Delrin® Homopolymer Acetal compared with Acetal Copolymer

Many of our clients assume that Delrin® rod and Acetal rod are the same thing. This is not true.

Yes, all Dupont Delrin® rod is Homopolymer Acetal rod, but not all Acetal rod is Delrin® rod. Dupont is the maker of Dupont Delrin® resins

Delrin® is the trade name for Homopolymer Acetal made by Dupont. Dupont™ Delrin ® is a popular acetal homopolymer brand name and the most commonly used acetal homopolymer.

This is the most recognized of all trade names for Acetal materials, but not the only available Acetal material.
The Copolymer Acetal resin is produced by a wide variety of large plastic manufacturers, BASF is probably one of the largest and most well known. Some main resin names are: BASF Ultraform® H4320, Kepital® F10-02, Hostaform® M25 and many others.

While Delrin® Homopolymer Acetal is a wonderful material, in a larger cross sections Homopolymer can exhibit center line porosity, or ‘soft centers’. This can sometimes be seen with the naked eye, and is a darker white in a normally milky white natural colored material. This center line porosity can cause problems in some applications. This porosity can cause leakage of fluid if under pressure, or soft center’s of homopolymer rod and sheet.

This should not stop you from considering Delrin® Homopolymer Acetal though. Many other properties of the homopolymer resins are superior to the copolymer resins. These properties are:

General Property ASTM
Typical Value

Typical Value
Unfilled Co-Polymer
Specific Gravity D792 1.42 1.40
Tensile Strength Yield D638 9,600 – 11,000 9,000 – 10,200
Tensile Modulus D638 450,000 400,000
Izod Impact – Notched D256 1.2 1.0
Hardness – Rockwell D785 M94 M90
Deflection Temp @ 264psi D648 257 220
Deflection Temp @ 66 psi D648 347 335
Water Absorption @ 24 hrs
% 0.24 0.25
Co. Thermal Expansion D696 6.83X10-5 5.4X10-5

Some key properties for homopolymer acetal are: higher tensile strength, increased Izod impact, higher deflection temperatures and it is slightly harder. The co-efficient of thermal expansion is a bit higher, and needs to be considered when designing a new part. Extruded Delrin® brand homopolymer resin material also comes in several resin variations, including: Delrin® 150 and Delrin® 507, contact us for details. Dupont™ Delrin® is a popular acetal homopolymer brand name and the most commonly used acetal homopolymer.

Many of our clients prefer the homopolymer rod and sheet for small machined parts. This is due to the increase in a few key properties, and of course brand recognition.

Both resins meet the standard ASTM-D-6778, and the cancelled specs, L-P-395 and ASTM-D-4181.Comparing Dupont Delrin to Acetal Copolymer

The Acetal family of plastic resins are excellent for wear resistance, great mechanical strength, and superior machining properties. It is available in a huge range of sizes and shapes. Click here for more details on Acetal – Homopolymer Aceteal Rod, and sometimes referred to as plastic dowel. We also have the capacity to supply colored Acetal Copolymer or Delrin® Homopolymer Acetal rod; click here from more details on the colored Acetal material.

Similar materials to Acetal Copolymer – Homopolymer Acetal are Nylon Rod, PET Rod and Noryl® Rod. Most materials are available as round rod, square rod, bar, strip, sheet and plate.

Please contact us for more details on these and other plastic materials. For a comparison chart of plastic materials click here: Plastic Materials Selection Guide 

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


What is the difference between Delrin® and Teflon®?

Dupont Delrin® is a premium Homopolymer Acetal or polyoxymethylene (POM-H) and it is a semi-crystalline, non-amorphous type of thermoplastic. Delrin®, which is the DuPont brand name for Acetal, is a homopolymer. It comes in both black and white. One important difference between Acetal Copolymer and the homopolymer Delrin resin is that Acetal tends to have centerline porosity. Teflon® is also a tradename for the original PTFE resin produced and invented by Dupont, and once processed into a shape it can only be called PTFE.

What kind of material is Delrin® Homopolymer?

Acetal Homopolymer (POM-H) or Dupont Delrin® is a semi-crystalline plastic which offers an excellent balance of physical properties that bridge the gap between metals and plastics. The Dupont Delrin® possesses high tensile strength, excellent creep resistance and toughness. It also exhibits low moisture absorption while providing an excellent wear resistance.

Are Delrin® Homopolymer Acetal and UHMW the same?

Dupont Delrin® is the common name for homopolymer acetal (POM-H). UHWM is a member of the Polyolefin family, and much different that Delrin®. The Dupont Delrin® has slightly better mechanical properties than copolymer acetal, but often can have a low density center, especially in large cross-sections. Dupont Delrin®, like all Acetal materials, is easy to machine and has very low moisture absorption, and provides an excellent machined surface finish.

Are Dupont Delrin® Rod and Acetal Rod the same thing?

No, they are not the same. The Dupont Delrin® homopolymer acetal or POM-H offers slightly higher mechanical properties than acetal copolymer, but may contain a soft or low density center (also known as 'center line porosity'), this is especially true in large cross-sections of Dupont Delrin. In addition, Dupont Delrin® also is slightly less chemical resistance than the copolymer acetal alson known as POM-C.

Which is better, Dupont Delrin® 150SA Homopolymer or Acetal Copolymer?

Acetal is the common name for a family of thermoplastics with the chemical name 'PolyOxyMethylene', or POM. Acetal is available in two general types of resins: Copolymer Acetal (POM-C), and Homopolymer Acetal (POM-H) commonly called Dupont Delrin®. Each type of acetal has its own set of advantages and disadvantages. Which one is better? It depends on the physical properties you are looking for.