Acetal vs Delrin: Uncovering the Best Choice for Your Plastic Applications

Having knowledge of the distinctions between closely similar options can dramatically help in ensuring the performance and longevity of plastic applications. Acetal and Delrin are two of the most popular choices within the engineering plastics category, and more often than not, they compete against each other for their remarkable gi me electronic properties and mechanical as well as physical behavior versatility. It can be very intricate to decide how the two materials compare to each other and who best fits to serve your specific case. This article seeks to discuss the significant similarities and differences between Acetal and Delrin, providing their characteristics, advantages, and usage. In the end, we will provide guidance to make decisions that best suit the application in question. We will unravel the dispute between these materials and determine the most adequate for your plans.

What is Acetal, and How is it Used in Plastic Applications?

Polyoxymethylene, or POM, is a thermoplastic polymer that possesses exceptional strength, rigidity, and low friction, making it one of the most used materials in the modern world. Within the manufacturing industry, polyoxymethylene is commonly used in high-precision and high-durability components such as gears, fasteners, and bearings. Its low wear resistance makes polyoxymethylene well-suited for automotive components as well as industrial and consumer goods that get moisture or chemicals. It is especially useful In situations where there are drastic temperature and load changes due to its high strength and ability to retain its shape.

Core Benefits of General Acetal Plastics

High Mechanical Strength and Rigidity

• Acetal plastics have exceptional tensile strength and rigididy that makes the material suitable for use in highly demanding applications. For example, the material usually shows a tensile strength in the range of 60-70 MPa, which guarantees reliable performance under considerable stress.

Low Friction Coefficient

• Acetal has a superior performance in moving parts like gears and bearings due to the low friction coefficient value of 0.10 to 0.35 (dry vs dry). This property reduces the wear of components and maximizes their lifetime.

Dimensional Stability

• Acetal is stable with respect to changes in the environment such as moisture and temperature. Its stability along with thermal expansion coefficient which is about 1 x 10⁻⁴ cm/cm/°C guarantees precision in parts with tight tolerances.

Resistance to Abrasion and Wears

• Acetal plastic is the best choice when parts are in constant motion due to the severe mechanical stress. This capability increases the lifetime of components such as conveyor systems and sliding mechanisms.

Chemical Resistance  

• Range of solvents including oils and fuels such as alcohols are resisted by acetal which permits remarkable chemical resistance. Thus, making it the best choice for automotive, and industrial applications where the materials are extensively exposed.

Moisture Resistance

•  According to ASTM D570, Acetal has a water absorption rate of 0.2%-0.3% over a 24 hour period which is relatively low compared to many other plastics. This helps in performing in damp or moist conditions without losing strength or rigidity.

Broad Operating Temperature Range 

• Acetel plastics are thermally resilient allowing them to perform well in low and high temperature applications. They can tolerate a temperature range of -40C to 120C which is -40F to 248F.

Easy Machinability  

• Acetal has great machinability meaning it can be easily cut, drilled or shaped into complex designs. This makes it a preferred choice for prototyping and custom part manufacturing.

Compliance with Safety Standards 

• Some grades of acetal meet FDA standards for food contact which makes them useful in food processing and packaging industries. Additionally, some formulations meet UL-94 HB flammability standards ensuring safe performance in various environments.

Cost Effectiveness

• Compared to metals and other high performance plastics, Acetal is more cost efficient because of its durability, versatility, and long service life. It also enhances output efficiency and makes maintenance cost effective for industrial operations.

Such propitious benefits give engineers and manufacturers in many industries the ability to choose acetal plastics, owing to their unique blend of mechanical properties and versatility.

Different Types of Acetal: Homopolymer vs Copolymer

Two types of these acetal plastics include, homopolymer and copolymer, with each presenting different mechanical properties and use-case benefits. Clearly distinguishing the two variations is vital in choosing the right material for certain applications.

