Comparative research on promising energetic 1,3-diazinane and 1,3-oxazinane structures

The additional carbon centers in 1,3-diazinane and 1,3-oxazinane enable them to covalently bonded geminal-explosophoric groups, leading to unique energetic properties when compared with their homologous energetic structure like RDX. In this paper, a concise synthesis and comparative studies towards 1,3,5-(trinitro1,3-diazinane-5-yl) methyl nitrate and (3,5-dinitro-1,3-oxazinan-5-yl) methyl nitrate (TNOP), two energetic 1,3-diazinane/1,3-oxazinane based promising explosive molecules, are reported. The new germinal nitro/nitroxy explosophoric moieties in the 1,3-diazinane and 1,3-oxazinane frameworks lead to novel structural and energetic properties, which have been investigated through both experimental and computational methods. Densities of the obtained compounds are 1.83 g·cm^?3 and 1.72 g·cm^?3, respectively, along with the detonation velocities of 8714 m·s^?1 and 8112 m·s^?1. The energetic properties of TNNP are comparable to those of RDX. Meanwhile, the low melting point (105 °C) and excellent insensitivity (IS﹥60 J, FS﹥360 N) of TNOP make it an ideal material for the preparation of melt-cast explosives.     

The Young's modulus of a microcrystalline cellulose

This research is concerned with an investigation into the determination of the micromechanical properties of particulate form of cellulose; namel microcr stalline cellulose. Using the technique of Raman spectroscop the shift in the 1095cm^–1 Raman band, characteristic of cellulose, with strain is monitored and compared to the deformation of natural cellulose fibres (flax and hemp). From the values of the shift rate of the 1095cm^–1 band for flax and hemp and the experimentally-determined value for microcrystalline cellulose the value for the Young's modulus of microcrystalline cellulose was estimated to be 25±4GPa. It has been shown that this value is consistent with the measured degree of crystallinity of microcrystalline cellulose. Theoretical modelling has also enabled the Young's modulus for compacted microcrystalline cellulose to be determined for fibres in either 2-D in-plane and 3-D arrangements. These values have been show to be consistent with recent direct measurements of the modulus of compacted material.     

Effect of wet spinning parameters on the properties of novel cellulosic fibres

Novel cellulose fibres (Biocelsol) were spun by traditional wet spinning technique from the alkaline solution prepared by dissolving enzyme treated pulp directly into aqueous sodium zincate (ZnO/NaOH). The spinning dope contained 6 wt.% of cellulose, 7.8 wt.% of sodium hydroxide (NaOH) and 0.84 wt.% of zinc oxide (ZnO). The fibres were spun into 5% and 15% sulphuric acid (H₂SO₄) baths containing 10% sodium sulphate (Na₂SO₄). The highest fibre tenacity obtained was 1.8 cNdtex⁻¹ with elongation of 15% and titre of 1.4 dtex. Average molecular weights and shape of molecular weight distribution curves of the celluloses from the novel wet spun cellulosic fibre and from the commercial viscose fibre were close to each other.     

The study of regenerated cellulose films toughened with thermoplastic polyurethane elastomers

Regenerated cellulose blend film with thermoplastic polyurethane (TPU) was successfully prepared by coagulating cellulose/TPU solution with water in the presence of a thermoplastic polyurethane elastomer (TPU). Compared with pristine regenerated cellulose film, the toughness and thermal stability of the blend film was significantly improved. For example, the elongation at break was increased from 11% of pristine cellulose film to 51% of blend film with 20 wt. % TPU. The 50% weight loss temperature of this blend film was increased by 33 °C compared to neat cellulose. The relaxation transition temperature of cellulose was decreased with the addition of TPU through dynamic mechanical thermal analysis. The oxygen permeability was decreased from 2.3 × 10⁻¹⁰ cm³ cm/cm² s Pa of pristine cellulose film to 0.08 × 10⁻¹⁰ cm³ cm/cm² s Pa of the blend film with 20 wt.%. TPU The X-ray diffraction spectra showed that the crystallinity of cellulose decreased with incorporation of TPU. The images of scanning electron microscope discovered that there was good compatibility between cellulose and TPU. TPU was nano-dispersed in cellulose matrix. The blend film still maintained quite good transparency.     

