Nitrocellulose Research Articles

N-doped carbon dots for the determination of Al3+ and Fe3+ using aggregation-induced emission.

New portable hydrogel sensors for Al3+ and Fe3+ detection were designed based on the aggregation-induced emission (AIE) and color change of N-doped carbon dots (N-CDs). N-CDs with yellow fluorescence were prepared by a one-pot hydrothermal method from 2,5-dihydroxyterephthalic acid and acrylamide. The fluorescence of N-CDs was enhanced by Al3+ about 20 times and quenched by Fe3+. It was interesting that although Fe3+ showed obvious quenching on the fluorescence of N-CDs it did not cause a noticeable change in the fluorescence of N-CDs + Al3+. The colorless solution of N-CDs appeared blue in the presence of Fe3+ without the influence of Al3+. Therefore, the turn-on fluorometry and colorimetry systems based on N-CDs were constructed for the simultaneous detection of Al3+ and Fe3+. Furthermore, the portable sensing of Al3+ and Fe3+ was realized with the assistance of hydrogel, filter paper, cellulose acetate, and cellulose nitrate film. The proposed approach was successfully applied to the detection of Al3+ and Fe3+ in food samples and cell imaging.

Regulating hollow structure of CL-20 microspheres using microjet droplet technology to enhance safety and combustion performance

Hollow energetic microspheres have attracted great attention in the field of materials due to their wide application potential. However, scalable, simple, and low-cost production methods have not been achieved yet. In this study, using nitrocellulose (NC) as a binder, hollow and porous hollow CL-20 microspheres were prepared by the assist of microjet droplet technology. The effects of receiving liquid temperature, solution concentration, and solvent type on the morphology, particle size, shell thickness, and pore size of the CL-20 microspheres were systematically investigated. Furthermore, the influences of shell thickness and pore size on the dispersibility, crystal structure, thermal decomposition, mechanical sensitivity, and combustion behavior of CL-20 microspheres were further studied. The results showed that precise control over the shell thickness and pore size of CL-20 microspheres could be achieved by adjusting the process parameters. Compared to raw CL-20, the CL-20 microspheres exhibited excellent dispersibility and improved thermal and safety performance (raw CL-20 vs CL-20 microspheres, 40.3° vs 27.1° ∼ 29.1°; 240.4℃ vs 241.1 ∼ 246.2℃; 2 J vs 25 ∼ 32.5 J). Ignition experiments demonstrated that the hollow and porous hollow structures significantly enhanced the combustion flame of CL-20, shortened the burning time, and thereby improved energy release efficiency. This preparation method is simple and efficient, providing a new approach for the fabrication of multi-structured hollow energetic microspheres.

Regulating the Thermal Behavior of Nitrocellulose by Stable Incorporation of a Green Supramolecular Salt

Commonly used inorganic potassium salts present challenges in nitrocellulose (NC)-based propellants due to poor dispersion, destabilization, and toxic byproduct formation. Environmental concerns drive interest in green flame suppressants. Here, we report a green supramolecular salt, carboxymethyl-cyclodextrin potassium (CM-CD-K) through alkalinization and etherification reaction. Molecular dynamic simulations reveal stronger interactions between CM-CD-K and NC. The loading of CM-CD-K within NC forms a stable structure with resistance to migration and defense against crystalline precipitation. Remarkably, static combustion tests show reduced flame areas and harmful gas concentrations compared to traditional potassium salt-doped NC. Kinetic analysis reveals a shift from order to Kamal-Sourour reaction with CM-CD-K addition. CD-based hybrid organic salts hold potential as eco-friendly propellant alternatives.

Simultaneous Production of Cellulose Nitrates and Bacterial Cellulose from Lignocellulose of Energy Crop.

