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Polyamide (PA) or Nylon: Complete Guide (PA6, PA66, PA11, PA12…)

Polyamide (PA) or Nylon: Complete Guide (PA6, PA66, PA11, PA12…)

Exhibiting high temperature and electrical resistances, polyamides (nylon) are considered as high performance plastics and are widely used in automotive & transportation markets, consumer goods and electrical and electronics applications among others.

Learn more about this interesting class of plastics along with the main applications and benefits of some common polyamides: PA11, PA12, PA46, PA6, PA66 and PPA (polyphthalamides). Explore more about their key properties like mechanical, thermal, electrical, etc., conditions to process this polymer and understand what makes Polyamides an ideal choice in high-end engineering applications.

What is Polyamide (Nylon)?


Polyamides or Nylon is the major engineering and high performance thermoplastics class because of its good balance of properties. Polyamides contain repeating amide linkages i.e. –CO-NH–. It is formed by condensing identical units, copolymers for different units.

Polyamides (or Nylon) are made from polycondensation of diacid with a diamine or by ring-opening polymerization of lactams with 6, 11 or 12 carbon atoms.

  • The monomers may be aliphatic, semi-aromatic or aromatic (aramids)
  • They may be amorphous, semi-crystalline and of greater or lesser crystallinity

Polyamide Monomer(s)
Polyamide 6 Caprolactum
Polyamide 12 Laurolactam
Polyamide 66 Hexamethylene Diamine/ Adipic Acid
Polyamide 69 Hexamethylene Diamine/ Azelaic Acid
Polyamide 6-10 Hexamethylene Diamine/ 1,12-Dodecanedioic Acid
Polyamide 6-12 Hexamethylene Diamine/ Sebacic Acid
Polyamide 46 1,4-Diaminobutane/ Adipic Acid
Polyamide 1212 1,12-Dodecanediamine/ 1,12-Dodecanedioic Acid

Aliphtaic Polyamide Polymers and Their Monomers


Aromatic polyamides (or Aramids) are obtained from polycondensation of terephthalic acid with diamines. PA 6-3-T is one of the common examples of aromatic polyamide which is an amorphous transparent in nature. The materials can be processed at 280-300°C. Aramids are expensive, have better dimensional stability, flame and heat resistance and higher strength as compared to aliphatic polyamides.

Polyamides exhibit high temperature and electrical resistance. Thanks to their crystalline structure, they also show excellent chemical resistance. They have very good mechanical and barrier properties. In addition, these materials can easily be flame retarded. Polyamides became the first truly synthetic fiber to be commercialized.

Continue reading or click below to explore more about:

Polyamides are widely used in markets such as:


When reinforced with glass fibers (short or long), their stiffness can compete with metals, this is why Polyamides are often considered in metal replacement projects.


The History


Nylon was discovered by Wallace Hume Carothers, a chemist hired in 1928 by DuPont de Nemours to lead an extensive research program on the design of original polymeric materials. It 1935, he developed the formula known as PA 66:

Polyamide66 Structure

Different Types of Polyamides


Among this large polymer family, several types of polyamides are particularly suited for given applications. The best choice depends on the set of performances needed as well as the economical constraints.

  • The two most widely used PA are by far PA66 and PA6. They are often extruded to manufacture fibers (textile industry) or films (packaging), or injected
  • The Polyamides with the highest performances are PPA and PA46, which are good candidates for metal replacement developments or very specific applications exposed to extreme conditions
  • Bio-based PA are also available. For instance, PA11 is based on castor-oil chemistry

However, all Polyamides tend to absorb moisture due to the amide chemical group. Moisture acts as a plasticizer on Polyamides thus reducing tensile modulus and increasing impact resistance & flexibility.

Moisture uptake also has a huge influence on dimensional variations; this must be taken into account when designing parts.

Some of the major polyamide suppliers include: RTP Company, SABIC, BASF, PolyOne, DuPont, Lehmann & Voss…

» View all PA commercial grades and suppliers in Omnexus Plastics Database

This plastic database is available to all, free of charge. You can filter down your options by property (mechanical, electrical…), applications, conversion mode and many more dimensions.


