All You Need to Know About POM for 3D Printing

Polyoxymethylene, better known as POM, is a thermoplastic used that is considered to be engineer-grade due to its properties. Discovered in 1920, it is currently one of the most widely used materials for injection molding, after polypropylene (PP) and polyamide (PA). It is also becoming increasingly popular in 3D printing. POM is semi-crystalline (it has both amorphous and crystalline zones) and is white.

POM comes in two different forms: the homopolymer (POM-H), marketed by DuPont in the 1950s, and the copolymer (POM-C), marketed by Celanese in the 1960s. While POM-H consists of a single type of monomer, POM-C is composed of several types of monomers. As a reminder, monomers are reactive molecules that can combine to form polymers. The main difference between the two is that POM-H has better mechanical properties, but is less resistant to UV light. POM-C meanwhile has better thermal and chemical properties and therefore reacts better to temperature changes and chemical influences. For these reasons, it is POM-C that is mainly used in 3D printing, also because it is easier to extrude. Please note that in the 3D printing industry, POM is mainly available as a filament, so we will focus on this form.

POM is available in white and easily colorable

Production and Characteristics of POM

In regard to the manufacturing of POM, a distinction must be made between homopolymer and copolymer. POM-H is mainly produced by the direct polymerization of formaldehyde. However, the material can also be produced by transition metal-centered cationic polymerization of trioxane (-CH2-O-)3. The end groups of POM-H are also closed by etherification and esterification to make the structure more stable with respect to the influence of acids or thermal loading. On the other hand, POM-C is produced by copolymerization of trioxane with dioxolane. To ensure stability, unstable end groups are degraded to formaldehyde by hydrolysis.