Unmodified Cellulose Research Articles

Preparation of new green poly (amino amide) based on cellulose nanoparticles for adsorption of Congo red and its adaptive neuro-fuzzy modeling

In this study, a novel green poly(amino amide) nanoparticle based on cellulose nanoparticles (Cell-PAMN) was developed for the efficient adsorption of Congo Red dye. Cellulose nanocrystals obtained from acid hydrolysis of cotton linter were functionalized via Oxa-Michael addition of acrylamide on their surface hydroxyl groups, followed by transamidation with ethylenediamine. The resulting nanoparticles were characterized using FT-IR spectroscopy, SEM, and X-ray diffraction techniques. The as-prepared Cell-PAMN exhibited considerably higher adsorption capacity compared to unmodified cellulose nanoparticles due to the presence of amino and amide functional groups. The adsorption kinetics and the effects of parameters such as contact time and initial dye concentration on the adsorption capacity were investigated. An adaptive Neuro-Fuzzy model was used to study the efficiency of dye removal, accurately predicted the adsorption behavior of Cell-PAMN. The kinetic study results showed that the adsorption process followed a pseudo-second-order kinetic model, with a maximum adsorption capacity of around 40 mg/g. The results demonstrated the potential of the synthesized material for the removal of Congo Red from aqueous solutions, highlighting its applicability in wastewater treatment. This research contributes to the development of sustainable and eco-friendly materials for environmental remediation applications.

Clarification of apple juice using cold plasma treated mixed cellulose esters membrane: flux modeling, membrane fouling, and juice physicochemical properties evaluation

This study aimed to clarify apple juice using unmodified and low-pressure cold plasma (gas: air, power: 10 W, and exposure time: 180 s) surface-modified mixed cellulose esters (MCE) microfiltration membranes. The effect of feed pressure (20, 40, and 60 kPa), feed flow rate (10, 15, and 20 mL/s), and feed temperature (27 and 40°C) on the permeate flux was evaluated using response surface methodology (RSM). The binary interaction of feed pressure and temperature and the second-order (non-linear) interaction of feed pressure and flow rate had a significant effect on the permeate flux (P<0.05). Generally, the process at 60 kPa, 15 mL/s, and 40 °C resulted in the maximum permeate flux. The cold plasma surface modification of the MCE membrane increased the permeate flux by about 45% at the optimum process conditions. Evaluation of membrane fouling showed that the cake formation was the predominant membrane fouling mechanism during both membrane processing. The physicochemical properties evaluation revealed that the surface-modified membrane produced clarified apple juice with antioxidant activity, reducing sugars, total sugars, phenolic, and vitamin C contents about 18.87%, 12.9%, 15.49%, 24.53%, and 45.15% more than clarified apple juice produced with unmodified MCE membrane, respectively.

Facile production of water-in-oil emulsions stabilized by unmodified cellulose nanocrystals using transient double emulsions technique

For hydrophilic biomacromolecules like cellulose and cellulose nanoparticles, creating water-in-oil emulsions poses significant challenges, particularly in controlling the size distribution and the interfacial composition simultaneously. Here, we introduced a simple transient double emulsion microfluidic approach for fabricating cellulose nanocrystals (CNCs) stabilized water-in-oil emulsions. It requires no chemical modifications or extra surfactants. Moreover, it allows control over the droplet size and surface coverage by simply adjusting the flow rates and particle concentration of the middle phase of the initial double emulsion. With the increase of the outer phase flow rate from 5000 μL h−1 to 8000 μL h−1, the diameter of the droplets significantly decreased from 236.0 ± 3.0 μm to 130.2 ± 2.2 μm. Moreover, the minimum CNC concentration required for emulsion stabilization using this method was lowered to only 0.1 wt%.This work demonstrates the feasibility of combining microfluidic techniques and double emulsion methods for producing unmodified CNCs-stabilized emulsions.

