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The Ultimate Guide to Polyoxymethylene: Understanding POM, Plastic, and Polyacetal

The Ultimate Guide to Polyoxymethylene: Understanding POM, Plastic, and Polyacetal
The Ultimate Guide to Polyoxymethylene: Understanding POM, Plastic, and Polyacetal
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Polyoxymethylene (POM), more commonly known as acetal, polyacetal, or just plastic, is an engineering thermoplastic that has transformed several industries across the globe. Its ability to exhibit amazing strength and rigidity while having low friction makes it quite useful for making components in the automotive, aeronautics, electronics, and consumer goods industries. This guide seeks to unlock POM by taking a closer look at its properties, key applications, advantages, and limitations. In this section, we will outline the key reasons why polyoxymethylene remains unique among different plastics, and will also address manufacturers, designers or anyone who is interested to know how the material POM can be useful.

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What Are the Applications of POM?

What Are the Applications of POM?

Polyoxymethylene (POM), also called acetal or Delrin, is a type of plastic material with excellent strength, rigidity, and low friction properties, hence finding its usage in industries that need high-end plastic parts. Key applications include:

  • Automotive Industry: Due to its ability to withstand wear & tear, POM is utilized in manufacturing fuel system parts, door locks, gears, and bushings.
  • Aerospace Sector: POM is a lightweight and robust part that is suitable for fasteners and control systems components.
  • Consumer Electronics: Due to its low friction characteristics, it provides good stability as a housing material for electronic devices, switches, and parts that move in electronic devices.
  • Medical Devices: Surgical handles, insulin pens, and inhalers are manufactured using pom because of their ability to withstand chemicals and their capacity to be precision molded.
  • Industrial Machinery: POM enhances the performance of machine gears, conveyor system parts, and bearings in high-tension applications.

The applications mentioned above clearly depict how POM is vital in a number of industries in making strong and reliable components that are made to last.

How is POM Used in the Automotive Industry?

Owing to its pliability, low friction, and dimension stability, POM has a wide application in the automotive industry. POM products can be found in fuel caps and fuel system housing components as they are resistant to fuel exposure. Other applications include the interior and exterior parts of a vehicle, including door lock systems, window lifters, and seatbelt parts where torque and abrasion resistance are a necessity. Moreover, strong mechanical strength means it can be used for under-the-hood parts like air intake systems and small cogs. Together, all these properties make POM a perfect material for reliable and persistent automotive components.

Why is POM Material Popular in Electronics?

Polyoxymethylene is especially sought after in the electronics sector as it springs together certain requisites conducive to the flawless functioning of electronic equipment. Doors, modules, connectors, and switches that employ modern technology have an exemplary performance owing to POM’s unparalleled dimensional and geometric stability alongside a POM frame. POM has also earned a position as a leading polymer in instances where electrical insulations are highly desired due to its exciting insulating qualities.

As aforementioned, its insulation accommodates a plethora of electronics, which increases moisture, chemicals, and wear. This broadens the scope of parts present in the electronic assemblies, morphing them into different shapes. Hereafter, the POM frame provides a conundrum of low friction settings to components constantly on the move, be it slugs or any rotational mechanism that can be found embedded into the sheet. In tandem, its resistance to high temperatures and durability enhances the manufacturable space of POM, giving rise to compact modern devices.

Notably, a strong push factor for grasping the admittance of POM into the electronics industry is the huge, enormous, intricate structures shooting out of the injection mold when POM is placed at the tip, all the while being sensitive to time constraints. As positivity around global warming strengthens throughout the world, the recycling grades of POM have become increasingly valuable, thus underscoring POM’s eco-friendly nature. Therefore it is no surprise that POM continues to reign supreme within multiple electronic applications.

What Are the Unique Applications of Polyacetal?

The use of polyacetal -also referred to as POM- is vast in cases where there is a high requirement for precision and reliability. It is mostly used in automotive fuel system parts, seat belts, and door lock mechanisms because of its high mechanical properties and wear resistance. When it comes to electronics, POM is a suitable choice for connectors, switches, and housings due to its insulating characteristics and dimensional stability. Furthermore, the material is often found in consumer products such as zippers, gears, and kitchen instruments, which require a high level of durability and low friction. Such applications of POM demonstrate its functionality target across different sectors.

