In 1928, no one had ever made a synthetic compound with a molecular weight higher than 4,021 atomic mass units. To test this scheme, Carothers challenged his team to use step-growth polymerization to break this record and make a molecule with a molecular weight of 6,000.

In 1930 Julian Hill, a member of the Carothers team did just that. He reacted propylene glycol with hexadecamethylene dicarboxylic acid.

The product was called polyester 3-16, because propylene glycol has three carbon atoms, and hexadecamethylene dicarboxylic acid has sixteen carbon atoms. This new material shattered the old molecular weight record. Its weight was 12,000!

By now DuPont's management was interested in turning research into real profitable products. One idea they were interested in was synthetic silk. It was hoped that polyester 3-16 would become synthetic silk. The material could be made into fibers, but it couldn't be made into clothing. It melted at mildly high temperatures, which meant it couldn't be ironed. It also dissolved easily in dry cleaning solvents.

Carothers thought about how to make material with a higher melting point that wouldn't dissolve so easily. The answer he came up with became what we now call nylon.

The members of Carothers team studied many different polyesters, but strangely they never tried to make a polyester from terephthalic acid and ethylene glycol while searching for a good synthetic fiber. The polyester that would have resulted has a high melting point and doesn't dissolve easily, and it makes excellent fibers.

Poly(ethylene terephthalate, or PET, would be made in the Carothers lab, sure enough, by Edgar W. Spanagel in October 1934. But this was only because he was trying to make small cyclic molecules. He was working on a project that led to the creation of the first synthetic musk scents.

By this time, DuPont was putting so much effort into developing a good polyamide fiber that there was no time to investigate this new polymer further. It would have to be re-invented several years later by chemists at the Calico Printers Association in the United Kingdom, a forerunner of Imperial Chemical Industries (ICI). It was named Terylene^¨ and it would become the polyester we're all familiar with as clothing and soft drink bottles. Ironically, though none of the polyesters studied by Carothers and his team became useful products, DuPont ended up making PET under license, which they called Dacron^¨.