Polyoxymethylene (POM), also known as acetal or Delrin®, is a high-performance engineering thermoplastic distinguished by its excellent strength, stiffness, and dimensional stability.
Unlike many conventional plastics, POM offers a unique combination of low friction, high wear resistance, and superior machinability, making it ideal for producing precision parts that demand reliability under mechanical stress.
This article provides a comprehensive overview of POM plastic, covering its material characteristics, classifications, processing methods, and common industrial applications.
1. What Is POM Plastic?
POM (Polyoxymethylene) is a crystalline thermoplastic polymer composed of repeating CH₂O molecular units. It exists in two primary forms: homopolymer POM (C₄H₈O₂)n and copolymer POM (C₅H₁₀O₂)n.
Chemically, POM belongs to the polyether family. Its highly ordered molecular structure and tightly packed polymer chains give it exceptional rigidity, strength, and fatigue resistance, which are significantly higher than those of most general-purpose plastics.
A common question is whether POM poses any safety risks because of its relation to formaldehyde. Under normal conditions between –40°C and 120°C, POM remains stable and does not release harmful gases. Only when exposed to excessive heat above 230°C does it begin to decompose and generate trace amounts of formaldehyde. When processed with proper temperature control, POM is safe and suitable even for food-contact applications.
2. Key Properties and Advantages of POM Plastic
POM stands out among engineering plastics because of its balance of strength, machinability, and reliability. Below are its most important characteristics:
High Mechanical Strength and Rigidity:
With a tensile strength of 60–70 MPa and a flexural modulus of up to 3,000 MPa, POM can bear heavy loads without deformation. This makes it suitable for gears, bearings, and other precision moving parts.
Excellent Wear Resistance and Low Friction:
POM has a very low coefficient of friction (0.1–0.3) and high abrasion resistance, enabling smooth motion even without lubrication. It’s widely used in sliders, pulleys, and mechanical guide rails.
Dimensional Stability:
The material absorbs very little moisture and maintains its dimensions across temperatures from –40°C to 100°C, making it reliable for high-precision assemblies.
Chemical and Electrical Resistance:
POM resists many solvents, oils, and greases and acts as an effective electrical insulator, ideal for connectors and switches.
Ease of Processing
POM can be injection molded, extruded, or machined with excellent surface finish and high productivity.
Typical Properties of POM:
| Propiedad | Value Range | Test Standard |
| Densidad (g/cm³) | 1.41–1.42 | ISO 1183 |
| Tensile Strength (MPa) | 60–70 | ISO 527 |
| Flexural Modulus (MPa) | 2,600–3,000 | ISO 178 |
| Impact Strength (KJ/m²) | 15–25 | ISO 179 |
| Coeficiente de fricción | 0.1–0.3 | ASTM D1894 |
| Heat Deflection Temp (°C) | 110–140 | ISO 75 |
While POM performs exceptionally well, it is not perfect. It has poor UV resistance, is flammable, and may emit trace formaldehyde when overheated. Modified grades are often used to enhance these limitations.
3. Types of POM: Homopolymer vs. Copolymer
POM plastic is divided into two main types—homopolymer and copolymer—each offering distinct advantages.
3.1 Homopolymer POM
Made by polymerizing trioxane, the homopolymer POM features a highly regular molecular structure, resulting in a higher crystallinity (75–85%). Key benefits include:
- High mechanical strength: Tensile strength of 70–80 MPa and flexural strength of 100–120 MPa.
- Excellent wear resistance: Up to 30% lower wear rate than copolymer POM.
- Higher heat resistance: Continuous use temperature of 100–110°C, short-term up to 140°C.
However, it also has drawbacks: poor thermal stability during processing and weaker alkali resistance, requiring precise temperature control.
3.2 Copolymer POM
Copolymer POM introduces a small amount of dioxolane (2–5%) during polymerization, reducing crystallinity (60–70%) but improving stability and processability. Advantages include:
- Better thermal stability: Processing window of 165–220°C with less risk of degradation.
- Improved chemical resistance: Resistant to weak alkalis and organic solvents.
- Higher impact strength: Suitable for outdoor or low-temperature environments.
| Propiedad | Homopolymer POM | Copolymer POM | Aplicaciones típicas |
| Crystallinity | 75–85% | 60–70% | – |
| Tensile Strength (MPa) | 70–80 | 60–70 | Load-bearing parts |
| Processing Range (°C) | 175–190 | 165–220 | General molding |
| Alkali Resistance | Poor | Bien | Chemical-contact parts |
| Price | Más alto | Moderado | Cost-sensitive parts |
Copolymer POM dominates the market due to its balanced performance and easier manufacturability.
4. Manufacturing Methods of POM Plastic
POM can be processed through various methods, including injection molding, extrusion, and machining. It melts easily, flows well, and cools quickly, allowing manufacturers to create precise, complex shapes such as gears, housings, and connectors.
| Método | Temperature (°C) | Características principales | Typical Products |
| Moldeo por inyección | 180–210 | Excellent melt flow, low shrinkage, suitable for high-volume production with tight tolerances | Precision gears, automotive housings, buckles |
| Extrusion | 190–200 | Consistent melt strength, smooth surface finish, suitable for continuous profiles | Pipes, rods, plates, film stock |
| Blow Molding | 190–210 | Good melt elasticity, allows uniform wall thickness for hollow parts | Fluid containers, ducts, fuel system components |
| Mecanizado CNC | Room temperature | Excellent dimensional stability, low tool wear, ideal for prototypes and small-batch production | Custom components, precision fittings, test samples |
In all these methods, careful temperature and cooling control are essential to maintain POM’s dimensional accuracy and prevent surface defects or thermal degradation.
