Search

Poly (lactic acid) PLA based biodegradable polymers and their bio composites are found to be promising as an alternative to the non-biodegradable plastics that are harmful for the environment and humans. These biodegradable and biocompatible polymers have great prospect in applications especially food packaging and bio medical. In bio medical, these have been used in drug delivery, tissue engineering, gene delivery, bone regeneration, and antibacterial biomaterials. This is due to their mechanical, physiological, and chemical properties in addition to their improved functionality, processibility, and sensitivity toward stimuli. The current review sought to highlight the main findings of research on improvements in properties of PLA and its bio composites by blending it with other polymers, adding biomaterials and the applicability of such biopolymers in food packaging and biomedical applications. Further, the advantages and disadvantages followed by challenges in PLA based bio composites and their possible solutions have also been discussed. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) are a green resource which can produce photonic crystal films with structural colors in evaporation-induced self-assembly; CNC photonic crystal films present unique structural colors that cannot be matched by other colored materials. Recently, the mechanisms of CNC photonic crystal films with a unique liquid crystal structure were investigated to obtain homogenous, stable, and even flexible films at a large scale. To clarify the mechanism of colorful CNC photonic crystal films, we briefly summarize the recent advances from the correlations among the preparation methods, microstructures, and color properties. We first discuss the preparation process of CNCs, aiming to realize the green application of resources. Then, the behavior of CNCs in the formation of liquid crystal phases is studied, considering the influence of the CNCs' size and shape, surface properties, and the types and concentrations of solvents. Finally, the film formation process of CNCs and the control of structural colors during the film formation are summarized, as well as the mechanisms of CNC photonic crystal films with full color. In summary, considering the above factors, obtaining reliable commercial CNC photonic crystal films requires a comprehensive consideration of the subsequent preparation processes starting from the preparation of CNCs. [ABSTRACT FROM AUTHOR]

The exploration of nanocellulose has been aided by rapid nanotechnology and material science breakthroughs, resulting in their emergence as desired biomaterials. Nanocellulose has been thoroughly studied in various disciplines, including renewable energy, electronics, environment, food production, biomedicine, healthcare, and so on. Cellulose nanocrystal (CNC) is a part of the organic crystallization of macromolecular compounds found in bacteria's capsular polysaccharides and plant fibers. Owing to numerous reactive chemical groups on its surface, physical adsorption, surface grating, and chemical vapor deposition can all be used to increase its performance, which is the key reason for its wide range of applications. Cellulose nanocrystals (CNCs) have much potential as suitable matrices and advanced materials, and they have been utilized so far, both in terms of modifying and inventing uses for them. This work reviews CNC's synthesis, properties and various industrial applications. This review has also discussed the widespread applications of CNC as sensor, acoustic insulator, and fire retardant material. [ABSTRACT FROM AUTHOR]

Primary material supply is the heart of engineering and sciences. The depletion of natural resources and an increase in the human population by a billion in 13 to 15 years pose a critical concern regarding the sustainability of these materials; therefore, functionalizing renewable materials, such as nanocellulose, by possibly exploiting their properties for various practical applications, has been undertaken worldwide. Nanocellulose has emerged as a dominant green natural material with attractive and tailorable physicochemical properties, is renewable and sustainable, and shows biocompatibility and tunable surface properties. Nanocellulose is derived from cellulose, the most abundant polymer in nature with the remarkable properties of nanomaterials. This article provides a comprehensive overview of the methods used for nanocellulose preparation, structure–property and structure–property correlations, and the application of nanocellulose and its nanocomposite materials. This article differentiates the classification of nanocellulose, provides a brief account of the production methods that have been developed for isolating nanocellulose, highlights a range of unique properties of nanocellulose that have been extracted from different kinds of experiments and studies, and elaborates on nanocellulose potential applications in various areas. The present review is anticipated to provide the readers with the progress and knowledge related to nanocellulose. Pushing the boundaries of nanocellulose further into cutting-edge applications will be of particular interest in the future, especially as cost-effective commercial sources of nanocellulose continue to emerge. [ABSTRACT FROM AUTHOR]

Nanocelluloses (NCs) are appealing nanomaterials that have experienced rapid development in recent years, with great potential in the biomedical field. This trend aligns with the increasing demand for sustainable materials, which will contribute both to an improvement in wellbeing and an extension of human life, and with the demand to keep up with advances in medical technology. In recent years, due to the diversity of their physical and biological properties and the possibility of tuning them according to the desired goal, these nanomaterials represent a point of maximum interest in the medical field. Applications such as tissue engineering, drug delivery, wound dressing, medical implants or those in cardiovascular health are some of the applications in which NCs have been successfully used. This review presents insight into the latest medical applications of NCs, in the forms of cellulose nanocrystals (CNCs), cellulose nanofibers (CNFs) and bacterial nanocellulose (BNC), with an emphasis on the domains that have recently experienced remarkable growth, namely wound dressing, tissue engineering and drug delivery. In order to highlight only the most recent achievements, the presented information is focused on studies from the last 3 years. Approaches to the preparation of NCs are discussed either by top-down (chemical or mechanical degradation) or by bottom-up (biosynthesis) techniques, along with their morphological characterization and unique properties, such as mechanical and biological properties. Finally, the main challenges, limitations and future research directions of NCs are identified in a sustained effort to identify their effective use in biomedical fields. [ABSTRACT FROM AUTHOR]

In 2020, we published a review on the study of semi-crystalline thermoplastic polyurethane elastomers and composites based on the shape memory effect. The shape recovery ability of such polymers is determined by their sensitivity to temperature, moisture, and magnetic or electric fields, which in turn are dependent on the chemical properties and composition of the matrix and the nanofiller. Nanocellulose is a type of nanomaterial with high strength, high specific surface area and high surface energy. Additionally, it is nontoxic, biocompatible, environmentally friendly, and can be extracted from biomass resources. Thanks to these properties, nanocellulose can be used to enhance the mechanical properties of polymer matrices with shape memory effect and as a switching element of shape memory. This review discusses the methods for producing and properties of nanocellulose-based thermo-, moisture-, and pH-sensitive polyurethane composites. The synergistic effect of nanocellulose and carbon nanofillers and possible applications of nanocellulose-based thermoplastic polyurethane biocomposites with shape memory effect are discussed. A brief description of nanocellulose terminology is also given, along with the structure of shape memory thermoplastic polyurethanes. There is significant interest in such materials for three primary reasons: the possibility of creating a new generation of biomaterials, improving the environmental friendliness of existing materials, and exploiting the natural renewability of cellulose sources. [ABSTRACT FROM AUTHOR]