In situ growth of ultrathin covalent triazine frameworks on unmodified cellulose II beads for enhanced dye pollutant removal

cellulose II beads@covalent triazine frameworks (CBCs) are prepared by in situ growth of ultra-dispersed covalent triazine frameworks (CTF) using unmodified regenerated cellulose beads (CBs) as templates. The CBCs as a whole are three-dimensional structures consisting of a layered pore structure and a continuous ultrathin CTF, which combines a functional surface with highly efficient mass transfer. The thickness of the CTF in the prepared CBCs can be controlled at 32–83 nm, which enables the CBC to have a dye adsorption efficiency of up to 191 mg g−1 and an ultrafast dye removal time (Methylene Blue, 0.5 min, 95 %). Molecular dynamics simulations revealed the mechanism for CTF growth on the surface of unmodified cellulose II rather than on the surface of cellulose Ⅰ, and the effects of the hydrophilic/hydrophobic surfaces of cellulose I and cellulose II on the growth of CTF were determined. This is the first use of unmodified cellulose II as a template for the in situ growth of ultrathin CTF and provides important insights into dynamic CTF-cellulose interactions. This research provides a new cost-effective strategy for preparation of ultra-dispersed CTF based on large-scale cellulose templates.

Surface functionalization of oil palm empty fruit bunch (OPEFB)-derived cellulose as a carboxyl platform for metal cations and dyes removal from aquatic media

The abundant oil palm empty fruit bunch (OPEFB) as by-product of palm oil milling processes exhibits a potential as an alternative cellulose feedstock for bio-adsorbent. This study aimed to produce a highly carboxylated bio-adsorbent for direct industrial application from OPEFB-based cellulose via mercerization and followed by esterification with succinic anhydride (SA) to enhance its adsorptive capability towards hazardous heavy metal and dyes ions. The modification using SA provides the carbon backbone platform for carboxyl group attachment for the contaminants. The results showed that the carboxylated cellulose had a high carboxyl content (4.39 mmol/g). Carboxylated cellulose had a higher binding capacity for adsorbates, with removal rates of 94.7%, 97.85%, 40.9%, and 90.15% for dye, Pb2+, Cu2+, and Cd2+ cations, respectively, at pH 6, 4 hours reaction time, and at room temperature. In comparison, unmodified cellulose removed only 47%, 23.1%, 2.9%, and 7.5% for dye, Pb2+, Cu2+, and Cd2+ cations, respectively. The adsorption kinetics study revealed that the adsorption process followed the pseudo-second-order model. The adsorption isotherm of these two metal cations follows the model of Langmuir very well, while Cu2+ follows the Freundlich model. Our method produces bio-adsorbents with high carboxyl content and adsorption rate in a short reaction time using OPEFB as a green precursor material that is easily scalable for industrial use.

Lyophilized Emulsions of Thymol and Eugenol Essential Oils Encapsulated in Cellulose.

Efforts to tap into the broad antimicrobial, insecticidal, and antioxidant activities of essential oils (EOs) are limited due to their strong odor and susceptibility to light and oxidation. Encapsulation of EOs and subsequent drying overcome these limitations and extend their applications. This study characterized freeze-dried (lyophilized) emulsions of eugenol (EU) and thymol (TY) EOs, encapsulated by chemically unmodified cellulose, a sustainable and low-cost resource. High-resolution scanning electron microscopy showed successful lyophilization. While the observed "flake-like" structure of the powders differed significantly from that of the emulsified microcapsules, useful properties were retained. Fourier transform infrared spectroscopy confirmed the presence of EOs in their corresponding powders and thermo-gravimetric analysis demonstrated high encapsulation efficiency (87-88%), improved thermal stability and resistance to evaporation, and slow EO release rates in comparison to their free forms. The lightweight and low-cost cellulose encapsulation, together with the results showing retained properties of the dried powder, enable the use of EOs in applications requiring high temperatures, such as EO incorporation into polymer films, that can be used to protect agricultural crops from microbial infections.

