20 Vital Differences between Nylon 6 and Nylon 66

Nylon is an important synthetic material for industrial purpose. It has many variants like Nylon 66, Nylon 6, Nylon 5,10, Nylon 6,12, Nylon 11 etc. What to choose, a little bit confusing right? Find out the differences between Nylon 6 and Nylon 66 right below!!

You will get to know about nylon 6, nylon 66 along with their application area in brief in this article.

For High mechanical damping ability, good sliding properties, excellent wear resistance, good electrical insulating properties, and good resistance to high energy radiation Nylon becomes incredibly popular for different industrial purposes. 

A quick glance on the difference between Nylon 6 and Nylon 66

Basically main difference between Nylon 6 and Nylon 66 is in their chemical structure. Both of them are popular for their durability and light weight properties. Nylon 6 is formed from Caprolactum by open ring polymerization having lower melting point. 

Whereas, Nylon 66 is formed from Hexa methylene di-ammine and Adipic acid by condensation polymerization reaction having a higher melting point. The latter property makes it suitable for high performance industrial use.

Nylon 6 in brief!

Nylon 6 results from open ring polymerization of only one monomer caprolactam. It is called Nylon 6 because of containg 6 carbon atioms in it. This is made from the type ………AAAAAA……… or (A)n, where n=200. 

It provides good insulation and damping properties. Toughness, stiffness and hardness all of them are the characteristics of nylon 6. It has lustrous finish along with it exhibits good dye affinity.

Uses of Nylon 6

  • Hosiery
  • Industrial yarn
  • Upholstery
  • Heavy duty fabric
  • Toothbrush fiber

What is Nylon 66?

Nylon 66 is a polymer formed from condensation polymerization of Hexa methylene di-ammine and adipic acid. It contains 12 carbon atoms that comes from its two monomers. As each of them has 6 carbon atoms in their structure.


Uses of Nylon 66

Its micro denier form is mostly used in apparel such as industrial workwear. Heavy denier is used in-

  • Tire cord
  • Automotive air bags
  • Parachutes
  • Carpets

Properties of Nylon 6 and Nylon 66

Let’s have a general discussion on the properties of Nylon 6 and Nylon 66……

The numbers of repeat units along the polymer chains of nylon 6.6 and nylon 6 are about 65 and 130, respectively. Both types of nylon contain weakly basic amino and weakly acidic carboxylic acid end groups.

Nylon 6 and nylon 6.6 are strong fibers with moderate elasticity, even after drawing. Nylon 6 has a somewhat lower elastic modulus and better elastic recovery than nylon 6.6 and therefore gives more flexible fabrics of softer handle.

Both nylons are available in high tenacity variations for industrial uses. In fact, the mechanical properties can be varied considerably by changes in the polymerization and drawing conditions.

Heat setting of nylon materials may be carried out under dry conditions in hot air at 190 °C for nylon 6, or 205 °C for nylon 6.6. Alternatively, setting is achieved in steam at 120 or 135 °C, respectively.

At higher temperature like 180°C, Nylon 66 shows better heat age strength of 11.5 kg whereas Nylon 6 breaks down at 2.5 kg. The fibers of Nylon 66 are 33% more resistant to abrasion than Nylon 6. They can withstand 60,000 cycles while Nylon 6 can withstand 40,000 cycles at the same conditions. 

Low creep, more crystalinity makes it slightly stiffer and better equipped, again its good stretch recovery, and higher abrasion resistance makes Nylon 66 more suitable for industrial use. 

As Nylon 6 is a bit lustrous than Nylon 66, it is suitable for radiator grilles, stadium seats or firearm components where we need an attractive lustrous finish. 

Differences between Nylon 6 and Nylon 66 in detail!!

TopicsNylon 6Nylon 66
No. of carbon atoms in structureNo of carbon atoms are 6. It represents that it has 6 carbon atoms in the backbone of its chainNylon 66 has two 6 numbers. It indicates the number of carbons in the acid and ammine residues. So it has 12 carbon atoms.
Requirement of monomerOnly one monomer is requiredTwo monomers are required
Monomer usedCaprolactamHexa-mythelene di-amine and Adipic acid
Polymerization techniqueIt is known as poly-caprolactam which is formed by open ring polymerizationThis polyamide is formed by condensation polymerization
Melting pointLower (215-220°C)Higher (250-265°C)
Water absorption rateHigh Low
Chemical resistance to acidPoorGood
Heat deflection temperatureLowHigh
Moisture regain4-4.5%4-4.5%
Chemical namePoly (6-aminocaproic acid)Poly [Immino (1,6-dioxohexamythelene)immio hexamythelene]
Density1.15 g/ml1.2 g/ml
Degree of polymerization20060-80
RecyclabilityMore recyclable than nylon 66Less recyclable than nylon 6
Tensile strength6.2 × 104 kPa8.3 × 104 kPa
Glass transition temperature (Tg)Dry – 60Tg reduces with the increase in moisture contentDry – 70
Molecular mobilityHighLow
Color fastnessLess than nylon 66Better
Dye affinityGreat dye affinityShows less dye affinity than nylon 6
Temperature resistanceLess than nylon 66Better
Stain clean-abilityLowHigh
Mold shrinkageLowMore
Heat setting at hot air190°C205°C
Internal structureLess compactMore compact
Heat setting at steam120°C135°C
ApplicationRadiator grilles, stadium seats or firearm componentsFriction bearings, battery modules, luggage and conveyor belts
Elastic modulusLowerHigher
Elastic recoveryBetterLower than nylon 6
LusterMore lustrous surfaceLess lustrous surface

To Sum Up!!

So, what should you choose for your specific purpose? You will clearly get your answer if you understand the differences between nylon 6 and nylon 66. 

Check out our another article on Nylon- not the material only for fiber!!

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