Using cotton pulp fibers as raw material, through composite enzymolysis and purification, two different forms of high-purity cellulose nanocrystals were obtained, namely spherical CNCs (SCNCs) and rod-like CNCs (RCNCs). Vacuum filtration was used to obtain pure SCNCs film and pure RCNCs film. The films were characterized by scanning electron microscopy, ultraviolet-visible spectrometry, and X-ray diffraction and tested for their mechanical properties. The films were shown to have good light transmittance and softness, and the structures were unchanged compared with the cellulose raw materials. This article mainly introduces the preparation process of high-purity cellulose nanocrystals films and provides data support for subsequent research. [ABSTRACT FROM AUTHOR]

This article describes the comparative study of the structure, mechanical and thermomechanical properties of cellulose nanopapers with different thicknesses. Cellulose nanopapers were fabricated by vacuum-filtering cellulose nanofiber (CNF) suspensions. The surfaces of the nanopapers consisted of long and entangled CNFs (10-30 nm in width) and their aggregates, while cross-sections exhibited parallel aligned lamellar structures. The nanopaper thickness can be tailored by controlling the amounts of CNF suspensions used for filtration. Owing to the packing density of CNFs, nanopapers with different thicknesses had similar densities of ~1.50 g cm. The thin nanopapers were transparent and flexible. With increasing thickness, the Young's modulus of the nanopapers slightly decreased, while the ultimate strain and work of fracture increased. The thicker nanopapers displayed higher storage and loss modulus. The nanopapers still kept advantageous mechanical properties even at high temperatures around 260 °C because of the high thermal stability of CNFs and their strong entangled web-like structures. [ABSTRACT FROM AUTHOR]

Highlights: Preparation strategies of cellulose nanopaper were elaborated. Functionalization of cellulose nanopaper and its advanced applications were summarized. Prospects and challenges of cellulose nanopaper were discussed.Cellulose nanopaper has shown great potential in diverse fields including optoelectronic devices, food packaging, biomedical application, and so forth, owing to their various advantages such as good flexibility, tunable light transmittance, high thermal stability, low thermal expansion coefficient, and superior mechanical properties. Herein, recent progress on the fabrication and applications of cellulose nanopaper is summarized and discussed based on the analyses of the latest studies. We begin with a brief introduction of the three types of nanocellulose: cellulose nanocrystals, cellulose nanofibrils and bacterial cellulose, recapitulating their differences in preparation and properties. Then, the main preparation methods of cellulose nanopaper including filtration method and casting method as well as the newly developed technology are systematically elaborated and compared. Furthermore, the advanced applications of cellulose nanopaper including energy storage, electronic devices, water treatment, and high-performance packaging materials were highlighted. Finally, the prospects and ongoing challenges of cellulose nanopaper were summarized. [ABSTRACT FROM AUTHOR]

Nanocellulose is the most abundant material extracted from plants, animals, and bacteria. Nanocellulose is a cellulosic material with nano-scale dimensions and exists in the form of cellulose nanocrystals (CNC), bacterial nanocellulose (BNC), and nano-fibrillated cellulose (NFC). Owing to its high surface area, non-toxic nature, good mechanical properties, low thermal expansion, and high biodegradability, it is obtaining high attraction in the fields of electronics, paper making, packaging, and filtration, as well as the biomedical industry. To obtain the full potential of nanocellulose, it is chemically modified to alter the surface, resulting in improved properties. This review covers the nanocellulose background, their extraction methods, and possible chemical treatments that can enhance the properties of nanocellulose and its composites, as well as their applications in various fields. [ABSTRACT FROM AUTHOR]

Nanocellulose has emerged in recent years as one of the most notable green materials available due to its numerous appealing factors, including its non-toxic nature, biodegradability, high aspect ratio, superior mechanical capabilities, remarkable optical properties, anisotropic shape, high mechanical strength, excellent biocompatibility and tailorable surface chemistry. It is proving to be a promising material in a range of applications pertinent to the material engineering to biomedical applications. In this review, recent advances in the preparation, modification, and emerging application of nanocellulose, especially cellulose nanocrystals (CNCs), are described and discussed based on the analysis of the latest investigations. This review presents an overview of general concepts in nanocellulose-based nanocomposites for sustainable applications. Beginning with a brief introduction of cellulose, nanocellulose sources, structural characteristics and the extraction process for those new to the area, we go on to more in-depth content. Following that, the research on techniques used to modify the surface properties of nanocellulose by functionalizing surface hydroxyl groups to impart desirable hydrophilic–hydrophobic balance, as well as their characteristics and functionalization strategies, were explained. The usage of nanocellulose in nanocomposites in versatile fields, as well as novel and foreseen markets of nanocellulose products, are also discussed. Finally, the difficulties, challenges and prospects of materials based on nanocellulose are then discussed in the last section for readers searching for future high-end eco-friendly functional materials. [ABSTRACT FROM AUTHOR]

Cellulose nanopaper (CNP) is a new potential candidate for flexible biopolymer substrate made of nanocellulose (NC). We systematically studied the effect of NC production from oil palm empty fruit bunch using the different types of acid hydrolysis based on sulphuric acid (NCs) as well as phosphoric acid (NCp) at varied temperatures regarding their morphology and crystallinity on the final properties of CNP. Both CNP from NCs (CNPs) and NCp (CNPp) exhibited higher optical transparency than conventional micropaper. In terms of mechanical properties, CNPs possessed an exceptional improvement of up to 200% compared to micropaper. CNPp specifically produced higher mechanical properties compared to CNPs. The stronger tensile strength of CNPp was attributed to a higher aspect ratio and thus a more flexible one compared to NCs. The greater transparency of CNPs than CNPp was postulated due to the formation of the densely packed order of intra-inter hydrogen bonds found in CNPs, which allowed more light to transmit through the film and reduce the light to scatter. In addition, the higher crystallinity with a smaller aspect ratio could also promote the higher transparency of CNPs to give the combination of influencing factors in explaining the level of transparency of CNP. [ABSTRACT FROM AUTHOR]

