Rheological Behavior Features of Feedstocks with a Two-Component Wax–Polyolefin Binder Compared to Analogs Based on Polyoxymethylene

Abstract

Despite the large number of studies devoted to different compositions of polymer binders for PIM technology, the actual task is still a comparative analysis of the properties of different types of binders to determine their advantages and disadvantages and optimize the compositions used. In this regard, this study aims at the identification and comparative analysis of the rheological properties of the most demanded feedstocks with binders based on polyoxymethylene and a wax–polyolefin mixture under the condition of using identical steel powder filler. The rate of change in the volume fraction of the liquid phase of the binder in the compared feedstocks with temperature change was determined by the calculation–experimental method. As shown, the temperature dependence of the viscosity of feedstocks with a binder based on a polymer blend depends on factors with variable power, i.e., the viscosity change with temperature occurs by different mechanisms with their relaxation spectra. Thus, the principle of temperature–time superposition for feedstocks with multicomponent binders is not applicable, and the study of the viscosity of such materials should involve a wide range of shear rates and temperatures using experimental methods. Capillary rheometry was used to measure the flow curves of feedstocks based on polyoxymethylene and wax–polyolefin binders. The analysis of flow curves of feedstocks showed that feedstocks with a binder of solution–thermal type of debinding have significantly lower viscosity, which is an advantage for molding thin-walled products. However, their difference of 1.5 times sensitivity to the shear rate gradient leads to their lower resistance to “jets” and liquation of components because of shear rate gradients when molding products with elements of different cross-sectional areas.