•Cellulose nanocrystals (CNC) were extracted from natural Phormium tenax and Flax.•CNC were also extracted from commercial microcrystalline cellulose for comparison.•Natural fibres offered high ...levels of extraction efficiency.•Homogeneous distribution of CNC in PVA is observed and transparent films are obtained.•CNC promotes the crystallization of the PVA matrix improving its plastic response.
PVA bio-nanocomposites reinforced with cellulose nanocrystals (CNC) extracted from commercial microcrystalline cellulose (MCC) and from two types of natural fibres, Phormium tenax and Flax of the Belinka variety, were produced by solvent casting in water. Morphological, thermal, mechanical and transparency properties were studied while the respective efficiency of the extraction process of CNC from the three sources was evaluated. The effect of CNC types and content on PVA properties and water absorption capacity were also evaluated. Natural fibres offered higher levels of extraction efficiency when compared with MCC hydrolysis yield. Thermal analysis proved that CNC promotes the crystallization of the PVA matrix, while improving its plastic response. It was also clarified that all PVA/CNC systems remain transparent due to CNC dispersion at the nanoscale, while being all saturated after the first 18–24h of water absorption.
•PVA/Ch hydrogels with 1 and 3wt% of LNPs were prepared by freezing-thawing.•LNPs at 1wt% was beneficial in terms of thermal and mechanical performances.•LNPs promoted the crosslinking and limited ...the deswelling of PVA into the water.•LNPs was efficient in terms of antioxidative response, in synergism with chitosan.•Chitosan and LNPs were effective against E.coli and S.aureus bacteria strain.
Polyvinyl alcohol/chitosan (PVA/Ch) hydrogels containing 1 and 3wt% of lignin nanoparticles (LNPs) were prepared through a freezing-thaw procedure. Results from microstructural, thermal and mechanical characterization of LNPs based PVA/Ch demonstrated that the lowest amount of LNPs (1wt%) was beneficial, whereas the presence of agglomerates at higher LNP content limited the effect. Moreover, a different swelling behaviour was observed for hydrogels containing LNPs with respect of PVA/Ch, due to the formation of a porous honeycomb-like structure. A synergic effect of Ch and LNPs was revealed in terms of antioxidative response by DPPH (1,1-Diphenyl-2-picryl-hydrazyl) activity of migrated substances, whereas results from antimicrobial tests confirmed LNPs as effective against Gram negative bacteria (E. coli) when compared to Gram positive (S.aureus and S. epidermidis) strains. The obtained results suggested the possible use of produced PVA/Ch hydrogels incorporating LNPs in many different sectors, such as drug delivery, food packaging, wound dressing.
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•PLA based films with 1 and 3wt.% of lignin nanoparticles (LNPs) were prepared.•LNPs induced a different nucleation effect in extruded (E) and cast (C) samples.•Decrease in mechanical ...performance was observed for 3wt.% of LNPs cast films.•Incorporation of 1wt.% of hydrophobic LNPs hindered the disintegration of PLA.
Polylactic (acid) bionanocomposites filled with 0, 1 and 3wt.% of lignin nanoparticles (LNPs) were produced by means of two processing techniques, melt extrusion (E-PLA) and solvent casting (C-PLA). The samples were thermally and mechanically characterized by using thermal analyses (TGA and DSC) and tensile tests. Nucleation effect was proved to be remarkably enhanced when homogeneous dispersion of LNPs in PLA matrix was achieved at 1wt.%, in melt extruded samples, while further increase of the loading of LNPs up to 3wt.% did not favor the crystallization behavior. Elongation at break in the case of extruded bionanocomposites was positively affected by the presence of LNPs; nonetheless, in the case of solvent cast films, a decreased tendency of tensile parameters was observed, attributed to inhomogeneous dispersion of LNPs. Disintegrability in composting conditions has been also tested and visual observation, chemical, thermal and morphological investigations proved that the incorporation of 1wt.% of LNPs hindered the disintegration of PLA matrix, due to the hydrophobic nature of the filler. When the nanoparticles content rises up to 3wt.%, aggregation and rougher film surface structure induced higher degradation rate.
