The DC Electrical Properties of Polyvinyl Alcohol / Multi-Walled Carbon Nanotube Composites

Polymer composites are intensively studied for the new properties which are given by the combination of the properties of the both polymer matrix and the filler respectively. When the concentration of the filler in the composite reaches the percolation value, the continuous bulk network structure is formed. If electrical conductive filler (Carbon black (CB)) is used, the composite properties can change from insulator to conductive ones. Electrical conductivity can change in the magnitude of several orders. The combination of polymers with carbon nanotubes allows linking the properties of both materials to form new functional materials. Samples were prepared in three steps. First, the solution samples were prepared by dissolving 1wt% sodium dodecyl sulfate (SDS) in distilled water using magnetic stirrer (corning hot plate stirrer PC-351) at 25 0 C for 1 hr. In the second step different weights of Multi-walled Carbon nanotube (CNT) in volume fraction (0.004, 0.009, 0.019, 0.029 and 0.038) were dispersed in the SDS/H2O solutions by using a high power ultrasonic homogenizer at 0 °C for 20min. Finally, solutions were prepared by dissolving 8wt % of poly vinyl alcohol (PVA) in sonicated solutions by using a magnetic stirrer at 80 0 C for 2hr. From the filler content (CNT) dependence of the electrical (DC) conductivity of PVA composites, we notice that in the case of very low filler concentration, the composites conductivity remain almost the same of that of the polymeric matrix. If the filler loading exceeds a certain critical value, however, a drastic rise in the composites conductivity by several orders of magnitude can occur. The present study is aimed to study the effect of carbon nanotube (CNT) filler on physical properties of poly vinyl alcohol (PVA) loaded with different CNTfiller. In addition the effect of CNT filler on the DC electrical properties of PVA samples will be elucidated. Keywords—Polyvinyl alcohol, multi-walled carbon nanotube, DC electrical properties Introduction In recent years, studies on the electrical and optical properties of polymers have attracted much attention in view of their applications in electronic and optical devices. The electrical properties are aimed to understand the nature of the charge transport prevalent in these materials while the optical properties are aimed to achieving better reflection, antireflection, and polarization properties. Electrical and optical properties of the polymers can be suitably modified by the addition of dopant depending on their reactivity with the host matrix. Moreover the advantages of polymer materials such as high strength, good mold ability, and flexibility could be combined with the great properties of inorganic materials such as high strength, heat strength, heat stability, and chemical resistance through producing composite materials [1-3]. The wide range applications of nano-fillers such as filters, catalysis, tissue engineering, wound dressing, scaffold, and sensors could be extended with enhancing their mechanical, electrical, optical, thermal, and magnetic properties by incorporating inorganic and organic nanoparticles in their structures [4-6]. Conductive filler particles in an insulating matrix are able to lower the overall resistivity by several orders of magnitude when a network develops throughout the matrix. The transition from an insulating to a conducting composite as a function of filler concentration is known as percolation and the critical concentration at which this drop occurs is called percolation threshold. Percolation is described by many theories using different approaches. Some of them take into account the dependence of the percolation threshold on the filler shape, size or aspect ratio, based upon excluded volume approach of infinitely thin particles. Another approach considers the dependency on the orientation of finitely thick sticks [7]. Experimental PVA powder (Mw = 72000 g/mol, 98% hydrolyzed) as a polymer was obtained from Merck and MWCNT (purity = 95%, diameter ~ 10 nm, Length: 30 μm) were supplied from Neutrino Company. Sodium dodecyl Journal of Multidisciplinary Engineering Science and Technology (JMEST) ISSN: 3159-0040 Vol. 2 Issue 5, May 2015 www.jmest. org JMESTN42350633 885 sulfate (SDS) was obtained from Sigma-Aldrich. The solvent used for dissolving PVA and PVA/SDS/CNT dispersion was distilled water. All reagents used were of analytical grade and were used as received without further purification. a-) Preparation of Sample Solutions were prepared in three steps. First, the solution samples were prepared by dissolving 1wt% SDS in distilled water using magnetic stirrer (corning hot plate stirrer PC-351) at 25 0C for 1 hr. In the second step; different weights of CNT were dispersed in the SDS/H2O solutions by using a high power ultrasonic homogenizer (UP200, Germany) at room temperature for 20min. 8wt% of PVA in sonicated solutions by using a magnetic stirrer at 80 0 C for 2hr. The calculated CNTs concentrations in each composition of any sample are listed in Table 1. Table 1: Concentrations of CNT, SDS, and PVA in the mixed solutions Mass in 100ml H20 CNT Mass ratio (wt%) PVA(mg) SDS(mg) CNT(mg)