Effect of the structure of reactor poly(propylene-co-ethylene) blends on the diffusion coefficient and activation energy of a conventional antioxidant

The diffusion of a thermal stabilizer, i.e. IRganox 1010, has been studied in three different reactor poly(propylene-co-ethylene) blends namely HecoQ, ExpSS, and Super Soft. The diffusion experiments were carried out by using Roc's method based on a stack of several polymer films where each of them had 60-70 mum thickness. The concentration profile of the stabilizer in every film has been monitored by the absorbance at 282 nm of the recorded UV spectra. Under four experimental conditions the diffusion of Irganoz 1010 for all polymer materials can be correctly interpreted by using Fick's second law resolved under certain boundary conditions. Best-fitting the experimental data with the equation model also allows calculation of the diffusion coefficient D, for these polymer materials at 40, 70 and 80degreesC. By applying an Arrhenius-type equation to the calculated D coefficients, an estimation of activation energies of the diffusion process has been achieved An interpretation in terms of free volume theory has been applied to explain the observed variation of D which depends mostly on the amount of amorphous phase of the blends.