Surface Of Nanocrystalline Cellulose Research Articles

Enhancing the mechanical properties of hydrogels with vinyl-functionalized nanocrystalline cellulose as a green crosslinker

Hydrogels have gained significant attention in scientific communities for their versatile applications, but several challenges need to be addressed to exploit their potential fully. Conventional hydrogels suffer from poor mechanical strength, limiting their use in many applications. Moreover, the crosslinking agents used to produce them are often toxic, carcinogenic, and not bio-friendly. This study presents a novel approach to overcome these limitations by using bio-friendly modified nanocrystalline cellulose as a crosslinker to prepare highly stretchable and tough thermosensitive hydrogels. The surface of nanocrystalline cellulose was modified with 3-methacryloxypropyltrimethoxysilane (MPTS) to obtain modified nanocrystalline cellulose (M-NCC) crosslinker and used during free radical polymerization of thermosensitive N-isopropyl acrylamide (NIPA) monomer to synthesize NIPA/M-NCC hydrogel. The resulting nanocomposite hydrogels exhibit superior mechanical, thermal, and temperature-responsive swelling properties compared to conventional hydrogels prepared with traditional bi-functional N, N′-methylene bis (acrylamide) (MBA) as a crosslinker. The elongation at break, tensile strength, and toughness of the NIPA/M-NCC hydrogels significantly increase and Young’s modulus decrease than conventional hydrogel. The designed M-NCC crosslinker could be utilized to improve the mechanical strength of any polymeric elastomer or hydrogel systems produced through chain polymerization.

A bio-plastic composite film based on nanocrystalline cellulose-zinc oxide reinforced poly (lactic acid) with enhanced UV-shielding effect and antibacterial activity for food packaging applications

This work reports the properties of composite films based on biodegradable poly (lactic acid) (PLA) incorporated with nanocrystalline cellulose (NCC) and nanocrystalline cellulose coated with zinc oxide (NCC-ZnO). The NCC was prepared from microcrystalline cellulose (MCC) by an acidolysis technique, and subsequently used as a supporting core for ZnO deposition via a hydrothermal process. The NCC and NCC-ZnO were characterized by various techniques, i.e., TEM, SEM, FTIR, XRD, and TGA. The results confirmed the successful fabrication of the NCC-ZnO, with approximately 41% weight of ZnO coated on the NCC surface. Both NCC and NCC-ZnO were later incorporated into PLA at various contents, and their properties, i.e., tensile properties, ultraviolet (UV) shielding efficacy, and antibacterial activity, were investigated. Compared with NCC, NCC-ZnO exhibited higher reinforcement because it provided greater tensile strength and Young’s modulus at the same filler content. The addition of NCC-ZnO significantly improved the UV shielding efficacy (both UV-A and UV-B) and the antibacterial activity. The results reveal the potential of using NCC-ZnO as an alternative filler in active food packaging applications for enhanced performance.

Characterization of magnetic bio-nanocomposites of nanocrystalline cellulose (NCC) coated on paper surface

Effects of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidation were evaluated for magnetic bio-nanocomposites of nanocrystalline cellulose (NCC). The magnetic bio-nanocomposites were prepared using NCC and nanomagnetite (NM) to produce organic compounds. The NCC was oxidized by sodium bromide (NaBr), sodium hypochlorite (NaOCl), and TEMPO. The oxidized NCC (ONCC) was characterized by Fourier-transform infrared spectroscopy (FTIR) and conductometry. The bio-nanocomposite particles from the NCC and the ONCC were prepared via in situ precipitation of iron salts from alkaline solution. The resultant bio-nanocomposites were coated on the surface of kraft paper. The magnetic bio-nanocomposite and coated papers were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). The results revealed that the carboxyl groups were introduced successfully on the NCC surface. The bio-nanocomposite particles showed good dispersion in the surface of the papers. The saturation magnetizations of the coated papers with magnetic bio-nanocomposites of NCC and ONCC were 10.9 and 14.57 emu/g, respectively. The magnetic coated papers exhibited a superparamagnetic behavior. The strengths, apparent density, and air resistance of the coated paper with the ONCC bio-nanocomposites increased in comparison to the NCC coated sample, while the water absorption diminished due to the TEMPO-oxidation.

