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Starch-derived films exhibit significant potential for packaging applications owing to their low cost, biodegradable characteristics, and natural abundance. Nonetheless, there is a demand to enhance their mechanical properties and moisture resistance to broaden their use. In this study, high performing sorbitol-plasticized starch/Ti 3 C 2 T x MXene nanocomposites, reinforced with ultra-low filler contents, were fabricated for the first time in literature. The MXene nanoplatelets were well-dispersed within the starch matrix while there was a tendency for the fillers to align in-plane, as revealed by polarized Raman spectroscopy. The produced nanocomposite films demonstrate remarkable effectiveness in blocking UV light, offering an additional valuable attribute in food packaging. The Young's modulus and tensile strength of starch films containing 0.75 wt% MXene increased from 439.9 and 11.0 MPa to 764.3 and 20.8 MPa, respectively. The introduction of 1 wt% MXene nanoplatelets reduced the water vapour permeability of starch films from 2.78 × 10−7 to 1.80 × 10−7 g/m h Pa due to the creation of highly tortuous paths for water molecules. Micromechanical theories were also implemented to understand further the reinforcing mechanisms in the biobased nanocomposites. The produced starch nanocomposites not only capitalize on the biodegradable and renewable nature of starch but also harness the unique properties of nanomaterials, paving the way for sustainable and high-performance packaging solutions that align with both consumer and environmental demands. [ABSTRACT FROM AUTHOR]

Isotactic polypropylene (i-PP) – montmorillonite (MMT) nanocomposite films were prepared by melt-compounding and hot-pressing. The influence of organoclays on the mechanical properties and drawability of these isotropic composite films was investigated. Ultimate properties of solid-state drawn PP tapes incorporating 2.5 wt% MMT outperformed those of pure PP tapes. Interestingly, these improvements were found not to be the result of a mechanical reinforcement effect of the nanoclay platelets but merely the result of a more efficient ultra-drawing mechanism with MMT acting as a processing additive that altered initial polymer morphology and drawing behaviour. Hence, the introduction of MMT resulted in higher ultimate draw ratios and subsequently higher ultimate mechanical properties of the oriented nanocomposite tapes. [ABSTRACT FROM AUTHOR]

A potential advantage of platelet-like nanofillers as nanocomposite reinforcements is the possibility of achieving twodimensional (2D) stiffening through planar orientation of the platelets. Forced assembly by multilayer coextrusion, which enables the in-plane orientation of platelet-like fillers in alternating layers, was used in this work to produce poly(lactic acid) (PLA)/graphene multilayer films. These films exhibited a multilayer structure made of alternating layers of neat PLA and PLA containing graphite nanoplatelets (GNPs). Electron microscopy revealed information on the orientation of the individual GNPs. X-ray diffraction results indicated that the thickness of the individual GNPs was reduced during the multilayer coextrusion process. A significant reinforcement of 120% at an overall GNP loading of 1 wt % in PLA was achieved. This high effective reinforcement was attributed to the high degree of planar alignment, improved dispersion and exfoliation and increased aspect ratio of the GNPs in the composite layers after multilayer coextrusion. Improved water vapor barrier properties were also achieved as a result of the highly organized 2D nanofillers in the multilayer films. These industrial scalable multilayer nanocomposite films open up possibilities for lightweight and strong packaging materials for food and industrial applications. [ABSTRACT FROM AUTHOR]

Oriented poly(lactic acid) (PLA)/multiwall carbon nanotube (MWNT) tapes are prepared by solid-state drawing. These tapes showed significant morphological, mechanical and electrical property changes after drawing, with polymer crystallinity, nanotube dispersion and alignment being improved. Interestingly, the presence of the MWNTs perturbed the orientation of the crystalline polymer chain domains. Drawing lowered the electrical conductivity and increased the percolation threshold of the nanocomposites, but micromechanical analysis showed that it greatly improved the reinforcing efficiency of the MWNTs. This resulted in an overall good balance with one of the best compromises in terms of high mechanical properties and electrical properties for conductive polymer composite tapes. [ABSTRACT FROM AUTHOR]

ABSTRACT Polylactic acid (PLA)-based nanocomposite films, containing up to 5% by weight of two types of nanoclays: sepiolite needle-like clay and halloysite nanotube clay, were prepared via industrially viable melt processing route. Clays modify the crystallinity of the hosting PLA affecting its gas barrier and mechanical properties. Annealing treatments of composite films were found to be critical in the optimization of these properties with an additional enhancement in crystallinity and stiffness especially in presence of clays. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39798. [ABSTRACT FROM AUTHOR]

