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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 Copolymer and Homopolymer Acetal, such as Dupont Delrin®, are distinct versions of Acetal resin, with Delrin® being a premium homopolymer known for generally superior physical properties. For instance, Homopolymer Acetal has a higher Tensile Modulus of Elasticity (450,000) and a higher Heat Deflection Temp @ 264 psi (257 degrees F) compared to Copolymer Acetal (400,000 and 220 degrees F, respectively). A notable difference is that homopolymer grades can exhibit center-line porosity from manufacturing outgassing, a problem less common in copolymer resin. Both materials are tough, machinable, and meet specifications like ASTM-D-4181.

Comparing Dupont Delrin to Copolymer Acetal

Are Acetal Copolymer and Homopolymer Acetal the same?

This is one of our most common questions, and it is a bit involved of an answer.

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.

What are the properties of Homopolymer and Copolymer Acetal?

Homopolymer Acetal and Copolymer Acetal exhibit distinct properties, as detailed in the chart below. Key properties include Tensile Modulus of Elasticity (Homopolymer: 450,000, Copolymer: 400,000), Flexural Modulus of Elasticity (Homopolymer: 470,000, Copolymer: 366,000), Heat Deflection Temp @ 264 psi (Homopolymer: 257°F, Copolymer: 220°F), Melting Point (Homopolymer: 347°F, Copolymer: 335°F), Coef. of Linear Thermal Expansion (Homopolymer: 6.8 x 10-5, Copolymer: 5.4 x 10-5), and Water Absorption @ Saturation (Homopolymer: 0.90, Copolymer: 0.80). These materials are available as both Acetal Copolymer or Acetal Homopolymer in Rod, Block, Sheet and Slabs, commonly in Natural (White) or Black, with other colors available for minimum orders. While properties are similar, one material may be better suited depending on your application. For additional information on product availability and data sheets, review our Delrin® Homopolymer and Acetal Copolymer page. We supply premium Delrin® Homopolymer product, also known by various names like Delron, Delran, Delrun, and Derlin. Contact us today at 866-832-9315 or Email Us for more details on Acetal Copolymer, premium Delrin® Homopolymer Acetal, or any other plastic material. Note: Delrin® is a registered Trademark of Dupont.

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 Homopolymer Acetal (Delrin®) and Copolymer Acetal?

Homopolymer Acetal, like Dupont™ Delrin®, generally exhibits higher physical properties than Copolymer Acetal. However, Copolymer Acetal is less prone to centerline porosity, a potential issue in some homopolymer extrusions. Both types are known for their toughness and machinability.

2 What is centerline porosity and how does it affect Acetal plastics?

Centerline porosity is a manufacturing issue caused by outgassing, which can appear at the center or surface of homopolymer extrusions. This porosity can lead to problems during machining or allow moisture permeation through the material. Copolymer Acetal resins typically have little to no porosity issues.

3 Is all Acetal plastic considered Delrin®?

No, "Acetal" is a generic term that encompasses both homopolymer and copolymer resins. Delrin® is a specific brand name for a premium homopolymer Acetal produced by Dupont. It's important to distinguish between them for specific applications.

4 How do the physical properties of Homopolymer and Copolymer Acetal compare?

While both are tough and machinable, Homopolymer Acetal generally has a higher tensile modulus of elasticity and flexural modulus compared to Copolymer Acetal. The page provides a chart detailing these and other specific property differences to aid in material selection for your project.