Nanocomposites of polyhydroxyurethane with nanocrystalline cellulose: Synthesis, thermomechanical and reprocessing properties

A commercial novolac epoxide was used to react with carbon dioxide (CO2), to obtain a novel five-membered cyclic carbonate. This novel novolac epoxide-based five-membered cyclic carbonate (NE5CC) was successfully utilized to prepare polyhydroxyurethane (PHU) thermoset. To improve the thermomechanical properties of the PHU thermoset, nanocrystalline cellulose (NCC) was used as the modifier. To facilitate dispersion of the modifier, the surface of NCC was functionalized with poly(N-vinylpyrrolidone) (PVPy). The functionalized NCC (NCC-PVPy) was prepared via the surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of N-vinylpyrrolidone (NVP). It was found that NCC-PVPy was readily dispersed in PHU matrix in the form of single nanocrystals. The nanocomposites of PHU with NCC displayed the enhanced glass transition temperatures and improved mechanical properties. In the meantime, the nanocomposites had good shape recovery properties; the nanocomposites can be reprocessed at elevated temperature. The reprocessing properties can be utilized to reprogram the original shapes of the shape memory nanocomposites.

Cationically Modified Nanocrystalline Cellulose/Carboxyl-Functionalized Graphene Quantum Dots Nanocomposite Thin Film: Characterization and Potential Sensing Application

In this study, highly functional cationically modified nanocrystalline cellulose (NCC)/carboxyl-functionalized graphene quantum dots (CGQD) has been described. The surface of NCC was first modified with hexadecyltrimethylammonium bromide (CTA) before combining with CGQD. The CGQD, CTA-NCC and CTA-NCC/CGQD nanocomposites thin films were prepared using spin coating technique. The obtained nanocomposite thin films were then characterized by using the Fourier transform infrared spectroscopy (FTIR) which confirmed the existence of hydroxyl groups, carboxyl groups and alkyl groups in CTA-NCC/CGQD. The optical properties of the thin films were characterized using UV–Vis spectroscopy. The absorption of CTA-NCC/CGQD was high with an optical band gap of 4.127 eV. On the other hand, the CTA-NCC/CGQD nanocomposite thin film showed positive responses towards glucose solution of different concentration using an optical method based on surface plasmon resonance phenomenon. This work suggests that the novel nanocomposite thin film has potential for a sensing application in glucose detection.

Study of plant and tunicate based nanocrystalline cellulose in hybrid polymeric nanocomposites

Nanocrystalline cellulose (NCC) is a sustainable and renewable nanomaterial which can be defined as the nanoscale crystalline region of cellulose fibrils. The present work describes polyvinyl alcohol (PVA) based nanocomposite materials containing reinforcing low aspect ratio NCC sourced from plants and high aspect ratio NCC from a local invasive tunicate species. The effect of size and surface chemistry of the NCC reinforcement on the mechanical, thermal and morphological properties of PVA based nanocomposites is studied. Hybrid nanocomposites which contain both plant and tunicate sourced NCC within the PVA matrix are also documented. To our best knowledge, this represents the first known study describing the effect of NCC with varying size and surface chemistry combined within PVA to form hybrid PVA–NCC nanocomposites. In all cases, increasing mechanical reinforcement is observed as NCC content is increased, which varies in magnitude with NCC aspect ratio and surface chemistry. A notable improvement in thermal stability is also observed in all nanocomposites when NCC content is increased. Precursor materials and the resulting nanocomposites are well characterized by transmission electron microscopy, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, elemental analysis and powder X-ray diffraction.

