Cellulose Nanostructures Research Articles

Materials Engineering of Violin Soundboards by Stradivari and Guarneri

AbstractWe investigated the material properties of Cremonese soundboards using a wide range of spectroscopic, microscopic, and chemical techniques. We found similar types of spruce in Cremonese soundboards as in modern instruments, but Cremonese spruces exhibit unnatural elemental compositions and oxidation patterns that suggest artificial manipulation. Combining analytical data and historical information, we may deduce the minerals being added and their potential functions—borax and metal sulfates for fungal suppression, table salt for moisture control, alum for molecular crosslinking, and potash or quicklime for alkaline treatment. The overall purpose may have been wood preservation or acoustic tuning. Hemicellulose fragmentation and altered cellulose nanostructures are observed in heavily treated Stradivari specimens, which show diminished second‐harmonic generation signals. Guarneri's practice of crosslinking wood fibers via aluminum coordination may also affect mechanical and acoustic properties. Our data suggest that old masters undertook materials engineering experiments to produce soundboards with unique properties.

Evaluation of conductivity of nanostructured polyaniline/cellulose nanocrystals (PANI/CNC) obtained via in situ polymerization

Cellulose nanocrystals (CNC) have a wide range of applications due to the high aspect ratio, crystallinity and mechanical properties in addition to being renewable and biodegradable. Polyaniline (PANI) is a conductive polymer that has attracted extensive attention due to low density and high electrical conductivity. However, polyaniline in the bulk form has some limitations in terms of use because of its chemical nature as a consequence of secondary hydrogen bonds that reduces conformability and mechanical strength. Aiming at the applicability of polyaniline as films or gels, this work combines two types of materials: cellulose nanocrystals (CNC) and polyaniline through an in situ polymerization of PANI in CNC suspensions to create a nanostructured material. Thermal stability (TGA), particle size (Zeta-sizer), physical and chemical characteristics (FTIR, UV-vis), the process of polymerization (Voc) as well as conductivity was evaluated according to the different PANI/CNC ratios (R = 0.05, 0.1, 0.2, 0.3 and 0.4). Results show that particle size, thermal stability and time of polymerization increase with CNC concentration, indicating that cellulose nanostructure works as a backbone to PANI deposition. FTIR and UV-vis show the evolution of the main characteristics absorption bands around 1220 cm−1 , 1487 cm−1 and 1594 cm−1 (IR) and 381∼391 nm, respectively while the PANI/CNC ratios increase. Otherwise, conductivity values of the nanostructured PANI/CNC with the higher content of PANI is 8.9 × 10−1 S/cm−1 compared to 3.63 S/cm−1 to neat polyaniline, showing to be a great alternative of nanostructured material.

Isolasi Nanoselulosa Terkarboksilasi dari Limbah Kulit Pisang Ambon Lumut dengan Metode Oksidasi

In this study, banana peel from ambon lumut (Musa acuminata) was used as source for nanocellulose fibers. Carboxylated nanocellulose was isolated with oxidation method using ammonium persulfate (APS). In order to investigate the effect of temperature towards the characteristics of nonocellulose, temperature for oxidation process was set at three different values: 60 °C, 70 °C, dan 80 °C. Nanostructure of cellulose was observed as a mix of fibers and whiskers from transmission electron microscopy (TEM) images. The diameter of nanocellulose is ranging from 12,1 to 25,1 nm. Data from spectrometry graphs (FTIR) confirms the existence of carboxyl functional groups in nanocellulose samples. X-ray diffraction pattern (XRD) shows that crystallinity index values increase as temperature of oxidation process increases. The highest crytallinity index value of 72,4% was obtained from nanocellulose treated with oxidation temperature of 80 °C. This analysis shows banana peel waste as a potential alternative source for carboxylated nanocellulose.

Migration and Degradation in Composting Environment of Active Polylactic Acid Bilayer Nanocomposites Films: Combined Role of Umbelliferone, Lignin and Cellulose Nanostructures.

