The Numbers Racket
On these pages there are a lot of names like "nylon 6-6", "polyamide 9", and "polyamide 5-10".
What do all these names and numbers mean? It's really not that complicated.
"Polyamide"
is simply the chemical name for nylon. Some nylon is made from two different
monomers,
a diacid and a diamine. For example, adipic acid and hexamethylene diamine are
used to make the most common nylon in the world. Since hexamethylene diamine has six
carbon atoms, and adipic acid also has six carbon atoms, the nylon they form is called
nylon 6-6, or polyamide 6-6. Before the name "nylon" was used, nylon 6-6 was called by a
codename, "fiber 66".
An earlier nylon that the Carothers group studied was made from pentamethylene diamine and sebacic acid. Pentamethylene diamine has five carbon atoms, and sebacic acid has ten carbon atoms. So the nylon they make is called nylon 5-10, or polyamide 5-10.
Carothers wanted polyamide 5-10 to be produced commercially. It has superior properties to nylon 6-6, but nylon 6-6 is cheaper to make.
Some nylons are made from one kind of monomer, such as a cyclic amide called a lactam. For example, caprolactam is a lactam with six carbon atoms. So nylon made from caprolactam is called nylon 6, or polyamide 6.
One can also make nylon 6 from an amino acid which contains six carbons, aminocaproic acid:
Polyester names
This system can be used to name other
polymers,
too. In fact, Carothers and his team invented
it to name polyesters. For example, a polyester made
from propylene glycol, which has three carbon atoms, and hexamethylene dicarboxylic acid, which
has sixteen carbon atoms, is called polyester 3-16.
This polyester was first invented by Julian Hill in 1930, but was never produced commercially. It was a different polyester that became the polyester you see everyday, called poly(ethylene terephthalate), or PET. It was named using a different system from the other polymers on this page, obviously.
