Abbreviated POM, this plastic material is available in both homopolymer and copolymer products.
Although the two differ slightly in chemical and mechanical properties, these engineering thermoplastics exhibit not only high strength, but also excellent dimensional stability and a low coefficient of friction.
Delrin manufacturers also offer optional additions to improve this material’s performance. These additions include thermal and oxidative stabilizers, lubricants, and fillers which enhance the material’s natural qualities and make the thermoplastic resistant to moisture, chemical corrosion, solvents, fuels and creep.
Such properties make polyoxymethylene, which is the chemical name of Delrin, popular in several industries including automotive, appliance, construction, hardware, electronics, consumer goods and food and chemical processing among others. Stock shapes are widely available and can be used as the final product or undergo secondary operations to become safe locks, gears, bindings, bearings, fan blades, nuts, screws, wheels, kettles and more.
This particular plastic cannot, however, be used in highly acidic contexts as it quickly degrades in heavy acidic or alkaline applications. Other names for Delrin include polyacetal or polyformaldehyde, in reference to the compounds from which it is synthesized.
Homopolymers begin with the generation of anhydrous formaldehyde, which reacts with alcohol to create hemiformal. This substance is dehydrated before being polymerized by an ionic catalysis, which is stabilized as polyoxymethylene by a reaction with acetic anhydride. Copolymers utilize formaldehyde as well, though it is processed in a different way.
Acid catalysis converts the formaldehyde to trioxane, which is distilled and dried to create Delrin copolymers. Both types of the plastic are commonly provided in a granulated form that is heated to its melting point. Delrin manufacturers can then use injection molding or extrusion processes to form the material into the desired shape.
It is important to consider the final product when selecting a mold as polyoxymethylene has a tendency to shrink as much as 2% during fabrication. In some instances, manufacturers choose to use rotational and blow molding to produce the stock shapes, such as plastic rods, plastic films and plastic sheets, which are distributed by suppliers.
While rods and sheets may be the final product, Delrin manufacturers commonly use secondary operations such as turning, milling, drilling and precision machining to create application specific parts. Because Delrin is a thermoplastic, stock shapes and finished parts can also be melted and remolded or extruded several times as needed.