Creation of low-thermal-conductivity polymer nanocomposites for internal gas vents of boiler chimneys

Abstract

Methods and results of experimental studies of thermophysical, structural and mechanical properties of low-heat-conducting polymer nanocomposites, oriented to use for gas ducts and chimneys of boiler installations, as well as various other gas and water communications are presented. In this work, on the basis of the performed set of methodological studies regarding the analysis of the legitimacy of using different models of heat conductivity for predicting the heat-conducting properties of these composites, the possibility of using for this prediction a number of models of the theory of the effective medium and the theory of percolation is considered. The analysis of thermophysical properties, structural characteristics and Young's modulus of low-heat-conductivity polymer nanocomposites based on polyethylene and polypropylene is carried out. Using these nanocomposites as an example, the achievement of a significant increase in their Young's modulus in comparison with unfilled polymers with a relatively small increase in heat conductivity is demonstrated. To obtain nanocomposites, we used a method based on mixing the components in a polymer melt using an extruder and then shaping the composite into the required shape by hot pressing. The method of differential scanning calorimetry was used to determine Young's modulus. On the basis of the studies carried out, the possibility of obtaining low-heat-conducting polymer nanocomposites with improved mechanical characteristics has been shown. In particular, it was shown that for nanocomposites based on polyethylene or polypropylene filled with CNTs (carbon nanotubes) or nanodispersed aerosil particles, with a mass fraction of the latter up to 2%, the following takes place a relatively insignificant increase in heat conductivity coefficients and a significant increase in the modulus of elasticity in tension. The research data also made it possible to obtain for the developed nanocomposites the temperature dependences of their specific mass heat capacity and, on this basis, to analyze the regularities of changes in the structural characteristics of these materials.