Synergy of low-and high-density polyethylene in a binder system for powder injection molding of SiC ceramics

Abstract

Powder injection molding enables the complex shape molding of SiC. The strength of a green body is one of the most important properties in injection molding. Due to the long heating time, the thermal debinding of the wax-based binder in powder injection molding is usually a very energy-consuming process. In this study, the synergy of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) in a wax-based binder was designed for SiC ceramics prepared by powder injection molding. The microstructure, mechanical properties and rheological properties of the sample were studied. The results demonstrated that the best ratio of adding LDPE to the binder was 6 wt%. A combination of LDPE and HDPE reduced the sensitivity coefficient and viscosity of the feedstock, which improved the uniformity of the green body. When 6 wt% LDPE was added to the binder, the tensile properties, impact properties and bending properties of the green body increased by 22%, 19% and 25%, respectively. The heating time of the thermal debinding was shortened by 40%, which greatly reduced the energy consumption. Based on the properties of LDPE, the theoretical model of thermal debinding analysis was performed. The short and branched chain of LDPE refines the microstructure of HDPE and provides more exhaust channels for thermal debinding. The compound binder in this work may also be used in the injection molding of other materials.