2013 Volume 49 Issue 7 Pages 244-248
In UV-curing adhesives, sufficient adhesive strength with relatively high elastic modulus at roomtemperature and high Tg cannot be obtained by the stress concentration at the interface between the adhesive and adherend. To verify the effect of surface morphology on adhesive strength, flat and sawtooth surface structures were studied. Changing surface morphology from flat to sawtooth structures,fracture mode was found to be changed from interfacial failure to the mixed mode with cohesive failure and the initial adhesive strength could be grea tly improved. On the otherhand, under 60℃ 90%RH storage, it was found that the sawtooth structure shows the fracture mode transition to the interfacial fracture only over storage time and dhesive strength is reduced with the accelerated rate of deterioration. The cause of this reduction in adhesive reliability is considered as follows. The adhesive absorbs moisture first to swell. Then, the total swelling force affects the local peeling on the highest surface points of sawtooth surface structure. For high reliability, it is important to further improve the stress tolerance and the reduction of the swelling rate by lowering the moisture absorption of the adhesive.
