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

Answer 1

The Correct Option is B

The correct option is (B): Anti-thixotropic.

Answer 2

Rheological (flow) behaviors are grouped as time-independent, where shear stress depends only on the current shear rate, or time-dependent, where the material's structure also changes with how long shearing continues. The question asks which of the four listed behaviors is the exception, meaning it is time-dependent rather than time-independent.

1. Plastic: Plastic (Bingham) flow needs a yield stress to be crossed before flow starts, but once that point is crossed, the shear stress at a given shear rate stays consistent regardless of how long shearing continues. This makes it a time-independent flow type.
2. Anti-thixotropic: Anti-thixotropic behavior, also called rheopexy, is defined by viscosity that increases the longer and harder a fluid is sheared, then only slowly recovers once shearing stops. Because the material's resistance to flow changes with the duration of shearing itself, this is a time-dependent behavior, not a time-independent one.
3. Pseudoplastic: Pseudoplastic (shear-thinning) flow shows viscosity dropping as shear rate rises, but at a fixed shear rate the viscosity stays constant no matter how long shearing continues. This makes it time-independent.
4. Non-newtonian: This is a broad umbrella term for any fluid whose viscosity is not constant with shear rate. Plastic and pseudoplastic flow, both time-independent, fall under this same non-Newtonian umbrella, so as a general category it groups with the time-independent types listed here rather than standing apart from them.

Since plastic and pseudoplastic flow only depend on shear rate, and non-Newtonian is the broader category that includes them, anti-thixotropic is the one behavior on the list defined specifically by a change over the duration of shearing.

The correct answer is Anti-thixotropic.