ASTM D1823 test is used for measuring plastisol and organosol viscosity at high shear rates with the help of an extrusion viscometer. This test is used for defining the flow behavior of plastisol or organosol under high shear. The viscosity depicts the parameters encountered in roller coating, pumping, knife coating, mixing, and spraying processes. Viscosity characteristics define the suitability of a dispersion resin for any specified application.
For the ASTM D1823 test, the rheometer is set up and attached to the pressure regulator to the nitrogen tank. The nitrogen supply is connected to the rheometer with the help of copper tubing.
The tank pressure is regulated to provide 1.04 MPa (150 psi) pressure to the device. The test sample is then conditioned to the required temperature. After that, the test is placed into an extrusion chamber and extruded under typical parameters. The viscosity is determined by the extrusion pressure and the flow rate through the orifice.
The sample size used is as specified by ASTM D1823.
The shear stress, shear rate, and viscosity are calculated as:
Shear stress, MPa (or psi) = PR/2L
P = pressure in a rheometer, MPa (or psi),
R = radius of the orifice, cm (inches), and
L = length of the orifice, cm (inches)
Shear rate, s-1=4W/3.1416R3DT
W = weight of material effluxed, g,
D = density of sample g/ml, and
T = efflux time, s
Viscosity, pascal seconds = (shear stress/shear rate)106 (In terms of MP a)
Viscosity, poises = (shear stress/shear rate) x 6.895 x 104 (In terms of psi)