This study is focused on exploring the feasibility of simultaneously producing the two products, cellulose nitrates (CNs) and bacterial cellulose (BC), from Miscanthus × giganteus. The starting cellulose for them was isolated by successive treatments of the feedstock with HNO3 and NaOH solutions. The cellulose was subjected to enzymatic hydrolysis for 2, 8, and 24 h. The cellulose samples after the hydrolysis were distinct in structure from the starting sample (degree of polymerization (DP) 1770, degree of crystallinity (DC) 64%) and between each other (DP 1510-1760, DC 72-75%). The nitration showed that these samples and the starting cellulose could successfully be nitrated to furnish acetone-soluble CNs. Extending the hydrolysis time from 2 h to 24 h led to an enhanced yield of CNs from 116 to 131%, with the nitrogen content and the viscosity of the CN samples increasing from 11.35 to 11.83% and from 94 to 119 mPa·s, respectively. The SEM analysis demonstrated that CNs retained the fiber shape. The IR spectroscopy confirmed that the synthesized material was specifically CNs, as evidenced by the characteristic frequencies of 1657-1659, 1277, 832-833, 747, and 688-690 cm-1. Nutrient media derived from the hydrolyzates obtained in 8 h and 24 h were of good quality for the synthesis of BC, with yields of 11.1% and 9.6%, respectively. The BC samples had a reticulate structure made of interlaced microfibrils with 65 and 81 nm widths and DPs of 2100 and 2300, respectively. It is for the first time that such an approach for the simultaneous production of CNs and BC has been employed.

Evaluating the effect of ammonium nitrate-based cocrystals on the properties and thermokinetic characteristics of a double-base propellant

This work aims to investigate the characteristics of a modified double-base propellant based on hydrazine 3-nitro-1,2,4-triazol-5-one and ammonium nitrate (HNTO/AN), nitrocellulose (NC), and diethylene glycol dinitrate (DEGDN), for which the optimal formulation was selected based on theoretical performance calculations. Structural and morphological results demonstrated that HNTO/AN co-crystals were homogenously distributed within the NC-DEGDN matrix without discernible alterations in the chemical structure. Furthermore, thermal analyses provided substantial evidence of the mutual thermal decomposition effect between HNTO/AN and NC-DEGDN. Indeed, thermal findings highlighted that the addition of HNTO/AN accelerated the thermolysis of NC-DEGDN propellant and significantly increased its heat release by approximately 1042.8 J/g. Additionally, a notable decrease in the activation energy was also observed, revealing the catalytic influence of HNTO/AN microparticles on the thermolysis of NC/DEGDN propellant.

A rapid and non-destructive identification method for tortoiseshell products using attenuated total reflectance infrared spectroscopy

Tortoiseshell, traditionally made from Hawksbill Turtle (Eretmochelys imbricata) shell, has long been a popular material for the production of coveted ornamental items. Hawksbill Turtles are critically endangered and like all sea turtles the trade in their products (e.g., tortoiseshell) is illegal. Tortoiseshell objects are also produced from other species and plastics, so the identification of the tortoiseshell source is important for distinguishing illegally and legally traded items. Distinguishing faux and real tortoiseshell visually can be challenging, so a screening method using infrared spectroscopy has been developed to provide a rapid means of discriminating the source of objects. A non-destructive attenuated total reflectance sampling technique has been employed. Marine turtle, horn, casein, cellulose nitrate, cellulose acetate and polyester were identified as the materials used in tortoiseshell production by employing a visual comparison of their spectra. A simple method for the discrimination of the protein-based spectra produced by marine turtle, horn and casein objects is provided, enabling the source of such objects to be differentiated.

