1 January 2018
, Pages 118-125
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https://doi.org/10.1016/j.carbpol.2017.09.089Get rights and content
Commercialization of cellulose nanofibrils (CNFs) involves addressing various challenges. Among them, wet storage and transport of CNFs due to their irreversible agglomeration when dehydrated (i.e., hornification) is a pressing issue, as it increases transportation costs. Various alternatives have been proposed in literature, some of which require the use of high-energy treatments to facilitate their redispersion after drying, while others may be inadequate when applied to food and pharmaceutical applications. The present work examines a new approach that involves using poly (vinyl alcohol) (PVA) as a capping agent to redisperse CNFs. Different CNF to PVA ratios were used, and redispersed samples were analyzed in terms of their morphological, physicochemical and rheological properties to assess changes occurring during processing. Results show that the ratio of CNFs to PVA affects the final properties of the redispersed product, when the ratio 1:2.5 was used, the redispersed product closely resembles the never dried sample.
Cellulose is one of the most widely abundant natural polymers, with applications in the textiles (Klemm, Heublein, Fink, & Bohn, 2005), painting (Ek, Gellerstedt, & Henriksson, 2009a), food (Soukoulis, Rontogianni, & Tzia, 2010), pulp and paper (Ek, Gellerstedt, & Henriksson, 2009b; Yousefi et al., 2013), construction (Peters, Rushing, Landis, & Cummins, 2010), medical, and pharmaceutical industries (Amin, Abadi, & Katas, 2014). Its success is associated with an annual synthesis of nearly 1.5×1012t (Klemm et al., 2005) and with a broad spectrum of physical and chemical properties. Its broad range of properties can be expanded through the deconstruction of the hierarchical structure of cellulose synthesized by plants to obtain a nano-sized material known as nanocellulose (Moon, Martini, Nairn, Simonsen, & Youngblood, 2011).
Recent advances in nanocellulose use have revealed its promising applications for concrete (Peters et al., 2010), specialty paper (Kumar et al., 2014), drilling fluids (Klemm et al., 2011), electronic devices (Okahisa, Yoshida, Miyaguchi, & Yano, 2009), food packaging (Fernandes et al., 2010, Gómez H. et al., 2016, Siró and Plackett, 2010) and drug delivery (Moon et al., 2011). Its potential for novel applications is exhibited by the over 315 patents developed for cellulose nanofibrils (CNFs) by 2015 (Carpenter, De Lannoy, & Wiesner, 2015). Technological advances in nanocellulose use have been accompanied by its industrial development through pilot plants in Canada, Japan, Sweden and Finland (Meyer, Tapin-Lingua, Da Silva Perez, Arndt, & Kautto, 2012; Rebouillat & Fernand, 2013).
In spite of the advances made towards production and commercialization of CNFs, several challenges must still be addressed to achieve a competitive product. Among these challenges, hornification, the irreversible formation of hydrogen bonds between fibrils during suspension dehydration, hinders its short term commercialization as this process increases transportation costs as suspensions require water content levels as high as 65wt.% (Eyholzer et al., 2009, Missoum et al., 2012) while also allowing for the growth of undesired microorganisms in suspensions.
Economic and technical disadvantages of the wet storage of nanocellulose have promoted the creation of means of obtaining nano-scaled products with less water. Different alternatives to obtain a redispersed powder form of CNFs have been proposed in the literature (Nechyporchuk, Belgacem, & Bras, 2016). Peng, Gardner, and Han (2011), have explored the effects of different dehydration methods on the morphologies of obtained particles by exploring techniques such as oven drying, spray drying, freeze-drying and supercritical fluid use. However, when the obtained particles were redispersed, the original solution could not be reconstituted. Alternative methods have been proposed as well (i.e., the chemical modification of nanocellulose (Eyholzer et al., 2009) and the inclusion of additives that can hinder hydrogen bond formation among CNFs. While Yan et al. (2016) performed a hydrophobization of the cellulosic surface, by the addition of alkyl ketene dimer in an organic solvent. This process hindered the hornification among fibers, while simultaneously improved its incorporation in polymeric matrix nanocomposites, as the contact angle between the pellets of CNFs and water increased to values over 100° (Yan et al., 2016).
Missoum, Bras, and Belgacem (2012) illustrated the effects of the addition of sodium chloride at different pH levels on the redispersion of freeze-dried CNFs. Redispersion was performed by stirring a suspension at 10000rpm and by then performing dialysis to remove the residual chloride. The authors associated the blockage of hydrogen bonding to the electrostatic attraction between Na+ and 2δ− of oxygen atoms present in cellulose and to the attraction between Cl− and the δ+ of H atoms, linked to the aforementioned oxygen atoms; generating a screening effect, preventing the formation of hydrogen bonds (Missoum et al., 2012).
Using a similar approach, Butchosa and Zhou (2014) evaluated the adsorption of carboxymethyl cellulose (CMC) during the drying and redispersion of CNFs. After dehydrating their suspensions, they were submerged in water and stirred at high speeds through a rotor-stator system to achieve redispersion. It was observed that a minimum quantity of CMC is adsorbed by CNFs, thus preventing hornification. Fairman (2014) evaluated different concentrations of cetyltrimethylammonium bromide (CTAB) of 0–10wt.% and found a proportional relationship between the redispersion of CNFs and surfactant content in their suspension.