Cellulose is one of the most abundant renewable biopolymer in nature and is present as major constituent in both plant cell walls as well as synthesized by some microorganisms as extracellular products. In both the systems, cellulose self-assembles into a hierarchical ordered architecture to form micro to nano-fibrillated structures, on basis of which it is classified into various forms. Nanocellulose (NCs) exist as rod-shaped highly crystalline cellulose nanocrystals to high aspect ratio cellulose nanofibers, micro-fibrillated cellulose and bacterial cellulose (BC), depending upon the origin, structural and morphological properties. Moreover, NCs have been processed into diversified products ranging from composite films, coatings, hydrogels, aerogels, xerogels, organogels, rheological modifiers, optically active birefringent colored films using traditional-to-advanced manufacturing techniques. With such versatility in structure-property, NCs have profound application in areas of healthcare, packaging, cosmetics, energy, food, electronics, bioremediation, and biomedicine with promising commercial potential. Herein this review, we highlight the recent advancements in synthesis, fabrication, processing of NCs, with strategic chemical modification routes to tailor its properties for targeted biomedical applications. We also study the basic mechanism and models for biosynthesis of cellulose in both plant and microbial systems and understand the structural insights of NC polymorphism. The kinetics study for both enzymatic/chemical modifications of NCs and microbial growth behavior of BC under various reactor configurations are studied. The challenges associated with the commercial aspects as well as industrial scale production of pristine and functionalized NCs to meet the growing demands of market are discussed and prospective strategies to mitigate them are described. Finally, post chemical modification evaluation of biological and inherent properties of NC are important to determine their efficacy for development of various products and technologies directed for biomedical applications. [ABSTRACT FROM AUTHOR]

In this work, A new composite material composed of cellulose nanocrystals (CNCs) and waterborne polyurethane (WPU) was prepared. The thermal stability and mechanical properties of composites were studied. Compared with composites with CNCs without acylation treatment, the composites with modified CNCs by acylation reagents exhibited better thermal stability and mechanical properties. In addition, CNCs modified by butyric anhydride in composites demonstrated excellent mechanical properties. When 1.00% of CNCs modified by butyric anhydride were added to WPU, the fracture stress of the resulting composite material reached 52.15 MPa, which was 1262% higher than that of WPU (3.81 MPa), and 157% higher than that of the composite 1% CNCs without acylation treatment (20.31 MPa). This preparation of CNCs-WPU composites with better performance on thermal and mechanical properties provides guidelines for further improving the application of WPU. [ABSTRACT FROM AUTHOR]

The reinforcement potential of novel nanocellulose-based scaffolding reinforcements composed of microfibrils 5 to 50 nm in diameter and several microns in length was investigated. The cellulose nanofibril reinforcement was used to produce a three-dimensional scaffolding. A hybrid two-step approach using vacuum pressure and hot pressing was used to integrate the nanocellulose reinforcements in a liquid molding process with an epoxy resin to manufacture composites containing fiber volume contents ranging from 0.6% to 7.5%. The mechanical properties were studied using three-point bending. The Shore-D hardness test and differential scanning calorimetry (DSC) were used to investigate the curing response and its relation to the mechanical properties. Dynamic mechanical analysis (DMA) with a three-point bend setup was used to investigate the viscoelastic behavior of the nanocellulose composite samples at various temperatures and dynamic loadings. The results using the proposed liquid resin manufacturing method for processing the nanocellulose composites showed an increased modulus and a lower strain-to-failure compared to neat resin. Dynamic testing showed a trend of lower tan delta peaks and a reduction in the glass transition temperature with the addition of nanocellulose reinforcement. [ABSTRACT FROM AUTHOR]

The development of nanocellulose-clay materials resulted of great relevance, as it opened up the applications of nanocellulose, but it still requires new approaches that could contribute to improve the preparation procedures and the features of this type of biohybrid materials. In this context, nanocellulose-sepiolite (NC-S) biocomposite foams and films have already been successfully tested for some applications. However, the influence of the nanocellulose properties on sepiolite-cellulose interactions, and consequently on the final properties and potential applications of NC-S biohybrid materials, has not been previously studied. To address this knowledge gap, four kinds of nanocelluloses produced from elm biomass (non-chemically pretreated lignocellulose and bleached cellulose nanofibers (LCNFs and CNFs, respectively), TEMPO-oxidized cellulose nanofibers (TOCNFs) and cellulose nanocrystals (CNCs)) were characterized and used to develop NC-S nanopapers. A stronger interaction was found between sepiolite and negatively charged nanocelluloses (TOCNFs and CNCs), improving their thermal stability and mechanical properties by increasing the sepiolite content. Furthermore, the type of nanocellulose and the sepiolite content could be adjusted to tune the flammability, water permeability and mechanical and optical properties of the NC-S nanopapers. [ABSTRACT FROM AUTHOR]

This review paper provides a recent overview of current international research that is being conducted into the functional properties of cellulose as a nanomaterial. A particular emphasis is placed on fundamental and applied research that is being undertaken to generate applications, which are now becoming a real prospect given the developments in the field over the last 20 years. A short introduction covers the context of the work, and definitions of the different forms of cellulose nanomaterials (CNMs) that are most widely studied. We also address the terminology used for CNMs, suggesting a standard way to classify these materials. The reviews are separated out into theme areas, namely healthcare, water purification, biocomposites, and energy. Each section contains a short review of the field within the theme and summarizes recent work being undertaken by the groups represented. Topics that are covered include cellulose nanocrystals for directed growth of tissues, bacterial cellulose in healthcare, nanocellulose for drug delivery, nanocellulose for water purification, nanocellulose for thermoplastic composites, nanocellulose for structurally colored materials, transparent wood biocomposites, supercapacitors and batteries. [ABSTRACT FROM AUTHOR]

Incorporation of nanoparticles into polymer blend to obtain finely dispersed morphology has been considered as an effective strategy to prepare nanocomposites. Owing to the renewable and degradable characters, cellulose nanocrystals (CNCs) have been proposed to tailor the phase morphology of poly(L-lactic acid) (PLLA) blend for producing high-performance fused deposition modeling (FDM) consumables. However, the main challenge associated with the ternary systems is the dispersion of the highly hydrophilic CNCs in non-polar PLLA blend by industrial melt blending without involving solution. Herein, with poly(vinyl acetate) (PVAc) modified CNCs powder (a mixture of PVAc grafted from CNCs and PVAc homopolymer latex), the selective dispersion of CNCs in PLLA has been achieved by simple melt processing of PLLA/TPU (polyether polyurethane)/CNCs blend. This results in the ultra-fine TPU droplets at nanoscale in PLLA and improves the melt processibility of composites in FDM due to the decreased viscosity ratio of the dispersed/matrix and the enhanced melt elasticity of PLLA. Combined with the intensive shear and continuous stretch effect during FDM, aligned TPU nanofibers (TNFs) were in situ formed along the elongational flow direction during deposition, which in turn contributed to the improvement of PLLA/TPU/CNCs with 5 wt% filler loading in tensile ductility by 418%, inter-layer adhesion strength and notched impact toughness by 261% and 210%, respectively, as well as achieved good dimensional accuracy and very fine surface quality. [ABSTRACT FROM AUTHOR]