Enhancing the attraction of positively charged precursors of conductive polymer poly(3,4-ethylenedioxythiophene) by anchoring sulfonate groups in cellulose fibres

Interfacial interactions are key to the development of high-performance coatings such as conductive polymer layers on fibrous materials. In this work, we present an approach of strengthening the interaction by forming ionic bonds between cellulose fibres and the conductive polymer layer by introducing a sulfonate group on cellulose fibres. The ionic bonds are formed between anchored sulfonate group and the positively charged precursor 3,4-ethylenedioxythiophene (EDOT), followed by the deposition and polymerisation of poly(3,4-ethylenedioxythiophene):sulfate (PEDOT:SO4) on the fibrous substrate surface. The conductance of the PEDOT:SO4 coated substrate with anchored sulfonate groups coated may be 1.7 times higher compared to the conductance of the unmodified cellulose substrate depending on experimental conditions. EDX measurements confirm the presence of sulfur and a shift of zeta potential at lower pH supports the evidence of the anionic anchored groups on the fibre surface. Our study therefore provides a new way to enhance the affinity of fibrous cellulose materials towards polymer conductive coatings.

Interactions of NaCl with cellulose I$$\beta$$ crystal surfaces and the effect on cellulose hydration: a molecular dynamics study

AbstractCrystalline nanocellulose is widely used for example, in the paper-making and food industries, as support matrix material or reinforcement of polymer materials, but also in drug carrier and nanomedicine applications. Interestingly, aqueous solutions of cellulose are extremely sensitive to small amounts of added salt yet mere considerations of charge screening leave open questions regarding the mechanisms, especially for unmodified cellulose in aqueous solutions. Here, we map NaCl ion distributions and the effect of added NaCl salt on the hydration of I$$\beta$$ β cellulose nanocrystal (CNC) surfaces by atomistic detail molecular dynamics simulations with explicit water solvent. The simulations reveal the dependency of the hydration layers of the six surfaces of CNCs on the ions, as well as NaCl ion binding sites, and preferences in terms of binding free energy for the ions near CNC surfaces at different NaCl concentrations. We discuss the modelling results against our prior rheology characterization of cellulose solutions. Together, the results indicate that the high sensitivity of cellulose aqueous solutions to added salt rises from the ions near the surface changing locally the ordering and structure of the hydration layers of the CNC surfaces. The revealed mechanism of salt-induced viscosity changes in cellulose aqueous solutions allows advanced design of gelling CNC systems for various end uses and may also guide tuning cellulose interactions by different solvent environments.

P/N/S-containing cellulose nanofibrils enable curcumin encapsulation via Pickering emulsion based microcapsules

Renewable polymeric microcapsules hold promise for precisely controlled release of hydrophobic drugs (curcumin) in therapeutic treatment. However, there still remains challenges to stabilize the properties of microcapsules and to enhance encapsulation efficiencies of curcumin. By using an eco-friendly ternary deep eutectic solvent here, we successfully fabricated native cellulose nanofibrils, holocellulose nanofibrils, and lignocellulose nanofibrils containing both phytates and sulfate groups. In addition, a novel type of curcumin-loaded polymeric microcapsules with diameter of 10–20 μm were prepared by cellulose nanofibrils as stabilizing agents in Polylactide Pickering emulsion. The Pickering emulsions stabilized by P/N/S-containing cellulose nanofibrils, holocellulose nanofibrils, and lignocellulose nanofibrils are more stable than the unmodified cellulose nanofibrils-stabilized emulsion. The Pickering emulsion stabilized by 0.2 wt% P/N/S-containing lignocellulose nanofibrils exhibited the highest emulsion layer height and the zeta potential reached −39.74 ± 2.88 mV. Moreover, the highest encapsulation efficiency of curcumin can be up to 94.80%. Antimicrobial test revealed that curcumin in the polymeric microcapsules exhibited an excellent inhibitory effect on S. aureus and the antibacterial efficiency reached 98.66%. These results provided important information on the comparison of different cellulose nanofibrils-stabilized Pickering emulsions and the application of controlled release of curcumin incorporated polymeric microcapsules in drug delivery system.

Regioselectively Carboxylated Cellulose Nanofibril Models from Dissolving Pulp: C6 via TEMPO Oxidation and C2,C3 via Periodate-Chlorite Oxidation.

