Physico-mechanical and thermophysical properties of composites based on secondary polypropylene modified with ultra-high molecular weight polyethylene

The relevance of the problem under study is due to the development of a method for the rational use of polypropylene-based polymer waste (PP) by creating polymer composites in a mixture with ultra-high molecular weight polyethylene (UHMWPE). The article is aimed at studying the physico-mechanical and thermophysical characteristics of polymer composites based on PP and UHMWPE. The leading research methods for this problem are the study of the strength characteristics of polymer composites at break and bending, thermogravimetric analysis and differential scanning calorimetry. It is shown that the maximum torque in the mixing chamber during polymer melting does not additively change depending on the composition of the mixture. The increase in maximum torque more than 2 times occurs when filling the secondary polypropylene 5 % of the mass. UHMWPE and only 25 – 35 % decreases when filling UHMWPE with polypropylene in an amount of 10 – 50 % of the mass. Filling of secondary UHMWPE polypropylene up to 3 % of the mass slightly strengthens the composition, and also increases its modulus of elasticity at break and bending. UHMWPE allows increasing the thermal stability of secondary polypropylene by increasing the decomposition onset temperature by 12°C, the mass of the residue upon heating to 400°C, and peak displacements corresponding to the maximum decomposition rate of the main substance in the high temperature region. Two endothermic peaks corresponding to the melting temperature of the starting polymers are observed in the DSC thermogram in the heating mode; the melting temperature of polypropylene in the composite is 3.1– 4.8°C lower than that of an individual polymer. The crystallization of PP and UHMWPE in the mixture proceeds in the same temperature range and is characterized by the presence of one exothermic maximum on the DSC curve, which is shifted to the temperature region corresponding to the crystallization temperature of an individual UHMWPE.