Polyamide 6 (or Nylon 6) and Polyamide 66/ PA 66


Polyamide 6/ PA6 is also known as Nylon 6 or polycaprolactam. It is one of the most extensively used polyamides globally. It is synthesized by ring-opening polymerization of caprolactam. Melting point of Polyamide 6 is 223°C.

While, Polyamide 66/PA66/Nylon 66 is one of the most popular engineering thermoplastics and is majorly used as a replacement to metal in various applications. Nylon 66 is synthesized by polycondensation of hexamethylenediamine and adipic acid (two monomers each containing 6 carbon atoms). Melting point of Polyamide 66 is 255°C.

 Polyamide 6  Polyamide 66

Molecular Structures of Polyamide 6 and Polyamide 66


Main properties of PA6 and PA 66 include:

  • High strength and stiffness at high temperature
  • Good impact strength, even at low temperature
  • Very good flow for easy processing
  • Good abrasion and wear resistance
  • Excellent fuel and oil resistance
  • Good fatigue resistance
  • PA 6 has excellent surface appearance and better processability than PA66 (due to its very low viscosity)
  • Good electrical insulating properties
  • High water absorption and water equilibrium content limits the usage
  • Low dimensional stability
  • Attacked by strong mineral acids and absorbs polar solvents
  • Proper drying before processing is needed

Both Polyamide 6 (PA6) and Polyamide 66 (PA66) are widely used in many different markets and applications due to their excellent performance/ cost ratios.

PA6 & PA66 are by far the most used Polyamides globally

Although, they exhibit similar properties, slight differences do remain. PA6 has a slightly lower temperature resistance versus PA66 and is also slightly less expansive.

Polyamide 6 vs. Polyamide 66 

While, as compared to PA6, the PA66 has:

  • Slightly less moisture absorption ability
  • Higher modulus
  • Better wear resistance
  • Better short term heat resistance

» Compare More Properties of PA6 and PA66

Popular Applications of PA6 & PA66


Plastic parts are made with these polyamides are used in various industries like:

  • Transportation
  • Electronics & Electrical
  • Consumer goods
  • Building & Construction
  • Packaging

PA66 is used when PA6 reaches its limit temperature or when the hydrolytic stability of PA6 is not sufficient anymore. It provides good surface appearance and weld strength leading to burst pressure resistance.

The molding cycles are quick, providing an economical interest. Polyamide 6 and Polyamide 66 answer the requirements of numerous applications in the varied markets.

Application Description

PA6, PA66 Replace Metal in Automotive Applications

PA6 and 66 in automotive applications
Thanks to their good processability, PA6 and PA66 are often used as an alternative to metal in automotive under the hood parts where design flexibility as well as temperature and chemical resistance are critical.

They ultimately contribute to weight savings, which offers CO2 emissions reduction opportunities. PA66's mechanical properties (stiffness, creep resistance, etc.) help improve safety and comfort in cars.

»   View Commercial PA6 Grades for Automotive

Electrical & Electronics Applications - Flame Retarded PA Works Well!

PA6 and 66 in electrical and electronics applications

In the electrical and electronic applications, Polyamides 6 and 66 grades are good candidates where specific tests (GWIT, UL94) need to be passed. PA6 & PA66 can easily be flame retarded and halogenated & non-halogenated FR solutions are commercially available.

»   See Flame Retardant PA66 Grades Available Today!

Moreover, they also bring solutions in this industry where miniaturization reinforces the needs for high temperature resistance and thin designs (possible due to easy processability).

Good Surface Aspect in Consumer Applications

PA6 and 66 in Agricultural films applications

Polyamide 66 offers solutions for durable Consumer and Industrial Goods, thanks to its easy moldability, colorability, good surface aspect and excellent mechanical resistance.

PA66 is an excellent material when complex designs are needed, and it is also a cost efficient solution.

Food Packaging with PA6 & PA66

PA6 and 66 in food packaging applications

PA6 and PA66 offer very high puncture resistance, barrier resistance to oxygen, carbon dioxide and aromas, transparency, etc. All these properties make PA6, PA66 ideal for use in food packaging (mono or multi-layer).