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•Ternary poly(lactic acid) (PLA) based nanocomposites were successfully produced.•Cellulose (CNC) and lignin (LNP) nanostructures were combined in PLA or graft-PLA.•A synergic effect ...of LNP and CNC on UV light blocking capability was detected.•The combination of LNP and CNC was effective in nucleation and crystal growth.•LNP and CNC induced an antibacterial activity against Pst tomato pathogen.
Ternary polymeric films based on poly (lactic acid), obtained dispersing cellulose nanocrystals (CNC) and lignin nanoparticles (LNP) at two different amounts (1 and 3wt%), respectively in neat PLA and glycidyl methacrylate (GMA) grafted PLA (g-PLA), were produced by melt extrusion. Thermal, optical and mechanical properties, as well as the morphologies of CNC and LNP reinforced PLA nanocomposites, were investigated. Results from UV–Vis characterization have confirmed a synergic effect of LNP and CNC based nanostructures in terms of transparency and UV light blocking capability. In addition, the combination of the two lignocellulosic nanofillers proved to be effective also in nucleation and crystal growth, with increased cristallinity values for ternary systems in comparison with binary nanocomposites. Furthermore, the ternary nanocomposites showed both higher strength and modulus values than those of neat PLA and PLA binary systems. Lignin nanoparticles and cellulose nanocrystals, when combined with neat or grafted poly (lactic acid), have shown antibacterial activity with reduction in multiplication of the bacterial plant pathogen Pseudomonas syringae pv. tomato (Pst). In particular, results from PLA nanocomposite films containing lignin nanoparticles pointed out how this green functionality allows to develop innovative strategies, towards harmful pathogens, helpful in the food packaging sector.
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•Cellulose nanocrystals (CNC) were isolated from Posidonia oceanica waste.•The surface of nanocrystals was also modified using a commercial surfactant (s-CNC).•Poly(lactic acid) (PLA) ...nanocomposites reinforced with CNC and s-CNC were developed.•The surfactant favours the CNC dispersion in the polymer supporting their effect on PLA properties.•PLA/cellulose systems can be used as new bio-nanocomposites in industrial applications.
Poly(lactic acid) (PLA) nanocomposite films, reinforced with cellulose nanocrystals (CNC) extracted from Posidonia oceanica plant waste, were produced by solvent casting and their morphological, mechanical, thermal, optical and migration properties were studied. Cellulose nanocrystals were successfully extracted through an optimized chemical treatment, followed by sulphuric acid hydrolysis. The nanocrystals were added to the neat polymer at two different weight percentages (1 and 3%wt) using a commercial surfactant to increase the dispersion of CNC in the biodegradable matrix. All the nanocomposites kept the optical transparency of the PLA matrix, while morphological investigations underlined the rougher fracture surfaces of the CNC based systems and a more porous structure of the PLA matrix, induced by the addition of surfactant modified s-CNC. The surfactant favours the cellulose nanocrystal dispersion in the polymer matrix, remarkably enhancing the nucleation effect for matrix crystallization and producing its plasticization. The migration levels for all the studied nanocomposites were well below the legislative limits required for their use as food packaging materials. The successful production of biodegradable nanocomposites incorporating cellulosic sources from biomass waste suggests the possibility of using these new bio-nanocomposites in industrial applications.
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•Cellulose nanocrystals (CNC) were successfully extracted from Diss stems.•Chemical and enzymatic pretreated celluloses from Diss were acid hydrolyzed.•CNC from enzymatic treated ...fibres (E-CNC) exhibited enhanced thermal stability.•CNC from chemically treated fibres (C-CNC) have reduced size compared to E-CNC.
The aim of this research activity was based on the revalorization of Amplodesmos mauritanicus (Diss), an African grass largely presented in the Algerian territory. Diss stems were selected as native botanic material for the extraction of cellulose nanocrystals (CNC). Two different pretreatment steps were carried out to extract CNC from Amplodesmos mauritanicus stems and the following acidic hydrolysis procedure allowed to extract/obtain cellulose nanocrystals in aqueous suspension. The effect of the two different pretreatments, based essentially on chemical or enzymatic treatments, were deeply investigated and the properties compared. Field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were considered for the characterization of raw material, chemical or enzymatic treated Diss stems and CNC extracted from both chemical and enzymatic pretreated cellulose.