The growing demand for products with lower environmental impact and the extensive applicability of cellulose nanofibrils (CNFs) have received attention due to their attractive properties. In this study, bio-based films/nanopapers were produced with CNFs from banana tree pseudostem (BTPT) wastes and Eucalyptus kraft cellulose (EKC) and were evaluated by their properties, such as mechanical strength, biodegradability, and light transmittance. The CNFs were produced by mechanical fibrillation (after 20 and 40 passages) from suspensions of BTPT (alkaline pre-treated) and EKC. Films/nanopapers were produced by casting from both suspensions with concentrations of 2% (based in dry mass of CNF). The BTPT films/nanopapers showed greater mechanical properties, with Young's modulus and tensile strength around 2.42 GPa and 51 MPa (after 40 passages), respectively. On the other hand, the EKC samples showed lower disintegration in water after 24 h and biodegradability. The increase in the number of fibrillation cycles produced more transparent films/nanopapers and caused a significant reduction of water absorption for both raw materials. The permeability was similar for the films/nanopapers from BTPT and EKC. This study indicated that attractive mechanical properties and biodegradability, besides low cost, could be achieved by bio-based nanomaterials, with potential for being applied as emulsifying agents and special membranes, enabling more efficient utilization of agricultural wastes. [ABSTRACT FROM AUTHOR]

Since last decades, nanocellulose has gained much attention in nanocomposite foams owing to high stiffness and strength, renewability, sustainability and biodegradability. Nanocellulose is hydrophilic, and could be easily dispersed in hydrophilic polymer matrices; however, there are challenges to introduce nanocellulose in less hydrophilic polymers. This review addresses the development of polymer nanocomposite foams with plant-based nanocellulose (cellulose nanofibers and cellulose nanocrystals), and the chemical modification and mechanical approaches to enhance the dispersibility of nanocellulose in hydrophobic polymer matrices. The combination of nanocellulose and other nanoparticles such as graphene nanoplatelets, montmorillonite clay, carbon nanotubes and zeolites to yield multifunctional porous nanocomposite materials with promising features such as self-extinguishment, dye adsorption, microwave absorption, conductivity and biocompatibility is also discussed in this paper. [ABSTRACT FROM AUTHOR]

Nanocellulose is a renewable material with excellent properties. At present, nanocellulose powder is mainly prepared by high-cost spray drying, which severely limits its output and quality. In this paper, we propose an innovative method to prepare dispersible nanocellulose powder by simple precipitation and conventional evaporation. Potassium acetate was added to CNC (a kind of nanocellulose) suspension to precipitate and purify CNC. The added potassium acetate was dissolved in ethanol and removed. Then dispersible nanocellulose powder can be obtained by simple evaporation. In CNC purification, we discussed the combination of different electrolytes and CNCs. It was found that although the monovalent electrolytes lead to weak aggregation with CNC, the resulting dry CNC powder had the best dispersion. In CNC drying, we discussed the effects of different dispersants and different drying methods on the forming of dry CNC powder. It is revealed that ethanol is the best dispersant tested in this paper because it can only form a single hydrogen bond with CNC and is easy to evaporate. In the evaporation of CNC and ethanol mixture, it will not lead to the aggregation of CNC fibers. It is hopeful that the new method may greatly reduce the cost of the preparation of nanocellulose powder. [ABSTRACT FROM AUTHOR]

We report the preparation of highly compressible and elastic piezoelectric aerogels of carboxylated cellulose nanocrystals (CNCs). Aqueous CNC dispersions containing polyethyleneimine and crosslinker were frozen isotropically to yield isotropic aerogels, while oriented aerogels were prepared by directional freezing. These aerogels were highly flexible and porous (~ 85% void fraction), exhibiting greater than 90% recovery at 50% compressive strain even after 100 compression–decompression cycles. Since such aerogels with low bulk modulus and high anisotropy would be an ideal platform for leveraging the piezoelectric properties of CNCs, we used them to prepare piezoelectric nanogenerator devices and determined their energy transduction behavior. Anisotropic aerogels led to an enhanced open-circuit voltage of 840 mV (at ~ 8 N applied force), which is over 2.6 times higher than isotropic aerogels (320 mV). The energy density of anisotropic aerogels was around 52 nW/cm2, representing outstanding piezoelectric performance for cellulose-based aerogels. Such aerogels with high compressibility, elastic recovery and exceptional piezoelectric performance could have potential applications in sensors, wearable electronics, etc. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) have attracted tremendous attention because of their excellent chemical and physical properties and due to their renewability and sustainability. This material can be extracted from agricultural by-products such as rice straw, banana tree, or bagasse. Rice straw was selected as the raw material in this study. Initially, a large amount of lignin must be removed by an alkaline process to obtain a slurry. Thereafter, a green bleaching process can be used to remove the remaining lignin in the slurry. An UV-emitting diode with 365 nm wavelength assisted the oxidation reaction of the H2O2 solution without the use of chlorine-containing chemical bleach. The reaction required only 2.5 h to obtain high-purity cellulose and successfully enhanced the yield. Transmission electron microscopy images showed that the CNCs from rice straw were ~ 100 nm long and 10–15 nm wide. The crystalline index and degradation temperature of CNCs were 83.8% and 257 °C, respectively. [ABSTRACT FROM AUTHOR]

This study reports a new cellulosic material that maintains the original three-dimensional structure of bamboo and is produced by optimization of chemical treatments. Bamboo blocks were prepared from the current year culms of moso bamboo (Phyllostachys edulis) and subjected to three chemical treatments alone or in combination. Based on the color changes and Fourier transform infrared spectra, the combination of alkaline treatment with alcoholysis followed by Wise method was found to be an optimal treatment method. This serial treatment caused the blocks to become completely white and removed non-cellulosic components such as hemicellulose and lignin from the cell walls of the parenchyma as well as those of vascular bundles. This sample was named as "White-Colored Bamboo." Extensive structural evaluations from anatomical- to nano- level were performed using X-ray computed tomography, X-ray diffraction, and transmission electron microscopy incorporated with the 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation technique. These multiple observations showed that the white-colored bamboo maintained its inherent hierarchical structure, thus encouraging to produce functional biomaterials. [ABSTRACT FROM AUTHOR]

