Nylon 6/6 is a polyamide plastic made up of two monomers. Each monomer contains 6 carbon atoms of hexamethylenediamiine and adipic acid. We have written about the reasons not to use nylon in our blog some time ago.
Six Reasons Not to Use Nylon
Nylon is hygroscopic meaning is absorbs water even from the natural environment. This can cause changes in a part’s dimensions.
It is not UV resistant without additives.
It is not particularly chemically resistant as it performs poorly in acids and halogens. This material does slightly better in ketones and hydrogenated hydrocarbons. However, it is not recommended for use in the presence of these chemicals.
Nylon has a relatively low continuous service temperature of 223 degrees F. So it is not recommended for use in ovens or in boiling water.
Its flammability rating is UL 94V-2. Therefore nylon parts melt rather than burn.
And it is not high strength with an ultimate tensile strength of 10,000 psi. Not bad, but FRP/G10 has a UTS of 45,000 PSI.
Popularity of Nylon
But Nylon is one of the most popular plastics in use. So why is this? First of all, nylon is used extensively in the building of automobiles to help with greater fuel efficiency. And it is used in fiber for fabrics from nylon stocking to parachute fabric as well as tents and rope. Nylon accounted for about a 30 billion USD industry in 2020. About a third was used in the automotive industry and one quarter in engineered plastics for products such as nylon fasteners and nylon custom parts. It is also used in the textile industry and the electrical and electronics industry. The most common grades are Nylon 6/6. Nylon 6, Nylon 4/6 and Nylon 612.
Nylon as an Insulator
- Importantly, nylon is an insulator. It’s electrical resistivity is 1500 V/mil. This makes it useful in electrical applications and electronics. Parts for these applications made from Nylon are screws, hex nuts, washers, cable ties, spacers, standoffs, screw insulators, parts for printed circuit boards including panel fasteners, snap rivets, and grommet nuts as well as threaded rod, custom parts and thousands of other fasteners.
Nylon is Hygroscopic
- Although it is hygroscopic it is however water repellent. Water repellent means a material is able to resist water penetration but not completely. But in many applications water repellent is all that is needed. For example in the automotive industry. Although parts of a car might get wet, usually they will dry off fairly quickly. The same for things made from nylon fibers. And usually these products are not made to tight tolerances.
Not Naturally UV Resistant
- The lack of UV resistance can be a problem if a product made from nylon receives UV rays continually. Say like a summer folding chain made of nylon webbing. However, the material can be treated with UV stabilizers which effectively stop deterioration from the sun. Also, some applications will never be exposed the the sun’s rays. For example nylon is used extensively for indoor carpets. UV resistance can also be important in engineered plastic applications such as nylon fasteners that are exposed to UV rays.
Gasoline is a Hydrocarbon While Kerosene is a Mixture
- This material does well in gasoline and kerosene. Since nylon is derived from petrochemicals this is not surprising. Nylon 6 is used in car engine components such as bushings, oil containers, crankcases, cylinder head covers and much more. Nylon 612 had been used in fuel line applications.
- They also have good wear resistance. It is also possible to add molybdenum disulphide to the material to improve lubricity. This is important in the engineered plastics industry for bushings and bearings.
Low Continuous Service Temperature
- Nylon has a relatively low continuous service temperature for an engineered plastic of 223 degrees F. However, this can be enough for an application. In automobiles, nylons are used in headlamp bezels, wheel covers, fuel caps, tailgate handles, front end grilles and exterior mirrors. And clothes, nylon stockings, rope and tents will perform just fine with the continuous service temperature of nylon.
Does Not Burn
- And nylon tends to melt rather than burn which is useful in all applications.
Useful in Breakaway Applications
- Nylon is not the strongest plastic available. This is useful in applications where a part is designed to breakaway at a certain load. And adding glass-fiber to the resin will result in a tensile strength of 32,000 psi, approximately 200 times that of the base resin.
Replacements for Nylon
While nylon use is expected to grow in the coming years there are other less expensive materials that can perform well in the required applications. Some even proform better. Such plastics as polypropylene, Polyvinylidene Fluoride (PVDF), para-armid synthetic fibers and bioabsobable polymers are an increasing threat to the use of nylons.