As is shown above, there have been important advances in the redispersion of CNFs; however, some of these solutions require the use of high quantities of energy to redisperse dehydrated products or using an additive that is inadequate in food and pharmaceutical applications (e.g., CTAB) (Isomaa, 1975). Due to the aforementioned reasons, the present work proposes an alternative approach to redisperse CNFs that involves poly (vinyl-alcohol) (PVA), a material approved by the Food and Drug Administration for its use in humans and in packaging with contact to food (DeMerlis & Schoneker, 2003). In spite of the use of PVA as a stabilizing agent in the redispersion of silver nanoparticles (Khanna et al., 2007); the reviewed literature is devoid of information pertaining the use of PVA to prevent hornification of CNFs. Following dehydration in the presence of PVA, the mixtures were subjected to mild mechanical stirring and evaluated in terms of their morphological, physicochemical and rheological properties to assess changes resulting from drying, redispersion and isolation processes; the analysis was conducted via field emission scanning electronic microscopy (FE-SEM), Attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and colorimetric and rheological measurements.
Ground rachis from banana plants (c.v. Valery) harvested in Antioquia, Colombia was supplied by Banacol S.A. Reagent grade potassium hydroxide and sodium chloride, synthesis quality sodium chlorite, glacial acetic acid, fuming hydrochloric acid and Congo red were manufactured by Merck. Unless otherwise specified water type 3 was used.
Commercial grade poly (vinyl alcohol) (PVA, hydrolysis degree: 98%, Mw: 105kDa) from Kuraray was obtained from a local provider (Andercol S.A.).
As an initial assessment of the performance of PVA in cellulose redispersion, the stability of the redispersed cellulose suspensions was evaluated based on a sedimentation essay. As is shown in Fig. 2, the dehydration and redispersion of cellulose decreased suspension stability levels, with the lowest stability levels evidenced by CNFOD while CNFND remained stable throughout the test period. When PVA was added to the cellulose before its dehydration, an improvement in redispersed cellulose
The use of PVA as a capping agent for CNFs was studied. The nanocellulose to capping agent ratio affected the stability of the redispersions obtained, with a ratio of 1:1.5 found to be the threshold between stable and unstable suspensions.
PVA was successfully removed from the redispersed CNFs by washing them with hot water and by filtering the suspensions as confirmed by FTIR and TGA measurements. The ratio of PVA added affected the behavior of the redispersed material with no significant
The authors acknowledge funding received from the Research Center for Investigation and Development (CIDI) at the Universidad Pontificia Bolivariana, and they thank the Science, Technology and Innovation Administrative Department of the Colombian Government (COLCIENCIAS) for providing financial support through 2013 grant #617. The authors thank M Sc. Marlon Osorio for his valuable input and comments.
- R. Zuluaga et al.
Cellulose microfibrils from banana rachis: effect of alkaline treatments on structural and morphological features
- H. Yousefi et al.
Comparative study of paper and nanopaper properties prepared from bacterial cellulose nanofibers and fibers/ground cellulose nanofibers of canola straw
Industrial Crops and Products
- J. Velásquez-Cock et al.
Influence of combined mechanical treatments on the morphology and structure of cellulose nanofibrils: thermal and mechanical properties of the resulting films
Industrial Crops and Products
- G.H.D. Tonoli et al.
Cellulose micro/nanofibres from Eucalyptus kraft pulp: preparation and propertiesSee AlsoQuaternized agricultural by-products as anion exchange resinsSynthesis, characterization, and antitumor activity of 5-iodouracil complexesSurface cationized cellulose nanofibrils for the production of contact active antimicrobial surfacesQualitative detection of ginsenosides in brain tissues after oral administration of high-purity ginseng total saponins by using polyclonal antibody against ginsenosides
- C. Soukoulis et al.
Contribution of thermal, rheological and physical measurements to the determination of sensorially perceived quality of ice cream containing bulk sweeteners
Journal of Food Engineering
- Y. Okahisa et al.
Optically transparent wood-cellulose nanocomposite as a base substrate for flexible organic light-emitting diode displays
Composites Science and Technology
- O. Nechyporchuk et al.
Production of cellulose nanofibrils: a review of recent advances
Industrial Crops and Products
- H.S. Mansur et al.
FTIR spectroscopy characterization of poly (vinyl alcohol) hydrogel with different hydrolysis degree and chemically crosslinked with glutaraldehyde
Materials Science and Engineering C
- H.S. Mansur et al.
Characterization of poly(vinyl alcohol)/poly(ethylene glycol) hydrogels and PVA-derived hybrids by small-angle X-ray scattering and FTIR spectroscopy
- P.K. Khanna et al.
