Aug. 26, 2024
Nylon 6 and Nylon 66 are both commonly used synthetic polymers known as polyamides.
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The numbers represent the amount and variant of the carbon atoms in the chemical structure from which they are formed.
For example:
Nylon 6 is created from caprolactam, which consists of 6 carbon atoms, while nylon 66 is produced from adipic acid, which has 6, and hexamethylene diamine, which also has 6.
Most nylons, including 6 and 66 are semi-crystalline and possess good strength and durability and are ideal for demanding projects.
Nylon 66 was discovered at the Du Pont Company in the s, giving the world the first synthetic fibre.
This was quickly introduced into the commercial arena and became the backbone of the new synthetic fibre industry.
Following this in , nylon 6 as it was to be known, was created in Germany by Paul Schlack.
Both fibres have become highly important in today&#;s fibre trade, and their uses and applications continue to be discovered and improved.
The properties and variations within commodity plastics, and in this case nylons, are not as stark as they would be with, say, steels.
Having said that, when we begin to subtly alter the underlying structure and its fillers and additives, many more commodity and specialist grades are achievable creating a wider range of properties and as a result, a broader scope of application.
As polyamides, while having their own defined benefits, they do also share many core performance characteristics.
So, while maintaining these core property values, they do still provide different attributes.
Nylon 6
Nylon 66
Resistance to Hydrocarbons
Mould Shrinkage*
Higher Shrinkage
Impact Resistance
Easiness To Colour
Less
Eye-Catching
Water Absorption Speed
Recyclability Potential
Molecular Mobility
Elastic Recovery
Dye Affinity
Crystalline
Less
Heat Deflection Temperature
Melting Point
(215° - 220°c)
(250° - 265°c)
Chemical Acid Resistance
Rigidity
Colour-Fastness
Temperature Resistance
Ability to clean
Elastic Modulus
Internal Structure
Less compact
Polymerization Formation
Open Ring
Moisture Regain
4 - 4.5%
4 - 4.5%
Monomer Requirements
2
Density
1.2 g/ml
Degree of Polymerization
200
Most notable of these distinctions is mould shrinkage.
Nylon 6's lower mould shrinkage gives more assurity of accurate dimensions for all manufactured goods.
Whereas the greater mould shrinkage of Nylon 66 means that when it is exposed to cooler air in solidification, its material shape will have more susceptibility to alteration after processing, which must be factored in.
Other highly relevant differences are their relative water absorption rate and heat deflection values.
Nylon 6 has higher water absorption and lower heat deflection temperature, and as such is less suited to applications where high-temperature water is present.
Nylons take their place among the engineering plastics due to a valuable combination of strength, rigidity and toughness.
Applications vary from gears, door handles, bearings, brushes, sprockets, power tool housing and even bicycle wheels, to name just a few.
When considering using nylon for a project, a vital factor is that nylons do absorb moisture, which can alter its properties and thus, its dimensional stability.
To offset this, a form of reinforcement, often glass, can be introduced to create an incredibly strong and impact resistant material.
Nylon 6 excels in damper conditions, having better impact strength and flex fatigue than nylon 66.
It can also be processed at a lower temperature and is less crystalline in structure, meaning mould shrinkage is reduced.
It is also available in transparent grades.
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However, Nylon 6 does have the highest level of absorption of any nylon, showing dimensional instability and fluctuating mechanical and electrical performance, some of which can be countered by alloying with low-density polyethylene.
As a result of all of this, Nylon 6 tends to be used for components requiring higher impact strength than nylon 66, but where higher yield strength is not a prerequisite.
Nylon 6 can be used in a host of varying applications, including:
Nylon 66 is the most commonly used of all the nylon groups:
Without fillers, it retains strength across the widest range of temperatures and the highest level of moisture exposure than any other nylon.
It also exhibits good abrasion resistance and the lowest permeability to mineral oils, gas and fluorocarbon refrigerants.
Nylon 66 is also reported to have better chemical resistance to saturated calcium chloride, and many reports suggest that 6/6 has better weathering properties too.
Nylon 66 is also a popular material for electrical components, and as a replacement for metals in die-cast hand tool bodies.
Another significant advantage is its Heat Deflection Temperature (HDT) compared to Nylon 6. Therefore, Nylon 66 is clearly a great choice in wet conditions, but not so much when dry.
Nylon 66 has high moisture absorption, low impact strength, and poor ductility. It is also the most susceptible to UV penetration and oxidative degradation.
