Thermo-oxidative stability of polyamide 6 films III. Isothermal microcalorimetry

Isothermal microcalorimetry (MC) was used to study the thermo-oxidative sta bility of polyamide 6 film in the temperature range of 100-130 degrees C. T he heatflow was found to vary for ageing times beyond the embrittlement of the film samples. The heatflow curve was characterised by an initial peak a nd a sigmoidal increase through a maximum. Polyamide 6 stabilised with the phenolic antioxidant Irganox 1098 shows a similar heatflow time curve altho ugh shifted towards lower heatflow levels and longer times. A maximum in th e heatflow curve was found to correspond to an accumulated heat energy in t he range of 15-20 J g(-1), whereas a drop in strain at break occurred in th e range of 45-55 J g(-1). Microcalorimetry was compared to oxygen uptake an d chemiluminescence measurements. All of these techniques respond to oxidat ion but exhibit distinctly different rate time curves. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.