Solid bed compaction and frictional drag during melting in a simulated plasticating extruder

Abstract

Solid bed transport has an important effect on the overall performance of a plasticating extruder. The coefjicient of friction and density are the properties of the solid bed that govern its transport in the feed section of the screw. These properties have been measured, as

Friction of Nonwoven Wood–Polypropylene Fiber Mats on Heated Steel Platens

“…Table 1 provides the means and ranges for the values of k for the nonwoven mats at the different PP and normal stress levels. The values in Table 1 includes the data for the different temperature levels and dwell [12] and Gang et al [20] for solid PP. The frictional response of the mats with no PP fibers was substantially lower than the values in the literature [7][8][9].…”

“…Friction values obtained for PP by Hwang and McKelvey[12] ranged from 0.05 to 0.15 at similar normal stress and temperature ranges. Gang et al[20] found k for PP to drop to 0.017-0.021 at a higher temperature of 210 C. For solid wood, k was found to be between 0.10 and 0.13 at Representative frictional load curve for nonwoven mats at a surface temperature of 180 C, a 7.6-MPa normal load, and a 0-s dwell time.…”

“…As the temperature exceeds T g to achieve a rubbery phase, k increases as the polymer conforms to the minute structure of the rigid surface. At this temperature range, the shear stress of the polymer () is greater than i [12]. As the polymer exhibits a viscous behavior, decreases with increasing temperature to a stress below i .…”

Friction and its effect on the mechanical‐ to‐thermal energy conversion during extrusion of poly(vinylidene chloride)

“…Matching test conditions with extruder conditions is very important. The COF of a polymer will vary in some instances rapidly with small changes in temperature, pressure, and velocity as evident from the experimental work of many studies (3)(4)(5)(6)(7)(8)(9)(10). This is because the nature of the interface changes as the sample deforms and approaches (or exceeds) its melting or glass transition temperature.…”

“…As will be detailed further in the Experimental section, the apparatus used in this work consists of a rotating drum with the polymer impinged on this drum through the use of a sample chamber and plunger. Other designs used to study friction under extruder like conditions include a cylindrical chamber with a piston that applies pressure and also can measure torque while it rotates (8). an apparatus of similar geometry to the present work except a smaller diameter cylinder is used (9).…”