Temperature dependence of mechanical shear degradation

Abstract

The rate of mechanical shear degradation of a 10% solution of Vistanex B‐100 polyisobutene (viscosity‐average molecular weight 1,740,000) in cetane has been studied at 60 and 80°C. at high rates of shear. The rate constants for the reaction at a given rate of shear energy application are found to decrease with temperature in this range. This result is interpreted as arising from a decreased efficiency at higher temperatures in the process of temporarily concentrating mechanical energy by means of intermolecular entanglements. The energy input requirements for degradation are found to increase with temperature.

Mechanochemistry in Thermomechanical Processing of Foods: Kinetic Aspects

“…Analogously with the development of the Arrhenius rate equation from a Boltzmann distribution of thermal energy, has been developed from a Boltzmann distribution of mechanical energy to model polymer degradation in a shear field (Goodman and Bestul 1955): where k S is the reaction rate constant for the shear‐induced degradation and k S0 is a constant analogous to k T0 in the Arrhenius equation. E S is shear activation energy.…”

Zur Messung des Fließverhaltens von Polymerlösungen im Bereich hoher Scherbeanspruchung

“…Im Gegensatz zu anMogen bekannten Erscheinungen des Abbaus yon Hochpo]ymeren dureh UltrasehM1, Temperatur oder Strahlung liegen ffir den Abbau durch Scherung wenig experimentelle Belege und Ergebnisse vor (7,8,9,10). das hohe Geschwindigkeitsgef/ille ffihren zu einer meehanisehen Beanspruchung des Polymermolekfils, die ein ZerreiBen der Kette, d. h. einen Molekulargewichtsabbau bewirken kann.…”

Thermomechanochemical depolymerization of dextrans in aqueous phase

“…The energy required for polymer degradation is composed of at least two components: the energy required to cause viscoelastic flow and the energy required to break chemical bonds. 15 In turn, the free energy, which can activate the bond rupture, is composed of two terms: entropy of deformation and potential energy, the latter being the only term contributing to bond scission. 16 Threemninmwhamsms may occur depending on the nature of the chemical bonds as well as the solvent.…”