Highlights The transcrystalline layer (TCL) constitutes a cylindrical crystal structure enveloping a reinforcing fiber, which plays a pivotal role in influencing the interfacial stress transfer within composite materials. However, its potential impact on interfacial shear strength (IFSS) and tensile properties of self‐reinforced polylactic acid composites (SRPLA) have been largely overlooked. In this study, the growth of TCL with isothermal crystallization time was observed. The development of TCL had an optimum effect on interfacial bonding (IFSS increased by 57.3%) after 10 min of isothermal crystallization due to improved “anchoring” effect caused by the interaction between the amorphous region in both TCL and the matrix. Prolonged isothermal crystallization time reversed this effect due to less chain entanglements as a result of spherulites growth and transcrystalline structure perfection. In terms of tensile properties, the development of the TCL exhibited a detrimental effect on tensile strength and strain at break, ascribed to a transition of tensile failure mode from a fiber‐dominated failure mode to a matrix‐dominated failure mode, yet yielded a positive influence on Young's modulus. This study offers crucial insights and guidance for comprehending the impact of TCL on SRPLA properties, thereby facilitating the potential for optimization of SRPLA properties. In‐situ observation of the TCL growth in SRPLA. Insight into impact of TCL development on IFSS and tensile properties. Essential guidance for SRPLA performance optimization. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) composites reinforced with two types of graphite nanoplatelets varying in lateral size - small (GNP-S) and large (GNP-L) - were produced via melt compounding. Morphological, thermal, mechanical, and electrical properties were investigated to reveal the influence of particle size. Electron microscopy and X-ray diffraction showed well dispersed small GNP-S particles up to 10 wt.% loading, while large GNP-L particles started to agglomerate at loadings ⩾7 wt.%. Addition of GNPs improved the Young’s modulus of the composites by 10% and 24% for small and large nanoplatelets, respectively, the latter being among the highest reported for PLA/GNP systems. For GNP-L this larger increase could be partly explained by an increase in crystallinity while no such effect was observed for GNP-S. Conversely, GNP-L systems showed embrittlement while polymer yield was preserved for GNP-S. GNP-L resulted in a lower electrical percolation threshold. However, systems based on smaller GNP-S particles showed significantly enhanced conductivity and a reduction in percolation threshold after annealing. Heat distortion temperature (HDT) increased by up to 13 °C, with large GNP-L showing the slightly larger increase. [ABSTRACT FROM AUTHOR]

Abstract The network formation of reduced graphene oxide (rGO) within an epoxy resin during curing has been in-situ visualised for the first time, with its effect on electrical, mechanical, and multifunctional properties of these nanocomposites explored. Different initial states of dispersion and filler contents were employed to examine the nanofiller network formation process. Good electrical conductivity (10−3 S/m at 0.05 wt% rGO) together with good mechanical reinforcement (12% increase in flexural modulus at 0.2 wt% rGO) were obtained at relatively low filler loadings. The integrated strain sensing capabilities based on the rGO network were explored with good sensitivity and repeatability. Joule heating was performed as a potential application for de-icing of multifunctional composite components with good heating capability from −20 °C to 20 °C within 2 min. [ABSTRACT FROM AUTHOR]

Abstract: Bacterial cellulose (BC) is a natural hydrogel, which is produced by Acetobacter xylinum (recently renamed Gluconacetobacter xylinum) in culture and constitutes of a three-dimensional network of ribbon-shaped bundles of cellulose microfibrils. Here, a two-step purification process is presented that significantly improves the structural, mechanical, thermal and morphological behaviour of BC sheet processed from these hydrogels produced in static culture. Alkalisation of BC using a single-step treatment of 2.5wt.% NaOH solution produced a twofold increase in Young’s modulus of processed BC sheet over untreated BC sheet. Further enhancements are achieved after a second treatment with 2.5wt.% NaOCl (bleaching). These treatments were carefully designed in order to prevent any polymorphic crystal transformation from cellulose I to cellulose II, which can be detrimental for the mechanical properties. Scanning electron microscopy and thermogravimetric analysis reveals that with increasing chemical treatment, morphological and thermal stability of the processed films are also improved. [Copyright &y& Elsevier]