Effect of stabilizer on the mechanical, morphological and thermal properties of compatibilized high density polyethylene/ethylene vinyl acetate copolymer/organoclay nanocomposites

In this work, the effects of a phosphate containing stabilizer on the mechanical, morphological and thermal properties of a compatibilized high density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blend containing an ammonium quaternary salts modified montmorillonite were studied from both statistical and experimental aspects. According to the results obtained from simultaneous implementation of analysis of variance (ANOVA) and mean effect assessment, the formulations designed based on the optimized coupling of stabilizer into organoclay/compatibilizer system exhibited the highest tensile properties among the prepared samples. From experimental point of view, the d-spacing measurements and microscopy observations through X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, revealed that the stabilizer not only favored the penetration of the polymeric chains between the silicate layers but also contributed to provide finer dispersion of the minor phase in the matrix. Thermal characterizations using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the stabilizer could play a role in prevention of the organic modifier of the nanoclay to undergo thermo-oxidative degradation by hindering the SN(2) nucleophilic substitution reactions between alkyl ammonium chains and oxygen molecules. This, we believe, is responsible for the properties enhancement, since the protective role of stabilizer might inhibit the formation of destructive degradation products which could collapse the organoclay tactoids and also deactivate the anhydride groups of the compatibilizer. (C) 2011 Elsevier Ltd. All rights reserved.