Convective Regime of Filtration Combustion of Energetic Materials in a Cocurrent Flow of Their Combustion Products

The convective regime of filtration combustion of energetic materials in a cocurrent flow of their combustion products is studied using a model with extremely simplified kinetics and heat transfer, which shows instability of the process. It is shown that the more accurate twotemperature model describes a steadystate regime. In this regime, the gas temperature on the hot boundary of the heating zone is well below the combustion temperature, and the solidphase temperature is well below the temperature proposed in recent studies on this topic. It is pointed out that the twotemperature approach is unjustified and intragranular nonisothermicity must be taken into account for convective regimes. It is shown that the threetemperature model, which takes into account this effect, does not give a stable steadystate solution.     

Critical solution point and chain dimension of branched-polystyrene solutions

Summary Critical solution point and chain dimension were measured for branched polystyrene(BPS) in solution as a function of molecular weight(M) and compared with those for linear polystyrene(LPS). The critical concentration _c of BPS was quite different from that of LPS at a fixed M, but the same at a fixed overlap-concentration ^*, i.e., plots of _c vs. ^* fall on a single straight line for both BPS and LPS (gf_c ^*). Reduced critical temperature _c defined by gt_c=(–T_c)/ [T_c: critical temperature, : the -temperature] was related to _c as _{c c} ² for BPS, whereas _{c c} for LPS.     

Some Problems in Drawing and Texturing of Vidlon Polycaproamide Fibres

The nature and causes of separation of white powder in drawing and accumulation of deposits on machine chamber walls in texturing of Vidlon polycaproamide fibres are investigated. It was found that the quality of the titanium dioxide suspension and the oiling agent significantly affect separation of powder and passage of the fibre in drawing. Thermooxidative and thermal and mechanical degradation processes in the polymer determine the structure of the fibres and their behavior in drawing and texturing. The amount of white powder separated is a function of the moisture content of the as-spun fibres and the climatic conditions in winding, conditioning, and drawing. The concentration of cross-links in the polymer and inorganic elements on the surface of the fibres and the amount of white powder and deposits on the walls of texturing machine chambers are closely correlated with their passability in drawing.     

Quasi‐Homogeneous and Pseudospin Modes of Zirconium‐Wire Combustion in Air

A novel experimental technique is proposed for examining the transition mechanism from quasihomogeneous to heterogeneous combustion — burning of a variablepitch spring. Depending on the pitch of aircombustible zirconium springs, two combustion modes are possible. Quasihomogeneous (layerbylayer) combustion is observed in the case of smallpitch springs; as the spring pitch increases, quasihomogeneous combustion transforms into heterogeneous (pseudospin) combustion. Conditions for the occurrence of various combustion modes, depending on the spring diameter and pitch, are studied.     

Antifungal polyoxygenated fatty acids fromAeollanthus parvifolius

Two polyoxygenated fatty acids with antifungal activity have been isolated from aerial parts ofAeollanthus parvifolius (Labiatae) using bioassay-guided isolation procedures. Spectroscopic analysis was used to identify the compounds as (Z)-4,9-diacetoxy-6,7-epoxy-5-hydroxy-8-oxododeca-2-enoic acid and (Z)-4,6,7,9-tetraacetoxy-5-hydroxy-8-oxododeca-2-enoic acid. Both of these compounds inhibited spore germination ofCladosporium cucumerinum. Minimum inhibitory doses were 1 µg and 5 µg, respectively, but only the former inhibited germination ofAspergillus niger at a dose of 5 µg. Neither compound exhibited antibacterial activity. (Z)-4,9-Diacetoxy-6,7-epoxy-5-hydroxy-8-oxododeca-2-enoic acid reduced the hyphal growth ofPythium ultimum. The mode of action was not resolved but did not involve either the disruption of the cell wall membrane or the inhibition of extracellular enzymes. Application of (Z)-4,6,7,9-tetraacetoxy-5-hydroxy-8-oxododeca-2-enoic acid to seedling plants did not give any protection against fungal attack, and indeed the compound appeared to be phytotoxic.     

Strength level of high-strength complex fibre from stiff-chain polymers

The discrete strength levels for ultrahigh-modulus Terlon, Armos, and SVM fibre were found. Small-angle x-ray scattering and the calculation procedure known as the method of tangents were used to estimate the radii of submicrocracks. The limiting and actual values of the average strength levels of these types of fibre were calculated for two characteristic radii of inertia R₁ and R₂. The agreement of the results with the published data confirms the accuracy of the method of tangents.Ukrainian Scientific-Research Institute of Fibre, Kiev. Translated from Khimicheskie Volokna, No. 6, pp. 33–35, November–December, 1992.     