Homopolymer Acetal

Homo-polymer acetal is most commonly known by its trade name Delrin®. It has a high strength-to-stiffness ratio with low wear, making it preferable for use in applications requiring excellent dimensions, stability, and resistance to stretching under continuous loads. Homopolymers tend to have a higher crystallinity, causing an increase in tensile strength and hardness. For instance, the tensile strength of homopolymer acetal is about 69-72 MPa with a density of 1.41 g/cm and is mostly used in making gears, bearings, and other precision mechanical parts. Homopolymer acetal has lower resistance to moisture and chemicals when compared to copolymer counterparts; however, the moisture and chemical resistance is greater than that of copolymer counterparts.

Copolymer Acetal

Unlike others, copolymer acetals have other comonomers that improve their chemical stability, especially in more difficult situations. This version has better resistance to hydrolysis, strong alkaline solutions, and thermal degradation, which makes it preferable for use in the presence of moisture or aggressive chemicals. Although it is slightly less stiff than its homopolymer counterpart, copolymer acetal has improved stiffness over time and better dimensional stability. Typical values for copolymer grades are around 62–65 MPa for tensile strength and a density of 1.41 g/cm³. This makes it a super choice for plumbing components, food processing equipment, and humid environment applications.

Key Considerations

It is best to interpret the requirements of the issue at hand to determine whether homopolymer or copolymer acetal is more suited. For dry mechanical applications that are under very high stress, homopolymer acetal is commonly preferred. On the other hand, for environments which require enhanced resistance to chemical and moisture, copolymer acetal is more suited.

Carefully balancing these properties helps ensure optimal performance and durability in conjunction with technical and operational demands.

Where is Acetal Plastic Used?

Due to its remarkable chemical resistance as well as durability, acetal is often utilized in plumbing fittings, medical equipment, and food preparation tools. In addition, acetal plastic is highly regarded in industries requiring strong materials with low friction and exceptional abrasion resistance. It is often found in gears, pumps, bearings as well as conveyor parts in the automotive, electronics and consumer goods industries. This versatility makes it a preferred material in the manufacturing of precision parts in harsh working conditions.

Understanding the Differences: Acetal vs Delrin

Main Distinctions Between Delrin and Acetal

Although both Delrin and acetal designate sorts of polyoxyethylene (POM) plastics in composition and production, they differ greatly. Delrin is a brand name for a homopolymer acetal resin developed by DuPont, which has higher strength and rigidity. Acetal, as a term, refers to copolymer acetal, which has a better resistance to moisture, wear, and heat but is weaker in mechanical strength compared to Delrin. Making a choice between the two is often dependent on the particular application conditions, such as environmental and mechanical expectations.

Benefits of Delrin over Acetal

Unmatched Mechanical Strength

• When measured in tensile strength and stiffness, Delrin has the upperhand over acetal copolymer. For example, Delrin’s measured tensile strength is around 11,000 psi while the typical measure on acetal copolymer is about 9,500 psi. This means enhances Delrin’s desirability for applications involving heavy loads.

Optimized Dimensional Stability 

• Delrin has a denser molecular structure, which translates to better performance when shrinking or experiencing other changes in dimensions under stress. This is useful for precision parts like gears or bearings that require accurate dimensions.

Lower Friction Coefficient 

• Unlike acetal copolymer, Delrin has a lower coefficient of friction, which mitigates long-term material damage in scenarios involving mechanical movement.

Enhanced Surface Finish 

• With lower surface finish measurements, Delrin is favored for applications where aesthetics are important or for components that require accurate dimensions and a smooth surface.

Greater Rigidity 

• When compared to an acetal copolymer, Delrin is more rigid, allowing it to withstand deformation when subjected to heavy static or dynamic loads.

Reduced Creep 

• When subjected to constant load, Delrin has been noted to outperform acetal copolymers when it comes to creep. This provides enhanced reliability for structural or load bearing components.

Resistance to Fatigue  

• The lifespan of Delrin is enhanced in applications that require repetitive motion or vibration, as it is designed to better withstand cyclical stresses.

Thermal Properties

• Both materials perform well within moderate temperatures, but Delrin exhibits better thermal stability with a melting point hovering around 347°F, while acetal copolymer melts at 331°F.

