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The oral histories presented here document the research and development processes that transformed Kevlar from a novel polymer in the laboratory to a life-changing product in the marketplace. Through many surprising twists and turns, the people profiled here managed to make Kevlar serve the complicated and occasionally contradictory interests of the DuPont company, scientific inquiry, the marketplace, and the general public. Their stories are a rich study in the business and technology of innovation.
Interviews were conducted by John Kenly Smith, PhD, in 2014 and 2015. Special thanks to the 1916 Foundation, the friends and family of Mary Laird Silvia, and individual donors for support of this project.
After describing his education and early work at the DuPont Company on polymer solutions, Herbert Blades recounts his contributions to the development of Tyvek and Kevlar. On the Tyvek project, he describes developing the polymerization process for creating high-density polyethylene fibers after such paper-like fibers had been accidentally created in the laboratory.
Blades details his work on Kevlar, for which he developed a commercially viable process to spin fibers from the polymer. Blades describes the three components of the process. First, he discovered that a relatively high concentration of polymer could be dissolved upon heating in 100 per cent sulfuric acid, which is non-aqueous and non-corrosive. The resulting solution had a low enough viscosity that it could be spun rapidly through a spinnerette, a small hole. Next, Blades discovered that instead of spinning the fiber directly into a water bath, leaving a small air gap led to fibers that were significantly stronger. Finally, he determined that the water "quenching" of the fiber occurred extremely fast. His spinning innovations made it possible to spin Kevlar fibers economically and at high speeds.
Wesley Memeger, Jr. details his contribution to streamlining the synthesis of Kevlar, which allowed the timely start-up of the first commercial scale Kevlar plant. In the laboratory, the polymer for Kevlar had previously been prepared by polymerizing para-phenylene diamine and terephthaloyl chloride in a mixture of two solvents, HMPA (hexamethylphosphoramide) and NMP (N-methylpyrrolidinone). Memeger found that a polymer with satisfactory molecular weight could be made using only HMPA, a discovery which made the preparation of Kevlar more commercially viable, as it allowed for a continuous polymerizer in a single solvent system.
Memeger recounts that DuPont used HMPA as the solvent for Kevlar production in the early 1970s, but after toxicology tests conducted at the company's Haskell Laboratory raised doubts about the safety of the solvent, DuPont replaced HMPA with NMP and calcium chloride. Memeger describes his subsequent work at DuPont investigating melt processible polymers, which share some properties with Kevlar but lack equivalent chemical and thermal stability, as well as his work on ring opening routes to polymers with novel properties. An accomplished artist, Memeger continues to be impressed by the elegance and simplicity of the Kevlar polymer that produces such remarkable properties.