The rheology of dense colloidal pastes used in 3D-printing

The rheology of dense, aqueous pastes of soda-lime glass frit and a polysaccharide binder, designed for use in a recently developed glass 3D-printing process, is reported. Pastes containing either xanthan gum or 2-hydroxyethyl cellulose binder and glass frit with average particle sizes of either 38-63 μm or 150-250 μm were investigated using a controlled stress rheometer over an applied stress range of (10.66-942.2 Pa). The pastes exhibited yield behaviour followed by shear-thinning as the applied stress was increased, in a similar manner to highly concentrated polysaccharide solutions. The yield stress was found to be reduced for pastes containing xanthan gum binder and larger glass particles. The physical properties (Young's modulus, opacity and density) of glass produced by kiln-firing pastes used for glass 3Dprinting are also reported. Paste composition was varied to investigate the effect of micro scale changes on the macro scale glass properties. The average glass particle diameter in the frit was varied in the range 38-250 μm and glass produced from 'pastes' containing frit-only, frit with binder and frit with binder and water were compared.