Exploring the Mechanical Properties of Polyoxymethylene

Exploring the Mechanical Properties of Polyoxymethylene

What Makes POM Highly Stiff and Strong?

Polyoxymethylene (POM) has a crystalline polymer structure that gives POM its durability. It has a firm molecular structure which helps increase its inherent strength and rigidity. Also, the trimer possesses high tensile strength and is resistant to deformation; hence, it is suitable for high load-bearing applications. The mechanical properties of POM are further backed by superior fatigue resistance, which enables POM to maintain its mechanical integrity and performance after ceaseless cycling.

How Do the Mechanical Properties Affect Durability?

POM has been known to have remarkable mechanical properties, which make it suitable for use in a wide range of industrial applications. Below are the properties of POM which aid in enhancing the durability of the material:

High Tensile Strength

  • The tensile strength of POM is relatively high, with a range between 60 and 70 MPa, depending on the grade. The strength allows components made from POM to carry loads without warping, ensuring their structural integrity is retained.

Low Coefficient of Friction

  • Due to POM having a low friction coefficient of 0.2 – 0.4, repetitive motion will result in low wear and tear, with gears and bearings being particularly useful.

Exceptional Fatigue Resistance

  • The mechanical integrity of POM during loading and unloading cycles is relatively (not completely) compromised while ensuring its durability is maintained, making the material ideal for constructions that include springs and lever arms.

High Creep Resistance 

  • Even when subjected to high temperature and prolonged stress, deformation of the material does not happen, making POM ideal for structural applications that need stability.

Impact Resistance

  • The material will not crack or break if subjected to force under the impact resistance value of 4 to 12 kJ/m² and is capable of staying intact.

Dimensional Stability

  • POM has both low thermal expansion and moisture absorption which allow its structure to remain unaffected in terms of size and shape under different environmental conditions.

POM’s unique mechanical characteristics make this material a preferred option for use in applications that require unattended operation and are characterized by high loads over a prolonged period.

Understanding the Dimensional Stability of POM Plastic

Understanding the Dimensional Stability of POM Plastic

What is the Significance of Excellent Dimensional Stability?

In situations where performance and form fit must be maintained over the span of time, dimensional stability becomes key. Certain materials like POM offer excellent dimensional stability, which is not altered by environmental conditions, including moisture content and temperature. As a result, parts are less likely to misshape or malfunction, and few or no adjustments are required to the component. Therefore, it will come as no surprise that POM is extensively adopted in the automotive, electronics, and manufacturing industries, where reliability and precision are needed.

How Does POM Maintain Stability Under Temperature Changes?

Polyoxymethylene (POM) has an efficient molecular design that enables it to withstand temperature fluctuations. POM also possesses a high level of crystallinity, which adds to its stiffness and its dimensional stability. This crystalline has been proven to make the material less prone to thermal expansion and contraction, enabling it to operate at a wider temperature range without complications.

Research shows that a material’s thermal expansion coefficient (CTE) explains the extent of its expansion or contraction due to temperature variation and makes POM apt for widths between 8-12×10 6°C. This is perfect for materials that need to be exactly the same size under different temperatures. Also, with a glass transition temperature of about -60°C and a melting point of around 175 degrees, this plastic maintains its integrity without any noticeable melting deformation, even under terrible thermal conditions.

Similarly, POM withstands the concerns of temperature swings alongside moisture with a low humidity absorption rate which in Standard atmospheres stays below 0.25%. This specific property also acts as a deterrent and hinders vapor-induced swelling or distortion, which is a major problem in high moisture and temperature conditions. Thanks to these features, POM is a go-to material for gears, precision parts, and housings in challenging industries such as automotive and electronics, where such properties are compelled to be melted.

Key Advantages of POM as an Engineering Plastic

Key Advantages of POM as an Engineering Plastic

What Are the Key Properties That Make POM Stand Out?

