Abstract
A thiirane bifunctional monomer, 3, 4-epithiobutyl 2, 2-bis (methacryloyloxymethyl) propionate (EP2BMA), was employed as an adhesive bonding promoter for precious metals. Two surface-treatment agents for precious metals were prepared by dissolving EP2BMA in ethanol. Gold alloy, gold-silver-palladium alloy and silver alloy were used as an adherend. Mirror-finished alloy surfaces treated with the agents were allowed to stand for one day and then washed to remove excessive monomer when the thiirane concentration was high (1 mol %). Two alloy specimens were butt-jointed with MMA-PMMA resin and tensile bond strengths were measured after 2,000 thermal cyclings, followed by observation of the fractured surfaces after tensile test. The surface treatment with EP2BMA significantly improved bond strengths. The effect of EP2BMA was comparable to that of 9, 10-epithiodecyl methacrylate (EP8MA) when TBBO was employed as an initiator, while the bond strength to silver alloy treated with EP2BMA was considerably lower than that with EP8MA in the case of BPO-amine initiator.
