Stretz earns honors as 2007 Kinslow Award winner

Focusing on controlling and aligning a few nanoparticles at a time, Tennessee Tech University assistant professor of chemical engineering Holly Stretz is adding to the science of how to produce the best fire retardant material available.

Those natural nanoparticles of volcanic ash, with a thickness equal to only 10 atoms each, were key to the published research that recently earned Stretz honors as the 2007 Kinslow Award winner. The award is given annually for the best paper written by a TTU engineering faculty member and published in a refereed professional journal. The paper, "Properties and Morphology of Nanocomposites Based on Styrenic Polymers-1: Styrene-acrylonitrinile Copolymers," was published in Polymer, one of the most competitive peer-reviewed journals in polymer science and engineering.

"Holly's contribution offers a significant breakthrough in the field," said Pedro Arce, professor and chairperson of TTU's chemical engineering department. "This subject has received strong attention, but Stretz’s efforts have been quite quantitative and critically examine the characterization of dispersion."

Stretz's research focused on the top-down manufacturing of a polymer composite that has the potential to be over twice the stiffness of steel and reduce the flammability of household material by 80 percent. She concentrated on a technique to disperse, control and arrange nanoparticles that are tinier than viruses. The process used was an inexpensive extrusion and injection molding process.

Stretz says the key to harnessing the nanoparticles is to first disperse them by making the polymer more hydrophilic — more like water.

"These particles are so tiny its difficult to control where they go, they don’t settle from gravity necessarily because even air molecules can crash into them and dislodge where you put them, and their movement without an external field is perfectly random," explained Stretz. "The way we controlled and aligned them was through a high-shear environment where we push them through a small hole at a very high pressure. They follow the streamlines of polymer melt flow.

"This paper looked at a model compound for materials used for computer housings," said Stretz. "We think that if we control dispersion and alignment we can significantly reduce the rate at which such materials will release heat during burning and therefore reduce the rate at which a fire spreads through a room."

Stretz says there are several other applications that will benefit consumers if materials made from polymers and these nanoparticles can be developed. For instance, the automotive industry would be able to develop lighter, more inexpensive parts made from plastics due to this process because the stiffness of the nanoparticles significantly reduces warping of plastics.

She says barrier applications — such as packaging, tires and bottles — would be improved with this polymer, so that a film is better able to contain or exclude gases.

"The nanoparticles would prevent oxygen and CO2 from moving in and out of the packaging," she explained. "So it wouldn't let the CO2 out of the beer bottle and wouldn't let the oxygen into the ketchup bottle. Or, ideally, a tire would never go flat."

Stretz earned her doctorate in chemical engineering from the University of Texas-Austin in 2005. She holds a master's degree in chemistry from Texas State University and a bachelor's degree in chemistry from Texas A&M University.

The Kinslow Award honors Professor Emeritus Ray Kinslow, who taught for 32 years at Tennessee Tech and served as head of the Engineering Science and Mechanics Department for 25 years. Last year's award winner was Electrical and Computer Engineering Associate Professor Robert Qiu.

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