Plastics Information, Plastics Materials, Uncategorized

Delrin AF Blend, not for food grade applications

Homopolymer Acetal (or Delrin) is one of the more versatile and popular plastics for job shops to machine. Acetal has great physical properties, is easy on tooling and both Homopolymer Delrin and Copolymer Acetal can be found in stock at any reputable plastics distributor.

Delrin AF is an enhanced version of Acetal that can help Delrin AF parts out perform and survive in very demanding applications that unfilled Acetal would not do well in. Despite having a relatively high cost when compared to unfilled Acetal, it is widely used and specified. What is Delrin AF and are all Delrin AF stock shapes the same?

First of all, let’s clarify that there are two types of Delrin AF: Delrin AF (full strength) and Delrin AF Blend. Delrin AF is a UL listed product made by DuPont comprised of a 20% PTFE fiber reinforced Homopolymer Acetal (for more information see What are the ingredients in plastics?). Delrin AF Blend is a 13% PTFE fiber reinforced Homopolymer Acetal. The blend is made by taking full strength Delrin AF and “blending” it down with Homopolymer Delrin (150) material. This is done for a variety of reasons but a primary motivator is to reduce the cost by reducing the amount of PTFE in the product. In the molding world it is common to see a Delrin AF or Delrin AF Blend. In the stock shapes world, Delrin AF Blend is the more readily available standard. A great deal of confusion occurs when a print was originally designed to be molded and then gets converted to a machined part instead. Delrin AF blend (13% Teflon) will have a slightly higher tensile strength, modulus, and impact since there is less filler in the material. Delrin 100AF (full strength) would have better wear since it has higher levels of Teflon. Delrin AF is also UL Listed where as Delrin AF Blend is made of UL Listed components but not necessary listed on its own as a stock shape product.

Now there is another product that lives in this same category but is a hybrid of sorts. Tecaform AD HPV13 is manufactured exclusively by Ensinger Inc and is a proprietary blend of Homopolymer Acetal with a 13% PTFE powder reinforcement. This product can offer similar properties and performance but still falls short of Delrin AF and Delrin AF blend. HPV-13 uses a resin that is not UL Listed but it does carry FDA approval so the primary benefit is that it can be used in food grade applications.

So for applications that require FDA approval in an enhanced Acetal material, HPV-13 is the only product for the job. Be sure to check out the physical property comparison sheets on our website to see how they compare and make sure the HPV-13 is tough enough for your food grade application. We are also ready to help with any questions or concerns you may have.

Plastics Information, Plastics Materials

Acetal: homopolymer (Delrin) versus copolymer, are they different?

Acetal Grades

In my twenty plus years in the plastics industry, there have been materials there have always been materials that were easily confused or misunderstood in terms of their physical properties and/or potential applications. By far the most commonly confused and misunderstood material is Acetal. There are a myriad of reasons why this happens, from a lack of training at the distribution level to the political alliances and capabilities at the manufacturer level.

Either way, we still spend a lot of time explaining and educating on this topic with our customers every day. Our goal is to make sure the Job Shop gets the best material for the job! The reason why this is so important? Acetal homopolymer (or Delrin) and Acetal copolymer (known by various trade names like Tecaform or Acetron GP to name a few) are not the same, they are not equivalents. What they really are is alternatives to each other. It’s not that one is necessarily better than the other, they each have a place in the market and offer some distinct advantages. Using the wrong one can be a source of failures and returns that will cost you time, materials and maybe even a customer.

Time and again we see prints that call out for “Delrin” in the title block are being substituted with Acetal copolymer because the pricing can be more favorable on the copolymer material when compared to Acetal homopolymer. The attraction of the lower price can allow some to rationalize that they are getting the same thing, only cheaper. Take a look at the comparison chart on our website. The tensile strength, creep and fatigue resistance and toughness of homopolymer Delrin are much different than that of copolymer Acetal. Homopolymer Delrin can have increased physical properties in excess of 20% of other Acetal’s.

Black Acetal-porosity line(Click on picture for a closer look)

Center line porosity is another differentiator. Acetal homopolymer has an inherent center line porosity that is not present in Acetal copolymer. Is this a bad thing? It depends on the application, but you have to know if it matters in the end use application. If there is a concern that Acetal homopolymer center line porosity will be a problem, the design can be modified or reinforced to allow the use of Acetal copolymer.

Fatigue endurance is another area of differentiation where homopolymer Delrin will significantly outperform copolymer Acetal. This makes it a more ideal material for various industrial applications especially when maintaining or improving long-term performance is important.

Acetal ASTM

When you request a quote and you want to make sure you will be quoted and sold Acetal homopolymer Delrin, ask the seller to certify it as such. Read the certification carefully. The primary ASTM heading for both items are the same (ASTM D6100-11). The devil is in details of the second level of the specification where S-POM0111=Acetal homopolymer Delrin and S-POM0211=Acetal copolymer.

Either way, Plastics International stocks a vast inventory of both Acetal homopolymer Delrin and copolymer Acetal in natural and black in sheet and rod form. We do not have a minimum order on in stock items so you can get as little or as much of which ever Acetal is right for you. We would be happy to help you make sure you have the right material to meet your customer’s specification. Visit our website at www.plasticsintl.com for more information.