Paint/Polymer Interface Structure for ABS Injection Moldings

Abstract

Abstract Structure of paint/polymer interface was investigated for the injection molded and compression molded ABS specimens. For the interface of the injection molded specimen, a peculiar “zigzag” structure formation of several tens μm in size was observed. In contrast, the interface structure was not observed for the compression molded specimen and injection molded specimen annealed above the glass transition temperature (Tg). These facts indicate that the interface structure is related to the residual stress and molecular orientation at the surface of the injection molding specimen, because both surface structures would be removed by annealing at temperatures above Tg. The interface structure was strongly dependent on the curing agent concentration. The depth of the structure decreased with increasing curing agent concentration because of decreasing in curing time. At painting temperature between 70°C and 130°C, the depth and pitch were constant. However, below 60°C and above 140°C, the depth and pitch were changed. These results strongly suggest that the interface structure is attributable to relaxation of the surface residual stress and molecular orientation by paint soaking.