Graphene-Incorporated Natural Fiber Polymer Composites: A First Overview

Abstract

A novel class of graphene-based materials incorporated into natural lignocellulosic fiber (NLF) polymer composites is surging since 2011. The present overview is the first attempt to compile achievements regarding this novel class of composites both in terms of technical and scientific researches as well as development of innovative products. A brief description of the graphene nature and its recent isolation from graphite is initially presented together with the processing of its main derivatives. In particular, graphene-based materials, such as nanographene (NG), exfoliated graphene/graphite nanoplatelet (GNP), graphene oxide (GO) and reduced graphene oxide (rGO), as well as other carbon-based nanomaterials, such as carbon nanotube (CNT), are effectively being incorporated into NLF composites. Their disclosed superior mechanical, thermal, electrical, and ballistic properties are discussed in specific publications. Interfacial shear strength of 575 MPa and tensile strength of 379 MPa were attained in 1 wt % GO-jute fiber and 0.75 wt % jute fiber, respectively, epoxy composites. Moreover, a Young's modulus of 44.4 GPa was reported for 0.75 wt % GO-jute fiber composite. An important point of interest concerning this incorporation is the fact that the amphiphilic character of graphene allows a better way to enhance the interfacial adhesion between hydrophilic NLF and hydrophobic polymer matrix. As indicated in this overview, two basic incorporation strategies have so far been adopted. In the first, NG, GNP, GO, rGO and CNT are used as hybrid filler together with NLF to reinforce polymer composites. The second one starts with GO or rGO as a coating to functionalize molecular bonding with NLF, which is then added into a polymeric matrix. Both strategies are contributing to develop innovative products for energy storage, drug release, biosensor, functional electronic clothes, medical implants, and armor for ballistic protection. As such, this first overview intends to provide a critical assessment of a surging class of composite materials and unveil successful development associated with graphene incorporated NLF polymer composites.

Keywords: ballistic armor; graphene; mechanical behavior; natural fiber composite; thermal analysis.

Figure 1

Publications by year for different material classes, according to Scopus database [3]: (a) “Composite materials”, “Polymer composites”, and “Polymer composites and fiber”; (b) “Natural fiber and composite” and “Natural fiber and composite and graphene”. In corresponding equations, y is the number of publications, and x is the year.

Figure 1

Publications by year for different material classes, according to Scopus database [3]: (a) “Composite materials”, “Polymer composites”, and “Polymer composites and fiber”; (b) “Natural fiber and composite” and “Natural fiber and composite and graphene”. In corresponding equations, y is the number of publications, and x is the year.

Figure 2

A schematic summarizing the main manufacturing processes and graphene-based materials used in composites.

Figure 3

Young’s modulus (E_f) of graphene-based materials as a function of the modulus of the matrix (E_m): (a) graphene oxide (GO); (b) reduced graphene oxide (rGO). Adapted from [114].

Figure 4

Ashby plot of Young’s modulus vs. tensile strength comparing the mechanical properties of natural fiber-based polymer composites* with glass fiber–reinforced plastic (GFRP) and carbon fiber–reinforced plastic (CFRP), with carbon nanotube (CNT), and graphene–based polymer composites. *The mechanical properties of natural fiber-polymer composites, natural lignocellulosic fiber (NLF)/graphene-based composites, and NLF/graphene material were based in many reported values from the literature, as shown in Table 2. Adapted from [81].

Figure 5

Properties of jute/epoxy composites incorporated and non-incorporated with rGO: (a) tensile, (b) flexural, (c) compression, and (d) Izod impact resistance. Adapted from [49].

Figure 6

SEM microphotographs of: (a) pristine GNP; (b) composite filled with 5 wt % GNP showing agglomerated GNPs. Adapted from [73].

Figure 7

SEM micrograph of bagasse flour/PP incorporated with 1 wt % of GO filler. Inset displays the agglomeration of the filler in the fractured surface. Adapted from [71].

Figure 8

Fracture surface micrographs of PP composites: (a) SF/PP composite; (b) GO-SF/PP composite; (c) SF/MAPP-PP composite; (d) GO-SF/MAPP-PP composite. Reproduced with permission from [53].

Figure 9

Dynamic modulus behavior for different amounts of (a) neat piassava fibers and (b) GO-coated piassava fibers. Adapted from [40].

Figure 10

Thermal behavior of sisal/PP composite with the incorporation of GO (fiber) and MAPP (matrix): (a) TGA curves, and (b) DSC analysis. Adapted from [53].

Figure 11

SEM micrograph displaying several micro mechanisms of failure observed in NLFs polymer composites under ballistic impact. Adapted from [158].

Figure 12

Multilayer armor system using curaua/epoxy composites as second layer: (a) CF before test, (b) CF after test, (c) GOCF before test, and (d) GOCF after test. Adapted from [51].

Figure 13

Water absorption of different sisal/PP composites after 45 days. Adapted from [53].