Assessment of the effect of lignin biopolymer on the thermal stability of energetic nitrocellulose/diethylene glycol dinitrate composite

AbstractThis study explored the stability and thermo‐kinetic features of double base nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN) propellant supplemented with Kraft lignin. For this purpose, the impact of 2‐nitrodiphenylamine (2‐NDPA), 1,3‐dimethyl‐1,3‐diphenylurea (C‐II) and lignin stabilizers on the molecular structure, morphology, and thermokinetic behavior of NC/DEGDN composite were thoroughly analyzed. Experimental results showed that lignin exhibits promising stabilizing efficiency comparable to that of the conventional 2‐NDPA and C‐II. In addition, thermal findings highlighted that the incorporation of 2‐NDPA, C‐II, and lignin has improved the thermal decomposition temperature of NC/DEGDN propellant. The investigation of the thermolysis kinetics of stabilized NC/DEGDN composites demonstrated an increase in the Arrhenius parameters with respect to the NC/DEGDN baseline. Above all, this investigation contributes to the ongoing efforts to develop new environmentally friendly stabilizers for nitrate esters‐based composites.

Thermal kinetics and flash DSC experimental validation of conventional nitrocellulose and ladder-structured nitrocellulose under non-isothermal condition

To better understand the thermal decomposition mechanism of conventional nitrocellulose (NC) and ladder-structured nitrocellulose (LNC), and effectively improve their safety performance during storage and service, the NC and LNC samples were subjected to non-isothermal DSC experiments to analyze their thermal kinetics. The model-free methods and model-fitting methods were used to analyze the thermal decomposition process of NC and LNC. The reaction autocatalytic behavior is confirmed in the thermal decomposition process of NC and LNC by Friedman analysis. Considering the fitting degree and the degree of freedom of the methods and models, the composite autocatalysis reaction model is the most suitable method to describe the thermal decomposition process of NC and LNC. Furthermore, the prediction accuracy of the composite autocatalysis reaction model is validated by the Flash DSC experimental data. The error between the actual and predicted peak temperatures is only approximately 1.5 %. Based on the composite autocatalysis reaction model of NC and LNC, the process of the thermal decomposition reaction of NC and LNC is obtained with high precision for their Flash DSC experimental data. This study can provide theoretical guidance for the process control of the thermal decomposition of NC and LNC. Novelty and Significance statementThe thermal decomposition mechanism of NC and LNC is studied. The kinetic model for the thermal decomposition of NC and LNC are deduced. The thermal decomposition kinetics equations for NC and LNC is obtained. The accuracy of the thermal decomposition kinetics equations of NC and LNC in predicting thermal decomposition behavior at extremely high heating rates is verified. This study can provide theoretical guidance for the process control of the thermal decomposition of NC and LNC.

Portable SERS-based lateral flow immunoassay strips with self-calibration for detection of a prostate cancer biomarker

Serum prostate-specific antigen (PSA) is thought to be the most vital indicator for early identification, staging and monitoring of prostate cancer (PCa). Although lateral flow immunoassay (LFA) has demonstrated limitless promise for point-of-care testing (POCT) and has drawn increasing interest and attention, there are significant restrictions on the assay's sensitivity and quantitative capability. Surface-enhanced Raman spectroscopy-based LFA (SERS-LFA) technique integrates the great sensitivity of SERS with the simplicity, rapidity, and usability of the LFA technique, making it ideal for POCT. In this paper, we propose a sensitive self-calibrating SERS-LFA platform, which uses Au@MBN@Ag@PSA NPs as a SERS immunoprobe for the specific recognition of PSA and loads graphene oxide/gold nanoparticles (GO/Au NPs) on nitrocellulose (NC) membranes as an internal standard (IS) molecule. The SERS-LFA platform's detection accuracy is increased through dynamic calibration of the characteristic signals, which is accomplished by detecting the immunoprobe and IS signals simultaneously and computing their respective signal intensity ratios. The self-calibrated SERS-LFA platform demonstrated a 1.65-fold improvement in reproducibility over the conventional SERS-LFA, and PSA could only be detected to a limit of 0.08 ng/mL, meaning that it was 3.5-fold lower than the conventional SERS-LFA platform. The spike recovery experiments yielded recoveries of 96.16∼104.53% with RSD values of 9.37%, 8.66%, and 3.49%, respectively, demonstrating that our self-calibrated SERS-LFA platform for PSA quantification has an acceptable level of precision and has great prospect for early screening of PCa and other diseases.

