Water-Assisted Production of Polypropylene/Boehmite Composites

Abstract

In this study polypropylene (PP) matrix-based boehmite alumina (BA) reinforced composites were prepared batchwise in an internal mixer. BA particles up to 10 wt.% were incorporated by 1. traditional melt mixing and 2. in a novel, Water-Assisted (WA) way, called fast evaporation mixing, during which BA was dispersed in PP with the use of an aqueous carrier medium. The WA way with pure water as medium proved to be ineffective because of the presence of the Leidenfrost effect. Therefore, an additional agent, carboxymethyl cellulose (CMC) was used to increase the boiling temperature of the water. Mechanical, morphological and thermal properties of the composites were determined. Scanning electron microscopy images revealed a partially dispersed structure of BA within the PP matrix in all cases, where aggregates and dispersed particles were identified as well. The size of the agglomerates observed was the smallest when BA was incorporated by being dispersed in water/CMC firstly. The mechanical tests results indicated that the reinforcing effect of BA was also most prominent in this case. However, CMC had an opposite effect on PP, than BA thus reducing the overall enhancement in mechanical properties. Differential scanning calorimetry showed an increase in the crystallinity ratio of PP with increasing BA content, which indicates a nucleating effect of BA.