How DuPont Delrin Rods Compare to Acetal Copolymer Rods

(Newswire.net — June 24, 2015) Anaheim, CA — The first development of POM was in 1952 by German Scientist Hermann Staudinger. Later, in 1952, research chemists at DuPont synthesized a new version of POM called Homopolymer. In 1956 DuPont patented this new Homopolymer Acetal which later was named Delrin. In 1960, DuPont completed their first production plant for this Delrin resin in Parkersburg, West Virginia.

During the same period, Celanese was researching a Copolymer POM version. Celanese began to produce this Copolymer Acetal and called it Celcon. Celanese in partnership with Hoechst AG began production of Celcon in 1962 in Frankfurt, Germany.

Acetal First High Performance Plastic

The evolution of Acetal products brought the first high performance plastic to market. This material combines stiffness, strength, abrasion resistance and lubricity, yielding a material excellent for most moving parts and can replace many metal parts. Common uses for Acetal materials are in conveyor moving parts, automotive parts, sliding and guiding parts, gears, wear strips, zippers, bindings and many more. This tough material is also known for its very low coefficient of friction, making it very slippery.

POM is intrinsically opaque white in its raw resin form. Other colors, including the popular Black Acetal are produced by adding colored pigments. Delrin and Acetal both have high tensile strength and creep resistance. They perform well at low temperatures and high temperatures. Acetal has dimensional stability and high precision tolerance properties which increases the flexibility of designing parts. The most popular Delrin product produced in sheets and rods is DuPont’s Delrin 150SA which has exceptional physical properties.

How do Delrin and Acetal Materials Compare?

The Homopolymer and Copolymer Acetal resins are similar, but not the same. The comparison of physical properties shows that the Delrin excels in many properties.

POM Homopolymer, Delrin, is a semi-crystalline polymer (75–85% crystalline) with a melting point of 175 °C. The POM Acetal copolymer has a slightly lower melting point of 162–173 °C.

Comparison of DuPont Delrin to Acetal Copolymer:

                                           DuPont Delrin                   Acetal Copolymer

Heat Deflection                        257 F                                      220 F

Tensile Elasticity                      450,000                                  400,000

Flexural Strength                     14,300                                    12,000

Rockwell Hardness                  M94                                        M90

Melting Point                            347 F                                      335 F

These properties all point to the DuPont Delrin Homopolymer having better properties. There is one property that doesn’t show up in the data sheets, and that is center line porosity.

These are typical properties from manufacturer’s data sheets, and your values may vary.

What Is Center Line Porosity?

During the processing of the Delrin Homopolymer resin into a finished part or shape, there is outgassing in the material. The outgassing is formaldehyde gas created under heat and pressure in the Delrin resin. The result is a centerline micro porosity. This is a fine layer or zone at the center of a sheet or rod, and the outer surface, where the outgassing settles during production. For many parts and applications this is not a factor. But for parts where the center is needed, and the center needs to be as solid as the rest of the part, this can cause problems. This is especially true with thicker cross sections.

Should I Choose Delrin or Acetal?

In most applications where a part will be used as a wear strip or guide, the material will perform very similar. The more critical the application, the more time is needed to review your options. In many machined parts produced from rod, in diameters greater than 2”, the Acetal is normally the better choice, once again, due to center line porosity. The same is true for thicker Acetal sheets.

Common Acetal Product Manufacturers

The main producers of Acetal resins are: Dupont – Delrin®, Celanese – Celcon®, Korea Eng. Plastics – Kepital®, and BASF – Ultraform®, and several more.

Some of the many converters that use these resins to produce Sheets and Rods are:

Rochling Engineering Plastics – Sustarin C®, Gehr Plastics – POM-C®, Nytef Plastics – Unital®, Engineer Plastics – Tecaform®, Westlake – Pomalux®, Z/L Plastics – ZL900®, and many more.

Picking a resin manufacturer and a shape processor can be confusing. You may need a ‘translator’ to help convert your design to the proper plastic manufacturer. One such supplier of finished sheets, rods and tubes is Industrial Plastic Supply, Inc., helping clients since 1975.