Nanocrystalline Cellulose Samples Research Articles

Isolation and Production of Nanocrystalline Cellulose from Conocarpus Fiber.

Conocarpus fiber is a lignocellulosic biomass rich in cellulose potentially used for producing nanocrystalline cellulose (NCC), a biomaterial extensively employed in various application fields. In the present work, different hydrolysis times of 10, 20 and 30 min were applied to chemically pre-treated Conocarpus fiber to produce CPNC1, CPNC2, and CPNC3 particles. With acid hydrolysis treatment, the yield of NCC product was successfully retained at 17–19%. Individual, rod-like shapes of NCC particles could be clearly observed under microscopy examination. From chemical composition analysis, a relatively pure cellulose compartment was produced for all NCC samples with substantial removal of lignin and hemicellulose. The physicochemical analysis proved that each nanoparticle sample possessed strong cellulose crystalline structure. For thermal analyses, the heat resistance of NCCs was gradually enhanced with the increased hydrolysis times. Therefore, the extracted NCC product from Conocarpus fiber could be a green nano-filler for developing nanocomposite material in the future.

Dispersibility of Nanocrystalline Cellulose in Organic Solvents

Aqueous suspensions of nanocrystalline cellulose (NCC) were obtained by sulfuric acid hydrolysis using the standard procedure. Suspensions, films, and aerogel of NCC were characterized by various methods: the degree of polymerization was determined, elemental analysis was carried out, the degree of crystallinity and crystallite size were calculated on the basis of X-ray data, and the morphology of NCC aerogels was studied using scanning electron microscopy. The particle size of the NCC was determined using a transmission electron microscope, a scanning atomic force microscope, and the method of dynamic light scattering. NCC hydrosols with different pH were used to prepare lyophilized NCC samples. From NCC hydrosols with pH 2.2, by gradual replacement of water with an organic solvent, NCC organogels with acetone, acetonitrile, and ethanol were obtained. The dispersion of lyophilized NCC and NCC organogels (acetone, acetonitrile, and ethanol) in water and in 11 organic solvents was investigated. The effect of the pH of the initial aqueous suspension of the NCC and the solvent forming the NCC organogel on the repeated dispersibility of the NCC is shown. The optimum pH value of the initial aqueous suspension of NCC was determined, which determines the maximum dispersibility of the lyophilized samples in each specific solvent. Acetone, acetonitrile, and ethanol organogels are dispersed in most of the solvents studied with the formation of particles less than 100 nm in diameter.

A comprehensive characterization of ice nucleation by three different types of cellulose particles immersed in water

Abstract. We present the laboratory results of immersion freezing efficiencies of cellulose particles at supercooled temperature (T) conditions. Three types of chemically homogeneous cellulose samples are used as surrogates that represent supermicron and submicron ice-nucleating plant structural polymers. These samples include microcrystalline cellulose (MCC), fibrous cellulose (FC) and nanocrystalline cellulose (NCC). Our immersion freezing dataset includes data from various ice nucleation measurement techniques available at 17 different institutions, including nine dry dispersion and 11 aqueous suspension techniques. With a total of 20 methods, we performed systematic accuracy and precision analysis of measurements from all 20 measurement techniques by evaluating T-binned (1 ∘C) data over a wide T range (−36 ∘C <T<-4 ∘C). Specifically, we intercompared the geometric surface area-based ice nucleation active surface site (INAS) density data derived from our measurements as a function of T, ns,geo(T). Additionally, we also compared the ns,geo(T) values and the freezing spectral slope parameter (Δlog(ns,geo)/ΔT) from our measurements to previous literature results. Results show all three cellulose materials are reasonably ice active. The freezing efficiencies of NCC samples agree reasonably well, whereas the diversity for the other two samples spans ≈ 10 ∘C. Despite given uncertainties within each instrument technique, the overall trend of the ns,geo(T) spectrum traced by the T-binned average of measurements suggests that predominantly supermicron-sized cellulose particles (MCC and FC) generally act as more efficient ice-nucleating particles (INPs) than NCC with about 1 order of magnitude higher ns,geo(T).

DISPERSIBILITY OF NANOCRYSTALLINE CELLULOSE IN ORGANIC SOLVENTS

Aqueous suspensions of nanocrystalline cellulose (NCC) were obtained by sulfuric acid hydrolysis using the standard procedure. Suspensions, films and airgel of NCC were characterized by various methods: the degree of polymerization was determined, elemental analysis was carried out, the degree of crystallinity and crystallite size were calculated on the basis of X-ray data, the morphology of NCC aerogels was studied using scanning electron microscopy. The particle size of the NCC was determined using a transmission electron microscope, a scanning atomic-force microscope and the method of dynamic light scattering. NFC hydrosols with different pH were used to prepare lyophilized NCC samples. From NCC hydrosols with pH 2.2, by gradual replacement of water with an organic solvent, NCC organogels with acetone, acetonitrile and ethanol were obtained.
 The process of dispersion of lyophilized NCC and NCC organogels (acetone, acetonitrile and ethanol) in water and in 11 organic solvents was investigated. The effect of the pH of the initial aqueous suspension of the NCC and the solvent forming the NCC organogel on the repeated dispersibility of the NCC is shown. The optimum pH value of the initial aqueous suspension of NCC was determined, which determines the maximum dispersibility of the lyophilized samples in each specific solvent. It was shown that dispersion of acetone, acetonitrile and ethanol organogels in most of the solvents studied occurs with the formation of particles less than 100 nm.

