Nylon (polyamide, abbreviated PA) is leading engineering plastic. It is a long-chain polymer composed of repeating amide groups (-CO-NH-). It possesses excellent mechanical properties, wear resistance, self-lubrication, and chemical stability. Nylon family is divided into several types based on different molecular structures, each with its unique properties and applications.
This article covers nylon family, reviews 15 categories of commercial PA, starting with PA6/PA66, and discussing other PA processes. Using these two basic nylons as reference points, and PA46 as a reference for high-temperature nylon.
PA6 (polycaprolactam) and PA66 (polyhexamethylene adipamide): These two materials are the most common nylon varieties, accounting for 90% of total nylon production in terms of both capacity and usage. It's worth noting that global total nylon production capacity is only slightly over 10 million tons! Of this, PA6 capacity exceeds 6 million tons, and PA66 exceeds 3 million tons. Among nylon materials, PA6 is the cheapest, followed by PA66.

 

PA6/PA66 raw material granules
So what are differences between PA6 and PA66? What are their key differences?
1. PA6 (Polycaprolactam): Commonly used in applications requiring high toughness, diverse processing methods, and cost-effectiveness, such as: Automotive parts (gears, bearings, fan blades, etc.); Electronic and electrical products (housing, connectors, etc.); Daily necessities (tableware, tool handles, etc.); Textiles and fibers (carpets, ropes, etc.).
2. PA66 (Polyhexamethylene adipamide): More suitable for applications requiring high strength, rigidity, heat resistance, and abrasion resistance, such as: Automotive industry (parts under the hood, brake system components, etc.); Industrial machinery (gears, pulleys, pump components, etc.); Electrical and electronic industries (connectors, switches, etc.); High-performance fibers (airbags, industrial yarns, etc.)
Processing considerations: Both PA6 and PA66 are highly hygroscopic, typically require drying before processing to minimize impact of moisture on final product's performance.

Comparison of PA6/PA66
Summary: Both PA6 and PA66 are conventional nylon varieties. Main difference lies in PA66's superior heat resistance. For example, PA66 is often used in PA fiber-reinforced fuel-retardant systems in automotive engine compartments. Due to its faster crystallization rate, PA66 has relatively better processing performance. For products requiring high processing speeds, such as nylon cable ties, PA66 offers better lubrication. In fasteners requiring high wear resistance, their performance is comparable. Their application areas differ, and specific choice of nylon material depends on actual application requirements, including strength, toughness, heat resistance, wear resistance, and dimensional stability in humid environments. PA6's core competitive advantage lies in its lower cost, with a price per ton 5-8K lower than PA66.
3. PA46 (Polyamide 46, Poly(dibutylene adipamide)): First commercially produced by DSM in Netherlands under its Stanyl brand. We place PA46 in an important position for following reasons: ① It is a pioneer in the field of high-temperature nylon! Industrialization of PA46 sparked a surge in research and application of high-temperature nylon. Following this, new varieties such as PA6T and PA9T emerged and gradually matured in the market. ② Among unreinforced resin materials, PA46 has the most outstanding heat resistance. Its melting point is 295 degrees Celsius without fiber reinforcement, and its heat distortion temperature can reach 280 degrees Celsius in a dry state, even reaching 180 degrees Celsius under a pressure of 1.8 MPa. ③ PA46 has excellent flowability, making it easy to process. ④ Among high-temperature nylons, PA46 exhibits the best wear resistance and good lubrication, primarily used in high-temperature environments such as bearings and gears. However, its price is relatively high.

