THIXOTROPY (Greek thixis a touch + trope turn) — reversible isothermal transformation of nek-ry gels, jellies or pastes into a liquid (fluid) state at mechanical influence (hashing or stirring) or at action of ultrasound. K T. refer also reversible decrease viscosity (see) solutions of high-molecular compounds, napr, solutions of proteins (see), at their hashing. Turning out as a result of T. sols (see), solutions of high-molecular compounds (see) or concentrated suspensions (see) through a nek-swarm time called by the thixotropic period lose flowability and again harden. Process firm system <-> liquid is reversible and can repeatedly repeat. T. cytoplasm of cells, a plasmolemma of muscle fibers, a blood plasma, a lymph, an intercellular lymph possesses. Thixotropic systems are many food stuffs (curdled milk, kefir, jelly, etc.).
Phenomenon of T. explain with the fact that particles of thixotropic systems, usually asymmetric in a form, are connected with each other in separate points in spatial structures (grids, frameworks) by weak van-der-vaalsovymi by forces (see. Molecule ). These structures easily collapse at mechanical influences, but are at rest recovered as a result of coupling of particles among themselves that is promoted by their thermal agitation. In nek-ry cases slight mechanical attachment, napr, slow rotation of colloid solution, promotes structurization. This phenomenon is called a reopeksiya.
Bibliography: Voyutsky S. S. Course of colloid chemistry, M., 1975; Friendlich G. A thixotropy, the lane with English, M., 1939.
V. P. Mishin.