Sorption of nitroglycerine from solution by granular nitrocellulose

Two nitrocelluloses of 12.7 and 14.0% nitrogen contents were prepared and fractionated to give samples having M?_n values in the range 2,200—388,000. The effect of chain-length of the nitrocellulose samples, having the same nitrogen content, on the sorption of nitroglycerine from n-hexane solution was investigated by means of partition equilibrium experiments. The separate effect of nitrogen content on sorption of nitroglycerine was determined by comparison of sorption isotherms for samples of similar molecular weight but different nitrogen contents. The amount of nitroglycerine taken up was greater for the lower nitrogen content samples, but sorption was not influenced by the molecular weight of the nitrocellulose. The results are discussed in terms of the molecular structure of the nitrocellulose samples, which is determined by the orientation and spacing of the chains in the crystalline and amorphous regions.     

丙二酸二乙酯与邻苯二甲酸二烯丙酯复合改性酚醛树脂

以甲醛和苯酚为原料、有机酯[由丙二酸二乙酯和DAP(邻苯二甲酸二烯丙酯)组成]为改性剂,制备碱性PF(酚醛树脂);然后采用DMA(动态热机械分析)法、DSC(差示扫描量热)法、FT-IR(红外光谱)法和TGA(热失重分析)法等对改性PF的固化机制、反应动力学等进行了表征和分析。研究结果表明:随着有机酯用量的不断增加,改性PF的储能模量、损耗模量和损耗因子(tanδ)无明显的规律性,固化温度随之下降;有机酯可促进改性PF的凝胶固化,并且是通过快速促进PF分子的活性中间体亚甲基醌来实现的。有机酯用量虽对改性PF的耐热性影响不大,但相应胶合板的胶接强度有所降低;当m(有机酯)=12 g、m(丙二酸二乙酯)∶m(DAP)=1∶1时,改性PF的综合性能相对最好。     

The birefringence of nitrocellulose fibers and pastes

The optical path difference of nitrocellulose fibers and pastes were measured on the polarizing microscope using three different compensation techniques, and a method is suggested for converting these path differences into birefringencies. By taking measurements on a sufficiently large number of fibers it is possible to estimate the average nitrogen content with an accuracy approaching that achieved by other methods on much larger samples. The distribution of nitrogen between individual fibers shows that material prepared by the displacement process differs from that made by the mechanical process and indicates that denitration occurs during displacement process manufacture. Solvents and plasticizers either increase or decrease the birefringence, and the structure of nitrocellulose pastes is discussed.     

The interaction of dibutyl phthalate with 12.6 % N nitrocellulose

The interaction of the plasticiser dibutyl phthalate with 12.6 % N nitrocellulose has been studied using dielectric relaxation. The plasticiser is adsorbed onto the nitrocellulose forming multilayers as more dibutyl phthalate is added, eventually forming a liquid layer of plasticiser. The behaviour found is similar to that observed for the plasticisation of cellulose acetate with dibutyl phthalate and for nitrocellulose plasticised with nitroglycerine (glycerol trintrate). Copyright © British Crown Copyright 2004 Dstl. Published with the permission of the Controller of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Autoradiographic determination of the di-n-butyl phthalate concentration profile in a nitrocellulose matrix

The concentration profile of a deterrent (di-n-butyl phthalate) which had been diffused into a nitrocellulose sphere (ball propellant) containing nitroglycerin was studied by means of autoradiography. Results indicate a level concentration part way into the sphere with an abrupt dropoff in concentration. An explanation for this type of concentration profile is offered based on hydrogen bonding of the deterrent carbonyl group with unesterified hydroxyl groups in nitrocellulose.     

Selective sorption of diethyl phthalate on pH-responsive,molecularly imprinted polymeric adsorbents

ABSTRACT

A novel synthetic route for preparation of pH-responsive molecularly imprinted adsorbents for separation of diethyl phthalate (DEP) is proposed. Polymers were synthesized using acrylic acid (AAc) and methyl methacrylate (MMA) crosslinked using ethylene glycol dimethacrylate (EGDMA) or divinylbenzene (DVB). The carried out tests revealed the pH-driven recognition of synthesized sorbents toward DEP. It was found that sorbents derived from mixture of 30% AAc:MMA (1:1) and 70 wt.% of DVB in the presence of 7 wt.% of template were the best. The DEP sorption took the highest value (85 mg g^?1) at pH = 5, while desorption with extent of 92% was the most efficient at pH = 8.     

Sorption of cadmium ions with chemisorbing polymer fibers

The effect of the structure and functional composition of amine-containing chemisorption fibers based on grafted copolymers on the regularities of cadmium-ion sorption was revealed. The main kinetic and capacity parameters of sorption were determined. The possibility of reaching a high degree of extraction of cadmium ions from low-concentration solutions was shown.     