This study was dedicated to the functional characterization of innovative poly(lactic acid) (PLA)-based bilayer films containing lignocellulosic nanostructures (cellulose nanocrystals (CNCs) or lignin nanoparticles (LNPs)) and umbelliferone (UMB) as active ingredients (AIs), prepared to be used as active food packaging. Materials proved to have active properties associated with the antioxidant action of UMB and LNPs, as the combination of both ingredients in the bilayer formulations produced a positive synergic effect inducing the highest antioxidant capacity. The results of overall migration for the PLA bilayer systems combining CNCs or LNPs and UMB revealed that none of these samples exceeded the overall migration limit required by the current normative for food packaging materials in both non-polar and polar simulants. Finally, all the hydrophobic monolayer and bilayer films were completely disintegrated in composting conditions in less than 18 days of incubation, providing a good insight on the potential use of these materials for application as active and compostable food packaging.

Improved production of bacterial cellulose through investigation of effects of inhibitory compounds from lignocellulosic hydrolysates

AbstractAlthough the unique nanostructure of bacterial cellulose (BC) imparts superior mechanochemical properties and thus allows for diverse applications, the high production cost of BC necessitates the development of more cost‐effective solutions, for example, those using lignocellulosic biomass as a substrate and relying on its pretreatment and saccharification to generate fermentable sugars. However, the various species (e.g., aliphatic acids, furans, and phenolics) produced during pretreatment may interfere with bacterial cell growth and BC production. Herein, we investigated the effects of aliphatic (acetic and formic) acids, furans (5‐hydroxymethylfurfural [5‐HMF] and furfural), and phenolics (syringaldehyde and p‐coumaric acid) on the production of BC. This production was enhanced at low aliphatic acid concentrations (1 g/L acetic acid and 0.5 g/L formic acid) but was suppressed by at least 90% in cases of 0.75 g/L formic acid, 0.4 g/L furfural, 4 g/L 5‐HMF, 2.5 g/L syringaldehyde, and 2.5 g/L p‐coumaric acid. BC production efficiencies of 97.86%, 76.66%, and 73.50% were observed for Miscanthus, barley straw, and pine tree hydrolysates, respectively, under optimal conditions. Therefore, these results provided the possibility to utilize the most abundant and sustainable lignocellulose on the planet for BC production.

A Novel Approach Using Conventional Methodologies to Scale up BNC Production Using Komagataeibacter medellinensis and Rotten Banana Waste as Alternative

Currently, cellulose nanostructures are among the most promising structures, and extensive work in materials and biotechnology industries is aimed at identifying an efficient process of production. Even when production at the laboratory scale is successful, crucial aspects of increased commercial applications for cellulose nanostructures are linked to large-scale production. Large-scale production requires a balance between the cost of the culture medium and product value. Therefore, in this work, for the optimization and scaling up of bacterial nanocellulose, a culture medium consisting of rotten banana unsuitable for human consumption was used for the first time as an inexpensive feedstock. Initially, the bacterial nanocellulose (BNC) culture medium conditions were optimized, and it was established that a glucose concentration of 26.4 g/L and a V/A ratio of 2.2 cm were the optimal conditions for production reaching a BNC yield of 5 g/L, which was 42.4% higher than the best result initially obtained. Finally, the scale-up process was performed, implementing a regime analysis methodology by comparing the characteristic times of the critical mechanisms involved in BNC production, namely, microbial growth, glucose consumption, BNC production, and glucose diffusion into the BNC membrane, as the first approach for this type of BNC production process. The mechanism underlying the BNC production process is glucose diffusion into the BNC membrane (characteristic time, 675.47 h). Thus, the V/A ratio was selected as the scale-up criterion most suitable for producing BNC under static culture conditions, allowing the production of 16 g of BNC after 12 d of fermentation in a plastic bioreactor, which was 3378% higher than that produced in glass vessels. The results obtained in this study may initiate further improvements in BNC commercial production by exploiting different feedstocks.

