Fig 2 - uploaded by Motaung Tshwafo
Content may be subject to copyright.
Source publication
Bleached hardwood and softwood South African kraft pulps were passed through a commercially available micro grinder for varying number of passes and the properties of the resultant pulps were assessed periodically using microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray crystallography (XRD) and Thermogravimetric analysis (TGA). The...
Similar publications
A novel composite material was prepared from prawn shell derived chitosan (CHT) and locally available kaolinite-rich modified Bijoypur clay (MC) using a facile technique in which dilute acetic acid was used as a solvent for dissolving chitosan and composite fabrication whereas distilled water was used for preparing the clay dispersion. Bijoypur cla...
The study investigated the bulk fuel, microstructure, morphological, mineral, and functional group characteristics of maize cobs (MC) along with carbonization through thermogravimetric analysis (TGA) for potential energy recovery. To the best of the authors' knowledge, this is the first study on the micro-scale analysis of the fuel properties and b...
Abstract
This study aims to explore the potential of the NaOH-treated Cytostachys renda fibre to be reinforced in the polymeric composites. The NaOH concentrations were prepared as 1, 3, and 5 wt% for soaking time of 1 and 2 h. The treated fibres were characterized in terms of density, chemical composition, Fourier Transform Infrared Spectroscopy (...
The conventional enameling process used in the fabrication of magnet wires requires
harmful processes and products. The target of the industry in the actual context of electrification
is to increase the electrical machines’ efficiency. Indeed, the electrical insulation systems (EIS) of
an electrical machine undergo various environmental constraints...
The parallel flow drop solvothermal method was utilized to synthesize the crystal of MOF-5 by taking the molar ratio of the metal ions to the organic ligands of 2:1 at 140∘C, and the reaction time at 12 hours. Meanwhile, the structure and properties of MOF-5 were characterized by the X-ray diffraction (XRD), scanning electron microscope (SEM), ther...
Citations
... The ATR-FTIR spectrum of microcrystalline cellulose is demonstrated in Fig. 5. The band assignment is presented as reported in the literature 61,63,[65][66][67] . The band centered at 3332 cm −1 corresponding to stretching of OH groups of cellulose and the one at 2893 cm −1 is corresponding to CH stretching vibrations. ...
A 3-unit cellulose model molecule was built and optimized using DFT B3LYP/6-31G(d,p). The electronic properties of the optimized structure of cellulose were investigated in terms of total dipole moment (TDM), HOMO–LUMO band gap (ΔE), and molecular electrostatic potential (MESP). Cellulose demonstrated a TDM of 9.106 Debye and ΔE of 7.647 eV. The hydrogen atom of the hydroxyl group of the CH2OH group of each cellulose unit was replaced by an alkali metal atom (X) such that the 3-unit cellulose once had 1X atom, then 2X, then 3X atoms, where X = Li, Na or K, both without and with 2, 4 and 6 water molecules (W), respectively, to study also the effect of hydration. Without hydration, the values of TDM decreased for all of the proposed interaction, but increased with hydration, while ΔE decreased in all interactions, confirming that interaction cellulose-alkali metal interaction, especially with hydration, resulted in more reactive structures. Mapping of HOMO–LUMO and MESP indicated significant change in the electron density distribution around cellulose under the effect of interaction with the alkali metals, both with and without hydration. The plots of projected density of states also clearly demonstrated the contribution of each alkali metal as well as water in the molecular orbitals, reflecting their effect on the electronic properties of cellulose and cellulose-alkali metals composites. The theoretical calculations were experimentally verified using FTIR and FT-Raman spectroscopy.
... Fig. 4A and B show XRD diffractograms for untreated Matake bamboo and all solid residues after organosolv delignification. Distinct peaks were observed at 2θ = 18 • corresponds to amorphous scattering and 22 • corresponds to the lattice plane of native cellulose I polymorph, which indicates the substantial presence of crystalline fraction (Lekka et al., 2016;Naduparambath et al., 2018). Even though the crystalline structure has not been altered among samples, the intensity of the diffraction peaks varied from one another. ...
... On the other hand, a percentage of fines is removed during the delignification process due to fibers washing. Consequently, the crystallinity index did not show significant differences (with 95% confidence) up to 10 h of reaction, with a value similar to those reported in earlier studies (Lekha et al. 2016;Wentzel et al. 2019). Moreover, the crystallinity index increases at 10 h due to oxidative reactions in the amorphous zone of the cellulose ( Figure S3, Supplementary material). ...