A design optimization study on synthesized nanocrystalline cellulose, evaluation and surface modification as a potential biomaterial for prospective biomedical applications

In the present study, nanocrystalline cellulose (NCC) was prepared via acid hydrolysis and synthesis parameters were optimized via response surface modelling with a determined maximum NCC yield of 43.8%. The optimized NCC sample was subsequently surface modified via epichlorohydrin-mediated amination forming aminated nanocrystalline cellulose (A-NCC) with an amine content calculated as 1500μmol/g. The average particle size and zeta potential were determined 100nm and 325nm for NCC and A-NCC, respectively. Structural properties were analyzed by FTIR, TEM and XRD techniques. The obtained A-NCC as final product depicted a pKa value of 10.86±0.07 demonstrating favourable protonation of amine groups at physiological pH allowing the material to be suitable for prospective application in drug delivery and tissue engineering.

Extraction of Cellulose Nanocrystals with Structure I and II and Their Applications for Reduction of Graphene Oxide and Nanocomposite Elaboration

The aim of the present study is to investigate the effect of the hydrolysis process on the properties of nanocrystalline cellulose (NCC) isolated from different precursors and the subsequent use of the extracted NCC for the reduction of graphene oxide (GO). The raw materials (almond and peanut shells) chosen for the isolation of cellulose were selected on the basis of their abundance and their poorly investigation in the production of NCC. Microcrystalline cellulose (MCC) was firstly extracted by alkali and bleaching treatments, then hydrolyzed under different processes to produce NCC polymorphs with structure I (NCC-I) and NCC structure II (NCC-II). The Fourier transform infrared spectroscopy, the X-ray diffraction (XRD) and the 13C NMR studies of the alkali and bleached products confirmed the formation of cellulose type I with high purity and good crystallinity, while scanning electron microscopy (SEM) showed micrometric fibers with lengths reaching 80 µm. Sulfuric acid treatment of these microfibers results in NCC type I or II, depending on the hydrolysis process. SEM of the NCC samples exhibited nanorods with diameter and aspect ratio in the range of 20–40 and 20–25 nm, respectively. Thermogravimetric analysis (TGA) of the MCC and NCC products indicated stable materials with a degradation temperature reaching 240 and 200 °C for MCC and NCC, respectively. The other part of our work concerns the use of the obtained cellulose nanocrystals (type II) for the preparation of reduced graphene oxide composite (NCC/RGO), to demonstrate the reducing properties of the isolated NCCII.

The effect of nanocrystalline cellulose on flow properties of fiber crop aqueous suspension

Nanocrystalline cellulose (NCC) a nature-based material, has gained significant attentions for its unique properties. The present study aims to investigate the flow behavior of cellulosic suspension containing non-wood pulp fibers and NCC, by means of rheological and pressure drop measurements. The NCC sample was prepared by sulfuric acid hydrolysis from Acacia mangium fibers. The rheological properties of kenaf/NCC suspensions were studied using viscosity and yield stress measurements. The pressure drop properties of the suspension flow were studied with respect to variation in flow velocity (0.4 m/s–3.6 m/s) and the NCC concentration (70 mg/l and 150 mg/l). The pressure drop results showed that the pulp suspension containing 150 mg/l NCC had higher drag reduction than kenaf suspension alone. The present insights into the flow of pulp/NCC suspension provide a new data and promote the application of NCC in industries.

Nanocrystalline cellulose isolated from discarded cigarette filters

We report the isolation of nanocrystalline cellulose (NCC) produced from discarded cigarette filters (DCF). The DCF were processed into cellulose via ethanolic extraction, hypochlorite bleaching, alkaline deacetylation, and then converted into NCC by sulfuric acid hydrolysis. The morphological structures of the isolated NCC established with TEM showed that the nanocrystals were needle-like with a mean length of 143nm. FEGSEM showed the morphological transition of the micro-sized DCF to self-assembled NCC while EDX revealed the presence of Ti (as TiO2) in DCF, which was retained in the NCC. A NCC sample was freeze-dried and showed a specific surface area of 7.78m2/g. The crystallinity of the NCC film and freeze-dried samples were 96.77% and 94.47%, respectively. Crystallite sizes of the freeze-dried (8.4nm) and film (7.6nm) samples correlated with the mean width (8.3nm) of the NCC observed under TEM.

