Relation between Steady-Flow and Dynamic Viscosity for Polyethylene Melts

Anomalous nonlinearities in steady shear of polyethylene melts

High-density polyethylene (HDPE) melts have been previously identified as having an unusually high degree of molecular order, but the rheological implications of this have heretofore not been explored. This has been a serious oversight, inasmuch as HDPE melt processing is one of the major tasks of the world's polymer industry. Here, we investigate several industrial samples of HDPE, covering a ...

Viscosity models for silicate melts

Rheology of silicates (melts or super cooled as glasses) is one of the most important fields to mankind, as geological activity largely influences life. In this paper, unifying empirical models for the Non-Newtonian shear viscosity and the extensional viscosity are proposed. The models have only one parameter, the zero shear viscosity (the Newtonian plateau), and are valid for a vide range of c...

Viscosity and Anelasticity of Melts

is the Maxwell relaxation time [24]. This relaxation time is a convenient approximation to the timescale of deformation where the transition from purely viscous behavior to purely elastic behavior occurs. The purely viscous response of a silicate melt is termed “liquid” behavior whereas the purely elastic response is termed “glassy” behavior. The term silicate melt is used to describe molten si...

Nonlocal constitutive relation for steady granular flow.

Extending recent modeling efforts for emulsions, we propose a nonlocal fluidity relation for flowing granular materials, capturing several known finite-size effects observed in steady flow. We express the local Bagnold-type granular flow law in terms of a fluidity ratio and then extend it with a particular Laplacian term that is scaled by the grain size. The resulting model is calibrated agains...

Viscosity overshoot in the start-up of uniaxial elongation of low density polyethylene melts