Flexible strain sensors have attracted much attention due to their wide applications in human health monitoring, motion detection, human–computer interaction, and smart robots in recent years. Cellulose-based materials include cellulose fibers, cellulose nanofibers, cellulose nanocrystals, and cellulose derivatives such as methylcellulose, carboxymethyl cellulose, and cellulose acetate. They exhibit excellent properties and diverse functions that play key roles in the preparation of flexible strain sensors. The conductive networks of the cellulose-based composite materials are established by mixing or coating conductive materials or directly carbonizing the cellulose materials. This paper was divided into five parts according to the macroscopic forms of sensors, including fibers and yarns, films, papers, fabrics and gels. The materials, preparation methods, and structures of the flexible strain sensors are detailly compared and discussed. The solutions to the difficulties met in the preparation process are proposed. The sensing performance of the flexible strain sensors based on cellulose composite and their applications in physiological signals and human motion detection are summarized. The potential applications and challenges during future development are analyzed. This review provides some suggestions and strategies for further development of flexible strain sensors based on cellulose composite for physiological signals and human motion detection. [ABSTRACT FROM AUTHOR]

Large wounds are characterized by clinical and surgical challenges, requiring numerous searches on demand for inexpensive biocompatible materials that produce the best quality of cutaneous healing. Cellulose is a biopolymer of greatest abundance, good biocompatibility and wide application due to its chemical and physical properties. This study was aimed to develop and characterize low cost membranes of wood cellulose nanofibrils for potential application as a wound dressing in comparison to a commercial porous regenerating membrane. An inexpensive mechanical method was used to defibrillate cellulose, and later the membranes were obtained from the nanofibrils by filtering and drying under mild pressure. The techniques employed for characterization included scanning electron microscopy, physical testing, application in vivo and cost-effectiveness analysis. The membranes presented promising physical properties for application as cutaneous dressing, with characteristic translucency allowing the evaluation of the wound without the need of removal and exchange of the dressing. Wood nanocellulose dressing seems to be promising for wound care since it presented good adhesion to the moist wound surfaces thus promoting the most efficient repitialization in the first 4 days. No allergic reaction or inflammatory response to wood nanocellulose dressings was observed. The wood nanocellulose membranes stand out as a potential wound dressing, as it shows similar efficacy of bacterial cellulose dressing. Besides the efficacy, the membrane developed in this study presents a simpler, faster and cheaper manufacturing process, which may reduce the production cost by 99%. [ABSTRACT FROM AUTHOR]

We investigate the terahertz complex conductivity spectra of cellulose nanocrystal (CNC) based composite films fabricated with different blending ratios of the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and without/with glycerol additive. A partially localized nature of carriers in the composite is clearly seen in the obtained spectral shapes of complex conductivity and is well described by an extended Drude model. We find that the carriers become denser and less localized with increasing PEDOT:PSS blending ratio and that the addition of glycerol to the composite is efficacious in enhancing carrier delocalization as well as mechanical flexibility. [ABSTRACT FROM AUTHOR]

This review covers the use of nanocelluloses in water treatment applications with particular focus on membranes and filters made either entirely from (nano)cellulose or in composite approaches. Nanocelluloses are among the emerging materials of this century, having found an abundance of potential applications in the fields of composites, medicine, functional additives or water treatment. Water treatment applications in particular have received significant academic and commercial attention, with a large variety of approaches developed in order to address arguably one of the largest problems that humanity is confronted with in the 21st century: clean water. In this regard, treatment of both potable water and wastewater is of high importance. The reason for the viability of nanocelluloses as base material relies upon their high specific surface area and abundance of OH groups that already exhibit certain attraction toward pollutants carrying ionic structures or dyes and also can be easily modified to significantly increase the affinity of nanocelluloses toward these pollutants. Nanocelluloses in their various forms (cellulose nanocrystals, cellulose nanofibrils, bacterial cellulose) have been applied in water treatment, with membranes and filters (size exclusion, e.g. for nanoparticle filtration, or affinity membranes) as well as adsorbents (e.g. heavy metal ions, dyes, nitrates) being the most studied. © 2020 The Author. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of bacterial cellulose (one of the most promising cellulose-based nanomaterials) fundamentally depend on its moisture content. It has been found that the effect of aqueous solutions of alkali metal chlorides on its strength and deformation properties is determined by the mobility of water molecules in the near coordination spheres of cation hydration shells. [ABSTRACT FROM AUTHOR]

In this work, a large size of macroporous phenolic resin (PR)/bacterial cellulose (BC) composite with double-network structure was fabricated simply by soaking, heating, solvent exchange, and ambient pressure drying. The mechanism and influence factors for the fabrication of this macroporous composite were systematically elaborated. One network of macroporous composite was composed of PR beads, and the other derived from original BC nanofibers. They supported and reinforced each other, avoiding the collapse of interconnected porous structure and achieving low density (0.29 g/cm3), high porosity (77.7%), low thermal conductivity (0.10 W/m K), and excellent compressive strength (7.97 ± 2.24 MPa). Through further carbonization, carbon counterpart that maintained fine structure and good performance can also be obtained. The surface of macroporous composite was extremely hydrophilic. On the contrary, its carbon counterpart possessed a highly hydrophobic surface (contact angle = 118.2°). These properties suggest that the macroporous composite and carbon counterpart may have potential applications for filtration, separation, and thermal insulation materials. Moreover, this work will provide a novel perspective for the fabrication of porous composites with BC as the template and 3D nanofiber reinforcement simultaneously. [ABSTRACT FROM AUTHOR]

In this work, a series of oil soluble diblock copolymers poly(methyl methacrylate)-b-poly[2-(dimethylamino)ethyl methacrylate] (PMMAm-b-PDEAEMAn; where m is fixed at 49 and n is varied from 3 to 12) are synthesized using a reversible addition-fragmentation chain transfer RAFT method. The copolymers exhibit pH-dependant interfacial activities and behave as macromolecular surfactants under strong acidic conditions. The coassembly behavior and kinetics of cellulose nanocrystals (CNCs) and the copolymer at the water/toluene interface is probed by tracking the dynamic interfacial tension using pendant drop tensiometry. At low pH such as 2 and 3, the film that CNCs coassemble with the copolymer at the oil/water interface can stabilize the pendant drop from dripping down. At a higher pH value, CNCs enhance the interfacial activity of the copolymer through interfacial tension measured and emulsions test. When investigating the coassembly kinetics, it is found that the interfacial protonation reaction of the copolymer and absorbing at the oil/water interface is the rate-determining step and electrostatic binding with CNCs is a much faster process. Besides, the interfacial activity of PMMAm-b-PDEAEMAn is enhanced as n increases and the interfacial coassembly with CNCs is accelerated. A nanoparticle film can be formed because of the coassembly behavior of CNCs and diblock copolymers at the oil/water interface and can stabilize the liquid/liquid interface and endow the interface elastic property. Based on this property, liquid tubule can be generated through injecting CNC aqueous dispersion to copolymer toluene solution. This formation of liquid tubule opens a new platform for the additive manufacturing technique of three-dimensional printing of liquid constructs. [ABSTRACT FROM AUTHOR]

