Acetal Copolymer vs Dupont Delrin® Homopolymer: Properties and Benefits of Each
Industrial Plastic Supply, Inc. has been supplying a vast inventory of plastics to a wide customer base since 1975. Today, we put the spotlight on two products that are incredibly similar, but have key differences that result in each performing optimally in certain applications: the Acetal Copolymer and the Delrin® Homopolymer.
Both of these acetal materials are incredibly similar, with similar beneficial properties. They are both compliant with FDA, ITAR, and RoHS standards. Both are very stiff plastics with excellent dimensional stability in average environments. They are self-lubricating, easy to cut with standard tools, and abrasion and wear resistant. The major differences between them however are a result of their differing structures.
What Is Polyoxymethylene
Polyoxymethylene (also known as POM for short) is an important and commonly used engineering plastic material. There are two distinct types of POM; the first is Homopolymer Acetal and is commonly called Dupont Delrin®. The other is Copolymer Acetal and is referred to by the trade names Celcon®, Sustarin® C, Tecaform®, Ultraform®, Kepital® and many others. Both versions of POM are very popular thermoplastic materials. They both are commonly used for parts that need to be stiff, dimensionally stable and have low surface friction.
Delrin® Homopolymer
The homopolymer possesses much more regularity in its structure, with a repeated, crystalline pattern throughout the plastic. As a result of its strong, crystalline makeup, the Delrin® Homopolymer has superior physical properties, such as better fatigue and creep resistance, and bearing properties. Also, it has better short-term heat resistance compared to the acetal copolymer, with a much higher melting point.
However, this homopolymer does experience minor and inherent center-line porosity. This is basically a band area of tiny porous holes along the center of a rod or sheet. Depending on the severity of the porosity, these holes could weaken a finished part or cause other problems with its performance.
Acetal Copolymer
We’ve found that our customers tend to gravitate towards the acetal copolymer when they require a wider processing window, lower costs, and better long-term resistance to heat and alkaline environments. The acetal copolymer is not as crystalline in its structure, which causes it to not only have a generally lower melting point, but when incorporated with other materials, also increases the tolerance for high melting temperatures.
The less crystalline structure of the copolymer means that this plastic isn’t quite as strong. However, its mixed molecular structure has several benefits. The acetal copolymer has improved resistance to oxidation, improved chemical resistance, and much better long-term resistance to heat. That difference in chemical resistance is much more pronounced with exposure to hot water, especially chlorinated water. The acetal copolymer survives much longer than the homopolymer in these conditions.
Final Thoughts
Both the Acetal Copolymer and the Delrin® Homopolymer have their benefits. Depending on your application and requirements, you can choose the best acetal based plastic for your needs. In need of a supplier of plastics and plastic materials? Check out the rest of Industrial Plastic Supply today!
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.
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 Test
Typical Value Unfilled Homo-Polymer
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. Some of our major brand names for quality Copolymer Acetal (POM-C) sheet and Rod include: Tecaform AH®, Sustarin C®, ZL 900® and Pomalux®.
Both resins meet the standard ASTM-D-6778, and the cancelled specs, L-P-395 and ASTM-D-4181. Contact us for certification and specifications you may require.
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 Acetal 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
Is colored Acetal Copolymer – Delrin® Homopolymer Rod Readily Available?
We get this question frequently.
The easy answer is yes, however, the most common available colors are Black and Natural (white in color). But to continue the thought, we have several manufacturers that run ‘Medical’ grades of Acetal Copolymer as well as Acetal Homopolymer (ie: Dupont Delrin® 150SA Homopolymer Acetal) in several colors. These materials are special run, but can frequently purchase by the standard length without a custom run. The biggest factor may be the price. The colored version of Acetal Copolymer – Delrin Homopolymer Acetal materials are dramatically more expensive.
Colored Acetal Copolymer – Dupont Delrin® Homopolymer 150SA Rod
While price is a factor, the benefits may out weigh the cost. Many of our clients use these colored rods to help differentiate their product from their competition. With colors that can come close to a logo color or match a machine, these advantages are clearly visible. Having a special color available to machine small to medium runs of your product can save you thousands over molding a new part for trials.
What colors can I get in Acetal Copolymer or Dupont Delrin® 150SA Homopolymer Acetal Rod?The range is a bit limited, but does include: brown, dark blue, dark green, gray, light blue, light green, red, rust and yellow (and of course Natural and Black). For details on the properties of these materials click here: Acetal Copolymer and Dupont Delrin® 150SA Homopolymer Acetal.Dupont™ Delrin® is a popular acetal homopolymer brand name and the most commonly used acetal homopolymer.
For specifics on your requirement, please contact us for availability and pricing. Email or call 866-832-9315
We can supply both the Acetal Copolymer and the premium Dupont Delrin 150SA Homopolymer acetal from our premium suppliers: Ensinger Plastics, Z/L Plastics, Rochling Engineered Plastics and others in special formulations.
