Influence of mineral filler on the thermal conductivity of polymer composites

Abstract

The study focuses on the development of polymer composites based on the Latex 2012 aqueous dispersion with mineral fillers of volcanic (andesite) and technogenic (fly ash from Burshtyn TPP and Kurakhove TPP) origin, aimed at achieving optimal thermal insulation properties. The main problem addressed was determining the influence of the type, concentration, and combination of fillers on the thermal conductivity of composites. High thermal conductivity of polymeric materials significantly limits their application in thermal insulation systems, making it crucial to investigate the mechanisms of interfacial interactions between fillers and the matrix for creating effective compositions.

The sizes of filler crystallites were determined using the Scherrer method: for andesite – 110 nm, fly ash B – 100.4 nm, and fly ash K – 113 nm. These data indicate the fillers' ability to affect phonon scattering in the material, reducing overall thermal conductivity. The thermal conductivity of the fillers is as follows: fly ash B – 0.2072 W/m·K, fly ash K – 0.2241 W/m·K, and andesite – 0.2118 W/m·K. Fly ash B demonstrated the best results due to its low thermal conductivity and high surface energy, which contributes to better interaction with the polymer matrix.

An analysis of the dependence of composite thermal conductivity on temperature and filler concentration showed that increasing filler concentration increases thermal conductivity due to the formation of thermal bridges between particles. However, combining different fillers in optimal proportions can mitigate this effect. Based on the Nielsen model, the composite compositions were optimized to achieve minimum thermal conductivity. The best results were obtained for a binary filler system of fly ash B and andesite in a 53:35 mass ratio, providing the lowest effective thermal conductivity of the composite – 0.173 W/m·K. Other successful combinations include fly ash B with fly ash K (60:40 wt. %) and andesite with fly ash K (45:55 wt. %), which also demonstrate significant improvements in thermal insulation properties.

The proposed compositions can be applied in the field of energy-efficient construction, thermal regulation systems, thermal insulation materials for industrial equipment, and other areas requiring low thermal conductivity. The research results are also valuable for developing materials that operate under significant temperature variations (from –125 °C to +100 °C), providing stable thermal insulation properties.