Studies of solid—solid interactions: I. Comparison of tensile strength theory with experiment using a model powder

Abstract A powder containing spherical submicron polystyrene particles with well-characterized surface chemistry has been prepared. The powder was obtained by freeze drying a polystyrene latex prepared by surfactant-free aqueous emulsion polymerization. Both the latex and the powder were characterized by various techniques. The polystyrene particles, by virtue of monodispersity and well-characterized surface chemistry, are proposed to be a model powder. Two different particle surface chemistries were tested, a sulfate-rich and a carboxyl-rich surface. The tensile strength of compacts was measured at relative humidities of 0%, 45% and 60%. The experimental tensile strengths were compared with those predicted by the recent theory proposed by Parfitt and Hartley. A large discrepancy was found between experiment and theory. Humidity was found to have an effect on the tensile strength but it was not large enough to account for the discrepancy.