Cellulose Nanocrystals Content Research Articles

Improving tribological efficiency of isopropyl palmitate oil with cellulose nanocrystals: a sustainable approach for high-performance lubricants

AbstractThis article explores the potential of cellulose nanocrystals (CNCs) as a lubricant additive for isopropyl palmitate (IPP) oil to enhance its tribological performance. CNCs, derived from renewable sources, offer a sustainable and environmentally friendly alternative to traditional lubricant additives. A two-step method was used to prepare the nanolubricants, with visual control and dynamic light scattering measurements to assess their temporal stability. The viscous behavior of the nanolubricants, in terms of viscosity and viscosity index, was evaluated at different temperatures. The study assesses the effectiveness of CNC/IPP oil blends as lubricants through tribological tests, including evaluations under pure sliding and rolling–sliding conditions. Studies on worn surfaces were conducted using surface roughness analysis, Raman mapping, and XPS, and the thermal stability was examined to determine their suitability for different operating conditions. CNCs significantly reduce friction by up to 44% and improve wear resistance compared to the neat IPP base oil, presumably due to a self-repairing effect. Furthermore, an improvement of the thermal conductivity of pure IPP base oil has been revealed with increasing CNC concentration. This study enhances the understanding of cellulose nanocrystals as lubricant additives and their potential to transform traditional lubricating oils into high-performance and sustainable solutions.

Liquid crystal phase behavior of oxalated cellulose nanocrystal and optical films with controllable structural color induced by centripetal force

Cellulose nanocrystal (CNC) is a sustainable bio-nanomaterial. The distinctive left-handed polarization properties render cellulose nanocrystal a promising candidate for optical film. Due to eco-friendliness, reliability, mildness and simplicity, the oxalate hydrolysis method stands out among various preparation methods for CNC. This study delved into the liquid crystal phase behavior of oxalated cellulose nanocrystal derived from pulp, and discovered the influences of CNC concentration and pH on suspension stability and phase transition, and evaluated its optical properties. The results demonstrated that oxalated CNC presented two different liquid crystal phases, the nematic phase and the cholesteric phase. The stability mechanism of CNC suspension and the regulatory principle of the liquid crystal phase transition were revealed. A novel CNC film-forming technology, the multilayer spin-coating technique, was developed for cellulose nanocrystal optical films. Driven by centrifugal force, cellulose nanocrystals were induced to self-assembly and formed the optical film with circular dichroism and structural color. This simple and efficient film-forming technology promised rapid processing (1 h) and controllable film structure and optical properties compared to traditional technologies. This work provided a theoretical understanding and practical prospects for integrating oxalated cellulose nanocrystal into sustainable advanced optical film materials.

The effects of cellulose nanocrystals (CNC) and halloysite nanotubes (HNT) on selected properties of crosslinked modified tapioca starch films

Abstract Crosslinked modified tapioca starch films with CNC and HNT have the potential to be good renewable and biodegradable food packaging. Starch, CNC, and HNT were used because of their availability and cheap cost. This study aimed to investigate the effect of varying concentrations of CNC and HNT on the morphology, mechanical and optical properties of crosslinked modified tapioca starch films as an initial step in developing an active food package. Both CNC and HNT have high crystallinity and a large amount of OH groups. The OH groups as well as the ion-dipole interaction in HNT increase the tensile strength of the films. The highest tensile strength and the lowest elongation were recorded in films containing 5% CNC and 5% HNT. Beyond 5%, the addition of these nanomaterials diminished the tensile strength due to agglomeration which is the weak point of the films. Below the 5%, the nanomaterials serve as good reinforcing agents which improve the tensile strength. In addition, all films have good transmission capacity for visible light, while films with HNT outperform films with CNC in UV blocking ability.