Nylon 66 is often found in:
It is important to note that both of these nylon groups have a lower resistance to weak acids than 6/10, 6/11 and 6/12. And, that ALL nylons will substantially degrade when exposed to fermented 15% ethanol gas.
Processing method, aesthetics, and mechanical characteristics must all be taken into account when assessing the right nylon for a project.
Nylon 6 for example, is a great choice if a lightweight Engineering Plastic is a prerequisite. It has good insulation properties, and damping values, as well as good toughness, rigidity and hardness.
Nylon 6 is also the standout choice if resistance to high impact and internal stresses are required and if aesthetics are a factor. Its lustrous look and ease of colouring make it the more attractive option on the eye.
Nylon 6 is also an ideal choice for applications in the automotive industry, as well as military and industrial components, commonly used for firearms, engines, gears and so on.
It is important to note, however, that Nylon 6 is not the right option where the high water temperature is a factor due to its high water absorption and lower heat deflection rate.
Here, Nylon 66 would be a better choice.
In contrast, Nylon 66 should be utilized where a high performing engineering plastic is needed in higher temperature environments.
Its greater rigidity and good tensile modulus make it a fantastic material for applications that need to last longer over repeated performance, such as friction bearings, tire ropes or radiator caps.
There are also many more nylons to consider that each has different performance advantages and property values, so it can be seen that within the plethora of nylons, selecting the right one is often a case of making a favourable compromise.
For this reason, we advise seeking expert advice before putting pen to paper on any nylon-based project.
Looking for more information on Nylon 6 vs 66? Contact your local centre and we'd be pleased to help you further!
Nylon (PA) 6 & 66 are both synthetic polymers called polyamides, with the numbers describing the type and quantity of polymer chains in their chemical structure. Most nylons, including 6 & 66, are semi-crystalline and possess good strength and durability for demanding applications.
Nylon Properties
As polyamides, Nylon 6 & 66, whilst having their own separate and distinct benefits, do share many of the same core properties:
Differences
So whilst Nylon 6 & 66 are very similar materials, they do provide slightly different characteristics. The reason for the differences is largely due to their differences in chemical structure. Nylon 6 is made from one monomer which has 6 carbon atoms whilst Nylon 66 is made from 2 monomers with each one having 6 carbon atoms, hence the Nylon 66 name.
NYLON 6
NYLON 66
Less crystalline
More crystalline
Lower mold shrinkage
Exhibits greater mold shrinkage
Lower melting point
Higher melting point
Lower heat deflection temperature
Higher heat deflection temperature
Higher water absorption rate
Lower water absorption rate
Poor chemical resistance to acids
Better chemical resistance to acids
Withstands high impact and stress and better stands up to hydrocarbons
Better stiffness, tensile modulus and flexural modulus
Lustrous surface finish, easy to colour
More difficult to colour
An important difference between Nylon 6 & 66 is mold shrinkage. Nylon 6&#;s lower mold shrinkage adds reliability to final part dimensions which is beneficial whilst Nylon 66&#;s greater mold shrinkage, as it is exposed to cool air and solidifies, means the material&#;s shape changes more after processing, which must be accounted for.
Other key differences between the two nylons are water absorption rates and heat deflection temperatures. As Nylon 6 absorbs more water than Nylon 66 and has lower heat deflection temperatures, it is not suited to applications that are exposed to water at high temperatures. Nylon 66 would be a better choice between the two.
Typical Material Applications
Which One Should I Choose?
The needs of an application have to be considered in terms of processing, aesthetic appearance, and mechanical properties first, in order to decide whether Nylon 6 or 66 is more suitable.
Nylon 6 should be used if a lightweight engineering plastic is required to withstand high impact and stress. It has better aesthetic appearance than Nylon 66 due to its lustrous finish and is easier to dye. It is an ideal choice for applications in the automotive, industrial and military industries. Common applications include: gears, firearm components and automotive engine compartments. It is not ideal, however, for applications that are exposed to water at high temperatures due to its higher water absorption and lower heat deflection rate than Nylon 66, which would be a better choice.
Nylon 66 should be used if a high performing engineering plastic is required that will be exposed to higher temperatures. Additionally, its stiffness and good tensile and flexural modulus make it an ideal material for applications that need repeated long-term performance. Typical applications include: friction bearings, radiator caps and tire ropes.
Are you interested in learning more about nylon 6 yarn? Contact us today to secure an expert consultation!
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