Is Delrin the Same Thing As Acetal?

This is one of our most common questions asked by our new and long term clients, and is a bit difficult to answer. All Delrin is Acetal (POM), but not all Acetal is Delrin. (All Fords are cars, not all cars are Fords)

Acetal is the generic name for the resin, and not all Acetal is Delrin. Several manufacturers produce Acetal resin, including: Celanese, BASF, Ticona, Sabic and many more.

The homo-polymer Acetal resin produced by Dupont and is called Delrin. The generic Acetal covers both the homo-polymer and the co-polymer grades of resin. Both materials meet the basic provisions of the ASTM-D-4181 specification. Homo-polymer is listed under POM 111, and Co-polymer is POM 211.

Both materials are very tough and easily machinable, and they have very similar physical properties. They look the same, but in practical use there are a few differences that may make one better than the other, and it depends heavily on your application. As with all plastic materials, check the typical properties data sheet for the applicable properties you may need for your application. We will also be happy to provide a sample piece for your testing.

An additional difference is the inherit problem of center-line porosity in the homo-polymer grades. This visible center-line is caused by out gassing during manufacturing, and can normally be found at the center or on the surface of all homo-polymer extrusion. This porosity can cause problems with machining or moisture permeation through the material. The co-polymer resin does not have this porosity issue.

Some of the other differences are in the physical properties of the resin. Review the chart for some of the most popular properties people ask for when looking at this industrial and mechanical material.

Properties: Homo-Polymer and Co-Polymer Acetal

Tensile Modulus of Elasticity 450,000 400,000

Flexural Modulus of Elasticity 470,000 366,000

Heat Deflection Temp @ 264 pound

per square inch – degrees F 257 220

Melting Point – degrees F 347 335

Co-effiecent of Linear Therm. Expansion 6.8 x 10-5 5.4 x 10-5

Water Absorption @ Saturation 0.90 0.80

Material is available as Delrin Rod, Acetal Rod, Delrin Block, Acetal Block, Delrin Sheet, Acetal Sheet, and Slabs. One of the most widely available and used plastics, especially on the West Coast (for some reason the East Coast users like the Nylon – Polyamide material more). Most commonly available in Natural (White) or Black, but can also be produced in a wide range of colors with minimum orders. This enables material matching your product color or for easy identification of parts.