Correlation of morphological, dynamic mechanical, and thermal properties in compatibilized polypropylene/ethylene-vinyl acetate copolymer/organoclay nanocomposites

Compatibilized and noncompatibilized nanocomposites based on polypropylene (PP)/ethylenevinyl acetate copolymer (EVA) blends, having 75/25 (wt %/wt %) PP/EVA ratio, with different contents of organoclay (OMMT) and maleated polypropylene as compatibilizer were made through a melt-mixing process with a twin-screw microcompounder, and their properties were investigated. X-ray analysis revealed mainly intercalated/partially exfoliated structures for the blend-based nanocomposites. Through a thermodynamic theoretical approach and transmission electron microscopy investigation, it was shown that the OMMT nanoparticles were mainly placed at the EVA phase of the nanocomposites. Also, scanning electron microscopy analysis showed that OMMT acted like a compatibilizer and reduced the average size of the EVA dispersed phase by preventing coalescence. Dynamic mechanical analysis revealed that the addition of OMMT in the presence of the compatibilizer increased both the storage modulus and damping factor of the corresponding blends. The critical interparticle distance of the EVA domains for achieving supertoughening behavior was obtained at about 100 nm. The addition of OMMT led to a significant improvement in the thermal stability of the blends, especially in the presence of the compatibilizer. A correlation between the morphological, dynamic mechanical, and thermal properties was established to determine the best performing composition, in which desirable damping and stiffness and good thermal stability could be achieved. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012