Polymer Nanohybrids With High Electrical Conductivities
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Polymer Nanohybrids With High Electrical Conductivities R. Yañez-Macías1, P. González-Morones1, C. Ávila-Orta1, S. Torres-Rincón1, J. Valdéz-Garza1, A. Rosales-Jasso1, J.G. Telles-Padilla1, A. Saénz-Galindo2 1 Research Center for Applied Chemistry (CIQA), Blvd. Enrique Reyna No 140, C. P. 25253, Saltillo, Coah. 2
Faculty of Chemical Sciences, Autonomous University of Coahuila (UAC), Blvd V. Carranza s/n, Col. República Oriente, Saltillo, Coah. . ABSTRACT Multiwalled carbon nanotube (MWCNT)/Nylon-6 nanohybrids were prepared by in situ polymerization under microwave irradiation. The effect of time and power of irradiation on the surface conductivity of the nanohybrid was studied. It was observed that the resistivity increases with irradiation time at low microwave power (200W). On the other hand, at high power (600W) an opposite behavior was observed. And at intermediate power (400W) the resistivity was independent of the irradiation time. Resistivity values range from 102 to 101 Ω/sq. This behavior was associated with the polymer nanocoating covering the surface of the carbon nanotubes. INTRODUCTION The use of microwave energy is an alternative method to carry out polymerization reactions due to its selective and effective heating. [1] Because of the structure, carbon nanotubes (CNT) and ε-caprolactam can absorb this type of energy [2] making it possible to heat and reach the necessary reaction temperature. The term nanohybrid involves covalently linking a functional group directly to the surface of a nanoparticle. The defect sites on the CNTs surface allow attachment of functional groups or polymer moieties3. The functionalization of CNTs with polymers might represent some advantages to ensure the compatibility of the nanoparticle with the polymer matrix or to fabricate conductive materials such as nanotubes but with polymer properties. EXPERIMENTAL DETAILS Reactive grade ε-caprolactam (monomer) and aminocaproic acid (initiator) were obtained from Sigma Aldrich, MWCNT were purchased from Nanoamor Inc. USA (purity 95%, average external diameter 30-50 nm, length 10-20 μm). The microwave polymerizations were conducted in a MARS X microwave oven with an operating power of 200, 400, 600 W and frequency of 2.45 GHz. To synthesize Nylon-6/MWCNT nanocomposites, amounts of 26.1 g of ε-caprolactam, 3.9 g of aminocaproic acid and 0.6 g of MWCNT were ground and mixed together and placed into a quartz vessel. The reaction temperature was 230°C. The products were first dissolved in formic acid, and subsequently washed with methanol to remove residual monomer, this
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procedure was repeated at least three times. Finally the nanocomposite was precipitated in water. The final product was dried in a vacuum oven at 60°C for 12 hours prior to subsequent characterization. To obtain MWCNT/Nylon-6 nanohybrids, a certain amount of nanocomposite were first dissolved in formic acid, prior to being filtered using a 0.2 μm polycarbonate membrane. The resulting solids were washed with formic acid in order to remove the ungrafted polymer. Th
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