Chemistry of removal of ethylene vinyl acetate binders

Abstract

The research presented herein has focused on debinding of an ethylene copolymer from a SiC based moulded ceramic green body within an inert atmosphere. Upon heating, the pure polymer undergoes a two-stage thermal degradation process. In the first stage, acetic acid is the only degradation product formed. The effect of the introduction of high surface area powder on the chemistry and kinetics of this first stage reaction was examined. The effluents were captured and analysed in a gas chromatograph/mass spectrometer. The product of the reaction was not altered by introduction of the ceramic powder. However, the kinetics of the reaction were altered. The kinetics of the reaction were determined with the use of thermogravi metric analysis (TGA). The mechanism of mass transport during binder removal was determined by monitoring dimensional changes during binder removal. It was found that one unit volume of shrinkage corresponded with one unit volume of binder removed, indicating that no porosity developed. The escaping acetic acid effluents must diffuse through the liquid polymer filled pores to escape. Bloating was observed in certain conditions and was attributed to the concentration of acetic acid exceeding a critical value, resulting in bubbling.