Chemical Resistance

• Due to its strong resistance to solvents, hydrocarbons, and other Delrin industrial chemicals, it can be used in more extreme industrial contexts. However, it is important to mention that both Delrin and copolymer are vulnerable to strong acids and bases.

These benefits demonstrate why Delrin is ideal for high-performance and precise applications where outstanding mechanical properties and durability are required.

Delrin vs Acetal: Comparison of Mechanical Properties

Tensile Strength

One of the main distinctions between Delrin and acetal copolymer plastic is their tensile strength. Delrin, which has a homopolymer configuration, proportionately possesses greater tensile strength in comparison to acetal copolymer. For instance, Delrin’s tensile strength is commonly estimated between 9,000 to 11,000 psi as opposed to acetal copolymer which ranges from 8,000 to 10,000 psi. Because of its superior tensile strength, Delrin would be the most effective choice for applications that involve high mechanical stress.

Impact Resistance

Acetal copolymer plastic has demonstrated greater impact resistance than Delrin at lower temperatures. The ability of the copolymer to resist notch sensitivity and impact makes it magnet for environments where severe or sudden forces need to be withstood. Although robust, Delrin can crack under sharp impact or quick changes in temperature.

Flexural Strength and Modulus

Flexural properties are another critical consideration. Withstanding bending force under load is best suited for Delrin that demonstrates relatively higher flexural strength around 13,000 psi. The flexural strength of Delrin is also higher than that of acetal copolymer. This adds flexibility at the same time making Delrin helpful in structural components requiring stiffness.

Creep Characteristics

Much like other materials, Delrin homopolymer has better creep resistance than acetal copolymer because it does not deform as much under a sustained load. The acetal copolymer may change shape under certain conditions, but copolymers are able to retain their shape for longer periods of time than copolymers are able to.

Thermal Degradation and Heat Deflection

The other important feature to be analyzed with regard to Delrin and acetal copolymer comparison is their relative thermal resistance. Acetal copolymer has lower heat deflection temperature (about 110 degrees) than Delrin (which has a heat deflection temperature of around 125 degrees), so both materials are able to withstand reasonably high operating temperatures, though Delrin generally outperforms in high-temperature operating conditions. Even so, if either material is held so high for prolonged periods of time, both risk loss of material integrity and performance.

Resistance to Wear and Friction

Both acetal polymers and Delrin have low surface friction and high wear resistance. Low surface friction and high wear resistance, in addition to Delrin’s other properties, make Delrin stand out as a clear choice for moving parts. Acetal copolymer does provide reasonable surface hardness, however it does not compare to the Delrin’s exceptional properties in surface hardness, which offer better protection from surface abrasion than acetal.

Density and Weight

With regards to density, Delrin and acetal copolymer differ very little, however, the slightly greater density of Delrin may lead to slightly heavier parts. Such a difference is often insignificant, but can become important in certain applications where weight is a primary concern.

Summary

The decision of whether to use Delrin or acetal copolymer comes down to the specific application requirements, but both offer superb mechanical properties relevant to industrial and engineering uses. Being a homopolymer, Delrin has higher tensile strength, flexural strength, and creep resistance than acetal copolymer, which makes Delrin preferable for highly precise parts subjected to severe mechanical loads. In contrast, copolymer has superior impact strength and better performance at lower temperatures, which makes it ideal for tough and resilient applications. Both materials offer unique characteristics; therefore, engineers must evaluate the expected operating conditions, thermal requirements, and mechanical needs of the system when choosing the right polymer to use in their applications.

How Does Polyoxymethylene (POM) Relate to Acetal and Delrin?

Defining Polyoxymethylene and Its Role

Polyoxymethylene (POM) is a thermoplastic engineering polymer of relatively low melting point, best known for its use in exceptional parts with high power-to-weight ratio, low resistance, and great dimensional stability. It is the basis of Acetal and Delrin polymers. Its strength, hardness, and wear resistance makes such polymer suitable for use in mechanical and industrial parts like gears, bearings, and other structural components. Being a chemical polymer, it endures many operational conditions and environments while maintaining quality and performance, even very challenging ones.

