What is POM? A Technical Introduction to Polyoxymethylene
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What is POM? A Technical Introduction to Polyoxymethylene
Polyoxymethylene (POM), also referred to as acetal or polyacetal, is a high-performance engineering thermoplastic known for its superior dimensional precision, excellent mechanical strength, and low friction properties. Due to its exceptional balance of machinability and mechanical reliability, POM is widely used in industries such as automotive, consumer electronics, and industrial automation.
Chemical Structure and Polymer Variants
POM is a polymer derived from formaldehyde, which gives it the alternate name polyformaldehyde. It exists in two main commercial forms: homopolymer and copolymer.
- POM Homopolymer: is synthesized by polymerizing pure formaldehyde and is known for its higher mechanical strength and rigidity.
- POM Copolymer: is modified by introducing small amounts of comonomers, improving its thermal and hydrolytic stability.
Both versions share similar base characteristics, but their slight differences allow engineers to select the right grade depending on processing requirements and part performance criteria.
Key Mechanical and Dimensional Properties
POM is recognized for its high tensile strength, impact resistance, and dimensional stability under mechanical stress. Its stiffness and low friction coefficient make it ideal for manufacturing components like precision gears, bushings, and conveyor rollers. Some important physical properties include:
- Tensile strength of 60 to 70 MPa
- High hardness and rigidity
- Consistent performance across a broad temperature range (typically -40°C to 100°C)
Its low moisture absorption and low thermal expansion coefficient contribute to its reliability in applications where long-term dimensional accuracy is critical.
Processing, Fabrication and Common Applications
POM is compatible with multiple processing techniques, including injection molding, extrusion, and CNC machining. It machines cleanly and maintains tight tolerances, making it an excellent material for precision components.
During processing, special attention must be given to thermal stability, as POM can decompose to release formaldehyde gas if overheated. Although it typically does not require drying before molding, proper storage is necessary to prevent moisture uptake in humid environments. Processing parameters like melt and mold temperature must be well-controlled for optimal performance and stability.
Due to its high mechanical integrity and ease of fabrication, POM is widely used in:
- Automotive parts (gears, gaskets, seat belt buckles)
- Consumer electronics (printer gears, zippers)
- Industrial machinery (valves, sliders, fasteners, roller wheels)
Its ability to maintain shape and performance under load makes it a favorite among design engineers seeking a durable, self-lubricating material.
Summary
Polyoxymethylene (POM), also known as acetal, is a high-performance engineering thermoplastic prized for its dimensional precision, mechanical strength, and low friction. Available as homopolymer and copolymer variants, POM offers a balance of rigidity and thermal stability suited to various applications. It exhibits high tensile strength, impact resistance, and stable performance across temperatures from -40°C to 100°C. With low moisture absorption and thermal expansion, it ensures long-term dimensional accuracy.
POM is compatible with injection molding, extrusion, and CNC machining, making it ideal for precision parts in automotive, consumer electronics, and industrial machinery, where durability and self-lubrication are essential.
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