Simple and Multiplexed Detection of Nucleic Acid Targets Based on Fluorescent Ring Patterns and Deep Learning Analysis.

Simple diagnostic tests for nucleic acid targets can provide great advantages for applications such as rapid pathogen detection. Here, we developed a membrane assay for multiplexed detection of nucleic acid targets based on the visualization of two-dimensional fluorescent ring patterns. A droplet of the assay solution is applied to a cellulose nitrate membrane, and upon radial chromatographic flow and evaporation of the solvent, fluorescent patterns appear under UV irradiation. The target nucleic acid is isothermally amplified and is immediately hybridized with fluorescent oligonucleotide probes in a one-pot reaction. We established the fluorescent ring assay integrated with isothermal amplification (iFluor-RFA = isothermal fluorescent ring-based radial flow assay), and feasibility was tested using nucleic acid targets of the receptor binding domain (RBD) and RNA-dependent RNA polymerase (RdRp) genes of SARS-CoV-2. We demonstrate that the iFluor-RFA method is capable of specific and sensitive detection in the subpicomole range, as well as multiplexed detection even in complex solutions. Furthermore, we applied deep learning analysis of the fluorescence images, showing that patterns could be classified as positive or negative and that quantitative amounts of the target could be predicted. The current technique, which is a membrane pattern-based nucleic acid assay combined with deep learning analysis, provides a novel approach in diagnostic platform development that can be versatilely applied for the rapid detection of infectious pathogens.

Influence Analysis of Polyvinyl Alcohol on the Degradation of Artificial Leather with Cellulose Nitrate Coating Originating from a Suitcase Stored in the Collection of the Auschwitz-Birkenau State Museum in Oświęcim, Poland.

The aim of this study was to assess the influence of a protective layer of polyvinyl alcohol on the degradation process of artificial leather based on cellulose nitrate. Samples of the artificial leather were obtained from a suitcase dating back to the first half of the 20th century, not considered a historical artifact. The analysis involved Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Artificial aging was employed for the study. The artificial leather sample with a protective coating of polyvinyl alcohol on a cellulose nitrate base exhibited the lowest degree of degradation due to minimal chemical changes in cellulose esters. The obtained FTIR-ATR spectrum indicated significantly higher nitration of cellulose and, consequently, a lower degree of polymer degradation. The sample without the protective polyvinyl alcohol coating and the sample with the coating removed before artificial aging showed similar reactions.

Best billiard ball in the 19th century: Composite materials made of celluloid and bone as substitutes for ivory.

The demystification of how 19th-century novelly designed materials became significant elements of modern technological, economic, and cultural life requires a complete understanding of the material dimensions of historical artifacts. The objects frequently described as the earliest manufactured plastic products-the billiard balls made by John Wesley Hyatt and his associates from the late 1860s-are examined closely for the first time and are found to be more complex and functionally more successful than has been described. Modern analytical techniques such as optical microscopy, scanning electron microscope-energy dispersive X-ray spectroscopy, X-ray fluorescence, micro-Fourier transformed infrared, and handheld/micro-Raman spectroscopies were used to reveal the complex composition of the Smithsonian Institution's "original" 1868 celluloid billiard ball. Comparisons with billiard and pool balls commercialized from the 1880s to the 1960s showed an unexpected consistency in material formulations. All specimens were made of an unprecedented composite material prepared with a mixture of cellulose nitrate, camphor, and ground bone; the source of the bone was identified as cattle by peptide mass fingerprint (ZooMS). Patent specifications and contemporary journal descriptions explained how and when these formulations emerged. Combining the technical analyses of compositions with a careful reading of the historical record and contemporary descriptions reveals the key elements of the first successful efforts to substitute materials to assist the survival of endangered animals.