Regioselective C6 and C2,C3 carboxylated cellulose nanofibrils (CNFs) have been robustly generated from dissolving pulp, a readily available source of unmodified cellulose, via stoichiometrically optimized 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO)-mediated and sequential sodium periodate-sodium chlorite (PC) oxidation coupled with high-speed blending. Both regioselectively optimized carboxylated CNF series possess the widest ranges of comparable charges (0.72-1.48 mmol/g for T-CNFs vs. 0.72-1.10 mmol/g for PC-CNFs), but similar ranges of thickness (1.3-2.4 nm for T-CNF, 1.8-2.7 nm PC-CNF), widths (4.6-6.6 nm T-CNF, 5.5-5.9 nm PC-CNF), and lengths (254-481 nm T-CNF, 247-442 nm PC-CNF). TEMPO-mediated oxidation is milder and one-pot, thus more time and process efficient, whereas the sequential periodate-chlorite oxidation produces C2,C3 dialdehyde intermediates that are amenable to further chemical functionalization or post-reactions. These two well-characterized regioselectively carboxylated CNF series represent coherent cellulose nanomaterial models from a single woody source and have served as references for their safety study toward the development of a safer-by-design substance evaluation tool.

Carboxylmethyl cellulose produced from wood sawdust for improving properties of sodium alginate hydrogel in dye adsorption

Cellulose-based materials have shown immense potential for diverse applications because of their attractive properties such as excellent mechanical properties, rich hydroxyl groups for modification, and natural properties with recyclability, nontoxicity, biocompatibility, biodegradability, and environmental friendliness. This study aimed to optimize cellulose extraction from wood sawdust using deep eutectic solution (DES) treatments for the preparation of carboxymethyl cellulose (CMC) and to evaluate the application of CMC in sodium alginate (SA) microgel for dye adsorption. Cellulose extractions were optimized in reduced chemical treatment conditions with high cellulose contents (88.19 %), and selectively increased lignin removal (87.23 %). The analyses by SEM, XRD, and FT-IR revealed that carboxymethylation has successfully transformed cellulose into CMC to facilitate the significantly improved water solubility and swelling ability. The TGA curve of CMC showed a higher thermal stability (residual weight of 52 % at 300 °C) compared to unmodified cellulose due to the decomposition of the amorphous regions during the carboxymethylation. The combined biodegradable SA and water-soluble CMC composite microgels were successfully fabricated via cross-linking with calcium chloride using a microfluidic approach. The incorporation of CMC into SA microgel had enhanced mechanical properties, adsorption capacities of 160.87 and 141.48 mg/g, and adsorption–desorption efficiencies of 96.84 % and 95.41 % for crystal violet and trypan blue respectively after five cycles. The adsorption processes of both dyes can be described by Sips adsorption isotherms and pseudo-second-order kinetic models, verifying the chemical interaction-assisted process. This simple green CMC/SA adsorbent has the potential to significantly enhance the adsorption capacity of dye removal from wastewater.

Mechanical Properties of Cellulose Aerogel Composites with and without Crude Oil Filling.

Aerogels are an excellent alternative to traditional oil absorbents and are designed to remove oil or organic solvents from water. Cellulose-based aerogels can be distinguished as polymers that are non-toxic, environmentally friendly, and biodegradable. The compression measurement properties of aerogels are often evaluated using dry samples. Here, oil-soaked, hydrophobized cellulose aerogel samples were examined in comparison to dry samples with and without additional hemp fibers and various levels of starch for crosslinking. The samples were characterized by compression measurement properties and filmed to evaluate the regeneration of the sorbent with repeated use. Overall, the measurements of the mechanical properties for the dry samples showed good reproducibility. The Young's modulus of samples with additional hemp fibers is significantly increased and also shows higher strength than samples without hemp fibers. However, samples without hemp fibers showed slightly better relaxation after compression. Oil acts as a weak plasticizer for all aerogel samples. However, it is important to note that the oil does not cause the samples to decompose in the way unmodified cellulose aerogels do in water. Therefore, using hydrophobized cellulose aerogels as sorbents for oil in a sea or harbor with swell means that they can be collected in their entirety even after use.

