Studies on Effects of Etching Reagents on Plastic Surfaces

This paper reports the research on etching mechanism for plating of ABS resin. After etching with sulfuric-chromic acid solution, the resin was examined by infrared spectroscopy, adsorption of dyes, weight loss, surface roughness, etc. A linear relationship was observed between the immersion time in the solution at 60°C and the amount of adsorption or other factor (such as weight loss or surface roughness) in the normal etching reagent (for example, saturated chromic acid containing 60% sulfuric acid). The results showed that polybutadiene particles only were preferentially oxidized and dissolved into the etching reagent. A further relation was examined between the immersion time and adhesion of plating on the resin. The adhesive strength was rapidly increased during the first several minutes and attained to a peak after 5-20 minutes, when the peeling strength obtained was 11kg/in. After etching with a solution of sulfuric-chromic acid (both acids were in higher concentrations), a layer insoluble in methyl ethyl ketone (MEK) was formed on the resin surface, which was examined by differential scanning calorimetry and elementary analysis. The effect of the solution was so remarkable that the resin remained in network structure insoluble in MEK, which seemed to be degraded. It was further found by the results of weight loss, surface roughness, etc. that AS resin matrix as well as polybutadience was attacked and dissolved into the solution. It was also shown that the immersion time in the solution had powerful effects on the adhesive strength and the resin etched for a long time had very little adhesive strength.