Water based simple synthesis of re-dispersible silver nano-particles
Absorption, distribution and excretion of [14C]CTAB, a quaternary ammonium surfactant, in the rat
Food and Cosmetics Toxicology
Vegetable nanocellulose in food science: a review
Transparent chitosan films reinforced with a high content of nanofibrillated cellulose
Review of the oral toxicity of polyvinyl alcohol (PVA)
Food and Chemical Toxicology
Purification, characterization and comparative studies of spray-dried bacterial cellulose microparticles
Evaluating cell wall structure and composition of developing cotton fibers using Fourier transform infrared spectroscopy and thermogravimetric analysis
Journal of Applied Polymer Science
Water redispersible cellulose nanofibrils adsorbed with carboxymethyl cellulose
Cellulose nanomaterials in water treatment technologies
Environmental Science and Technology
Composite films based on biorelated agro-Industrial waste and poly(vinyl alcohol)
Preparation and Mechanical Properties Characterization. Biomacromolecules
Pulp and paper chemistry and technology volume 1. wood chemistry and wood biotechnology (1st ed., vol. 1)
Pulp and paper chemistry and technology volume 2. pulping chemistry and technology (1 st ed., vol. 2)
Preparation and characterization of water-redispersible nanofibrillated cellulose in powder form
Avoiding aggregation during drying and rehydration of nanocellulose
Effect of residual lignin and heteropolysaccharides in nanofibrillar cellulose and nanopaper from wood fibers
Flocculation of microfibrillated cellulose in shear flow
Redispersion of dried plant nanocellulose: A review
2022, Carbohydrate Polymers
Citation Excerpt :
Various organic additives have been investigated, including maltodextrin (Velasquez-Cock et al., 2018a), surfactant (Esparza et al., 2019), polyvinyl alcohol (Velasquez-Cock et al., 2018b), PEG (Cheng et al., 2015), hydrophilic gelatin (Kwak et al., 2019). Velasquez-Cock and colleagues (Velasquez-Cock et al., 2018a; Velasquez-Cock et al., 2018b) described the utilization of two capping agents, polyvinyl alcohol and maltodextrin, to improve the CNF redispersibility, which improved significantly as the amount of capping agents increased. Unfortunately, capping agents are required in substantial quantities (at least 150 % of CNF weight) to redisperse dried CNFs properly (noting some of the added capping agents are removed through filtrating or hot-water washing) (Velasquez-Cock, Ganan, et al., 2018; Velasquez-Cock et al., 2018b).See AlsoPreparation method and application of cation-modified glycoprotein type microorganism flocculating agentColloidal properties and cytotoxicity of enzymatically hydrolyzed cationic starch-graft-poly(butyl acrylate-co-methyl methacrylate) latex by surfactant-free emulsion polymerization for paper coating applicationViscoelastic auxiliary agent, and composition, preparation method and application thereofSimultaneous detection of type A and type B trichothecenes in cereals by liquid chromatography–electrospray ionization mass spectrometry using NaCl as cationization agent
Nanocellulose has undergone substantial development as a high value-added cellulose product with broad applications. Dried products are advantageous to decrease transportation costs. However, dried nanocellulose has redispersion challenges when rewetting. In this work, drying techniques, factors affecting redispersibility, and strategies improving the nanocellulose redispersibility are comprehensively reviewed. Hydrogen bonds of nanocellulose are unavoidably developed during drying, leading to inferior redispersibility of dried nanocellulose, even hornification. Drying processes of nanocellulose are discussed first. Then, factors affecting redispersibility are discussed. Following that, strategies improving the nanocellulose redispersibility are analyzed and their advantages and disadvantages are highlighted. Surface charge modification and steric hindrance concept are two main pathways to overcome the redispersion challenge, which are mainly carried out by chemical modification, additive incorporation and non-cellulosic component preservation. Despite several advancements having been achieved, new approaches for enhancing the nanocellulose redispersibility are still required to promote the industrial-scale applications of nanocellulose in various domains.
Eco-friendly alkaline lignin/cellulose nanofiber drying system for efficient redispersion behavior
2022, Carbohydrate Polymers
Although nanocellulose is an eco-friendly, high-performance raw material provided by nature, the agglomeration of nanocellulose that occurs during the drying process is the biggest obstacle to its advanced materialization and commercialization. In this study, a facile and simple nanocellulose drying system was designed using lignin, which is self-assembled together with cellulose in natural wood, as an eco-friendly additive. The addition of lignin not only minimized aggregation during the drying and dehydration process of nanocellulose but also ensured excellent redispersion kinetics and stability. In addition, the added lignin could be removed through a simple washing process. Through FTIR, XRD, TGA, tensile and swelling tests, it was confirmed that the addition of lignin enabled the reversible restitution of the nanocellulose physicochemical properties to the level of pristine never-dried nanocellulose in drying, redispersion, and polymer processing processes.
Production of bacterial cellulose tubes for biomedical applications: Analysis of the effect of fermentation time on selected properties
2021, International Journal of Biological Macromolecules
Citation Excerpt :
The Congo red dye adsorption method is generally considered an accurate method for the measurement of the SSA of cellulosic materials in the never-dried state . SSA determination by this method has previously proved useful for inferring the relative aggregation of dehydrated and later redispersed cellulose nanofibrils of plant origin , as well as for assaying the effect of processing methods on the SSA of microfibrillated cellulose isolated from hardwood pulp samples . Congo red has a high degree of specificity for the (1–>4)-beta-D-glucopyranosic units of cellulose, being its adsorption strongly dependent on the pH of the medium .