Effect of nanocrystalline cellulose and zinc oxide hybrid organic–inorganic nanofiller on the physical properties of polycaprolactone nanocomposite films

New biobased polycaprolactone (PCL) nanocomposite materials were prepared using cellulose-zinc oxide (NCC-ZnO) as an organic–inorganic nanofiller which was prepared by loading zinc oxide (ZnO) onto the surface of nanocrystalline cellulose (NCC). Various loadings (2–8 wt%) of nanofiller were added onto the PCL matrix to prepare PCL/NCC-ZnO nanocomposite films using the solvent cast method. The nanofiller and nanocomposite films were characterised by AFM, TEM, FTIR, FE-SEM, XRD, DSC, TGA and tensile strength. The results of AFM, TEM and FTIR analysis confirmed the interaction between NCC and ZnO nanoparticles and between nanofiller (NCC-ZnO) and PCL. The mechanical properties of the PCL polymer significantly improved due to incorporation of the nanofiller, especially, when increasing the amount of nanofiller beyond 4 wt%. FE-SEM analysis showed homogenous dispersion of nanofiller within the PCL matrix, and illustrated a rough porous surface. Both TGA and DSC results indicated that the thermal stability of PCL increased due to the incorporation of nanofillers.

Polymeric Composites with Embedded Nanocrystalline Cellulose for the Removal of Iron(II) from Contaminated Water.

The exponential increase in heavy metal usage for industrial applications has led to the limited supply of clean water for human needs. Iron is one of the examples of heavy metals, which is responsible for an unpleasant taste of water and its discoloration, and is also associated with elevated health risks if it persists in drinking water for a prolonged period of time. The adsorption of a soluble form of iron (Fe2+) from water resources is generally accomplished in the presence of natural or synthetic polymers or nanoparticles, followed by their filtration from treated water. The self-assembly of these colloidal carriers into macroarchitectures can help in achieving the facile removal of metal-chelated materials from treated water and hence can reduce the cost and improve the efficiency of the water purification process. In this study, we aim to develop a facile one-pot strategy for the synthesis of polymeric composites with embedded nanocrystalline cellulose (NCC) for the chelation of iron(II) from contaminated water. The synthesis of the polymeric composites with embedded nanoparticles was achieved by the facile coating of ionic monomers on the surface of NCC, followed by their polymerization, crosslinking, and self-assembly in the form of three-dimensional architectures at room temperature. The composites prepared were analyzed for their physiochemical properties, antifouling properties, and for their iron(II)-chelation efficacies in vitro. The results indicate that the embedded-NCC polymeric composites have antifouling properties and exhibit superior iron(II)-chelation properties at both acidic and basic conditions.

Modification of NanoCrystalline Cellulose (NCC) by Hyperbranched Polymer

Objectives: The surface modification of NanoCrystalline Cellulose (NCC) recently has been paid attention due to the increasing opportunities in the application. The objective of this paper is to modify the surface of NCC by the HyperBranched Polymer (HBP) with hydroxyl terminal groups ends. Methods/Statistical Analysis: The NCC surfaces were modified with HBP using solvent evaporation methods. First, the NCC was synthesized via ultrasound assisted acid hydrolysis process and the obtained NCC was surface coated by using HBP with different concentration through solvent evaporation technique. Finally, the obtained NCC and Modified NCC were characterized by using FTIR, XRD and TGA. Findings: Results revealed that there are significant differences of FTIR pattern analysis indicated that the NCC has been modified, however the modification NCC with HBP under various conditions did not change the X-ray patterns of NCC which indicates that the HBP only coated on the surface of NCC. Application/Improvements: This modification of NCC showed promising results which can be used for various applications.

Preparation of Colloidal Properties and Water Dispersible Conductive Polypyrrole Nanocomposite of Nanocrystalline Cellulose

The development of conductive polypyrrole (PPY) processability was successfully achieved by a synthesis of colloidal form with high dispersion stability in aqueous medium. In-situ polymerization method of pyrrole monomers (PY) assisted by aqueous suspension nanocrystalline cellulose (NCC) and the oxidizing agent ammonium persulfate (APS). Facial and fast technique consisted of deposition of PY monomers on the NCC surface via electrostatic attractions between the sulfate groups in NCC surface and the amine group of the PY. Steric hindrance feature of NCC suspension significantly influences the colloid production. The nanocomposite of PPY and NCC (PPY-NCC), purified by centrifuge repeatedly and desiccated by freeze-dry technique. The observations of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), clearly shows the nanostructure modification for nanocomposite and the NCC particles after the composition. The PPY-NCC nanocomposite have very good dispersion stability in aqueous media. The variation between PPY and PPY-NCC in the crystallinity and thermal stability was studied by thermogravimetric analysis (TGA) and x-ray diffraction (XRD) respectively.

