New theory predicts polymer aging process
Published: April 25, 2007 at 5:49 PM
CHAMPAIGN, Ill., April 25 (UPI) -- U.S. scientists have developed a theory that predicts the aging process in DVDs, Plexiglas and other polymers used in a wide range of applications.
The theory developed by University of Illinois researchers also explains why motions at the molecular level can have macroscopic consequences.
"Glasses, including polymer glasses, are essentially frozen liquids," said Professor Kenneth Schweizer. "They appear solid, but because they are frozen liquids, the molecules continually undergo small motions that lead to a time dependence of properties."
Schweizer and post-doctoral research associate Kang Chen developed the new theory that predicts not only how polymer molecules move, but also their material properties, at a wide variety of times and temperatures.
"The movements are so small and so slow, we can't see them without the aid of sophisticated measuring tools," Schweizer said. "Nevertheless, this residual motion can significantly change the material's mechanical and thermal properties over time."
He said the study's findings are important in engineering applications, in which small changes in dimensions, stiffness or other properties can affect long-term performance or reliability.
The research, funded by the National Science Foundation, appears in the April 20 issue of Physical Review Letters.
The theory developed by University of Illinois researchers also explains why motions at the molecular level can have macroscopic consequences.
"Glasses, including polymer glasses, are essentially frozen liquids," said Professor Kenneth Schweizer. "They appear solid, but because they are frozen liquids, the molecules continually undergo small motions that lead to a time dependence of properties."
Schweizer and post-doctoral research associate Kang Chen developed the new theory that predicts not only how polymer molecules move, but also their material properties, at a wide variety of times and temperatures.
"The movements are so small and so slow, we can't see them without the aid of sophisticated measuring tools," Schweizer said. "Nevertheless, this residual motion can significantly change the material's mechanical and thermal properties over time."
He said the study's findings are important in engineering applications, in which small changes in dimensions, stiffness or other properties can affect long-term performance or reliability.
The research, funded by the National Science Foundation, appears in the April 20 issue of Physical Review Letters.
© 2007 United Press International. All Rights Reserved.
This material may not be reproduced, redistributed, or manipulated in any form.
This material may not be reproduced, redistributed, or manipulated in any form.
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