Evaluation of mechanical and dynamic mechanical properties of multiwalled carbon nanotube-based ethylene–propylene copolymer composites mixed by masterbatch dilution

Abstract

A two-step masterbatch mixing technique was studied for preparation of carbon nanotube-filled ethylene–propylene diene elastomer compounds, and compared to conventional one-step mixing process. In the two-step process, a masterbatch compound with carbon nanotube content of 50 parts per hundred was prepared by melt-mixing ethylene–propylene diene elastomer. This material was then compounded with pristine ethylene–propylene diene elastomer and composites with different carbon nanotube concentrations were compared. The aim of this study is to compare the efficiency of two different mixing processes on the dispersion of carbon nanotubes and to facilitate the handling of carbon nanotubes, as the masterbatch can be prepared in a controlled way and used for further dilution without the problems related to carbon nanotube processing. The compound properties were studied with emphasis on mechanical characterization and dynamic mechanical thermal analysis. Masterbatch mixing resulted in the similar mechanical properties of the composites compared to the direct mixing method. At the relatively low loadings of carbon nanotubes, the considerable improvements of the mechanical properties were observed. The aspect ratio of the carbon nanotubes determined by transmission electron microscope was found to be similar to the one calculated from the Guth equation. It showed a considerable reduction in aspect ratio independent of the used mixing method.