»   Get Access to PA6 Grades Available for Packaging Applications

In the medical field, PA6 is fabricated into tough, puncture-resistant packages for medical blister packs.

PA Replaces PP in Furniture Applications

PA6 and 66 in furniture applications
For the furniture market, PA6, PA66 is used to manufacture stadium seats thanks to their brilliant surface quality, excellent resistance to dirt and aging and offering a great alternative to polypropylene.

Sports & Leisure

PA6 and 66 in sports applications
The exceptional fatigue properties and high impact and mechanical strength of PA6 and PA66 contribute in sports applications where they are used to manufacture Ski bindings.



Other applications include agricultural films, liquids packaging, protective packaging, medical, etc.


Polyamide 11 or PA 11


Check Out Several Bio-based
Polyamide Grades Now!
Biobased Polyamides
Polyamide 11/ PA11/ Nylon 11 is a rare bio-based engineering plastic that is derived from renewable resources (castor plants) and produced by polymerization of 11-amino undecanoic acid.

Rilsan® - or polyamide 11 - is one of the first biosourced polymers. Melting point of Polyamide 11 is 190°C.

Several properties of PA11 are similar to Polyamide 12 (PA12) but comparatively offers superior thermal and U.V resistance, low water absorption and lower environmental impact. It displays good impact strength and dimensional stability.

 Strengths  Limitations 
 The lowest water absorption of all commercially      available polyamides  High cost relative to other polyamides
 Outstanding impact strength, even at                        temperatures well below the freezing point  Lower stiffness and heat resistance than other        polyamides
 Resistant to chemicals, particularly against              greases, fuels, common solvents and salt solutions
 Poor resistance to boiling water and UV
 Outstanding resistance to stress cracking, aging      and abrasions
 Proper drying before processing is needed
 Low coefficient of friction  Attacked by strong mineral acids and acetic acid,    and are dissolved by phenols
 Noise and vibration damping properties  Electrical properties highly depend on moisture      content
 Fatigue resistant under high frequency                cyclical loading condition
 Ability to accept high loading of fillers
 Highly resistant to ionization radiation


Polyamide 12 (PA 12)


Polyamide 12/PA 12/Nylon 12 is a semi-crystalline thermoplastic which shows performance similar to Polyamide 11. It can be derived from both petroleum and renewable sources.

It is an expensive polymer as compared to other polyamides.

Polyamide12

Molecular Structure of Polyamide 12

Key Properties of PA 12


  • Possesses lower impact resistance but shows good resistance to abrasions and UV
  • Has a low water absorbency than PA 6, PA66 and all other types of polyamides
  • Displays good dimensional stability and reasonable electrical properties
  • Is ideal for applications where safety, durability or reliability over time is critical.
  • Transparent grades are also available, allowing high flexibility in terms of design and creation

 Strengths  Limitations 
 Lowest water absorption of all commercially            available polyamides  Expensive than other polyamides
 Outstanding impact strength, even at very low        temperatures  Lower stiffness and heat resistance than other        polyamides
 Good chemical resistance, in particularly against      greases, fuels, common solvents and salt solutions
 Low UV resistance
 Outstanding resistance to stress cracking
 Proper drying before processing is needed
 Excellent abrasion resistance  Electrical properties highly depend on moisture      content
 Low coefficient of friction
 Noise and vibration damping properties
 Good fatigue resistance under high frequency          cyclical loading condition

The superior properties of PA11/ Nylon 11 and PA12/Nylon 12 make them useful in applications like:

PA11 applications

  • Automomtive - Due to its aigh flexibility and tensile strength, PA11/ Nylon 11 is used to manufacture trailer brake hoses, fuel lines, etc. for the automotive/transportation market.

  • Sports and Leisure - PA11/ Nylon 11 is used to manufacture bicycle derailleur, sport shoes (football shoe soles), etc., thanks to its good grease and abrasion resistance and low coefficient of friction

  • In engineering/ manufacturing applications like protective layer of water pipes, air and spray-painting hoses, PA11/ Nylon 11 is widely used

  • Other applications include: Healthcare/Medical- Catheters; Appliances- Protective coating of dishwasher racks; Electrical markets- Coatings for termit resistant wires; Household products/Consumer goods- Hammer heads etc.