High Dimensional Stability

  • Thanks to their awesome capacity to retain their dimensions, POMs have become popular in making mechanical components that need to maintain tight tolerances for a good period of usage.

Low Friction and High Wear Resistance

  • The said material works well with low friction coefficients and offers a great wear resistance, which is good for moving components like gears and bearings.

Thermal Resistance

  • POM polymers are designed to sustain high temperatures while retaining their mechanical properties and functionality.

Chemical Resistance

  • It exhibits resistance to a range of solvents, fuels, and chemicals, which increases the lifespan of the material under aggressive chemically active conditions.

Low Moisture Absorption

  • POMs show proper resistance to swelling/ distortion due to humidity or moisture because of their high water absorption resistance.

High Mechanical Strength and Stiffness

  • POMs retain and withstand great tensile strains and stiffness which enable functional components and parts to support optimum loads and stress without any deformation.

Considering the above qualities, POMs have become more preferable and more reliable in applications with stringent engineering requirements.

How Does POM Compare to Other Engineering Plastics?

POM is widely regarded as a one-of-a-kind engineering plastic due to its strength in balance when it comes to mechanical, chemical, and moisture absorbance properties. In humid or wet conditions, Princeton POM performs better than Nylon as it has a lower moisture absorbance rate, which allows for better dimensional stability. When dealing with higher tensile stresses, POM’s tensile strength allows the transport of heavy loads due to its added stiffness, which is not the case for polyethylene. In comparison to ABS, POM has low absorbance to chemicals and fuels, which enables a stronger adaptability compared to weaker chemical-resistant plastic. Due to these properties, Princeton POM allows for delicate mechanical components to be used with better durability and stability.

Why is POM Considered a Thermoplastic Material?

Polyoxymethylene (POM) is considered a thermoplastic material because it has the ability to re-soften after being heated and thus gets reprocessed without major damage. This property is ascribed to its structural chemistry, which has semi-crystalline polymers made up of formaldehyde oligomers. Of note, POM polymer’s melting point is around 175 Celsius, which augurs well for high-temperature applications while also allowing it to retain its shape during the cooling process and return to solid form after cooling.

Moreover, POM, like all thermoplastic polymers, can be manufactured into products through injection molding or extrusion methods. For example, the low viscosity of POM, renders it as an ideal candidate for rotational molding of components with thin walls and fine details. Apart from these, as already highlighted, parts with tight tolerances can also be made from POM polymers since they retain superior mechanical properties after the machining process with tensile strength ranging from 60 to 70 MPA with an elongation at the break between 10 to 50 percent depending on grade, i.e., type. Following these traits, POM is highly recommended for use in mechanical devices such as gears, bearings, and car parts, where reliable performance is essential.

The recyclability of thermoplastics such as POM greatly emphasizes the sustainability aspect as compared to thermoset plastics, which cannot be reshaped or remelted. This enables POM to be considered in all sectors for use by designers who can ensure performance as well as avoid negative environmental implications.

Explaining the Differences Between Acetal and Polyoxymethylene

Explaining the Differences Between Acetal and Polyoxymethylene

What is the Difference Between Acetal and POM?

Acetal and Polyoxymethylene (POM) are fundamentally the same thing and are often used interchangeably. While ‘acetal’ is a generic term used prominently in industry, POM is more of a technical term for the polymer. Acetal is used for both the homopolymer and copolymer types of POM. The differences only come on what the material is composed of:

  • POM Homopolymer is a polymer with a uniform molecular structure that has increased strength and stiffness but does not perform or resist heat as well as its counterpart.
  • POM Copolymer has more comonomers that help with long-term thermal heat exposure while also keeping the degradation to a minimum due to chemicals.

The selection of homopolymer or copolymer grade is determined by the thermal, chemical, and mechanical performance requirements of a specific application.

How Does a POM Homopolymer Differ from Copolymers?

