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So much of engineering is about material choices. When you make the right choice, you lift your solution out of the ordinary. We spend a lot of time helping our clients find the right material options – and one of the tougher decisions is choosing between the Delrin and nylon families. Note that Delrin is the brand name for acetal/POM produced by DuPont, who originated the material class.
These two material groups stand out for their versatility, strength, and all-round adaptability in industrial applications. Both are appreciated for their mechanical, chemical, and thermal properties and both find widespread application across divergent sectors, from automotive and consumer goods to medical devices and electronics. But note: neither of them offers beauty to go with their serviceability. These are engineering materials!
Each has unique benefits that make it the better option for various applications. And then sometimes the choice is less clear.
Below, we are aiming for a comprehensive comparison between the two. We will explore the properties, advantages, limitations, and applications of these two material classes in the key areas of strength, toughness, wear resilience, chemical durability, moisture resistance, temperature tolerance and processing – machining and molding.
An understanding of the differences between these two classes will equip you to make informed decisions as to which is the right choice for your tasks.
Overview of Delrin (Acetal/POM)
Delrin is a brand name for a wide family of variants/grades of acetal homopolymer, copolymer, and additive-modified materials available as molding grades, or cast slabs/rods—or both. At its core is a high-performance engineering plastic developed by DuPont, polyoxymethylene (POM), polyformaldehyde, or polyacetal. It is generically referred to as acetal, and its primary features include toughness, excellent dimensional stability and coefficient of low friction. Delrin is appreciated in engineering roles for its combination of high strength, stiffness, and toughness, making it a popular choice for precision parts that require consistent performance over time.
Delrin is either a homopolymer, meaning it consists of a single type of repeating unit produced by catalytic polymerization of the hemiformal monomer, OR it is a copolymer resulting from the copolymerization of dioxane and trioxane monomers purified by melt or solution hydrolysis.
The resulting structures give a higher degree of crystallinity in homopolymers, whereas acetal copolymers typically result in lower crystallinity, superior toughness, better fatigue resistance, higher stiffness, and greater wear resilience than the homopolymer forms.
Key properties of Delrin
- High strength and stiffness: Delrins are known for near-metal levels of strength-to-weight ratio and rigidity, making them suitable for load-bearing applications.
- Low coefficient of friction: This makes them ideal for applications where low wear and smooth movement are required.
- Dimensional stability: Delrins exhibit outstanding dimensional stability, even in humid environments, making them suitable for precision parts that must maintain tight tolerances.
- Wear and abrasion resistance: Delrin is highly resistant to wear, making it a preferred material for gears, bearings, and other components that experience continuous motion.
- Impact resistance: Delrin’s toughness allows it to withstand impact forces without cracking or breaking — more so for copolymer, than for homopolymer which is more brittle due to higher crystallinity.
- Good chemical resistance: Delrin is resistant to a wide range of chemicals, including solvents, fuels, and weak acids.
The property differences between grades of Delrin generally stem from the degree of crystallinity — higher for homopolymer, which is stiffer/harder, lower for copolymers, which is more resilient, temperature-tolerant and chemically resilient.
Applications of Delrin
Delrin of various grades, is used across a huge range of engineering products in most market sectors, due to its advantageous and varied properties, which are altered by degree of copolymerisation and by additives.
- Automotive components: Delrin is widely used in automotive parts such as gears, fuel system components, and door mechanisms.
- Electrical connectors: The material’s dimensional stability and extreme breakdown voltage make it ideal for precision connectors and terminals.
- Industrial bearings and bushings: Delrin’s low friction and wear resistance, reduced further by PTFE or graphite additions, make it optimally suitable for bearings.
- Medical devices: Delrin is used in various medical device components due to its biocompatibility and resistance to sterilization processes. In particular, the low porosity resulting from some production processes, combined with high chemical/radiation/heat tolerance make it resistant to the most aggressive sterilization methods.
Overview of the Nylon (Polyamide) Family
Nylon is another popular engineering plastic, from a family known for toughness, flexibility, and wear resistance. Nylon belongs to the polyamide family of plastics, which are characterized by the presence of amide linkages in their molecular structure. The most common types of nylon are nylon 6, nylon 11, and nylon 6/6, which differ slightly in their molecular structures but closely parallel mechanical properties.
Nylons are versatile materials that serve in applications where wear resistance, toughness, and chemical resistance are critical. It is commonly reinforced with other materials, such as glass fibers, carbon fibers etc., to further enhance its mechanical properties. Nylon is also known for its excellent resistance to abrasion, making it suitable for parts that experience otherwise detrimental levels of friction.
Key properties of Nylon
- High toughness: Nylon is considered to be very tough, offering both high impact resistance and the ability to tolerate significant distortion without breaking.
- Excellent wear resistance: These materials are renowned for their resistance to wear and abrasion, making them ideally suited to applications involving repetitive sliding/rotating motion and wear potential.
- Flexibility: Nylon is more flexible than Delrin, making it better suited for applications that require both toughness and flexibility. This flexibility also implies lower dimensional resilience, making it less suited to higher-precision applications.
- Chemical resilience: They are typically highly resistant to a wide range of chemicals, including acids, alkalis, oil/grease, and fuels.
- Moisture absorption: One of nylon’s main drawbacks is its tendency to absorb moisture, which adversely affects its dimensional stability and mechanical properties proportionately to the hydration level.
