•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.
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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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•Cellulose nanocrystals (CNC) were successfully extracted from Phormium tenax leaves.•Limonene was used as plasticizer for poly(lactic acid) (PLA) based formulations.•PLA_Limonene_CNC ...bio-nanocomposites were produced by a twin-screw microextruder.•The addition of limonene positively affects the mechanical properties of PLA.•The presence of plasticizer and CNC alters the degradation of PLA bio-nanocomposites.
Poly(lactic acid) (PLA) bio-nanocomposite films modified with limonene as plasticizer and reinforced with cellulose nanocrystals (CNC) extracted from agro-waste, such as Phormium tenax leaves, have been prepared by using a twin-screw microextruder and characterized.
The extraction of cellulose was carried out by chemical treatment followed by sulphuric acid hydrolysis process. Binary and ternary films containing the plasticizer (20wt.%) and/or the CNC (1 and 3wt.%) were produced and characterized in terms of morphological, thermal, mechanical and wettability properties. The effect of CNC content and the combination with the specific plasticizer on the structural properties of PLA films were also investigated.
The addition of limonene into the PLA matrix reduces, as expected, the glass transition temperature of the films, and affects the mechanical properties of the films, increasing the plastic response of PLA. Disintegration study was also carried out under simulated composting conditions in a laboratory-scale test at 58°C, 50% of humidity and in aerobic conditions, demonstrating that the presence of both plasticizer and CNC can alter the degradation rate of developed PLA-based formulations. The successful production of PLA biodegradable nanocomposites incorporating cellulosic material from agro-waste suggested the possible application of these new bio-nanocomposites for active food packaging.
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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.
Blends of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) plasticized with a lactic acid oligomer (OLA) added at three different concentrations (15, 20 and 30 wt% by weight), were prepared ...by an optimized extrusion process to improve the processability and mechanical properties of these biopolymers for flexible film manufacturing. Morphological, chemical, thermal, mechanical, barrier and migration properties were investigated and formulations with desired performance in eco-friendly films were selected. The efficiency of OLA as plasticizer for PLA_PHB blends was demonstrated by the significant decrease of their glass transition temperatures and a considerable improvement of their ductile properties. The measured improvements in the barrier properties are related to the higher crystallinity of the plasticized PLA_PHB blends, while the overall migration test underlined that all the proposed formulations maintained migration levels below admitted levels. The PLA_PHB blend with 30 wt% OLA was selected as the optimum formulation for food packaging, since it offered the best compromise between ductility and oxygen and water vapor barrier properties with practically no migration.
•Sunflower stalks were proposed as source for the extraction of cellulosic materials.•Cellulose nanofibrils (CNF) were successfully extracted by steam explosion.•Cellulose nanocrystals (CNC) were ...extracted by a hydrolysis procedure.•Novel gluten bionanocomposite films were prepared by solvent casting.•The study suggested the possibility of re-valorizing sunflower wastes.
Novel gluten based bionanocomposites reinforced with cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) extracted from sunflower stalks by respectively a steam explosion treatment and a hydrolysis procedure, were prepared by casting/evaporation. The extracted cellulose nanomaterials, both CNC and CNF, were embedded in gluten matrix and their effect was investigated. Morphological investigations highlighted that gluten based bionanocomposites showed a homogenous morphology, the absence of visible cellulose nanoreinforcements, and the presence of holes for Gluten_CNF nanocomposites. Gluten_CNF showed a reduction of water vapour permeability coefficients but the values are higher respect to gluten reinforced with CNC. This behaviour could be related to the ability of CNC to increase the tortuous path of gas molecules. Moreover, the results from thermal, mechanical and barrier properties confirmed the strong interactions obtained between CNC and gluten matrix during the process.
The study suggested the possibility to re-valorise agricultural wastes with potential applications as reinforcement in polymer matrix bionanocomposites.
Poly(vinyl alcohol-co-ethylene) (EVOH) films containing two different active ingredients (AIs), gallic acid (GA) and umbelliferone (UMB) at 5 wt % and 15 wt %, were successfully produced by solvent ...casting and extrusion. The effects of process techniques, AIs presence, typology and content on optical, morphological, thermal and mechanical properties of EVOH based films have been investigated. In addition, moisture content, migration and radical scavenging activity, antimicrobial and antifungal studies were performed, with the aim of evaluating the effect of AIs on structural and functional properties of realized food packaging systems. Results from colorimetric and transparency investigation underlined that the presence of AIs in EVOH copolymer induced important alterations, whereas migration to food simulant data restricted the use of produced films to the contact with fatty foods. On the other hand, the use of AIs clearly induced positive antioxidant response, inhibitions of bacterial and antifungal growth, confirming the possibility of practically using these materials in the food packaging sector.
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•EVOH based films were produced by solvent casting and extrusion.•Gallic acid and umbelliferone were combined with EVOH to get active food packaging.•Homogeneous distribution of active ingredients in EVOH was observed and transparent films were obtained.•Gallic acid and umbelliferone in EVOH based formulations induced antioxidant, antimicrobial and antifungal effects.
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