Tracing the History of Polymeric Materials, Part 13: How Nylon and Polyesters Rewrote Textile Innovation

The same wave of innovation that birthed nylon also spurred the creation of synthetic polyesters. In the 1930s, Julian Hill, a key member of Wallace Carothers’ DuPont team, first synthesized polyester fibers—long before nylon itself. Yet once nylon’s exceptional properties emerged, polyester research was put on hold. The intertwined stories of nylon and polyester can best be understood through a closer look at their chemistry.

Both first-generation nylons and early polyesters belong to the family of condensation polymers. Carothers began exploring these reactions as early as 1926 while still in academia. With the resources of DuPont’s laboratories at his disposal, he quickly translated theory into practice. Condensation polymers form when two molecules—each bearing reactive functional groups at both ends—react to release a small molecule (often water) and grow in both directions, producing a long chain.

Esters arise when an alcohol reacts with a carboxylic acid, as shown in Figure 1, where ethyl alcohol and acetic acid form ethyl acetate. The characteristic carbonyl–oxygen double bond defines the ester functional group. Amides are formed similarly, but an amine replaces the alcohol. In Figure 2, propanoic acid reacts with urea to produce propanamide.

In typical ester and amide syntheses, only one reactive end participates, terminating the reaction. Carothers discovered that when both ends of a molecule carry reactive groups, the process can continue, generating a long-chain macromolecule—a polymer. Figure 3 illustrates this principle applied to nylon 66.

The amide bond—comprising a carbonyl group (C=O) and an N–H link—creates a dipole that facilitates strong intermolecular hydrogen bonds. The oxygen bears a partial negative charge, while the hydrogen attached to nitrogen carries a partial positive charge. When adjacent polymer chains align, these dipoles attract, conferring nylon’s high tensile strength and a melting point of 260 °C (500 °F). This hydrogen‑bonding network is the cornerstone of nylon’s superior mechanical performance.

In contrast, ester linkages lack the N–H component, so they cannot form the same robust hydrogen bonds. As a result, aliphatic polyesters exhibit lower melting points—typically around 80 °C (176 °F) for a polymer with a molecular weight comparable to nylon 66—and are more prone to hydrolysis. These properties did not meet DuPont’s goals for high‑performance fibers, leading the company to shift focus entirely to nylon.

Three years later, British chemists John Rex Whinfield and James Tennant Dickson revisited the DuPont data and identified a way to improve polyester’s properties by incorporating aromatic rings. Aromatic structures, such as benzene or xylene, are planar, rigid, and significantly enhance thermal and mechanical behavior when embedded in a polymer chain.

In 1939, Whinfield and Dickson combined the aromatic carboxylic acid terephthalic acid with ethylene glycol to produce the first commercially viable polyester—polyethylene terephthalate (PET). Together with W.K. Birtwhistle and C.G. Ritchie, they patented PET and introduced a fiber under the brand name Terylene, launched by Imperial Chemical Industries (ICI) in 1941.

This breakthrough inaugurated the modern era of polyester fibers, a story we will continue in the next installment.

About the Author
Michael Sepe is an independent materials and processing consultant based in Sedona, Ariz. With over 45 years in the plastics industry, he advises clients across North America, Europe, and Asia on material selection, design for manufacturability, process optimization, troubleshooting, and failure analysis. Contact: (928) 203‑0408 | mike@thematerialanalyst.com