A Brookfield Viscometer measures a fluid’s viscosity at given shear rates. Fluids measured can be of polymers in solutions, oils, etc. The viscometer uses a rotating spindle that is inserted into a glass container to measure the fluids resistance to flow through torque on the spindle. Torques from samples are compared to known standards to determine the fluid viscosity. Multiple samples are measured to ensure accuracy.
ISO 1628, ASTM D4603
ISO 1628 ASTM D4603
ISO 1628 gives a general procedure for determining the viscosity of polymer solutions using an Ubbelohde viscometer and ASTM D4603 gives the method for determining the inherent viscosity of polyethylene terephthalate (PET).
The Ubbelohde viscometer is a U-shaped capillary tube viscometer that is used to measure the viscosity of a dilute solution. The amount of time it takes for the solution meniscus to drop from the upper mark on the tube to the lower-level mark is known as the flow time. This time is used to determine the viscosity of the solution. The reduced viscosity is calculated and plotted against the concentration of different polymer solutions and regression is used to determine the intrinsic viscosity.The intrinsic viscosity is an important value as it can be correlated to the molecular weight of a polymer using the Mark-Houwink equation.