Hydrolytic activities of artificial nanocellulose synthesized via phosphorylase-catalyzed enzymatic reactions

Nature-based nanocelluloses with the cellulose I allomorph are attractive one-dimensional nanomaterials because of their mass productivity and unique physicochemical properties. Our previous studies demonstrated that the activated ester, monophosphate and amide linkages of small organic substrates were hydrolyzed on the surface of nanocrystalline cellulose (NCC), which is a nature-based nanocellulose. However, fundamental knowledge of the hydrolytic activities of nanocelluloses is limited. In this study, artificial sheet-like nanocelluloses composed of cellulose oligomers with the cellulose II allomorph were synthesized by phosphorylase-catalyzed enzymatic reactions, and their hydrolytic activities against ester substrates were characterized. The as-prepared nanocelluloses exhibited relatively low hydrolytic activities. However, distorted and smaller nanocelluloses with larger surface areas, which were prepared by sonication-based mechanical treatment of the as-prepared nanocelluloses, exhibited significantly greater hydrolytic activities. These enzymatically synthesized artificial nanocelluloses exhibited hydrolytic activities, even though the molecular weights of the component cellulose, allomorphs, and morphologies were different from those of nature-based NCC. Artificial sheet-like nanocelluloses composed of cellulose oligomers with the cellulose II allomorph were synthesized by phosphorylase-catalyzed enzymatic reactions, and their hydrolytic activities against ester substrates were characterized. The as-prepared nanocelluloses exhibited relatively low hydrolytic activities. However, distorted and smaller nanocelluloses with larger surface areas, which were prepared by sonication-based mechanical treatment of the as-prepared nanocelluloses, exhibited significantly greater hydrolytic activities.

Modification of nanocrystalline cellulose for application as a reinforcing nanofiller in PMMA composites

Nanocrystalline cellulose (NCC) with particle length of 100–500 nm was prepared from microcrystalline cellulose and modified with a reversible addition–fragmentation chain transfer (RAFT) agent, i.e., 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPADB). From the surface of CPADB-modified NCC, methyl methacrylate (MMA) was grafted to produce poly(methyl methacrylate) (PMMA)-modified NCC. Unmodified NCC, CPADB-modified NCC, and PMMA-modified NCC were further used as reinforcing nanofillers in PMMA composite plates prepared by bulk polymerization of MMA. Regardless of NCC type, the PMMA plates were transparent to visible light at low NCC concentrations but became translucent with increasing NCC concentration. At given NCC concentration, the visible-light transparency of the PMMA/NCC composites decreased in the order PMMA-modified NCC, CPADB-modified NCC, unmodified NCC. PMMA-modified NCC and CPADB-modified NCC showed moderate potential for reinforcing the PMMA matrix, while unmodified NCC detrimentally affected the mechanical properties of the PMMA composites due to more pronounced particle aggregation.

Characterization of Surface Acetylated Nanocrystalline Cellulose by Single-Step Method

Surface acetylated nanocrystalline cellulose (NCC) was prepared from cotton fiber by a single-step method under mild conditions using anhydrous phosphoric acid as the solvent. The absorbance peak of O-H was reduced, and the absorbance peaks of C=O and CH3 appeared in the Fourier transform infrared (FTIR) spectrum of the acetylated NCC with respect to that of the unmodified NCC. The roughly estimated degree of substitution was a little greater than 1.5 by FTIR analyses, implying that most of the free hydroxyl groups on the NCC surface were acetylated at 40 °C for 3 h. The carbons of the acetyl groups were clearly identified in the 13C cross polarization-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) spectrum. The zeta potential was reduced from -32.12 mV to -20.57 mV after acetylation. Transmission electron microscope (TEM) and field-emission scanning electron microscope (FESEM) images showed that they were thread-like nano-crystals with a diameter less than 5 nm. Crystal structure analysis using X-ray diffraction (XRD) demonstrated that the acetylated NCC had the typical CelluloseⅡstructure. The PLA film reinforced with 3 wt% acetylated NCC content exhibited the highest tensile strength, which was increased by 117% compared to the control. SEM observation demonstrated good interfacial interaction between the acetylated NCC and the matrix.

