Polyamide is the general term for all polymers that contain amide linkages. Nylon was originally DuPont’s trademark for the synthetic polyamides PA6 and PA66 developed for industrial and consumer applications. Although nylon is a subset of polyamides, the two terms are not entirely interchangeable. In this article, we will explore the relationship between polyamide and nylon and offer a detailed comparison of their key properties and performance.
What Is Polyamide?
Polyamide (PA) is a class of high-molecular-weight polymers whose repeating units are linked by amide (-CO-NH-) bonds. Polyamides can be either natural or synthetic. Natural polyamides include wool, silk, collagen, and keratin. Synthetic polyamides can be classified into three categories:
Aliphatic Polyamides (PA6, PA66, PA11, PA12): A good fit for general engineering. They balance strength, toughness, wear resistance, and easy processing at reasonable cost.
Aromatic Polyamides (Aramids such as Kevlar® and Nomex®): Best for extreme performance. Para-aramids like Kevlar® offer exceptional tensile strength and cut resistance, while meta-aramids like Nomex® are prized for inherent flame resistance and thermal stability. They are expensive and not melt-processable, so part shapes and manufacturing routes are more limited.
Semi-Aromatic Polyamides (PPA, PA6T, PA6/12T): Targeted at high-temperature engineering. They keep stiffness and dimensions at elevated temperatures and handle many automotive fluids well. They can be melt-processed (injection/extrusion) but run at higher melt temperatures and need careful drying. Cost sits between aliphatic PAs and aramids.
They have increased crystallinity, good thermal and chemical resistance, and a tendency for moisture absorption due to hydrogen bonding between molecular chains—although the extent of these properties varies greatly by type. Their mechanical properties (tensile strength, elastic modulus, elongation at break) are closely tied to chain rigidity and crystallinity: the higher these are, the stiffer and stronger the material, but also the more brittle; lower values result in softer, tougher materials.
Common Grades of Polyamides
Below is a summary of the most common synthetic polyamide grades, their key properties, and typical applications.
Grade
Common Name
Monomer(s)
Carbon Count
Polymerization
Tensile Strength (MPa)
Elastic Modulus (GPa)
Melting Temp (°C)
HDT (°C, dry, 1.8 MPa)
Moisture Absorption (%) @50%RH
Chemical Resistance
PA6
Nylon 6 (synthetic)
Caprolactam (ε-caprolactam)
6
Ring-opening polymerization
60–75
1.6–2.5
220–225
65–75
2.4–3.2(~9–11% saturated)
Good oil/fuel resistance; sensitive to strong acids/bases
PA66
Nylon 6,6
Hexamethylene diamine + adipic acid
6+6
Condensation polymerization
70–85
2.5–3.0
255–265
75–85
2.5–3.5(~8–9% saturated)
Similar to PA6, slightly better solvent resistance
PA11
Bio-based polyamide
11-aminoundecanoic acid
11
Self-condensation
50–65
1.2–1.8
185–190
55–65
1.5–2.0
Excellent chemical resistance, salt spray, fuel resistance
PA12
Long-chain polyamide
Lauryl lactam
12
Ring-opening polymerization
45–55
1.6–1.8
178–180
50–60
0.5–1.0
Similar to PA11; outstanding chemical resistance
PA46
High-temp polyamide
Tetramethylene diamine + adipic acid
4+6
Condensation polymerization
80–100
3.0–3.5
~295
160–170
2.0–3.0 (higher when saturated)
Excellent high-temp, oil, and wear resistance
Kevlar
Para-aramid
p-Phenylenediamine + terephthaloyl chloride
—
Condensation polymerization
3000-3600
70–130
No melting; decomposes >500 °C
Retains properties up to ~300 °C; decomposes >500 °C
3–7 (moisture regain @65%RH)
Resistant to most chemicals; UV sensitive
How to Identify Polyamides
You can quickly screen polyamides with simple hands-on tests—start with a burn test (they melt then burn with a blue flame tipped in yellow, give off a celery-like odor, and leave a hard black bead) or a hot-needle test (they soften cleanly with the same odor). Note that PA6/PA66 (density ≈1.13–1.15 g/cm³) sink in water, whereas long-chain grades like PA11/PA12 (≈1.01–1.03 g/cm³) may float in water or dilute alcohol. For a definitive lab ID, use FTIR spectroscopy to detect the characteristic N–H stretch (~3300 cm⁻¹) and C=O stretch (~1630 cm⁻¹), and employ DSC to confirm melting points (PA12 ≈178 °C, PA6 ≈215 °C, PA66 ≈260 °C).
What Is Nylon?
Nylon is the most famous subset of synthetic polyamides. In practice, when people say “polyamide” in plastics or textiles, they are almost always referring to nylon-type materials.
