In this paper, bamboo charcoals (BCs) were considered as alternative ecofriendly and sustainable carbon-based nanoparticles because of their good affinity with water-soluble biopolymer poly(vinyl alcohol) (PVA) to achieve strong PVA/BC nanocomposites. Two different types of BC particles, namely microdiameter bamboo charcoals (MBCs) and nanodiameter bamboo charcoals (NBCs) were successfully fabricated by the solution casting method. Nanofiller reinforcement effect was investigated from BC particle size and dispersion, morphological structures, and interfacial interactions between BCs and PVA matrices. Overall, the addition of NBCs yields increasingly higher mechanical properties of PVA/BC nanocomposites when compared with that of MBCs. The maximum enhancements in tensile moduli of nanocomposites were achieved up to 123% and 100% with the inclusion of 10 wt % NBCs and MBCs, respectively, whereas corresponding tensile strengths were improved by 110% and 72% with the incorporation of 3 wt % NBCs and MBCs accordingly, as opposed to those of PVA. Such findings obtained may be attributed to more uniform BC particle dispersion in PVA/BC nanocomposites and better interfacial interactions between BCs and PVA matrices. Tensile moduli of PVA/BC nanocomposites were predicted by Halpin−Tsai model and combined Mori-Tanaka model and laminate theory in both BC well-aligned and randomly oriented states, suggesting that the introduction of effective volume fractions of randomly oriented BCs led to the best modulus estimation. This study confirms the necessity of using BCs to replace conventional carbon-based nanofillers for developing more economical and eco-friendly nanocomposites.
Carbon-based nanofillers, such as carbon nanotubes (CNTs) and graphene sheets are considered as effective nanoreinforcements due to their unique structures and material performance. However, the utilisation of such nanofillers can be hindered owing to a high level of nanotoxicity via human inhalation and high material cost for CNTs, as well as the
Mechanical properties of polymer nanocomposites depend primarily on nanointerphases as transitional zones between nanoparticles and surrounding matrices. Due to the difficulty in the quantitative characterisation of nanointerphases, previous literature generally deemed such interphases as one-dimensional uniform zones around nanoparticles by assumption for analytical or theoretical modelling. We hereby have demonstrated for the first time direct three-dimensional topography and physical measurement of nanophase mechanical properties between nanodiameter bamboo charcoals (NBCs) and poly (vinyl alcohol) (PVA) in polymer nanocomposites. Topographical features, nanomechanical properties and dimensions of nanointerphases were systematically determined via peak force quantitative nanomechanical tapping mode. Significantly different mechanical properties of nanointerphases were revealed as opposed to those of individual NBCs and PVA matrices. Non-uniform irregular three-dimensional structures and shapes of nanointerphases are manifested around individual NBCs, which can be greatly influenced by nanoparticle size and roughness, and nanoparticle dispersion and distribution. Elastic moduli of nanointerphases were experimentally determined in range from 25.32 ± 3.4 to 66.3 ± 3.2 GPa. Additionally, it is clearly shown that the interphase modulus strongly depends on interphase surface area and interphase volume. Different NBC distribution patterns from fully to partially embedded nanoparticles are proven to yield a remarkable reduction in elastic moduli of nanointerphases.
Three different types of nanoparticles, 1D Cloisite 30B clay nanoplatelets, 2D halloysite nanotubes (HNTs), and 3D nanobamboo charcoals (NBCs) were employed to investigate the impact of nanoparticle shapes and structures on the material performance of polyvinyl alcohol (PVA) bionanocomposite films in terms of their mechanical and thermal properties, morphological structures, and nanomechanical behaviour. The overall results revealed the superior reinforcement efficiency of NBCs to Cloisite 30B clays and HNTs, owing to their typical porous structures to actively interact with PVA matrices in the combined formation of strong mechanical and hydrogen bondings. Three-dimensional NBCs also achieved better nanoparticle dispersibility when compared with 1D Cloisite 30B clays and 2D HNTs along with higher thermal stability, which was attributed to their larger interfacial regions when characterised for the nanomechanical behaviour of corresponding bionanocomposite films. Our study offers an insightful guidance to the appropriate selection of nanoparticles as effective reinforcements and the further sophisticated design of bionanocomposite materials.
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