Edit1992 Coefficients of Dynamic Friction as a Function of Temperature, Pressure, and Velocity for Several Polyethylene Resins
Mark A. Spalding and K. S. Hyun - The Dow Chemical Company
EditIntroduction
In a plasticating extruder, the coefficient of dynamic friction is in many cases the controlling factor for solids conveying, pressure generation, thermal decomposition of the resin, and flow surging. The coefficient of friction is, however, very poorly understood and very difficult to measure. Moreover, interpretation of experimental data are complicated by the dissipation of frictional energy at the sliding interface. This energy flux at the interface makes it extremely difficult to determine the coefficient as a function of temperature, pressure, and velocity at conditions of extrusion.
A new fricition-measuring device has been designed and fabricated based on a first generation machine built at Rensselaer Polytechnic Institue by C. I. Chung (1,2). The unit is capable of studying forces, resulting from frictional and viscous drag, on a small plug of polymer at conditions typical of extrusion. With this equipment and a numerical technique for computing the interface temperature, the coefficients can be measured as a function of temperature, pressure, and velocity.
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