Molecular weight-dependent anticoagulation activity of sulfated cellulose derivatives

This work is to examine the molecular weight (MW)-anticoagulation activity relationship of sulfated cellulose derivatives (cellulose sulfates, CS). The initial CS with a degree of substitution (1.59) was prepared by homogeneous sulfation of microcrystalline cellulose in an ionic liquid [C₄mim]Cl. It was then hydrolyzed in a dilute acidic solution and separated into four MW fractions of 59, 23, 10 × 10³ g/mol and below 2.7 × 10³ g/mol. The anticoagulation activities based on in vitro assays of coagulation time and coagulation factors in human plasma showed a positive correlation with the MW of CS, while the activity assay of clotting time in rats exhibited a negative correlation with the MW 10–59 × 10³ g/mol, and the fraction with a MW <2.7 × 10³ g/mol exhibited a more moderate and durable activity. The results indicate that MW is a major factor on the anticoagulant properties of CS derivatives and higher MW range is favorable for in vitro, and lower MW suitable for in vivo applications.     

Effect of structural and physico-chemical features of cellulosic substrates on the efficiency of enzymatic hydrolysis

Effects of major physicochemical and structural parameters of cellulose on the rate and degree of its enzymatic hydrolysis were tested with cellulosic materials from various sources. Some different pretreatments were: mechanical (milling), physical (X-ray irradiation), and chemical (cadoxen, H₃PO₄, H₂SO₄, NaOH, Fe²+/H₂O₂). The average size of cellulose particles and its degree of polymerization had little effect on the efficiency of enzymatic hydrolysis. For samples of pure cellulose (cotton linter, microcrystalline cellulose, α-cellulose), increase in the specific surface area accessible to protein molecules and decrease in the crystallinity index accelerated the enzymatic hydrolysis (the correlation coefficients were 0.89 and 0.92, respectively). In the case of lignocellulose (bagasse), a quantitative linear relationship only between specific surface area and reactivity was observed.     

Aggregation and sedimentation stability of microcrystalline cellulose suspensions in aqueous aluminum nitrate solutions

The aggregation and sedimentation stability of dilute suspensions of microcrystalline cellulose in aqueous solutions of Al(NO₃)₃(2 × 10⁻⁵–2 × 10⁻³ mol/l) is studied by the photometric method at pH 2–11. It is found that, in the absence of Al(NO₃)₃, microcrystalline cellulose suspensions are stable with respect to aggregation throughout the pH range in question. The addition of Al(NO₃)₃ induces the coagulation and accelerates the sedimentation of microcrystalline cellulose aggregates. At all concentrations of Al(NO₃)₃, the maximum loss in stability is observed at pH 7–9. Original Russian Text ? P.M. Mosur, A.V. Lorentsson, Yu.M. Chernoberezhskii, 2009, published in Kolloidnyi Zhurnal, 2009, Vol. 71, No. 4, pp. 566–568.     

Characteristics of methyl cellulose-NH4NO3-PEG electrolyte and application in fuel cells

We report the viability of methyl cellulose (MC) as a membrane in a polymer electrolyte membrane fuel cell (PEMFC). Methyl cellulose serves as the polymer host, ammonium nitrate (NH₄NO₃) as the doping salt and poly(ethylene glycol) (PEG) as plasticizer. Conductivity measurement was carried out using electrochemical impedance spectroscopy. The room temperature conductivity of pure MC film is ( 3.08±0.63 ) ×10 ^{- 11}S cm ^{- 1} \left( {{3}.0{8}\pm 0.{63}} \right) \times {1}{0^{ - {11}}}{\hbox{S}}\,{\hbox{c}}{{\hbox{m}}^{ - {1}}} . The conductivity increased to ( 2.10±0.37 ) ×10 ^{- 6}S cm ^{- 1} \left( {{2}.{1}0\pm 0.{37}} \right) \times {1}{0^{ - {6}}}{\hbox{S}}\,{\hbox{c}}{{\hbox{m}}^{ - {1}}} on addition of 25 wt.% NH₄NO₃. By adding 15 wt.% of PEG 200 to the highest conducting sample in the MC-NH₄NO₃ system, the conductivity was further raised by two orders of magnitude to ( 1.14±0.37 ) ×10 ^{- 4}S cm ^{- 1} \left( {{1}.{14}\pm 0.{37}} \right) \times {1}{0^{ - {4}}}{\hbox{S}}\,{\hbox{c}}{{\hbox{m}}^{ - {1}}} . The highest conducting sample containing 15 wt.% PEG was used as membrane in PEMFC and was operated at room and elevated temperatures. From voltage-current density characteristics, the short circuit current density was 31.52 mA cm⁻² at room temperature (25 °C).     