Enhanced rheology and firefighting performance of fluorine-free soft foams through the assembly of cellulose nanofibres and cellulose nanocrystals at the air–liquid interface

In this work, we developed soft and highly stable perfluorocarbon-free foams based on cellulose nanofibres (CNFs), cellulose nanocrystals (CNCs) and alkyl polyglycoside (APG). Neither the CNCs nor the CNFs can effectively stabilise the APG foam, which is reflected in the spontaneous degradation of the foam. Interestingly, blending these two nanocelluloses and foaming resulted in an ultrastable foam. The reflective optical interference technique was used to visualise liquid flow in the liquid film, and the results showed that the foam film with a thickness of only a few tens of nanometres gained excellent mechanical stability by tuning the assembly of CNCs and CNFs at the air–liquid interface. Moreover, the interfibril interactions at the Plateau borders reduce the bubble coarsening rate and drainage rate. In pool fire extinguishing tests, increasing the total concentration of CNCs and CNFs improved the foam stability, but increasing the viscosity led to a decrease in the foam spreading rate. Thus, a formulation with 0.4 % nanocellulose has poorer firefighting performance than a formulation with 0.15 % nanocellulose. When the ratios of CNCs and CNFs are properly controlled, the burnback performance of perfluorocarbon-free foam is better than that of state-of-the-art fluorinated AFFFs for n-heptane pool fires. The sustainability of the firefighting process is considerably improved by switching to the nonperfluorinated liquid foam developed in this work.

Tragacanth gum hydrogels with cellulose nanocrystals: A study on optimizing properties and printability

This study investigates a novel all-polysaccharide hydrogel composed of tragacanth gum (TG) and cellulose nanocrystals (CNCs), eliminating the need for toxic crosslinkers. Designed for potential tissue engineering applications, these hydrogels were fabricated using 3D printing and freeze-drying techniques to create scaffolds with interconnected macropores, facilitating nutrient transport. SEM images revealed that the hydrogels contained macropores with a diameter of 100–115 μm. Notably, increasing the CNC content within the TG matrix (30–50 %) resulted in a decrease in porosity from 83 % to 76 %, attributed to enhanced polymer-nanocrystal interactions that produced denser networks. Despite the reduced porosity, the hydrogels demonstrated high swelling ratios (890–1090 %) due to the high water binding capacity of the hydrogel. Mechanical testing showed that higher CNC concentrations significantly improved compressive strength (27.7–49.5 kPa) and toughness (362–707 kJ/m3), highlighting the enhanced mechanical properties of the hydrogels. Thermal analysis confirmed stability up to 400 °C and verified ionic crosslinking with CaCl₂. Additionally, hemolysis tests indicated minimal hemolytic activity, affirming the biocompatibility of the TG/CNC hydrogels. These findings highlight the potential of these hydrogels as advanced materials for 3D-printed scaffolds and injectable hydrogels, offering customizable porosity, superior mechanical strength, thermal stability, and biocompatibility.

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.

Electrodeposited zinc cellulose nanocrystals composite coatings: Morphology, structure, corrosion resistance and electrodeposition process

Nanoparticles, particularly ceramic, have been widely investigated as beneficial additives in electrodeposited zinc coatings. However, exploiting cellulose-based nanocrystals derived from plant sources is attractive due to their cost-effectiveness and sustainability. In this work, we assessed the impact of various concentrations of cellulose nanocrystals, ranging from 0 to 8 v/v%, on the characteristics of zinc coatings obtained through electrodeposition. We investigated the morphology and structure of the zinc deposits using scanning electron microscopy (SEM), x-ray diffraction (XRD), and confocal microscopy (CM). Corrosion resistance was evaluated through mass loss measurements and electrochemical tests including DC (potentiodynamic polarization) and AC (electrochemical impedance spectroscopy) measurements. Increasing cellulose nanocrystal concentrations up to 7 v/v% notably enhanced the corrosion resistance in 0.5 M NaCl solution. In comparison to coatings with no cellulose addition, the 7 v/v% cellulose concentration resulted in: i) an increase in polarization resistance from 586 Ω cm2 to 1850 Ω cm2, ii) a decrease in corrosion current density from 3.21 × 10−5 A/cm2 to 0.76 × 10−5 A/cm2, and iii) a reduction of the corrosion rate from 0.15 mm/year to 0.08 mm/year assessed after 24-h immersion. Furthermore, the addition of this optimal concentration of nanocrystals enhanced current efficiency to approximately 95%, without compromising microhardness, which remained around 184 HV0.1. Additionally, the incorporation of cellulose nanocrystals resulted in a more compact coating with reduced roughness (Ra ∼0.69 μm). This work thus showcases the significant and beneficial impact of cellulose nanocrystals in producing enhanced electrodeposited zinc coatings.