Preparation and characterization of octyl and octadecyl-modified mesoporous SBA-15 silica molecular sieves for adsorption of dimethyl phthalate and diethyl phthalate

Octyl (C₈) or octadecyl (C₁₈)-modified mesoporous SBA-15 silica molecular sieves have been prepared by adding SBA-15 silica molecular sieves to octyltrimethoxysilane or octadecyltrimethoxysilane in toluene at 100 °C, and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), nitrogen adsorption–desorption measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). FTIR spectra shows the presence of methylene (–CH₂–) and methyl (–CH₃) bands on the modified SBA-15. Powder XRD data indicate the structure of modified SBA-15 with octyl or octadecyl groups still remains two-dimensional hexagonal mesostructrure. Brunauer–Emmett–Teller (BET) surface area analysis presents that surface area of octyl- and octadeyl-SBA-15 changed from 647 to 449 and 321 m² g⁻¹, respectively, and SEM images show the decreased size of modified SBA-15 particles. TEM images of modified materials with alkyl groups show the structures remain the same as the parent SBA-15 silica. We also have studied the adsorption capacity of the materials to phthalate esters (dimethyl and diethyl phthalate) by dynamic adsorption experiments on high performance liquid chromatography (HPLC). It is found that the modified materials can increase the adsorption of phthalate esters compared to SBA-15 particles, and the adsorption capacity increased with the increased length of alkyl chain on SBA-15. The maximum dynamic adsorption capacity for diethyl phthalate was 3.9 (C₈-SBA-15) or 4.3 (C₁₈-SBA-15) times higher than that of SBA-15 particles, respectively. The results indicate that alkyl SBA-15 particles could be used for enrichment of phthalate esters in water samples before the further analysis.     

Sorption of oil emulsified in water on oil palm fibers

Oil palm empty fruit bunch (OPEFB) fibers were modified with silylation by trimethylchlorosilane (TMCS) and diethyldichlorosilane (DEDCS). The investigation was carried out at room temperature at a concentration of 1, 3, 5, and 9%wt and aging time of 3, 5, and 9 hr. Fiber modification was conducted by leaching out surface contaminants resulting in open porous surface. An optimal condition to reach the equilibrium silylation reaction was undertaken at a concentration of 1%wt and aging time of 3 hr. The sorption of oil which was emulsified in water on fresh and silylated OPEFB fibers fit Temkin and Langmuir isotherms, respectively.     

Preparation of polyaniline montmorillonite clay composites for the removal of diethyl hexyl phthalate from aqueous solutions

The work presents the synthesis of polyaniline functionalized montmorillonite (PANI/MMT) clay composites and evaluation of their performance as an adsorbent for the mitigation of toxic diethyl hexyl phthalate (DEHP) from water. The formation of composite was confirmed by different analytical techniques such as FTIR, zeta potential analysis, XRD, SEM, and AFM. The adsorption capacity of PANI/MMT was superior to MMT. DEHP followed partition mechanism on PANI/MMT whereas MMT favored surface adsorption mechanism. The performance of PANI/MMT for DEHP removal was unaffected by the change in pH of solution, change in salinity, and hardness contents in aqueous system and consecutive adsorption desorption cycles compared to MMT. Furthermore, both PANI/MMT and MMT exhibited greater adsorption capacities as compared to the previously published work and showed satisfactory performance in real water samples.     

Sorption studies of the structure of carbon fibers derived from pitch

Conclusions -- It has been found that the investigated pitch carbon fibers are ultra- and microporous adsorbents with a strongly developed surface.-- The studied fibers display clearly expressed molecular-sieve properties.-- With increase in activation time, the size and volume of the pores and the specific surface of the specimens increase, while the chemical activity of the surface changes only slightly.Translated from Khimicheskie Volokna, No. 2, pp. 40–41, March–April, 1993.     

Sorption properties of the composite fibers made of PAN and chitosan

A composite fiber of polyacrylonitrile (PAN) and chitosan was obtained by spinning the mixture of PAN/chitosan with a certain amount of diluted acetic acid as a plasticizer. Water plasticizes the PAN and acetic acid plasticizes the chitosan. The fiber showed a porous and fibrillar structure, which could be converted easily into pulplike short fiber by pulping. PAN/chitosan pulp showed a much higher amount of uptake for acid dye than that of either powdery chitosan or activated carbon. It is considered that this better sorption capacity of the composite fiber results from the relatively large surface area attributed to its pulplike shape. The adsorption behavior of the composite fiber was considerably affected by temperature and pH because the adsorption is exothermic and proceeds by an acid–base reaction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2505–2511, 2002     

Sorption and recovery of heavy oils using carbonized fir fibers and recycling

Fibers extracted from fir trees (Abis sachalinensis Fr. Schm) and carbonized at either 380 or 900°C were found to have a high performance for sorption, recovery and recycling of heavy oils, even the viscous ones. Sorption capacity showed strong dependence on bulk density of carbonized fibers, suggesting the importance of the space formed among entangled fibers: 60-80 g/g for bulk density of ca. 6 kg/m³ and 10-20 g/g for density of ca. 40 kg/m³. The sorption capacity of carbonized fir fibers for a less viscous heavy oil was almost comparable to that of exfoliated graphite which was also reported to have high capacity. For viscous oil, however, carbonized fir fibers had higher sorption capacities than exfoliated graphite, particularly when the bulk densities are high. Less viscous heavy oil could be recovered by simple filtration under suction and the fibers could be reused for the sorption of oil, although the sorption capacity decreased with recycling. Their recycling performance was also strongly dependent on their bulk density: the sorption capacity of 6 kg/m³ fibers after the eighth cycle became less than 60% from that of the first cycle, but for 35 kg/m³ fibers it was more than 90%. Viscous oil could be recovered only by washing with n-hexane and also with less viscous oil. After washing the fir fibers could be reused for the sorption of oil.     

