KIW´s Veröffentlichen

Journal of Macromolecular Science, Part B. Physics. 2018. "Prediction of the Creep of Elastomers Taking into Account the Forces of Entropie Elasticity of Macromolecules (Prediction of Creep of Elastomers)"

V. I. Kartsovnik (2018)
The Society of Sciences & Engineering Registered Community "KIW-Gesellschaft e.V.", Dresden, Germany /
http://doi.org/10.1080/00222348.2018.1470836

Accounting for the increase in the energy of activation of viscous flow of polymers by an amount proportional to the force of entropic elasticity of the stretched macromolecules, allows for a quantitative description of the curves of deformation of elastomers in the models of Kelvin Voigt and the Standard linear solid. For these models, application of a rubber like elasticity modulus, increasing with the increase of deformation, enables cakulation of Flory's correction factor for the network defects for the deformation curves of a rubber. The curves of creep of Silicone rubbers under constant load for various temperatures were measured. For the Kelvin Voigt model differential equations the dependence of the coefficients of linear approximations of these equations on loadings and temperatures were measured. The possibility to predict the time of achieving given creep values based on the proposed Kelvin Voigt model equations were demonstrated.

ARTICLE HISTORY

Received 6 November 2017. Accepted 19 April 2018

Key words:

Activation energy; creep of rubbers; Eyring’s viscosity theory; Kelvin-Voigt model; Prediction of creep: Rubber- like elasticity modulus. Weiterlesen ...

Journal of Macromolecular Science, Part B. Physics. 2016. Vol. 55, Nr. 2, S.149-157
"Calculation of the Viscosity of Polymer Melts Based on Measurements of the Recovered Rubber-Like Deformation"

V. I. Kartsovnik, R. Worlitsch, F. Hermann, and J.Tsoglin /
The Society of Sciences & Engineering Registered Community "KIW-Gesellschaft e.V.", Dresden, Germany /
RHE0TEST Medingen Ltd., Ottendorf-Okrilla, Germany
http://dx.doi.org/10.1080/002223482015.1119340

On the basis of a model of polymer flow, considering the forces of entropic elasticity of extended macromolecules within the Eyring's concept, the relationships between the shear rate, shear stress, viscosity, and recovered rubber-like deformation were derived. The reduction of activation energy of the flow, by an amount proportional to the recovered rubber-like deformation, leads to an exponential decrease of viscosity with increasing shear rates; this nonlinear dependence of viscosity on shear rate (and shear stress) is defined as the viscosity anomaly of polymers. The measurement of deformation recovery alter the cessation of polymer flow in the mode of constant shear rate or shear stress on a rotational viscometer confirmed the validity of the theoretical dependences.

Key words:

Activation energy; Entropic elasticity of macromolecules; Eyring's theory of viscous flow; Recovered rubber-like deformation; Viscosity anomaly. Weiterlesen ...

Journal of Macromolecular Science, Part B. Physics

Based on a simple molecular model, a mechanism of rubber flow characterized by viscosity increasing with the reversible rubber-like deformation is proposed. It is associated with an activation energy of viscous flow that increases proportionally to an external stress due to the entropy elasticity of macromolecules. This increase of the activation energy for jumping of molecular-kinetic units of a polymer network into vacancies during the rubber deformation process is caused by an increasing resistance of the stretching macromolecular network due to the entropy nature of macromolecule deformation.

Keywords:

Activation energy, entropic elasticity, Eyring's viscosity theory, polymer network, rubber deformation, standard inear solid. Weiterlesen ...

Abstract:

A non-Newtonian flow of a polymer melt is discussed. The description of the exponential decrease of the apparent viscosity by the well-known Eyring formula with an activation energy reduction proportional to the shear stress does not take into account specific features of the polymeric structure. We propose to modify the description of the macromolecular flow mechanism by including conformational changes of the polymeric chains. The elasticity of a strained polymeric chain, having an entropy origin, can be the reason of the reduction of the activation energy for the transition of a molecular-kinetic unit of the chain into a new equilibrium state in the flow direction during the thermal fluctuations. In that case, the activation energy of the transition should decrease by a value proportional to the reversible high-elastic component of the shear deformation caused by the flow of the polymer.

Dr. rer. nat. V. Kartsovnik: "Neue Erforschung der Deformation von Gummi. Experimentalanlage von M.Lipskiy".

Den Vortrag fand ein wissenschaftliches Seminare am 22.10.2015 statt.

Auf der Grundlage eines neuen Molekülmodells der Verformung von Elastomeren unter Berücksichtigung der Kräfte der Entropieelastizität [1] wurde eine Untersuchung des Kriechens und der Dauerfähigkeit von Silikongummi durchgeführt. Für Messungen des Kriechens und der Lebensdauer von Gummi wurde in der KIW-Gesellschaft e.V. ein Prüfstand für standardisierte Gummimuster hergestellt.

Unter den aktuellen wissenschaftlich-technischen Problemen, die sich im Focus unserer professionellen Tätigkeit und unseres Interesses befinden, ist ein hauptsächliches das Problem der Betriebssicherheit von Kernenergieanlagen.

Die Grundvoraussetzungen für den Erfolg unserer Ausarbeitungen zu diesem Thema bilden die praktischen Erfahrungen und die wissenschaftlichen Ergebnisse unseres Vorstandvorsitzenden Dr. Yuriy Tsoglin.

Fließkurven von Polymerschmelzen unterliegen bekanntlich nicht dem Newtonschen Fließgesetz. Sie besitzen eine Viskositätsanomalie, d.h. die Viskosität der Schmelze sinkt unter der Einwirkung von Scherspannung um das Vielfache mit der Zunahme der Geschwindigkeitsscherung.

Der Mechanismus der Viskositätsanomalie sowie die Theorie des Fließens von Polymerschmelzen haben bis jetzt keine eindeutige und überzeugende Erklärung gefunden.