5. Applications of POM Plastic
Thanks to its balance of rigidity, wear resistance, and dimensional stability, POM is used across multiple industries:
Industria automotriz
POM is used in parts such as fuel connectors, wiper gears, and seat adjusters. Its excellent wear resistance, low friction, and chemical stability make it suitable for continuous motion and exposure to oils. Copolymer and glass fiber–reinforced grades are commonly selected for better dimensional stability and long-term performance.
Home Appliances
In washing machines, refrigerators, and air conditioners, POM components like gears, hinges, and valve plates ensure smooth operation and a long service life. The copolymer type is preferred due to its good moisture resistance and surface quality.
Maquinaria industrial
POM is often chosen for pump impellers, valve cores, and sliding parts that require low friction and self-lubrication. Both homopolymer and copolymer grades perform well under cyclic stress and fatigue conditions.
Productos de consumo
Everyday items such as zippers, eyeglass hinges, and toy axles benefit from POM’s toughness and smooth finish. Its processability also allows high-volume, cost-effective production.
Dispositivos médicos
Medical-grade POM copolymers are used in surgical clamps and diagnostic device fittings because of their non-toxic nature and ability to withstand sterilization processes.
POM’s versatility across industries stems from its balanced properties: strong yet lightweight, rigid yet easy to process. That makes it one of the most reliable materials for precision plastic components.
6. POM vs. Other Engineering Plastics
POM is often compared with Nylon (PA), Polycarbonate (PC), and Polyester (PBT). Each material has its own strengths:
| Propiedad | POM | Nylon (PA66) | ordenador personal | PBT |
| Densidad (g/cm³) | 1.41–1.42 | 1.13–1.15 | 1.20–1.22 | 1.30–1.38 |
| Tensile Strength (MPa) | 60–70 | 80–90 | 55–75 | 55–65 |
| Impact Strength (KJ/m²) | 15–25 | 40–50 | 60–80 | 30–40 |
| Heat Deflection Temp (°C) | 110–140 | 180–220 | 125–135 | 150–200 |
| Water Absorption (%) | 0.2–0.3 | 1.2–1.5 | 0.15–0.18 | 0.08–0.10 |
| Friction Coefficient | 0.1–0.3 | 0.2–0.4 | 0.3–0.4 | 0.2–0.3 |
POM excels in low friction, wear resistance, and dimensional precision, making it ideal for moving or precision parts where stability is critical.
7. Sustainability and Market Outlook of POM Plastic
The POM industry is increasingly adopting sustainable practices. Manufacturers are optimizing energy use and polymerization efficiency, while chemical recycling methods are gaining attention. Depolymerization allows POM waste to be converted back into monomers for reuse, supporting a circular economy.
Major POM products in the market include:
- DuPont Delrin®. This homopolymer is known for its high mechanical strength and finds extensive applications in automotive components and consumer goods.
- Celanese Celcon®. It is a copolymer with excellent thermal stability, commonly used in electronics and machinery parts.
- Polyplastics Duracon®. Duracon offers balanced performance, making it suitable for both automotive and medical applications.
- Mitsubishi Iupital®. This weather-resistant copolymer is widely applied in electronics and machinery that require durability under environmental stress.
- BASF Ultraform®. Ultraform is a low-warpage copolymer, often used in automotive and consumer products where dimensional stability is critical.
Ongoing advances in recycling technologies and sustainable production are helping the POM industry maintain high performance while reducing environmental impact.
Conclusión
POM plastic is one of the most versatile and reliable engineering materials available today. Its combination of metal-like strength, self-lubrication, and excellent machinability allows it to support innovation across automotive, electronics, medical, and consumer product industries. As technology advances and sustainability becomes increasingly important, POM will continue to play a central role in modern manufacturing.
Looking for a manufacturing solution to bring POM-based projects to life? Consulting a capable and trustworthy CNC machining or plastic injection molding partner like the Beska team is essential to ensure precision, material integrity, and reliable performance.
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Preguntas frecuentes
No. POM is safe under normal conditions and complies with food-contact standards. It only releases formaldehyde when overheated or burned.
Because it combines high strength, rigidity, and wear resistance with low weight and self-lubrication—allowing it to replace metal in many designs.
POM offers better dimensional stability and lower friction; Nylon has higher toughness and heat resistance. Selection depends on the application.
Yes, though more complex than common plastics. Both mechanical and chemical recycling methods are used to recover material.
Cracking often results from internal stress, poor design, or improper molding parameters. Balanced wall thickness and proper cooling help prevent it.
Standard grades have limited UV resistance. For outdoor use, choose UV-stabilized or coated grades.
Generally higher than PP or PE but lower than high-performance plastics. The average market price ranges from USD 2.5 to 5.0 per kg depending on grade.
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