acetal H (Delrin)
acetal H
Polyoxymethylene Homopolymer (pom-h)
Polyoxymethylene Homopolymer (pom-h)
Acetal H, technically known as Polyoxymethylene Homopolymer (and frequently referred to by the brand name Delrin®), is a high-performance engineering thermoplastic. It is characterised by its high degree of crystallinity which provides superior mechanical strength, stiffness, and hardness compared to its copolymer counterpart (Acetal C).
While both acetal variants offer excellent machinability and dimensional stability, Acetal H is specifically engineered for high-load applications where maximum rigidity and fatigue resistance are required. It bridges the gap between metals and ordinary plastics, making it a staple in precision mechanical engineering.
Key Properties
Mechanical & Physical
- Superior Tensile Strength
Approximately 10–15% stronger than Acetal C, making it ideal for high-load structural parts. - High Rigidity and Hardness
Exceptional stiffness and surface hardness for load-bearing components. - Excellent Fatigue Resistance
Capable of withstanding repeated loading and unloading cycles without failure. - Low Coefficient of Friction
Like all acetals, Acetal H is self-lubricating and provides excellent sliding properties against metals and other plastics. - Exceptional Creep Resistance
Maintains its shape under long-term mechanical stress better than most other thermoplastics.
Chemical & Thermal
- Higher Melting Point
AcetAL H has a melting peak roughly 10°C higher than the copolymer version (Acetal C). - Low Moisture Absorption
Maintains dimensional stability in humid environments (though slightly more susceptible to hot water than Acetal C) - Centerline Porosity
This is a characteristic where the core of extruded shapes may contain small voids. This is a byproduct of the Acetal H manufacturing process and is the primary reason why Acetal C is often preferred for precision manifold blocks. - Regulatory Compliance
Most grades are FDA, USDA, and EU compliant for direct contact with food.
COMMON APPLICATIONS
Technical Details
| TEST METHOD | VALUE | VALUE (IMPERIAL) | |
|---|---|---|---|
| PHYSICAL PROPERTIES | |||
| Density | ISO 1183 | 1.42–1.43 g/cm³ | 0.052 lb/in³ |
| Water Absorption (24h) | ISO 62 | 0.25% | 0.25% |
| Water Absorption (Saturation) | ISO 62 | 0.90% | 0.90% |
| MECHANICAL PROPERTIES (at 23°C) | |||
| Tensile Strength at Yield | ISO 527 | 75–80 MPa | 11,000–11,600 psi |
| Tensile Modulus of Elasticity | ISO 527 | 3,100–3,400 MPa | 450–495 ksi |
| Elongation at Yield | ISO 527 | 12% | 12% |
| Elongation at Break | ISO 527 | 25–40% | 25–40% |
| Flexural Strength | ISO 178 | 100–110 MPa | 14,500–16,000 psi |
| Flexural Modulus | ISO 178 | 3,000–3,200 MPa | 35–465 ksi |
| Charpy Impact (Notched) | ISO 179 | 8–10 kJ/m² | 3.8–4.7 ft-lb/in² |
| Rockwell Hardness | ISO 2039-2 | M 94 / R 120 | M 94 / R 120 |
| THERMAL PROPERTIES | |||
| Melting Temperature | ISO 11357 | 175–178°C | 347–352°F |
| Heat Deflection Temp (1.8 MPa) | ISO 75 | 115–124°C | 239–255°F |
| Max. Service Temp (Long Term) | 90–105°C | 194–221°F | |
| Min. Service Temp | -50°C | -58°F | |
| Thermal expansion (CLTE) | ISO 11359 | 100 x 10⁻⁶/K | 5.5 x 10⁻⁵/°F |
| Thermal Conductivity | 0.37 W/(K·m) | 2.56 BTU·in/(hr·ft²·°F) | |
| Flammability Rating | UL 94 | HB | HB |
| ELECTRICAL PROPERTIES | |||
| Dielectric Strength | IEC 60243 | 20–35 kV/mm | |
| Volume Resistivity | IEC 60093 | 10¹⁴ – 10¹⁵ Ω·cm | |
| Surface Resistivity | IEC 60093 | > 10¹³ Ω | |
| Dielectric Constant (1 MHz) | IEC 60250 | 3.7 | |
| Dissipation Factor (1 MHz) | IEC 60250 | 0.005 | |
| Dielectric Constant (100 Hz) | IEC 60250 | 3.8 | |
| Dissipation Factor (100 Hz) | IEC 60250 | 0.003 | |
| Comparative Tracking Index (CTI) | IEC 60112 | 600 V |
These values are typical averages and should be used for material selection and design guidance only.
