Impact of Ultrasonication on Carbon Nanotube Demixing and Damage in Polymer Nanocomposites

Abstract

The processing technique can significantly impact how nanoparticles are distributed and dispersed within a polymeric matrix. Homogeneity in spatial distribution and effective nanoparticle dispersion are necessary to achieve optimal polymer nanocomposite properties and can be a processing challenge. Here in particular we study the impact of ultrasonication on the dispersion and distribution of carbon nanotubes (CNTs) in the polymer nanocomposite. Specifically, we seek to better understand the interplay between nanotube demixing and damage for excessive sonication times. Here polymer nanocomposite samples of poly(caprolactone) (PCL) were mixed with CNTs using a ultrasonication process where the samples are subjected to different durations of CNT/solvent sonication. In addition to common dispersion characterization techniques, an analysis of mixing indices and the shear-induced crystallization behavior of the nanocomposites were found to be particularly insightful when used to study the effects of sonication time on nanoparticle dispersion. Findings based on TEM evidence of CNT damage, optical image analysis, and the shear-induced crystallization behavior of the samples suggest that mechanisms of demixing and damage of the CNTs co-exist within the processed nanocomposite and that both contribute to the reduction in effective properties for excessive sonication times.