A new approach for the use of anionic surfactants: nanocellulose modification and development of biodegradable nanocomposites

The stabilization of nanocellulose suspensions and their compatibility with polymer matrices are challenges that have been investigated in the scientific community. However, little work has resulted in significant electrostatic stabilization as well as improved the mechanical behavior of nanocomposites. Anionic surfactant modified nanocellulose, and the results demonstrated the impact of the concentration of this surfactant on nanocellulose surfaces and properties. The variation in electrostatic stability was evaluated by the zeta potential, which is key to the comprehension of dispersion and agglomeration in suspensions. Also, physicochemical tests were conducted to analyze the properties of nanocelluloses. The addition of the surfactant and its effects were verified by physicochemical characterization; it was evaluated the crystallinity, thermal stability, composition, adsorption effect, and other properties. Mechanical, thermal and physicochemical tests were conducted to understand the influence of nanoparticles on nanocomposites. The results of this study demonstrated that the surfactant-modified cellulose nanostructures presented excellent electrostatic and thermal stability, which made the developed materials potential reinforcing agents for the incorporation of polymeric matrices. These modified CNSs were incorporated in a poly(butylene adipate-co-terephthalate), and improvements of its mechanical properties were observed. Also, the thermal stability of the polymer was maintained, and the water diffusion coefficient was reduced, favoring applications that need this characteristic, like plastic packaging.

Chromium removal from contaminated wastewaters using biodegradable membranes containing cellulose nanostructures

The removal of chromium from contaminated water was investigated using biodegradable membranes and functionalized cellulose nanoparticles. We used poly(butylene adipate-co-terephthalate), a flexible polymer, for membrane development via phase inversion technique. CNS, with and without phosphorylation (CNS-P), was used aiming to improve the removal of chromium from contaminated drinking water. The neat CNS showed limited efficiency on the Cr removal. On the other hand, CNS-P indicated removal of 93% and 88% of Cr(VI) and Cr(III), respectively. The Cr removal can be associated with CNS higher surface area and active sites, which allows more regions for immobilization of chromium species. Also, at lower pH the CNS-P presents a surface charge that can interact via electrostatic forces with the chromium species, which increases the removal efficiency. CNS-P also showed greater thermal stability due to phosphorylation. The addition of CNS and CNS-P improved the membranes’ mechanical performance, which improves the applicability of this material, with potential application in domestic houses and water treatment stations. A small device for domestic use was tested to confirm the efficiency of the membranes, and the functionalized membranes showed 71% of chromium removal, which highlights its potential for water decontamination.

Acetylated cellulose nanostructures as reinforcement materials for PBAT nanocomposites

AbstractAcetylated‐cellulose nanostructures (CNS) were used as reinforcing agent to develop poly(butylene adipate‐co‐terephthalate)—PBAT—nanocomposites with 1, 3, 5, and 10 wt% of modified and nonmodified nanoparticles through solvent casting. This study explains the interactions between the reactive groups CNS and PBAT interact and the influence of this interaction in the mechanical and thermal properties of the composites. The nonmodified CNS showed a noncontinuous increase in the PBAT stiffness, due to the low interaction between the reinforcement and the matrix and low CNS dispersion. The best results were obtained to acetylated CNS due to the intermolecular interactions between the acetyl groups and the polymer chains. Probably the acetyl groups interfered in the atomic vibration relative to the functional groups of the matrix, which is indicative of the interaction and enhancement of the internal cohesion of the components.

A New Proposal of Preparation of Different Polymorphs of Nanocellulose from Eucalyptus citriodora

Cellulose is a renewable, sustainable, and high available biopolymer; their common form is the type-I polymorph. However, polymorphic changes are associated with different properties and a wide range of applications. In this study, we proposed a new method to prepare polymorphic cellulose nanostructures (CNSs): first, the CNS were isolated, and then the polymorphs were converted. CNS-I (type-I), CNS-II (type-II), and CNS-III (type-III) were successfully obtained, and the structure, crystallinity, superficial characteristic, morphology, and thermal stability were evaluated. The results showed that CNS-II and CNS-III are more amorphous than CNS-I due to the strong reagents used for the polymorphic conversion, which results in a swelling, increased chain spacing, and structural disorganization. This effectively changed the morphology of the CNS, from cellulose nanocrystals from irregular quasi-spherical nanoparticles. The proposed method allows a wide range of applications, from package and nanocomposites with CNS-I due to its high crystallinity and crystal morphology, to drug carrier, food thickener and biomedical products for CNS-II and CNS-III due to its quasi-spherical shape and more amorphous structure.

