Colour changes in pigmented Nylon-6 systems containing copper iodide

The fading and colour changes in glass-filled polyamide formulations during ageing in water at 80 °C are reported. Formulations were stabilized with CuI and a UVA system and contained cobalt blue and phthalocyanine blue pigments. The results suggest that CuI causes an “aubergine” colour development in the absence of pigments whose origin is attributed to oxides and complexes of copper that are produced during thermal processing and degradation processes. Ageing in water causes dramatic fading along with a colour shift towards the green. This effect is attributed to leaching and/or hydrolysis of copper-containing species. It was found that an increase in CuI stabilizer produces an increased level of fading in un-pigmented samples. However, as the pigment loading is increased there is a concomitant reduction in the extent of fading and the extent of the green shift suggesting that pigments may mask ageing-induced colour changes in these systems. The susceptibility of phthalocyanine-pigmented polyamines to colour change is not adversely affected by CuI.