Biosynthesis of bacterial cellulose (BC) in cylindrical oxygen permeable molds allows the production of hollow tubular structures of increasing interest for biomedical applications (artificial blood vessels, ureters, urethra, trachea, esophagus, etc.). In the current contribution a simple set-up is used to obtain BC tubes of predefined dimensions; and the effects of fermentation time on the water holding capacity, nanofibrils network architecture, specific surface area, chemical purity, thermal stability, mechanical properties, and cell adhesion, proliferation and migration of BC tubes are systematically analysed for the first time. The results reported highlight the role of culture time on key properties of the BC tubes produced, with significant differences arising from the denser and more compact fibril arrangements generated at longer fermentation intervals.
Nanocellulose/polyethylene nanocomposite sheets prepared from an oven-dried nanocellulose by elastic kneading
2021, Composites Science and Technology
Citation Excerpt :
Furthermore, the addition of DEG to the TEMPO-CNF/water dispersion probably enabled fibrillation of TEMPO-CNFs in the PE matrix during kneading. We attribute this DEG preventing the formation of interfibrillar hydrogen bonds [25,26]. As a result, when both the cationic surfactant and DEG are present, a homogeneous distribution is achieved.
Nanocellulose-reinforced polyethylene composite sheets were prepared with an in situ surface-hydrophobized, TEMPO-oxidized cellulose nanofibrils (TEMPO-CNFs) and polyethylene by thermal kneading with high shear forces (i.e., under ‘elastic’ kneading conditions). First, diethylene glycol (DEG) and cationic surfactant were added to a 1% TEMPO-CNF/water dispersion, and the mixture was agitated to prepare a foam. This foam was oven-dried at 40°C for ~2 days to prepare a bulky and soft product. This oven-dried TEMPO-CNF/surfactant/DEG was added to maleic anhydride-modified polyethylene at 120–135°C, and the mixture was elastically kneaded to prepare a TEMPO-CNF/surfactant/polyethylene master batch. The DEG and water molecules present in the oven-dried product were completely removed during kneading. The master batch was further kneaded with polyethylene to prepare TEMPO-CNF/cationic surfactant/polyethylene composite sheets. No detectable aggregates of TEMPO-CNFs were observed in the scanning electron microscopy images of the composite sheets. The yield stress and modulus of the sheets linearly increased with increasing TEMPO-CNF content up to ~8vol%. Therefore, we successfully reinforced polyethylene with TEMPO-CNFs using our oven-drying and elastic kneading method.
Prevention of interfibril hornification by replacing water in nanocellulose gel with low molecular weight liquid poly(ethylene glycol)
2020, Carbohydrate Polymers
Nanocellulose is typically stored and transported as a gel with a nominal solid content of up to 5 wt.-% to avoid interfibril hornification, i.e. the formation of irreversible hydrogen bonds between adjacent nanocellulose upon drying, which makes nanocellulose not cost-effective. In this work, we report the use of low molecular weight liquid poly(ethylene glycol) (PEG-200) as a replacement for the water phase in nanocellulose aqueous gel. Our results indicated that nanocellulose can be stored in PEG-200 at a solid content of up to 70 wt.-% without interfibril hornification, even when exposed to the ambient environment. This is due to the low vapour pressure and high boiling point of PEG-200. ATR-FTIR and ζ-potential measurements confirmed that PEG-200 can be easily washed out from the nanocellulose as PEG-200 is water miscible. Using PEG-200 as a replacement for the water phase in nanocellulose aqueous gel could improve the cost-efficiency of nanocellulose storage and transportation. The tensile properties of the cellulose nanopaper prepared from the various never-dried and once-dried nanocellulose are also discussed in this work.
Synthesis and characterization of novel poly(3-aminophenyl boronic acid-co-vinyl alcohol) nanocomposite polymer stabilized silver nanoparticles with antibacterial and antioxidant applications
2020, Colloids and Surfaces B: Biointerfaces
Citation Excerpt :
Emphatically, the alteration in the peak of PVA at 1420 cm−1 further validated this submission. This similar result has been observed by Velásquez-Cock et al. . The thermal stability of PVA and (PABA-PVA)AgNPs were assessed by TGA (Table S1 and Fig. 5A) and DTG analysis (Fig. 5B).
