by Staff Writers
Oak Ridge TN (SPX) Nov 10, 2014
For much the same reason LCD televisions offer eye-popping performance, a thermomagnetic processing method developed at the Department of Energy's Oak Ridge National Laboratory can advance the performance of polymers.
Polymers are used in cars, planes and hundreds of consumer products, and scientists have long been challenged to create polymers that are immune to shape-altering thermal expansion.
One way to achieve this goal is to develop highly directional crystalline structures that mimic those of transparent liquid crystal diode, or LCD, films of television and computer screens. Unfortunately, polymers typically feature random microstructures rather than the perfectly aligned microstructure - and transparency - of the LCD film.
ORNL's Orlando Rios and collaborators at Washington State University have pushed this barrier aside with a processing system that changes the microstructure and mechanical properties of a liquid crystalline epoxy resin.
Their finding, outlined in a paper published in the American Chemical Society journal Applied Materials and Interfaces, offers a potential path to new structural designs and functional composites with improved properties.
The method combines conventional heat processing with the application of powerful magnetic fields generated by superconducting magnets. This provides a lever researchers can use to control the orientation of the molecules and, ultimately, the crystal alignment.
"In this way, we can achieve our goal of a zero thermal expansion coefficient and a polymer that is highly crystalline," said Rios, a member of ORNL's Deposition Science Group. "And this means we have the potential to dial in the desired properties for the epoxy resin polymers that are so prevalent today."
Epoxy is commonly used in structural composites, bonded magnets and coatings. Rios noted that thermosets such as epoxy undergo a chemical cross-linking reaction that hardens or sets the material. Conventional epoxy typically consists of randomly oriented molecules with the molecular chains pointing in every direction, almost like a spider web of atoms.
"Using thermomagnetic processing and magnetically responsive molecular chains, we are able to form highly aligned structures analogous to many stacks of plates sitting on a shelf," Rios said. "We confirmed the directionality of this structure using X-ray measurements, mechanical properties and thermal expansion."
Co-authors of the paper, "Thermomagnetic processing of liquid crystalline epoxy resins and their mechanical characterization using nanoindentation," are Yuzhan Li and Michael Kessler of Washington State's School of Mechanical and Materials Engineering.
The ORNL portion of the research was supported by the Critical Materials Institute, an Energy Innovation Hub funded by DOE's Office of Energy Efficiency and Renewable Energy. Washington State's research was funded by the Air Force Office of Scientific Research.
Oak Ridge National Laboratory
Space Technology News - Applications and Research
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|