Tim Reichard, one of Piedmont Plastics' Industrial Market Specialists, answers frequently asked questions about acetal.
What is acetal?
Acetal, also known as Polyoxymethylene or POM, is a general purpose engineered thermoplastic. Acetal is an excellent choice for parts that need to be stiff, have low surface friction and maintain good dimensional stability in environments where temperature change and humidity are present. It is also a favorite of machinists for its ease of machining and nice chipping while in process due to its semi-crystalline make up. In natural form, acetal is FDA compliant for food use and even some black acetal is now FDA compliant.
Why is acetal becoming a popular choice for industrial facilities?
Acetal is a popular choice because of its well-rounded characteristics. It’s ability to be used in wear applications, wet environments, and food applications (Natural) make it an all-around great choice in almost all industrial applications. Acetal’s ease of machining, high strength and stiffness, low moisture absorption and many formulation options make it an ideal for multiple parts in a facility.
What is the difference between homopolymer and copolymer acetals?
Acetal is made in two formulations. The first is known as homopolymer (POM-H) commonly known as Delrin (DuPont makes the homopolymer resin that is most commonly manufactured into extruded shapes). The second is known as copolymer (POM-C).
The most important difference between the two formulations is the porosity (bubbles or voids) found in the center due to lower density. This was engineered out by adding another molecular chain to create acetal copolymers, which are porosity free. This is important, as porosity tends to be more prevalent in the thicker or larger sheets and rods in POM-H. Other notable differences are
- Homopolymer has better creep resistance, a higher rockwell hardness rating, a 10 to 15% higher tensile strength and higher operating temperature than POM-C.
- Copolymer is mostly porosity free, outgasses less, has better chemical resistance and better dimensional stability than POM-H.
What are the different types of acetal?
Like I mentioned before, the two formulations of acetal are POM-H and POM-C. Under those two unfilled formulations, there are a myriad of filled types. Some common filled acetals are:
- Acetal 570
- 20% Glass Filled
- Delrin AF, 13-20% PTFE Filled
- Delrin 527, Delrin 511P
- UV resistant grade.
There are many more to consider, and each manufacturer has their own tradenames for their acetal. Some examples are:
- Acetron GP - MCAM
- Sustarin - Röchling
- Tecaform - Ensinger
How does acetal compare to alternative products like metals?
Acetal compares very well to metals, particularly where weight savings and performance in wet environments are needed. Also, acetal’s wear properties shine against metals as well.
Where do you see acetal being used the most?
Any industrial application that requires:
Low moisture absorption, High strength and stiffness, FDA required and wear under load is needed.
Markets include:
Food production, Military contractors, Material’s Handling and many more.
Can acetal improve safety?
Metal-detectable and X-Ray detectable formulations are ideal for food production as safety options to contamination of the food being processed.
What would you like to say to prospective customers who are hesitant to make the switch to acetal?
Give it a try! That’s what I would say. Never met a machinist that didn’t tell me it was their favorite plastic to machine.
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