Biocompatibility analysis of Borassus flabellifer biomass-derived nanofibrillated cellulose

The increased awareness about environment conservation and sustainable progress has encouraged the use of agricultural byproducts. Here, we investigated Borassus flabellifer leaf stalk residues as a sustainable precursor for nanofibrillated cellulose (NFC) production by sequential process. Alkali pretreatment and bleaching removed hemicellulose and lignin from B. flabellifer leaf stalk. Transmission electron microscopy images revealed the diameter and length of fibrillated cellulose nanostructure as 12−27 nm and 0.5−1 μm, respectively. NFC biocompatibility was analyzed in human mesenchymal stem cells (hMSCs) using cell viability assay, cellular and nuclear morphology analysis, mitochondrial membrane potential (MMP) assessment, and gene expression analysis. NFC showed no significant effect on hMSC viability at high concentration and failed to alter nuclear architecture and MMP. Biocompatibility assessment suggests that NFC is non-toxic and NFC-based films may enhance the adhesion and proliferation of hMSCs, highlighting its potential role as a suitable matrix for stem cell differentiation and biomedical applications.

Cellulose nanocrystals from curaua fibers and poly[ethylene‐co‐(vinyl acetate)] nanocomposites: Effect of drying process of CNCs on thermal and mechanical properties

AbstractPoly[ethylene‐co‐(vinyl acetate)] (EVA) and cellulose nanocrystals (CNCs) from curaua fibers were used to obtain nanocomposites. Due to polarity that acetate groups promote in EVA, they tend to present better affinity with cellulose nanostructures without compatibilizers. In addition, the influence of the drying conditions of CNCs suspension on their dispersion through the matrix was also evaluated. CNCs were obtained via acid hydrolysis in a mixture of sulfuric and hydrochloric acids. Part of CNCs in neutral suspension was freeze‐dried and part was dried in an oven with air circulation. The dried CNCs were incorporated into EVA at concentrations of 1, 3, and 5 wt% of each CNCs. The compositions were processed in a corotating twin‐screw extruder and injection molded. Morphological results showed better dispersion and adhesion of freeze‐dried nanocrystals into EVA, and these nanocomposites also presented increase in elastic modulus and elongation at break, resulting in more resilient and elastic materials.

Surface modification effects on the thermal stability of cellulose nanostructures obtained from lignocellulosic residues

In this work, it was studied the steric and electrostatic stabilization of cellulose nanostructures (CNS) and their effects on the thermal stability of the nanoparticles. Three different agents modified the surface of CNS: a grafted polymer, polyethylene glycol (PEG), a nonionic surfactant, Ultraric, and an anionic surfactant (Surfom). All modifications changed the dimensions of the nanoparticles, and the thermogravimetric results show an improvement in the thermal stability of the CNSs, that is, the thermal decomposition of cellulose increased from 326 to 341–366 °C for Surfom-modified samples, 348–389 °C for Ultraric-modified samples, and to 426–436 °C for PEG-modified samples. The differential scanning calorimetry showed that the Surfom-modified samples have no crystalline structure, different from the other modifiers. The other stabilizers showed a tendency to form a crystalline coating in the CNSs surface since all the results are highly dependent on the structure of the modified. In this way, it is possible to conclude that the addition of different materials to improve the stabilization of CNS and minimize its aggregation tendency has a significant influence on the thermal stability, enhancing the applicability of these nanomaterials. Finally, it is presented how the differences between the thermal behavior of the modified CNS impact the applications, comparing the use of different polymer matrices and its respective processing temperatures.

Cellulose Nanostructure-Based Biodegradable Nanocomposite Foams: A Brief Overview on the Recent Advancements and Perspectives.

