This project will study nonlinear mechanics of a major class of engineering materials, i.e., entangled polymeric liquids that are produced at a rate of a few hundred billion pounds per year. Specifically, the proposed research will probe molecular mechanisms responsible for different types of fracture-like failure (technically known as melt fracture) that occur during processing of these materials. Strategies based on molecular engineering will be developed to reduce or remove melt fracture to improve the mechanical performance of these materials. Various experimental methods will be applied to elucidate true physical origins of rupture-like failures related to 1) yielding and failure in simple shear by studying their dependence on molecular composition, 2) surface melt fracture using a new experimental design as a function of molecular formulation, 3) entry material instability to be investigated with particle-tracking velocimetry and correlated with gross melt fracture.
The mechanical failure of molten plastics has long prevented more efficient making of such common items as milk bottles, grocery bags, clothing (fibers), car bumpers, automobile tires and microelectronic circuitry boards. Results from the proposed activities may produce practical solutions to postpone or remove melt fracture in manufacturing so that many plastics articles can be made at a faster speed and lower energy cost. Akron Global Polymer Academy (www.agpa.uakron.edu/nn-scied-researchfeatures.html) provides the infrastructure to allow access to regional high school teachers and students. Six movies from previous research have recently been uploaded onto YouTube.com and received over five hundred hits (key word: Polymer Rheology).
