POM (Polyoxymethylene / Acetal): Applications, Advantages & Injection Molding Guide

POM, also known as acetal, is a high-performance engineering thermoplastic known for its excellent dimensional stability, high strength, low friction, and resistance to wear and moisture. It is widely used in precision parts for mechanical and automotive components.

What Is POM?
Polyoxymethylene is a semi-crystalline polymer available in two main types: homopolymer (POM-H) and copolymer (POM-C). Homopolymer POM has better tensile strength and stiffness, while copolymer POM provides improved chemical resistance and thermal stability. POM is characterized by its smooth surface finish, machinability, and resistance to fatigue.

Key Applications of POM
Automotive Industry
– Gears, bushings, and pulleys
– Fuel system components
– Window regulators and seatbelt parts

Industrial Equipment
– Conveyor belt links and valve components
– Bearings, cams, and snap fits
– Pump housings and precision levers

Consumer Products
– Zippers and fasteners
– Electric toothbrush gears and knobs
– Furniture fittings and door handles

Electrical & Electronics
– Switch housings and circuit board holders
– Connectors and terminal blocks
– Insulating parts and housings

Medical & Food Equipment
– Drug delivery devices (non-implantable)
– Food-grade dispensers and seals
– Sterilizable components for lab equipment

Advantages of POM
– Low coefficient of friction and excellent wear resistance
– High tensile strength and stiffness
– Excellent dimensional stability
– Low moisture absorption
– Good fatigue and impact resistance
– Chemical resistance to fuels, oils, and solvents
– Smooth surface finish and machinability

Injection Molding Guidelines for POM

1. Drying Requirements
POM generally does not require drying if stored in sealed containers. Drying may be necessary after extended exposure to humidity.
– Drying temperature: 80–100 °C (if needed)
– Drying time: 1–2 hours

2. Melt and Mold Temperatures
– Melt temperature: 190–230 °C for homopolymer; 190–210 °C for copolymer
– Mold temperature: 80–105 °C
– Higher mold temperatures improve part strength and reduce post-mold shrinkage

3. Injection Pressure & Speed
– Pressure: 700–1200 bar depending on wall thickness
– Speed: Medium to high injection speed recommended for better flow and surface finish

4. Runner and Gate Design
– Suitable for all gate types (fan, edge, tunnel)
– Avoid sharp corners and ensure proper venting to prevent burn marks
– Hot runners can be used but may increase risk of degradation (especially for homopolymer)

Common Molding Issues
– Warping: Use consistent mold temperature and balanced cooling
– Brittleness: Avoid excessive shear or thermal degradation
– Burn marks: Improve venting and reduce injection speed
– Shrinkage: Typical shrinkage 2–3.5%, affected by crystallinity and filler type

Final Thoughts
POM is a top-tier choice for precision parts that require strength, wear resistance, and dimensional accuracy. Its performance in lubricated and high-load environments makes it indispensable in automotive, industrial, and consumer applications.
Need support selecting between homopolymer and copolymer grades of POM or optimizing your tool design? Our materials experts are here to help.