Brookfield Measurement of Viscosity

Viscosity is the property of resistance to flow exhibited within a body of material at a given shear rate. In Brookfield viscometer measurements, flow behavior is an indirect measure of product consistency and quality, where materials need to be consistent from batch to batch. Furthermore, molded parts can be compared to the original resin to determine the degree of degradation resulting from the molding process, as the viscosity of the reduced material will be lower as a result of the decrease in molecular weight. Because flow behavior is sensitive to molecular weight distribution, this is a precise method for material characterization.

When measuring with a Brookfield viscometer, formic acid is placed in an eight-ounce screw-cap flask filled with 22.0 grams plus/minus 0.01 grams of polymer. It is shaken in a shaker until all of it is submerged in the nylon solution, then placed in a 25-degree bath for no less than one hour. The prepared solution is then placed in the Brookfield viscometer, and an appropriate speed is selected according to the expected viscosity of the sample. The Brookfield viscometer determines viscosity by measuring the force required to rotate the shaft in the solution at a specific rate. Relative viscosity is calculated by dividing the absolute viscosity of the nylon/formic acid solution by the absolute viscosity of the formic acid.

The two standards based on this subject are the following two standards developed by the American Testing and Materials Organization (ASTM):

• ASTM D789-19 Standard test method for determining the relative viscosity of concentrated polyamide (PA) solutions. This test method applies to concentrated solutions of polyamide (PA) and includes the determination of relative viscosity. This test method does not consider viscosity measurements derived from measurements with dilute solutions.
• ASTM D4878-08 Standard test methods for polyurethane raw materials: determination of viscosity of polyols. Test methods A and B described in this standard determine the viscosity of polyols in the range of 25 to 50 mPa at 10 degrees or 100.000 degrees. Test method A also applies to more viscous samples that are soluble in n-butyl acetate. Test method B is a reference to the ASTM D445 standard, which is a general procedure for kinematic viscosity.

Briefly, Brookfield viscometers use the well-known principle of rotational viscometers. It measures viscosity by sensing the torque required to rotate a shaft at constant speed while immersed in the sample fluid.

Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides viscosity Brookfield measurement services with its trained and expert staff and advanced technological equipment.