Thixotropic Index (TI)

Definition - What does Thixotropic Index (TI) mean?

This is a ratio between the slow speed viscosity to the high speed viscosity of a non-Newtonian body. It is obtained from dividing the viscosity number at low speed by the viscosity number at high speed of a given fluid. It therefore defines how well the fluid will hang or resist sagging under gravity.

It is used to indicate the ability of a paint or coating to hold shape-stiff and non-sagging when rebuilding; aids in choosing an epoxy in accordance to the application, dispense method and viscosity of a material.

Corrosionpedia explains Thixotropic Index (TI)

Non-Newtonian fluids are known to have a low viscosity when stirred at high speed and high viscosity at low speeds. In these fluids, the energy required to move then is not directly equal to the speed applied. At rest, the fluid will not flow, but when subjected to shear or pressure, it flows easily as the agitation increase. A fluid is thixotropic when the apparent viscosity is recovered when the shearing is removed; the recovery is time-dependent—viscosity decreases gradually with time.

The thixotropic index is obtained by measuring the viscosity of a fluid at room or ambient temperature. The viscometer is used to measure the viscosity at two speeds (one is a multiple or a factor of 10 of the other). From the viscosity results, the product is obtained by dividing the viscosity at lowest speed by the viscosity at the highest speed.

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