Effect of the substrate-binder interactions on the mechanical properties of compacts

The effect of the substrate-binder interfacial interaction in granules, made of PVP and glass ballotini as model substrates, on the mechanical properties of rectangular compacts consisting of these granules was investigated by use of the four-point beam bending technique. The mechanical properties of the prepared compacts were correlated with the physico-chemical characteristics--contact angle, surface tension and binder concentration--of the granulation liquid. The mechanical strength and Young's modulus of the specimens both reached a maximum value when the binder concentration in the granulation liquid was increased to 20% (w/v) for all granulation liquid volumes used. Above a 20% PVP concentration, the increasing granulation liquid contact angle hindered the binder spreading, creating weak regions in the compact and decreasing its mechanical strength.