Mechanical and Thermal Degradation Properties of Isotactic Polypropylene Composites with Cloisite15A and Cloisite20A

Abstract

In this work, the influence of maleic anhydride grafted polypropylene (PP-g-MA) content on thermal and mechanical properties of polypropylene (PP) composites with two types of clays, differing modifier density in the interlayer space, Cloisite15A and Cloisite20A, was studied. PP/clay composites were melt blended in presence of different content of PP-g-MA from 3, 6, 9, and 12 wt.%. It was found that Cloisite15A with a high density of the modifier promotes the formation of intercalated structures, while Cloisite20A with a low density of the modifier, predominantly exfoliated nanocomposites are formed. In the first case, the structure tends to become intercalated whilst composites with Cloisite20A favor the formation of predominantly exfoliated structures. The formation of the nanocomposite is accompanied by a significant increase in thermal stability (50 % weight loss is observed at temperatures of 360 °C and 430 °C for polypropylene and nanocomposites based on it, respectively). An analysis of the mechanical properties of nanocomposites generally indicates an increase in the elastic modulus by 15–20 %, and this effect is more pronounced for exfoliated structures, the yield strength practically does not change and the elongation at break decreases noticeably.