Specific features of the phase transformations occurring during the sintering process of the beta-alumina based ceramics and their properties

Conclusions During the sintering process of beta-alumina obtained using the method of plasmochemical synthesis, the structural transformation occurs and it is accompanied by the separation of the excess Na₂O and the formation of an intergranular meltlike phase that is saturated with sodium and is characterized by high dielectric properties.The quantity of the meltlike phase and the magnitude of the /( + ) ratio determine the degree of stabilization (stability) and the final resistivity of the material and depend on the initial chemical composition and the heating rate maintained during the sintering process.It was shown that when the duration of residence of the material in the hot zone of the furnace is increased or when the specimens sintered maintaining high heating rates are subjected to additional heat treatment, one observes the occurrance of the reverse structural transformation that is characterized by an increase of the phase ratio /( + ) 1, a reduction in the quantity of the meltlike phase right up to its complete disappearance, and a decrease of the electrical resistivity of the material.In the materials having a large excess quantity of sodium oxide, the process of crystallization of the intergranular NaAlO₂ phase occurs simultaneously with the second phase transformation.The best ceramic and electrophysical parameters were obtained when sintering the material contained 7.9% Na₂O.Translated from Ogneupory, No. 3, pp. 13–18, March, 1990.     

Birefringence of polyamide fibres of nonround cross-sectional from

Conclusions A method of determining the birefringence n of fibres having an uncomplicated profile (pentagonal, trilobal, or double rhombus) consists of the following: Over sections of the fibre one determines the ratio of the outer-contour dimensions — the diameterl of the fibre to its thickness d — the path over which the beam acquires the difference in speed ; the values of ,l, andl/d are averaged; and the calculation of n is carried out from the equation n = .This method has been tested on specimens of polyamide fibre prepared under identical melt flow rate conditions.Translated from Khimicheskie Volokna, No. 3, pp. 42–43, May–June, 1983.     

Boron-Free, Alkali-Free Glass Fibre for Production of Fibreglass-Reinforced Plastics

A boron-free alkali-free glass fibre with better fundamental properties than type E fibre was developed. The process properties of the new glass allow drawing the glass fibre on existing equipment. The fibre is recommended for use as a filler for high-strength fibreglass-reinforced plastics and for reinforcing corrosion-resistant fibreglass-reinforced plastics.     

Shrinkage of highly oriented gel-spun polymeric fibres

Summary The melting and shrinking process of gel-spun hot-drawn UHMWPE fibres has been investigated. Instead of being superheated, the highly oriented fibres start to melt at the fibre ends and shear bands, at a temperature near the equilibrium melting temperature of polyethylene. For draw ratios of 40, the fibre transforms into a ribbon shape upon melting. This change in shape could be prevented by constrained heating before shrinkage. Ribbon-like melting was also observed for gel-spun hot-drawn poly(L-lactide) fibres.     

Location of Mn in MnAPO‐11: influence of synthesis from aqueous and non‐aqueous media

MnAPO11 samples were synthesized from aqueous (MnAPO11(A)) and ethylene glycol (MnAPO11(NA)) media. The crystallinity of the samples was more when the synthesis was carried out in ethylene glycol. Chemical and thermogravimetric analyses reveal greater incorporation of Mn in the framework of MnAPO11(NA) than in MnAPO11(A). At least five different types of Mn(II) species are detected in the samples by ESR. The studies suggest that Mn is more homogeneously distributed in MnAPO11(NA) than in MnAPO11(A).     

Recovery and recrystallization of electrodeposited bright copper coatings at room temperature. II. X-ray investigation of primary recrystallization

X-ray investigations of the recrystallization processes occurring at room temperature in electrodeposited bright copper coatings were carried outin situ. As a result of the orientation transformation of the growth texture with 311, 111 and 110 components, a recrystallization texture with 100, 110 and 111 components was obtained. It was established that one of the factors which influence the microhardness of copper coatings is the orientation distribution of crystallites.     

Studies on electrical conductivity of gamma irradiated polyaniline

Summary de electrical conductivity at surface of -irradiated polyaniline (PAn) has been studied. EPR spectroscopic results indicate that the variation of spin concentration is consistent with the increase of _de. Electrical conductivity (_de) versus temperature (T) characteristics of unirradiated and irradiated PAn were performed, which demonstrate that the unirradiated curve can fit to ln_deT₁, while the irradiated curve fit to ln_deT_1/4.     

