Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Theory predicts aging process in DVDs, plexiglas, other polymer glasses

Polymer glasses are versatile plastics widely used in applications ranging from aircraft windshields to DVDs.

Researchers at the University of Illinois have developed a theory that predicts how these materials age. The theory also explains why motions at the molecular level can have macroscopic consequences.

"Glasses, including polymer glasses, are essentially frozen liquids,"
said Kenneth S. Schweizer, the G. Ronald and Margaret H. Morris Professor of Materials Science at the University of Illinois. "They appear solid, but because they are frozen liquids, the molecules continually undergo small motions that lead to a time dependence of properties."

Three years ago, Schweizer and graduate student Erica Saltzman developed a theory that described the transition upon cooling of a polymeric material from a liquid to an amorphous solid or glass. The theory explained how the viscosity of a polymer glass changes dramatically over a narrow temperature range. The researchers reported that work in the July 22, 2004, issue of the Journal of Chemical Physics.

Now, in the April 20 issue of Physical Review Letters, Schweizer and postdoctoral research associate Kang Chen present a theory to describe the aging process in polymer glasses. The new theory predicts not only how polymer molecules move, but also the material properties, at a wide variety of times and temperatures.

Polymer glasses are plastics that possess unusual and technologically useful mechanical properties. Unlike most other types of solids, polymer glasses can possess high impact resistance and, even though they are stiff, can often be significantly deformed without breaking. They are usually inexpensive to make, and easily melted and molded into many shapes.

And, they're always on the move.

Unlike window glass, which melts at roughly 1,200 degrees above room temperature, polymer glasses have melting points much closer to room temperature. So close, in fact, that many polymer glasses retain some liquid-like properties at room temperature, including motion at the molecular level.

"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."

As the material gradually reconfigures and approaches equilibrium at room temperature, the movements become slower and slower. Under sufficiently cold conditions, this "relaxation" time can become astronomically large, even longer than the age of the universe for some materials.

"Among other possible effects, the aging process causes polymer glasses to become stiffer and often more brittle," said Schweizer, who also is a professor of chemistry, of chemical and biomolecular engineering, and a researcher at the university's Frederick Seitz Materials Research Laboratory.

Over time, the molecules crowd closer together, increasing the density and changing the mechanical properties of the material.

"Through our theory we developed a way to relate the physical properties of a polymer glass to the time scale of molecular movement," Schweizer said. "This information is especially important in engineering applications where small changes in dimensions, stiffness or other properties can affect long-term performance or reliability."

The work was funded by the National Science Foundation.

Editor's note: To reach Kenneth Schweizer, call 217-333-6440; e-mail:

James E. Kloeppel | University of Illinois
Further information:

More articles from Physics and Astronomy:

nachricht 'Frequency combs' ID chemicals within the mid-infrared spectral region
16.03.2018 | American Institute of Physics

nachricht Fraunhofer HHI have developed a novel single-polarization Kramers-Kronig receiver scheme
16.03.2018 | Fraunhofer-Institut für Nachrichtentechnik, Heinrich-Hertz-Institut, HHI

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

TIB’s Visual Analytics Research Group to develop methods for person detection and visualisation

19.03.2018 | Information Technology

Tiny implants for cells are functional in vivo

19.03.2018 | Interdisciplinary Research

Science & Research
Overview of more VideoLinks >>>