There are also some specialty PA 11 grades developed for 3D printing offering benefits such as:

  1. Good control of particle size
  2. Good thermal properties, 
  3. Very good processability in laser sintering machines


In contrast to traditional bio-based polymers, PA11 and bio-sourced PA12 demonstrate the features shown in the image below.

PA11 PA12 Features


  • Even if they do not over-perform in terms of temperature resistance (HDT, peak temperature...), they exhibit outstanding retention of performance over time
  • Their remarkable long lasting performance allows for their use in a wide range of conditions (temperature, pressure, chemical...)
  • PA11 and PA12 are particularly suitable when reliability over time is needed

  » Check Out their properties and processing conditions in detail

Polyamide 6-10


Polyamide 6-10 (PA 6-10) is a semi-crystalline polyamide. PA 6-10 is produced by the polymerization of hexamethylene diamine with a dibasic acid i.e sebacic acid this this case. Melting point of PA6-10 is 223°C.

Main Properties of Polyamide 6-10 include:

  • Exhibits lower water absorption when compared to PA6 or PA66
  • Has lower brittle temperature than PA6 or PA 66
  • Has good abrasion resistance and chemical resistance
  • Possesses lower strength and stiffness unlike PA 66
  • Drying before processing of PA 6-10 is highly recommended
  • PA 6-10 is much stronger than PA 11, PA 12 or PA 6-12
  • Low coefficient of friction
  • Good electrical insulating properties
  • High resistance against high energy radiation (gamma and X-rays)

» Click Here to Review PA 6-10 Properties (Mechanical, Electrical, Physical...) Along with Their Values!

Few limitations of PA 6-10 include: high mold shrinkage, high cost compared to other low water absorption polyamides and it is attacked by strong mineral acids and absorbs polar solvents.

Thanks to its good insulating properties, heat resistance and flame retardancy, Polyamide 6-10 is used to manufacture insulators for the electrical market.


Polyamide 46 (PA46)/ Nylon 46


Polyamide 46 is manufactured by polycondensation of adipic acid and 1,4-diaminobutane. Diaminobutane is synthesized from acrylonitrile and HCN. Melting point of Polyamide 46 is 295°C.

Polyamide 46 (PA46) is a high temperature polyamide providing unmatched performances across a broad range of applications, such as:

  • Automotive - It is used to manufacture several automotive/ transportation parts like chain tensioners, engine covers, oil filter parts, signaling lamp bases, thrust washers, gear-shift forks, speedometer gear wheels, fuel distributors, etc.
  • E&E, - It is used to manufacture surface-mount devices, connectors, end laminates in electric motors, brush holders in electric motors, etc. for the electronics market
  • Industrial goods, , consumer goods, safety controls in appliances such as kettles and ovens
  • And many more…

PA46 is the polyamide exhibiting the highest temperature resistance. Its HDT at 1.8MPA is 160°C, and 285°C when filled with 30% of glass fibers. PA 46's mechanical resistance is superior to PA66's. Its fatigue resistance is 50 times that of PA66.

Key Properties of PA46


Excellent thermal performance with Polyamide46
PA46 mechanical properties
Excellent wear resistance with PA46
Chemical resistance with PA46
Excellent electrical resistance with PA46
Good Thermal
Performances
Good Mechanical
Properties

Particularly at high
temperatures
Excellent Wear
Resistance
Excellent Chemical
Resistance
Excellent Electrical
Resistance

  • PA46 is often used to replace metal in demanding, high temperature applications.
  • Due to PA46's excellent mar and wear resistance, it is used in gear applications where it offers a combination of mechanical and constant performances at high temperature, excellent tribological behavior and high fatigue resistance.
  • PA46 can be metallized. It is also possible to color a part made of PA46, however the color resistance will depend on the behavior of the pigments at high temperature.
  • Due to its high fluidity, PA46 is a good solution for complex shapes and parts with thin walls.