The Strength and Fire Properties of Paper Sheets Made of Phosphorylated Cellulose Fibers.

Phosphorylated cellulose can be an intrinsic flame retardant and a promising alternative for halogenated fire inhibitors. In this study, the mixture of di-ammonium hydrogen phosphate (DAP) and urea (U), containing phosphate and nitrogen groups, was applied to attain fire inhibitor properties. Functional groups of cellulose were grafted with phosphorous by keeping the constant molar ratio of 1/1.2/4.9 between anhydroglucose units of cellulose/DAP/U in different concentrations of bleached kraft pulp. Phosphorus concentrations were determined using the ICP hrOES method, and paper sheets were made using the Rapid Köthen apparatus. The tensile strength of phosphorylated cellulose increased twice compared with unmodified cellulose when the phosphorous concentration increased to 10,000 g/kg. An increase in the tensile index comes from the higher freeness of pulp and cross-linking of the phosphorous group between cellulose fibers. Remarkable fire retardancy effects were achieved in cellulose concentrations above 5 wt%. The raised phosphorous concentration above 10,000 g/kg due to the phosphorylation process caused the formation of a char layer on a cellulose surface and the nonflammable gas emission. That effect was indirectly confirmed by reducing the combustion temperature and HRR by 50 and 45%, respectively. Due to increasing phosphorus concentration in cellulose sheets, cellulose's fire and strength properties increased significantly.

Cellulose-embedded polyacrylonitrile/amidoxime for the removal of cadmium (II) from wastewater: Adsorption performance and proposed mechanism

The adsorption of metals using unmodified cellulose is often unsatisfactory owing to insufficient active functional groups on its surface. The objective of this work is to modify cellulose to enhance its adsorption capacity for cadmium (II). In this work, a chelating polyacrylonitrile/amidoxime-functionalized cellulose (Cel/PAN/AO) composite was successfully synthesized as modified cellulose and applied as a novel adsorbent to efficiently remove Cd2+ from aqueous solution. Cel/PAN/AO composite was synthesized by Michael's addition between cellulose and acrylonitrile, followed by amidoximation. Tools including SEM, EDS, FTIR, XRD, TGA, XPS, BET, and zeta potential were exploited to give insights about the Cel/PAN/AO adsorbent nature as well as the adsorption mechanism. The numerous available adsorption active sites embedded into modified cellulose contribute to enhancing the adsorption capacity of Cel/PAN/AO (in comparison to unmodified cellulose) toward Cd2+. Using the produced composite, cadmium was removed from the water at 50 mg/L Cd2+ by reacting 0.1 g Cel/PAN/AO with Cd2+ at pH 5 for 90 min at 298 K. The maximum adsorption capacity of Cel/PAN/AO toward Cd2+ was 123.23 mg/g. Cel/PAN/AO adsorbent exhibits competitive adsorption capacity as compared with other reported adsorbents. Pseudo-first-order and Langmuir's isotherm fit the sorption mechanism quite well. Cd2+ sorption onto the Cel/PAN/AO composite was found to be an exothermic, random, and spontaneous process in the thermodynamic analyses. Moreover, Cd2+ adsorption was also confirmed through SEM, EDS, FTIR, and XPS analysis of Cd2+-loaded adsorbent. Using 0.9 M KCl and 1:70 S:L ratio for 90 min, Cd2+ was also desorbed from Cd-loaded Cel/PAN/AO. In addition, after six cycles of Cd2+ adsorption-elution, the Cel/PAN/AO sorbent was regenerated and showed excellent reusability. It appears from the adsorption performance results of this work that the Cel/PAN/AO formulation has promise as an adsorbent for extracting Cd2+ from wastewater.

