Influence of Mixing and Standing Times on the Rheological Properties and Performance of Coatings for Lost Foam Shell Casting

Abstract

This study investigates the rheological properties and performance of coatings used in lost foam shell casting, focusing on the influence of mixing and standing times. The experimental procedure involved systematically preparing coatings by varying the mixing times (10, 20, 30, 40, 50, and 60 min) to assess the dispersion of particles and the subsequent standing times (1, 7, 11, 24, 40, and 48 h) to evaluate the stability of the mixture. A rotational viscometer was utilized to measure the viscosity and shear stress of the coatings under different conditions. The results indicate a significant decrease in viscosity with increasing mixing time, stabilizing after 50 min due to the uniform dispersion of solid particles and shear-thinning behavior. Conversely, the viscosity initially increases with prolonged standing time as the binder’s molecular chains reform, reaching a peak before gradually decreasing. The optimal performance of the coatings, characterized by stable viscosity and consistent rheological properties, was achieved with a mixing time of at least 50 min and a standing time not exceeding 40 h. These findings provide critical insights into optimizing the preparation and application processes of coatings, ensuring enhanced efficiency and quality in lost foam shell casting.