Dupont Delrin rod and Acetal Rods

Many of our clients assume that Delrin rod and Acetal rod is the same thing. This is not quite true. Yes, all Delrin rod is Acetal rod, but not all Acetal rod is Delrin rod. Delrin is a trade name for Homo-Polymer Acetal made by Dupont. This is the most recognized of all Acetal materials, but far from the only available Acetal material.Black and Natural Acetal - Delrin Rod
The Co-Polymer Acetal 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, or Hostaform M25. While Delrin is a wonderful material, in larger cross sections or larger diameters, the Delrin brand Homo-Polymer can exhibit center line porosity. 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 centers’ of Delrin Rod and Delrin Sheet.

This should not stop you from considering Delrin though. Many other properties of the Delrin resin are superior to the Co-Polymer resins. These properties are:

General Property ASTM
Typical Value
Unfilled Delrin®

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

The key properties that Delrin 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. Delrin brand material also comes in several resin variations, including: Delrin 150 and Delrin 507, contact us for details.

Many of our clients prefer the Delrin brand 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.Colored Acetal - Delrin Rod - Pomalux

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 – Delrin Rod, and sometimes referred to as plastic dowel. We also have the capacity to supply colored Acetal – Delrin rod; click here from more details on the colored Acetal material.

Similar materials to Acetal – Delrin 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


Delrin Homopolymer versus Copolymer Acetal

Have you noticed the little plastic gears in your watch, the working parts in a garden hose nozzle, audio and video cassette moving parts, food slide components, timing screws and pumps parts, or perhaps even acoustic guitar picks? If you have, then you have seen perhaps the most versatile plastic known as Acetal (polyoxymethylene or POM). It is an extremely durable and strong plastic material, so it is no surprise to see it being used for so many different things. Used as a regular replacement for many aluminum or metal parts, or the similar plastic materials, like Polyamide Nylon or Rigid Polyester. It is the next step up from HDPE, a common plastic used in food processing. Because of the uniform molecular structure of Acetal, it can be used for different applications that might require a plastic material to be more rigid, have good mechanical properties and have a low coefficient of friction.Machining Copolymer Acetal or Delrin Homopolymer Acetal Rod

The battle between Delrin and Acetal

Both Delrin and Acetal materials are thermoplastic. What this means a material can be softened by being heated and when cooled becomes hard again, and will retain the new shape. Because of this characteristic it is able to be molded in to many different types of objects, like the few listed above. While some thermoplastics are ‘formable’, Acetal is definitely not to reshape with heat after it is made into a sheet or rod. A crystalline, rather than amorphous type resin is used to make acetal. Because of the uniform molecular structure of Acetal, it can be used for different applications that would require a plastic material to be more rigid, have excellent mechanical properties and have a low coefficient of friction. Both of these resins are produced in Natural (White) and Black, also there are some colors are available on special order; there is also the Delrin AF (a PTFE filled Delrin) is a mid to dark brown color.

There are two basic grades of Acetal

You need to know some of the differences, Acetal versus Delrin. There are two main types of Acetal; one is a copolymer and the other a homopolymer. Ticona is one manufacture that makes a widely known copolymer called Celcon, BASF produces a high quality copolymer, H2320. Likewise DuPont makes Delrin, a popular brand name and the most commonly used Homopolymer. Standard mill shapes include: Acetal Sheet, round rods, flat sheets and some tube and profiles are also produced.
They may be close, but not the exactly

Yes, the copolymer and homopolymer acetal are very similar and they look the same, they do have some large differences in properties and this makes them unique in their own way. For example the copolymer will perform better than the homopolymer in these areas; thermal, impact, wear and chemical resistance. As you investigate the copolymer characteristics, you will discover that it has a lower water absorption rate. You may find this to be important if you plan on using with moist functions such as faucets, impellers, pump parts, valve and valves stems than the homopolymer acetal will. Now, when you review the homopolymer, which has a higher crystallinity, this will increase some properties and make it stronger, with improved mechanical strength and creep resistance, than its brother, the copolymer. Chemical resistance is one of the areas Acetal materials sometimes have a weakness, specifically oxidizing agents and strong acids. Other than these types of chemicals, Acetal is pretty much resistant to a wide range of solvents and commonly used chemicals.

Delrin Versus Acetal

One visual difference, and possibly a significant performance difference, between the copolymer and homopolymer is center line porosity. The homopolymer (Delrin) resin is known to be susceptible to having center line porosity, a section in the center of a rodt, it will be seen as a small circle found at the center. As for slab or sheet, it will appear as a white stripe down the center or middle (of the thickness) of the extruded or compression molded sheet material. This porosity is caused by the gasses trying to escape during the cooling processes. If a large rod is to have the middle or center machined out, then Delrin is an excellent choice. Copolymer Acetal does not have this ‘soft center’ or porosity.
Homopolymer Delrin and Copolymer Acetal are easy to machine

Both of these resins can be excellent choices for machining and mechanical type applications. Tight tolerances may be maintained during the cutting and machining process. The materials are considered to be self lubricating, and make very good dry slide wear strips. Both of these resins are FDA and 3A (Dairy) compliant.

You may wish to consider Acetal, either Delrin Homopolymer or Copolymer Acetal for your next engineering plastic applications. Contact us via Email for additional assistance, or call us at 866-832-9315

Topic: Delrin Versus Acetal in Sheet and Rod

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