Thermophysical properties of polymer composites based on secondary polypropylene filled with chalk

Abstract

One of the most common ways to create polymer composites based on polypropylene is to fill it with chalk, which allows you to improve the appearance of the resulting plastic products and their performance properties. The thermoplasticity of the resulting polymer composites determines the possibility of involving retired polymer materials in re-processing, which requires the study of the laws of the influence of heating on the thermophysical properties of the polymer phase. In this paper, we study the regularities of changes in the thermophysical parameters of polymer composites based on secondary polypropylene in the process of filling it with a chalk additive. It is shown that processing of primary polypropylene by injection molding leads to a decrease in the thermal stability of the resulting secondary polymer material without changing the melting and crystallization temperatures of the polymer phase, but is accompanied by a decrease in the melting enthalpy (by 9 – 11 %) and the degree of crystallinity of the polymer (by 5.6 – 6.5 %). Filling secondary polypropylene with chalk further reduces the temperature of the beginning of decomposition of the composite, while the temperature corresponding to the maximum rate of thermal-oxidative destruction is shifted by 18 – 25 °С to the lower temperature region. The introduction of a 2 mass.p. chalk additive into polypropylene reduces the melting point by 3.6 °С and increases the crystallization temperature of the polymer phase by 1.3 °С. Filling of secondary polypropylene with a chalk additive in the amount of 5 – 10 mass.p. reduces the degree of crystallinity of the polymer, which can lead to changes in the physical and mechanical properties of plastic products.