The interest in designing new environmentally friendly materials has led to the development of biodegradable foams as a potential substitute to most currently used fossil fuel–derived polymer foams. Despite the possibility of developing biodegradable and environmentally friendly polymer foams, the challenge of foaming biopolymers still persists as they have very low melt strength and viscosity as well as low crystallisation kinetics. Studies have shown that the incorporation of cellulose nanostructure (CN) particles into biopolymers can enhance the foamability of these materials. In addition, the final properties and performance of the foamed products can be improved with the addition of these nanoparticles. They not only aid in foamability but also act as nucleating agents by controlling the morphological properties of the foamed material. Here, we provide a critical and accessible overview of the influence of CN particles on the properties of biodegradable foams; in particular, their rheological, thermal, mechanical, and flammability and thermal insulating properties and biodegradability.

Composite films of ecofriendly lignocellulosic nanostructures in biodegradable polymeric matrix

Cellulose nanostructures (CNS) are an alternative for reinforcement of biodegradable polymers. However, the usual process applied to obtain them is environmentally harmful, generating chemical wastes, mostly in the lignin removal process. In this work, bionanocomposites reinforced with CNS were obtained using a process with lower environmental impact, viz. enzymatic hydrolysis of Pinus wood, with or without alkaline pretreatment for lignin removal. They were then incorporated into poly(butylene adipate-co-terephthalate) (PBAT) at 1%, 3%, and 5% (wt./wt.) by a solvent casting process with a nonionic surfactant as surface modification agent. The properties of the obtained composites indicated that pretreatment for lignin removal was not necessary to improve the mechanical properties. The isolated nature of the CNS led to a better distribution in the casting process and similar mechanical properties, with an increase in the Young’s modulus by 16%. Addition of the surfactant helped improve the dispersion of the reinforcement but did not affect the mechanical properties. The interaction with water was affected by the addition of surfactant, which resulted in a hydrophilic composite and influenced its post-use degradation. The results of this work confirm that it is possible to produce CNS composites without excessive consumption of reagents and that their properties can be modified for use in different packaging applications.

Phoenix dactylifera lignocellulosic biomass as precursor for nanostructure fabrication using integrated process

Agricultural residue is an inevitable byproduct of agricultural activities. Valorization of agricultural residue is necessary to avoid wastage. In this study, we developed an integrated process for fabricating various nanostructures using Phoenix dactylifera (PD) lignocellulosic biomass as a sustainable bioprecursor. The PD biomass was treated using a hydrothermal method at 180 °C to derive the liquid fraction containing carbon nanodots (CDs). After pretreatment, the biomass was treated with an alkali solution to disassociate the lignin and cellulose. The extracted lignin was dissolved in tetrahydrofuran and subjected to a dialysis process. During the dialysis process, the lignin transformed into lignin nanoparticles (LNPs). The cellulose-containing fraction was transformed into cellulose nanostructures (CNs) via a sequential process (bleaching and acid hydrolysis). The structural properties, morphological features, crystallinity, and thermal stability of the fabricated CDs, LNPs, and CNs were analyzed. The synthesized CDs and LNPs had a spherical shape with different sizes: 2–10 nm (CDs) and 100–900 nm (LNPs). The CNs exhibited a fibrillated architecture and were 5–10 nm wide and 400–700 nm long. A biocompatibility analysis indicated that the synthesized nanostructures are nontoxic to human mesenchymal stem cells at concentrations of up to 200 μg/mL. This process is suitable for synthesizing nanostructures using different types of plant lignocellulosic biomass.

Isolation and acetylation of cellulose nanostructures with a homogeneous system

A homogeneous system for nanocellulose acetylation was investigated. Cellulose nanostructures (CNS) were obtained from microcrystalline cellulose, and modification was conducted to increase hydrophobicity and physico-chemical properties of the nanoparticles. Sulfuric acid and hydrochloric acid were used for the isolation. The CNS were characterized with dynamic light scattering, zeta potential, atomic force microscopy, Fourier-transform infrared spectroscopy, nuclear magnetic resonance, X-ray photoelectron spectrometry, degree of substitution (DS), X-ray diffraction (XRD), and thermogravimetric analysis. Nanostructures obtained with sulfuric acid showed lower particle sizes and lower thermal stability. After modification, the results indicated the substitution of OH groups in cellulose structure by acetyl groups. The XRD patter was considerably modified and it was verified that acetylation increased the thermal stability. Different methods were used to calculate the DS, and the differences between the methodologies were explained. The acetylated samples play an important role in the nanocomposites field, since the hydrophobic surface increase its applications.

