prDS CEN ISO/TR 20659-2:2024

Metodat e provës reologjike - Bazat dhe krahasimet ndërlaboratorike - Pjesa 2: Përcaktimi i ndryshimit strukturor të varur nga koha (tiksotropia) (ISO/TR 20659-2:2024)

Rheological test methods - Fundamentals and interlaboratory comparisons - Part 2: Determination of the time-dependent structural change (thixotropy) (ISO/TR 20659-2:2024)

Scope

This document gives information on an interlaboratory comparison for the determination of the time-dependent structural change (thixotropy) using rheological test methods. Thixotropy is the reversible, time-dependent decrease of shear viscosity η at a constant shear rate or shear stress τ.
This document provides examples of fields of application, in which important material properties can be characterized by the thixotropy. These fields of application include:
—     effectiveness of rheological additives and thixotropic agents, respectively;
—     stability of the structure at rest (e.g. behaviour when starting to pump);
—     wet film thickness after processing;
—     levelling and sagging behaviour (e.g. without brushmarks or sag formation);
—     orientation of effect pigments.