Effects of graphene on the behavior of chitosan and starch nanocomposite films

Effective reinforcement of plasticized starch by the incorporation of graphene, graphene oxide and reduced graphene oxide

Plasticized starch (PLS) nanocomposite films using glycerol and reinforced with graphene (G) and graphene oxide (GO) were prepared by solvent casting procedure. On one hand, the influence of adding different G contents into the PLS matrix was analyzed. In order to improve the stability of G nanoflakes in water, Salvia extracts were added as surfactants. The resulting nanocomposites presented improved mechanical properties. A maximum increase of 287 % in Young's modulus and 57 % in tensile strength was achieved for nanocomposites with 5 wt% of G. However, it seemed that Salvia acted as co-plasticizer for the PLS. Moreover, the addition of the highest G content led to an improvement of the electrical conductivity close to 5 × 10-6 S/m compared to the matrix. On the other hand, GO was also incorporated as nanofiller to prepare nanocomposites. Thus, the effect of increasing the GO content in the final behavior of the PLS nanocomposites was evaluated. The characterization of GO containing PLS nanocomposites showed that strong starch/GO interactions and a good dispersion of the nanofiller were achieved. Moreover, the acidic treatment applied for the reduction of the GO was found to be effective, since the electrical conductivity was 150 times bigger than its G containing counterpart.

Surfactant-Free Stabilization of Aqueous Graphene Dispersions Using Starch as a Dispersing Agent

Attention to graphene dispersions in water with the aid of natural polymers is increasing with improved awareness of sustainability. However, the function of biopolymers that can act as dispersing agents in graphene dispersions is not well understood. In particular, the use of starch to disperse pristine graphene materials deserves further investigation. Here, we report the processing conditions of aqueous graphene dispersions using unmodified starch. We have found that the graphene content of the starch-graphene dispersion is dependent on the starch fraction. The starch-graphene sheets are few-layer graphene with a lateral size of 3.2 μm. Furthermore, topographical images of these starch-graphene sheets confirm the adsorption of starch nanoparticles with a height around 5 nm on the graphene surface. The adsorbed starch nanoparticles are ascribed to extend the storage time of the starch-graphene dispersion up to 1 month compared to spontaneous aggregation in a nonstabilized graphene dispersion without starch. Moreover, the ability to retain water by starch is reduced in the presence of graphene, likely due to environmental changes in the hydroxyl groups responsible for starch-water interactions. These findings demonstrate that starch can disperse graphene with a low oxygen content in water. The aqueous starch-graphene dispersion provides tremendous opportunities for environmental-friendly packaging applications.

Polymer nanocomposites having a high filler content: synthesis, structures, properties, and applications

The recent development of nanoscale fillers, such as carbon nanotubes, graphene, and nanocellulose, allows the functionality of polymer nanocomposites to be controlled and enhanced. However, conventional synthesis methods of polymer nanocomposites cannot maximise the reinforcement of these nanofillers at high filler content. Approaches for the synthesis of high content filler polymer nanocomposites are suggested to facilitate future applications. The fabrication methods address the design of the polymer nanocomposite architecture, which encompasses one, two, and three dimensional morphologies. Factors that hamper the reinforcement of nanostructures, such as alignment, dispersion of the filler and interfacial bonding between the filler and polymer, are outlined. Using suitable approaches, maximum potential reinforcement of nanoscale fillers can be anticipated without limitations in orientation, dispersion, and the integrity of the filler particle-matrix interface. High filler content polymer composites containing emerging materials such as 2D transition metal carbides, nitrides, and carbonitrides (MXenes) are expected in the future.

Bio- and Fossil-Based Polymeric Blends and Nanocomposites for Packaging: Structure⁻Property Relationship

In the present review, the possibilities for blending of commodities and bio-based and/or biodegradable polymers for packaging purposes has been considered, limiting the analysis to this class of materials without considering blends where both components have a bio-based composition or origin. The production of blends with synthetic polymeric materials is among the strategies to modulate the main characteristics of biodegradable polymeric materials, altering disintegrability rates and decreasing the final cost of different products. Special emphasis has been given to blends functional behavior in the frame of packaging application (compostability, gas/water/light barrier properties, migration, antioxidant performance). In addition, to better analyze the presence of nanosized ingredients on the overall behavior of a nanocomposite system composed of synthetic polymers, combined with biodegradable and/or bio-based plastics, the nature and effect of the inclusion of bio-based nanofillers has been investigated.