 

PA46 raw material
Other high-temperature nylons: PA6T, PA9T, PA10T, PA4T, and other materials with PA + number + T, also collectively referred to as PPA, include semi-aromatic nylons and long-chain carbon nylons. These materials possess good heat resistance, and after fiber reinforcement, their performance is comparable to PA46. Some modified PA6T and 9T materials can even achieve heat distortion temperatures exceeding 290 degrees Celsius. However, in terms of resin's inherent heat resistance, PA46 remains the best choice. Among PAXT series of high-temperature nylons, they possess excellent chemical resistance and high dimensional stability, primarily used in electronic components, connectors, and LED packaging. First, let's look at pictures:

4. PA6T (Polyhexamethylene terephthalamide): Produced by companies such as Mitsui Chemicals, DuPont, and Solvay, with a melting point exceeding 320℃, a glass transition temperature of 180℃, and a heat distortion temperature (glass fiber reinforced) of 290℃. Its advantages are: ① Compared to PA46, it has lower water absorption, superior weldability and chemical resistance. ② It has better dimensional stability and high-temperature rigidity than PA46, lower water absorption, is easier to process, but its toughness is generally average. Among high-temperature nylons, PA6T has a very high cost-performance ratio; price of virgin fiber-reinforced products can reach 30,000+ RMB per ton.

 

PA6T raw material
5. PA9T (Polynonyl sebacate): Produced by Kuraray, with a melting point of 306℃. Its advantages are: ① Compared to PA46, it has better high-temperature rigidity. ② It has better dimensional stability than PA46, making it suitable for manufacturing precision connectors where PA46 is unsuitable. It also exhibits good flowability and excellent toughness, making it suitable for industries such as electrical and electronic engineering, automotive, and textiles.

PA6T/9T raw materials

6. PA10T (Polydecyl terephthalamide): Produced by companies such as EMS and Arkema, with a melting point of 316℃. Its advantages are: ① Better high-temperature rigidity compared to PA46. ② Good dimensional stability and flowability. ③ Excellent toughness and extremely high impact strength, performing best among high-temperature nylons, is used in automotive, electronics, LED, and water supply systems.

 

EMS PA10T Modified Resin
7. PA4T (Polybutylene Terephthalamide): With PA6T, PA9T, PA10T, and other materials increasingly competing with PA46, DSM introduced PA4T. Its melting point is as high as 325℃, and after fiber modification, its heat distortion temperature (HDT) can even exceed 300℃. PA4T exhibits excellent mechanical strength and rigidity at both room temperature and high temperatures. It not only inherits some of advantages of PA46 but also combines almost all advantages of aforementioned PA4T materials, regaining its place in the market. However, its price is also very high, often exceeding hundreds of dollars, making it prohibitive for many.
Above is a simple comparison of four high-temperature nylon PA4T and PA46 materials. These four materials excel in high-temperature resistance, mechanical properties, and chemical stability, but their individual properties differ. In practical applications, appropriate material should be selected based on specific application scenario and requirements.

 

High-Temperature Nylon Application 1

 

High-Temperature Nylon Application 2
8. MXD6 Nylon (Polymer of m-phenylenediamine and adipic acid): Nylon MXD6 possesses outstanding gas barrier properties, with overall physical properties superior to PA66 and approaching PPA, while also exhibiting good heat resistance and dimensional stability. Its temperature resistance is slightly lower than PPA system, but it possesses high strength and rigidity. Due to its excellent gas barrier properties, MXD6 nylon is highly favored in packaging and automotive industries, is widely used in many high-temperature products requiring resistance to hydrolysis and gas barriers.
After reviewing conventional and high-temperature nylons, following section introduces low-temperature and tough nylons, such as PA11 and PA12 transparent nylon elastic materials. These materials are characterized by low specific gravity, cold resistance, and impact resistance.
9. PA11 (Polyundecyllactam): Extracted from castor oil, it is a bio-based material, is therefore considered to have higher environmental friendliness and sustainability. PA11 possesses excellent impact strength and a melting point of approximately 200℃. While its heat resistance is lower than PA6, it exhibits superior low-temperature toughness and good chemical stability. It is primarily used in pipes, fuel tanks, packaging materials, and cable sheathing.

 

Arkema PA11 raw material
10. PA12 (Polydodecanoic acid): Prepared through linearization of butadiene, it is a petrochemical-based material with high transparency. PA12 is also known as memory nylon and is a resin material used in eyeglass frames. Its melting point is between 175℃ and 185℃. Improved PA12 has similar thermal properties to PA11, excellent low-temperature impact resistance, good chemical and oil resistance, low hygroscopicity, excellent dimensional stability. It has the lowest shrinkage rate among nylon materials. It is mainly used in fuel systems, hydraulic systems, electronic components, and eyeglasses.

