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.     

Temperature effects on the birefringence of nitrocellulose and nitrocellulose/nitroglycerine mixtures

Changes in the optical path difference of nitrocellulose fibres of varying degrees of substitution over the temperature range ?120°C to 130°C are interpreted as due to conformational changes in the primary nitrate group. Changes in path difference of nitrocellulose/nitroglycerine paste fibres over the same temperature range indicate an irreversible annealing effect and a change in the nitrocellulose structure. Propellants made from nitrocellulose and nitroglycerine show similar changes and it is concluded that submicroscopic fibrils are present even though no fibres are visible. When fibres are visible they show a banded structure, the nature of which is discussed.     

Thermoreversible gelation of nitrocellulose solutions

Thermoreversible gelation of concentrated solutions of nitrocellulose was examined. The sol–gel transition diagrams were established using the ball‐drop method. The critical gel concentrations (C_gel), defined as the lowest concentration for gelation to occur, are approximately proportional to the reciprocal of the molecular weight of nitrocellulose. In addition, the values of C_gel[η] lie in the concentrated regime where entanglement effects are present. These facts suggest that the entanglement of polymer chains is a necessary condition for the formation of nitrocellulose gels. Moreover, the association of polymer segments is identified as another factor affecting the gel stability. This is evidenced by both the enhancement of the gel stability in poor solvents and the large enthalpy of mixing at low temperatures. Because of the presence of the association, the number of polymer chains in a junction point is larger than two, which is the value predicted by assuming entanglements as the only factor responsible for gelation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4000–4008, 2003     

谈釉下五彩瓷装饰的色彩表现

色彩表现是釉下五彩瓷装饰得以形成的关键因素,釉下五彩瓷装饰风格大致分为工笔和写意两种,均十分重视色彩的表现与运用,具有强烈的形式、意象和工艺之美。     

Perceived lightness of chromatic object colors including highly saturated colors

A model was formulated for predicting the Helmholtz-Kohlrausch effect or the Y tristimulus values for chromatic object colors with the same perceived lightness (L/Y ratios). the model was extended from the previous one in Color Res. Appl. 16 , 16-25 (1991), making it possible to estimate the Helmholtz-Kohlrausch effect on chromatic object colors with any Munsell Value. By analyzing the two experiments by Wyszecki and by Sanders and Wyszecki using the extended model, the model parameters were estimated for each experiment. By using each of the two estimated equations, L/Y ratios for Y = 20.0 were predicted in the whole chromaticity gamut corresponding to the two kinds of experimental results. the derived contour lines for equal L/Y ratios correlated well with those estimated directly from each experimental data. In addition, extrapolated L/Y ratios for spectral colors with Y = 20.0 showed very good agreement with the luminance ratios for equally bright spectral stimuli, so-called brightness/luminance (B/L) ratios, derived from the luminous efficiency functions V_b,2(Λ) by CIE TC 1-02 and V_judd(Λ) proposed by D. B. Judd.     

硝化纤维乳液的制备途径

简要介绍了用分散、反相乳化及化学改性法制备硝化纤维乳液。     

Alcogel and aerogel of nitrocellulose formed in nitrocellulose/acetone/ethanol ternary system

Nitrocellulose (NC) alcogels were formed in NC/acetone/ethanol ternary system and NC aerogels were prepared from NC alcogels after drying under supercritical CO₂ (scCO2). NC alcogel with lower modulus was formed in the ternary system with a higher ethanol ratio. The densities and porosities of NC aerogels were related directly to the initial ethanol content. The NC aerogels clearly retained the crystalline structure of NC powder. NC aerogels that were formed in the system with higher ethanol content had larger pore size distribution range, larger average pore diameter, and larger mesopore and macropore volume. The thermal decomposition of NC aerogel was more accelerated and more acute compared with NC powders.     

Optimal fluorescent colors

This article poses and discusses a maximization problem: for a given chromaticity, and in a given illumination, how light a fluorescent color is possible. The article does not present a solution, but does offer a conjecture that for many illuminants and many chromaticities the greatest lightness is achieved by a simple form of bispectral function. The output is in two points plus a tail, so we call it a “PPT” function. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 85 – 91, 2007     

Greyness of process colors

A method of measuring and comparing the greyness (unwanted spectral absorptions) of process colorants has been developed. The method uses the 1976 CIELAB color space and, in effect, makes a chromatic match of a trial colorant with a reference Cromalin®^? color and then calculates greyness from the difference of their values of CIE 1976 lightness L*.     

