummier than standard POM-H — use light finishing cuts, air blast, and expect stress-relief distortion on thick sections (anneal 150 °C in air).
Can POM-H HI be welded?
Hot-plate, vibration, spin and ultrasonic welding work with moderate joint strength; solvent bonding is impossible and adhesives need flame/plasma or chromic-acid etch pretreatment.
Can POM-H HI be formed, bent or molded?
Dry to <0.1 % moisture if pellets are wet, melt 205–225 °C, mould 80–110 °C, use generous gates and 1.7–2.4 % shrink allowance; avoid melt residence >20 min and never mix with PVC or acidic resins to prevent formaldehyde decomposition.
What surface finishes work on POM-H HI?
Takes machining/tumble finishing and laser marking well; painting, plating or printing require surface activation because of the low-energy, chemically inert surface.
POM-H HI 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 |
|---|---|---|
| elastomer impact modifier (thermoplasticdispersed rubber phase, grade dependent | 10 – 25 | 18 |
| antioxidant / formaldehyde scavenger / athermal stabilizer package | 0.3 – 1.5 | 0.8 |
| lubricant, nucleant, pigmentprocessing aids and colour | 0 – 2.5 | 0.7 |
| polyoxymethylene homopolymer (formaldehyend-capped POM-H resin | ≥ 75 (balance) | — |
POM-H HI ST — frequently asked
What is POM-H HI ST used for?
POM-H HI ST is typically used for seat belt components, snap-fit fasteners, sporting goods hardware and handle and lever mechanisms. In short: toughest acetal grade; ductile at low temperature; snap-fit and clip resin.
What is the yield strength of POM-H HI ST?
POM-H HI ST has a typical yield strength of 45 MPa (6.53 ksi) and a tensile strength of 45 MPa (6.53 ksi) — weaker than 58% of polymer grades. Strength varies by condition: see the 6 listed tempers.
Is POM-H HI ST easy to machine?
Yes — machinability is rated very good (72/100, better than 76% of polymer grades). Machines cleanly with sharp positive-rake tools and high speed, but the rubber phase makes it gummier than standard POM-H — use light finishing cuts, air blast, and expect stress-relief distortion on thick sections (anneal 150 °C in air).
Can POM-H HI ST be welded?
With care — weldability is rated fair (45/100). Hot-plate, vibration, spin and ultrasonic welding work with moderate joint strength; solvent bonding is impossible and adhesives need flame/plasma or chromic-acid etch pretreatment.
What surface finishes work on POM-H HI ST?
Takes machining/tumble finishing and laser marking well; painting, plating or printing require surface activation because of the low-energy, chemically inert surface.
Can POM-H HI ST be formed, bent or molded?
Dry to <0.1 % moisture if pellets are wet, melt 205–225 °C, mould 80–110 °C, use generous gates and 1.7–2.4 % shrink allowance; avoid melt residence >20 min and never mix with PVC or acidic resins to prevent formaldehyde decomposition.
What is the maximum service temperature of POM-H HI ST?
POM-H HI ST is rated for continuous use to about 85°C (185 °F), and briefly to 130°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between POM-H HI ST and POM-H HI HF?
ST is the default condition — pick when maximum notched impact and ductile failure down to -40 °C matter more than stiffness (Delrin 100ST class). HF: choose for thin-wall, multi-cavity or long-flow-path parts where fill pressure limits the low-MFR super-tough grades. Yield strength is 45 MPa in ST versus 53 MPa in HF.
Sources
- Delrin 100ST / 500T acetal homopolymer product data — DuPont / Delrin (Celanese) (2023)
- Tenac / Tenac-C acetal resin grade list — Asahi Kasei (2022)
- CAMPUS plastics database — impact-modified POM homopolymer datasets (ISO 10350-1) — CAMPUS / CWFG (2024)
- Engineered Materials Handbook Vol.2: Engineering Plastics — ASM International (1988)
- ISO 9988-1/-2 Plastics — Polyoxymethylene (POM) moulding and extrusion materials — ISO (2020)
- GB/T 24283 (POM) — SAC (2009)
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.