Design of an orifice die to measure entrance pressure drop

Evaluation of temperature-strain rate dependent uniaxial and planar elongational viscosities for branched LDPE polymer melt

“…The elongational viscosity represents key rheological parameter allowing understanding the molecular structure of the polymers as well as polymer processing at which the polymer melts are stretched [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Due to the fact that generation and control of the extensional flow is difficult, experimental determination of the elongational viscosity is a problem [17][18][19][20].…”

Planar Extensional Viscosity Measurements for LDPE Polymer Melt by Using Novel Orifice Die Design and Cogswell Model

“…Due to the fact that generation and control of the extensional flow is difficult, experimental determination of the extensional viscosity is a problem [1][2]. Different types of experimental techniques have been developed [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] to measure this very important property but each of them is applicable for only limited range of extensional rates or stresses. Probably the most challenging rheological task is experimental determination of planar extensional viscosity as one can see from very small numbers of experimental data available in the open literature [1][2][12][13][14][15][16].…”

Development of Novel Orifice Die Design for Precise Entrance Pressure Drop Measurements

“…It should be mentioned that the extensional viscosity of the polymer melt is much more difficult to measure in comparison with the shear viscosity [1]. In the open literature, several types of extensional rheometers and experimental techniques have been developed [1][2][3][4][5][6][7][8][9] to measure this very important property. However each of them is applicable for only limited range of extensional rates or stresses and the low experimental error can be observed only in the case when the elongation flow is stable for a sufficient time for large enough volume of the sample.…”

“…However each of them is applicable for only limited range of extensional rates or stresses and the low experimental error can be observed only in the case when the elongation flow is stable for a sufficient time for large enough volume of the sample. Interestingly, the only available experimental technique to determine extensional viscosity at high extensional strain rates is based on the entrance pressure drop measurements [1,[5][6][7][8][9] by using capillary rheometers (see Figure 1). The use of an orifice die for entrance pressure drop measurements is very attractive methodology because it minimizes errors due to pressure dependence of viscosity, wall slip and viscous heating which can occur during alternative extrapolation based Bagley plot approach.…”

“…The use of an orifice die for entrance pressure drop measurements is very attractive methodology because it minimizes errors due to pressure dependence of viscosity, wall slip and viscous heating which can occur during alternative extrapolation based Bagley plot approach. On the other hand, Kim and Dealy [8] recently pointed out that entrance pressure drop measurements can be highly erroneous by using orifice dies for the cases when orifice die exit section is wetted by the polymer melt. With the aim to overcome this conventional orifice die weakness, the theoretical and experimental flow analysis has been performed to obtain novel improved orifice die design.…”