Cellulose, hemicellulose, and lignin are the main constituents of lignocellulose nanofibrils (LCNFs). The content and modification of lignin in the pulps affect the production process and characteristics of LCNFs, showing changes in their morphology, surface, rheological, and dielectric behaviors. Due to controversy and relevance in applications, these changes still need to be explained. This work seeks to understand the effect of lignin content and its oxidation on the production process and the characteristics of LCNFs. It was possible to produce pulps with fibers of similar physical characteristics and carbohydrate content after delignification, allowing the identification of the isolated effects of in situ lignin. A lower amount of lignin facilitated the LCNF production process, generating fibrils with smaller widths (up to ~ 48%) but more considerable apparent lengths (up to ~ 73%). In addition, the viscosity of the suspensions increased for LCNFs with lower lignin content (up to ~ 3.5 times to 0.5% (w/v)), due to increased flexibility, specific surface area, and surface charge of the fibrils. Finally, the LCNFs showed four dipolar relaxations, where the glass transition temperature of lignin decreased with oxidation and increased with increasing condensed structures and decreasing S/G ratio.
... Moreover, they possess unique valuable characteristics, such as high specific strength, moduli and specific surface area, as summarized in Table 2. CNMs can be extracted from different natural sources (wood, non-woody and animal materials), by mechanical treatment and acid hydrolysis or combination of the two. They can broadly be grouped into five categories, viz., cellulose nanofibers (CNF), cellulose nanocrystals (CNCs), bacterial cellulose (BC), algal cellulose (AC), and tunicate cellulose depending on the source and extraction method, as discussed below [3,7,[18][19][20][21][22][23]. Cellulose nanofibers (CNF): Cellulose nanofibers, also known as either microfibrillated cellulose (MFC) or cellulose microfibrils (CMF), are mostly obtained by mechanical treatment from cellulose-based materials and are recognized by web-like structure that consists of crystalline and amorphous domains [7,34]. ...
The present work focused on the research, design, and study of innovative chain extender systems of renewable origin for PLA–based biocomposites, reinforced with wheat bran as filler. The majority of employed chain extender compounds belongs to fossil world, affecting the biodegradability property which characterizes biopolymers. The aim of this work was thus to find promising biobased and sustainable alternatives to provide the same enhancements. According to this objective, epoxidized soybean oil (ESO) was chosen as principal component of the chain extender systems, together with a dicarboxylic acid, malic acid (MA), or succinic acid (SA). The reactivity of the modifier systems was previously studied through thermogravimetric analysis (TGA) and IR spectroscopy, to hypothesize the reaction mechanism in bran–filled blends. Hence, small–scale extrusion was carried out to investigate the effects of ESO/MA and ESO/SA on formulations of different composition (both pure PLA blends and composites). The variation of melt fluidity parameters was analyzed to define the optimized concentration of modifier systems. A comparison between the effects on blends of designed biobased systems and the action of fossil–based Joncryl was performed, to understand if the developed green solutions could represent competitive and efficient substitutes. The modified composites were characterized in terms of mechanical tests, degradation and thermal studies (TGA and DSC), and morphological analysis (SEM), to figure out their main features and to understand their potential in possible industrial applications.
... On the other hand, when digestion of amorphous cellulosic domains of a raw material is performed via acid hydrolysis, the resulting product is the so-called cellulose nanocrystals (CNC) (Peng et al., 2013;Abdul Khalil et al., 2014). NFC, which consists of alternating crystalline and amorphous domains with long, flexible and entangled nanofibres that have lateral diameters in the range of 10-100 nm and lengths in the micrometre scale (Debiagi et al., 2020;Yemenicioglu et al., 2020), is of interest due to its unique properties, including high specific surface area, high aspect ratio, high strength and stiffness, low density and biodegradability (Lekha et al., 2016;Yan et al., 2018a). Such unique properties have proved beneficial when NFC is applied to the manufacturing of packagings, nanocomposites as well as pharmaceutical, medical, cosmetic and food products (Abdul Khalil et al., 2016;Iglesias et al., 2020). ...
... while those of the autoclaved NFCs (ANFC6-ANFC12) were 37.95-46.52%. The crystallinity index significantly decreased upon microfluidisation in the range of 6-12 passes; crystallinity indices of NFCs prepared at 8 and 10 passes are not listed in Table 2. Significant reduction in the crystallinity at increasing number of passes can be ascribed to the fact that microfluidisation randomly broke apart both the crystalline and amorphous regions; the breakage of the crystalline region is indeed believed to play a part in the defibrillation of nanofibres and cellulose bundles (Lekha et al., 2016). ...
Although chemical‐free production processes of nanofibrillated cellulose (NFC) have been investigated, comparative studies on the effect of chemical and chemical‐free processes to produce NFCs are limited. Combined effect of either of these production routes and defibrillation condition has also never been studied. Here, thermally treated NFCs were produced through microfluidisation for 6–12 passes (ANFC6‐ANFC12), while TEMPO‐oxidised NFC (TONFC) was prepared at six passes. Proportion of nanocellulose, viscosity, Gʹ and Gʺ values increased with increased microfluidisation pass in the cases of ANFCs. ANFC12 exhibited gel‐like behaviour with strongest three‐dimensional network structure and required lowest concentration to enhance thin liquid foods into honey‐like consistency. TONFC needed to be added by as much as 8.5, 1.3 and 2.3 times the amount of ANFC12 to achieve the same consistency in thickened water, milk and soup, respectively. ANFC12 can also be well used as Pickering emulsifier due to its higher viscosity and gel‐like property.
