Lalatendu Nayak

Super Heat-Resistant Conductive Nanocomposites Based on Polysulfone–Carbon Nanofillers

The present article describes the morphology, mechanical, thermal, electrical, and dielectric properties of polysulfone (PSU) nanocomposites filled with different concentrations of multiwalled carbon nanotubes (MWCNT) and carbon nanofibers (CNF) [Only one carbon material per each]. The tensile strength and tensile modulus of both MWCNT- and CNF-filled nanocomposites increased with the increase in filler loading up to 3 wt.%. The addition of 3 wt.% CNF led to increase in tensile strength and modulus by 22% and 46%, respectively. Similarly at the same loading of MWCNT, the tensile strength and tensile modulus increased by 16% and 44%, respectively. Thermogravimetric analysis indicated continuous upgrade in thermal stability compared to pure PSU matrix up to 3 wt.% nanofiller loading. Electrical conductivity of both nanocomposites obeyed a power law model of the percolation theory having very low percolation threshold of 0.0079 (0.9 wt.%) for PSU/CNF nanocomposite and 0.014 (1.5 wt.%) for PSU/MWCNT nanocomposite. Dielectric properties of nanocomposites were enhanced significantly with increasing MWCNT/CNF concentration, but decreased with increasing frequency. The dielectric constant reached to 8.5 × 109 (100 Hz) at 5 wt.% MWCNT and 5.4 × 1010 at 5 wt.% CNF, respectively, from the neat PSU matrix (2.1 at 100 MHz). The current (I)–voltage (V) characteristics exhibited ohmic conduction at and above the percolation threshold for both MWCNT- and CNF-filled nanocomposites. GRAPHICAL ABSTRACT

Electrical Conductivity of Polymer–Carbon Composites: Effects of Different Factors

In this chapter, the electrical conductivity/resistivity of polymer–carbon composites has been discussed in detail. The types of electrical resistivity and their measurement procedure have been depicted pictorially. The electrical conductivity of different carbon materials like diamond, graphite, fullerene, carbon fiber, carbon black, carbon nanotubes, and graphene are noted and discussed. The different techniques of preparation/processing of conducting polymer/carbon composites are mentioned here within short. Moreover, how the geometry/structure of different carbons controls the electrical conductivity of polymer composites has been critically reviewed. The electrical percolation threshold and the conductivity of polymer/carbon composites that depends on many physical and chemical factors are investigated from different literature sources and reported in this chapter.

Surface Modification/Functionalization of Carbon Materials by Different Techniques: An Overview

Carbon materials have agglomeration tendency because of high van der Wall force of interaction among the carbon particles. This agglomeration tendency has been an obstacle for their application in different fields. In order to reduce this agglomeration tendency and to explore their application areas, different surface modification/functionalization processes have been successfully developed by researchers. Surface functionalization reduces the agglomerating tendency of carbon materials and increases the carbon–polymer interfacial adhesion through covalent or ionic bonds. This chapter aims to depict an overview on the different types of surface functionalization techniques applied to different carbon materials like carbon blacks (CB), carbon nanotubes (CNTs), carbon nanofibers (CNFs), graphenes, and fullerenes. The methodology like wet oxidation (oxidation using nitric acid, sulfuric acid, hydrogen peroxide, potassium permanganate, etc.), dry oxidation (oxidation with air, ozone, plasma, etc.), amidation, silanization, silylation, polymer grafting, polymer wrapping, surfactant adsorption, and encapsulation have been presented with different examples. All the functionalization processes have been highlighted with their specific application. The gathering of different functionalization processes in this chapter will provide deep understanding regarding the selection of a particular technique for specific application.