Influence of structure-forming agent on rheological properties of polymer mixture based on low and high density polyethylene

Abstract

The paper considers the effect of a structure-forming agent (titanium dioxide) on the rheological characteristics of a polymer mixture based on low and high density polyethylene, taken in a 50/50 ratio. The titanium dioxide concentration was 1 wt%. The rheological behavior of melts of polymer composites was studied using a CEAST MF50 capillary rheometer (Instron, Italy) at temperatures of 190, 210, 230, 250 °С and loads of 3.8, 5.0, 10.0, 12.5, and 21.6 kg. The effect of temperature and shear stress on the regularity of changes in effective viscosity and shear rate has been established. According to the Arrhenius – Frenkel – Eyring model, the activation energy of the viscous flow of composites is determined. The “apparent” activation energy of the viscous flow varies within 16.04–33.10 kJ/mol for the initial polyethylene mixture and in the range of 6.96–33.10 kJ/mol for composites modified with a structurant based on a mixture of low and high density polyethylene. A universal temperature-invariant characteristic of the viscosity properties of polymeric materials has been constructed, which makes it possible, by extrapolating this dependence to the region of high shear rates, to predict the technological mode of their processing by injection molding and extrusion.