The Effect of Water on Matrix/Filler Adhesion in a Polyurethane Elastomer

The static “moduli”, failure stresses and dynamic moduli of both filled and unfilled polyurethanes were measured over a range of equilibrium water contents and these results are compared with those obtained from dry controls. Where barium sulphate was employed as the major filler component, it is shown that the presence of as little as ～0.7% water results in a profound degradation of mechanical properties with the loss of most of the contribution attributable to the presence of fillers as a result of hydrolytic disruption of filler/matrix adhesion. A quantitative relationship between water content and mechanical properties is established and the mechanics of the water/polymer/filler interaction are considered. Less dramatic effects were observed when barium sulphate was replaced by iron oxide and these were apparently further reduced by the use of a silane coupling agent.