Oxidized carbon nanofiber/polymer composites prepared by chaotic mixing

Composites of oxidized carbon nanofibers (ox-CNFs) and polymethyl methacrylate and thermoplastic polyurethane (TPU) were prepared in a chaotic mixer and their electrical and mechanical properties were compared with those prepared using untreated carbon nanofibers (CNFs). X-ray photoelectron spectroscopy data of ox-CNFs showed higher oxygen to carbon ratio than CNFs indicating the presence of polar functional groups on the surfaces of ox-CNFs. Consequently, dispersion of ox-CNFs improved in both polymers and the resultant composites showed improved thermal-oxidative stability, higher storage modulus, and higher glass transition temperature. The electrical conductivity, however, decreased with improved nanofiber dispersion. In the case of TPU/ox-CNF composites, maximum values of tensile strength and Young's modulus were obtained with 1 wt.% fiber content; higher amounts of ox-CNFs promoted phase mixing of soft and hard segment domains and consequently caused a reduction in tensile properties. (c) 2007 Elsevier Ltd. All rights reserved.