Effect of multistage sonication on dispersive mixing of polymer nanocomposites characterized via shear-induced crystallization behavior

While nanoparticle dispersion is necessary to achieve optimal properties, it has long been recognized as a major technological hurdle for polymer nanocomposites. Here, a systematic study incorporated carbon nanotubes (CNTs) in polycaprolactone (PCL) using a multi-stage sonication process, with Stage 1 sonication of CNT/solvent followed by Stage 2 sonication of the preprocessed CNT/solvent with the dissolved polymer. Conventional dispersion characterization techniques were complemented with analysis of the shear-induced crystallization (SIC) behavior of the semicrystalline nanocomposite, which was found to be particularly sensitive to the state of nanoparticle dispersion. While Stage 1 sonication was found to have a pronounced effect on the nanoparticle dispersion as characterized via SIC and thermal characterization, the impact of Stage 2 sonication on the level of nanoparticle dispersion was much smaller. Such results demonstrate the utility of characterization of the shear-induced crystallization behavior as a means to analyze nanoparticle dispersion in semicrystalline polymer nanocomposites. (C) 2016 Wiley Periodicals, Inc.