Stress relaxation during the orientation stretch of synthetics fibres

Conclusions Results of investigating structural changes during the process of orientation stretching above the glass point (hot stretching) for a number of thermoplastic fibres have been examined: polyethylene, polypropylene, polyvinyl chloride, chlorine, kapron, nitron, lavsan, vinol, and acetate yarns, plus results of heat-treatments under tension and in the free state. The possibility of describing the relaxation of internal stresses in these fibres in terms of the concept of operating volume has been shown.A correlative determination of the dependence of fibre stress dispersion during the process of orientation stretch and setting the structure of polyester yarn on the dispersion in yarn heat treatments has been established, as well as a dependence of the dispersion of physicomechanical properties on dispersion in fibre tension by steps in the technological process.Translated from Khimicheskie Volokna, No. 3, pp. 29–32, May–June, 1993.     

Formation of a phase structure of the “fibrils in matrix” type in a composite fibre based on high-density polyethylene and polyethylene terephthalate

Conclusions Regions of component ratio and conditions for obtaining a composite fibre of the fibrils in matrix type have been determined for the HDPE-PET system.At an HDPE-PET ratio of 60:40, phase inversion takes place and a structure of the interpenetration networks type is realized.Under identical fibre spinning conditions, the formation of a phase structure of the fibrils in matrix type can be regulated by varying the temperature.Translated from Khimicheskie Volokna, No. 4, pp. 38–40, July–August, 1987.     

Kinetics and Mechanism of Separation of Water from Polybenzothiazole Fibres

The kinetics and mechanism of separation of water from polybenzothiazole fibres was investigated by mass spectrometry. It is shown that weakly bound and strongly bound water of different origins is separated from fibres during thermal drawing.     

Dense magnesium oxide refractories with increased spalling resistance

Conclusions A production process of magnesium oxide spinel-bound plates with a porosity of 1 to 3%, high spalling resistance and considerable life span at high temperatures was developed.The production process is distinguished by the application of dead-burned finely-milled magnesium oxide, the introduction of highly dispersed -AI₂O₃, compression of green compacts from pseudogranular mixtures, slow drying accompanied by uniform air circulation and two-stage firing at 1450 and 1750° C in powder-covered capsules.     

State and prospects of development of domestic equipment for manufacture of needle-punched,nonwoven materials from polymer melts

Conclusions Domestic equipment has been devised for the production of needle-punched nonwoven geotextile materials from second-grade polycaproamide or fibre-forming polypropylene.The geotextile materials produced are promising for use in construction of roads, foundations of buildings, in hydrotechnology, and in land reclamation.Promising trends in the development of equipment for preparing spun nonwoven materials have been noted (light-duty needle-punched or heat-bonded materials, bulky spun articles, etc.).Coworkers of the Kemerovskii and Kamenskii Khimvolokno IAs the Khimtekstil'mash SIA, the VNIISV, the GIPROtyumenneftegaz, the SoyuzdorNII, and the Plastpolimer SIA took part in this work.Translated from Khimicheskie Volokna, No. 4, pp. 8–10, July–August, 1989.     

Improving Carbon Fibre Production Technology

The quality of carbon fibres, their strength and modulus of elasticity in particular, can be increased by the following methods: decreasing the porosity of the initial PAN fibres by selecting the optimum conditions for spinning, plasticizing drawing, finishing, and drying; decreasing the inhomogeneity of the diameters of PAN fibres by suppressing deformation resonance during spinning by selecting conditions of jet formation and precipitation that do not allow formation of bulbs in the jets or prevent their deformation; decreasing fibril and crystallite size by reducing the precipitant and solvent concentration gradient in the precipitation zone (spinning in mild baths); creating optimum conditions for interphase self-ordering of the polymer at 450-550°C during precarbonization; increasing the cohesive energy by increasing the density to 1.75-2.10 g/cm³. Substitution of convective tempering of PAN twists in thermooxidative treatment by conductive (contact) treatment decreases the duration of the treatment by 3-4 times and improves the environmental conditions. Use of reflecting screens in high-temperature furnaces reduces heat losses by 4-5 times and decreases consumption of cooling water. The progress made in the technology and creation of high-capacity equipment suggests that the cost of high-strength carbon fibre will decrease to $10-15/kg in the future in the condition of large-scale production.     

Properties of fibres of cellulose acetomethacrylates

Conclusions 1. The authors have shown that fibres can be formed for acetic acid syrups of mixed esters of cellulose with acetic and methacrylic acids.2. The effect of the composition of cellulose acetomethacrylate on the physicomechanical properties and degree of orientation of the fibres has been studied. It has been established that maximal improvement of the strength and degree of orientation of the fibres takes place at _max=7–9.3. The change in fibre structure in relation to the methacrylic acid content has been studied by electron-microscopic analysis. It is shown that the structural uniformity of cellulose acetomethacrylate fibres improves at _max=7–9; a further increase in _max leads to a decrease of the structural uniformity.First communication of a series devoted to Preparation of fibres on the basis of cellulose esters, and study of their properties.NIIKhTTs. Translated from Khimicheskie Volokna, No. 5, pp. 41–43, September–October, 1969.