Acetylation of cellulose in LiCl-<Emphasis Type="Italic">N,N</Emphasis>-dimethylacetamide: first report on the correlation between the reaction efficiency and the aggregation number of dissolved cellulose

The acylation of three cellulose samples by acetic anhydride, Ac₂O, in the solvent system LiCl/N,N-dimethylacetamide, DMAc (4 h, 110 °C), has been revisited in order to investigate the dependence of the reaction efficiency on the structural characteristics of cellulose, and its aggregation in solution. The cellulose samples employed included microcrystalline, MCC; mercerized cotton linters, M-cotton, and mercerized sisal, M-sisal. The reaction efficiency expresses the relationship between the degree of substitution, DS, of the ester obtained, and the molar ratio Ac₂O/AGU (anhydroglucose unit of the biopolymer); 100% efficiency means obtaining DS = 3 at Ac₂O/AGU = 3. For all celluloses, the dependence of DS on Ac₂O/AGU is described by an exponential decay equation: DS = DS_o − Ae^{−[(Ac2O/AGU)/B]}; (A) and (B) are regression coefficients, and DS_o is the calculated maximum degree of substitution, achieved under the conditions of each experiment. Values of (B) are clearly dependent on the cellulose employed: B_(M-cotton) > B_(M-sisal) > B_(MCC); they correlate qualitatively with the degree of polymerization of cellulose, and linearly with the aggregation number, N_agg, of the dissolved biopolymer, as calculated from static light scattering measurements: (B) = 1.709 + 0.034 N_agg. To our knowledge, this is the first report on the latter correlation; it shows the importance of the physical state of dissolved cellulose, and serves to explain, in part, the need to use distinct reaction conditions for MCC and fibrous celluloses, in particular Ac₂O/AGU, time, temperature.     

Self-reinforced cellulose nanocomposites

A self-reinforced cellulosic material was produced exclusively from regenerated cellulose microcrystals. The level of reinforcement was controlled by tailoring the crystallinity of cellulose by controlling the dissolution of microcrystalline cellulose (MCC) before its regeneration process. After the cellulose regeneration a self-reinforced material was obtained in which cellulose crystals reinforced amorphous cellulose. This structure was produced by dissolution of MCC in a non-derivatising cosolvent N,N-dimethylacetamide/LiCl followed by subsequent cellulose regeneration in distilled H₂O. The reduction of the overall crystallinity of self-reinforced regenerated cellulose was dependent on the dissolution time of the cellulose precursor. The crystallinity of regenerated cellulose was determined by wide angle X-ray diffraction. A reduction in crystal size from microcrystalline cellulose to regenerated cellulose was observed with increasing dissolution time in DMAc/LiCl cosolvent. The reduction in degree of crystallinity of regenerated cellulose led to a decrease in the tensile mechanical performance and thermal stability of the regenerated cellulose. The controlled dissolution of microcrystalline cellulose resulted in the modification of structural, physical, thermal properties and moisture uptake behaviour of regenerated cellulose.     

Syntheses and characterizations of allyl cellulose and glycidyl cellulose

Allyl cellulose was synthesized by reacting cellulose with allyl bromide in homogeneous LiCl/DMAc solution containing NaOH powder. The degree of substitution (DS) per anhydroglucose (AHG) unit was determined by titrating the allyl cellulose with bromine in chloroform solution, and an allyl DS of 2.80 was found. Glycidyl cellulose was then prepared by reacting this allyl cellulose with peracetic acid in methylene chloride at ambient temperature for 6 days. The measured reaction rate constant was 1.33 × 10^?3 min^?1. The glycidyl cellulose thus obtained with a glycidyl DS of 2.58 was determined by titrating the product with perchloric acid in conjunction with tetrabutylammonium iodide. The 2.58 of glycidyl DS was also confirmed by ¹H-NMR integration. Both allyl cellulose and glycidyl cellulose were analyzed and characterized with FTIR, ¹H-NMR, ¹³C-NMR, TGA, and GPC. During epoxidation of allyl cellulose, possible side reaction leading to ester formation was evidenced from the continuous increase of v_{C? O} at 1735 cm^?1 in FTIR analyses. In addition, a bimodal distribution and a decreased molecular weight for glycidyl cellulose were found from GPC data, which might suggest a possible chain scission at the cellulosic ether linkage. © 1992 John Wiley & Sons, Inc.     