A paper-based aptamer-sandwich assay for detection of HNP 1 as a biomarker for periprosthetic joint infections on an integrated microfluidic platform

BackgroundTotal joint arthroplasty (TJA) has significantly improved the quality of life for millions suffering from end-stage arthritis. However, periprosthetic joint infections (PJI) remain a serious complication, necessitating extensive interventions and prolonged antimicrobial treatments. The aging population is expected to lead to a rise in TJA cases, subsequently increasing the incidence of PJI, particularly in the elderly who face higher mortality rates. Current diagnostic methods for suspected PJI, such as radiographs and biochemical markers like CRP and ESR, exhibit limited sensitivity. Therefore, there is a critical need for a specific synovial fluid biomarker assay to enhance PJI diagnosis using specific SF-based assay. ResultsThis study introduces a novel microfluidic chip with a paper-based aptamer-sandwich assay for the quantitative detection of HNP 1, a crucial PJI biomarker, in synovial fluid. The assay leverages the advantages of aptamers over antibodies, demonstrating high selectivity and affinity for target molecules. The integration of a nitrocellulose (NC) membrane onto the microfluidic platform represents a significant advancement, reducing background signals and simplifying the assay procedure without intricate procedure and pre-treatment. The NC membrane-based microfluidic device offers rapid, cost-effective, and highly sensitive detection of HNP 1, with a limit of detection of 0.5 mg L−1. The microfluidic device demonstrates exceptional performance, detecting up to four clinical samples in approximately 42 min on a single chip with 100 % accuracy, as confirmed by analysis of 12 clinical samples and comparison with “gold-standard”. Moreover, the assay exhibits a wide dynamic range of 0.5–100 mg L-1, underscoring its potential as a powerful tool for PJI diagnosis in clinical settings. SignificanceThis work introduces a paper-based microfluidic system tailored for rapid HNP 1 detection using synovial fluid near joint region (and not serum via blood) for better diagnosis. The innovative paper-based aptamer-sandwich assay yields results within 42-min. Significantly, it boasts a wide dynamic range, detecting levels from an impressive 0.5 mg L-1, crucial in the 2.6 mg L-1 threshold region. This heightened sensitivity and expansive detection capability establish our assay as a leader in PJI diagnostics, promising unmatched precision and efficiency in clinical applications.

Friction Sensitivity Test Experiment and Desensitization Mechanism of Nitrocellulose-Coated DNTF Explosive Crystals

In response to the problem of the high friction sensitivity of 3,4-bis(3-nitrofurazan-4-yl) furoxan (DNTF) in solid propellants, the inherent component of solid propellants, nitrocellulose (NC), was used to coat DNTF explosives via the water suspension method. The coated samples were characterized by scanning electron microscopy (SEM) and friction sensitivity tests at a fixed 66° swing angle, and molecular dynamics calculations were performed to study the friction sensitivity and desensitization mechanism of NC-based DNTF coatings. The results show that NC, when used as a coating layer, can form a white gel on the surface of DNTF crystals, which can effectively reduce the friction sensitivity of DNTF. The coating effect becomes more obvious as the NC content increases. When the NC content is 5%, the friction sensitivity decreases by 72%, and a prediction formula for the exponential decay of DNTF friction sensitivity is obtained. MD calculation data show that NC can weaken the stiffness, enhance the elastic-plastic properties, increase the ductility and toughness of DNTF materials, and effectively improve the mechanical properties of DNTF. By combining experiments and simulation calculations, while considering the compatibility of new components and changes in propellant energy and other unpredictable new issues, NC can be referred to as a better coating layer for DNTF, as it has a certain feasibility for improving the friction sensitivity of DNTF.