Amine-decorated nanocrystalline cellulose surfaces: synthesis, characterization, and surface properties

In this present work, terminal amino-functionalized nanocrystalline cellulose derivatives were prepared using a simple two-step protecting group-free protocol under aqueous reaction conditions at room temperature. Carboxylate groups were first introduced onto the surface of nanocrystalline cellulose (NCC) via a TEMPO-mediated oxidation. Then, reaction of surface-carboxylated NCC with bifunctional amines of small alkyl chain length by EDC/NHS-mediated coupling furnished the desired aminated NCC via an amide linkage. Surface covalent functionalization was confirmed by Fourier transform infrared spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy. Size, surface charge, morphology, and thermal properties were obtained by various techniques. STEM images revealed no change in structure and morphology of the materials after TEMPO-mediated oxidation but a slight agglomeration was observed after surface covalent functionalization with diamines. While amide linkage confers stability, terminal primary amine groups on the surface of NCC represent a versatile reactive functional group for bioconjugation with other biomolecules for potential biomedical applications.

Effect of Surface Energy on Dispersion and Mechanical Properties of Polymer/Nanocrystalline Cellulose Nanocomposites

Dispersion quality and polymer-filler interaction are important factors in determining the final properties of polymer nanocomposites. Surface energy of nanocrystalline cellulose (NCC) and some polymers (polypropylene, PP, and polylactic acid, PLA) was measured at room and high temperatures. NCC had higher polarity and surface energy than PP and PLA at room temperature but had a lower surface energy at higher temperatures. The effect of surface modification with alkenyl succinic anhydride (ASA) on NCC surface energy at room and high temperature was studied. Total surface energy of NCC was lowered after surface modification. Thermodynamic work of adhesion for PP/NCC and PLA/NCC was lowered by NCC surface modification. A thermodynamic analysis is proposed to estimate the dispersion energy, based on surface energy measurements at room and high temperatures. Also, a dispersion factor is defined to provide a quantitative indication of the dispersibility of nanoparticles in a polymer matrix under various conditions. The required dispersion energy was reduced by lowering the interfacial tension. On the other hand, it increased as the quality of NCC dispersion (i.e., the nanoparticle surface area) in the system was improved. Surface modification of NCC with ASA had a negative effect on the compatibility between NCC and PLA, whereas it had a positive influence on compatibility between PP and NCC.

Preparation and Characterization of Waterborne Polyurethane Modified by Nanocrystalline Cellulose

Nanocrystalline cellulose (NCC) was used as a modifier for waterborne polyurethane (WPU) to investigate the water and ethanol resistance of WPU-NCC composites. The NCC surface was modified with γ-glycidoxypropyltrimethoxysilane (GPTMS) and γ-ammnonimpropylmethyldimethoxysilane (APMDS) to improve its compatibility with waterborne polyurethane (WPU), as indicated by the contact angle (CA). The characteristic properties of WPU modified by NCC and a control group were compared by a Fourier-transform infrared spectroscope (FTIR), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The CA between the modified NCC and WPU was decreased by 31.2% (with 8.0% APMDS (v/v)), and the NCC modified by GPTMS resulted in a 33.8% decrease of the CA. Compared to the original WPU, the crystal structure and crystallinity of the modified WPU showed a slight alteration. The SEM micrographs showed that the NCC particles modified by GPTMS were dispersed more uniformly. The FT-IR results showed that the addition of modified NCC led to the reduction of the characteristic absorption peak of the hydroxyl group. The water resistance of WPU with 1.5% NCC modified by GPTMS was increased by 47.2%, and the ethanol resistance decreased by 67.0%, while the modification from APMDS led to a 38.1% increase in water resistance and a 56.9% decrease in ethanol resistance.