Isolation and Characterization of Nanocrystalline Cellulose from Totally Chlorine Free Oil Palm Empty Fruit Bunch Pulp

Nanocrystalline cellulose (NCC) was isolated from a totally chlorine free (TCF) bleached oil palm empty fruit bunch (OPEFB) pulp via acid hydrolysis using a 58 % sulfuric acid concentration and ultrasonic treatment. The effects of acid concentration and hydrolysis time were investigated. Characterization of OPEFB–NCC was carried out using TEM, FTIR, 13C-NMR, XRD, zeta potential and TGA. The optimal hydrolysis time was 80 min as indicated by the leveling off of the OPEFB–NCC dimensions (length 150 nm and diameter 6.5 nm) with no significant loss of crystallinity at this point. The presence of a shoulder peak at 1231 cm−1 (assigned to a sulfate group) in the FTIR spectrum of NCC is indicative of a successful esterification. This is further corroborated by the 13C-NMR analysis whereby the distinct C4 amorphous and crystalline peaks present in OPEFB–TCF pulp had almost disappeared and the cluster of signals for C2, C3, C5, and a well separated signal of C6 had merged into one single peak in the OPEFB–NCC sample. These observations allude to most of the amorphous region having been removed and to the strong possibility of sulfonation having not only occurred on the C6, but also on C2 and C3. OPEFB–NCC isolated over shorter hydrolysis time was more thermally stable; however, the char fraction decreases with hydrolysis time despite having a higher zeta potential. The results of this investigation demonstrate that NCC can be produced from pulp made by chlorine free environmentally benign processes with ensuing savings in energy and chemicals.

Catalytic Isolation and Physicochemical Properties of Nanocrystalline Cellulose (NCC) using HCl-FeCl3 System Combined with Ultrasonication

This research emphasizes the isolation of nanocrystalline cellulose (NCC) from palm tree cellulose (PTC) and α-cellulose (AC), using acidic FeCl3-assisted catalytic pretreatment coupled with ultrasonication. The cavitation effect of ultrasonication affects the microstructure of the fibers, ultimately enhancing the crystallinity index of the prepared nanocrystalline cellulose (NCC) sample. In this research, Fourier transform infrared spectroscopy (FTIR) was used to identify the specific functional groups on both types of NCC sample. X-ray diffraction (XRD) analysis demonstrated that the isolated NCC from PTC and AC showed a higher crystallinity index of 73.51% and 89.03%, with diameters of 20 to 70 nm and 15 to 50 nm, respectively. The change in surface morphological features was observed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopic (TEM) analysis. It was observed that PTC-based NCC had higher thermal stability than the starting cellulosic sample, whereas NCC isolated from AC showed an opposite trend of reduced thermal stability relative to the raw sample. The results indicated that catalytic acid hydrolysis with ultrasonication was able to yield up to 80.88% and 81.20% of NCC from PTC and AC, respectively, which is comparatively high enough for economic viability of the process.

Green preparation and characterization of size-controlled nanocrystalline cellulose via ultrasonic-assisted enzymatic hydrolysis

Cellulose is the most abundant biopolymer on earth and the main component of crop by-products, but its development is inadequate. Preparation and application of nanocrystalline cellulose (NCC) are drawing much attention from both the academia and the industry because of its unique and exceptional physicochemical properties. For the first time, rod-like NCC was successfully prepared through an environmentally friendly ultrasonic-assisted enzymatic hydrolysis process from wheat microcrystalline cellulose. NCC yield reached 22.57% under the optimal condition of hydrolysis time of 120h combined with ultrasonic treatment of 10 times each for 60min, whereas the NCC yield was only 15.76% in the absence of ultrasonic treatment. Images of transmission electron microscopy showed that the NCC samples exhibited a rod-like structure with a width of less than 10nm and a length of 200–500nm, 100–200nm, and 40–50nm when the ultrasonic treatment was 0, 30, and 60min, respectively. Dynamic light scattering analysis demonstrated that as-obtained NCC exhibited a smaller value in particle size than that prepared in the absence of ultrasonic treatment. X-ray diffraction results revealed that the NCC sample exhibited higher crystallinity as ultrasonic time increased. NCC fabricated by this facile, safe, and eco-friendly ultrasonic-assisted enzymolysis method can have great potential in applications in bionanocomposites, drug delivery, agriculture, and cosmetic industry.