Comparison of Acetal, Delrin, and POM Properties

Material Composition

• In the realm of polymers, Acetal and POM represent Polyoxymethylene, a specific general class of polymer material.
• Delrin is a brand name of DuPont, who developed it for particular grade or types of POM that has a higher degree of crystallinity and thus better performance for some features.

Mechanical Properties

• Ordinary Acetal/POM materials have high stiffness, low friction, and excellent resistance to wearing, all useful qualities for general industrial applications.
• Delrin offers enhanced strength, impact resistance, and stability with a dimensioned object which makes it ideal for more demanding or precision oriented applications.

Applications 

• Acetal/POM is often used in combination with gears and bearings or in conveyor machinery where moderate stability and durability are satisfactory.
• Delrin is often used where superior mechanical performance is required, for example, in automotive parts, high-tolerance gears, and different complex mechanical assemblies.

Cost Considerations

• Acetal/POM materials are much cheaper for general non-special purposes.
• Delrin, with its specialized properties, typically costs more but serves much more effectively in critical use cases.

Exploring Injection Molding with Acetal and Delrin

Advantages of Using Acetal in Injection Molding

Dimensional Stability

• Components made using Acetal have low thermal expansion coefficient (about 1.1 x 10^–4°C), which ensure performance consistency over a range of temperatures. As the material also possesses impressive dimensional stability, it can be applied in components that require outstanding precision.

Low Friction and Wear Resistance

• Acetal can be employed in sliding applications due to its feature of having low coefficient of friction which ranges from 0.2 to 0.35 against steel. It’s inherent resistance to wear also increases the durability of gear and bearing components that are continuously in motion.

Chemical Resistance

• Acetal can withstand strong fuels, solvents, and weak acids which can damage other materials, making the polymer suitable for harsh surroundings, especially the automobile and chemical processing industries.

Moisture Resistance

• Acetal’s moisture absorption capacity is low (around 0.2% at 23°C and 50% RH), enabling the polymer to better retain its mechanical properties in humid conditions compared to other plastics and thus lowering the chances of dimensional changes.

High Strength and Rigidity

• Acetal has impressive structural strength characteristics with a high tensile strength of about 9300 psi. It also demonstrates extraordinary rigidity, enabling more components to endure mechanical stress with ease.

Good Processability

• Acetal can be processed easily and produced to parts of desired quality through injection molding because of the low melting temperature of 175 – 183 °C, which reduces cycle time and ensures uniform production.

Cost-Effectiveness

• The low material costs and remarkable durability of Acetal make it an economical solution for many industrial uses as compared to other high-performance engineering plastics.

Why Delrin is a Popular Choice for Injection Molding

1. Stability in Dimensions

Delrin, which is an acetal thermoplastic resin produced by DuPont, has remarkable dimensional stability regardless of the surrounding environment. Parts made of Delrin are particularly well-suited for highly precise applications, as its low moisture absorption rate (less than 0.25% at saturation) ensures they will not undergo any volumetric change over time.

2. Minimal Friction and Greater Wear Resistance

The outstanding features of Delrin entail a low coefficient of friction (as low as 0.10 against steel) and remarkable wear resistance. These properties make Delrin a preferred accoutrements in other materials which include gears, bearings, and bushings where smooth movement as well as durability are the utmost important.

3. Compressive and Impact Strength

Delrin is made to withstand repetitive mechanical stress and strain without any deformation or cracking; this is vitally important for parts in automotive and industrial machinery. This makes Delrin exceedingly desirable for dynamic applications, considering it has an impact strength greater than 1.5 ft-lb/in for notched specimens.

4. Performance in elevated temperatures

Delrin is capable of retaining its mechanical qualities even at moderately high temperatures and exhibits a heat deflection temperature (HDT) of up to 120°C (248°F). This thermal capacity widens its use in various applications, such as engine components and electrical fittings.

5. Finishing Surface with a High Degree of Perfection 

Delrin injection molded components are visually appealing with an excellent surface finish and require minimal post-processing. This characteristic is ideal for consumer products such as electronic device housings that need to look professional and visually appealing.

