Heat physical properties of polymer composites based on polychlortrifluoroethylene filled with thermally expanded graphite
Authors: Sichkar T.G. , Rokytskyi M.O. , Yanchevsky L.K. , Rokytska G.V. , Ursul K.V. , Shut M.I. 
Published: January 2023

Based on research and comparative analysis of heat physical (specific heat capacity cp, thermal coefficient of linear expansion a) properties of systems polychlorotrifluoroethylene (PCTFE) - nanodispersed thermally expanded graphite (TEG) and PCTFE - nanomodified silicon dioxide (SiO2) TEG (30% SiO2 for 70% TEG) the influence of the structural-morphological state of the components and their concentration, the level of interfacial interaction on the physical properties of nanocomposites has been studied.
It is established that the double effect of the modified nanofiller on the crystalline component of the matrix structure is that a more developed crystal structure is formed in the polymer-modified nanofiller interaction zones and, conversely, some amorphization in the peripheral zones. At the same time, increasing the concentration of the modified nanofiller leads to competition from the growth of neighboring crystallites and the ability to fix macromolecules “from both ends” on the particles of the modified nanofiller. Whereas in the case of unmodified dispersed TEG the existence of such competing factors led to their mutual compensation and, as a consequence, stabilization of reflex temperatures after reaching the percolation threshold and exceeding the percolation threshold, in the case of modified nanofiller when polymer-filler interactions percolation of the second factor predominates, which leads to a decrease in the temperatures of the corresponding reflexes almost to their values, which correspond to a pure matrix.
The work found that depending on the nanofiller concentration, the structure of the matrix and the system as a whole shows a transformation in the size of the inhomogeneity and change in the size of the inhomogeneity of the system structure is associated with the transition from inhomogeneity as the size of crystallites, the growth of which is activated by nanofiller at low concentrations, through the percolation threshold, to inhomogeneities associated with coagulation of nanoparticles at concentrations exceeding the percolation threshold. Thus the case of nanofillers, it is not advisable to use concentrations that significantly exceed the percolation threshold, as this leads to coagulation of the filler particles and the corresponding loosening of the matrix.
It is also shown that modification of the nanofiller (TRG/30%SiO2) increases intermolecular interaction in the filler-matrix system. Depending on the concentration of the filler, the structure of the matrix and the system as a whole demonstrates dynamic transformations in the size of the heterogeneity of the structure. Also, research results show that modified nanofiller is more active against the polymer matrix than unmodified, which is a consequence of the fact of the double action of the modified nanofiller on the matrix structure is manifested, which consists in the formation of a strong crystalline structure in the zones of influence of the nanofiller and amorphization of the matrix in the peripheral zones