Mechanical and shrinkage properties of cellulose nanocrystal modified alkali-activated fly ash/slag pastes

Alkali-activated materials based on fly ash (FA) and ground granulated blast furnace slag (GGBFS) offer lower carbon footprints but face challenges like low tensile strength and shrinkage susceptibility. This research explores the potential of cellulose nanocrystals (CNC) as additives to enhance the mechanical and shrinkage properties of alkali-activated fly ash/slag (AAFS) pastes to advance sustainable construction materials. A comprehensive examination is conducted on the impact of different contents of CNC (0.05 %, 0.1 %, 0.2 %, and 0.3 % by mass of FA + GGBFS) on the properties of AAFS pastes with two different alkaline activator contents (4 % and 8 % by mass of FA + GGBFS). It is found that incorporating 0.3 % CNC into AAFS pastes respectively improves the 28-day compressive and flexural strengths by 18.54 % and 60.87 % (8 % alkaline activator) and by 16.99 % and 50.12 % (4 % alkaline activator), and reduces the autogenous shrinkage and drying shrinkage by 26.42 % and 50.32 % (8 % alkaline activator) and by 11.74 % and 22.05 % (4 % alkaline activator). Also, the flexural/compressive strength ratio of AAFS pastes is increased with increasing CNC content. The microstructural analysis shows increased hydration product formation and a smoother, more compact morphology in CNC-modified samples, which together with water retention and distribution effect and nano-reinforcing effect of CNC explains the improvements in mechanical properties and volume stability. The research findings highlight the great potential of CNC as a reinforcing agent for sustainable construction materials, aligning with the demand from industries for eco-friendly alternatives to traditional cementitious materials.

Tuning Rigid Polyurethane Foam with Eco-friendly Cellulose Nanocrystals from Oil Palm Empty Fruit Bunches as Energy-Efficient Material Composites for Buildings

The development of novel materials based on renewable materials with beneficial properties that assist with energy efficiency and conservation has been encouraged by increasing consciousness of environmental issues. This research intends to use sustainable cellulose nanocrystals (CNC) obtained from oil palm empty fruit bunches (OPEFB) as reinforcement to enhance the properties of rigid polyurethane foam (RPUF). RPUF reinforcement with varied CNC concentrations (0.25–1 wt%) was examined by foaming behavior, surface morphology, mechanical properties, thermal insulation properties, dimensional stability, efficiency energy study, and CO2 reduction through their thermal conductivity values. The results achieved an optimal improvement of mechanical properties of the RPUF composite by around 23.53% compared to RPUF control, at the addition of 0.5 wt% of CNC concentration while maintaining the density of 37–39 kg/m3. Further, incorporating CNC improved thermal insulating performance by 9.95%, as reflected by decreased thermal conductivity from 0.0292 W/mK to 0.0269 W/mK and decreased cell size by 28.12%. Finally, based on the energy and cost efficiency studies, RPUF-CNC composites offer up to 0.78 kWh/m2 and 0.031 kWh/m2 compared to conventional wall materials made of concrete and wood, respectively. Furthermore, it contributed to reduced greenhouse gas (GHG) emissions by 110 and 7.2 kg CO2/year compared to concrete and wood, respectively. This work demonstrates the promising use of eco-friendly building insulation materials to mitigate the energy and environmental crisis.

