Nylon fasteners such as screws, flat washers, hex head cap screws, hex nuts spacers and standoffs etc. are some of the most in demand fasteners in the world of plastics.  Many people choose nylon fasteners because they are cheaper and more well-known than many other plastic fasteners.  For many applications, nylon fasteners work just fine.  However, nylon has several weak points which may cause nylon fasteners to fail in various extreme situations.

Nylon was first developed in the late 1930’s by Wallace Carothers at DuPont and introduced as a fabric at the 1939 New York World’s Fair. Much of the world’s production of nylon is still used in the textile industry for cloth.  Since 1939, nylon has been incorporated into such diverse products as toothbrushes, carpets and truck tires.

Nylon 6/6 is a popular grade for nylon fasteners.  It is a semi-crystalline polymer, one with crystalline regions within an amorphous matrix.  It is a polyhexamethylene adiamide in which the amide group –(-CO-NH-)- provides hydrogen bonding between polyamide chains.

While much of the world’s production of nylon 6/6 is used for cloth, it is also an important thermoplastic engineering resin extruded into bar shapes or for injection molding and used to manufacture nylon fasteners including machine screws, nuts, washers, spacers, bearings, gears, and fittings.  However, there are situations where Nylon 6/6 fasteners are definitely not the right choice for an engineering application.  Here’s a list of the six top reasons NOT to use nylon fasteners in an application:

1.  Moisture: Nylon is hygroscopic, meaning that it attracts and absorbs water from the surrounding environment.  The composition of the plastic is changed as water molecules are suspended between the molecules of the material.  Over time Nylon 6/6 will swell considerably and begin to degrade.   Nylon fasteners are definitely not recommended for use in or around water.

2.  UV Resistance:  Nylon 6/6 is not UV resistant.*   When placed in sunlight over time the physical and mechanical properties of nylon fasteners will degrade.   They will often turn yellow and become brittle.

3.  Chemical resistance:  Nylon 6/6 is generally not chemically resistant.  It performs poorly in acids and halogens such as fluorine and chlorine.  It stands up slightly better to ketones (acetone, camphor) and halogenated hydrocarbons (carbon tetrachloride, dichlorobenzene.)  It is not recommended for use with these chemicals.

4. Temperature:    Nylon 6/6 has a continuous service temperature of 223⁰ F (121⁰ C.)  Nylon fasteners are not recommended for use in ovens, nor in contact with boiling water.  Teflon (PTFE) is a much better choice.

5.  Flammability:  Nylon 6/6 has a UL 94 V-2 rating.**  94V-2  is a UL test rating in which a specified test specimen stops burning within 60 seconds after two applications of ten seconds each of a flame with flaming drips allowed. So nylon fasteners melt rather than burn when in contact with an open flame. If an application requires a nonflammable material, Nylon 6/6 is not recommended. *** 

6.  High Strength:  Plastics that are strong enough to replace metals are much in demand.  The ultimate tensile strength of nylon 6/6 is 10,000 PSI .  This is not unreasonably low, as other common engineering plastics such as PVC and polypropylene have an ultimate tensile strength of 9,580 and 5,800 PSI respectively.  However, nylon fasteners are certainly not the strongest available nor are they as strong as metal fasteners.  The ultimate tensile strength of FR4/G10 is 45,000 PSI.   Cast iron has a UTI of 29,000 PSI and copper comes in at 31,900 PSI while aluminum has a UTI of 43,500 PSI.  Nylon 6/6 is not recommended when higher strength is required and definitely not as a replacement for metal.

*There are grades with additives such as carbon black that improve the UV performance of Nylon 6/6.

**Grades with flame retardant additives are available on the market.

***Additives are used to improve the flame resistance of Nylon 6/6.

Have you used nylon fasteners in your applications?  How did they perform for you?  Let us know in the comments below.

Looking for more information on the many different grades of nylon?  Download our complimentary guide!


8 responses to “6 Reasons NOT to Use Nylon Fasteners

  1. All quick reads on plastic vs. nylon or polymer (for garden hose end repair clamps) state that the manufacturing of plastic is not environmentally friendly AT ALL, which is important to a great many people. Is the process for making nylon / polymer really less harmful to the environment, or is this just hype? I have not done any in-depth research on my own yet. If there’s no consensus among experts and sellers, I’ll just go with the zinc clamps as before, which have proven to be almost indestructible, albeit a bit heavy for the application. When you get 150 feet of rubber hose connected end-to-end, every ounce of weight is uppermost in your mind!

    1. Thanks for your question, and for reading the Craftech blogs. I don’t think the manufacture of either plastic OR zinc is what I would label environmentally friendly. Honestly, I’m not sure which is more so. Even though I am also an environmentalist, I don’t think the impact of a couple of connectors will make much of an impact regardless of your direction. Good luck!

  2. Nylon is good in breakaway applications such as helmet visors. You would rather have the bolt break than the helmet visor and they save weight over metal.

  3. New Technology now exists to prevent nylon 6 and 6,6, and all polyamides from UV degradation , chalking, cracking from long term photo themal degradation. This is a molecular process in the melt extrusion process and reduces the need for large pigment loadings and terminates yellowing for ever especially in natural and white pigment parts! The data is available and years of testing in the harshest environments already done.

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