Design and Characterization of PLA Bilayer Films Containing Lignin and Cellulose Nanostructures in Combination With Umbelliferone as Active Ingredient.

Poly (lactic acid) (PLA) bilayer films, containing cellulose nanocrystals (CNC) or lignin nanoparticles (LNP) and Umbelliferone (UMB) were extruded and successfully layered by thermo-compression starting from monolayer films. Lignocellulosic nanostructures were used in PLA based film as nanofillers at 3 wt.%, while UMB was used as active ingredient (AI) at 15 wt.%. The effects of processing techniques, presence, typology and content of lignocellulosic nanoparticles have been analyzed and thermal, morphological, mechanical and optical characterization of PLA nanocomposites have been made. Furthermore, X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR) studies evaluated the presence of nanofillers and AI at chemical level. Bilayer formulations showed a good interfacial adhesion and improved stress at break with respect of PLA monolayers, although they were less stretchable and transparent. Data obtained from thermal, colorimetric and transparency investigations underlined that the presence of lignocellulosic nanofillers and AI in PLA monolayer and bilayer films induced relevant alterations in terms of overall color properties and thermal stability, while antioxidant activity of umbelliferone was enhanced by the addition of lignin in produced materials.

Thermal stability of the PBAT biofilms with cellulose nanostructures/essential oils for active packaging

The primary objective of this study is to evaluate the thermal stability of the active films with the cellulose nanostructure (CNS, 5 mass%) treated with encapsulated essential oils (EOs), eugenol and linalool. CNS untreated and treated were incorporated in the poly(butylene adipate-co-terephthalate) (PBAT) polymer matrix prepared by casting. In this study, all samples were characterized by FTIR, DRX, TG, DSC and SEM, elucidating the contribution of each component in the final films. CNS untreated and treated with EOs were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA), confirming the interaction between these components. The active biofilms were analyzed by TGA and DSC analyses (differential scanning calorimetry), confirming that their thermal stability was maintained similar to the neat PBAT film, without loss of properties. The CI (crystallinity index, %) of the polymeric films was calculated from heat fusion (ΔH) values, indicating that the incorporation of the nanostructures into the PBAT matrix increases the crystallinity of the biofilms, from 11.5 (neat PBAT) to 13.8% (PBAT/CNS-E), acting as a nucleating agent in the polymeric matrix. The presence of the EOs did not decrease the CNS stability, as well of the biocomposite films. Moreover, the thermal analysis confirmed that the EO was well involved by the CNS, before and after the incorporation in the PBAT polymer, as observed in the SEM images.

Valorization of industrial paper waste by isolating cellulose nanostructures with different pretreatment methods

Industrial paper wastes are an underestimated source of lignocellulosic materials. In this work cellulose nanostructures (CNS) were produced from this residue by acid hydrolysis and two chemical pretreatments consisting of an alkaline (CNS-I) or an acid (CNS-II) treatment. These pretreatments and the obtained CNSs were characterized using compositional analysis, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential, atomic force microscopy (AFM), and X-ray diffraction (XRD). Results reveal a reduction in the non-cellulosic compounds in pre-treated samples, with different levels of components removal and lower lignin values for alkali treatment. TGA reveals that CNSs present lower thermal stability than the residue. The SEM images revealed that pretreatment led to fiber breakage. The XDR diffractions show the co-existence of cellulose I and cellulose II, with different crystallinity index for CNSs. The DLS and AFM revealed that the production of spherical nanoparticles was following the dimensions of ˜195 for CNS-I and ˜350 nm for CNS-II. All the analysis allowed a more comprehensive understanding of the CNS properties and their possible applications. Finally, it is possible to conclude that the conversion of paper wastes into CNS is an excellent opportunity to recovery this residue and aggregate value to them.