In this work, the synthesis method and applications of nanocomposite polymer stabilized silver nanoparticles (AgNPs) are reported. 3-Aminophenyl boronic acid (3APBA) was used as a reductant of silver nitrate which acted as an oxidant for the polymerization of 3APBA through in situ chemical oxidative polymerization to poly(3-aminophenyl boronic acid) or PABA. The formation of PABA in the reaction mixture led to particle agglomeration owing to PABA poor solubility. However, in the presence of hydrophilic poly(vinyl alcohol) (PVA), PABA binds to the free hydroxyl group of PVA to form a composite polymer (PABA-PVA), which perfectly stabilized the formed AgNPs. Succinctly, PVA acted as a solubilizer and stabilizer for (PABA-PVA)AgNPs synthesis. Synthesis was optimized and sharp absorption peaks at 290 nm and 426 nm were observed, attributing to the π-π* transition of the benzenoid ring of PABA and the characteristic absorption spectrum of AgNPs, respectively. (PABA-PVA)AgNPs was characterized using UV–vis, TEM, FESEM, EDX, XRD, FTIR, TGA/DTG, DLS and zeta potential analysis. In addition, the antibacterial, antioxidant and metal chelating capacities of (PABA-PVA)AgNPs were evaluated. The (PABA-PVA)AgNPs exhibited significant antibacterial activity against Escherichia coli and Listeria monocytogenes, and good antioxidant and metal chelating properties of (PABA-PVA)AgNPs, thus validating its attractive biological applications.
Preparation and characterization of cationic and amphoteric mannans from Candida albicans
Carbohydrate Polymers, Volume 149, 2016, pp. 1-7
Cationic and amphoteric mannans from Candida albicans were prepared by chemical modification with (3-chloro-2-hydroxypropyl)trimethylammonium chloride (CHPTAC) and sodium chloroacetate under aqueous alkaline conditions. The optimal reaction conditions for mannan cationization were found to be 6h, 60°C, and NaOH/CHPTAC ratio of 1.0. Adjusting the molar ratio of cationization agent to anhydromannose unit, cationic and amphoteric mannans with degree of substitution ranging from 0.07 to 0.57 were obtained. Their structure was confirmed by elemental analysis as well as FTIR and NMR spectroscopies. Moderate decrease of molecular weight of both cationic and amphoteric mannans was recorded by size exclusion chromatography. With increasing level of modification, reduction of the antibody-binding capacity was observed by enzyme-linked immunosorbent assay.
Assessing cellulose nanofiber production from olive tree pruning residue
Carbohydrate Polymers, Volume 179, 2018, pp. 252-261
Pruning operation in olive trees generates a large amount of biomass that is normally burned causing severe environmental concern. Therefore, the transformation of this agricultural residue into value-added products is imperative but still remains as a technological challenge.
In this study, olive tree pruning (OTP) residue is evaluated for the first time to produce cellulose nanofibers (CNF). The OTP bleached pulp was treated by TEMPO-mediated oxidation and subsequent defibrillation in a microfluidizer. The resulting CNF was characterized and compared to CNF obtained from a commercial bleached eucalyptus kraft pulp using the same chemi-mechanical procedure.
CNF from OTP showed higher carboxylate content but lower fibrillation yield and optical transmittance as compared to eucalyptus CNF. Finally, the visco-elastic gel obtained from OTP was stronger than that produced from eucalyptus. Therefore, the properties of CNF from OTP made this nanomaterial suitable for several applications.
CNF from OTP showed higher carboxylate content as compared to eucalyptus CNF (1038 vs. 778μmol/g) but lower fibrillation yield (48% vs. 96%) and optical transmittance. Finally, the visco-elastic gel obtained from OTP was stronger than that produced from eucalyptus. Therefore, the properties of CNF from OTP made this nanomaterial suitable for several applications.
Temperature stability of nanocellulose dispersions
Carbohydrate Polymers, Volume 157, 2017, pp. 114-121
Cellulose nanofibrils (CNF) have potential as rheology modifiers of water based fluids, e.g. drilling fluids for use in oil wells or as additives in injection water for enhanced oil recovery (EOR). The temperature in oil wells can be high (>100°C), and the retention time long; days for drilling fluids and months for EOR fluids. Hence, it is important to assess the temperature stability over time of nanocellulose dispersions to clarify their suitability as rheology modifiers of water based fluids at such harsh conditions. Dispersions of CNF produced mechanically, by using TEMPO mediated oxidation and by using carboxymethylation as pretreatment, in addition to cellulose nanocrystals (CNC), have been subjected to heat aging. Temperature stability was best for CNC and for mechanically produced CNF that were stable after heating to 140°C for three days. The effect of additives was evaluated; cesium formate and sodium formate increased the temperature stability of the dispersions, while there was no effect of using phosphate buffer.
On the use of microwave pretreatment to assist zero-waste chemical-free production process of nanofibrillated cellulose from lime residue
Carbohydrate Polymers, Volume 230, 2020, Article 115630
Microwave (MW) pretreatment as an energy-efficient method to enhance the production of nanofibrillated cellulose (NFC) from lime (Citrus aurantifolia Swingle) residue after juice extraction is proposed. NFC was prepared by subjecting lime residue to MW pretreatment for up to 3 rounds; this was followed by high-shear and high-pressure homogenization. Repeated application of MW pretreatment helped remove non-cellulosic components and resulted in an increased cellulose content and crystallinity index but a decrease in fiber diameter. Freshly prepared NFC sample exhibited gel-like behavior. G′ and G″ of suspension prepared from dried NFC markedly decreased, indicating the loss of gel-like property upon drying. Proper pectin molecular weight as well as pectin content were noted to play an important role in controlling aggregation of NFC during drying and hence water redispersibility of dried NFC. Significant amounts of pectin and limonin could be recovered and utilized as co-products after the first round of MW pretreatment.