... Its uses were soon expanded to a myriad of products, including different tools and tool-handles, shelters and houses, bridges and pathways, boats and vessels, bows and arrows, shoes, and thousands of other essential utensils and applications. From an architectural point of view, wood, engineered wood, and wood-based products have been used to construct houses and buildings, bridges, tree-houses, roof-gardens, exterior and interior wood paneling, and even designing landscapes (Arce and Moya, 2015;Bal, 2016;Andrade et al., 2016;Lekha et al., 2016). ...
Wood is a natural renewable material with unique properties helping mankind to build and develop its communities since the genesis of human on the Earth. Moreover, wood/cellulosic composites provide the opportunity to utilize low-density wood species and agricultural materials that are basically not suitable for structural applications; they also provide homogeneous structures that are of great value for different applications. Never, over the history of civilization, was it possible to exclude wood and wood products from human life. In the recent century or so, iron and concrete ‘tried’ to replace wood, presenting higher strength and less susceptibility to environmental weathering and biological deteriorating agents. Nevertheless, modern structures and buildings erected by iron and concrete lack the warm atmosphere which is the unique characteristic of wood. Although wood is considered irreplaceable, it has some disadvantages narrowing its applications and limiting its service life. These disadvantages mainly include its susceptibility to water and water vapor, biological deteriorating fungi, insects, termites, and marine borers. Various nano-materials have been developed to successfully overcome these shortcomings in the past two decades. The present chapter tries to summarize some main areas in which nanotechnology is being used to improve wood and cellulosic composites. Moreover, some new applications and capabilities of this precious natural material are also brought into perspective, emerging from the utilization of nanotechnology, areas such as transparent wood, self-cleaning coatings, and smart windows. Though some areas have been thoroughly studied, much potential still exists for further studies and commercialization.
... On the other hand, when digestion of amorphous cellulosic domains of a raw material is performed via acid hydrolysis, the resulting product is the so-called cellulose nanocrystals (CNC) (Peng et al., 2013;Abdul Khalil et al., 2014). NFC, which consists of alternating crystalline and amorphous domains with long, flexible and entangled nanofibres that have lateral diameters in the range of 10-100 nm and lengths in the micrometre scale (Debiagi et al., 2020;Yemenicioglu et al., 2020), is of interest due to its unique properties, including high specific surface area, high aspect ratio, high strength and stiffness, low density and biodegradability (Lekha et al., 2016;Yan et al., 2018a). Such unique properties have proved beneficial when NFC is applied to the manufacturing of packagings, nanocomposites as well as pharmaceutical, medical, cosmetic and food products (Abdul Khalil et al., 2016;Iglesias et al., 2020). ...
... while those of the autoclaved NFCs (ANFC6-ANFC12) were 37.95-46.52%. The crystallinity index significantly decreased upon microfluidisation in the range of 6-12 passes; crystallinity indices of NFCs prepared at 8 and 10 passes are not listed in Table 2. Significant reduction in the crystallinity at increasing number of passes can be ascribed to the fact that microfluidisation randomly broke apart both the crystalline and amorphous regions; the breakage of the crystalline region is indeed believed to play a part in the defibrillation of nanofibres and cellulose bundles (Lekha et al., 2016). ...
Dysphagia or swallowing difficulty is a common morbidity experienced by those who have suffered a stroke or those undergone such treatments as head and neck surgeries. Dysphagic patients require special foods that are easier to swallow. Various technologies, including high‐pressure processing, high‐hydrodynamic pressure processing, pulsed electric field treatment, plasma processing, ultrasound‐assisted processing, and irradiation have been applied to modify food texture to make it more suitable for such patients. This review surveys the applications of these technologies for food texture modification of products made of meat, rice, starch, and carbohydrates, as well as fruits and vegetables. The review also attempts to categorize, via the use of such key characteristics as hardness and viscosity, texture‐modified foods into various dysphagia diet levels. Current and future trends of dysphagia food production, including the use of three‐dimensional food printing to reduce the design and fabrication time, to enhance the sensory characteristics, as well as to create visually attractive foods, are also mentioned.
... Cellulose nanofibers can be obtained from diverse sources as wood pulps [11], sisal [12], banana leafs [13], waste newspaper [14], wheat straw [15] through mechanical fibrillation. However, significantly high cost demand required by mechanical fibrillation process is the major challenge for their application at industrial level [11,16,17]. ...
