Electrical properties polymer nanofibers

The wide assortment of polymer systans (polypropylene, poly(methyl methacrylate) [PMMA], polyepoxide, polystyrol, PC, etc.) is used as a polymeric matrix for nanocomposites production (Ray and Okamoto 2003). The most well-known fillers of polymeric matrix are nanoparticles (silica, metal, and other organic and inorganic particles), layered materials (graphite, layered aluminosilicates, and other layered minerals), and fibrous materials (nanofibers and nanotubes) (Thostenson et al. 2005). Nanocomposite polymer materials containing metal or metal oxide particles attract growing interest due to their specific combination of physical and electric properties (Rozenberg and Tenne 2008, Zezin et al. 2010). Nanocomposites on the base of layered materials... 

The dimensions of the added nanoelements also contribute to the characteristic properties of PNCs. Thus, when the dimensions of the particles approach the fundamental length scale of a physical property, they exhibit unique mechanical, optical and electrical properties, not observed for the macroscopic counterpart. Bulk materials comprising dispersions of these nanoelements thus display properties related to solid-state physics of the nanoscale. A list of potential nanoparticulate components includes metal, layered graphite, layered chalcogenides, metal oxide, nitride, carbide, carbon nanotubes and nanofibers. The performance of PNCs thus depends on three major attributes nanoscopically confined matrix polymer, nanosize inorganic constituents, and nanoscale arrangement of these constituents. The current research is focused on developing tools that would enable optimum combination of these unique characteristics for best performance of PNCs. 

Carbon nanotubes (CNTs) and carbon nanofibers (CNFs), due to their unique structure and properties, appear to offer quite promising potential for industrial application [236]. As prices decrease, they become increasingly affordable for use in polymer nanocomposites as structural materials in many large scale applications. In fact, three applications of multiwall CNT have been discussed recently first, antistatic or conductive materials [237] second, mechanically reinforced materials [238,239] and third, flame retarded materials [240,241]. The success of CNTs in the field of antistatic or conductive materials is based on the extraordinary electrical properties of CNTs and their special geometry, which enables percolation at very low concentrations of nanotubes in the polymer matrix [242]. 

C.-C. Wang, J.-F. Song, H.-M. Bao, Q.-D. Shen, and C.-Z. Yang, Enhancement of electrical properties of ferroelectric polymers by polyaniline nanofibers with controllable conductivities, Adv. Funct. Mater., 18, 1299-1306 (2008). 

I. S. Chronakis, S. Grapenson, and A. Jakob, Conductive polypyrrole nanofibers via electrospinning electrical and morphological properties. Polymer, 47, 1597-1603 (2006). 

HGURE 4.4 Electrical properties of polymer composites. (A) The electrical conductivity of the PS/graphene composite as a function of graphene volume fraction. (B) The electrical conductivity of directly mixing (DM) CNT/PANI and CNT/ PANI nanofibers with different CNT contents in the directions being parallel and perpendicular to the fiber axis. 

Zhou Z., Lai C., Zhang L., Qian Y, Hou H., Reneker D. H., and Fong H., Development of carbon nanofibers from aligned electrospun polyacrylonitrile nanofiber bundles and characterization of their microstructural, electrical, and mechanical properties. Polymer, 2009, 50,2999-3006. 

The fabrication of PEDOT nanofiber, nanotube and nanowire has been mainly focused on the AAO membrane, because AAO has advantages such as rigid shape, uniform diameter, and various pore sizes [364-368]. Electrochemical polymerization was performed in the pores of AAO membrane using SDS, LiC104 and EDOT solution and measured the resistance of the PEDOT nanofiber with a diameter of 35 nm and 150 nm, respectively. The resistance of PEDOT nanofiber was between 1.5 K and 300 K and the resistance ratio of R(T)/R (300 K) was the relevant term to investigate the intrinsic electrical properties of the conducting polymer. The resistance ratio increased... 

The parameters involved in the electrospinning processes that affect the nanofiber geometry and structure can be divided into two groups (i) System parameters such as polymer molecular weight, molecular weight distribution, polymer architecture (branched, linear), concentration of the polymer solution and its properties, including viscosity, electrical conductivity, and surface tension and (ii) Process parameters such as applied electric voltage, polymer flow rate, distance between the needle tip and the collector, ambient parameters such as temperature, humidity, and air velocity in the chamber, and motion of the collector (Frenot and Chronakis 2003). 

Liao C-C, Wang C-C, Chen C-Y and Lai W-J (2011) Stretching-induced orientation of polyacrylonitrile nanofibers by an electrically rotating viscoelastic jet for improving the mechanical properties, Polymer 52 2263-2275. 

Polymer composites reinforced with electrospun polymer nanofibers have so far been developed mainly for providing some outstanding physical e.g., optical and electrical) and chemical properties [20,21], Most of the applications at present focus on very small quantity usage for instance, reinforcement of dental resins, thin films, or in the case of large scale composites parts, only as additional ply interface reinforcement between composite laminates [21], As mentioned before, the biggest issues remain fiber alignment and collection at reasonable production rates. Therefore, large scale production (both quantity and size) of SPCs may benefit more from the methods described in Sections 19,2.3 and 19.4.1. 

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