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•Advances on lignocellulosic as reinforcements in nanocomposites are highlighted.•The extraction of nanoscaled cellulose and lignin from natural sources is reported.•Notable examples ...of nanocellulose and/or nanolignin based systems are reviewed.•Solvent and melt based processes were considered to develop nanocomposites.•The synergic effect of nanocellulose and nanolignin inside a polymer is emphasized.
Lignocellulosic nanostructures, mainly cellulose and lignin based materials, have recently attracted much attention due to their renewable nature, wide variety of source materials available throughout the world, low cost and density, high surface functionality and reactivity. The exceptional mechanical strength, together with high aspect ratio and large surface area, enable these nanomaterials to reinforce a wide variety of polymers even at very low filler loadings. Furthermore, nanocomposite approach has emerged in the last two decades as an efficient strategy to upgrade the structural and functional properties of natural and/or synthetic polymers. The combination of bioresorbable and sustainable polymers with bio-based nanostructures opened new perspectives in the self-assembly of nanomaterials for different applications with tuneable mechanical, thermal and degradative properties. In the present paper, the effect of introduction of lignocellulosic reinforcement phases (cellulosic and lignin based nanostructures), on structural and functional properties of several thermoplastic polymer matrices was investigated at the nanoscale level. Both solvent casting and melt compounding were considered as processing techniques for the proposed nanocomposite formulations. The role of cellulose and lignin based nanostructures, such as their synergic action when embedded in a polymer matrix, were analysed (taking into account the required functionality of the systems in the appropriate final applications) and reported in terms of morphological, optical, thermal, chemical, mechanical, barrier and degradative performance.
•Cellulose nanocrystals (CNC) were successfully isolated from barley straw and husk.•Chemical and sustainable enzymatic pre-treatments were evaluated for CNC extraction.•The enzymatic pre-treatment ...resulted more effective for CNC extraction.•CNC were successfully used as fillers in PVA_chitosan based nanocomposite films.•Chitosan and CNC modulated the optical, mechanical and antibacterial responses of PVA.
Poly(vinyl alcohol) (PVA) blended with natural chitosan (CH) was selected as matrix for the production, by solvent casting in water, of nanocomposite films containing cellulose nanocrystals (CNC) extracted from barley residues, that were introduced in PVA_CH systems as reinforcement phases. Cellulose nanocrystals were successfully extracted from both barley straw and husk by applying two different approaches, a chemical alkaline and an enzymatic pre-treatment, followed by acidic hydrolysis. The results evidenced the major effectiveness of the enzymatic pre-treatment on the quality of obtained CNC; nevertheless, all the different typologies of nanocrystals were added to the polymers and the morphological, optical, mechanical response, thermal and migration characteristics were investigated, whereas antimicrobial assay were carried out to evaluate the bactericidal effect induced by chitosan presence. The results indicated that chitosan reduced the optical transparency and the mechanical response of PVA matrix, whereas its combination with CNC (especially when extracted by enzymatic treatment and added at a higher content) was able to modulate the optical properties, the mechanical and thermal responses. Moreover, inhibitions on fungal and bacterial development were detected for PVA_CH_CNC ternary systems, suggesting their protective function against microorganisms contamination.
► For the first time, hybrid laminates with three different fibres were produced. ► Concerns are confirmed on the brittleness of hybrid laminates with basalt fibre core. ► An optimal configuration ...(FHB) for flexural properties was singled out. ► Differences between tensile and flexural properties of hybrids were identified. ► In general, the specific mechanical properties of the hybrids are quite high.
This work concerns the production by vacuum infusion and the comparison of the properties of different hybrid composite laminates, based on basalt fibre composites as the inner core, and using also glass, flax and hemp fibre laminates to produce symmetrical configurations, all of them with a 21–23% fibre volume, in an epoxy resin. The laminates have been subjected to tensile, three-point flexural and interlaminar shear strength tests and their fracture surfaces have been characterised by scanning electron microscopy. The mechanical performance of all the hybrid laminates appears superior to pure hemp and flax fibre reinforced laminates and inferior to basalt fibre laminates. Among the hybrids, the best properties are offered by those obtained by adding glass and flax to basalt fibre reinforced laminates. Scanning electron microscopy (SEM) observation of hybrid laminates showed the diffuse presence of fibre pull-out in hemp and flax fibre reinforced layers and a general trend of brittle failure.
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