 Strengths  Limitations 
 Outstanding stiffness, fatigue and creep  resistance, up to 220°C  High water absorption and water equilibrium  content
 Excellent abrasion and friction behavior
 High temperature processing, due to its high  melting point
 Very good flow for easy processing
 Low dimensional stability
 Very low injection cycle time, due to its high  crystallization rate
 Attacked by strong mineral acids and absorbs  polar solvents
 Excellent fuel and oil resistance
 Proper drying before processing is needed
 Good impact strength
 Darkens with exposure to high heat
 Very low flash
 Good electrical insulating properties
 High resistance against high energy radiation  (gamma and X-rays)

» View PA 46 Properties in Detail Before Making the Right Selection!

Latest High Heat Polymer Resins & Applications Advances (2017 Edition)


Polyphthalamide (PPA)


Polyphthalamides are formed by reaction of aromatic acids with aliphatic diamines and produced using a combination of terephthalic acid and isophthalic acids.

Polyphthalamide also known as PPA is a high heat resistance semi-aromatic polyamide.

With its low moisture pick up, PPA demonstrates excellent retention of performances in a wide range of conditions, including:

  • Chemical environment,
  • Extreme temperature requirements

They also demonstrate excellent stiffness and creep resistance...Learn More About PPA Properties

Thanks to their aromatic structure, Polyphthalamides (PPA) offer several superior performances compared to other polyamides, such as:

  • Improved dimensional stability
  • Improved solvent and hydrolysis resistance
  • Better high temperature mechanical property retention

Mis-fuel inhibitor with PPA
Mis-fuel inhibitor
Charge-Air-Cooler end tanks with PPA
Charge-Air-Cooler end tanks

Polyphthalamide are stronger, less moisture sensitive and possess better thermal properties compared to the aliphatic polyamides such as PA66. However, they are less ductile in comparison although impact grades are available.

Polyphthalamide resin features an excellent stiffness-to-cost ratio and a high strength-to-weight ratio, both of which are superior relative to PBT, PPS, PEI, PET and PA 66. And, its thermal performance is exceeded only by polyetheretherketone (PEEK) and some Liquid Crystal Polymers.

 Strengths  Limitations 
 Very high stiffness and strength, compared to  PA66  Requires high processing temperatures (up to  350°C)
 Good heat resistance
 Requires good drying equipment
 Low water absorption
 Not inherently flame retardant
 Very low creep tendency
 Attacked by powerful oxidants, mineral acids,  acetic acid and formic acid
 Good chemical resistance
 Good fatigue resistance
 Good dimensional stability

PPA Grades deliver cost effective solutions, compared to PA46, in many applications such as:

  • Many types of automotive components including sensors and solenoids, halogen lamp sockets and fog lamp assemblies, motor end caps and housings, fuel system components (flanges, fuel rails, fuel line connectors), anti-lock braking system components, cooling and heating system components (thermostat housings, oil filter housings, turbo charger air coolers).

    Polyphthalamide is also used in a range of high temperature applications in the automotive electronics sector such as lamp sockets, electronics connectors, high-temperature switches, and sensors.

  • Electrical and Electronics Market - Main applications include LEDs and other optoelectronic devices, SMT electronic components, capacitor and chip carriers, heat sinks and switches. PPA resin is also surface mount compatible and, with its outstanding strength and ability to be injection molded with fast cycle times, is an excellent fit for applications such as cellular phone connectors.

    Finally, fully automated wafer loading systems use cassettes molded from Polyphthalamide resin to transport silicon wafers into process equipment where heat and chemical resistance are required.

  • Other markets benefiting from PPA resin benefits are: optics (optical fiber components), hardware and plumbing, sporting goods, oil field parts, and military applications.

They can also be a good alternative to metal when filled with glass fibers.


Nylon Versus Polyester: Main Differences


Both nylon and polyester are thermoplastic materials but polyester compounds can be thermosets as well. They both are majorly synthetic in nature.

