Formation of incandescent bodies at the surface and increase in the combustion rate of condensed systems by additions of chromium compounds

Combustion, Explosion, and Shock Waves -     

Mechanical relaxations in polybutene-1 and poly-4-methylpentene-1

Dynamic mechanical measurements between — 180°C and 180°C were made on both isotropic and drawn samples of polybutene-1 (PB-1) and poly-4-methylpentene-1 (P4MB1) over a wide frequency range by the use of a torsional pendulum (0.3–3 Hz), a viscoelastic spectrometer (5–90 Hz) and ultrasonic technique (3 MHz). The relaxation peaks were identified and the associated activation energies determined from Arrhenius plots. For PB-1 it was observed that orientation reduces the height and shifts up the temperature of the α_a-peak associated with large scale main-chain motion in the amorphous regions, but has little effect on the β-peak associated with side-group motion. In addition to the α_a and β relaxations a high-temperature crystalline relaxation (α_c) is also observed in P4MP1. For both the α_c and β relaxations the mechanical loss at 45° to the draw direction is much larger than that at 90°, which indicates that shear processes are involved in these relaxations.     

Carbonization reactions of inertinite macerals in Australian coals

Widespread disagreement about the degree of reactivity of the inertinite group of macerais is related to variations in experimental conditions of assessment and failure to appreciate technological modifications imposed on similar macerals by dissimilar source materials and depositional conditions. This has resulted in the constant under-estimation of the coking potential of post-Carboniferous inertinite-rich coals by predictive methods developed for vitrinite-rich Carboniferous coals. Coking tests up to 1000 °C have been carried out on 20 coals of different rank in such a manner that coked portions of the samples could be correlated with their uncoked equivalents. It has been found that an inverse relationship exists between the level of precarbonization reflectance (PCR) of inertinite and the reflectance and bireflectance of its coke. The increase in the latter parameter is non-linear and involves a sudden jump which is taken as the boundary between reactive (high bireflectance) and non-reactive (low bireflectance) inertinite. In relation to coal rank a reactivity field for inertinite has been delineated which can be subdivided into two areas of high and moderate reactivity, respectively. On the whole, the proportion of reactive inertinite is larger than allowed for in most petrography-based coke stability calculations.     

Interface Oscillations in Boiling

Interface oscillations during boiling are studied experimentally and theoretically. The output-signal spectra of light and acoustic sensors indicate that the liquid-pressure and interface oscillations are interrelated. A model is suggested for the oscillations of a bubble growing on a heating surface, and the existence of an attractor is deduced for the first time from the solution of model equations. The data obtained enable one to determine the ranges of interface oscillation amplitude and frequency and can be used in the modeling of boiling.     

The hydration of jet cement at 20°C

Two types of jet cement having different retarders were investigated. Both physical properties such as mechanical strength, pore size distribution and porosity and chemical processes of hydration such as rate of hydration and the kind of hydrate produced upon hardening of jet cement are strongly affected by the method of the regulation of setting. The difference between the mechanical strength developed is discussed.     

Properties of aluminophosphate concretes containing various types of orthophosphoric acid

Conclusions The type of orthophosphoric acid has the maximum influence on the properties of corundum concretes, a lower influence on high-alumina concretes, and practically no influence on quartz-clay concretes. It is desirable to use wet-process orthophosphoric acid for refractory concretes. The excellent properties of concretes in the system A1₂O₃-SiO₂ based on this acid which is also cheaper enabled us to recommend it for preparing refractory concretes.The advantage of using H₃PO₄ of various types for corundum concretes is determined by the requirements placed on them in actual working conditions.Translated from Ogneupory, No.6, pp. 58–61, June, 1970.     

Synthesis and characterization of maltose fatty acid monoesters as biosurfactants

Maltose long-chain fatty acid esters (MFAE), esterified at the 6 and 6′ position, were synthesized with stearic, palmitic, myristic, and oleic groups. Synthesis yields were 15–20% based on initial maltose present, and structural confirmation was obtained using plasma desorption mass spectrometry and nuclear magnetic resonance spectroscopy. These surfactants have surface tensions in the range of 34–36 dyn/cm at their critical micelle concentrations (CMC) of approximately 10⁻⁵–10⁻⁶ mol/L. The increased chain lengths have a marked effect, reducing CMC values for MFAE by approximately three orders of magnitude over similar carbohydrate-based dodecyl chain sources. Within chain lengths between 14 and 18 carbons, the rate of change in CMC is significant and decreases with increasing chain length for MFAE. The melting points of MFAE are approximately 40°C, and the heat capacities range from 1.6 to 1.9 J/g·K. These numbers are comparable to those of sucrose esters, indicating their applicability in similar uses. However, because MFAE, unlike sucrose, possess an anomeric carbohydrate carbon position, these surfactants maintain their reducing nature and are susceptible to further derivatization. They are also synthesized from renewable, economical carbohydrates and lipids and may provide an excellent alternative to pertrochemical-derived products.     

Effect of additives on formation of natural gas hydrate

The formation of natural gas hydrate (NGH) is studied in this work. Kinetics data of hydrate formation with no agitation were collected at various concentrations of the aqueous solutions with different additives such as alkylpolyglucside, sodium dodecyl benzene sulfonate and potassium oxalate monohydrate. Various kinds of additive increased the formation rates of NGH and its storage capacity and reduced the induction time of NGH formation. Moreover, the storage capacity, the induction time and the hydrate formation rate were influenced by the concentration of the aqueous solution.     

Structure development in amorphous starch as revealed by X‐ray scattering: Influence of the network structure and water content

The evolution of the amorphous structure of starch was characterized during the drying process by real‐time X‐ray wide‐angle scattering. The X‐ray diffractograms of injection‐molded starch show two superposed, rather broad, scattering maxima indicative of noncrystalline structures. The location of the two peaks has been associated to disordered starch single helices. A third maximum that arises upon drying the material in vacuum is associated to the scattering emerging from regions containing double helices. A model for the starch network is proposed, assuming a primary and a secondary component. The wider, temperature stable component appearing first, is correlated to the entanglement network of the melt. The narrower network component, which is created later, at lower temperature (secondary network), is explained by the formation of double helix regions that densify the wider primary network. The secondary network is increased strongly by the drying process. X‐ray experiments performed during the penetration of water, provoking a higher molecular mobility, reveal a better‐packed helical structure that becomes the precursor of a double helix crystalline formation. When temperature increases, the secondary network is dissolved and water molecules arrange themselves in better‐organized crystals as strongly bound crystal water. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1880–1886, 2006