Effect of the chemical treatment sequence on pineapple peel fiber: chemical composition and thermal degradation behavior

Millions of tons of fruit waste are generated globally every year from agricultural residues, which makes it essential to find alternative uses to increase their aggregate value and reduce their environmental impact. The present study aimed to explore pineapple peel as an alternative source of cellulose by evaluating its chemical composition and physical properties, which are essential for applications. A sequence of chlorine-free treatments was applied to purify the cellulose by removing noncellulosic components in the fresh pineapple peels. The cellulosic pulp was characterized regarding its chemical composition and characterized by Nuclear Magnetic Resonance (¹³C NMR), X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis to determine crystallinity, structural properties, morphology, and thermal characteristics, respectively. The results revealed that the pineapple peel amorphous segments containing hemicelluloses and lignin were extensively removed with increasing chemical treatment steps, leading to increased purity, crystallinity index, and thermal stability of the extracted cellulose pulps. The maximum thermal degradation (150 °C) and crystallinity index (80.9%) were determined for the cellulosic material obtained from the second bleaching (2B) step. The cellulose content increased from 24% in the starting material (fresh pineapple peel) to 80.9% in the bleached cellulose (2B). These results indicate that the extracted cellulose from pineapple peel has characteristic for applications such as the production of cellulose nanocrystals due to the high crystallinity.

Graphical abstract

     

Enzymatic hydrolysis of cellulose I is greatly accelerated via its conversion to the cellulose II hydrate form

Cellulose II hydrate was prepared from microcrystalline cellulose (cellulose I) via its mercerization with 5 N NaOH solution over 1 h at room temperature followed by washing with water. The structure of cellulose II hydrate changed to that of cellulose II after drying. Compared with cellulose II, cellulose II hydrate exhibited a slightly (8.5%) expanded structure only along the direction. The hydrophobic stacking sheets of the cellulose II were conserved in the cellulose II hydrate, and water molecules could be incorporated in the inflated two-chain unit cell of cellulose II hydrate. Enzymatic hydrolysis of cellulose I, cellulose II hydrate, and cellulose II was carried out at 37 °C using solutions comprising a mixture of cellulase and β-glucosidase. The hydrolysis of cellulose II hydrate proceeded much faster than the hydrolysis of the other two substrates, while the saccharification ratio of cellulose II was only slightly higher than that of cellulose I. The alkaline mercerization treatment was also applied to sugarcane bagasse. After its direct mercerization, the cellulose in bagasse was converted from cellulose I to cellulose II hydrate, and then to cellulose II after drying. Similar to in the case of microcrystalline cellulose, the rate of the enzymatic hydrolysis of the mercerized bagasse without drying (cellulose II hydrate) was much faster than the enzymatic hydrolysis of the other two substrates. Thus, the wet forms of cellulose and cellulosic biomass after mercerization, and after hydrolysis with cellulolytic enzymes, afforded superior products with extremely high degradability.     

Nitric acid preparation of cellulose from miscanthus as a nitrocellulose precursor

A nitric acid method for the preparation of cellulose from miscanthus is considered. The method consists in successive treatment of the raw material with nitric acid and sodium hydroxide and affords cellulose with properties suitable for the synthesis of cellulose nitrates. The data on the nitrogen weight fraction, the viscosity, and the solubility of cellulose nitrates from miscanthus in the alcohol-ether medium are given. The miscanthus cellulose was nitrated using an industrial sulfuric-nitric acid mixture to yield cellulose nitrate samples with characteristics close to those of colloxylin.

     

Electrochemical properties modulation of Zinc oxide nanoparticles

The influence of zinc salts precursors (nitrate, acetate, chloride) on the electroactivity of the synthesised Zinc oxide nanoparticles (ZnONPs) was investigated using Glassy carbon ZnONPs modified electrode (ZnONPs films). The precipitation synthesised ZnONPs ‘s optical, morphological, size and Structural properties were assessed by usual spectroscopical technique. The XRD data confirmed synthesis of The ZnONPs which were predominately Zincite except for the nitrate product (zincite, ZHNH). All the NPs were of smaller size with the highest diameter size of 0.25 μM and lowest 0.066 μM for nitrate and chloride NPs respectively. All had good electroactivity, with rate constants (k_s) above 1 × 10⁻² indicating fast reversible reactions, values ranged from 0.6152 to 0.7515 for Zn(NO₃) and Zn(CH₃COO)₂ respectively. Excellent opto-electric properties were observed with the nitrate product that had the highest band gaps (∼3.7 eV), DPV current(,7.57 × 10⁻⁷ A) ΔE_p, diffusion coefficient (D_e) (3.120 × 10⁻¹(cm^2/s (Ariyanta et al., 2022) [5]) and rate constant (0.62 S^-1). In addition it had the lowest resistance as indicated by the R_s value (1.13 kΩ) below the bare electrode value lowest R_ct (444.77 kΩ) and CPE (3.00 × 10⁻⁶ F). For fabrication of sensors and batteries where low resistance and conductivity are essential, ZnONPs using Nitrate is ideal.     