The synthesis of TiO2 using a nanocrystalline cellulose template improves its photocatalytic performance

Using cellulose nanocrystals (CNCs) as a template in the production of TiO2 has a positive impact on its crystal and porous structure, ultimately improving its photocatalytic performance. In this study, TiO2 photocatalysts with mesoporous anatase structures were prepared by acid-catalyzed hydrolysis using sulfate-ester-modified CNCs as the template. The effects of CNC concentration on the structure and performance of TiO2 were investigated in detail. The addition of CNCs was found to inhibit TiO2 transformation from the anatase to rutile phase, and abundant hydroxyl and sulfate ester groups on the CNCs provide narrow confined spaces for the crystal growth of TiO2, leading to the generation of smaller crystals with more exposed (001) crystal faces. Moreover, the CNCs act as a template for the pore structure remaining after calcination, thus increasing the specific surface area of the TiO2. Among the numerous samples evaluated, that prepared with a CNC concentration of 0.15 wt% and calcined at 600 °C had the highest percentage of (001) crystalline surface exposure. In photodegradation tests using phenol as a model pollutant, a degradation rate of 97.4 % and mineralization rate of 79.9 % were achieved with 60 min of light exposure. Thus, this study provides a clear approach for the directional synthesis of mesoporous TiO2 from biomass template materials.

Biodegradable active films based on Chlorella biomass and cellulose nanocrystals isolated from hemp stalk fibers

Cellulose nanocrystals (CNC)-reinforced biopolymers have emerged as a widely embraced approach for enhancing the characteristics of biopolymers due to their exceptional properties. Biocomposite (Chl-CNC) films were fabricated by blending Chlorella biomass and varying concentrations of CNCs via a solution casting technique. CNCs were effectively isolated from hemp stalk fibers, as confirmed by structural, surface, thermal, and morphological analysis. The crystallinity of films increased by CNC incorporation, which was confirmed by the XRD. The presence of molecular interactions between CNC and protein-rich Chlorella biomass was illustrated with the FTIR analysis. These interactions enhanced the physicochemical properties of the films. Further, films demonstrated a high level of soil biodegradation in the 42 days, while their total phenolic, chlorophyll, carotenoid contents, and antibacterial activity were unaffected by the incorporation of CNCs. The Chl-CNC films, regardless of CNC addition, indicated antimicrobial activity toward Escherichia coli but not Staphylococcus aureus. These results indicate that developed biobased and biodegradable Chl-CNC films could be highly beneficial in active food packaging applications.

Fabrication of PMMA nanocomposite biomaterials reinforced by cellulose nanocrystals extracted from rice husk for dental applications

The primary objective of global studies is to develop the properties and durability of polymers for various applications. When it comes to dental disability, denture base materials must have sufficient mechanical and tribological performance in order to withstand the forces experienced in the mouth. This work aims to investigate the effects of the addition of low content of cellulose nanocrystals (CNC) on the mechanical and tribological performance of the polymethyl methacrylate (PMMA) nanocomposites. Different weight percent of CNC (0, 0.2, 0.4, 0.6, and 0.8 wt%) were added to the PMMA matrix followed by ball milling to evenly distribute the nanoparticles reinforced phase in the matrix phase. The findings emphasize the significant impact of CNC integration on the performance of PMMA nanocomposites. By increasing the content of the CNC nanoparticles, the mechanical properties of PMMA were improved. In addition, the tribological outcomes demonstrated a significant reduction in the friction coefficient besides an enhancement in the wear resistance as the weight percentage of nanoparticles increased. The surface of the worn samples was investigated by utilizing SEM to identify the wear mechanisms corresponding to the different compositions. In addition, a finite elment model (FEM) was developed to ascertain the thickness of the worn layer and the generated stressed on the surfaces of the nanocomposite throughout the friction process.

Depletion Flocculation of High Internal Phase Pickering Emulsion Inks: A Colloidal Engineering Approach to Develop 3D Printed Porous Scaffolds with Tunable Bioactive Delivery.