 

EMS Transparent PA12
PA11 and PA12 nylons have similar properties. In practical applications, choice of material usually depends on specific application requirements, including cost, performance requirements (such as temperature range, chemical stability, strength, etc.), ease of processing, environmental factors. PA11's environmentally friendly properties make it a preferred choice in some scenarios; however, in other cases, PA12's cost-effectiveness and good overall performance may be more suitable.
11. PA610 (Polyhexamethylene sebacic acid): This is a translucent or opaque milky white crystalline polymer. Refer to relevant characteristics of PA6. Its melting point is 225℃, and its heat resistance is slightly higher than PA6. Compared with ordinary nylon PA6/PA66, its advantages are: ① Better overall mechanical strength, with outstanding tensile strength, flexural strength, and impact strength. ② Relatively low water absorption and high dimensional stability. It is commonly used to make nylon filaments for brushes and can also be used in electrical components, gears, bearings, and other fields.

 

PA610 Raw Material
12. PA612 (Polyhexamethylene dodecanoate): Compared with ordinary PA6/66, it has following advantages: ① Lower water absorption and density. ② Good dimensional stability, similar to PA610. ③ Higher tensile strength and impact strength, and higher transparency. Nylon 612 has excellent abrasion resistance and chemical resistance, and its temperature resistance is close to that of PA6. It is mainly used to make high-grade toothbrushes and other industrial bristles, and can also be used in oil pipelines, oil-resistant ropes, conveyor belts, bearings, gaskets, and other electronic components.

 

PA612 applied to nylon brushes
13. PA1010 (Nylon 1010): Developed in China in 1958, it is made by extracting decanediamine and sebacic acid from castor oil, followed by condensation. Both of its main monomers are derived from castor seeds, making it a renewable bio-based nylon material with a melting point of 205-210℃. Its heat resistance, strength, and density are slightly lower than PA6. Compared to PA6, PA1010 has advantages in low water absorption, good dimensional stability, excellent toughness, and outstanding wear resistance, exhibiting similar properties and applications to PA612 and PA610. However, its widespread application faces significant challenges due to its higher price and lower production capacity.
14. PA1212 (Nylon 1212): This is a long-chain carbon nylon with a melting point typically between 178-180℃ and a long-term operating temperature generally around 140-150℃, overlapping with properties of PA12. Compared to PA6 and PA66, PA1212 features low water absorption, good dimensional stability, relatively good wear resistance, making it suitable for components requiring high precision and wear resistance. It also possesses good flexibility and low-temperature toughness, exhibiting excellent low-temperature performance. However, like PA12, its price is also relatively high.
15. PA56 (Polyamide 56): A new type of bio-based nylon, PA11 mentioned earlier is also a bio-based nylon. PA56 is polymerized from bio-based pentanediamine and petroleum-based adipic acid, with a melting point of approximately 260℃. Its strength, softness, moisture absorption, resilience, and low-temperature resistance are similar to PA66. Its advantages lie in its more environmentally friendly nature as a bio-based material, slightly better flexibility than PA66, better spun feel and flexibility. However, its disadvantage is that bio-based nylons are generally more expensive. Although PA56's performance is close to PA66, its price is twice that of PA66, making its widespread application extremely difficult.

 

Bio-based PA56 raw material
16. PA Nylon Elastomer: Also known as thermoplastic polyamide elastomers (TPAE), it is obtained by modifying nylons such as PA11 and PA12. It is a block copolymer composed of polyamide hard segments and aliphatic polyester or polyether soft segments. This material combines strength of nylon with flexibility of elastomers. Its performance can be understood as a combination of PA11/12 and TPU, exhibiting excellent properties in high tensile strength, low-temperature resistance, elastic recovery, abrasion resistance, chemical resistance. It belongs to high-end product category in plastic elastomer field. Major manufacturers include Arkema Pebax and Evonik TPAE, its products are showing a growing trend in high-end sports shoes and sports equipment.

 

TPAE Nylon Elastomer

 

Professional running shoes such as Xtep Shock Absorber Pro use nylon elastomers