Detonation waves in polydisperse bubble media

Detonation waves in polydisperse and monodisperse bubble media are studied experimentally. The data on the critical initiation conditions and the structure and properties of detonation waves are obtained. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 6, pp. 71–76, November–December 1998.     

Detonation waves in multicomponent bubbly media

Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 1, pp. 110–117, Junuary-February, 1993     

Detonation of liquid explosive mixtures in powdered media

The propagation of detonation in liquid explosive mixtures (LEM) (nitrobenzene solutions in tetranitromethane) in inert and active powdered media of normal loose packing has been experimentally studied. It is shown that for small distances the general wave process is determined only by the propagation of detonation in LEM through narrow channels formed by separate particles of the powdered material independently of its acoustic stiffness. As the distance increases, in heterogeneous explosive mixtures with HMX a comparatively low-velocity wave smoothly changes to stationary detonation of the composition as a whole.All-Russian Research Institute of Experimental Physics, Arzamas-16 607200. Translated from Fizika Gorenia i Vzryva, Vol. 31, No. 2, pp. 156–160, March–April, 1995.     

Detonation velocity of highly dispersed ammonium perchlorate and its mixtures with explosive substances

This paper describes the measurement of the detonation velocities close to ideal velocity relative to large charges of highly dispersed ammonium perchlorate (AP) and its mixtures with different explosive substances in thick-walled steel pipes. The relationship of the detonation velocity of AP with its density and the relationship between the detonation velocity of mixtures with the component ratios and oxygen coefficient of the mixtures are determined. The calculation of the detonation velocity of AP/explosive/Al three-component compositions is proposed for the first time.     

Analysis for concentric-double inclusions dispersed in continuous media

The behaviors of concentric-double inclusions dispersed in continuous media are investigated theoretically to find some possibilities of improving toughness of composite materials by dispersing double-inc’usions instead of single-inclusions. The general solutions of the Stokes equation, expressed in terms of the spherical harmonics, are used for analyzing the problems that are related to the concentric-double inclusions. From the analysis, it is found that the pressure and stress fields inside and outside the inclusion can be modified by changing the modulus ratios and the thickness of shell layer. Especially, the positions of the minimum pressure points and the maximum stress points turn out to be controllable with some degree of freedom.     

Color control of interference pigments dispersed in translucent media

This article presents a method of evaluating the color of special‐effect pigments dispersed in translucent media and of characterizing the color of such media. An analytical model eliminating the effect of sample thickness variations is proposed. The method is based on reflectance measurements against both white and black backgrounds and is applied to the flexible poly(vinyl chloride) model for the quality control of pearlescent/interference/aluminum pigments based on the calculated color differences and for creating a color‐matching database for computer color formulation. © 2002 Wiley Periodicals, Inc. Col Res Appl, 27, 83–87, 2002; DOI 10.1002/col.10032     

High-strength high-modulus carbon fibres

Translated from Khimicheskie Volokna, No. 3, pp. 5–8, May–June, 1991.     

Gas transmission through polymers

Little data is available on gas transmission through thick polymer samples. There is, therefore, a temptation to assume an inverse relationship between gas transmission rate and thickness and to calculate flow through thick samples using permeability data obtained on thin films. This is incorrect, as the calculation assumes steady flow, and with thick samples this state may not be reached for months or even years. Thus both diffusivity and permeability are needed to calculate the gas flow and the calculations are more complex than simple permeability calculations. Because of the long time scale, the effects of varying the thickness are difficult to demonstrate experimentally. We describe a computer simulation of the manometric method which compares the behavior of two materials with similar permeabilities but different diffusivities. Although thin samples behave identically, they differ increasingly with thickness. The pitfalls in using the gradient and time lag of the pressure curve to calculate permeability and diffusivity are also discussed.     

High-strength/high-modulus organic fibers

Current trends and developments taken from the literature are reviewed and some new work from the laboratories of Monsanto Company is presented concerning the use of aromatic polymers for high-strength/high-modulus fibers. In the area of aromatic polymer synthesis, pertinent information concerning the factors necessary for the attainment of high molecular weight for the heat-resistant type polymers and for the ultra-rigid type polymers is discussed. Some new polymers and new routes of synthesis for rod-like polymers are described along with the tensile properties of fibers from these novel polymers.     

Conformational considerations of high-modulus polymers

Some general considerations are given concerning the conformational factors affecting the inherent elastic modulus of the macromolecular chains in the crystalline state. In particular, the influence of the size of side groups and that of the chain extension are discussed. Some conformational properties concerning two polymers with different stiffness, both containing amide groups, are clarified.     

Synthesis and properties of high-modulus zeolites

Zeolites with a high silica modulus were synthesized using a hexamethylenediamine (HMDA) structure-forming addition. Their physicochemical and acid characteristics were studied. The zeolites showed high activity and stability during the conversion of methanol.     