Flocculation is a type of aggregation where the surfaces of approaching droplets are still at distances no closer than a few nanometers while still remaining in close proximity. In a high internal-phase oil-in-water (O/W) emulsion, the state of flocculation affects the bulk flow behavior and viscoelasticity, which can consequently control the three-dimensional (3D)-printing process and printing performance. Herein, we present the assembly of O/W Pickering high-internal-phase emulsions (Pickering-HIPEs) as printing inks and demonstrate how depletion flocculation in such Pickering-HIPE inks can be used as a facile colloidal engineering approach to tailor a porous 3D structure suitable for drug delivery. Pickering-HIPEs were prepared using different levels of cellulose nanocrystals (CNCs), co-stabilized using "raw" submicrometer-sized sustainable particles from a biomass-processing byproduct. In the presence of this sustainable particle, the higher CNC contents facilitated particle-induced depletion flocculation, which led to the formation of a mechanically robust gel-like ink system. Nonetheless, the presence of adsorbed particles on the surface of droplets ensured their stability against coalescence, even in such a highly aggregated system. The gel structures resulting from the depletion phenomenon enabled the creation of high-performance printed objects with tunable porosity, which can be precisely controlled at two distinct levels: first, by introducing voids within the internal structure of filaments, and second, by generating cavities (pore structures) through the elimination of the water phase. In addition to printing efficacy, the HIPEs could be applied for curcumin delivery, and in vitro release kinetics demonstrated that the porous 3D scaffolds engineered for the first time using depletion-flocculated HIPE inks played an important role in 3D scaffold disintegration and curcumin release. Thus, this study offers a unique colloidal engineering approach of using depletion flocculation to template 3D printing of sustainable inks to generate next-generation porous scaffolds for personalized drug deliveries.

Synthesis of thermally and pH-responsive poly(2-(dimethylamino)ethyl methacrylate)-based hydrogel reinforced with cellulose nanocrystals for sustained drug release

Hydrogels are widely employed in biomedical applications due to their high swelling potential, tailored mechanical properties, biocompatibility, and ability to incorporate drugs to modify their release behavior. This study explored the synthesis of dual stimuli-responsive composite hydrogels by combining poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) with 4, 8, and 12 % (w/w) of cellulose nanocrystals (CNC) through in-situ free-radical polymerization, modifying their properties for topical anti-inflammatory release. Although PDMAEMA-based hydrogels have been known for their responsiveness to pH and temperature stimuli, which are useful for modulating the release profile of drugs, their use as a matrix for anti-inflammatory topical applications remains unexplored. Thus, a comprehensive analysis of CNC concentration's impact on PDMAEMA-based hydrogel structure and physicochemical properties is provided. The incorporation of ibuprofen as an anti-inflammatory model was assessed, providing insights into the potential of these composite hydrogels for sustained drug delivery applications. Overall, the hydrogels exhibited homogenous CNC dispersion, with gel fraction higher than 70 % and ibuprofen load higher than 90 %. The rise in CNC concentration led to an increase hydrogel stiffness. Finally, the CNC incorporation also modified the ibuprofen release to a more sustained profile, following the Peppas-Sahlin model, which may be attractive for developing pharmaceutical devices for different therapeutical scenarios.

High performances of cellulose nanocrystal based bicomponent supramolecular hydrogel lubricant

To improve the limitations of water-based lubricants, a novel cellulose nanocrystal based supramolecular hydrogel (CNC/x-DG/y) was prepared by mixing cellulose nanocrystal (CNC) and diglycerol (DG) into deionized water (DW). The hydrogel was characterized to determine its material ratio and gelation mechanism. When DW was fixed at 1 mL, CNC content should be no <2.4 wt% and DG content 0.1–1.3 mL. The gelification was driven by the multiple H-bond network between CNC and DG, which immobilized water molecules. The rheological performances, the anti-rust property and the volatilization behaviour of the hydrogel were further studied. The results showed that the hydrogel had satisfactory viscoelasticity, excellent thermal stability, strong creep recovery, high anti-rust performance and low volatilization rate, which were exactly its advantages for use as lubricant. A typical representative of the hydrogel, namely CNC/2.4-DG/0.1, was selected to evaluate the tribological performances, and the resulting worn surfaces were analyzed. CNC/2.4-DG/0.1 exhibited a lower friction coefficient of 0.059 and a smaller wear volume of 0.81 × 10−3 mm3, compared to DW(1 mL) + CNC(2.4 wt%) and DW(1 mL) + DG(0.1 mL). The outstanding tribological performances of CNC/2.4-DG/0.1 were reasonably attributed to the synergistic mending effect of CNC and DG and the dissipative effect of H-bonds between the two.

