Materials—Polymer theory problem

Materials—Polymer theory problem

Studies of simulated entangled polymers in equilibrium and following deformation may indicate that a 40-year-old theory of how plastic polymers behavior during processing needs updating. Credit: Yangyang Wang/Oak Ridge National Laboratory, U.S. DOE
Studies of simulated entangled polymers in equilibrium and following deformation may indicate that a 40-year-old theory of how plastic polymers behavior during processing needs updating. Credit: Yangyang Wang/Oak Ridge National Laboratory, U.S. Dept. of Energy. (hi-res image)

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Jonathan Hines, Communications
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April 2, 2018 - Scientists at Oak Ridge National Laboratory have conducted a series of breakthrough experimental and computational studies that cast doubt on a 40-year-old theory describing how polymers in plastic materials behave during processing. The team used high-performance computing and neutron scattering to evaluate systems of highly entangled, spaghetti-like polymers undergoing deformation, finding evidence of flaws in the so-called “tube model,” which describes how polymer strings flow when stretched, pulled and squeezed. Originally pioneered by Nobel Prize laureate Pierre-Gilles de Gennes, the model has enabled practical predictions for manufacturing and processing of plastic materials. A complete description of polymer dynamics, however, continues to elude scientists. “We need modifications, or maybe a new theory, to explain the flow behavior of polymers,” said Yangyang Wang of ORNL’s Center for Nanophase Materials Sciences, who led the research. “Better understanding of polymer behavior could lead to improved control of materials and aid design of materials with novel characteristics.”