酯化法合成戊二酸乙酯

以戊二酸和无水乙醇为原料，硫酸氢钠为催化剂合成戊二酸二乙酯，考察了影响收率的各种因素，确定了最佳反应条件为：戊二酸用量0．1mol时，无水乙醇与戊二酸的物质的量比为6．0，2．0g催化剂，25mL环乙烷作带水剂，反应时间1．5h，收率达79．1％，结果表明，硫酸氢钠是合成戊二酸二乙酯的优良催化剂。     

Methylcentralite concentration profiles in monoperforated extruded nitrocellulose and nitrocellulose/nitroglycerine propellant grains by Raman microspectroscopy

Raman microscopy was used to determine the methylcentralite (MC) concentration profiles diffused into single-base (nitrocellulose) (NC) and double-based (nitrocellulose/nitroglycerine) (NC/NG) small-arms propellant grains. External and internal concentration profiles were determined by measuring the concentration of MC relative to the NC and NC/NG at 5-μm intervals into the grain from the edge inward and the perforation edge outward. The external profile was constant with a diffusion and interaction mechanism, i.e., a level concentration of deterrent through the outer region of the grain followed by a gradual dropoff in concentration with distance into the grains, whereas the internal profile was found to be dependent on perforation size with either a diffusion and interaction mechanism profile or a gradual decrease in concentration profile.     

Determination of degree of nitration of nitrocellulose by refractometry

Nitrocellulose (NC) films, when dried on a rigid substrate, tend to be biaxial and thus exhibit two refractive indices. The absolute difference between these indices has been found to provide an accurate measure of the degree of nitration of NC. A film of NC is cast from a 1% solution in butyl acetate to provide a film about 0.5 mil thick. The dry film, when placed in an Abbé-3L refractometer, gives two white lines which go to extinction alternately upon rotation of a cap analyzer through the east–west (EW) and north–south (NS) directions. Refractive index measurements are made using the line visible in each direction of the analyzer. The absolute difference between the two indices is related to the degree of nitration through standard curves for various grades of NC. The standard deviation for the proposed method was found to be ±0.01% N.     

The interactions and partitioning of low molecular weight polyethylene glycols and diethyl phthalate in ethylcellulose/hydroxypropyl methylcellulose blends

The interactions and partitioning of diethyl phthalate and low molecular weight polyethylene-glycols in blends of ethylcellulose/hydroxypropyl methylcellulose have been studied. Both plasticizers were shown to diffuse in both phases according to the overall volume composition. The plasticizers interacted preferentially with one polymer component of the blend as predicted from studies of the individual polymers. Diethyl phthalate, a preferential plasticizer for ethylcellulose, demonstrated increased partitioning in the ethylcellulose-rich phase only at 80/20 w/w ethylcellulose/hydroxypropyl methylcellulose compositions. Polyethylene glycols, PEG200 and PEG400, preferential plasticizers for hydroxypropyl methylcellulose, showed increased partitioning in the hydroxypropyl-methycellulose-rich phase also in blends containing 80% w/w ethylcellulose. The general effect of the mechanism and kinetics of the phase separation of the blend on the plasticizer partitioning has also been discussed.     

Grafting of methyl methacrylate to nitrocellulose by ceric ions

Studies were carried out on grafting of various vinyl monomers to nitrocellulose by ceric ions. It was observed that graft copolymerization occurred only with methyl methacrylate (MMA) and methyl acrylate monomer. The variables such as initiator concentration, monomer concentration, time of grafting, and nitrocellulose content on grafting of MMA are discussed. By hydrolyzing away the nitrocellulose backbone, the grafted poly(methyl methacrylate) branches were isolated and the >c?o peak at 1740 cm^?1 in the infrared spectra of these isolated branches gave definite evidence of grafting. The molecular weight of isolated branches has been determined by viscometry. The probable mechanism of grafting may be at the α-carbon atom of primary alcohol or at a C₂-C₃ glycol group of the anhydro glucose unit or at the hemiacetal group of the end unit of nitrocellulose, as nitrocellulose is formed by the partial nitration of cotton cellulose.     

Microbial attack of nitrocellulose

This is a study dealing with the use of a microorganism for partial denitration of the surface of nitrocellulose-based small arms propellants, in order to gain burning rate control. An organism, Aspergillus fumigatus, was found to grow on pyroxylin suspended in a nitrogen deficient, carbon-containing nutrient medium. No growth was observed under the same conditions when carbon was absent. This would indicate that the organism utilized nitrogen from nitrocellulose without attacking the carbon backbone. Further, mechanism studies indicated that the organism did not utilize the nitrogen directly from nitrocellulose, but rather relied on a hydrolysis reaction for a source of nitrogen.