Thermochromism of fluorescent colors

Fluorescence (sometimes called rapid luminescence or just luminescence) has been scientifically studied for 150 years. Recent advances in daylight simulators, ultraviolet filters, and measurement devices (for example, advances in the commercial two‐monochromator measurement devices) have made it possible to study this phenomenon more accurately. Many factors affect the color of a fluorescent object. One of these factors is the temperature of the sample. It is known that, for example, the reflectance of the nonfluorescent ceramic color reference tiles used for calibration of colorimeters and spectrophotometers is temperature dependent. This phenomenon is called thermochromism, which means a reversible change of a color of the sample as a function of temperature. The phenomenon can also be detected in fluorescent colors, although fluorescent samples show quite different thermochromic properties that have not been extensively studied and are partly unknown. In this article we first discuss the thermochromism of nonfluorescent samples. We consider the meaning of thermochromism for fluorescent color measurements. Novel experimental data are provided and the temperature‐dependent changes in samples' radiance spectra are analyzed and proven to be significant. In some fluorescent samples the thermochromic changes can be as high as 4 times the thermochromic changes in some nonfluorescent samples in the same temperature scale (e.g., red fluorescent paint sample versus red ceramic sample, with equivalent temperature changes). In addition, a two‐component thermochromic model is introduced to discuss the phenomenon of thermochromism more closely. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 163–171, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20104     

Exploring compatible facility colors and associated colors for outdoor recreational spaces

Many studies have demonstrated that people associate customary colors to buildings and facilities, and these colors significantly influence people's evaluations of the environment. However, whether customary colors also exist in the environments where building facilities have been installed is rarely discussed. Using correspondence analysis, this study explored the colors associated with five different outdoor recreational spaces (theme parks, national parks, recreational farms, riverside parks, and historic heritage sites) and fitted facility colors. The study acquired a valid sample of 103 college students and demonstrated that people judge colors in recreational spaces according to past experience and their impressions of the spaces. Hue, value, and saturation are not independent factors for color consideration; a color with a specific value and saturation is particularly suitable for some spaces. In addition, the color associated with an environment and the compatible color for facilities are not exactly the same. The possible factors that influence different environment colors and future research directions were also discussed. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 424–432, 2016     

Membrane potentials of thin nitrocellulose membranes

The membrane potentials of thin (300–1300 A.) nitrocellulose (Parlodion) membranes have been investigated. Measurements were made in a Lucite cell by use of calomel electrodes with 0.05N KCl and 0.1N KCl. Variables having an influence on membrane structure, such as solvent polarity, temperature, and thickness, have been studied in relation to membrane potential. The range of potentials observed for Parlodion (2.1–9.2 mv.) is believed to be the result of differences in the orientation of the nitrocellulose molecules (and their accompanying electrochemically active carboxyl groups) in the membrane structure.     

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.     

Hygroscopicity of nitrocellulose with different nitrogen content

Research on the hygroscopic behavior of NC is essential because it affects the mechanical properties, combustion properties, and safe storage of NC-based products. In this study, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) are used to characterize the chemical structure, crystal structure, and microscopic morphology of NC, respectively. The moisture adsorption isotherms of NC fibers with different nitrogen content are determined by dynamic vapor sorption (DVS) and fitted with Hailwood-Horrobin (H−H) and Guggenheim-Anderson-de Boer (GAB) models. The specific surface area and surface energy of NC are also measured by inverse gas chromatography (IGC). The results show that as the nitrogen content of NC increases, the intensity of the −OH characteristic absorption peak is weakened, the crystallinity does not change much, the number of cracks and pores on the NC fiber surface increases, and the equilibrium moisture content (EMC) of the NC decreases in general. In addition, the fitting results based on the H−H and GAB models show that, under low humidity conditions, the EMC value of NC is determined by the adsorbed water content of the monolayer, which is mainly related to the −OH content in NC. However, with the increase of humidity, the EMC value of NC is gradually determined by the multilayer adsorbed water content, which is influenced by both the nitrogen content and the fiber cleavage structure. Meanwhile, the IGC results show that the surface energy of the NC consists mainly of the dispersive surface energy (values >46 mJ m⁻²), with the specific surface energy contributing approximately 25 mJ m⁻². The total surface energy of NC and the bonding strength between NC molecules and water molecules decrease with increasing nitrogen content.     

Quantitative representation of floral colors

Human and insect pollinator perceived floral colors of 81 species of angiosperms (flowering plants) from Trivandrum (Kerala, India) was represented using the CIE 1976 L*a*b* color space and color hexagon, respectively. The floral color difference among human perceived red, yellow, and blue‐hued flowers and that of each flower from its respective pure hue was calculated using the CIE ΔE 2000 formula. Human perceived floral color difference values were consistently higher than 3.5, indicating the uniqueness of floral colors. Flowers perceived red and yellow by humans were dominant and of comparable proportions. Insect pollinators perceive most of the flowers as blue‐green. Quantitative representation of human and pollinator perceived floral colors would be invaluable to understand the information broadcasted by flowers. It can form the basis of flower grading in the floriculture industry and underpin objectivity in evolving the framework for national pollinator strategies.