Polyoxymethylene in the context of "Ultra-high-molecular-weight polyethylene"

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⭐ Core Definition: Polyoxymethylene

Polyoxymethylene (POM), also known as acetal, polyacetal, and polyformaldehyde, is an engineering thermoplastic used in precision parts requiring high stiffness, low friction, and excellent dimensional stability. Short-chained POM (chain length between 8 and 100 repeating units) is also better known as paraformaldehyde (PFA). As with many other synthetic polymers, polyoxymethylenes are produced by different chemical firms with slightly different formulas and sold as Delrin, Kocetal, Ultraform, Celcon, Ramtal, Duracon, Kepital, Polypenco, Tenac and Hostaform.

POM is characterized by its high strength, hardness and rigidity to −40 °C. POM is intrinsically opaque white because of its high crystalline composition but can be produced in a variety of colors. POM has a density of 1.410–1.420 g/cm.

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👉 Polyoxymethylene in the context of Ultra-high-molecular-weight polyethylene

Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene (HMPE), it has extremely long chains, with a molecular mass typically between 2 and 6 million daltons. The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made.

UHMWPE is odorless, tasteless, and nontoxic. It embodies all the characteristics of high-density polyethylene (HDPE) with the added traits of being resistant to concentrated acids and alkalis, as well as numerous organic solvents. It is highly resistant to corrosive chemicals except oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating (see boundary lubrication); and is highly resistant to abrasion, in some forms being 15 times more resistant to abrasion than carbon steel. Its coefficient of friction is significantly lower than that of nylon and acetal and is comparable to that of polytetrafluoroethylene (PTFE, Teflon), but UHMWPE has better abrasion resistance than PTFE.

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Polyoxymethylene in the context of Harpsichord

A harpsichord is a keyboard instrument that makes its sound by plucking a set of strings. In a harpsichord, depressing a key raises its back end within the instrument, which in turn lifts one or more jacks, each a thin strip of wood holding a small plectrum made from quill or plastic; each plectrum plucks a single string. The strings are under tension on a soundboard, which is mounted in a wooden case; the soundboard amplifies the vibrations from the strings so that the listeners can hear them. Harpsichord often include more than one choir of strings. Various devices are used to select which choir will sound when playing; these can include simple levers, or in more elaborate instruments the deployment of more than one keyboard .

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Polyoxymethylene in the context of Paraformaldehyde

Paraformaldehyde (PFA) is the smallest polyoxymethylene, the polymerization product of formaldehyde with a typical degree of polymerization of 8–100 units. Paraformaldehyde commonly has a slight odor of formaldehyde due to decomposition. Paraformaldehyde is a poly-acetal.

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LINKED FROM (PARENTS)
← Harpsichord ← Ultra-high-molecular-weight polyethylene ← Paraformaldehyde
LINKS TO (CHILDREN)
Ground glass joint → Thermoplastic → Stiffness → Friction → Paraformaldehyde → Polymer →