IMPROVEMENTS OF MECHANICAL PROPERTIES AND SPECULAR GLOSS OF POLYURETHANE BY MODIFIED NANOCRYSTALLINE CELLULOSE

In this study, the optical and mechanical properties of polyurethane were improved by modified nanocrystalline cellulose (NCC). The surface of NCC was modified by 3-glycidoxypropyltrimethoxysilane (GPTMS) and 3-methacryloxy-propyltrimethoxysilane (MPS) to overcome the lack of compatibility with polyurethane. Polyurethane with modified NCC was characterized by wetting property, X-ray powder diffraction, and thermogravimetric analysis. The pencil hardness, specular gloss, and abrasion resistance of modified polyurethane were determined using the methods of Chinese National Standards GB/T 6739-2006, GB/T 9754-2007, and GB/T 1768-2006. The wetting property of NCC modified by GPTMS increased by 25.9%, and modification from MPS resulted in a 22.5% decrease of the contact angle. MPS-modified NCC affected the crystal structure and thermal stability of polyurethane more significantly than NCC modified by GPTMS. The pencil hardness of polyurethane was enhanced with 1.5% modified NCC. The specular gloss and abrasion resistance of modified polyurethane increased by 253.1% (1.0% NCC modified by GPTMS) and 59.4% (1.5% NCC modified by GPTMS), respectively. MPS-modified NCC led to the inconspicuous improvements.

Modification of NCC for Improving the Wetting Property with Polyurethane

In this study, different lipophilic groups from 3-aminpropyltriethoxysilane (APTES) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were used to alter the surface structure of nanocrystalline cellulose (NCC). The diversifications of NCC surface resulted from modifiers improved the wetting property between NCC and polyurethane significantly. The modified NCC was characterized by X-ray powder diffraction (XRD). And the wetting property was indicated by contact angle (CA). Epoxy groups from 6% GPTMS led to a 47.6% decline of CA, while the improvement of wetting property from APTES was inconspicuous.

Synthesis and characterization of cationically modified nanocrystalline cellulose

In this study, nanocrystalline cellulose (NCC) resulting from sulfuric acid hydrolysis of wood cellulose fiber, was rendered cationic by grafting with glycidyltrimethylammonium chloride (GTMAC). An optimization of the reaction parameters, such as water content, reactant mole ratio, and reaction media was performed. The presence of cationic GTMAC on the surface of NCC was confirmed by Fourier Transform Infrared Spectroscopy (FTIR). The cationically modified NCC was characterized by surface charge density, degree of substitution, ζ potential, and particle size. It was found that the cationic surface charge density of NCC can be increased by controlling the water content of the reaction system. Surface cationization of NCC led to an increase in the surface charge density over the un-modified NCC. The cationically modified NCC was well dispersed and stable in aqueous media due to enhanced cationic surface charge density. Transmission electron microscopy (TEM) images showed the improvement in state of dispersion of cationically modified NCC over the un-modified NCC. The optimum water content was found to be 36wt% for aqueous based media and 0.5 water to DMSO volume ratio for aqueous–organic solvent reaction media. The increased surface charge density of NCC also delayed the onset of gelation in aqueous system.

Modified nanocrystalline cellulose from two kinds of modifiers used for improving formaldehyde emission and bonding strength of urea-formaldehyde resin adhesive

In this study, nanocrystalline cellulose (NCC) was used for increasing the bonding strength of urea-formaldehyde (UF) resin adhesive, with a reduction of formaldehyde (HCHO) emissions. The surface of NCC was modified by 3-aminpropyltriethoxysilane (APTES) and 3-methacryloxypropyltrimethoxysilane (MPS) for the lack of compatibility with UF resin adhesive. The modified NCC was characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TG), and wetting property. HCHO emission and bonding strength of the UF resin adhesive with modified NCC were tested according to Chinese National Standards GB/T 17657-1999 and GB/T 9846-2004. The results of XRD, TG, and wetting property from NCC modified by APTES showed more significant improvements than that from NCC modified by MPS. The HCHO emission of UF resin adhesive with 1.5% NCC modified by APTES decreased by 53.2% and bonding strength increased by 23.6%, while the results from the NCC modified by MPS were 21.3% and 7.0%, respectively.