Interpretation of DSC measurements of the degree of fusion of rigid PVC

Differential scanning calorimetric (DSC) measurements can be used to infer the degree of fusion of rigid PVC articles. The preferred method involves annealing of the specimen at 260°C for 5 minutes, to erase all crystalline structures, followed by a 2 day storage at room temperature. New crystalline entities that are formed give use to an endotherm in the DSC heating mode. The magnitude of this endotherm divided by the total endotherm observed to 220°C can be used to estimate the degree of fusion of the specimen. Data from various processes and different cross-sections of extruded pipe are consistent with solvent resistance estimations.     

Effect of the degree of polymerization of cellulose triacetate on the physicomechanical properties of yarns

Conclusions The dependence of the relative breaking load and elongation at break of cellulose triacetate yarns and the resistance to abrasion and to repeated bending on specific viscosity of the polymer have been investigated.On increase in specific viscosity from 0.32 to 0.41, the fibre strength rises from 9 to 11.4 cN/tex; the resistance to bending, from 1200 to 2000 cycles; the resistance to abrasion, from 1000 to 8000 cycles. The elongation at break and resistance to repeated stretching change but little with increase in specific viscosity.Translated from Khimicheskie Volokna, No. 3, pp. 46–47, May–June, 1985.     

Quantification of the degree of reaction of fly ash

The quantification of the fly ash (FA) in FA blended cements is an important parameter to understand the effect of the fly ash on the hydration of OPC and on the microstructural development. The FA reaction in two different blended OPC-FA systems was studied using a selective dissolution technique based on EDTA/NaOH, diluted NaOH solution, the portlandite content and by backscattered electron image analysis.The amount of FA determined by selective dissolution using EDTA/NaOH is found to be associated with a significant possible error as different assumptions lead to large differences in the estimate of FA reacted. In addition, at longer hydration times, the reaction of the FA is underestimated by this method due to the presence of non-dissolved hydrates and MgO rich particles. The dissolution of FA in diluted NaOH solution agreed during the first days well with the dissolution as observed by image analysis. At 28 days and longer, the formation of hydrates in the diluted solutions leads to an underestimation. Image analysis appears to give consistent results and to be most reliable technique studied.     

Chemistry of the modification of sulphur by the use of dicyclopentadiene and of styrene

Dicyclopentadiene reacts with excess sulphur in the melt at 140°C to give initially cyclic tri- and pentathianes which then copolymerise with further sulphur to give initially chain polymers and then finally cross-linked species, Styrene reacts under the same conditions to give rapid initial formation of relatively high molecular weight polymeric polysulphides which then depolymerise to give a mixture of short chain species and 2,4-diphenylthiophene.     

3种肠杆菌科细菌的耐药性变迁

目的研究大肠埃希菌、肺炎克雷伯菌、阴沟肠杆菌的耐药性变迁。方法对2007～2009年临床分离的大肠埃希菌(645株)、肺炎克雷伯菌(260株)和阴沟肠杆菌(150株),采用纸片扩散法进行体外药敏测定,并依据美国临床实验室标准化协会(Clinical and Laboratory Standards Institute,CLSI)规定的标准,分析3种肠杆菌科细菌的耐药性变迁。结果大肠埃希菌、肺炎克雷伯菌、阴沟肠杆菌对氨苄西林的耐药率均较高;对头孢他啶的耐药率低于头孢噻肟;与2007年比较,2008年和2009年对头孢吡肟的耐药率明显增长;未发现对亚胺培南耐药菌株的产生。结论细菌耐药性不断增强已成为临床治疗面临的重要难题,应从耐药监测、医院感染控制、合理使用抗生素等多方面努力,减少细菌耐药性的产生。     

成套技术出口工程项目设计经理职能探讨

通过参与向东南亚某国首次出口我国较大型成套化工技术和实施工程总承包项目管理的工作回顾,概要提出设计管理的一些共性原则和观点,抛砖引玉,供同行研讨和专家赐教,以期缩短向国际型工程公司迈进的历程,加快与国际接轨的步伐。     

Effect of degree of deacetylation of chitin on the properties of chitin crystallites

In the present article, chitin from crab shell was systematically deacetylated using a NaOH treatment with control of the reaction time. The degree of deacetylation, monitored using solid-state NMR, revealed that the reaction was pseudo-first order. Based on this, swollen and NaOH-saturated particles are proposed as the reaction system. The weight loss of the partially saponified and neutralized samples after HCl hydrolysis increased linearly with the degree of deacetylation. The crystallinity of the samples was found to increase after acid hydrolysis. According to conductimetric titration, the surface charge density of the crystallites, after acid hydrolysis, was found to increase with base treatment time. The effect of surface charge on the formation of a chiral nematic phase, due to the rodlike nature of the crystallites, was explored. These results show that because the contribution of charged particles to the ionic strength was significant the double layer compression was affected, especially since the surface charge density was close to the Manning limit. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:373–380, 1997     

