WATER RESISTANCE OF RESIN-BONDED JOINTS WITH TIME-RELATED TO ALLOY SURFACE-TREATMENT

Objectives: This paper attempts to study the resistance of resin-bonde d metallic joints to damage in water with time. Methods: Unlike the sh ear or tensile test, a cleavage test (Double Cantilever Beam test) all ows us to follow the crack propagation in water, according to the frac ture mechanics concept. Moreover, it is possible to follow the kinetic degradation of the metal/resin interface because this test is not tot ally destructive to the assembly. We have worked on 18 batches accordi ng to the nature of the alloys (Pd, Pd-Ag, Au, Co-Cr and Ni-Cr) and th e surface treatment (sandblasting, Silicoater MD, Rocatec, V-Primer). The crack length was measured over a period of 20 days. The results ar e expressed in terms of adherence energy. Results: The adherence energ y dramatically decreased with time in water. The slope of the regressi on straight line appears to be a good criterion for evaluating the dur ability of the alloy/adhesive interface. We have demonstrated the impo rtance of silica coating and, especially, the effectiveness of the Roc atec system upon the degree of hydrolytic degradation, and have shown how the development of cracks depends upon surface treatment. (C) 1998 Elsevier Science Ltd. All rights reserved.