Nylon 6 vs. Nylon 66: Key Differences & Which One to Choose
Nylon 6 is a polyamide made from caprolactam; Nylon 66 is made from two monomers—adipic acid and hexamethylenediamine—creating a stiffer, more heat-resistant chain.
Designers often grab the wrong reel because both feel silky and strong, yet one melts at your soldering iron while the other survives under a car hood—costing prototypes and reputation.
Key Differences
Nylon 66 tolerates 40 °C more heat, absorbs half the moisture, and shrinks less, giving tighter tolerances. Nylon 6 is tougher at impact, dyes brighter, and extrudes faster—cheaper for big, colorful parts.
Which One Should You Choose?
Pick Nylon 66 for engine mounts, electrical housings, or gears needing precision under heat. Choose Nylon 6 for consumer sporting goods, textile fibers, or large 3D prints where vibrant color and impact strength matter more than dimensional stability.
Can I dye Nylon 66 as easily as Nylon 6?
No. Nylon 6’s open molecular structure accepts acid dyes at lower temps, while Nylon 66 needs hotter baths and more time for deep shades.
Does moisture really change part dimensions?
Yes. Nylon 6 can swell 3 % at 50 % humidity, warping tight fits; Nylon 66 swells only ~1 %, keeping gears and bearings true.