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Observation of the Cavitation Phenomena Upon the Gross Melt Fracture Regime in LLDPE Extrusion



Y Son, Kalman D. Migler


We present observation of a cavitation phenomenon inLLDPE eaxtrusion. In the gross melt fracture regime, cavitation was always observed in the first 0.5 mm to 1.5 mm upstream of the exit. We saw cavities at the wall form (seemingly out of nothing) to grow to a length and width of about 150 [mu]m, then shrink down and disappear. From the velocity measurements of these structures, we conclude that their width in the radial direction is much smaller than those in the axial and lateral direction and that they are in contact with the wall. The process for the growth and disappearance is approximately 20 ms to 25 ms. The shape of the cavities is highly irregular. From several precise investigations, we concluded that the unstable flow and melt fracture in the entrance region is main source for the cavitation phenomenon, and the cavitation was initiated from the unstable flow by the extensional flow at the die exit.
ANTEC Conference Proceedings


cavitation, extrusion, gross melt fracture, microscopy


Son, Y. and Migler, K. (2002), Observation of the Cavitation Phenomena Upon the Gross Melt Fracture Regime in LLDPE Extrusion, ANTEC Conference Proceedings, [online], (Accessed July 18, 2024)


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Created April 30, 2002, Updated October 12, 2021