Delrin (Acetal/POM): Properties, Uses, and Applications
Representative Infinita Engineering Visual explaining the four-step workflow for Delrin Acetal Uses.What Is Delrin?
Delrin is DuPont’s brand name for acetal homopolymer (POM-H), one of two major polyoxymethylene (POM) formulations — the other being acetal copolymer (POM-C) from manufacturers like Celanese and BASF. Both fall under the generic “acetal” or “polyacetal” designation, but differ meaningfully in mechanical performance and chemical resistance, which drives which one is right for a given application.
Delrin (POM-H) vs. Acetal Copolymer (POM-C)
- Delrin (POM-H): higher crystallinity, giving superior tensile strength (approximately 70 MPa), stiffness, hardness, and fatigue resistance versus copolymer grades; can exhibit centerline porosity in larger cross-sections
- Acetal copolymer (POM-C): slightly lower mechanical properties in exchange for better chemical and hydrolysis resistance, improved thermal stability, and lower centerline porosity — preferred for parts exposed to hot water or aggressive chemicals
- Melting point: POM-C softens around 160-175°C, while POM-H (Delrin) melts at a slightly higher 172-184°C
Key Material Properties
Both POM formulations offer low friction, high stiffness, excellent dimensional stability, and very low moisture absorption — properties that let POM hold tighter machining tolerances and finer surface finishes than most engineering plastics. Standard CNC-machined tolerances of ±0.005 to ±0.010 inches are achievable without special precautions, with optimised tooling and process control pushing to ±0.002 inches or better on critical dimensions.
Common Applications
- Precision gears, bushings, and bearings, where low friction and self-lubrication reduce the need for external lubricants
- Snap-fit features and springs, leveraging POM-H’s superior fatigue resistance
- Pump housings and sliding trays, where dimensional stability under load matters
- Fuel system components and fasteners, particularly acetal copolymer grades for chemical resistance
Machining Considerations
POM machines cleanly with minimal tool wear, holding tight tolerances and fine finishes due to its low moisture absorption and moderate thermal expansion. Thin walls and deep cavities should be avoided in part design where possible, since they increase machining time and risk part damage or distortion during production; thread depth is typically kept under three times the hole diameter to control machining time and cost.
Limitations
All POM formulations degrade under prolonged sunlight/UV exposure and begin to soften above approximately 120°C, limiting their suitability for outdoor or elevated-temperature applications without added UV stabilization or a different material choice entirely.
Industry Specifications Referencing Delrin/Acetal
- Common comparison materials: nylon (similar strength/wear resistance, more moisture-sensitive), PTFE (lower friction, lower strength), PEEK (higher temperature capability, higher cost)
- Typical test methods: ASTM D638 (tensile), D785 (Rockwell hardness for plastics), D256 (impact)
Conclusion
The Delrin-versus-copolymer decision usually comes down to environment: dry, precision-critical applications favour Delrin’s superior strength and stiffness, while wet or chemically aggressive environments favour copolymer’s better hydrolysis and chemical resistance — both machine well, so the choice is a materials decision, not a manufacturing one.
What is the difference between Delrin and acetal? Acetal is the general name for POM plastics, while Delrin refers to a specific acetal homopolymer product family. Acetal materials are available as homopolymers and copolymers. Homopolymers generally provide greater stiffness and strength, while copolymers may offer better resistance to hot water, chemicals, and long-term thermal degradation.
What are the main properties of Delrin? Delrin combines high tensile strength, rigidity, fatigue resistance, low moisture absorption, and good dimensional stability. It also has a naturally low coefficient of friction and good resistance to abrasion. These properties make it suitable for moving parts, precision-machined components, and applications where metals may be unnecessarily heavy or expensive.
What are the common uses of Delrin? Delrin is commonly used for gears, bearings, bushings, rollers, pulleys, fasteners, valve parts, electrical components, conveyor parts, and precision housings. It is also found in automotive systems, consumer products, industrial machinery, medical equipment, and fluid-handling assemblies where low friction and dimensional accuracy are important.
Why is Delrin used for gears and bearings? Delrin has low friction, good wear resistance, high fatigue strength, and the ability to operate with limited lubrication. These characteristics help reduce noise and wear in gears, bearings, and sliding components. Its low weight and corrosion resistance can also make it a practical alternative to certain metal components.
Is Delrin chemically resistant? Delrin provides good resistance to many fuels, oils, greases, solvents, and neutral chemicals. However, it can be damaged by strong acids, strong oxidizing agents, and prolonged exposure to certain aggressive chemicals. Chemical compatibility should be evaluated using the actual concentration, temperature, exposure duration, and mechanical loading conditions.
Other Categories
