LCR7000 & RHEOSIGHTS P/N: 974194 |
Rev: A
|
ECO: 52468
www.dynisco.com
From lab to production,
providing a window into the process
-65-
Apparent Shear Stress:
Where:
= shear stress
F
= force acting on surface area
A
.
F
p= force on the plunger
rc = radius of the capillary
Dc= diameter of the capillary
Rb= radius of the barrel
Lc =
length of the capillary
∆
P
= pressure drop across the capillary
Apparent Shear Rate:
γ
π
=
=
32Q
Dc
3
4R b
2S
rc
3
Where:
γ
= shear rate
S
= speed of the plunger
Q = volumetric flow rate
Using the above expressions for shear stress and shear rate the viscosity reduces to the
equation shown above. Physically the viscosity is proportional to the force on the plunger
divided by the speed of the plunger. As can be seen in the equation, viscosity is strongly
dependent on barrel and die radius.
τ
π
=
=
=
F
A
D
P
4 L
F r
2 R L
c
c
p c
b
2
c
∆
τ
η
π
=
F
S
c
b
c
r
R L
4
4
8
