2000 Volume 49 Issue 8 Pages 494-499
The corrosion behavior of polyamide plastics immersed in sulfuric acid solution was investigated. The degree of degradation was evaluated by the changes of weight, flexural strength, and molecular weight. The flexural strength rapidly decreased after the onset of immersion due to water absorption. A part of decreased flexural strength recovered by drying. Color changed layer was observed by using optical microscope, and the generation of crack was also observed in scanning electron microscopic photographs. The thickness of color changed layer agreed with that of crack depth. The average molecular weight of polyamide decreased by immersion in sulfuric acid solution. It was recognized by X-ray microanalyzer that sulfuric acid molecules penetrated into the inside of the color changed layer. Thus, color changed layer was formed by the extreme decrease of molecular weight, and color unchanged layer was also degraded by the penetration of sulfuric acid.