Cellulose is the main structural component of plant cell walls. Cellulose is a fibrous, water-insoluble substance and is considered to be the most abundant bio-derived polymer on earth. From an industrial perspective, plant cellulose has been the mainstay of the wood industries for the past 100 years. The hierarchical organization and semicrystalline nature of cellulose found in plant fibers allows the extraction of nanofibers and nanocrystals using mechanical and chemical top-down de-structuring strategies. Bacterial cellulose has also been increasingly investigated. Bacterial cellulose is composed of cellulose nanofibers secreted extracellularly by some bacteria; bacterial cellulose is therefore obtained using bottom-up synthesis. The unique nanofibrillar structure of bacterial cellulose confers excellent physical and mechanical properties such as high porosity, high elastic modulus and high crystallinity. Research on nanocellulose is accelerating due actual fossil fuel issues such as CO2 emissions, plastic pollution and lack of renewable energy. Nanocellulose materials are non-toxic, biodegradable and recyclable, with no adverse effects on health and the environment. Here, we review cellulose production methods, properties and applications, focusing on the food industry, biomedical materials and electronic devices. We compare vegetal nanocellulose and bacterial cellulose. The increase in the number of publications on nanocellulose is also discussed. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) received great attention in various fields, because of their high efficacy, high aspect ratio, low density, renewability and non-toxicity which make them ideal candidates. Here, various properties and applications especially, thermal, mechanical, adhesives, coatings etc., to introduce CNCs, a hydrophilic and colloidally stable, rigid rod-shaped bio-based nanomaterial with high strength and high surface area. CNCs enhance properties of different compounds under different conditions. The research in the last decade reveals that couple of years CNCs possesses high nature, than any other kind of compound, widely used in industrial and other products, as well as for human benefits. Over the past decade, CNCs is an abundant natural nanomaterial with great potential, has attracted many researches towards its use. Dispersing in polar solvent, they assemble to form multiphase or higher order structures yielding desirable optical and structural properties. The present review summarizes the recent achievements in the development of CNCs templating, highlights considerable progress has been achieved in addressing these multidimensional properties and potential use of CNCs in a wide range of high-tech applications in different fields. [ABSTRACT FROM AUTHOR]

This review describes the recent advances in the production and application of cellulose nanomaterials. Cellulose nanomaterials (CNMs), especially cellulose nanocrystals and cellulose nanofibers, can be produced using different preparation processes resulting in materials with unique structures and physicochemical properties that are exploited in different fields such as, biomedical, sensors, in wastewater treatment, paper and board/packaging industry. These materials possess attractive properties such as large surface area, high tensile strength and stiffness, surface tailor-ability via hydroxyl groups and are renewable. This has been a driving force to produce these materials in industrial scale with several companies producing CNMs at tons-per-day scale. The recent developments in their production rate and their applications in various fields such as medical sector, environmental protection, energy harvesting/storage are comprehensively discussed in this review. We emphasize on the current trends and future remarks based on the production and applications of cellulose nanomaterials. [ABSTRACT FROM AUTHOR]

Nanocellulose materials are derived from cellulose, the most abundant biopolymer on the earth. Nanocellulose have been extensively used in the field of food packaging materials, wastewater treatment, drug delivery, tissue engineering, hydrogels, aerogels, sensors, pharmaceuticals, and electronic sectors due to their unique chemical structure and excellent mechanical properties. On the other hand, metal and metal oxide nanoparticles (NP) such as Ag NP, ZnO NP, CuO NP, and Fe3O4 NP have a variety of functional properties such as UV-barrier, antimicrobial, and magnetic properties. Recently, nanocelluloses materials have been used as a green template for producing metal or metal oxide nanoparticles. As a result, multifunctional nanocellulose/metal or metal oxide hybrid nanomaterials with high antibacterial properties, ultraviolet barrier properties, and mechanical properties were prepared. This review emphasized recent information on the synthesis, properties, and potential applications of multifunctional nanocellulose-based hybrid nanomaterials with metal or metal oxides such as Ag NP, ZnO NP, CuO NP, and Fe3O4 NP. The nanocellulose-based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics. [ABSTRACT FROM AUTHOR]

Determination of nanofibril orientation is crucial for predicting the properties of films and membranes made from cellulose nanofibrils (CNF) because of their inherent anisotropic nature. A novel method is proposed based on image analysis of the polarized light micrographs to quantify and map nanofibril orientation in the film structure. Thin films (average 30 µm in thickness) of CNF were produced using a filtration method and were wet-stretched to two extension levels. Randomly-oriented films were also produced as the control without applying stretch. Samples were imaged at − 45°, 0° and + 45° between crossed polarizers using a polarized light microscope. A BOI was developed based on the interference color changes between the two angles (+ 45° and − 45°). The proposed BOI values range between − 1 and + 1 differentiating orientation in perpendicular directions. The index was shown to work successfully for mapping of the fibril orientation in CNF films. Statistical analysis of the tensile test results confirmed significant difference between tensile modulus of CNF films produced using different stretch ratios. This difference was also supported by the good agreement between the tensile properties of the films, the BOI and directionality results obtained from the surface analysis of scanning electron micrographs. The method was validated by applying to single pulp fibers with known orientation as well as un-stretched and stretched polyvinyl chloride films and oriented cellulose nanocrystals. The advantages of the proposed method over other conventional methods used for orientation analysis are discussed. [ABSTRACT FROM AUTHOR]

In this article, we successfully fabricated the bionanocomposites using cellulose nanocrystals (CNCs) and reduced graphene oxide (rGO) reinforced into biodegradable polylactic acid (PLA) matrix through melt‐mixing method. Due to the affinity difference between hydrophilic CNC and hydrophobic PLA, the surface modification of CNC was employed using quaternary ammonium salts (CTAB) as a surfactant. The nanocomposites were developed using different blend ratios of CNC/modified CNC (1, 2, and 3) wt% and (0.5 wt%) rGO into the polymer matrix. The morphology of CNC, q‐CNC (modified CNC), and nanocomposites were inspected by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). It is demonstrated from tensile tests that, the nanocomposite with 1 wt% CNC and rGO showed maximum tensile strength compared with PLA and its nanocomposites. Moreover, the nanocomposite with 1 wt% CNC and rGO was also having maximum thermal stability. From cytotoxicity evaluation, it is observed that all the nanocomposites are nontoxic and cytocompatible to HEK293 cells. In addition to this, the nanocomposite with q‐CNC showed enhanced barrier properties compared with PLA and PLA/CNC/rGO nanocomposite. The results obtained from different characterizations showed that the incorporation of surfactant onto CNC improved the dispersion in PLA but at the same time deteriorated the PLA matrix. [ABSTRACT FROM AUTHOR]

