Is HDPE Sheet and Acetal Sheet (Delrin) the same?

Here is another popular question asked by our clients. Is HDPE the same as Acetal / Delrin?
No, they are two totally different materials. Although the natural color of both is a milky white to opaque white, and they do look a bit similar, they are not. (HDPE is milky white to almost translucent depending on thickness, and Acetal is a more opaque white to slightly milky – once again depending on thickness . See picture below of .500″ thick samples of HDPE and Acetal sheets)

HDPE and Acetal – Some DifferencesHDPE sheet and Acetal sheet Natural Color Samples Both .500" thick sheet

The HDPE sheet and rod is a softer material, and is commonly known for its FDA certification and used in numerous food applications, such as: one gallon milk jugs, cutting boards, colored water glasses/cups, and many, many more. While it can be machined, because it is a bit softer and lighter, the tolerances it can be machined to are not very tight. It is not bondable, so it makes a great non-stick surface for sticky foods and adhesives.


The Acetal / Delrin also have FDA certification, and are used heavily in the food processing industry. This material is a more mechanical material and is used in bearing and wear applications, cams, feeder screws, etc. This material is can be machined to tight tolerances, and will wear for long periods without lubrication. Due to its exceptional wear properties, it is not bondable, thus requiring mechanical fastening or threads to assemble. It has a very low water absorption, and you will find it in your toilet tank as the white moving parts in the filler mechanism. It is an extremely popular material for machinists, as it works much like soft brass.


While HDPE Sheet and Acetal Sheet look similar, they perform quite a bit differently.

While both materials are FDA approved, are machinable and can be used to make rigid wear resistant parts, they are two different resins and have drastically different physical properties. Another major difference is in the weight of these items, HDPE sheet and rod material weighs about 35% less than the Acetal sheet and rod material. Please check the data sheets for more information to assist in proper material selection. Acetal Data Sheet and HDPE Sheet Data

Acetal is commonly known as: Delrin, Ensital, Unital, Pomalux, Ultraform and many more.

HDPE is also known as: Ultraethylux, Densetec, Polystone G, Fortiflex, Versadur, Hostalen, and many more.

Contact us for more details on the HDPE and Acetal families of plastic materials, e-mail us or call 866-832-9315
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Topic: HDPE sheet and Delrin Sheet (Acetal Sheet)

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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Acetal – Delrin Sheet vs. ABS Sheets and Rods

Acetal-Delrin® (Delrin® is a trade name for Dupont’s Acetal Homopolymer) and ABS (Acrylonitrile-Butadiene-Stryene) have some similar properties but are really very different materials. They similarities are: high impact strength, ease of machining with standard cutting tools and good mechanical properties. They are also both FDA compliant and are both good substitutes for brass. They also have great water absorption resistance and good electrical properties. Both materials are good for some of the same applications but certainly not all. Listed below are some of the major differences.Natural ABS Rod, Rods, Sheets and Sheet

ABS Sheet and Rod Information

 

  • ABS comes as Natural (straw) and Black color in Plate, Slab, Sheets and Rods, and thin sheet (.040″ – .250″) it is available as White or Black with a textured surface one side. It can be cut from 48″ X 96″ sheets into strip, panels or pieces.
  • ABS is formable. ABS is a great thermo-formable material while Acetal is not. Acetal is used more for machined parts such as gears and screws. ABS is great for molding and shaping parts from vacuum to heat forming. Excellent for model building and prototype projects.
  • ABS is easily bondable (similar to PVC). ABS can be bonded or welded to itself. Because Acetal is self lubricating, it is not possible for anything to stick to it unless etching is done – therefor it is not bondable.
  • ABS is a great material for painting and silk screening. While Acetal can not be painted or silk screened unless it has undergone Corona Treating (a flame surface treatment), but if treated will nice paint or screened surface.
  • ABS has better chemical resistance than Acetals or Delrin®. Both are attacked by acids like sulfuric, but ABS has a wider range of resistance to chemicals like aqueous acids, alkaline and alcohol. Acetal will degrade when exposed to such chemicals as chlorine and alkalines.
  • Specialty grades of ABS are available, including: Glass Filled, Static Dissapating, and Fire Retardant Grades (like Royalite – R59)Machined Black ABS Rod Part

ABS Typical Properties Table

General Property ASTM

TestTypical ValueR59 Typical ValueSpecific Gravity D7921.041.18 – 1.25Tensile Strength YieldD6386,5005,000Tensile ModulusD638320290,000Izod Impact – NotchedD2567.07.8Hardness – RockwellD785R105R93Deflection Temp @ 264psiD648192174Deflection Temp @ 66 psiD648208195Co. Thermal ExpansionD6965.3X10-54.6 -5.5X10-5

 

Acetal-Delrin® Sheet and Rod Information

  • Acetal is the better machining plastic, considered the best machining plastic material. Because of its durability and wear resistance, Acetal is an excellent choice for producing a wide variety of parts that require high wear resistance over a wide period of time. When machining to tight and specific tolerances, Acetal is ideal.
  • Acetal has low co-efficient of friction. Due to its self lubricating properties, it is a great material for sliding and wear applications. This material provides years of maintenance free bushings and bearings.Natural Acetal Machined Gears
  • Acetal – Delrin sheet is produced from .062″ – over 6″ thick and sheet sizes of up to 48″ X 120″ as standard. The standard color for Acetal and Delrin is Natural (a deep milky white) and Black. Some colors are available as Medical Grade, and can be obtained in limited sizes. These sheet are available cut to: slabs, blocks, plates, slabs and blocks.
  • Delrin – Acetal (Polyoxymethylene) can be both a homo and a co-polymer. The Dupont brand name is a homo-polymer which is a repeating chain of one atom while the generic Acetal is a co-polymer which is two atoms forming a repeating chain. ABS is only a co-polymer.

Acetal – Delrin Properties Table

General Property ASTM Test Typical Value Unfilled Delrin® 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

ABS and Acetal – Similar, but very different materials

Both of these materials possess excellent qualities and have a wide range of different uses. Acetal is great for machining, while ABS is great for forming and bonding. They both can be used for machined parts and are great choices for food contact and electrical applications. These two materials are both strong and durable plastics, but one might be better than the other for a specific job. When picking the right plastic, it is important to compare plastics and their specific properties to make sure the material won’t fail and that your job will be successful.

Contact us for additional information, call us at 866-832-9315 or contact us here. Consider Industrial Plastic Supply for all your plastic needs, we want to be your go-to plastic supplier.

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