Continuous extrusion of high-modulus semicrystalline polymers

A process has been developed by which very high-modulus semicrystalline polymer films can be extruded continuously from a melt. This is accomplished by controlled cooling of the melt in a two-stage flow channel. A temperature gradient along the flow channel quenches the melt prior to an area reduction in which the polymer undergoes solid-state orientation. Analysis of high-density polyethylene tapes extruded by this process shows that they have properties similar to samples hydrostatically extruded at 120°C. Infrared analysis was used to determine both the degree of crystallinity and degree of orientation in these tapes as well as previously prepared hydrostatically extruded samples.     

Transmission of Bubble Detonation through a Layer of an Inert Liquid

The possibility of detonation transmission through a water plug from one column of a chemically active bubbly medium to another is experimentally verified. The critical length of the liquid plug is determined. The experiments are performed in a shock tube with bubbles of a stoichiometric acetylene–oxygen mixture in water. The character of peakpressure decay after detonationwave departure from the bubbly medium to the liquid is established. It is shown that the pressure profile retains similarity as the compression wave propagates over a discrete gas–iquid medium.     

Highly dispersed carbon nanotubes in organic media for polymer:fullerene photovoltaic devices

Composites for a photo-active layer in an organic photovoltaic device are fabricated using homogeneously dispersed carbon nanotubes (CNTs) in a polymer:fullerene bulk-heterojunction matrix. CNTs are functionalized by alkyl-amide groups for high dispersion in organic media and by homogeneously mixing them with the polymer and fullerene in solution. In a Fourier transform infrared spectrometry analysis, the formation of functional groups is confirmed. Scanning electron microscopy images indicate the high dispersion of the CNTs. These composites show considerable improvement of their optical and electrical properties due to effects of the wideband photo-absorption and high charge carrier mobility of the CNTs. These effects were investigated by ultraviolet–visible spectroscopy and by the fabrication of an organic thin film transistor. An organic solar cell was fabricated from these composites as a photo-active layer, showing a remarkable 40% (3.2–4.4%) increase of the power conversion efficiency compared to an organic solar cell using a photo-active layer without CNTs.     

Oxygen transmission through highly crosslinked polymers

Highly crosslinked polymers of varying structure were produced by the reaction of poly(glycidyl acrylate) (PGA) and methacrylate (PGM) with a variety of anhydride crosslinking agents: chlorendic (CA), glutaric (GA), maleic (MeA), succinic (SA), and polyrnalonic (pMnA) anhydrides. Topology was also varied by the use of a diluent and a comonomer in the backbone chain. Oxygen permeation measurements were made on these polymers coated onto a polypropylene film substrate before crosslinking. The crosslinking process greatly reduced the O₂ permeability which, however, was dependent not only on the degree of crosslinking (yield of the crosslinking reaction), but also on the crosslink density, the chemical nature of the structural elements, and the topology of the polymer network. Thus the most impermeable coating (XPGA/CA) was made not from the stiffest and bulkiest components (PGM and CA), but by the reaction of the bulkiest anhydride (CA) with the more flexible polymer backbone chain (PGA). This is explained in terms of the need for chain flexibility to produce a crosslinked structure of optimum space filling character and network tightness.     

PAN基高模碳纤维阳极氧化的表面处理

采用阳极氧化法对PAN基高模碳纤维进行连续表面处理,重点研究了氧化电流密度对碳纤维宏观力学性能、表面形貌、表面酸性官能团以及碳纤维增强树脂基复合材料(CFRP)层间剪切强度(ILSS)的影响。结果表明,电流密度对纤维力学性能、表面形貌影响不大;氧化后纤维表面总的酸性官能团显著提高,最大增幅达13倍左右;适当的处理条件可使CFRP的ILSS从28.4 MPa提高到80 MPa以上。     

制备高模型对位芳纶热处理工艺研究

在通用型对位芳纶的基础上进行热处理制备高模型对位芳纶。试验研究了通用型对位芳纶初始含水质量分数、热处理张力、热处理温度、热处理时间等对处理后纤维性能的影响,并深入分析了纤维取向、晶体结构与纤维模量的关系,得出了制备高模型对位芳纶的最佳热处理工艺条件。结果表明,通用型对位芳纶初始含水质量分数10%~30%,热处理张力1.8~3.1 cN/dtex,高温处理时间4.2 s,热处理温度≯500℃,可制得力学性能、取向度、晶体完美指数和晶粒直径与杜邦Kevlar-49相同的高模型对位芳纶。     

High-strength high-modulus fibres from liquid-crystalline aromatic polyesters

Translated from Khimicheskie Volokna, No. 3, pp. 42–49, May–June, 1990.