Authors: H. Mahfuz, M.M. Hasan, V.K. Rangari and S. Jeelani
Affilation: Tuskegee University, United States
Pages: 86 - 89
Keywords: nanocomposites, nylon, filaments, nanotubes, nanofibers
It has been demonstrated in recent years that infusion of nanoparticles in thermoset as well as in thermoplastic polymers can help improve the chemical, thermal, and mechanical properties significantly. The improvement in properties can be achieved at very low nanoparticles loading (most of the cases „T 3% by weight). The shape of nanoparticles can be spherical, layered, irregular and acicular or rod-shaped. It is believed that the properties of the polymer can be maximized by aligning the rod-shaped particles along preferred directions. The improvement in properties due to alignment of nanoparticles is influenced by two factors; (a) physio-chemical effect on the polymer structure, and (b) load transfer mechanism. In the present study infusion of vapor grown carbon nanofibers (CNF), and multi-walled carbon nanotubes (MWCNT) into a thermoplastic polymer, Nylon-6 was first investigated. Carbon nanofibers were „T200nm in diameter and 50-100ƒ_m in length. On the other hand MWCNTs were around 10-15 nm in diameter and about 5ƒ_m long. These nanoparticles with 1% wt loading were dry-mixed with Nylon-6 by mechanical means, melted in a single screw extrusion machine, and then extruded through an orifice. Extruded filaments were later stretched and stabilized by sequentially passing them through a set of tension adjusters and a secondary heater. Stabilized filaments of about 80-100 micron dia were finally wound into spools in a filament winder. Two sets of filaments; one with CNF and the other with MWCNT were extruded. Individual filaments were then tested under tension. The enhancement in strength and stiffness were phenomenal. In both cases the enhancement in properties was in the 70-100% range. This remarkable increase in strength and stiffness was clearly due to the alignment of acicular reinforcements during the extrusion process.