The performance and suitability properties of each polymer are greatly affected by the nature of the triangular phase described above. In particular, highly crystalline parts such as Delrin, which are a part of the POM homopolymer family, are very strong, rigid, and highly wear-resistant. This attribute makes it ideal for use in mechanical strength requirements applications like gear wheels and automotive and precision components. This structure, however, diminishes its resistance to thermal wear and makes it more vulnerable to hydrolysis in hot and humid water environments, thus impacting durability in those conditions for long periods of time.

On a different note, the harshness of the environment also tends to lower the hindered transition temperatures (for instance, 77K from -114K, as stated by one study) of POM copolymers, thus resulting in copolymers performing well in high-temperature conditions or whilst under mechanical stress for prolonged periods. The aid of specialty comonomers in POM gyrates and aggregates the polymer chain, removing the region of semi-crystallinity in extrusions, hence doing a phase crystal shift, making them more resistant to hydrolysis. This makes them more viable components in conjunction with hot water and steam in applications such as plumbing, medical, and various other industrial devices.

In quantitative terms, the glass transition temperature of POM homopolymer is around 175°C, to be compared with the values for copolymers typically in the range 162°C. Tensile strength for homopolymer grades can be as high as approximately 69 MPa, whilst for copolymer grades are closer to 65 MPa. These minimal distinctions underscore the compromises made concerning strength and environmental resistance, enabling producers to determine the most suitable grade in relation to the demands of their application.

Frequently Asked Questions (FAQs)

Q: What is the definition of POM, and what are its main features?

A: POM, also called acetal or polyacetal, falls within the family of engineering thermoplastics with performance attributes. It is defined by a combination of factors, including high strength, superior mechanical properties, and high modulus. POM finds extensive application in several products because of its distinct attributes like high melting point, low coefficient of friction and excellent dimensional stability.

Q: What are the various types of accessible POM grades?

A: There are two types of POM: polyoxymethylene homopolymer and polyoxymethylene copolymer. The homopolymer is mechanically stronger and stiffer than its other counterpart; the copolymer exhibits good thermal stability and has excellent resistance to chemicals. Apart from the above grades of POM, different grades are also produced, in which certain additives are included in order to improve various properties of POM for specific applications.

Q: What is the contribution of formaldehyde during POM manufacturing?

A: Formaldehyde is very important in the manufacture of POM resin. POM is a resin where the molecule ‘polyoxymethylene’ is made by linking together large amounts of formaldehyde, which is a polymerized compound. These novel compounds are POM, and their exceptional mechanical and physical characteristics can be attributed to the formaldehyde polymerization process.

Q: What industries typically leverage the application of injection molded for POM?

A: Injection-molded POM is commonly integrated into automotive parts (fuel systems and gears), electronics (zippers and fasteners), medical devices, plumbing, and parts for industrial machinery. This is often due to its high mechanical strength, low-friction plausibility, and decent dimensional stability, which makes it suitable for moving and precision parts.

Q: What temperature range can POM withstand and operate in?

A: The operating temperature for POM is generally within -40C to 100C. In order to withstand slight variance, exposure to temperatures as low as -40F to as high as 212F has proven to not compromise material properties for POM. Depending on the specific needs, some grades can endure temperatures of 140C for a short period.

Q: In the field of mechanical properties, where does POM fall in comparison to other engineering plastics?

A: Typical POM material surpasses a range of engineering plastics when it comes to mechanical properties. POM has high levels of tensile strength, enormous creep resistance, and stellar fatigue endurance. It is also a hard and stiff composite, leading to POM being leveraged where there is a requirement of wear resistance with high retention of shape. POM composites have a low friction coefficient, which makes POM suitable for a plethora of engineering needs. That is POM as a whole function exceptionally well as an engineering composite.

Q: How does POM behave in an electrical field?

A: POM’s electric properties put it in a suitable position for a variety of electrical and electronic uses. The reason is that it has a low conductivity and dielectric constant. This, in particular, allows POM to be placed as an insulator against electricity. Furthermore, humidity and temperature changes do not greatly affect POM’s electrical properties, which allows it to be used in a wide range of electrical parts.

Q: How does molten POM behave during processing?

