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Acetal Copolymer vs. Delrin® Homopolymer Acetal: Key Differences

Feb 25, 2013 | Choosing A Plastic Material, Educational Post, Material Comparison, Mentor Nuggets | 5 comments

Quick Answer

Acetal is a generic term encompassing two main versions: homopolymer acetal, famously known as DuPont Delrin, and copolymer acetal. While both are tough and machinable, Delrin (homopolymer) typically exhibits superior physical properties, such as a higher Heat Deflection Temperature of 257 degrees F at 264 psi compared to 220 degrees F for copolymer acetal. A key distinction is that homopolymer acetal can have centerline porosity due to outgassing during manufacturing, whereas copolymer acetal generally has little to no porosity issues.

Comparing Dupont Delrin to Copolymer Acetal

Are Acetal Copolymer and Homopolymer Acetal the same?

No, Acetal Copolymer and Homopolymer Acetal are not the same; they are two distinct versions of acetal resin with different properties and applications. While both are tough and machinable, homopolymer acetal (like DuPont Delrin) generally offers superior physical properties, whereas copolymer acetal provides better chemical resistance and dimensional stability. The answer is a bit involved, as detailed further in this article.

There are two main versions of Acetal Resin

Homopolymer Acetal and Copolymer Acetal

The most popular name for a Homopolymer Acetal is the Dupont Delrin, which is a premium Homopolymer Acetal.

The second Acetal is a Copolymer acetal, and there are many suppliers of this resin. 

Acetal is the generic, and not all Acetal is Delrin® Hompolymer, nor is it Acetal Copolymer. A distinction is required to determine which is best for your application. There are several manufacturers that produce Acetal Copolymer resin, including: Celanese®, BASF®, Ticona®, SABIC® and many more.

Acetal Copolymer compared to Delrin® Homopolymer Acetal

Delrin® is a premium homopolymer Acetal produced by Dupont. Many of the physical properties of the homopolymer exceed that of the copolymer Acetal. Dupont™ Delrin® is a popular acetal homopolymer brand name and the most commonly used acetal homopolymer.Comparing structure of Homopolymer and Copolymer Acetal

The generic term ‘Acetal’ covers both the homopolymer from Dupont and the copolymer grades of resin. Both materials meet the ASTM-D-4181, ASTM-D-6100 or ASTM-D-6778 specification (an old call out is L-P-392). Homopolymer Acetal is POM111, and Copolymer Acetal is POM211.

Both are very tough and machinable, and have some similar properties.

An additional difference is the inherit problem of center-line porosity in some of the homopolymer grades. This is caused by out gassing during manufacturing, and can be found at the center or on the surface of all homo-polymer extrusions. This porosity can cause some problems with machining or moisture permeation through the material. The copolymer resin has little to no porosity issue.

Some of the other differences are in the physical properties of the resin. Review the chart for some of the most popular properties people ask for when looking at Acetal Copolymer or Homopolymer Acetal.

See Homopolymer and Copolymer Acetal properties chart below.

Properties Homopolymer Acetal Copolymer Acetal
Tensile Modulus of Elasticity 450,000 400,000
Flexural Modulus of Elasticity 470,000 366,000
Heat Deflection Temp @ 264 psi – degrees F 257 220
Melting Point – degrees F 347 335
Coef. of Linear Thermal Expansion 6.8 x 10-5 5.4 x 10-5
Water Absorption @ Saturation 0.90 0.80

Material is available as both Acetal Copolymer or Acetal Homopolymer in Rod, Block, Sheet and Slabs.

Acetal is one of the most widely available plastics, especially on the West Coast (for some reason the East Coast seems to like the Nylon – Polyamide material more). Most commonly available in Natural (White) or Black, but can be produced in a wide range of colors with minimum orders. This enables material matching your product color or for easy identification of parts.

While these properties are similar, depending on your application, one material may be better suited than the other. Review our Delrin® Homopolymer and Acetal Copolymer page for additional information on the product availability and data sheets. We get calls for the premium Delrin® Homopolymer product, but some people may call it Delron, Delran, Delrun, Derlin and many other names, but it is still premium Delrin® Homopolymer Acetal to us.

Looking for other colors of Acetal Copolymer or Acetal Homopolymer Rod?

Contact us today for more information on Acetal Copolymer or premium Delrin® Homopolymer Acetal or any other plastic material.

Call us at 866-832-9315 or Email Us for more additional details

**Note:  Delrin® is a registered Trademark of Dupont

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Frequently Asked Questions

1 What is the primary difference between Acetal copolymer and homopolymer?

Acetal homopolymer, often known by the brand name Delrin, typically offers higher strength, stiffness, and hardness. Acetal copolymer, on the other hand, provides better chemical resistance, lower moisture absorption, and improved dimensional stability, making it suitable for different application requirements.

2 What are the key properties of Acetal resin that make it suitable for industrial use?

Acetal resin is valued for its high strength, stiffness, and hardness, combined with excellent dimensional stability and a low coefficient of friction. It also offers good chemical resistance and creep resistance, making it ideal for precision parts in demanding industrial environments.

3 What specific characteristics does Delrin homopolymer acetal offer?

Delrin, a type of homopolymer acetal, is renowned for its superior tensile strength, rigidity, and fatigue endurance. It exhibits excellent wear resistance and a low friction coefficient, making it a top choice for high-performance mechanical components requiring long-term reliability.

4 When should I choose Acetal copolymer over homopolymer for my application?

You should consider Acetal copolymer when your application requires enhanced chemical resistance, particularly against strong bases, or when operating in environments with high humidity where lower moisture absorption and better dimensional stability are critical. Homopolymer is generally preferred for maximum mechanical strength and hardness.