Extraction and comparison of cellulose nanocrystals from lemon (Citrus limon) seeds using sulfuric acid hydrolysis and oxidation methods
Carbohydrate Polymers, Volume 238, 2020, Article 116180
In this study, the lemon (Citrus limon) seeds as typical agricultural processing wastes were utilized to extract cellulose nanocrystals (CNCs) by sulfuric acid hydrolysis (S-LSCNC), ammonium persulfate oxidation (A-LSCNC) and TEMPO oxidation (T-LSCNC). The properties of CNCs were comparatively investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TG), and atomic force microscope (AFM), and the application in Pickering emulsions was also preliminarily studied. The results showed that all CNCs maintained cellulose Iβ structure and had a good dispersion regardless of extraction methods. Differently, T-LSCNC had a higher yield, larger size and lower CrI than A-LSCNC and S-LSCNC. Comparatively, A-LSCNC showed the highest CrI and S-LSCNC showed the lowest size. For the application of Pickering emulsions, S-LSCNC and A-LSCNC showed a better ability as Pickering stabilizers than T-LSCNC. This study is beneficial for developing the potential utilization of CNCs from lemon by-products.
Adsorption of polyethylene glycol (PEG) onto cellulose nano-crystals to improve its dispersity
Carbohydrate Polymers, Volume 123, 2015, pp. 157-163
In this work, the adsorption of polyethylene glycol (PEG) onto cellulose nano-crystals (CNC) was investigated for preparing re-dispersible dried CNC. Results showed that the re-dispersity of CNC in water can be significantly enhanced using a PEG1000 dosage of 5wt% (based on the dry weight of CNC). The elemental analysis confirmed the adsorption of PEG onto the CNC surface. Transmission electron microscopy (TEM) was used to characterize the dry powder and indicated that the irreversible agglomeration of CNC after drying was essentially eliminated based on the PEG adsorption concept. Thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) suggested that CNC crystallinity and thermal stability were not affected by the adsorption of PEG. Thus, the adsorption of PEG has great potential for producing re-dispersible powder CNC.
© 2017 Elsevier Ltd. All rights reserved.
What is the use of polyvinyl alcohol? ›
PVA is used in many industries, such as textile, paper industry, and food packaging industry [29,54] because of its high chemical and thermal stability, and low manufacturing cost . It is also a popular water-soluble polymer and has high strength and high optical transparency in water.What is PVA soluble in? ›
PVA is highly soluble in water as it comprises a large amount of hydroxyl groups, which interact with the water molecules through hydrogen bonds. The PVA solubility depends on its degree of hydrolysis and molecular weight . The degree of hydrolysis of the PVA is inversely proportional to its solubility.How is PVA synthesized? ›
It is manufactured by the polymerization of vinyl acetate followed by partial hydrolysis. The process of hydrolysis is based on the partial replacement of ester group in vinyl acetate with the hydroxyl group, and is completed in the presence of aqueous sodium hydroxide.What is the shelf life of polyvinyl alcohol? ›
The recommended shelf life on PVA glue is generally a way for the company to cover its butt. One year is simply the length of time they will guarantee the quality level. But most glues can go for two years or more if stored consistently at room temp.What is the disadvantage of polyvinyl alcohol? ›
The major disadvantage of PVA based composites/films is higher water uptake or solubility in water. To over this negative aspect, many researchers studied crosslinking of PVA based composites/films, which are also discussed in the article.Is polyvinyl alcohol used as a thickening agent? ›
Poly(vinyl alcohol), made by removing acetate groups from poly(vinyl acetate), is a polymer used in a tremendous variety of products: as a vapor barrier in 2-L soda bottles, a thickening agent in shampoos, and the polymer that kids call "slime".At what temperature does PVA dissolve? ›
The dissolving temperature range for conventional PVA water-soluble fibers made from wet spinning process is about 40°C.What is another name for PVA? ›
Polyvinyl acetate (PVA, PVAc, poly(ethenyl ethanoate)), commonly known as wood glue, PVA glue, white glue, carpenter's glue, school glue, or Elmer's glue in the US, is a widely available adhesive used for porous materials like wood, paper, and cloth.What does PVA do in nanoparticles? ›
PVA is a biocompatible polymer that can absorb moisture content for hydrogel formation . Therefore, coating nanoparticle surfaces with modification using polyvinyl alcohol can prevent agglomeration resulting in monodisperse particles, coagulation, and stabilizing nanoparticles from oxidation .What is the solvent for polyvinyl alcohol? ›
Poly(vinyl alcohol), a biocompatible and biodegradable polymer, is readily soluble in polar solvents like water and dimethyl sulfoxide (DMSO). Out of the two solvents, DMSO is reported to be a better solvent for PVA than water.
