How the use of solvent affects the mechanical behavior of polyester resin/carbon nanotubes nanocomposites

Filler dispersion is critical in the nanocomposite feature determination. Physical methods such as sonication are usually employed to disperse carbon nanotubes inside a thermoset polymeric matrix. Those methods often use strong forces to disperse the filler but they could damage it, compromising its reinforcing action. In this paper, we have employed acetone solvent during the sonication process of carbon nanotubes and polyester resin. The solvent helps the carbon nanotube bundle dissolution and favors its homogeneous distribution inside the matrix, thus reducing the action of ultrasounds. Moreover, the carbon nanotubes employed were both pristine and properly oxidized, to favor the opening of carbon nanotube bundles. Solvent was then removed although traces remained in the mixture. We have analyzed the role of solvent during the mixing and the following polymeric network growth. The experimental analyses highlighted as the solvent interacts with the carbon nanotubes during the mixing, thus hindering the right network development. Styrene fragments remain entrapped within the network of polyester resin, softening and improving the adhesive properties. Instead, without solvent, the carbon nanotubes improve the material stiffness in the order CNTox>CNTp.