ASTM  D5225 Measuring Solution Viscosity of Polymers with a Differential Viscometer

Scope:

The ASTM D5225 test method specifies the use of a differential or modified differential viscometer to determine the solution viscosity of polymers. This test is applicable to all polymers that dissolve entirely without a chemical reaction or degradation, forming stable solutions over time and temperature. All types of synthetic polymers, biopolymers, proteins, and peptides can be measured using the differential viscometer utilized in the test. The ASTM D5225 test method also allows for quick viscosity characterization of polymers.

Procedure:

The ASTM D5225 test is carried out with a balanced network of four capillaries organized in a  Wheatstone bridge-like pattern. Pure solvent flows via a balanced capillary network at constant inlet pressure P_i, resulting in a zero or baseline pressure on the differential pressure transducer.  Sample reservoir A is filled with the solution, which is subsequently injected onstream via the switching valve S_A. The differential pressure rises until it reaches a steady-state value of ∆P, which is proportional to the solution’s particular viscosity. On a strip chart recorder or computer,  the differential pressure is continuously monitored, providing a baseline against which ∆P is recorded.

Specimen size:

For ASTM D5225 test procedure, the polymer is used as a test specimen.

Data : 

Results of the ASTM D5225 test are usually expressed as specific viscosity, intrinsic viscosity,  inherent viscosity, or relative viscosity. 

According to ASTM D5225, polymer solution viscosity is proportional to the average molecular size of the polymer component that dissolves in the solvent.

Conclusion:

The ASTM D5225 test method specifies the use of a differential or modified differential viscometer to determine the solution viscosity of polymers.