Unrevealing the role of the sulfonitric media composition on the design and properties of potato starch-based nitrogen-rich biopolymer

In research of crafting high-energy materials from sustainable sources, this study undertook the synthesis of energetic nitrostarches employing diverse sulfonitric mediums to better assess how they influence the characteristics and performance of potato starch nitrate. Accordingly, a deep exploration of the physicochemical properties, morphology, heat behavior, mechanical sensitivities, and combustion energy of starch nitrate was carried out. The experimental results highlighted that an increase in the nitric acid concentration from 70% to 100% enhanced the density (≥1.71 g/cm3) and the crystallinity of potato starch nitrate, whereas the nitrogen content does not exhibit any evident correlation. Moreover, its short-term stability remains unaffected as a function of nitric acid content, in contrast to the long-term stability together with mechanical sensitivities (Impact Sensitivity ≥ 4 J; Friction Sensitivity ≥ 252 N) that decrease with nitrogen content. The investigation of the thermolysis kinetics of starch nitrate demonstrated a decrease in the activation barrier (Ea) with the increase in nitrogen content. The Ea of high nitrogen content potato starch nitrate is inferior to that of cellulose nitrate, proving the enhanced reactivity of starch nitrate. These findings demonstrated that the elaborated nitrogen-rich potato starch biopolymers display promising features that support their use in high-performance propellant or explosive formulations.

Synthesis of cellulose nitrates from Miscanthus × giganteus var. KAMIS cellulose obtained under pilot production conditions

The work is devoted to the study of a novel national raw material resource Miscanthus × Giganteus var. KAMIS, which is positioned as one of the most promising natural sources for obtaining high-quality cellulose for the purpose of its further chemical functionalisation. A batch of technical cellulose isolated from raw materials under pilot production conditions using the nitric acid method having a cellulose content of 50.2% was characterized by high α-cellulose mass fraction (92.8%) and degree of polymerisation (1200) values. On the basis of the pilot batch of technical cellulose, a sample of cellulose nitrates offering basic functional properties was obtained: mass fraction of nitrogen – 11.18%; viscosity – 48 MPa·s; solubility – 94%. The synthesised sample is characterized by extremely high solubility in acetone, confirming the production of cellulose nitric acid esters, and a high yield of 150%. IR-Fourier spectroscopy was used to identify the main functional groups in the experimental batch of technical cellulose (3384, 2902, 1639, 1428, 1370, 1319, 1161, 700–500 cm-1) and in a sample of cellulose nitrates (1659, 1278, 834, 746, 683 cm-1). Acorresponding affiliation to cellulose and cellulose nitric acid esters was established. The structural and morphological features of the fibres of the experimental batch of technical cellulose and a sample of cellulose nitrates were characterised using scanning electron microscopy. Combined methods of thermogravimetric and differential thermal analyses were used to establish high initial temperature (197 °C) and specific heat of decomposition (6.92 kJ/g) values at the beginning of intensive decomposition. The obtained results substantiate the possibility to chemically functionalise cellulose isolated from a new alternative source into cellulose nitric acid esters with satisfactory functional properties.

Doping HTPB binder with cellulose nitrate: A promising strategy for advanced energetic material applications

This study explored the characteristics of hydroxyl-terminated polybutadiene (HTPB) supplemented with cellulose nitrate (NC), as a high-energy density binder. The effect of NC doping and its content on the chemical structure, morphology, energetic, and thermokinetic behavior of HTPB–NC binder highlighted attractive features such as good compatibility, improved density, homogeneity, and fiber dispersion. Additionally, HTPB–NC exhibited excellent thermal stability with significant energy release and notable chemical reactivity. These interesting properties of the HTPB–NC binder, provide evidence for the excellent synergistic effect between HTPB and NC, which could promote its application in the next generation of energetic propellant formulations.