A novel biocomposite of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)/acetylated cellulose nanocrystals (ACN/PHBH) was prepared by solution-casting after surface modification of cellulose nanocrystals (CNCs). Acetylated cellulose nanocrystals (ACNs) exhibited improved dispersion in PHBH compared with non-acetylated CNCs, and maximum thermal decomposition temperature of ACN/PHBH was 13 °C higher than that of neat PHBH. Compared to the neat PHBH and CNC/PHBH, 57.6% and 24.5% improvements in tensile strength, and 52.4% and 30.6% improvements in Young's modulus were obtained for the bionanocomposites. The water-vapour and the oxygen barrier properties of ACN/PHBH improved by 76.1% and 30.4% compared with CNC/PHBH samples. Simultaneous enhancements on the thermal stability, mechanical and barrier properties were mainly caused by uniform dispersion of ACNs and solid interfacial bonding between filler and matrix. This performance of the bionanocomposite will broaden the utilization of CNCs as renewable bioresources and the practical application of PHBH-based plastics as replacements for traditional petrochemical materials. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) was functionalized applying the Laccase/TEMPO oxidative treatment, leading to a five-fold increase of the concentration of carboxyl groups. Paper produced with this cellulose showed improved mechanical properties while maintaining barrier function against water and greases as compared to paper produced with non-oxidized BC. Also, the negative charge provided by the carboxyl groups on functionalized BC was used to generate silver nanoparticles (AgNPs), obtaining a BC paper and Ag composite. The presence of AgNPs in the composites was validated by SEM, EDS and ICP analysis, showing spherical, uniformly sized particles stabilized in the BC nanofibers matrix. Additionally, antimicrobial property of composites containing AgNPs was tested. The results showed the strong antimicrobial activity of the composites against Gram-positive and Gram-negative bacteria and fungi. The generation of Ag nanoparticles in a matrix that combine the physical characteristics of the BC nanofibers with the stiffness and the mechanical properties of paper produced composites that may have applicability in technological and biomedical uses. [ABSTRACT FROM AUTHOR]

In this work, high transparent bacterial cellulose (HTBC) biocompatible membranes were produced to be used as substrates in organic light-emitting diodes (OLEDs). These multifunctional membranes are based on bacterial cellulose (BC) and an organic–inorganic sol, composed of boehmite (Boe) nanoparticles and epoxi modified siloxane (GTPS). In order to be used as substrates, BC/Boe-GPTS membranes were covered with silicon dioxide (SiO2) and indium tin oxide (ITO) thin films deposited at room temperature using radio frequency (RF) magnetron sputtering. Visible light transmission improves to 88%, instead of 40% previously achieved. The electrical properties for HTBC/SiO2/ITO substrate shows that the ITO deposited films are n-type doped semiconductors with resistivity of 2.7 × 10−4 Ω cm, carrier concentration of − 1.48 × 1021 cm−3, and mobility of 15.2 cm2 V−1 s−1. These values are comparable to those of commercial ITO deposited onto glass substrates. After the characterization of the HTBC film, we used it as a substrate for the fabrication of a small molecule organic light-emitting diode OLED. The maximum efficiencies obtained were 1.95 cd/A and 1.68 cd/A for the reference OLED and the HTBC OLED, respectively. The HTBC OLED efficiency is then around 86% of the standard ITO-based OLED. This is clearly a good improvement, since previous BC-based simple architecture devices without Boe-GPTS have an efficiency 50% smaller than that of the standard OLED. [ABSTRACT FROM AUTHOR]

Bacterial cellulose is a product of the vital activity of some types of bacteria. In contrast to plant cellulose, it is characterized by high purity, strength, and elasticity. Together with nontoxicity and biocompatibility, these properties make bacterial cellulose to be applicable in biotechnology, medicine, and production of composites as a reinforcing component. The nanoscopic sizes of the structural units of bacterial cellulose provide it with a large specific surface area and, as a consequence, a pronounced dependence of many properties of a material on surface interactions with an environment. This review is devoted to discussing the structure and mechanical properties of bacterial cellulose, with especial attention being focused on its behavior in the presence of water and aqueous solutions. "Bacteria make no mistakes..." S. Gandlevskii [ABSTRACT FROM AUTHOR]

The tribological tests were performed on a pin on cylinder tribometer, in order to investigate the application of cellulose nanocrystals (CNC) as additives in water-based lubricants. The coefficient of friction and wear between a stainless steel shaft and chrome steel ball were measured in the presence of CNC lubricant with different concentrations. The effect of the normal force, the rotational speed and the shaft diameter on the coefficient of friction and wear were studied as well. It was found that adding 2 wt% of CNC in water improved lubrication and provided a very low friction coefficient of approximately 0.09. The wear depth and width were reduced by more than 50%. The improvement of the coefficient of friction and wear was mainly due to the high strength and alignment of CNC rods. [ABSTRACT FROM AUTHOR]

This report describes the synthesis of highly carboxylated cellulose nanocrystals (CNCs) from jute fiber by facile oxidation with ammonium persulfate (APS). The oxidation time effects on microstructure, surface chemistry, crystal structure, and thermal properties were investigated. Crystal-like morphology was obtained with 5.2 nm average particle diameter and 300–500 nm length, depending on the oxidation time. The degree of oxidation (DO) was found to be 0.27: the highest among APS-oxidized CNCs. The carboxylic group amount of 1550 mmol kg−1 was achieved for 16 h oxidation treatment, resulting in high surface charge with the absolute zeta potential value of 40 mV. The DO value was well correlated with the peak intensity of carbonyl group ascertained from FT-IR studies: 0.12 + 0.38(I1730/I1060). As-prepared CNCs showed improved dispersibility in organic solvents up to 15 h. The APS oxidized CNCs showed good thermal stability: the onset decomposition temperature was 240 °C. Using X-ray diffraction method the crystalline index was ascertained as more than 67%. Surface modification of APS-oxidized cellulose nanofibers (CNFs) was confirmed using FT-IR and XPS. Modified CNFs were dispersed in organic solvents such as toluene and THF. Jute is a good candidate material for obtaining highly pure and crystalline CNCs through APS oxidation, exhibiting great potential as a functional material for use in diverse fields. [ABSTRACT FROM AUTHOR]