Most widely used commercial nylons—such as Nylon 6, Nylon 6/6, Nylon 11, and Nylon 12—are aliphatic polyamides. Their semi-crystalline microstructure and strong hydrogen bonding give them an excellent combination of strength, toughness, wear resistance, and good heat and chemical resistance for general engineering. Versatile and dependable, they can be processed through a wide range of conventional manufacturing and additive techniques, making them a long-standing staple in the family of engineering plastics.
How to Identify Nylon
Overall, the methods used to identify nylon and polyamide—both in the field and in the lab—are essentially the same. The main difference is that nylon grades require more precise criteria for accurate distinction. In laboratory settings, Differential Scanning Calorimetry (DSC) is commonly used to measure melting points and pinpoint specific grades. Density testing provides a quick way to separate long-chain nylons (PA11/PA12) from short-chain nylons (PA6/PA66). When further confirmation is needed, techniques such as X-ray diffraction (XRD) or melt flow rate (MFR) analysis can be applied to distinguish 6-series from 11/12-series materials with greater accuracy.
Common Properties of Polyamides and Nylon
“Polyamide” and “nylon” are often used interchangeably, though nylon is only one type of polyamide. This section details their common properties.
Composition and Structure
Polyamides are characterized by repeating amide (-CO-NH-) bonds in their backbone but can be synthesized from many monomers. Aliphatic polyamides are built from straight-chain units such as ε-caprolactam, hexamethylenediamine with adipic acid, or 11-aminoundecanoic acid, while aromatic aramids incorporate rigid benzene rings into the chain. The choice of monomer and the polymerization method determine chain flexibility, crystallinity, and hydrogen-bonding density—factors that in turn influence mechanical strength, thermal stability, and resistance to oils, fuels, and many chemicals.
Nylon is the subset of aliphatic polyamides made from a narrow monomer set. Common nylon grades include PA6, made from ε-caprolactam, and PA6,6, produced by condensing hexamethylenediamine with adipic acid. Their uniform chain segments and strong hydrogen bonding create a semicrystalline network that delivers a balanced mix of tensile strength, toughness, wear resistance, and moderate heat resistance.
Melting Point
A polyamide’s (including nylon’s) melting point is decided by four main factors: monomer chemical structure, degree of crystallinity, hydrogen-bonding density, and chain flexibility. In general, more numerous and regularly spaced hydrogen bonds and higher crystallinity raise the melting temperature; conversely, flexible chain segments that disrupt crystal formation lower the melting points. For example, long-chain, low-crystallinity polyamides such as PA11 and PA12 melt around 178–180 °C, common nylons like PA6 and PA6/6 melt between roughly 215 °C and 265 °C, and rigid aromatic polyamides such as Kevlar do not melt under atmospheric pressure, instead decomposing above 500 °C.
Tensile Strength and Toughness
In general, nylons provide a balanced combination of strength and toughness, while other polyamides offer a wider range of performance tuning. At the high-strength end, aromatic aramids such as Kevlar® achieve fiber tensile strengths up to about 3.6 GPa (~3600 MPa) and excel in energy absorption under ballistic impact. At the other end, long-chain aliphatic polyamides like PA11 and PA12 trade some tensile strength (~45–60 MPa) for superior ductility and high impact resistance. Common nylons (PA6 and PA6,6) lie squarely in the middle, offering dry tensile strengths of approximately 60–85 MPa and balanced impact resistance, making them a popular choice for load-bearing, impact-tolerant molded parts.
Wear Resistance
The polyamide family as a whole offers good abrasion resistance. Aromatic polyamides such as Kevlar® combine very high surface hardness and modulus with outstanding wear and cut resistance. Common nylons (PA6 and PA6,6) feature medium hardness but a low coefficient of friction (≈0.2–0.3), giving them excellent abrasion resistance in both dry and lubricated conditions. Long-chain aliphatic polyamides (PA11 and PA12) have softer, more flexible chain segments, resulting in slightly lower hardness and wear resistance than PA6/PA6,6; however, their high toughness allows them to maintain excellent wear performance in low-load, high-impact applications.
Impact Resistance
Impact resistance of polyamides depends largely on chain flexibility, glass transition temperature (Tg), and moisture uptake. Long-chain grades like PA11 and PA12 offer excellent toughness even at low temperatures thanks to their flexible backbones and low Tg. Common nylons (PA6 and PA6,6) provide balanced impact strength, which is further improved by moderate moisture absorption as water acts as a plasticizer, lowering Tg. Aromatic polyamides such as Kevlar®, while extremely strong in tension, are stiffer and less forgiving under transverse or high-strain-rate impacts when used in bulk or composite forms rather than as fibers.
