Abstract
Isothermal microcalorimetry (MC) was used to study the oxidation stability of isotactic polypropylene (PP) including different concentrations of stabilizer in the temperature range of 110C–130C. A microcalorimeter provides in this context a fast method for the investigation of oxidation and thermal stability at various conditions opposite to more classical time- and
labor-consuming methods. The measurements were performed in both wet and dry environments in sealed stainless steel vials for new and preaged materials. The preaged materials were aged in advance at 110◦C and 100% relative humidity to observe the effect of the ageing for the MC measurements. Different material sizes (ground, unground) were also investigated. The results from the MC measurements on preaged material show that stabilized PP produce less heat flow than unstabilized PP in dry atmosphere, and no
significant difference between the various levels of stabilized materials are observed as long as the stabilizer is present. This indicates that when stabilizer is present above a certain but so far unknown concentration (50–100 ppm), the oxidation and the following heat flow of the material becomes much weaker compared with the unstabilized materials. Comparison between wet and dry calorimeter
measurements in air indicates that the autoxidation of the unstabilized material is more powerful in a wet atmosphere. No significant differences are observed for the stabilized materials. In the material particle size investigation, the heat flow and total energy output seem to be higher for the ground unstabilized materials; no difference is observed for the stabilized material. Copyright 2014 Wiley Periodicals,
labor-consuming methods. The measurements were performed in both wet and dry environments in sealed stainless steel vials for new and preaged materials. The preaged materials were aged in advance at 110◦C and 100% relative humidity to observe the effect of the ageing for the MC measurements. Different material sizes (ground, unground) were also investigated. The results from the MC measurements on preaged material show that stabilized PP produce less heat flow than unstabilized PP in dry atmosphere, and no
significant difference between the various levels of stabilized materials are observed as long as the stabilizer is present. This indicates that when stabilizer is present above a certain but so far unknown concentration (50–100 ppm), the oxidation and the following heat flow of the material becomes much weaker compared with the unstabilized materials. Comparison between wet and dry calorimeter
measurements in air indicates that the autoxidation of the unstabilized material is more powerful in a wet atmosphere. No significant differences are observed for the stabilized materials. In the material particle size investigation, the heat flow and total energy output seem to be higher for the ground unstabilized materials; no difference is observed for the stabilized material. Copyright 2014 Wiley Periodicals,