... Cellulose nanofibers can be obtained from diverse sources as wood pulps [11], sisal [12], banana leafs [13], waste newspaper [14], wheat straw [15] through mechanical fibrillation. However, significantly high cost demand required by mechanical fibrillation process is the major challenge for their application at industrial level [11,16,17]. Only a few studies focus on reduction of cost and energy consumption on CNFs production. ...
Lignin-containing cellulose nanofibers (L-CNFs) with various lignin contents were produced by a grinding process from switchgrass, which were pretreated using organosolv fractionation. The effect of different fractionation conditions (temperature and time) and different number of grinder passes on the energy consumption and morphologies of L-CNFs were investigated. Results showed that nanosized fibers were found in organosolv-fractionated samples before grinding. After several grinding passes, L-CNFs with a similar degree of fibrillation as commercial cellulose nanofibers (CNF) were obtained from the fractionated materials. It is beneficial to save energy consumption in the grinding process. The dimensions and dispersion of L-CNFs were significantly influenced by the lignin content in the L-CNFs. Longer and well-separated nanofibrils were observed from transmission electron microscopy and fluorescence microscopy with appropriate residual lignin (~ 13.7 ± 1.59%) in the L-CNFs compared to those of L-CNFs with either lower or higher lignin contents. Therefore, microsized and nanosized lignin particles were successfully obtained in a single process, and they not only facilitated L-CNFs dispersion but also help to decrease the energy consumption during the grinding process.
... The variations in thermal degradation behavior depending on the number of processing steps during fibrillation have been noticed: in general, a decrease in thermal stability can be attributed to the degradation of the cellulose under friction. However, a non-monotonous decrease in thermal stability may be attributed to the reorientation of the chemical components and/or a high possibility of lignin and hemicellulose degradation that favored catalytic behavior [57]. The thermal stability of nanofibrils with a high amount of residual lignin is significantly higher than that for CNF with low lignin contents, and the maximum rate of degradation occurring at 390 C is among the highest reported value [58]. ...
Native polysaccharide nanocrystals have gained increasing interest as fibrous reinforcement in nanocomposites. Unique mechanical properties combined with biodegradability and renewability have placed them as alternative for designing environmentally friendly materials. The source origin and processing have a large impact on the nanofiber dimensions and properties. Most of the studies have been devoted to cellulose and chitin nanocrystals which are organized into fiber bundles in nature. Cellulose nanofibers can be obtained from animal, bacterial, algal, and plant sources. Chitin fibrils constitute, for example, fungal cell walls and arthropod exoskeletons. Based on processing, one defines two major families of polysaccharide nanofibers (whiskers and nanofibrils of polysaccharide). The preparation of the elementary whisker monocrystals has been achieved by acid hydrolysis, which allows collecting them after cleavage of the amorphous domains of the original substrates. Alternatively, the nanofibrillated material constitutes the other family, which results from the peeling of native microfibrils into a network of nanofibrils. The microfibril delamination is often performed with mechanical devices. Chitosan is the deacetylated derivative of chitin. Nevertheless, the preparation of chitosan crystalline nanofibrils that preserve the native directional packing is challenging. The preparation of chitosan nanofibril networks was recently reported by means of a chitosan mild hydrolysis at the solid state. This chapter reviews the methodologies used to produce crystalline nanofibers of polysaccharide with preserved native structural packing. Nanofibers of polysaccharides cellulose, chitin, and chitosan will be the focus of this review. The methods used to characterize these nanofibers will be revised, and the nanofiber properties will be discussed.
... For example, kraft pulp fibers were treated more than 120 times using an ultrafine grinder to obtain CNF. 42 Chun et al. produced CNF passing cellulose fibers 12 times through a microfluidizer. 12 Previous studies which pursued full dispersion of cellulose fibers to nanofibrils 8,43,44 required high degrees of charge density, 600−1500 μmol/g, whereas for 350 μmol/g, the extent of chemical modification enabled to produce CNF by passing the fibers through a microfluidizer just once. ...
Carboxylated cellulose nanofibers, prepared by TEMPO-mediated oxidation (TOCN), were processed into asymmetric mesoporous membranes using a facile paper-making approach and investigated as lithium ion battery separators. Membranes made of TOCN with sodium carboxylate groups (TOCN-COO–Na+) showed capacity fading after a few cycles of charging and discharging. On the other hand, its protonated counterpart (TOCN-COOH) showed highly improved electrochemical and cycling stability, displaying 94.5% of discharge capacity maintained after 100 cycles at 1 C rate of charging and discharging. The asymmetric surface porosity of the membranes must be considered when assembling a battery cell as it influences the rate capabilities of the battery. The wood-based TOCN-membranes have a good potential as an eco-friendly alternative to conventional fossil fuel-derived separators without adverse side effects.
