Atmospheric corrosion of Nylon 6,6 in Mauritius

Abstract

Plastics are being more and more commonly used for outdoor applications in Mauritius. In this context, the atmospheric corrosion degradation behaviour of nylon 6,6 was observed in the Mauritian atmosphere, having a corrosivity category of C3, according to ISO 9223. The crack width, depth and extent of the cracks formed on the surface were investigated using micrometry and image analysis. The changes in the chemical composition of the nylon 6,6 were investigated using the Fourier Transform Infrared spectroscopy technique. It was observed that the nylon 6,6 surface showed a progressive discolouration and a sudden increase in the size of the cracks after around 2 years of exposure. The degree of crack formation in terms of crack width, the depth of degradation and the microhardness of the surface were evaluated and all showed significant degradation only after about 2 years of exposure. Degradation has penetrated the test material within 750 µm from the surface in 4.5 years of exposure. Using the FTIR technique, evidence of chain scission occurring among the polymer chains was observed.

Keywords: nylon, atmospheric corrosion, weathering, cracks, FTIR.