6. Medical and Food Certification 

Some grades of Delrin are compliant with FDA, NSF, and other global standards regarding food contact and medical use. This compliance makes Delrin a preferred material for hygienic and safety-demanding parts such as pump components, valves, and medical devices.

7. Data on the Adoption of Industry 

As per the industry report, the demand for acetal resins, among which Delrin is included, is estimated to increase with a compound annual growth rate (CAGR) of 6.5% until 2030. Its use in the automotive, healthcare, and consumer electronics industries signifies its importance in contemporary engineering.

Delrin’s exceptional mechanical properties, cost efficiency, and adherence to standards make it a flexible and dependable material for injection molding in various industries.

Choosing the Right Material: Factors to Consider Between Acetal and Delrin

Evaluating Chemical Resistance in Acetal and Delrin

Acetal and Delrin differ in their degrees of chemical resistance. While both homopolymer and copolymer acetals have very good resistance to hydrocarbons, solvents, and alcohols, their resistance to strong acids and bases, especially at high temperatures, is much lower. Delrin’s more uniform molecular structure compared to copolymer acetals results in slightly higher resistance to certain chemicals. Therefore, with respect to the chemicals and environmental conditions for the application of interest, one of the options should be chosen.

The Importance of Dimensional Stability

Twenty-three degree stability is crucial when choosing materials in precision engineering and forms the basis of a material’s capability to sustain its size and shape while being subjected to the mechanical loads, temperature, and the environment. Both acetal and Delrin exhibit very high stability, but Delrin has the edge because of its hompolymer structure offering rigidity against deformation and creep over a period of time.

For example, Delrin has a lower coefficient of thermal expansion than the copolymer acetal materials with more than 1.2 x 10*^4 /°C, thus maintaining better dimensional accuracy in high and low-temperature ambient conditions. Moreover, its long-term creep resistance under constant load is about 2% to 4% lower relative to standard acetals, making it more desirable for use in gears and bearings that are continuously loaded.

Delrin also has low moisture uptake of 0.2% in 24 hours at room temperature, thus does not change dimensions in humid conditions, which is beneficial in automotive, medical devices, and electronics industries. These factors explain why Delrin is best suited for use in products with tight tolerances, and where consistent performance is expected throughout the life of the product.

Engineers are able to optimize design functionality and durability by evaluating the dimensional stability properties of the materials in relation to the needs of the application.

Considering Cost and Availability

Due to its superior attributes and performance, Delrin typically has a higher initial cost when compared to standard acetals, which is not particularly economically friendly. However, its use in applications where mechanical strength and dimensional stability are paramount make long-term value justifiable. Standard acetals can be used in less demanding applications because they are widely available and more cost efficient. The tradeoff between the two materials is budgetary limitations and performance expectations for the application.

Frequently Asked Questions (FAQs)

Q: What is the distinction between acetal and Delrin as it pertains to the uses of plastic materials?

A: The key distinction between acetal and Delrin is that the latter is a brand name for a specific type of plastic called acetal homopolymer. Alternatively, acetal copolymer is yet another type of acetal. Delrin, being a polyacetal, has a homogeneous crystalline structure which increases its stiffness and strength, thus enabling its use in applications that require high mechanical properties.

Q: In what way is the crystalline structure of Delrin distinct from other acetals?

A: Instead of having variably formed crystals, Delrin possesses a homogeneous crystalline structure which results in greater strength and stiffness. This particular feature of its crystalline structure enables Delrin to outperform other acetal copolymers in severe applications.

Q: What are the reasons for the choice of Delrin in the CNC machining of plastic components?

A: For CNC machining of plastic, Delrin is the preferred choice because it is semi-crystalline engineering thermoplastic. It possesses excellent dimensional stability, reduced centerline porosity, and better machinability, which are fundamental in manufacturing accurate and complex structures from plastic.

Q: What can you tell us about Delrin’s fatigue resistance characteristics compared to acetal copolymer?

A: Delrin still has superior flex fatigue resistance when compared to acetal copolymer. This is a result of its uniform crystalline structure along with its material properties, due to which it is able to sustain repeated stress and strain over a period of time without any failure.

