Processing of polymer-based nanocomposites

Abstract

Nanocomposites are materials that incorporate nano-sized particles into a matrix of standard material. Polymer nanocomposites are defined as the combination of a polymer matrix and nano-sized additives/fillers/particles. Over the past decade, there has been a growing interest in polymer nanocomposites. This is attributed to the improved mechanical, thermal, and electrical properties that enable their use in automotive and aerospace industries. Several studies, of both experimental and theoretical nature, have been carried out to investigate the mechanical, thermal, and electrical properties of polymer matrix nanocomposites. Researchers and scientists have been evaluating the effect of organic (CNT, SWCNT, MWCNT, graphene, etc.) and inorganic (Al2O3, TiO2, SiO2, ZrO2, etc.) nano-fillers on the mechanical, electrical, tribological, and thermal properties of polymer matrix nanocomposites. In mechanical terms, nanocomposites differ from conventional composite materials due to the exceptionally high surface to volume ratio of the reinforcing phase and/or its exceptionally high aspect ratio. The reinforcing material can be made up of particles (e.g. minerals), sheets (e.g. exfoliated clay stacks), or fibers (e.g. carbon nanotubes or electrospun fibers). Fiber reinforced polymer (FRP) composites are noncrystalline and brittle. Therefore, a strengthening mechanism applicable for metals may not be suitable for polymer matrix composites because of the different failure mechanisms. In polymer matrix composites, the initiation of crack is possible either in the matrix or at the matrix/fiber interface. If the interface bond strength is sufficient enough to sustain the applied load, then the probability of crack initiation is more in the matrix as compared to the fiber. The crack propagates through the matrix and the fiber-matrix interface depending on the adhesive bond between the matrix and the fiber. Failure occurs by the gradual propagation of the microcrack in the composites. Different researchers and scientists have adopted different manufacturing processes to incorporate nanoparticles or tubes into the polymer matrix (solution processing, melt processing, in situ polymerization, sol-gel process, three-roll shear mixing, mechanical mixing, ultrasonic tip sonicator, ultrasonic bath, and ultrasonic dual mixing). The effectiveness of nanoparticles is such that the amount of material added is usually only between 0.1% and 5% by weight. However, uniform dispersion of high concentration of nano-fillers in the polymer matrix is a challenge to both researchers and academia for commercialization of polymer matrix nanocomposite materials. Therefore, in this chapter, the fabrication methods, advantages, and limitations of mixing of organic and inorganic nano-fillers into the polymer matrix composites and their properties have been discussed elaborately.