Rachel M. Thurston

Ms. Thurston is currently working in Columbus, Ohio.

Background

I've been interested in polymers ever since I first heard about them through the Chemistry Explorers club in high school. Growing up near the University of Akron, it was inevitable that I would hear about them, and what I heard fascinated me. I knew then that I wanted to learn as much about polymers as I could, so when I went to college I studied polymers and made a career out of them.

Education

• Case Western Reserve University, Department of Macromolecular Science, MS August 1996
  Thesis on environmental stress cracking of polyethylene, with Professor Charles Rogers.
• MIT, Materials Science and Engineering, SB May 1993, with a concentration in polymers

Thesis Research

My thesis was on "Environmental Stress Cracking of Polyethylene", on a fellowship from British Petroleum. Environmental stress cracking (ESC) was first observed 50 years ago by Richards, who noted that polyethylene, normally a ductile material, failed brittly when exposed to mobile polar liquids. In the early 1950s, Bell Telephone was using low-density polyethylene as cable sheathings for telephone cable, which had an unusually high incidence of failure. It turns out they were using Igepal surfactant, one of the most aggressive known ESC agents, to lubricate the cables while running them through the sheaths. Bell Labs began extensive research in the phenomenon, and when ESC failure started appearing in polyethylene gas pipes, the gas companies soon followed.

Over the past 50 years, there have been many theories proposed for the mechanism of ESC, but each theory breaks down at some point in analyzing the data, so there is no definitive answer as of yet. Some of the failed approaches have been classical fracture mechanics, surface tension reduction, diffusion controlled surfactant distribution, and viscous flow control of surfactant distribution. My research proposes an exciting new theory based on fracture mechanics and the thermodynamics of micelle formation. It is well-known that surfactants form micelles in aqueous solution and inverse micelles in nonpolar solvents. Other research has shown that organic molecules diffusing through polyethylene cluster rather than distributing randomly. It has been shown in this lab and others that Igepal is absorbed into the polyethylene bulk rather than just sitting on the surface. Therefore, it is proposed that surfactants cause environmental stress cracking by diffusing into polyethylene and forming inverse micelles, which act as flaws or microvoids to initiate craze formation and subsequent crack growth under stress. (more evidence forthcoming shortly)

Professional Affiliations

• Case Western Reserve University, Department of Macromolecular Science
• The Society of Plastics Engineers
• American Physical Society
• American Chemical Society

Feature Article

My thesis research was part of a 5-year partnership between British Petroleum and CWRU. The program was featured in the BP internal research newsletter, along with a picture from my research lab, in June 1995.

Polymer Links

Personal

Last update 10/10/05

Rachel M. Thurston

surakofb5@yahoo.com