Phenomenological Kinetic Equation of Conversion of a Binder of Composite Materials Based on Isothermal Experimental Data

Abstract

In the problems of technological mechanics, such as manufacturing of composite structures, packaging and deployment of space-grade prepreg products, etc., there is a need to calculate the current mechanical properties of a composite material with an incompletely cured binder. Such properties are determined, first of all, by the state of the binder, which is described by the kinetic equation of conversion. The parameters of the kinetic equation depend on many factors: temperature, diffusion, the presence of a catalytic system, modifiers, reagents, the formation of by-products of kinetic reactions, evaporation of reagents, the effect of radiation on the reaction, etc. Reliable consideration of the influence of each factor in the kinetic equation turns out to be practically impossible. Therefore, most researchers use the phenomenological conversion equation based on experimental data, since these data reflect all the features of the kinetic process. The paper considers the first-order conversion equation, which takes into account autoacceleration and autodeceleration. The equation parameters are determined from isothermal experimental data using the following technique. The equation for the conversion rate is integrated, and the integral is used to construct a system of equations containing experimental data and the sought approximation parameters, which are determined by standard mathematical methods. The dependence of the kinetic equation parameters on temperature is also constructed by approximation. Examples of constructing conversion equations for a two-component model composite and the Barnes multicomponent industrial mixture are given. It is shown that the parameters of the kinetic equation in both cases significantly depend on temperature. Examples of using the obtained kinetic equation to calculate the degree of curing of samples under a given temperature loading are given.