Preparation and Characterization of Dialdehyde Nanocellulose

Dialdehyde nanocellulose (DANC) was prepared by periodate selective oxidation of secondary hydroxyl group of nanocrystalline cellulose (NCC). NCC and DANC samples were characterized by FT-IR, XRD and conductimetric titration. Aldehyde groups were introduced during the process of sodium periodate oxidation, which was confirmed by the FT-IR spectra. The aldehyde group content increased with the increase of sodium periodate. The crystallinity index (CrI) and crystallite size of the samples were continuously decreased with the increase of the oxidant.

Preparation and characterization of nanocrystalline cellulose via low-intensity ultrasonic-assisted sulfuric acid hydrolysis

Nanocrystalline cellulose (NCC) was extracted from microcrystalline cellulose via low-intensity ultrasonic-assisted sulfuric acid hydrolysis process. NCC samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size distribution (PSD) analysis, Fourier-transformed infrared spectra (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and rheological measurement. It was found that NCC yield reached 40.4 % under the optimum process of low-intensity ultrasonic-assisted sulfuric acid hydrolysis, while it was only 33.0 % in the absence of ultrasonic treatment. Furthermore, the results showed that the two NCC samples obtained from ultrasonic-assisted hydrolysis and conventional hydrolysis were very similar in morphology, both exhibiting rod-like structures with widths and lengths of 10–20 and 50–150 nm, respectively. XRD result revealed that the NCC sample from ultrasonic-assisted hydrolysis contained a small amount of cellulose II and possessed a Segal Crystallinity Index of 90.38 % and a crystallite size of 58.99 A, higher than those of the NCC sample from conventional hydrolysis. Moreover, PSD analysis demonstrated that the former exhibited a smaller value in average particle size than the latter. In addition, rheological measurements showed that the NCC suspensions from the ultrasonic-assisted process exhibited a lower viscosity over the range of shear rate from 0.1 to 100 s−1 in comparison with that prepared in the absence of ultrasonic treatment.

Ageing, yielding, and rheology of nanocrystalline cellulose suspensions

This paper investigates yielding and flow of nanocrystalline cellulose (NCC) suspensions by combining rheological measurements with light scattering echo (LS-echo). The NCC samples are characterized using static and dynamic light scattering as well as polarized optical microscopy coupled with a rotational rheometer. The storage modulus of the NCC suspensions is found to increase with waiting time after shear rejuvenation. The microscopic particle rearrangements of the NCC spindles are followed by LS-echo at both short and long waiting times under oscillatory shear flow. We find that the onset of shear-induced irreversible microscopic particle rearrangements, coincide with the strain at which storage and loss moduli cross over in the nonlinear viscoelastic regime identified by the macroscopic yield point of the sample. The yielding transition is found to occur at a higher strain as the frequency of oscillation increases.

New insights into nano-crystalline cellulose structure and morphology based on solid-state NMR

The phase structure of nanocrystalline cellulose (NCC) is studied with solid-state NMR experiments on NCC samples subjected to 2H/1H exchange in order to label regions accessible to water. These novel results show partial but similar exchange in portions of the 13C spectrum previously assigned to both highly crystalline and disordered/surface cellulose. Exchange in liquid D2O occurs rapidly, faster than the time-scale required to dry the samples, while exposure to D2O vapor reveals a single time constant of ∼30 h to build up to the liquid exposed exchange level. In both cases ca. 37 % of the expected exchangeable sites are found to contain 2H. These results, along with those from relaxation experiments requiring multi-component or stretched-exponential fits, together with X-ray diffraction results suggest the NCC particles contain distributions of environments distinguished by their structures and crystalline perfection. The incomplete exchange of the disordered/surface regions suggests that the NCC crystallites contain abundant disordered domains in their interiors that are protected from exchange. Preliminary 31P/13C REDOR experiments on phosphoric-acid hydrolyzed NCC samples provide a 13C spectrum of accessible surface sites, but are of relatively low signal-to-noise. These experiments suggest a phosphate coverage of 2.6 per 100 anhydroglucose monomers, similar to sulfate coverage measured previously for sulfuric acid hydrolyzed samples.

An ecotoxicological characterization of nanocrystalline cellulose (NCC)

The pulp and paper industry in Canada is developing technology for the production and use of nanocrystalline cellulose (NCC). A key component of the developmental work is an assessment of potential environmental risks. Towards this goal, NCC samples as well as carboxyl methyl cellulose (CMC), a surrogate of the parent cellulosic material, were subjected to an ecotoxicological evaluation. This involved toxicity tests with rainbow trout hepatocytes and nine aquatic species. The hepatocytes were most sensitive (EC20s between 10 and 200 mg/l) to NCC, although neither NCC nor CMC caused genotoxicity. In tests with the nine species, NCC affected the reproduction of the fathead minnow at (IC25) 0.29 g/l, but no other effects on endpoints such as survival and growth occurred in the other species at concentrations below 1 g/l, which was comparable to CMC. Based on this ecotoxicological characterization, NCC was found to have low toxicity potential and environmental risk.