Effect of sulfuric residual acid on the physicochemical properties, thermal behavior, and decomposition kinetics of nitrocellulose

The acid remaining in the nitrocellulose (NC) during the production process have some influence on its structure and stability. Herein, physicochemical properties, thermal behavior, and decomposition kinetics of NC before and after sulfuric acid treatment were thoroughly investigated using a series of analytical instruments in this paper. It is found that the nitrogen content and relative molecular weight of NC-0.968% that undergoing impregnation with sulfuric acid and drying is decreased by 0.58% and 16% (decreasing rate), respectively, suggesting that the presence of excess sulfuric acid leads to denitrification of NC at room temperature as well as breakage of the glucoside bond, with a greater effect on the latter. Moreover, the results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and dynamic vapor sorption (DVS) indicate that the presence of sulfuric acid did not cause significant changes in the crystalline structure of NC, but severely damage the microscopic morphology, resulting in a large number of micropores appearing on its fiber surface, which enhances the hygroscopicity of NC. In addition, the combined Model-based kinetic results indicate that the decomposition reaction process of NC- 0.968% has a step one more than that of pure NC, which is attributed to the acid-catalyzed denitrification of NC and the breaking of glucoside bonds. Combined with the experimental results of TG-DSC-FITR, it shows that the presence of acid mainly affects the initial decomposition process of NC, while the fracture of the glucose ring frame and oxygen bridge in the NC molecular structure is more dependent on the action of NO2 and the decomposition temperature.

Influence of humidity on the decomposition process of double base rocket propellant

The decomposition mechanisms of the polymer cellulose nitrate (NC) which is used in double base (DB) rocket propellants, have been extensively studied, and the influence of storage temperature on the lifetime of these energetic formulations is well known. However, the impact of humidity and water on the polymer decomposition process is poorly understood. This paper studies the influence of humidity on the decomposition chemistry of NC and its impact on shelf life. Stabiliser consumption was first analysed by ageing the propellant in sealed vials at different humidity levels for 7 days at an isothermal temperature of 90 °C. Samples were also analysed using heat flow calorimetry (HFC) at isothermal temperatures of 80 °C, 90 °C, and 100 °C. The results indicates that stabiliser depletion increases with increasing water content. Life assessment calculations (AOP 48 ed2) show that increasing the absolute humidity from 6 to 22 g m-3 will decrease the propellant life from 11 to 6 years (25 °C equivalents). The HFC results follow the same trend as the stabiliser depletion where greater absolute humidity increases the heat flow by up to 400 %. Unlike the pass/fail criteria for stabiliser depletion, the HFC samples passed the 10-year (25 °C equivalent) life criteria (STANAG 4582). A multi-temperature (80, 90, 100 °C) kinetic analysis of the initial heat flow showed that the heat flow rate increased with increasing humidity, but the activation energy for all humidity levels remained at 131 (± 3) kJ mol−1.

Highly surface-selective nitration of cellulose nanofibers under mildly acidic reaction conditions

Cellulose nitrate (CN) is used in numerous industrial materials, such as propellants, lacquers, and plastics, exploiting its highly flammable, hydrophobic, and plastic characters. The downsizing of cellulose nitrate fibers may enhance their properties. Although a direct nitration of cellulose nanofiber (CNF) is a prospective method for preparing nanosized CN materials, it is difficult because of the susceptibility of CNF to acids. In the previous study, we prepared nitrated cellulose nanofibers (NCNFs) using never-dried CNFs and relatively dilute H2SO4, obtaining a high yield and degree of substitution. In this study, we describe a novel highly surface-selective nitration method using dried CNFs. To prevent the acid hydrolysis of the CNFs, mildly acidic conditions (acetic acid/acetic anhydride/HNO3) were used instead of the conventional mixed-acid systems. Solid- and gel-state NMR studies revealed that the original crystalline structure of the produced NCNF core was retained, even after nitration, whereas the cellulose molecules on the NCNF surface were completely converted to cellulose pernitrates. The NCNFs exhibited morphologies comprising thin nanofiber diameters of approximately 10–50 nm with high specific surface areas of approximately 260 m2 g–1. Thus, unique core–shell NCNFs were prepared, potentially leading to the development of CNF derivatives with novel applications and functions.Graphical abstract