Cellulose nanofiber aerogels modified with titanium dioxide nanoparticles as high-performance nanofiltration materials

Air pollution is a major environmental and public health issue. Each year, large amounts of particulate matter (PM) and other harmful pollutants are released into the atmosphere. Conventional polymer nanofiber filters lack the functionality to capture ultrafine PM. As a sustainable alternative, this work developed titanium dioxide (TiO2) nanoparticle surface-modified cellulose nanofiber (CNF) aerogels for PM2.5 filtration. CNFs were extracted via mechanical disintegration to diameters below 100 nm. The nanofibers were functionalized with 1.0–2.5 wt% TiO2 nanoparticles using citric acid cross-linking. Cylindrical aerogels were fabricated by freezing and lyophilizing aqueous suspensions. Structural, morphological, thermal, and mechanical properties were characterized. TiO2 modification increased density (11.8–19.7 mg/cm3), specific surface area (287–370 m2/g), and Young's modulus (33.5–125.5 kPa) but decreased porosity (99.6 %–97.7 %), pore size (20.2–15.6 nm) and thermal stability compared to unmodified cellulose aerogels. At 2.5 wt% loading, the optimized aerogels achieved 100 % absorption of 0.1–5 μm particulates owing to reduced pore size. Despite enhanced filtration capabilities, the modified CNF aerogels retained inherent biodegradability, degrading over 70 % within one month of soil burial. This pioneering research establishes TiO2 functionalized CNF aerogels as promising sustainable alternatives to traditional petroleum-based air filters, representing an innovative approach to creating next-generation nanofiltration materials capable of effectively capturing fine and ultrafine particulate matter pollutants.

Improving cellulose acetate mixed matrix membranes by incorporating hydrophilic MIL-101(Cr)-NH2 nanoparticles for treating dye/salt solution

Mixed matrix membranes were developed by incorporating hydrophilic MIL-101(Cr)–NH2 nanoparticles into a cellulose acetate (CA) matrix, resulting in enhanced hydrophilicity. By enhancing hydrophilicity, mixed matrix membranes were developed to counter the common issue of fouling that occurs when using membranes for the treatment of industrial wastewater. The mixed matrix membrane structures demonstrated impressive stability, with minimal change in water contact angle over a period of 30 days. The incorporation of MIL-101(Cr)–NH2 into the cellulose acetate membrane resulted in a reduction of the water contact angle from approximately 65.1˚ to 50.3˚, improving hydrophilicity. Even with just 1 wt% of MIL-101(Cr)–NH2 added to the cellulose acetate matrix, the pure water flux was significantly increased by 150 % to 68.1 ± 0.87 L/m2h, due to the enhanced hydrophilicity and larger pore size while maintaining a similar level of salt rejection. The prepared membranes exhibited high rejection (>97 %) of Methyl Blue dye through size exclusion mechanism. Additionally, the flux recovery ratio (FRR) improved significantly, increasing from approximately 54 % for the unmodified cellulose acetate membrane to 82 % for the mixed matrix membrane containing 0.2 wt% MIL-101(Cr)–NH2, demonstrating a significant improvement in the antifouling properties of the prepared membrane.

Cracking polymer coatings of paper-like surfaces: Control via block co-polymer structure and system composition

Dissipative particle dynamics simulations are employed to examine the self-assembly of a three-component polymeric coating on a hydrophilic surface. The examined suspension is composed of an amphiphilic di-block co-polymer, a hydrophobic polymer, and a hydrophilic stabilizer in water. For technological relevance, the basis hydrophobic and hydrophilic polymer contents correspond to poly(styrene-co-n-butyl acrylate) and to starch, respectively, while the hydrophilic surface resembles unmodified cellulose. We show that the amphiphilic di-block co-polymer is key in controlling the assembling coating structure: symmetric co-polymers form well-ordered lamellar coatings, while asymmetric ones lead to advanced patterning in the film. This response persists over a broad composition range of additional hydrophobic material. We also map the sensitivity of the results to polymer chemistry by variation of the interaction parameters. Finally, we show that the presence of excess free stabilizer in the coating solution can disrupt the homogeneity of the film, potentially deteriorating coating quality in practical applications. The findings stress the importance of block compositions and component concentrations as fundamental means to tune surface coating films and their internal structure.

Thiol-Surface-Engineered Cellulose Nanocrystals in Favor of Copper Ion Uptake.

