Why is nylon 6 called that?

The naming of the nylon family is quite interesting, much like naming children; it usually directly reflects their "family genes."

The reason Nylon 6 is named as such is very simple:

Core reason: The number of carbon atoms

Characteristic of a single raw material: Manufacturing Nylon 6 only requires one main chemical raw material, called "caprolactam."
Counting the atoms: Under a microscope, the molecular structure of this raw material contains exactly 6 carbon atoms.
Naming logic: Because only these 6 carbon atoms are involved in the construction of the entire long chain, for convenience and ease of memorization, scientists and manufacturers simply called it "Nylon 6."

Structural "unique" property

Difference between monomer and dimer: This is also the biggest difference between it and Nylon 66. Nylon 66 is composed of two different raw materials, each containing 6 carbon atoms, hence the name "66."
Nylon 6, on the other hand, is "independent," with only one type of building block containing 6 carbon atoms repeating from beginning to end, so it only needs one number to represent its identity.

Background and differentiation

For easy differentiation: In the early plastics industry, there were many different formulations of nylon. The "6" label was added to allow factory workers and customers to easily identify its properties.
Performance implication: The "6" in the name also hints at its structural characteristics. Because it only has one set of carbon atoms, its molecular arrangement is different from "66," making it more flexible and easier to dye than 66.