Identifying the Influence of the Polymer Matrix Type on the Structure Formation of Microcomposites When They Are Filled with Copper Particles

Studies were carried out to establish the mechanisms of structure formation during crystallization of polymer composites based on polyethylene, polypropylene or polycarbonate filled with copper microparticles. The researches were executed using a technique, the first stage of which consisted in the experimental determination of crystallization exotherms of composites, and the second – in the theoretical analysis based on the obtained exotherms of the structure formation characteristics. A complex of studies on determination of crystallization exotherms for investigated microcomposites was carried out. The regularities of the cooling rate influence of composites, the method of their production and the mass fraction of filler on the temperature level of the beginning and ending of crystallization, the maximum value of the reduced heat flux, etc. were established. It is shown that for the applied methods of obtaining composites the increase of their cooling rate causes the decrease of the indicated temperatures and heat flux. It is established that the value of the mass fraction of the filler has a less significant effect on the characteristics of the crystallization process.The regularities of structure formation of polymer composites at the initial stage of crystallization with the involvement of data on crystallization exotherms and nucleation equations are investigated. The presence of planar and three-dimensional mechanisms of structure formation at this stage has been established. It is shown that the ratio of these mechanisms is influenced by the type of polymer matrix and the method of obtaining composites.For the second stage of crystallization, which occurs in the entire volume of the composite, the results of experiments on crystallization exotherms were analyzed on the basis of the Kolmogorov-Avrami equation. It is shown that the structure formation of polyethylene-based composites occurs by the three-dimensional mechanism, and on the basis of polypropylene and polycarbonate – by the mechanism of the stressed matri

Establishment of Regularities of Influence on the Specific Heat Capacity and Thermal Diffusivity of Polymer Nanocomposites of A Complex of Defining Parameters

This paper reports a series of experimental studies to establish regularities of the integrated effect exerted on the specific heat capacity of polymer nanocomposites by such factors as the temperature regime of their production, the value of the mass fraction of the filler, and the temperature of the composite material. The studies were conducted for nanocomposites based on polypropylene filled with carbon nanotubes. When obtaining composites, the method of mixing the components in the melt of the polymer was used. During the studies, the temperature of nanocomposites varied from 295 to 455 K, the mass fraction of the filler ‒ from 0.3 to 10 %. The basic parameter of the technological mode for obtaining composite materials, the value of overheating the polymer melt relative to its melting point, varied in the range of 10...75 K. It is shown that the temperature dependence of the specific heat capacity of the considered composites is sensitive to changes in the overheating of the polymer melt only in the region maximum values of the specific heat capacity. Concentration dependences of the specific heat capacity of the considered nanocomposites at different values of their temperature and the level of overheating of the polymer melt have been built. The studies have been carried out to identify the effects of the influence of the above parameters on the coefficient of thermal diffusivity of nanocomposites. It has been established, in particular, that an increase in the level of overheating the polymer could lead to a very significant increase in the coefficient of thermal diffusivity, which is all the more significant the higher the proportion of filler and the lower the temperature of the composite material. It is shown that the level of overheating the polymer melt relative to its melting point is a parameter that can be used as the basis for the creation of polymer composite materials with specified thermophysical properties