热磁处理技术能提高聚合物的性能

For much the same reason LCD televisions offer eye-popping performance, a thermomagnetic processing method developed at the Department of Energy's Oak Ridge¹ 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 thermal² expansion. One way to achieve this goal is to develop highly directional crystalline structures that mimic³ those of transparent⁴ liquid crystal diode, or LCD, films of television and computer screens. Unfortunately, polymers typically feature random⁵ microstructures rather than the perfectly⁶ aligned⁷ 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 resin⁸. Their finding, outlined in a paper published in the American Chemical Society journal Applied⁹ Materials and Interfaces¹⁰, offers a potential path to new structural¹¹ designs and functional¹² 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 orientation¹³ of the molecules¹⁴ and, ultimately, the crystal alignment¹⁵.   "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 Deposition¹⁶ 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, bonded¹⁷ magnets and coatings. Rios noted¹⁸ that thermosets such as epoxy undergo a chemical cross-linking reaction that hardens or sets the material. Conventional epoxy typically consists of randomly¹⁹ oriented molecules with the molecular²⁰ 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#p#分页标题#e#²¹ 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."