Their main differences include:

Nylon Polyester
Type Thermoplastic Polymers commonly known as Polyamides Thermoplastic or Thermoset
History First Nylon was produced by Wallace Carothers in 1935 First polyester fiber called Terylene created in 1941
Production Nylon is formed by the condensation of copolymers. Equal parts of dicarboxylic acid and diamine are used for the process. There are peptide bonds on the ends of the monomers Synthetic polyesters are made up of dimethyl ester dimethyl terephthalate (DMT) or the purified terephthalic acid (PTA).
Uses Used in apparel, flooring, molded parts for cars, electrical equipment, etc., packaging films Used to manufacture a variety of products, including textiles, belts, furniture, insulation, padding, tarps and glossy finishes for hardwoods
Touch A silky, smooth touch Fiber feeling
Durability Exceptionally strong, abrasion resistant, resistant to damage from oil and many chemicals Strong, resistant to stretching and shrinking, resistant to most chemicals, crisp and resilient wet or dry, abrasion resistant
Stretchability Low moisture absorbency allows fabric to stretch No water absorbance, faster drying, wrinkle resistant


How to Process Polyamide?


Polyamides can be processed by all common melt processing techniques. Though low melt viscosity polyamides needs particular attention. Sure to their semi-crystalline nature processing must be controlled to optimize the physical properties of the end component.

Thanks to their crystalline structure Polyamides are easy to inject, showing high fluidity. This is particularly appreciated when injecting thin-walled parts.

Due to their moisture sensitivity, Polyamides require efficient drying process. Insufficient drying will lead to splays and unaesthetic marks on part surfaces, as well as lower mechanical properties due to material degradation (heat and water lead to oxidation).

Injection Molding

All polyamide materials can be processed by injection molding.
  • If the moisture content is >0.2%, drying in a hot air oven at 80 C (176 F) for 16 hours is recommended. If the material has been exposed to air for more than 8 hours, vacuum drying at 105°C (221°F) for more than 8 hours is recommended. 
  • Mold Temperature: 60-80°C
  • Melt Temperature: 230 - 280°C; 250 - 300°C for reinforced grades
  • Material Injection Pressure: 75 - 125 MPa (depends on material and product design)


High Temperature Plastics: How to Well Control Melt Temperature


Extrusion

  • Maximum allowable moisture content 0.1%
  • Melt Temperature: 230-290°C
  • The compression ratio: <4.0
  • The L/D Ratio: 25-30 (Barrier Screw or Polyolefin Screw with equal feed, transition and metering section)

Polyamides are also widely used to produce 3D parts printed by selective laser sintering (SLS). 3D printing technique used to produce plastic prototypes offer several benefits such as production of complex parts, individual designs, cost-effective in small scale production.

» Check Out All Polyamide Grades Available for 3D Printing



Watch Today! An Interesting Video on Tips and Tricks for Nylon 3D Printing by 3D Systems

Polyamide Recycling and Toxicity


The key use of polyamide 6 is in carpets and a recycling process for this was initially devised by DuPont in 1944 although recycling a dirty carpet is still a challenge.

Polyamide polymer can be chemically recycled or de-polymerized

De-polymerization method involves breaking down the long polymer chains into monomers which can be then re-polymerized which possibly converts the waste into products having a quality equivalent to that of the “virgin” polymer.

Polyamide 6 can be depolymerized to its monomer – caprolactam, byacidolysis, hydrolysis, aminolysis or catalyzed-de-polymerization in vaccum. Companies recycling polyamide 6 and 6.6 by depolymerization includes: DuPont, AlliedSignal, BASF and Novalis Fibers.

Other recycling method include recovery of polymer components without reaching the monomer level. Includes multiples extraction and separation steps, Mechanical recycling and Thermal recycling or Energy generator.

Polyamide Recycling from Carpets
(Source: AlliedSignal/NCSU)



Polymer Properties Compare PA6 & PA66 Properties Polymer Properties Explore PA 6-10 Properties in Detail
Polymer PropertiesSee PA46 Properties & Their Values Polymer Properties Check Out Properties of PPA
Polymer PropertiesSee PA11 & PA 12 Properties in Detail Polymer Application Check Latest News About Polyamides

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