Atypical temperature and composition influence upon rheology of aqueous glues and coating colours

   Formerly we observed a complicated shape of viscosity temperature curves of some aqueous glues and coating colours having one or more peaks, i.e. with one or more maximums and minimums. The viscosity - temperature behaviour of these mixtures changes significantly with any change in their composition and depends on shear rate as well. It was observed temperature and composition influence upon rheology of aqueous glues and coating colours. This behaviour is observable not only in mixtures containing starch or starch derivates.  

viscosity coefficient upon temperature

   This anomalous behaviour is possible explained only by means of concept the hydration bonding system among interacting particles of dispersion. It seems that both the concentration and the composition play important role in temperature flow behaviour of these concentrated hydrated hydrophilic systems but the complicated temperature dependences are determined by amount, character and strength of bonds in three-dimensional structure among sites at interacting hydrated hydrophilic phase interfaces of components thus forming coating colours and glues.  The explanation of this phenomenon is based on relative simple idea of mosaic type of nano-sites distribution on interacting planes consisting of two types of qualitatively different sites.  Both sorts of nano-sites have a common property their behaviour strongly depends upon temperature. The system achieves a minimum potential energy if attractive forces prevail between interacting planes and a maximum if only repulsive forces exist. At dynamic conditions, when the mutual movement of interacting planes is controlled, the resulting potential energy of steady state is defined by the prevailing force action. At a constant composition of surfaces, they are given by temperature and distance between interacting planes, i.e. by the concentration of interacting nano-sites. The effect of hydration forces belongs among the physical or colloidal intermolecular forces and depends strongly upon temperature. They disappear with rising temperature, but at equal conditions, the repulsive forces are effective over a greater distance. These differences appear important during interactions of surfaces in which repulsive and attractive hydration forces are affected simultaneously. As model predicts, at this situation may exist a temperature at which prevailing attractive forces are functioning whilst at another temperature prevail repulsive hydration forces.

Schematic representation of isopotentials around interacting particles of mosaic type distribution of hydration forces activity an influence of temperature.

 isopotentials around interacting particles


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