Improved Carbon Nanofiber/Polymer Composites by Low Shear Compounding

"Carbon nanofiber reinforced polymer composites are anticipated to offer a suite of physical property advantages similar to conventional carbon fiber composites reinforced with PAN- or pitch-based carbon fiber. Early results show high promise for use ofcarbon nanofibers to enhance the physical properties, including electrical conductivity, coefficient of thermal expansion, strength, and modulus, of polymer composites. An artifact of high volume methods of production for carbon nanofibers and nanotubesis that fibers are generated in a birdnested form, and are difficult to separate in compounding into a uniform dispersion throughout the matrix polymer. In order to disperse other nanoparticle additives such as carbon black or nanoclays, high shear mixingis frequently used; however, when applied to nanotubes and nanofibers, the aspect ratio of the fibers may be seriously compromised, reducing the reinforcement value of the nanofiber. As a result, the observed physical properties for carbon nanofiberreinforced polymers represent only a small fraction of the values predicted by theory. It is proposed to use methods of low shear processing, low viscosity resins and in situ polymerization to create masterbatch compounds of uniformly dispersed carbonnanofibers where the high aspect ratio of the as-grown carbon nanofiber is preserved. The Air Force has a variety of aircraft and satellite applications that a successfully developed material