A: It appears that molten POM maintains its uniqueness through most phases while undergoing processing, flow and filling of complex molds appears to be facilitated through relatively lower melt viscosity. However, upon cooling, the viscosity increases significantly, and POM tends to crystallize quickly, which could result in an unappealing warpage and shrinking if not monitored and controlled correctly. For optimal results, processing parameters, including mold temperature and cooling rate, should be employed to ensure that high-quality POM parts are manufactured.

Reference Sources

1. Polyoxymethylene Das Werkstoff F Modified Partial Dentures Reports, a Literature Review, and a Case

  • Authors: O. Schierz et al.
  • Published in: Journal of Clinical Medicine, Volume 10
  • Publication Date: April 1, 2021
  • Citation: (Schierz et al., 2021)
  • Summary: This literature review addresses the socio-economic and polyoxymethylene pom properties as a material for removable partial denture POM. The advantages of the POM and its exceptional aesthetics and very low mechanical performance suggest that it might replace metal frameworks or other materials. The article examines a case report describing the functional use of POM in the production of semi-permanent semi-removable partial dentures, adding that POM may not be ideal for structural support but may work fair enough for other semi-permanent restorations, the wear factors may limit the time of survival.

2. Molecular dynamics study on friction of polymer material polyoxymethylene (POM)

  • Authors: Xinmin Li et al.
  • Published in: Journal of Polymer Engineering, Volume 44
  • Publication Date: June 10th, 2024
  • Citation: (Li et al., 2024, pp. 375–385)
  • Summary: The purpose of this research is to gain an understanding of the tribological behavior of POM, particularly for its engineering applications. To achieve this, molecular dynamics simulations have been programmed to capture the frictional characteristics of POM as a function of temperature and sliding velocity. Research findings establish that temperature has an insignificant effect on the friction coefficient, but excessive friction depth and sliding certainly encourage the plowing effect and the plastic deformation to become more severe.

3. Inclusiveness of thermoplastic polyurethane elastomer and carbon fiber in polyoxymethylene composites and their characterization for mechanical, thermal and electrical properties

  • Authors: Junhao Yang et al.
  • Published in: Journal of Thermoplastic Composite Materials, Volume 37
  • Publication Date: July 27th, 2023
  • Citation: (Yang et al., 2023, pp. 1135–1149)
  • Summary: The use of thermoplastic polyurethane elastomer (TPU) and carbon fiber (CF) in POM composites was the primary focus of this research as it accepted that CF wraps strengthen cores for composites. This means that CF addition resulted in an appreciable increase of over ten times in the tensile strength and flexural modulus of the composites, in addition to enhancing the anti-static capabilities of the composites. With regards to the modified POM composites, mechanical testing alongside a variety of analytical techniques was incorporated into the research methodology.

4. Examination of Tribological Characteristics Experimentally Using Pin-on-Disk of POM Gear Material “Polyoxymethylene”

  • Authors: Xinmin Li et al.
  • Published in: IEEE Transactions on Instrumentation and Measurement, Volume 73
  • Publication Year: 2024
  • Citation: (Li et al, 2024, pp. 1-10)
  • Summary: This study advances the existing research on the gear POM by conducting pin-on-disk tests to determine the tribological properties of POM through which the authors were able to analyze the impact of contact pressure, POM lubrication, and sliding speed on the friction and wear performance. The results established through the findings showed lubrication to be an important feature in optimizing friction, which varied the wear mechanisms depending on operational conditions.

5. The effect temperature has on polyoxymethylene POM materials’ tribological properties

  • Authors: Xinmin Li et al.
  • Published in: Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology
  • Publication Date: October 29, 2024
  • Citation: (Li et al, 2024)
  • Summary: This paper studies POM and seeks to emphasize the performance variations exposed to different temperature ranges. The research results show that with increased temperature, both friction and wear coefficients increased due to adhesive wear in the secondary mechanism. The methodology consists of experimental temperature conditions to simulate practical scenarios to assess the quality of POM.

6. Polyoxymethylene

7. Thermoplastic

8. Plastic

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