THE EFFECT OF DISPERSION TIME ON THE STRUCTURE AND THERMOPHYSICAL PROPERTIES OF SYSTEMS BASED ON POLYETHYLENE GLYCOL AND MONTMORILLONITE

Abstract

In this work, the effect of ultrasonic dispersion time on the structural and thermophysical properties of nanocomposites was studied. Model systems were made based on polyethylene glycol and montmorillonite. All samples had the same composition and filler content (5% by weight), the ultrasonic treatment time was from 5 to 12 minutes. The methods of wide-angle X-ray scattering and differential scanning calorimetry were used to establish the dependence of the properties of the systems on the dispersion time. Data analysis of the obtained results showed that the variation of ultrasonic dispersion time significantly affects the properties of polymer nanocomposites. As the mixing time increases, the interplanar distance of montmorillonite increases, which indicates an increase in the degree of intercalation of the polymer matrix. At the same time, the crystallinity of the nanocomposite decreases, which corresponds to the increase in the area of the polymer/filler boundary layer. The melting temperature of the nanocomposite increases with increasing dispersion time. This trend is a consequence of the complication of the thermal movement of polymer molecules due to the presence of a developed surface of the filler. It is shown that with an increase in the sonication time, the part of the immobilized amorphous fraction of the polymer increases. This is explained by the fact that the polymer intercalated in the interlayer space of montmorillonite loses its ability to cooperative movement, that is, to glass transition. It was established that the maximum improvement of system properties is observed at a dispersion time of 10 min. In this state, the montmorillonite particles are most stratified, which leads to the maximum increase in the area of the boundary layer. During further mixing, processes of aggregation of montmorillonite particles and destruction of polymer molecules occur, which leads to the loss of the desired properties of the nanocomposite. Finding the optimal mixing time of a polymer nanocomposite makes it possible to obtain the desired properties of systems with a defined composition.