Review on the Processing and Properties of Polymer Nanocomposites and Nanocoatings and Their Applications in the Packaging, Automotive and Solar Energy Fields

Abstract

For the last decades, nanocomposites materials have been widely studied in the scientific literature as they provide substantial properties enhancements, even at low nanoparticles content. Their performance depends on a number of parameters but the nanoparticles dispersion and distribution state remains the key challenge in order to obtain the full nanocomposites' potential in terms of, e.g., flame retardance, mechanical, barrier and thermal properties, etc., that would allow extending their use in the industry. While the amount of existing research and indeed review papers regarding the formulation of nanocomposites is already significant, after listing the most common applications, this review focuses more in-depth on the properties and materials of relevance in three target sectors: packaging, solar energy and automotive. In terms of advances in the processing of nanocomposites, this review discusses various enhancement technologies such as the use of ultrasounds for in-process nanoparticles dispersion. In the case of nanocoatings, it describes the different conventionally used processes as well as nanoparticles deposition by electro-hydrodynamic processing. All in all, this review gives the basics both in terms of composition and of processing aspects to reach optimal properties for using nanocomposites in the selected applications. As an outlook, up-to-date nanosafety issues are discussed.

Keywords: barrier improvement; electrospraying; light-weight materials; nanocomposite; nanodeposit; self-cleaning surfaces.

Figure 1

Different types of composites arising from the interaction of layered silicates and polymer. (I) Phase separated microcomposite, (II) intercalated nanocomposites and (III) exfoliated nanocomposites. Adapted from [31].

Figure 2

Melt intercalation synthesis of polymer/clay nanocomposite. Adapted from [27].

Figure 3

Mechanism of clay dispersion and exfoliation during melt processing. Adapted from [48,50].

Figure 4

Surface of a polyethylene terephthalate film with particle, partially covered by a SiO_x layer (Source: Fraunhofer IVV) [80].

Figure 5

Comparison of oxygen permeability (OP) and water vapour transmission rate (WVTR) properties for different polymers normalized to 100 µm thickness. Source: Fraunhofer IVV [55].

Figure 6

“Tortuous pathway” created by incorporation of exfoliated clay nanoplatelets into a polymer matrix film. In a film composed only of polymer (I), diffusing gas molecules on average migrate via a pathway that is perpendicular to the film orientation in a nanocomposite (II), diffusing molecules must navigate around impenetrable particles/platelets and through interfacial zones which have different permeability characteristics than those of the virgin polymer. Adapted from [133].

Figure 7

Comparison of modulus reinforcement (relative to matrix polymer) for nanocomposites based on montmorillonite (MMT) versus glass fibre for a PA 6 matrix [141].

Figure 8

Structure of montmorillonite (phyllosilicate clay). Adapted from [133].