Technical Details
| TEST METHOD | VALUE | |
|---|---|---|
| PHYSICAL PROPERTIES | ||
| Density | ISO 1183 | 1.42–1.43 g/cm³ |
| Water Absorption (24h) | ISO 62 | 0.25% |
| Water Absorption (Saturation) | ISO 62 | 0.90% |
| MECHANICAL PROPERTIES | ||
| Tensile Strength at Yield | ISO 527 | 75–80 MPa |
| Tensile Modulus of Elasticity | ISO 527 | 3,100–3,400 MPa |
| Elongation at Yield | ISO 527 | 12% |
| Elongation at Break | ISO 527 | 25–40% |
| Flexural Strength | ISO 178 | 100–110 MPa |
| Flexural Modulus | ISO 178 | 3,000–3,200 MPa |
| Charpy Impact (Notched) | ISO 179 | 8–10 kJ/m² |
| Rockwell Hardness | ISO 2039-2 | M 94 / R 120 |
| THERMAL PROPERTIES | ||
| Melting Temperature | ISO 11357 | 175–178°C |
| Heat Deflection Temp (1.8 MPa) | ISO 75 | 115–124°C |
| Max. Service Temp (Long Term) | 90–105°C | |
| Min. Service Temp | -50°C | |
| Thermal expansion (CLTE) | ISO 11359 | 100 x 10⁻⁶/K |
| Thermal Conductivity | 0.37 W/(K·m) | |
| Flammability Rating | UL 94 | HB |
| ELECTRICAL PROPERTIES | ||
| Dielectric Strength | IEC 60243 | 20–35 kV/mm |
| Volume Resistivity | IEC 60093 | 10¹⁴ – 10¹⁵ Ω·cm |
| Surface Resistivity | IEC 60093 | > 10¹³ Ω |
| Dielectric Constant (1 MHz) | IEC 60250 | 3.7 |
| Dissipation Factor (1 MHz) | IEC 60250 | 0.005 |
| Dielectric Constant (100 Hz) | IEC 60250 | 3.8 |
| Dissipation Factor (100 Hz) | IEC 60250 | 0.003 |
| Comparative Tracking Index | IEC 60112 | 600 V |
These values are typical averages and should be used for material selection and design guidance only.
CHEMICAL RESISTANCE
| CATEGORY | REPRESENTATIVE SUBSTANCE | RATING | NOTES |
|---|---|---|---|
| Acids (Weak) | Acetic Acid, Citric Acid | C | Even mild acids (pH < 4) can trigger polymer "unzipping." |
| Acids (Strong) | Sulfuric or Hydrochloric Acid | C | Do not use. Rapidly decomposes the polymer |
| Alcohols | Ethanol, Isopropanol, Methanol | A | Excellent resistance |
| Alkalis (Bases) | Sodium Hydroxide, Ammonia | C | Do not use. Unlike Acetal C, Acetal H is attacked by strong bases. |
| Aromatic Hydrocarbons | Benzene, Toluene | A | Highly stable |
| Chlorinated Solvents | Methylene Chloride | B | Good for short-term; long-term exposure causes swelling |
| Fuels | Petrol, Diesel, Kerosene | A | Excellent; the industry standard for fuel-system gears. |
| Ketones | Acetone, Methyl Ethyl Ketone (MEK) | A | Generally very resistant |
| Oxidizing Agents | Bleach, Hydrogen Peroxide | C | Causes brittleness and surface chalking |
| Water / Steam | Hot Water (>60°C), Steam | C | Prone to hydrolysis; Acetal C is much better for hot water. |
RATING SCALE:
A (Excellent): Little to no effect.
B (Good/Fair): Minor swelling or slight changes in properties; acceptable for short-term exposure.
C (Poor): Severe degradation or stress cracking. Not recommended.
CHEMICAL RESISTANCE
| CATEGORY | EXAMPLE | RATING |
|---|---|---|
| Acids (Weak) | Acetic Acid Citric Acid | C |
| Acids (Strong) | Sulfuric or Hydrochloric Acid | C |
| Alcohols | Ethanol, Isopropanol | A |
| Alkalis (Bases) | Sodium Hydroxide | C |
| Aromatic Hydrocarbons | Benzene, Toluene | A |
| Chlorinated Solvents | Methylene Chloride | B |
| Fuels | Petrol, Diesel, Kerosene | A |
| Ketones | Acetone, Methyl Ethyl Ketone (MEK) | A |
| Oxidizing Agents | Bleach Hydrogen Peroxide | C |
| Water / Steam | Hot Water (>60°C) | C |
RATING SCALE:
A (Excellent): Little to no effect.
B (Good/Fair): Minor swelling or slight changes in properties; acceptable for short-term exposure.
C (Poor): Severe degradation or stress cracking. Not recommended.
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Plastock has extensive experience in all cutting, laser and manufacturing techniques across a huge range of industries and materials using the latest technologies. With expert engineering knowledge and world class equipment, we can help with the design, development, fabrication and installation or your project. No job is too big or too small.
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