Shear stress and normal stress measurements of aqueous polymer solutions in a cone-and-plate rheogoniometer |
| |
Authors: | P -J Klijn J Ellenberger J M H Fortuin |
| |
Institution: | (1) Laboratory of Chemical Technology, University of Amsterdam, Plantage Muidergracht 30, Amsterdam, The Netherlands |
| |
Abstract: | Summary The rheological behaviour of aqueous solutions of Separan AP-30 and Polyox WSR-301 in a concentration range of 10–10000 wppm is investigated by means of a cone-and-plate rheogoniometer. The relation between the shear stress and the shear rate is for lower shear rates characterized by a timet
0, which is concentration dependent. Both polymers show for 4000 s–1 <
< 10000 s–1 a behaviour similar to that of a Bingham material, characterized by a dynamic viscosity
0 and an apparent yield stress
0, which also depend on the concentration. The inertial forces are measured for water and some other Newtonian liquids. An explanation is given why the theoretical model developed for these forces does not match the experimental values; the shape of the liquid surface is shear rate dependent. To obtain the first normal stress difference, we have to correct for these inertial forces, the surface tension and the buoyancy. The normal forces, measured for Separan AP-30, appear to be a linear function of the shear rate for 350 s–1 <
< 3300 s–1.
Zusammenfassung Das rheologische Verhalten wäßriger Polymerlösungen von Separan AP-30 und Polyox WSR-301 wird in einem Konzentrationsgebiet von 10–10000 wppm in einem Kegel-Platte-Rheogoniometer untersucht. Der Zusammenhang zwischen Schubspannung und Schergeschwindigkeit wird für niedrige Schergeschwindigkeiten durch eine konzentrationsabhängige Zeitt
0 gekennzeichnet. Für Schergeschwindigkeiten 4000 s–1 <
< 10000 s–1 zeigen beide Polymere ein genähert binghamsches Verhalten, gekennzeichnet durch eine dynamische Viskosität
0 und eine scheinbare Fließgrenze
0, welche ebenfalls konzentrationsabhängig sind. Die Trägheitskräfte werden für Wasser und einige newtonsche Öle bestimmt. Die Abweichung der experimentellen Ergebnisse vom theoretischen Modell wird durch die Abhängigkeit der Gestalt der Flüssigkeitsoberfläche von der Schergeschwindigkeit erklärt. Um die Werte der ersten Normalspannungsdifferenz zu erhalten, muß man bezüglich der Trägheitskräfte, der Oberflächenspannung und der Auftriebskräfte korrigieren. Die Normalspannungen für Separan AP-30, gemessen für 350 s–1 <
< 3300 s–1, zeigen eine lineare Abhängigkeit von der Schergeschwindigkeit.
c
concentration (wppm)
-
g
acceleration of gravity (ms–2)
-
K
force (N)
-
K
b
buoyant force (N)
-
K
c
force, acting on the cone (N)
-
K
0
dimensional constant def. by eq. 24] (N)
-
K
s
force, def. by eq. 22] (N)
-
M
dimensional constant def. by eq. 24] (Ns)
-
P
s
pressure def. by eq. 17] (Nm–2)
-
P
0
average pressure in the liquid atr = 0 (Nm–2)
-
P
R
average pressure in the liquid atr = R (Nm–2)
-
r
1,r
2
radii of curved liquid surface (m)
-
R
platen radius (m)
-
R
w
radius of wetted platen area (m)
-
S
x
standard deviation ofx
-
t
0
characteristic time def. by eq. 1] (s)
-
T
temperature (°C)
-
V
volume of the submerged part of the cone (m3)
-
v
tangential velocity of liquid (ms–1)
-
x
distance (m)
-
angle (rad)
-
0
cone angle (rad)
-
calibration constant (Nm–3)
-
shear rate (s–1)
-
dynamic viscosity (mPa · s)
-
0
viscosity def. by eq. 1] (mPa · s)
-
contact angle (rad)
-
density (kgm–3)
-
static surface tension (Nm–1)
-
shear stress (Nm–2)
-
0
yield stress def. by eq. 1] (Nm–2)
-
c,
p
angular velocity (c = cone,p = plate) (s–1)
With 8 figures and 3 tables |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|