- Heat resistance: Nylon exhibits good heat resistance (typically 140°C but with reduced resilience), though it can degrade in long-term exposure to high temperatures. Nylon 4.6 is among the higher performing grades, surviving up to 140°C but retaining better creep and stiffness at this level than nylon 11 or 6/6.
Applications of Nylon
Nylon’s desirable combination of toughness, flexibility, and wear resistance, and low friction makes these materials a widely selected option in many high-stress and moving-part applications.
- Gears and bearings: Nylon’s intrinsic wear resistance and low friction make it ideal for gears and bearings in mechanical systems.
- Textiles: Nylon, as drawn fibers, is widely used in the textile industry for the production of very hard-wearing fabrics.
- Automotive parts: The material is used in various automotive applications, including under-the-hood components, high-speed/low-stress gears, and hoses.
- Industrial components: Nylon is used in a variety of industrial applications, such as conveyor belts, rollers, wheels, structural elements, and rope/chain pulleys.
- Consumer goods: Nylon is used in the production of everyday items such as toothbrushes, zippers, and kitchen utensils.
Nylons are generally considered to have poor cosmetic qualities and be unsuitable for aesthetic applications, although some grades, such as nylon 6-3-T (or nylon TMDT), are high-cosmetic, glass-clear variants.
Strength and stiffness
Delrin typically has higher strength and stiffness compared to Nylon. It maintains its rigidity even in low-temperature environments, making it suitable for precision components that require dimensional stability. Nylon, on the other hand, is more flexible and tough, allowing it to absorb impact without breaking. However, Nylon’s flexibility can also make it less suitable for applications that require high stiffness and rigidity.
Wear and friction
Both Delrin and Nylon offer excellent wear resistance, but Delrin copolymer’s reliably lower coefficient of friction, combined with dimensional stability, makes it more reliable for bearings. For example, Delrin is often used in gears, bearings, and sliding components where smooth movement is essential. Nylon also performs well in these applications, but its generally slightly higher friction coefficient means higher wear.
Moisture absorption
One of the most significant differences between Delrin and nylon is their behavior in immersed or humid environments. Nylon is hygroscopic, meaning it absorbs moisture from the air—up to a ceiling of 8% which is 10x the level for Delrins. This can lead to dimensional changes—both swelling and distortion—and a decrease in mechanical properties over time. Delrin, having near-zero moisture absorption, retains its dimensional stability even in hot-immersed conditions, making it equally precise under all normal environmental conditions.
Chemical resilience
Both Delrin and nylon offer good chemical resistance, but Delrin tends to be more resistant to a wider range of chemicals, including fuels, solvents, and weak acids. Nylon is resistant to oils, greases, and milder fuels, but its chemical resistance breaks down under exposure to strong acids or alkalis.
Temperature resistance
Some nylons have greater heat tolerance than typical Delrins without degrading. Nylon is often used in applications where components are exposed to elevated temperatures for extended periods. Both homopolymer and copolymer Delrins, while capable of handling moderate heat, show risk of deforming under load or losing strength when exposed to hot conditions.
Machinability
Both Delrin and Nylon offer good machinability, but homopolymer Delrin generally performs best in precision machining. The lower friction coefficient and better dimensional stability facilitate tighter tolerances and smoother finishes when tools are sharp. Nylon’s flexibility renders it more challenging to machine precisely, and moisture absorption creates moderate dimensional uncertainty.
Moldability
Delrin and Nylon are both versatile injection molding candidates, with different properties in moldability. Delrin (acetal) offers excellent dimensional stability, making it ideal for precision components. Nylon delivers lower dimensional reliability due to the moisture absorption influence. Many Delrin grades have a moderately poor melt flow index (MFI), low in the range of 9-35 g/10 min, limiting their use in fine sections and complex parts. Nylons typically have a higher MFI, often high in the overall range of 10-30 g/10 min, depending on grade, equipping the material to form finer sections.
Selection between Delrin and Nylon
The choice between Delrin and Nylon ultimately depends on the specifics of the application. The decision will typically flow from these criteria:
- For applications requiring high dimensional stability, low friction, and good wear resistance, a Delrin derivative will usually be the better option. Gears, bearings, and electrical connectors that must maintain tight tolerances and smooth sliding/rotation are generally better performing in Delrin.
- For applications involving high impact forces, requiring components to tolerate mechanical shocks, Nylon’s toughness and flexibility make it a better option.
- A typical nylon is also marginally better than the best-performing Delrin, where heat resistance is critical, such as automotive and industrial components.
- If moisture absorption is a concern, Delrin is more suitable, as Nylon can be a high-risk choice if wet-strength or dimensional stability are demanded.
- If chemical resistance is a key factor, both families of materials offer good resistance to oils, greases, and fuels, but Delrin generally offers better resistance to a wider range of chemical and solvent exposures.
Conclusion
Both Delrin and Nylon are highly versatile engineering plastics with distinct advantages and limitations. Delrin excels in applications that require high strength, stiffness, low friction, and excellent dimensional stability, while Nylon offers superior toughness, flexibility, and heat resistance.
A well-informed grasp of the specific needs of your application and the properties of these two material families, and their various grades will enable you to make an informed and equipped decision that optimizes your outcomes, balancing performance, durability and cost.