Comprehensive comparison of cellulose nanocrystal (CNC) drying using multi-frequency ultrasonic technology with selected conventional drying technologies

Cellulose nanocrystals (CNCs) have garnered increased attention due to their renewable nature, abundant feedstock availbility, and good mechanical properties. However, one of the bottlenecks for its commercial production is the drying process. Because of the low CNC concentrations in suspension after isolation, CNC drying requires the removal of a large amount of water to obtain dry products for the following utilization and saving shipping costs. A novel multi-frequency, multimode, modulated ultrasonic drying technology was developed for CNC drying to improve product quality, reduce energy consumption, and increase production rate. CNCs dried with different drying technologies were characterized by Fourier transform infrared (FT-IR) spectra analysis, X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and redispersibility to measure the quality and property changes. Under the same temperature and airflow rate, ultrasonic drying enhanced drying rates, resulting in at least a 50% reduction in drying time compared to hot air drying. The mean particle sizes of CNC from ultrasonic drying changed little with settling time, indicating good redispersibility. In addition, ultrasonic dried CNCs exhibited good stability in aqueous solutions, with the zeta potentials ranging from –35 to –65 mV. Specific energy consumption and CO2 emissions of various CNC drying technologies were evaluated. Energy consumption of ultrasonic drying is significantly reduced compared to other drying technologies. Moreover, the potential CO2 emissions of the fully electrified ultrasonic drying could be net zero if renewable electricity is used.

Modulation of Tannic Acid on the Cholesteric Structure of Cellulose Nanocrystals.

The chiral nematic phase structure, formed by the self-assembly of cellulose nanocrystals (CNCs) in an aqueous suspension and maintained in a solid film, shows great potential for optical applications. To achieve complex structures in optical devices, it is crucial to subject CNCs to specific shearing processes, such as spinning and printing. Understanding the structural and property changes of the CNC liquid crystal phase in these processes is of utmost importance. In this study, we investigated the effect of adding tannic acid (TA) on the rheological properties and cholesteric phase structures of CNCs/TA mixed suspensions. By calculating the surface site interaction points, we observed that TA can adsorb onto the surface of CNC rods in suspensions through hydrogen bonding. Through characterization techniques, such as polarized optical microscopy, rheology, and synchrotron SAXS, we examined the effects of TA addition on the microstructure and rheological properties of the CNC liquid crystal phase and clarified the change relating to the system composition. Under the same CNC concentration, the volume fraction of the anisotropic phase, the pitch, and the rod spacing of the cholesteric phase were not significantly affected by the addition of TA. However, the system viscosity was significantly reduced with the appropriate amount of TA (2 wt %), in a wide range of CNC concentrations (up to 15 wt % CNCs). The flow indexes (n) in Region I and Region III of steady-state shear curves of CNCs/TA systems (11-15 wt % CNCs) were compared. Moreover, we introduced the well-established theoretical models for liquid crystal polymers to tentatively interpret Region I of the CNCs/TA cholesteric phase and realized that increased numbers of smaller cholesteric-phase domains in the CNCs/TA system and interfacial modification by TA may contribute to the fluidity change. The feature of the domain texture of CNCs/TA systems is verified by polarized optical microscopy observations.

Crystallization Behavior and Mechanical Property of Biodegradable Poly(butylene succinate-co-2-methyl succinate)/Cellulose Nanocrystals Composites.

Biodegradable poly(butylene succinate-co-2-methyl succinate) (PBSMS)/cellulose nanocrystals (CNC) composites were successfully prepared at low CNC loadings with the aims of improving crystallization and mechanical properties and extending the practical application of PBSMS. CNC is finely dispersed in the PBSMS matrix without obvious aggregations. The low content of CNC obviously promoted the crystallization behavior of PBSMS under different conditions. The spherulitic morphology study revealed that CNC, as an effective heterogeneous nucleating agent, provided more nucleation sites during the melt crystallization process. In addition, the nucleation effect of CNC was quantitatively evaluated by the following two parameters, i.e., nucleation activity and nucleation efficiency. The crystal structure and crystallization mechanism of PBSMS remained unchanged in the composites. In addition, as a reinforcing nanofiller, CNC significantly increased Young's modulus and the yield strength of PBSMS. The crystallization behavior and mechanical properties of PBSMS were significantly improved by the low content of CNC, which should be interesting and essential from the perspective of biodegradable polymer composites.