Graphene Nanoplatelets-Based Advanced Materials and Recent Progress in Sustainable Applications

Graphene is the first 2D crystal ever isolated by mankind. It consists of a single graphite layer, and its exceptional properties are revolutionizing material science. However, there is still a lack of convenient mass-production methods to obtain defect-free monolayer graphene. In contrast, graphene nanoplatelets, hybrids between graphene and graphite, are already industrially available. Such nanomaterials are attractive, considering their planar structure, light weight, high aspect ratio, electrical conductivity, low cost, and mechanical toughness. These diverse features enable applications ranging from energy harvesting and electronic skin to reinforced plastic materials. This review presents progress in composite materials with graphene nanoplatelets applied, among others, in the field of flexible electronics and motion and structural sensing. Particular emphasis is given to applications such as antennas, flexible electrodes for energy devices, and strain sensors. A separate discussion is included on advanced biodegradable materials reinforced with graphene nanoplatelets. A discussion of the necessary steps for the further spread of graphene nanoplatelets is provided for each revised field.

Study on the effect of graphene and glycerol plasticizer on the properties of chitosan-graphene nanocomposites via in situ green chemical reduction of graphene oxide

Unplasticized and glycerol plasticized chitosan/graphene (CS/GS) nanocomposites were synthesized via in situ chemical reduction of graphene oxide sheets (GO) with l-ascorbic acid (L-AA) as reductant by solution casting. The reduction of GO with L-AA was investigated to establish the optimal amount of reductant required to produce chemically reduced graphene sheets (GS). The combine effect of both nanofiller and glycerol on the structure, thermal, mechanical, and electrical properties of CS/GS nanocomposite films was evaluated. Materials were characterized by FT-IR, NMR, UV-Vis, XPS, XRD, Raman, SEM, TEM, and TGA. The results showed that GS sheets were homogeneously dispersed throughout the CS matrix, and that interactions between CS and the surface of GS took place. When compared with neat CS, nanocomposites showed a decrease in the crystallinity, better thermal stability under oxidative atmosphere, and improved mechanical properties, while maintained the thermal properties of CS under inert conditions. Combined use of glycerol and GS led to substantially enhanced mechanical properties. The electrical conductivity was increased with increasing GS loading in nanocomposite. This study demonstrates how CS/GS nanocomposites performance properties can be tailored by controlling GsS and plasticizer content.

Recent Advances in Nanocomposite Materials of Graphene Derivatives with Polysaccharides

This review article presents the recent advances in syntheses and applications of nanocomposites consisting of graphene derivatives with various polysaccharides. Graphene has recently attracted much interest in the materials field due to its unique 2D structure and outstanding properties. To follow, the physical and mechanical properties of graphene are then introduced. However it was observed that the synthesis of graphene-based nanocomposites had become one of the most important research frontiers in the application of graphene. Therefore, this review also summarizes the recent advances in the synthesis of graphene nanocomposites with polysaccharides, which are abundant in nature and are easily synthesized bio-based polymers. Polysaccharides can be classified in various ways such as cellulose, chitosan, starch, and alginates, each group with unique and different properties. Alginates are considered to be ideal for the preparation of nanocomposites with graphene derivatives due to their environmental-friendly potential. The characteristics of such nanocomposites are discussed here and are compared with regard to their mechanical properties and their various applications.

Polysaccharide-assisted rapid exfoliation of graphite platelets into high quality water-dispersible graphene sheets

High quality graphene has been obtained by polysaccharide-assisted ultrasonication in aqueous medium. This approach provides an economical, solvent-free, high-yield, and industrially scalable route for new applications of graphene-based nanocomposites.

Recent progress in chemical modification of starch and its applications

Starch has received much attention as a promising natural material both in biomedical fields and waste water treatment due to its unique biological and adsorptive properties.