Question

Based on the rheological behavior of fluid, all of the following shows time independent property, except:

• A. Plastic
• B. Anti-thixotropic
• C. Pseudoplastic
• D. Non-newtonian

Hint:

Anti-thixotropic fluids become thicker with time under constant shear, unlike time-independent fluids like plastic and pseudoplastic, which maintain a consistent flow behavior.

Answer 1

The Correct Option is B

The key test for telling time-independent from time-dependent flow is whether letting the material sit under constant shear for longer changes its viscosity. Applying that test to each option below identifies the exception.

1. Plastic: Once a plastic system's yield stress is exceeded, its resistance to flow at a given shear rate is fixed and does not shift with how long the shear is maintained, so it belongs in the time-independent group.
2. Anti-thixotropic: This behaviour is specifically about viscosity climbing as shear is held constant over time (and slowly relaxing back once shear stops), which means time itself, not just shear rate, is a variable that changes the response. This is what makes it time-dependent rather than time-independent.
3. Pseudoplastic: The shear-thinning response of a pseudoplastic material depends only on the shear rate applied at that instant, and holding the shear constant for a longer period does not change the viscosity further, so it is a time-independent type.
4. Non-newtonian: As a general label for fluids that do not follow a straight-line shear stress to shear rate relationship, non-Newtonian includes plastic and pseudoplastic behaviour, both time-independent, so the term as a category groups with the time-independent set here.

Since anti-thixotropic is the only one of the four where viscosity itself changes with the duration of shearing, the correct answer is Anti-thixotropic.