Is Elmer's glue PVA? ›
Polyvinyl acetate is a component of a widely used glue type, commonly referred to as wood glue, white glue, carpenter's glue, school glue, Elmer's glue (in the US), or PVA glue.”Is PVA toxic to humans? ›
Is polyvinyl alcohol toxic to humans? It is not toxic.Is PVA the same as polyvinyl alcohol? ›
Polyvinyl alcohol (PVA) is a water-soluble synthetic resin used widely in paints.Is PVA FDA approved? ›
PVA is unique in that it is one of very few polymers with excellent biocompatibility and safety and has FDA approval for clinical uses in humans.Why is polyvinyl alcohol bad for you? ›
However, the ingredients inside the PVA encasement are often not as safe. Pods made from PVA may contain highly concentrated detergents that can cause harm if consumed or exposed to our skin.Is PVA carcinogenic? ›
No evidence of carcinogenic activity is demonstrated by studies that are interpreted as showing no chemical-related increases in malignant or benign neoplasms.What is polyvinyl alcohol also known as? ›
Polyvinyl alcohol also known as PVA, PVOH, or PVAI, water soluble synthetic polymers, made from polyvinyl acetate. Most of the polymers are manufactured by polymerization of its monomeric unit.What is a substitute for polyvinyl alcohol? ›
Although not suitable for items that must stand up to washing, a gelatin/glycerin glue can be used for fabric crafts in place of PVA. The glycerin makes the glue stay flexible after it dries.Is it safe to use polyvinyl alcohol? ›
Is Polyvinyl Alcohol Safe? Polyvinyl alcohol is a non-toxic, colorless, and odorless biodegradable polymer that is safe to use and consume. The PVA film on products is designed to dissolve as intended, and has unique features to avoid spillage and ensure consumer safety.What is the absorption of PVA? ›
The pure PVA films have the highest moisture absorption compared to blend and pure starch films. The value of moisture absorption of pure PVA film at 8 h is 41.97%. This is different from pure starch films which only have 36.50% in these conditions. It is indicated that PVA is more hydrophilic than bengkuang starch.
What happens to PVA when heated? ›
Overheating will cause water evaporation and a thick film will form on top of the solution. Also, very high heat may interfere with the hydrogen bonding interaction which is occurring between the polyvinyl alcohol and the water. It will easily take 20 minutes to make the 1-L solution, so please be patient.Can PVA withstand heat? ›
He is correct that PVA white glue can be heated and softened... Normally it's used when repairing veneering or to take joints apart in joinery, it's a trick of the trade.How long does it take for PVA to dissolve? ›
Typical time to fully dissolve PVA would be between 12-18 hours. This will vary depending on the brand of PVA you are using. There are a number of ways you can reduce the amount of time it takes to fully dissolve your PVA supports.What are the best solvents for PVA? ›
All Polyvinyl Alcohol grades are readily soluble in water. Other solvents include dimethyl sulfoxide, acetamide, glycols, and dimethylformamide.Does vinegar dissolve PVA? ›
You can count this product as a handy tool to dissolve PVA glue. Many people use this natural solution as an easy method to prevent dry wood. It doesn't damage the wood if you can do it properly. A half-cup of white vinegar is enough to give it a try.
PVA is soluble in water but insoluble in acetone. Layering acetone over a 4% solution of PVA creates a white interface of PVA fibers which can be pulled upwards through the acetone to produce a PVA rope.What are the two types of PVA? ›
There are two main types of PVA glue: white PVA and yellow PVA glue. The yellow variety of this glue tends to be fairly pricey, which is why many people will avoid it. The white PVA glue is much more affordable and is therefore usually the main choice for interior works of all sorts.Is PVA same as latex? ›
PVA glue basically adheres the same way as liquid latex, so u can get away with most looks. BUT it is not as flexible or as strong. Here's a perfect example of sfx wounds using only glue! 3 EASY WOUNDS without liquid latex – Makeup Tutorial – Alexander...Is polyvinyl alcohol actually alcohol? ›
PVA starts as ethylene. Then, oxygen and acetic acid (or vinegar when it's diluted) turn the ethylene into vinyl acetate — which is then dissolved into alcohol to become Polyvinyl Alcohol.How do you remove PVA from nanoparticles? ›
To remove PVA, nanoparticles were centrifuged at 17,000 × g for 10 min, the supernatant was discarded and nanoparticles were resuspended in water as previously described (Yang et al., 2019).