Effect of cellulose nanocrystals on performance of PVA fiber-reinforced geopolymer composites: Reaction kinetics, bending behavior, and toughening mechanisms

Geopolymer composites are an attractive alternative to those based on ordinary Portland cement, owing to their lower carbon footprint and higher mechanical performance. However, brittleness is one of the major barriers limiting their use in construction applications. In this work, cellulose nanocrystal (CNC), a cost-effective and eco-friendly nanoparticle, was exploited in polyvinyl alcohol (PVA)-reinforced metakaolin-based geopolymer composite to further increase its mechanical performance. To this end, PVA-reinforced geopolymer composites were prepared by varying the CNC concentration from 0 wt% to 0.15 wt%. Three-point bending and fracture testing, combined with digital image correlation (DIC) and scanning electron microscopy (SEM), were performed to evaluate the bending and fracture behavior of samples containing CNC and reveal various toughening mechanisms. Composites with 0.15 wt% CNC recorded an increase of 190% in flexural strength and a 325 time of increase in fracture energy, compared to the control geopolymer (i.e. without PVA fibers and CNC). Isothermal calorimetry, Fourier transform infrared (FTIR) spectroscopy, and x-ray diffraction (XRD) were also utilized to characterize the heat flow, chemical bonds, and crystalline phases of the samples. These analyses revealed that CNC incorporation increased the amount of formed geopolymer gel with no significant changes in the crystalline structure and chemical bonding. In addition, stronger interfacial bonding between the PVA-geopolymer matrix was achieved, resulting in substantial improvements in flexural strength and fracture energy.

In‐situ preparation and performance of cellulose nanocrystals grafted with polyamide 6 composites

AbstractNylon nanocomposites were prepared by in‐situ ring‐opening polymerization to overcome the problem of poor properties due to the uneven dispersion of the nanoparticles by the traditional melt blending. This high‐performance polyamide 6 (PA6) nanocomposites with high dispersion and strong interface was prepared by grafting PA6 onto the surface of cellulose nanocrystals (CNC). The micromorphology, mechanical, crystalline and thermal properties of the composites were also investigated. Firstly, the hydroxyl group on the surface of CNC reacted with the para isocyanate of toluene diisocyanate (TDI), and the remaining ortho isocyanate was blocked by caprolactam to prepare CNC grafted with caprolactam (CNC‐g‐CL). Then CNC‐g‐CL was used as an activator to prepare cellulose nanocrystal grafted with polyamide 6 (CNC‐g‐PA6) composites by the ring‐opening polymerization of caprolactam on the CNC. The effects of different reaction temperatures, solvent amounts and molar ratios on the grafting rate of CNC‐g‐CL were investigated. The results showed that the highest grafting rate of CNC‐g‐CL with 66.7% was achieved at a reaction temperature of 45°C, 0.1 g/mL CNC in toluene, and a molar ratio of 6 for TDI/CNC. Further, different CNC‐g‐PA6 composites prepared from different CNC content and activator content were explored. For CNC‐g‐PA6 composites, CNC was uniformly dispersed in the PA6 matrix and had a good compatibility with the matrix. CNC exhibited significant reinforcement in the composites with a tensile strength of up to 108 MPa. In addition, the glass transition temperature of CNC‐g‐PA6 was increased to 92°C, which significantly improved the heat resistance of the new composites.Highlights Effects of reaction condition of CNC and TDI on DSTDI and DSCL were studied. Effects of CNC and activator content on CNC‐g‐PA6 properties were studied. CNC is uniformly dispersed in PA6 with average particle size less than 1 micron. The nylon matrix was significantly strengthened by the addition of CNC. The addition of CNC significantly improved the heat resistance of the composites.