Study of thermal degradation mechanism of binders for ceramic injection molding by TGA-FTIR

Abstract

Thermal debinding is the most widely employed method in ceramic injection molding. The gas evolution of binders and their mixture during degradation has been studied by TGA-FTIR. The results show that the thermal degradation of typical binders like ethylene vinyl acetate copolymer(EVA), polystyrene(PS), paraffin wax(PW) and stearic acid(SA) involves three main events of degradation: the first corresponds to the degradation of macromolecule binders into smaller molecules or carbon oxides; the second corresponds to the degradation of small molecular into carbon oxides; and the third corresponds to the oxidation of carbon residues to carbon oxides. The degradation of acrylic resin (AR) involves only one main event of degradation and it corresponds to the degradation of AR into acrylic ester small molecule. Mixture's 3D diagram verified that degradation products of binders are not changed with the mixing of binders. The TGA(DSC) curves of mixture suggest that the mixing of binders decreases the initial degradation temperature of some low molecular weight binders. But it also increases the degradation temperature of some polymer binders. The TGA(DTG) curves of feedstocks reveals that ceramic powders increase the temperature at the beginning of degradation due to a physical or chemical adsorption of ceramic powders on binders.