High-Performance Acetal Fasteners: Screws, Nuts, Rods & Custom Parts

Polyoxymethylene (Acetal)

Acetal, also known as polyoxymethylene (POM), is a premier engineering thermoplastic prized for its exceptional stiffness, low friction, and dimensional stability. From –40 °C to 80 °C, POM delivers high strength, hardness, and rigidity. Naturally an opaque white, it can be dyed to virtually any color, making it versatile for both functional and aesthetic applications. The material is available as a homopolymer or a copolymer, and is sold under well‑known trade names such as Delrin® by DuPont and Celcon® by Celanese.

Acetal Copolymer vs. Acetal Homopolymer

Both POM variants share many characteristics, yet their molecular structures differ: the homopolymer consists of a single monomer repeat unit, while the copolymer incorporates two distinct monomers. For most applications either grade performs adequately, with properties typically within 10 % of each other. However, specific performance differences can influence material selection.

Key Characteristics of POM (Acetal)

• Creep‑resistant and mechanically stable
• Excellent electrical insulation and dielectric properties
• Strong, rigid, and tough
• Outstanding moisture resistance with low water absorption
• Low coefficient of friction and high lubricity
• Broad chemical resistance—mostly unaffected by solvents and fuels
• Low thermal expansion and high stiffness, offering a metal‑alternative option
• FDA‑approved for food‑contact applications
• Easily machined, molded, and colorable

Limitations

• Not paintable
• Flammable and heat‑sensitive
• High lubricity can impede adhesion to other materials
• Poor performance in chlorinated environments; unsuitable for swimming‑pool use

Acetal Copolymer

The semi‑crystalline copolymer offers reduced centerline porosity and superior chemical properties. It remains stable across a pH range of 4–9, resists hydrolysis up to 60 °C, and tolerates continuous service temperatures up to 90 °C in air. Available in natural and black grades, the copolymer typically costs slightly less than the homopolymer.

Acetal Homopolymer

As a fully crystalline thermoplastic, the homopolymer is an ideal metal substitute, albeit with centerline porosity. It outperforms the copolymer in mechanical metrics:

• 15 % higher stiffness and strength
• 10 % better creep resistance
• Higher Rockwell hardness rating
• Natural grade meets FDA, NSF, and USDA standards
• Greater tensile strength and impact resistance

Why Choose Delrin® (Acetal Homopolymer) to Replace Metals?

Delrin® combines high tensile strength, low friction, and superior wear resistance. Its low creep, resistance to warping, and overall toughness make it a durable alternative in demanding environments. While it does not match the ultimate strength of metals, it excels in applications such as pump and valve components exposed to moisture, where metal parts may fail.

Applications

POM is engineered for high‑performance parts: gears, safety restraints, bearings, bushings, rollers, fittings, and electrical insulators. It’s also a popular material for fasteners—screws, hex nuts, washers, and bolts—alongside consumer goods like eyeglass frames, ski bindings, gun and knife handles. The automotive sector favors Delrin® for interior components due to its impact strength, while the electronics industry utilizes it for precision assemblies.

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