What are the advantages and disadvantages of PVA? ›
Polyvinyl acetate or PVA glue is one of the most readily available glues on the market, as it includes basic school glue. Since it is water based, it is easy to clean up, but it is also not waterproof or water-resistant in most cases.What is PVA in nanotechnology? ›
Polyvinyl alcohol (PVA) is a bio-friendly polymer since it is water soluble and has extremely low cytotoxicity. This allows a wide range of potential biomedical applications. It is used as a stabilizer due to its optical clarity which enables investigation of nanoparticle formation.Does PVA dissolve in alcohol? ›
PVAL is insoluble in most organic solvents and only slightly soluble in ethanol while typical pipeline drug molecules are only slightly soluble in more aggressive organic solvents.How do you mix PVA for sealing? ›
Dilute 1 part PVA with 4 parts water and mix well. Apply using a brush, working material well into crevices and gaps. Allow the coat to dry before continuing.Is Mod Podge and PVA glue the same? ›
Is it the same as PVA glue? Mod Podge contains PVA, but it's not the same. There are additional ingredients in Mod Podge.Is Gorilla glue a PVA glue? ›
Gorilla Wood Glue, a PVA glue, offers the benefits of an easy-to use, water-based adhesive, with Gorilla strength. It is incredibly water resistant and versatile, making it great for both indoor and outdoor wood working projects.Where should PVA glue not be used? ›
Most PVA Glues Are Not Waterproof: One of the main disadvantages of this type of glue is the fact that 99% of them are not fully waterproof, which means that you can't really use it as an adhesive in things like boats, or anything that you might leave outdoors.Does PVA release Microplastics? ›
While it serves a beneficial purpose, these laundry pods are one of the main sources for PVA microplastics which can be found in many everyday items.Does PVA produce Microplastics? ›
PVA films are manufactured to be completely biodegradable, meaning that once they dissolve they do not break into microplastics.Is PVA a fire retardant? ›
Like most polymers, PVA is flammable, which is a potential hazard to the above-mentioned application. The common solution to improving the flame retardancy of PVA is incorporating flame retardants into the polymer matrix by physical mixing or by chemical reaction [4–8].
What is the strongest PVA? ›
Gorilla wood glue is some of the strongest wood glue in the world, and for many woodworkers, it is the only wood glue they trust. This PVA glue sets up in 20-30 minutes, depending on the temperature, and offers an almost permanent bond for any wood joint.Why is PVA not made from vinyl alcohol? ›
Although poly(vinyl alcohol) (PVA) is one of the synthetic polymers composed of vinyl monomer units similarly to polystyrene or polypropylene, PVA cannot usually be prepared directly from vinyl alcohol as the monomer because vinyl alcohol itself is unstable and readily tautomerized into acetaldehyde.What household items have polyvinyl alcohol in them? ›
PVA is used in many products like shampoos, masks,makeup, skin care products, and hairsprays. In other industries PVA is used in: paper coatings, latex paints, glues and as a textile sizing agent, a carbon dioxide barrier in PET bottles and as a plastic backing sheet in adult incontinence and feminine hygiene products.Is PVA cytotoxic? ›
All nPVA solutions were cytotoxic at a threshold molar concentration that correlated with the molecular weight of the starting PVA polymer. In contrast, none of the nonelectrospun PVA solutions caused any cytotoxicity, regardless of their concentration in the cell culture.What is polyvinyl alcohol used for? ›
PVA is used in many industries, such as textile, paper industry, and food packaging industry [29,54] because of its high chemical and thermal stability, and low manufacturing cost . It is also a popular water-soluble polymer and has high strength and high optical transparency in water.What products are made from polyvinyl alcohol? ›
Elvanol™ polyvinyl alcohol is widely used in diverse applications such as adhesives for paper, wood, textiles, leather, and other water-absorbent substrates; photosensitive coatings; specialty molded products; water-soluble, gas-tight films; paper and paperboard; and binders for pigmented paper coatings, ceramic ...Is polyvinyl alcohol in Elmer's glue? ›
Now Elmer's Glue-All is an aqueous emulsion of Polyvinyl acetate, Polyvinyl alcohol, and Propylene glycol distributed in plastic squeeze type bottles with twist-open dispenser lids. It is widely used in homes, businesses, and schools and effectively bonds most materials, such as wood, paper, and fabric.Is polyvinyl alcohol toxic to humans? ›
Is it safe for humans? Sub-chronic toxicity and genotoxicity studies confirm that PVA is safe for humans when exposed via numerous exposure pathways in typical daily exposure (1,2). However, the ingredients inside the PVA encasement are often not as safe.What is the chemical name for polyvinyl alcohol? ›
Poly(vinyl alcohol) (PVOH, PVA, or PVAl) is a water-soluble synthetic polymer. It has the idealized formula [CH2CH(OH)]n.Is Elmer's glue and PVA the same? ›
Polyvinyl acetate is a component of a widely used glue type, commonly referred to as wood glue, white glue, carpenter's glue, school glue, Elmer's glue (in the US), or PVA glue.”
What is polyvinyl alcohol found in? ›
PVA is a synthetic plastic polymer found in many of our everyday products. PVA is often found in household items like dishwasher and laundry pods and sheets as a thin single-use plastic wrapping or woven into laundry sheets themselves.What are the health effects of polyvinyl alcohol? ›
Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: eye pain, change in vision, continued eye redness/irritation. A very serious allergic reaction to this drug is rare.What does polyvinyl alcohol do to your skin? ›
It is commonly found in shampoos, conditioners, and moisturizers. Further, Polyvinyl alcohol works as an emulsifier. Due to its film-forming properties, it prevents moisture loss from the surface of the skin.Does polyvinyl alcohol create Microplastics? ›
PVA is a type of microplastic, and it's becoming increasingly prevalent in our environment.What is the difference between polyvinyl chloride and polyvinyl alcohol? ›
The term PVA stands for polyvinyl alcohol polymer material while the term PVC stands for polyvinyl chloride polymer material. The key difference between PVA and PVC is that the functional group of PVA material is an alcohol group, whereas the functional group of PVC material is a halide group.