Polyamide vs. Nylon: What Are the Differences and Uses?
Learn more about these materials and examples of when to best use them.
The terms “polyamide” and “nylon” are often used interchangeably. However, this is not completely correct. The word polyamide refers to a family of materials with different molecular structures, applications, and properties. Nylon forms part of the aliphatic polyamide subcategory. Aromatic and semi-aromatic polyamides also form part of the larger group of polyamides.
This article will compare polyamides to nylons, describe what the different grades are used for, explain their basic chemical structure, address their mechanical properties, and discuss how to identify them.
Polyamides are a group of synthetic or natural polymers made up of repeating amide groups that are connected by amide links. The hydrogen bonds increase crystallinity, thermal resistance, and chemical resistance. Natural polyamides include materials such as wool, silk, collagen, and keratin. Synthetic polyamides can be broken down into three categories, namely:
- Aliphatic Polyamides: Many grades of nylon belong to this category of polyamide. Typical grades include Nylon 6 and Nylon 6/6.
- Aromatic Polyamides: These polyamides, also called aramids, are typically made into fibers such as Nomex® and Kevlar®. Nomex is used to make fire-resistant fabric. Kevlar is used to make bullet-resistant vests, as shown in Figure 1 below:
Example of bullet proof vests.
Image Credit: Shutterstock.com/MBLifestyle
- Semi-Aromatic Polyamides: These polyamides are high-performance engineering polymers with excellent high-temperature properties. They are also known as polyphthalamides or PPA. Common PPAs are Zytel® and Rislan®.
Polyamides are divided into three categories: aliphatic, aromatic, and semi-aromatic polyamides. Polyamides can be woven into fibers, cast, or injection molded. Polyamides tend to have poor resistance to moisture absorption but have excellent tensile strength and impact resistance depending on the grade.
The molecular structure of polyamides varies widely. Aliphatic polyamides (Nylon) are polymerized from monomers such as caprolactam and hexamethylenediamine and aromatic polyamides are polymerized from para-phenylenediamine and terephthaloyl chloride.
The term “polyamide” refers to a wide range of different materials. A good measure of this is tensile strength. Nylon 6, an aliphatic polyamide, has a tensile strength of approximately 40 MPa. Kevlar® 29, an aromatic polyamide, has a tensile strength of 3600 MPa. This large difference in properties is a testament to the large range of materials in the polyamide group.
Polyamides include a number of subcategories of materials. Listed below are some examples of polyamides and their applications:
- Kevlar®: Kevlar fibers are often woven into bullet-resistant vests, and are also used for reinforcing tires.
- Nomex®: Nomex is a specially formulated fabric with excellent thermal resistance and is used in workwear and fire-resistant suits.
- Nylon: Nylon is used in several different applications and can be spun into a fiber and injection molded. Examples can include gear wheels or rope.
- Wool: Wool is extensively used for the production of clothing, furniture, and carpets.
If there is no datasheet for the material, then the most precise way to identify a polyamide is to send a sample to a lab for destructive testing. Since polyamides refer to a wide range of different materials, visual identification is almost impossible. Polyamides have no distinctive visual characteristics that can help distinguish them. In addition, polyamides can be either stranded or molded.
Molded polyamides like nylon are typically thermoplastics. They will soften when exposed to a specific temperature and will re-harden when cooled. However, other polyamides like Nomex® have very high-temperature resistance. They are also thermosets which makes it impossible to identify them via thermal testing. Calculating the density is another potential method of identifying a polyamide. However, this may not produce a precise enough result to determine exactly what the grade of the polyamide is. Another potential method is the testing of properties, however, the samples must be prepared and tested in accordance with the relevant standards so that they can be precisely compared with supplier values. Ultimately sending samples to a lab is the best option.
Nylon is the trade name given to a group of aliphatic polyamides by DuPont. It is one of the most popular engineering thermoplastics due to its excellent toughness, tensile strength, and wear resistance. Its thermoplastic nature means it can be melted and formed using techniques like injection molding and extrusion, as shown in Figure 2 below:
Nylon cogs and gears.
Image Credit: Shutterstock.com/Paulpixs
Nylon can also be formed into a fabric. There are many different grades of nylon with many different molecular structures and polymerization techniques. Nylon is typically an amorphous polymer but can also have a degree of crystallinity. Aliphatic polyamides are far more prevalent than aromatic and semi-aromatic polyamides. Two of the most common nylons are Nylon 6/6 and Nylon 6.