Syntheses,Crystal Structures,and Properties of Two Novel CL‐20‐based Cocrystals

In recent years, cocrystallization has emerged as an effective way of tuning the properties of compounds and has been widely used in the field of energetic materials. In this study, we have prepared two novel cocrystals of CL‐20 and methylimidazole, including a 1:2 CL‐20 / 2‐mercapto‐1‐methylimidazole ( 1 ) and a 1:4 CL‐20 / 4‐methyl‐5‐nitroimidazole ( 2 ). Cocrystal 1 has good physical and detonation properties (ρ₁ = 1.652 g · cm^–3, D₁ = 7073 m · s^–1, P₁ = 21.6 GPa); however, cocrystal 2 shows higher properties (ρ₂ = 1.680 g · cm^–3, D₂ = 7945 m · s^–1, P₂ = 27.4 GPa). The performance of both cocrystals is better than those of TNT. Thermal performance suggests that both the cocrystals have moderate thermal stabilities. Cocrystal 1 decomposes at 164.9 °C and cocrystal 2 has an exothermic peak at 221 °C. Both cocrystals are insensitive energetic explosives (IS > 40 J, FS > 360 N). Methylimidazole compounds are rarely used as coformers to form cocrystals with CL‐20, which possess good properties for a range of potential applications. Herein, we provide new possible directions for enriching cocrystal speciation.     

Improvement of mechanical and oxygen barrier properties of cellulose films by controlling drying conditions of regenerated cellulose hydrogels

Mechanical, thermal and oxygen barrier properties of regenerated cellulose films prepared from aqueous cellulose/alkali/urea solutions can be markedly improved by controlling the drying conditions of the films. By pre-pressing followed by vacuum drying under compression, the tensile strength, Young’s modulus, coefficient of thermal expansion and oxygen permeability of the dried films reached 263 MPa, 7.3 GPa, 10.3 ppm K⁻¹ and 0.0007 ml μm m⁻² day⁻¹ kPa⁻¹, respectively. Thus, films produced in this way show the highest performance of regenerated cellulose films with no orientation of cellulose chains reported to date. These improved properties are accompanied by a clear increase in cellulose II crystallinity from 50 to 62% during pre-pressing/press-vacuum drying process. At the same time, the film density increased from 1.45 to 1.57 g cm⁻³, and the moisture content under equilibrium conditions decreased from 14.1 to 9.8%. Hence, the aqueous alkali/urea solvent system has potential applications in producing new and environmentally friendly cellulose films with high performances through control of the drying conditions.     

Nitration of Chitin Monomer: From Glucosamine to Energetic Compound

The nitration of chitin monomer in a mixture of nitric acid and acetic anhydride was conducted and a highly nitrated (3R,4R,6R)-3-acetamido-6-((nitrooxy)methyl)tetrahydro-2H-pyran-2,4,5-triyl trinitrate (1) was obtained. Its structure was fully characterized using infrared spectroscopy, NMR spectroscopy, elemental analysis, and X-ray diffraction. Compound 1 possesses good density (ρ: 1.721 g·cm⁻³) and has comparable detonation performance (V_d: 7717 m·s⁻¹; P: 25.6 GPa) to that of nitrocellulose (NC: V_d: 7456 m·s⁻¹; P: 23 GPa; I_sp = 239 s) and microcrystalline nitrocellulose (MCNC; V_d: 7683 m·s⁻¹; P: 25 GPa; I_sp = 250 s). However, Compound 1 has much lower impact sensitivity (IS: 15 J) than the regular nitrocellulose (NC; IS: 3.2 J) and MCNC (IS: 2.8 J). Compound 1 was calculated to exhibit a good specific impulse (I_sp: 240 s), which is comparable with NC (I_sp: 239 s) and MCNC (I_sp: 250 s). By replacing the nitrocellulose with Compound 1 in typical propellants JA2, M30, and M9, the specific impulse was improved by up to 4 s. These promising properties indicate that Compound 1 has a significant potential as an energetic component in solid propellants.     

Aerocellulose: Aerogels and Aerogel-like Materials made from Cellulose

Summary: Cellulose aerogels have been prepared starting from cellulose-NMMO solutions via the classical aerogel-path. Different cellulosic materials have been tested and their influence on the properties of the product aerogels has been studied. Other parameters that have been varied include solution composition as well as the way of cellulose regeneration (solvent and temperature). More than 300 different samples were prepared and analysed. Their density is in a typical range from 0.02 g/cm³ to 0.2 g/cm³ and their internal surface area ranges from 100 m²/g to 400 m²/g. Another property investigated in detail beside density and internal surface area was the shrinkage of the cellulosic bodies during the production process.