Thermal degradation kinetics of PP/OMMT nanocomposites with mPE and EVA

Abstract

The thermal properties and the kinetics of thermal degradation of nanocomposites of polypropylene (PP) and montmorillonite (OMMT) and an ethylene-co-vinyl acetate copolymer (EVA) as a minority phase, including a third elastomeric component represented by poly(ethylene-co-octene) (mPE) were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Two maleic anhydride modified PP (PP-g-AM), one of them commercial and the other one prepared in our laboratory, were used as compatibilizers. The expected nucleating effect of the organoclay in the nanocomposites and the increase on crystallization temperature was observed. The degradation kinetic parameters were obtained using the Coats e Redfern integral method to obtain the reaction order and the E2 function methodology to calculate the activation energy. The PP/OMMT nanocomposites with mPE or EVA exhibited higher degradation temperatures and activation energies than the neat PP and also a higher decomposition temperature than the PP nanocomposites without the elastomeric minority phase. The employment of the commercial compatibilizer generated more exfoliated structures on the ternary nanocomposites that contributed to a better thermal stability. The degradation mechanisms involve crosslinking, chain branching and chain scission reactions for the ternary PP/OMMT/mPE nanocomposites and an additional accelerated deacetylation process for the ternary PP/OMMT/EVA nanocomposites.