Cellulose Nanocrystals (CNC) have received significant attention due to their high Young's modulus, high strength, biocompatibility, and renewability. These properties make them ideal as a reinforcement phase for polymer composites. However, typical composite processing techniques have limitation in efficiently fabricating composites with different shapes. Inspired by the emerging technology of 3D printing, this work utilized the digital light processing (DLP) 3D printing approach to fabricate CNC reinforced poly (ethylene glycol) diacrylate (PEGDA) glycerol composites. To improve CNC compatibility with PEGDA matrix, 1,3-diglycerolate diacrylate (DiGlyDA) that has a similar chemical structure but also has hydroxyl groups was blended with PEGDA. The dispersibility of CNC was characterized by the Halpin–Tsai model and polarized light microscopy. Mechanical testing results indicated that mechanical properties of DLP 3D printed composites were improved by CNC incorporation. Furthermore, curing layer thickness during DLP 3D printing can also be used to tune the composites' mechanical and water swelling properties. Complex 3D CNC composites structures were also successfully printed by the DLP 3D printing with great fidelity. This versatile approach of controlling composite's properties and structure using CNC and DLP 3D printing can be exploited to further advance the utilization of cellulosic materials toward biomedical and many other applications. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a fluorescent and antibacterial nanocomposite film based on Zinc sulphide (ZnS) quantum dots, cellulose nanocrystals (CNCs) and polyvinyl alcohol (PVA) was successfully synthesized. CNCs were first decorated in situ with ZnS quantum dots, which were then introduced into a PVA matrix to prepare nanocomposite films with good fluorescent and antibacterial properties. The X-ray diffraction and scanning electron microscope analysis indicated that ZnS nanoparticles were well-dispersed and randomly coated on the CNCs with uniform particle size. The visible emission peak in the ZnS/CNCs nanocomposites was 473 nm with an excitation wavelength of 350 nm. The CNCs loaded with ZnS quantum dots exhibited bright blue fluorescence under the ultraviolet light. Additionally, CNCs/ZnS nanocomposite films also had good antibacterial properties (bacterial inhibition rate = 78.25%).Graphical abstract: [ABSTRACT FROM AUTHOR]

Abstract: This study investigated effects of residual lignin on composition, structure and properties of cellulose fibrils and cellulose fibril-based films by comparing two groups of cellulose fibrils which contained different amounts of lignin (15% and 2%, respectively) but were similar in cellulose to hemicellulose ratio. The results showed that lignin affected the size and content of nanofibril in cellulose fibrils through initially delaying but ultimately facilitating the mechanical defibrillation. Due to higher thermal stability and strong UV absorption capability, lignin enhanced the thermal stability and UV blocking properties of cellulose fibril-based film. Hydrophobic lignin also improved the dewatering of cellulose fibrils and the hydrophobicity of cellulose fibril-based film. Lignin interfered with the interfibrillar hydrogen bonding and therefore increased the mesopore diameter of cellulose fibril network. Lignin acting as a cement in cellulose fibril-based film made the film with a more densely packed structure, a higher density and a smoother surface. However, lignin decreased the transparency of cellulose fibril-based film due to its chromophore groups and impaired the mechanical strength of cellulose fibril-based film through interfering with the interfibrillar hydrogen bonding.Graphical abstract: [ABSTRACT FROM AUTHOR]

Abstract: For the successful commercialisation of microfibrillated cellulose (MFC) it is of utmost importance to carefully characterise the constituent cellulose particles. This could for instance lead to the development of MFC grades with size distributions tailored for specific applications. Characterization of MFC is challenging due to the heterogeneous chemical and structural nature of MFC. This study describes a fractionation approach that combines two steps of physical sieving of larger particles and a final centrifugation step to separate out the smallest, colloidally stable particles, resulting in four distinctly different size fractions. The properties, such as size and charge, of each fraction were studied, as well as MFC filtration time, film formation, and film properties (mechanical and optical). It was found that virtually all surface charges, determined by polyelectrolyte adsorption, are located in the colloidally stable fraction of the MFC. In addition, the amount of available surface charges can be used as an estimate of the degree of fibrillation of the MFC. The partly fibrillated particles frequently displayed a branching, fringed morphology. Mechanical testing of films from the different fractions revealed that the removal of large particles may be more important for strength than achieving full fibrillation. Overall, this study demonstrates that by controlling the size distribution in MFC grades, property profiles including dewatering time to make films by filtration, rheology, film strength and optical transmittance could be optimised.Graphical abstract: [ABSTRACT FROM AUTHOR]

Hydroxyazetidinium salts were used to surface-modify cellulose nanocrystals (CNC) by grafting the salts onto the sulphate ester groups on the CNC surfaces. The grafting was confirmed by ζ-potential measurements and by the thermal degradation behaviour of the modified CNC. The thermal stability (onset of degradation) of the CNC was improved by the surface modification (almost 100 °C). Composites containing surface-modified or unmodified CNC (0.1, 1.0 and 10 wt%) with an ethylene-based copolymer as matrix were produced by compression moulding. The thermal stability of the composites was not, however, markedly improved by the surface grafting onto the CNC. It is suggested that this is due to a degrafting mechanism, associated with the alkaline character of the system, taking place at high temperatures. Model experiments indicated, however, that this did not occur at the conditions under which the composites were produced. Furthermore, in the case of a reference based on pH-neutralised polymeric system and modified CNC, an upward shift in the onset of thermal degradation of the composite was observed. The addition of the CNC to the polymer matrix had a strong influence of the mechanical performance. For example, the tensile modulus increased approximately three times for some systems when adding 10 wt% CNC. The surface grafting of the hydroxyazetidinium salts appeared mainly to affect, in a positive sense, the yield behaviour and ductility of the composites. The results of the mechanical testing are discussed in terms of interactions between the grafted units and the matrix material and between the grafted groups. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a novel bionanocomposite of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) and cellulose nanocrystals (CNCs) was prepared by the cast-film method. The influence of the CNC content on the morphology, crystallization, as well as thermal, mechanical, and barrier properties (oxygen and water vapor) of the bionanocomposite was systematically investigated. The results showed that the crystallization behavior of PHBH was changed with the addition of CNCs, resulting in an improvement in the thermal stability and mechanical properties of the bionanocomposite. Compared with PHBH, the water-vapor permeability coefficient of bionanocomposite increased by 207.82% and the oxygen permeability coefficient decreased by 18.46%. Moreover, it was notable that the bionanocomposite possessed the optimal mechanical properties when the CNC content was 2.3 wt%.Graphical abstract: [ABSTRACT FROM AUTHOR]