Diffusion coefficient and activation energy of Irganox 1010 in poly(propylene-co-ethylene) copolymers

The diffusion of a thermal stabiliser, Irganox 1010, has been studied both in a commercially available polypropylene homopolymer (HomoQ) and in a poly(propylene-co-ethylene) copolymer (RacoS). The diffusion experiments were carried out by using the Roe method formed by a stack of several polymer films having 60-70 mum as thickness under nitrogen atmosphere. The concentration profile of stabiliser in every film has been monitored by the absorbance at 282 nm in UV spectra recorded for every film forming the stack assembly. Under our experimental conditions, the diffusion of Irganox 1010 in each film. stack for both polymer materials can be correctly interpreted by using the Fick's second law. The best fit of the experimental data with this equation allows calculation of the diffusion coefficients D, for these polymer materials at 40, 70 and 80 degreesC. By applying an Arrhenius equation to the calculated D coefficients, an estimation of activation energies of the diffusion process has been also achieved. (C) 2001 Elsevier Science Ltd. All rights reserved.