Difference Between Acetal and Delrin

Main Difference – Acetal vs Delrin

A thermoplastic polymer is a compound that can be repeatedly heated and molded into a definite shape. Therefore, most products are formed from thermoplastic polymers. Acetal is a thermoplastic polymer. Delrin is a type of acetal. Acetal is the common name used for polyoxymethylene. Acetal plastic is produced as either homopolymer acetal or copolymer acetal. Delrin is a homopolymer form of acetal. Therefore, Delrin is a derivative of acetal. All Delrin is acetal but not all acetal is Delrin. Delrin is a type of acetal produced by the company named DuPoint. The main difference between acetal and Delrin is that acetal can be found as either a homopolymer or a copolymer whereas Delrin can be found as a homopolymer.

Key Areas Covered

1. What is Acetal
      – Definition, Synthesis and Properties
2. What is Delrin
      – Definition, Synthesis and Properties
3. What is the Relationship Between Acetal and Delrin
      – Acetal and Delrin
4. What is the Difference Between Acetal and Delrin
      – Comparison of Key Differences

Key Terms: Acetal, Copolymer, Delrin, Homopolymer, Polymer, Polyoxymethylene, Thermoplastic

What is Acetal

Acetal is a thermoplastic polymer that is used for the production of many products due to its high strength and low friction. Acetal polymer is made as either a homopolymer or a copolymer. The name acetal is the common name used for polyoxymethylene (POM). Acetal has an opaque white appearance, but it is commercially available in various colors. The chemical formula of acetal is given as [CH₂O]_n. The density of this polymer is about 1.42 g/cm³.

Figure 1: Polyoxymethylene Chemical Formula

In the synthesis of homopolymer acetal, anhydrous formaldehyde is generated, followed by the polymerization of this anhydrous formaldehyde through anionic catalysis. However, the process of this synthesis results in a considerable centerline porosity. In the synthesis of copolymer acetal, about 1% of –CH₂O groups are replaced with –CH₂CH₂O groups.

Properties of Acetal

High strength
Excellent machinability
Low friction
Excellent wear properties in both wet and dry environments
Chemical resistance – Acetal is chemically resistant to many fuels and solvents.

The heat deflection temperature for homopolymer acetal is about 257 ⁰F whereas it is about 230 ⁰F for copolymer acetal. The water absorption capacity of acetal varies from 0.20% to 0.25%. The applications of acetal include the production of bearings, pump and valve parts, gears, wear pads and electrical components.

What is Delrin

Delrin is a homopolymer form of acetal. It is a form of acetal resin produced by a company named DuPoint. The heat deflection temperature of Delrin is about 257 ⁰F. The water absorption of Delrin is about 0.25%.

Delrin product is sold in several forms such as Delrin rod, Delrin block, Delrin sheet, etc. The mechanical properties of Delrin are high. Delrin is produced by the polymerization of anhydrous formaldehyde through anionic catalysis. This method causes the creation of a centerline porosity in cross sections of the polymer material. This region is called a low-density centre due to this porosity. Delrin is less resistant to chemicals than other acetal polymers.

Figure 2: Commercially Available Delrin Rods

Delrin is available in different colors, including black color. The flexural modulus of Delrin is comparatively very high. It is about 420,000 psi. (Flexural modulus is the tendency of a material to bend).

Relationship Between Acetal and Delrin

Acetal can be produced as a homopolymer acetal form or a copolymer acetal form.
Delrin is a homopolymer form of acetal.

Definition

Acetal: Acetal is a thermoplastic polymer that is commonly used due to its high strength and low friction.

Delrin: Delrin is a homopolymer form of acetal which was first produced by the company named DuPoint.

Porosity

Acetal: Homopolymer acetal has porosity and copolymer acetal has no porosity.

Delrin: Delrin has centerline porosity.

Density

Acetal: The density is almost even in copolymers and some homopolymer acetal forms.

Delrin: Delrin has a low-density centre due to the presence of porosity in the centre.

Production

Acetal: Homopolymer acetal forms are produced through polymerization of anhydrous formaldehyde whereas copolymer acetal is formed by replacing 1% of acetal groups from –CH₂CH₂O groups.

Delrin: Delrin is produced by the polymerization of anhydrous formaldehyde through anionic catalysis.

Flexural Modulus

Acetal: The value of flexural modulus for acetal depends on whether it is a homopolymer or copolymer.

Delrin: The value of flexural modulus for Delrin is about 420,000 psi.

Stiffness

Acetal: The stiffness of homopolymer acetal is greater than that of copolymer acetal.

Delrin: The stiffness of Delrin is very high comparatively.

Cost

Acetal: Acetal is comparatively cheap.

Delrin: Delrin is expensive than acetal.

Conclusion

Acetal is a thermoplastic polymer. Therefore, the products made of acetal can be melted and molded to reuse several times. Acetal can be produced as either homopolymer acetal or copolymer acetal. Delrin is a homopolymer form of acetal. The main difference between acetal and Delrin is that acetal can be found as either a homopolymer or a copolymer whereas Delrin can be found as a homopolymer.

References:

1. “Acetal.” Curbell Plastics, Available here. Accessed 28 Aug. 2017.
2. “Why Choose Acetal Or Delrin.” Directplastics, Available here. Accessed 28 Aug. 2017.

Image Courtesy:

1. “Polyoxymethylene” By Yikrazuul – Own work (Public Domain) via Commons Wikimedia
2. “South Bend Lathe Delrin stock for machining (17051720658)” By Nathanael Burton – Delrin stock for machining, (CC BY-SA 2.0) via Commons Wikimedia