Cellulose, the most abundant natural polymer on earth, has recently gained attention for a large spectrum of applications. At a nanoscale, nanocelluloses (mainly involving cellulose nanocrystals or cellulose nanofibrils) possess many predominant features, such as highly thermal and mechanical stability, renewability, biodegradability and non-toxicity. More importantly, the surface modification of such nanocelluloses can be efficiently obtained based on the native surface hydroxyl groups, acting as metal ions chelators. Taking into account this fact, in the present work, the sequential process involving chemical hydrolysis of cellulose and autocatalytic esterification using thioglycolic acid was performed to obtain thiol-functionalized cellulose nanocrystals. The change in chemical compositions was attributed to thiol-functionalized groups and explored via the degree of substitution using a back titration method, X-ray powder diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis. Cellulose nanocrystals were spherical in shape and ca. 50 nm in diameter as observed via transmission electron microscopy. The adsorption behavior of such a nanomaterial toward divalent copper ions from an aqueous solution was also assessed via isotherm and kinetic studies, elucidating a chemisorption mechanism (ion exchange, metal chelation and electrostatic force) and processing its operational parameters. In contrast to an inactive configure of unmodified cellulose, the maximum adsorption capacity of thiol-functionalized cellulose nanocrystals toward divalent copper ions from an aqueous solution was 4.244 mg g-1 at a pH of 5 and at room temperature.

Reinforcement Behavior of Chemically Unmodified Cellulose Nanofiber in Natural Rubber Nanocomposites.

We investigated the reinforcement behavior of small amounts of chemically unmodified cellulose nanofiber (CNF) in eco-friendly natural rubber (NR) nanocomposites. For this purpose, NR nanocomposites filled with 1, 3, and 5 parts per hundred rubber (phr) of cellulose nanofiber (CNF) were prepared by a latex mixing method. By using TEM, a tensile test, DMA, WAXD, a bound rubber test, and gel content measurements, the effect of CNF concentration on the structure-property relationship and reinforcing mechanism of the CNF/NR nanocomposite was revealed. Increasing the content of CNF resulted in decreased dispersibility of the nanofiber in the NR matrix. It was found that the stress upturn in the stress-strain curves was remarkably enhanced when the NR was combined with 1-3 phr CNF, and a noticeable increase in tensile strength (an approximately 122% increase in tensile strength over that of NR) was observed without sacrificing the flexibility of the NR in the NR filled with 1 phr CNF, though no acceleration in their strain-induced crystallization was observed. Since the NR chains were not inserted in the uniformly dispersed CNF bundles, the reinforcement behavior by the small content of CNF might be attributed to the shear stress transfer at the CNF/NR interface through the interfacial interaction (i.e., physical entanglement) between the nano-dispersed CNFs and the NR chains. However, at a higher CNF filling content (5 phr), the CNFs formed micron-sized aggregates in the NR matrix, which significantly induced the local stress concentration and promoted strain-induced crystallization, causing a substantially increased modulus but reduced the strain at the rupture of the NR.

Toughened Renewable Bio-polyester Blends Achieved through Crystallization Retardation by Acetylated Cellulose Fibers

Acetylation was explored as a technique to make cellulose fibers more compatible within a poly(lactic acid)/poly(3-hydroxybutyrate) polymer matrix. Acetylation was performed to degrees of substitutions 1.74, 2.52, and 2.8, and fibers were used in loadings from 0–20% by weight. Results showed no tensile strength improvements due to poor dispersion and fiber size reduction with fiber addition, but there were increases in modulus in the non-acetylated fiber sample and fully acetylated [degree of substitution (DS) 2.8] fiber samples. Composites containing modified fibers showed an increase in strain at break by as much as 200% at low loading levels. Acetylated cellulose acted as a nucleation retardant, while unmodified cellulose fibers acted as a nucleating agent. Results indicated the importance of fiber size, fiber, dispersion, and fiber–polymer interactions for final properties. Acetylated fiber reinforcement showed some promise for increasing maximum strain and compatibility of composites, which could allow for future investigations into filler chemistry–final property relationships, especially in applications like 3D printing where increased toughness is desired for some polymers.