Effect of molecular weight on secondary Newtonian plateau at high shear rates for linear isotactic melt blown polypropylenes

Effect of molecular weight, branching and temperature on dynamics of polypropylene melts at very high shear rates

“…Polymer melts in these processes are typically exposed to very high shear rates (10 6 -10 7 1/s) [1][2][3][4][5]. There are only a few papers reporting shear viscosity measurements for polymer melts at such extreme shear rates utilizing specially designed rheological equipment such as hydraulically powered capillary rheometers [6] or instrumented injection molding machines [7][8][9][10][11]. Recent studies on entangled linear polypropylene melts have shown a well-developed Newtonian regime occurs above 2 • 10 6 1/s, which is linearly dependant on molecular weight suggesting that polymer chains become fully disentangled in such a flow regime [11].…”

“…There are only a few papers reporting shear viscosity measurements for polymer melts at such extreme shear rates utilizing specially designed rheological equipment such as hydraulically powered capillary rheometers [6] or instrumented injection molding machines [7][8][9][10][11]. Recent studies on entangled linear polypropylene melts have shown a well-developed Newtonian regime occurs above 2 • 10 6 1/s, which is linearly dependant on molecular weight suggesting that polymer chains become fully disentangled in such a flow regime [11]. In order to understand the role of the chain branching and temperature on high shear rate dynamics of polypropylene melts, well characterized low molecular weight linear PP Borflow HL512FB (L-PP) [11] and high molecular weight branched PP Daploy WB180HMS (LCB-PP) [12], both produced by Borealis Polyolefine (Linz, Austria), have been used in this work.…”

“…Recent studies on entangled linear polypropylene melts have shown a well-developed Newtonian regime occurs above 2 • 10 6 1/s, which is linearly dependant on molecular weight suggesting that polymer chains become fully disentangled in such a flow regime [11]. In order to understand the role of the chain branching and temperature on high shear rate dynamics of polypropylene melts, well characterized low molecular weight linear PP Borflow HL512FB (L-PP) [11] and high molecular weight branched PP Daploy WB180HMS (LCB-PP) [12], both produced by Borealis Polyolefine (Linz, Austria), have been used in this work. Polymer blends were prepared by adding 10, 20 and 30 wt% of LCB-PP to L-PP in a twin screw extruder.…”

“…These systems are miscible for blends containing up to 50 wt% LCB-PP [13][14][15][16][17]. High shear rate rheology was conducted at 190, 210 and 230 o C on a high accuracy Fanuc Roboshot S-2000i electric high-speed injection molding machine in air-shot mode using an instrumented rheometric capillary die nozzle under processing conditions, in which the effect of viscous dissipation and pressure is mutually cancelled [11]. A capillary die of 8 mm length and diameter 0.5 mm as well as an orifice die of the same diameter were used to enable Bagley and Weissenberg-Rabinowitsch corrections.…”

Numerical simulation of gas‐assisted polymer‐melt electrospinning: Parametric study of a multinozzle system for mass production

“…We assumed polypropylene melt as Newtonian fluid at given process condition because the shear rate at the process is in range of Newtonian plateau (Figure S1B). [ 35 ]…”