Nylon is an aliphatic polyamide that can be made with a range of different chemistries. For example, Nylon 6 is made from caprolactam whereas Nylon 6/6 is made from hexamethylene and diamine/adipic acid. Some nylons like Nylon 11, can be produced from renewable sources like castor bean plants via the polymerization of undecanoic acid. The nylon numbering scheme typically has two numbers that refer to the number of carbon atoms in the various reactants. For example, in Nylon 6/6 the first number refers to the number of carbon atoms in the diamine and the second refers to the number of carbon atoms in the diacid. Nylon 6 is only made from one polymer that has 6 carbon atoms. For more information, see our guide on the Properties of Nylon.
Nylon is one of the strongest engineering plastics. It has a high tensile, impact strength, and high abrasion resistance while also having high lubricity. Nylon can have a tensile strength from 40 MPa to 90 MPa depending on the grade. Nylon 6/6, which is a common injection molding grade of nylon, has a tensile strength of 85 MPa. Glass-filled nylon can have even higher tensile strength when compared to unfilled nylon.
Nylon is used in almost all industries for its excellent mechanical properties, including: its tensile strength, wear resistance, chemical resistance, and high strength-to-weight ratio. It is often used as a lightweight alternative to metal. Some examples of applications include: gears, sheaves, pulleys, ropes, textiles, and parachutes.
Nylon cannot be easily identified without specialized techniques, as it does not have any distinctive visual properties. Nylon can be slick to the touch but many other polymers, such as PTFE, for example, will also feel slippery. It may be possible to identify a material as being part of the nylon group by testing its melting point or density. However, the results may not be accurate enough to differentiate between the different grades of nylons. In addition, some nylon grades are blends of two other grades. As such, if it is absolutely critical to identify the specific grade of nylon, and if there is no documentation accompanying the material, then the most precise way to identify the exact chemical compound and grade is to send a sample to a lab for destructive testing.
Nylons are a subcategory of polyamides. They are not an entire class of polymer. However, compared to aromatic and semi-aromatic polyamides, nylon has a lower cost, is easier to process, and has a better balance of properties. Aramids, on the other hand, have higher thermal resistance and tensile strength and are typically processed into fibers. Nylon is also the most common polyamide and is used in many different applications.
Polyamides are a large group of materials with different molecular structures and mechanical, electrical, and thermal properties. In addition, there are many different ways in which the material can be processed, i.e. woven into fabric, cast, extruded, or even injection molded. Listed below are some general examples of polyamides:
- Kevlar®: An aramid fiber with excellent tensile strength and thermal resistance. It is used as a reinforcing material for tires and in bulletproof vests.
- Zytel®: A semi-aromatic polyamide with excellent thermal and tensile strength as well as excellent resistance to moisture and chemicals. Zytel® is often used in the manufacture of firearms.
- Nylon: Nylon is an aliphatic polyamide available in many different grades that cover a wide range of applications from fabric to complex injection molded parts.
Nylon is a type of aliphatic polyamide used in many different industries. It can be produced in a wide range of molecular structures. Listed below are some of the more common grades of nylon:
- Nylon 6: Often used for ropes, seatbelts, and parachutes.
- Nylon 6/6: Often used in engineering applications as a lightweight replacement for metal. Typical applications include gears and sheaves.
- Nylon 12: Moisture absorption is one of the weaknesses of polyamide. Nylon 12 has the lowest moisture absorption rate of all polyamides. Nylon 12 is often used for food packaging.
Yes and no — nylon is a type of polyamide. However, any given polyamide may or may not be part of the aliphatic polyamide group of which nylon is a member. Nylons have different properties and applications than other polymers in the polyamide family.
Yes, polyamides are often processed into fabrics that are also breathable. A good example of this is stockings.
No, nylon is not the same as polyester. Nylon is part of the polyamide family. When trying to compare polyamide vs. polyester, it should be noted that they have completely different molecular structures. The only similarities between nylon and polyester are that they are both available as fabrics, with polyester being the more commonly used polymer for manufacturing fabrics. For more information, see our guide on Nylon vs. Polyester.
Yes, nylon is a polyamide. More specifically, nylon is a trading name for a specific class of aliphatic polyamides.
This article presented polyamide vs. nylon, explained what they are, and discussed examples of each material. To learn more about polyamide and nylon, contact a Xometry representative.
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- Kevlar®, Nomex®, Zytel®, and Rislan® are trademarks of DUPONT SAFETY & CONSTRUCTION, INC. CORPORATION.
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