Effect of degree of abrasion of composite surfaces on strengths of adhesively bonded joints

Strengths of double lap joints between carbon fibre composite and aluminium alloy varied over a threefold range, and low strengths were correlated with a high proportion of failure in adhesion to the composite. Low strengths were traced to incomplete abrasion by grit blasting of the composite surface before bonding, although the effect appeared to depend on the adhesive used. Low strengths of lightly abraded joints were probably due to PTFE residues from the release cloth.     

溶胶-凝胶技术在催化剂制备中的应用

介绍了溶胶-凝胶法制备催化剂的3种主要方法:(1)将有机分子直接物理包容到陶瓷材料中;(2)通过与有机金属烷氧化物的共聚对陶瓷基体进行改性;(3)通过共聚形成2种或2种以上物质的基体复合物。并对3种方法进行了综述。     

滤床过滤系数的确定方法

过滤系数λ是表征深层过滤性能的重要参数,用试验的方法测定滤床过滤系数较为复杂。通过试验法和数学模拟法对不同粗细的滤料滤床进行研究,确定其λ的具体值,通过比较两者的结果发现,利用数学模拟法替代复杂的试验方法来确定实际滤床的过滤系数和预测运行状况是简便可行的。     

Role of Pressure in Coking of Thin Films of Bitumen

An important step in the formation of product from feed in a fluidized‐bed coker is the evolution of product and coke from layers of vacuum residue on the surfaces of heated particles and from liquid inside agglomerates of liquid and solid. In the present study, the yield of coke from Athabasca vacuum residue was measured using a reactor based on rapid induction heating of thin films of liquid feed on the surface of pieces of Curie‐point alloy. This approach allowed measurement of the yield of coke at pressures from 101–652 kPa, temperatures of 503 and 530°C, and reaction times from 10 to 240 s. When the liquid was reacted in thin films of ca. 20 µm, the effects of temperature and pressure on coke yield were insignificant. As the film thickness was increased to 120 µm, the yield of coke increased at all conditions. The yield of coke from thicker films was only sensitive to total pressure at 503°C reaction temperature, when the pressure was increased from 377 kPa to 652 kPa. Observable bubbling due to cracking reactions during coking was suppressed by increasing pressure, and the transition from quiescent liquid to bubbling liquid increased from circa 26 µm at 101.3 kPa to 78 µm at 652 kPa at 503°C. The bubbling transition was much less sensitive to pressure at 530°C, falling in the range from 22 µm to 43 µm as pressure increased from 101.3 to 652 kPa. These results suggest that the most important effect of pressure will be on the physical behaviour of liquid feed, due to its impact on bubble evolution from liquid inside agglomerates of liquid and solid particles. Depending on the liquid/solid ratio in an agglomerate, the formation of bubbles inside such a structure would make it weaker and easier to disperse on the fluidized bed reactor.     

Application of the method of the experimental design to the study of a processing of unshrinkableness of wool fibers

The objective of this study was to optimize the character of the unshrinkableness of wool fibers. A study of the processing of fibers of wool by an oxidative processing by performic acid was carried out by a complete factorial design to determine the most influential parameters of this study and then to optimize this process by the method of simplex. In parallel, a new ozone treatment was applied and a central composite design adapted to this protocol made it possible to identify the most influential parameters. This last type of processing has the advantage of being less polluting. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 535–547, 2003     

提高渗透率解释精度的方法

在油田的勘探开发过程中,始终都离不开渗透率这个参数。因此,提高渗透率的解释精度就成为解释人员的一项重要工作。很多情况下,渗透率的误差可能会达到数量级的水平。如何提高渗透率的解释精度,国内外的很多学者提出不同的研究方法。本文以秘鲁1-AB区块SAN-JACINTO油田为例,利用试油试采的动态资料对测井解释的渗透率进行校正,从而能够真实地反映出原始地层的渗流特点。     

Equation of state of the detonation products of RDX

Summary Experimental data and theoretical ideas concerning the detonation adiabat and the thermodynamic properties of real gases have been used to find the equation of state of the detonation products of RDX in the density range 0–2.3 g/cm³. The equation of state relates mainly to the region of thermodynamic parameters corresponding to adiabatic expansion of the explosion mines the pressure at given values of the density and energy in this region correct to 5–10%.Fizika Goreniya i Vzryva, Vol. 2, No. 4, pp. 85–96, 1966     