Q: How does porosity affect the difference between Delrin and acetal copolymer counterparts?

A: Material Delrin generally has less centerline porosity compared to acetal copolymer. In applications requiring strength and uniformity, reduced porosity is critical because it minimizes contained weaknesses within the material that could lead to failure at any given time.

Q: Is Delrin suitable for every type of plastic application?

A: Acetal copolymer is a plastic with outstanding mechanical properties, and while sometimes Delrin is the right choice, it isn’t always the optimal choice depending on the application. Cost, chemical resistance, and environmental conditions are also factors to consider. Some applications may be better served by other plastics besides acetal copolymer.

Q: Where can Delrin and acetal be applied?

A: Acetal and Delrin are frequently utilized in the development of gears, bearings, and bushings, as well as other mechanical parts with high resistance to wear and low-friction performance. Delrin is also preferred in the automotive industry and industrial applications where greater rigidity and toughness are needed.

Q: What should one pay attention to when comparing acetal to Delrin?

A: Stiffness, fatigue resistance, porosity, and application requirements must all be factored in when weighing acetal versus Delrin. For tough applications, Delrin’s greater rigidity combined with lower porosity makes it a better choice, while acetal copolymer is more suited for less demanding environments.

Q: Who sells Delrin and acetal for industrial purposes?

A: EMCO Industrial Plastics is one of the distributors of Delrin® and acetal products, which have a multitude of industrial uses. They stock an extensive range of materials for various manufacturing processes, including CNC machining and custom-built components.

Reference Sources

1. Title: Forecasting surface quality and process parameter optimization in Delrin drilling operations using neural networks

• Authors: V. Kaviarasan et al.
• Journal: Progress in Rubber, Plastics and Recycling Technology
• Published On: June 13, 2019
• Citation Token: (Kaviarasan et al., 2019, pp. 149-169)
• Summary:
• In this paper, the authors study the drilling of Delrin, which is an acetal homopolymer, and its process parameters were optimized for maximum surface quality. Surface roughness modeling was performed by the authors using an artificial neural network with spindle speed, feed rate, and tool point angle as the drilling parameters.
• Key Findings:
• The optimal drilling conditions were determined from the results of the experiments conducted, which yielded a surface roughness of 0.699 µm, the best for Delrin.
• The study explains the importance of using the right machining parameters in enhancing the performance of Delrin in its applications.

2. Title: Advancement of Dimensional Stability and Environmental Durability of Delrin Molded Parts Using Sophisticated Annealing Methods

• Author: Dhrudipsinh Dabhi
• Journal: International Scientific Journal of Engineering and Management
• Published on: 2024-12-08
• Citation Token: (Dabhi, 2024)
• Summary:
• The purpose of this research is to outline the issues pertaining to the moisture absorption and associated dimension alterations of Delrin molded components after the molding process in order to develop an advanced annealing process to achieve improved durability and stability of Delrin parts along with environmental dampening features.
• Key Findings:
• In combination, the annealing procedure reduced moisture and dimensional variability to a significant extent, resulting in better performability of Delrin parts in different environments.
• This work gives insight into the way processes aimed at the construction of Delrin components is conducted for the purpose of making such components durable for outdoor conditions.

3. Title: Surface Microhardness, Flexural Strength, Retention and Deformation of Clasps of Acetal Versus Poly-Ether-Ether-Ketone After pH Aged And Combined Thermal Cycling

• Author: Salma M. Fathy et al.
• Journal: Journal of Contemporary Dental Practice
• Published on: 2021-02-01
• Citation Token: (Fathy et al., 2021, pp. 140-145)
• Summary: 
• This investigation compared some mechanical properties of acetal and poly-ether-ether ketone (PEEK) materials and evaluated their chamfer microhardness, flexural strength, and clasp retention under oral environment simulation conditions.
• Important Results:
• Acetal’s mechanical properties significantly decreased after thermal cycling and pH aging, while PEEK retained its properties better under those conditions.
• This study indicates that PEEK may be a more dependable material for dental work than acetal, particularly for domains changing temperature and pH.

4. Plastic

5. Machining

6. Thermoplastic