Chemical Resistance
Chemical resistance varies greatly among different polyamides. Common nylons (PA6 and PA6/6) provide good barriers against light hydrocarbons, oils, and most nonpolar solvents, but they are prone to hydrolysis or degradation when exposed to strong acids, strong bases, or oxidizing agents such as nitric acid, bleach, and chlorinated solvents. Long-chain aliphatic polyamides (PA11 and PA12) can resist petroleum, fuels, many organic solvents, and oils, making them a preferred choice for fuel lines, fuel tank components, gears, and sliding parts.
Aromatic polyamides (e.g., Kevlar, Nomex) are highly resistant to virtually all common solvents and fuels. However, elevated temperatures, prolonged immersion, or dynamic wear can make the microvoids and hydrogen-bond network within polyamides more susceptible to chemical ingress, leading to performance degradation.
Water Resistance
At 23 °C and 50 % RH, typical nylons (PA6 and PA6/6) have a moisture absorption rate of about 2-3 %, while long-chain polyamides (PA11 and PA12) absorb only around 0.5-1 %, and aromatic polyamides absorb even less. Moisture uptake slightly plasticizes the material, increasing toughness and reducing the risk of brittle fracture. In optical or concealment applications, hydration also brings the refractive index of nylon closer to that of water, enhancing “invisibility”— the principle behind nylon fishing lines.
However, moisture absorption can also cause dimensional swelling, reduced stiffness and strength, and, in some cases, hydrolysis, ultimately shortening the material’s service life.
Polyamide and Nylon for 3D Printing: Key Materials and Uses
Polyamide and nylon are excellent 3D printing materials because they offer exceptional mechanical strength, thermal stability, and chemical resistance. These polymers are also compatible with a wide range of additive manufacturing processes, recyclable, and support versatile post-processing.Here are some of the most common 3D-printing nylon and polyamide materials and their uses.
1. PA12
One of the most common polyamides in 3D printing, PA12 offers low moisture absorption (~0.5–1.0%), high dimensional accuracy, and excellent resistance to aliphatic hydrocarbons (fuels, oils), many alcohols and dilute alkalis. Additionally, it has better impact resistance and fatigue life compared to other nylon powders.
Processes: MJF, SLS, FDM
Best for: Functional prototypes, housings, snap-fits, gears, chemical-resistant jigs and small end-use parts.
2. PA12 Glass Beads (PA12 GB)
PA12 is reinforced with ~40 wt % glass beads to improve rigidity, dimensional stability, and a fine-textured surface finish.
Process: MJF
Best for: Fixtures, tooling, brackets, jigs, and marine parts.
3. PA12 Glass Fibers (PA12 GF)
Similar to PA12 GB but reinforced with chopped glass fibers (~35–40 wt%), PA12 GF delivers significantly higher stiffness and tensile strength, but typically offers greater warping tendency and more brittle fracture behavior.
Process: SLS
Best for: Load-bearing fixtures, consumer-grade housings, and high-stiffness gears.
4. PA6
FDM-grade nylon is considered one of the strongest and most impact-resistant common FDM materials. It offers excellent wear and heat resistance, but its higher moisture absorption (~2-3 %) and shrinkage make it more prone to warping compared to PA12.
Process: FDM
Best for: Gears, bearings, structural parts, functional prototypes; also easily machined for post-processing.
5. PA11
PA11 is a bio-based nylon, offering superior flexibility, impact resistance, and environmental stability.
Process: MJF
Best for: Connectors, prosthetics, fuel lines, and snap-fits.
6. PA11 Flame Retardant (FR)
Modified PA11 with added flame-retardant fillers like molybdenum trioxide or alumina trihydrate for use in high-heat or electronic environments.
Process: SLS
Best for: Switch housings, pump components, and electrical connectors.
Conclusion
Polyamide is the umbrella term for all polymers with amide linkages, with nylon being the most well-known and widely used synthetic variant. Thanks to their exceptional strength, flexibility, chemical resistance, and design versatility, these materials have become a standout choice in the world of 3D printing. Whether you're working with PA12 for precision housings, PA11 for impact-resistant bio-based parts, or glass-reinforced variants for structural applications, these materials continue to unlock new possibilities across industries—from aerospace and automotive to medical and consumer electronics.
With deep expertise in additive manufacturing, material selection, and production-grade quality control, Chiggo is committed to turning your ideas into high-performance, ready-to-implement solutions. Contact us and take the next step for your project!
FAQ
What does “PA” stand for in PA6 or PA12?
“PA” stands for polyamide. The number indicates the number of carbon atoms in the monomer(s) used—e.g., PA6 comes from caprolactam (6 carbons), PA12 from lauryl lactam (12 carbons).
Is polyamide healthy to wear?
Yes, polyamide is generally considered safe and healthy to wear for most people when used in clothing and textiles. It is widely used in activewear, underwear, hosiery, swimwear, and outerwear due to its lightweight, stretchable, and durable nature.
