On intrinsic errors in pressure‐hole measurements in flow of polymer melts

Abstract

AbstractIn order to investigate the possibilities of pressure‐hole errors in the measurement of wall normal stresses in the flow of polymer melts, a 2.280‐in. long slit die has been designed, having a slot with a rectangular cross section, 0.050 in. by 1.000 in. Three transducers were mounted on each of the two long sides of the rectangular slot along the longitudinal center line of the die and located so that each transducer was directly opposite another in the opposite side. The three transducers on one side were flush mounted. Those on the other side were mounted through pressure‐holes with different diameters (0.017, 0.034, and 0.050 in.) Measurements of wall normal stresse were made with high density polyethylene and polypropylene melts at 200°C., following the experimental procedure described in the author's earlier papers. The present study indicates that pressure measurements made through pressureholes are essentially the same as those made flush‐mounted instruments, and that there are no pressure hole errors in the measurements of wall normal stresses, insofar as polymer melts are concerned.