Know your materials: Nylon
Nylons are a family of strong engineering plastics. Nylons are low-friction plastics, which makes them ideal for replacing metal components like bearings or bushings. Additionally, nylons create less operating noise and wear on mating parts, often allowing for external lubrication to be removed from the component application entirely.
Nylons are thermoplastics (as opposed to thermosets), or synthetic polymers that are extremely workable when heated to high temperatures, yet set firmly when cooled. Many nylons have both amorphous and crystalline microstructures when cooled, giving the material elasticity as well as rigidity and stiffness.
A versatile class of materials, nylons can also be combined with a range of additives to create specific material and chemical properties, which has led to their widespread use in commercial applications ranging from fabric to automotive and electrical molding. This versatility also extends to production, as nylons are compatible with both additive and traditional manufacturing methods.
How is nylon made?
Similar to other plastics, nylons are created by distilling hydrocarbon fuels, which are then introduced to catalysts that produce the plastic polymers. Nylons are typically created in one of two processes: polymerization and polycondensation.
Polymerization creates nylon material by reacting amine monomers (groups of NH2 molecules) with carboxylic acid (COOH), while polycondensation involves the reaction diamine (molecules with two NH2 groups) with dicarboxylic acid (which has two COOH groups).
Nylons created through polycondensation tend to be more biodegradable than those made from addition polymers. Nylons can also be created from biomass, which can also contribute to increased material biodegradability.
Properties and mechanical specifications
The semi-crystalline microstructure of nylon materials provides both stiffness and strength, in addition to good chemical resistance. Nylons are also resistant to heat and are therefore ideal for applications involving friction. As thermoplastics, nylons can also be reheated, molded, and cooled multiple times.
It is important to note that nylon absorbs moisture from its surroundings, which can negatively impact a component’s dimensional stability. Nylons that have greater impact resistance and flexibility also tend to absorb more moisture, though this depends on the material’s crystallinity, the part thickness, and the temperature of the component’s environment.
Nylons can also be preconditioned to help mitigate the effects of moisture absorption. Additionally, it is worth noting that nylon is not inherently resistant to UV light, though stabilizers can be incorporated into the material to reduce damage.
The chemical and physical characteristics of the material will of course vary depending on the specific type of nylon, but here are some of the key mechanical specifications for unreinforced Nylon 6:
- Specific Gravity: 1.13
- Water Absorption: 1.900%, 24 hrs @ 73.4°F (23°C)
- Typical Mold Shrinkage: 1.3%
- Tensile Strength: 76 MPa
- Tensile Modulus: 2758 MPa
- Flexural Strength: 110 MPa
- Flexural Modulus: 2965 MPa
- Hardness: 116, Rockwell R
- Notched Impact Strength: 5.0 kj/m²
- Melting Temperature: 428°F (220°C)
- Deflection Temperature @ 1820 kPa (264 psi): 160°F (71°C)
- Deflection Temperature @ 455 kPa (66 psi): 340 °F (171°C)
Common types of Nylon
Nylons are identified by number — such as 6 or 66 — which refers to the number of carbon atoms between the amine and acid groups, as well as how the polymer was created. Nylon 6, for instance, is created entirely from a single monomer, whereas Nylon 66 is created from combinations of different monomers (called comonomers). Nylons can also be reinforced with additives like glass or combined with other engineering plastics for increased performance and material characteristics.
The three most common types of nylon are Nylon 6, Nylon 66, and PA 12. Nylon 6 filaments are highly elastic fibers that are often used in textiles and high-strength industrial applications, including apparel, ropes, and industrial cords. These fibers have a smooth, glass-like surface that offers outstanding abrasion resistance. Nylon 6 typically results in more reliable final part dimensions.
Nylon 66 is a more crystalline material than Nylon 6 and therefore provides greater stiffness, tensile modulus, and flexural modulus. This makes it an ideal material for applications that require strength, stiffness, and chemical resistance, such as carpets, airbags, and luggage. While a more machinable material than Nylon 6, Nylon 66 has a higher melting temperature, which makes it more susceptible to mold shrinkage. Nylon 66 is frequently used in injection molding.
PA 12 (also known as Nylon 12) is a good general-use plastic with broad additive applications and is known for its toughness, tensile strength, impact strength and ability to flex without fracture. PA 12 has long been used by injection molders due to these mechanical properties. And more recently, PA 12 has been adopted as a common material in additive manufacturing processes for creating functional parts and prototypes.
Nylon is highly valued for its combination of natural low-friction properties and strong mechanical, chemical, and thermal properties. It is a versatile and high-performing family of materials well-suited for applications that receive a lot of wear and tear, such as fuel system components, manifolds, brackets, gears, and other applications that require plastic materials with high melting temperatures. Nylons can also be combined with additives and stabilizers, which enables a greater degree of specificity and control when optimizing the material properties of various components.
Furthermore, since nylons can be shaped into filaments, fibers, films, sheets, and can also be used in conjunction with a range of manufacturing processes — including injection molding, CNC machining, and 3D printing — these materials are often used for prototyping purposes.
Nylon is used widely across many market sectors. Textiles and carpets often incorporate nylon filaments, and FDA-compliant nylon film is frequently used in food packaging because it provides durability, low gas permeability, and temperature resistance.
Nylon parts frequently replace aluminum components in engines, as they are both less expensive (tooling costs aside) and lighter. Nylon offers good electrical insulation and corrosion resistance, which — especially when paired with nylon’s natural toughness — makes it a useful material for electrical applications like cable ties, insulators, and switch housings.
Getting started with nylon
Nylons are a versatile family of thermoplastic materials that provide a unique combination of friction resistance, chemical and thermal resistance, strength, and flexibility. These properties have made nylon a popular choice for applications across a wide range of industries. However, while nylons share some characteristics, they are incredibly modifiable materials, so it’s essential that product teams know the precise material properties needed for a given part. A trusted manufacturing partner can help simplify that process.
Fast Radius is an on-demand digital manufacturer offering both traditional and additive manufacturing services, and our experience working with a breadth of materials — including nylons — makes us the manufacturing partner of choice for product teams everywhere.
Our team of dedicated engineers and designers provide ongoing support during each stage of the production lifecycle, ensuring that customers receive superior quality parts at competitive prices, delivered on-time, every time. Contact us today to find out how we can help make your vision a reality.
You can visit our site to learn more about the services we offer. The Fast Radius resource center also provides insight on everything from how digital manufacturing is changing the global supply to other features on the different materials we work with.