Theory of yield of cohesive powders

In many problems in process technology, the influence of the adhesion forces on the mechanics of fine powders plays a considerable role. The existing knowledge is characterized by intensive experimental and theoretical investigations into the mechanism of adhesion for single particle contacts without consolidation by external forces. On the other hand, the mechanical behaviour of cohesive powders has been investigated mainly on the basis of continuum mechanics.For science and technology, it is useful to combine the particles approach and the continuum approach in order to provide a better understanding of the mechanical properties of cohesive powders. A theoretical model has therefore been developed which takes into account the forces acting in interparticle contacts. The theory especially considers the increase in the adhesion forces transmitted in interparticle contacts with increasing consolidation. Contrary to the commonly used phenomenological view, this theory yields a physically based understanding of the effective yield locus for steady-state flow which is reduced to material properties of the solid particles and is therefore shown to be an invariant of a respective powder.The opinion found in the literature that a single yield locus uniquely belongs to one consolidation locus is shown to be not valid. The microstructural view of a cohesive powder is able to show that, contrary to the continuum mechanical view, in the general case a cohesive powder is mechanically anisotropic due to its loading history.     

Effectiveness of combustion of shock-dispersed fuels in calorimeters of various volumes

The combustion of a shock-dispersed-fuel charge consisting of 1-g flake Al in 6.6-, 21.5-, and 40.5-liter bomb calorimeters were investigated. Wall pressure histories were used to diagnose the effect of energy release due to turbulent mixing and combustion of the explosion cloud with air. These effects lead to a factor of four increase in the peak quasistatic pressure for the 6.6-liter chamber. Pressure decay was observed at late times and was ascribed to energy losses to the walls due to radiation heat transfer. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 6, pp. 121–125, November–December, 2006.     

Studies of Early Stages of Paste Hydration of Different Types of Portland Cements

The early stages of hydration of four different types of portland cements were studied by electron-optical and X-ray diffraction techniques. It was observed that, except for low-heat cement, very little ettringite formed up to 3 hours of hydration and that the alite present in the cements was more reactive than the laboratory form. Ettringite formed earlier in the low-heat cement than in other cements. Ettringite was found to be the stable sulfate-bearing phase in sulfateresistant cement, at least up to 30 months, although in other cements ettringite began to change to monosulfate by 14 days. Direct evidence was found for the formation of gypsum from either CaSO₄±0.5H₂O or soluble anhydrite in some cements.     

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.     

A priori characterization of criticity and of dynamic thermal behaviour of a storage of cork powder

The new dispositions of the recent French law, called “Lois Risques” present some difficulties of application to qualify and quantify the new notion of dynamics of a hazardous process such as a thermal runaway. Many steady models predicting the thermal runaway (Semenov, Frank–Kamenetskii, Thomas, etc.) are proposed in literature. Due to their simplifying hypotheses, even if these models are widely used, they do not provide any information on the history of the self-heating of the system enabling to predict the necessary time to urgently react to a drift. The analysis of the transient thermal behaviour turns out to be necessary to complete the previous classical results, to estimate the profile of the adiabatic temperature rise and the time of induction for reaching the maximum adiabatic temperature and thus to better characterize the ability of the system to runaway, whose prediction fiability must be presently improved to respond to the new needs of the hazard study. The present work shows that the consideration of the influence of temperature on the heat transfer parameters and of more realistic boundary conditions during the numerical solution of the heat balances describing the storage behaviour allows us to better predict the criticity and the dynamics of appearance and of evolution of the runaway concerning the example of a cork storage.     

几种农药对甲霜灵光降解的影响

[目的]研究溴虫腈、毒死蜱、氯氰菊酯、灭多威与甲霜灵混合后对其光解效应的影响。[方法]以紫外灯为模拟光源,用一级动力学方程来描述光降解效应。[结果]甲霜灵与供试农药等剂量混合时,溴虫腈和灭多威表现出光敏化降解效应;而毒死蜱和氯氰菊酯则表现为光猝灭降解效应。与不同剂量农药混合时,溴虫腈和氯氰菊酯对甲霜灵的光敏(猝灭)效率与剂量呈正相关、而毒死蜱和灭多威与剂量呈负相关。[结论]供试农药对甲霜灵的光化学降解效应与剂量以及农药品种相关。