When a project demands the precision of a Swiss watch and the durability of an engine gear, POM (Polyoxymethylene)—often called Acetal—is the undisputed champion. In the manufacturing world, it is known as “Plastic Steel” because it bridges the gap between common plastics and die-cast metals.
POM is a highly crystalline plastic, which gives it two incredible traits: extreme rigidity and a naturally slippery surface. It has the lowest friction of almost any engineering plastic, making it the go-to for parts that need to slide, rotate, or click.
| Property | Typical Value | Unit | Why it Matters |
| Tensile Strength | 60 – 70 | MPa | Metal-like rigidity and strength |
| Flexural Modulus | 2,500 – 3,000 | MPa | Resists “creep” (deformation) under load |
| Coeff. of Friction | 0.20 – 0.25 | – | Self-lubricating; smooth movement |
| Water Absorption | 0.20 – 0.25 | % | Excellent stability in wet environments |
| Molding Shrinkage | 1.8 – 2.2 | % | High shrinkage requires expert mold design |
Unlike Nylon, which absorbs water and changes size, POM stays exactly the size you molded it. This dimensional stability is why it’s used for fuel system components, zippers, gear wheels, and precision medical injectors.
If you’ve ever felt a “satisfying” click from a plastic buckle or a button, that’s often POM. It has a high “spring-back” effect, meaning it can be flexed and will return to its original shape perfectly, time after time.
A Note for Designers: POM is sensitive to high heat during the molding process; if left in the barrel too long at extreme temperatures, it can release formaldehyde gas. Because of its high crystallinity, it also has a high shrinkage rate. Partnering with a molder who understands POM’s thermal limits is key to avoiding internal “voids” or bubbles in thick-walled parts.
Are you designing a gear system or a high-tension clip? I can help you decide between POM-H (stronger) or POM-C (better chemical resistance) to ensure your mechanical assembly runs smoothly.
Contact us to evaluate manufacturability, tolerances, and cost for your specific application.
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