Full structural formula of the repeating unit
Space-filling model of a polyoxymethylene chain
Other names
Poly(oxymethylene) glycol; Polymethylene glycol
  • none
Molar massVariable
AppearanceColorless solid
Density1.41–1.42 g/cm3
−9.36×10−6 (SI, 22°C) [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
Keck clips made of polyoxymethylene

Polyoxymethylene (POM), also known as acetal,[2] polyacetal, and polyformaldehyde, is an engineering thermoplastic used in precision parts requiring high stiffness, low friction, and excellent dimensional stability. As with many other synthetic polymers, it is produced by different chemical firms with slightly different formulas and sold variously by such names as Delrin, Celcon, Ramtal, Duracon, Kepital, and Hostaform.

POM is characterized by its high strength, hardness and rigidity to −40 °C. POM is intrinsically opaque white, due to its high crystalline composition, but it is available in all colors. POM has a density of 1.410–1.420 g/cm3.[3]

Typical applications for injection-molded POM include high-performance engineering components such as small gear wheels, eyeglass frames, ball bearings, ski bindings, fasteners, guns, knife handles, and lock systems. The material is widely used in the automotive and consumer electronics industry.


Polyoxymethylene was discovered by Hermann Staudinger, a German chemist who received the 1953 Nobel Prize in Chemistry.[4] He had studied the polymerization and structure of POM in the 1920s while researching macromolecules, which he characterized as polymers. Due to problems with thermal stability, POM was not commercialized at that time.

Around 1952, research chemists at DuPont synthesized a version of POM,[5] and in 1956 the company filed for patent protection of the homopolymer.[6] DuPont credits R. N. MacDonald as the inventor of high-molecular-weight POM.[7] Patents by MacDonald and coworkers describe the preparation of high-molecular-weight hemiacetal-terminated (~O−CH2OH) POM,[8] but these lack sufficient thermal stability to be commercially viable. The inventor of a heat-stable (and therefore useful) POM homopolymer was Stephen Dal Nogare,[9] who discovered that reacting the hemiacetal ends with acetic anhydride converts the readily depolymerizable hemiacetal into a thermally stable, melt-processable plastic.

In 1960, DuPont completed construction of a plant to produce its own version of acetal resin, named Delrin, at Parkersburg, West Virginia.[10] Also in 1960, Celanese completed its own research. Shortly thereafter, in a limited partnership with the Frankfurt firm Hoechst AG, a factory was built in Kelsterbach, Hessen; from there, Celcon was produced starting in 1962,[11] with Hostaform joining it a year later. Both remain in production under the auspices of Hostaform/Celcon POM.

Other Languages
català: Poliacetal
čeština: Polyoxymetylén
español: Poliacetal
Nederlands: Polyoxymethyleen
norsk nynorsk: Acetalplast
português: Poliacetal
українська: Поліформальдегід
中文: 聚甲醛