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Abstract  

The use of modulated temperature differential scanning calorimetry (TMDSC) and differential scanning calorimetry (DSC) in the measurement of the glass transition temperature (T g) in polymer-water systems presents several important problems. These include the presence of water evaporation endotherms, partial water evaporation during scanning, changes in pan integrity due to vapour pressure developing in the pan headspace during analysis, and possible interaction between water and polymer at high temperatures. As a result, in most of the cases, only apparent T g values can be obtained. In this study, TMDSC and DSC were used to determinate the thermal behaviour of methylmethacrylate copolymer-water systems. The samples were previously equilibrated at different relative humidities (RH) from 0 to 97% RH. Three different pan arrangements were used. In addition, thermogravimetric analysis (TG) was carried out to determine the initial amount of water in the sample. None of the pan arrangements was entirely suitable for the study of these systems. When sealed pans were used, the plastification effect of water was observed. Some evidence of degradation was also observed in which water and methylmethacrylate appeared to play roles.

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Abstract  

The reactivity of MgO obtained from calcination of magnesium carbonate at different temperatures has been investigated by means of hydration in a constant relative humidity environment at 40°C for periods up to 24 days. Natural magnesite and AR grade basic MgCO3 calcined in the range of 500–1000°C was characterised in terms of surface area, crystallite size, morphology, and hydration rate. It was found that the hydration rate is dependent on the surface area and crystallite size where temperature was the main variable affecting them. The most reactive MgO was produced at the lowest calcination temperature with the highest surface area and the smallest crystallite size. The basic MgO specimens showed higher degree of hydration compared to the natural MgO specimens due to the smaller surface area and larger crystallite size. The low MgO content of the starting natural magnesite is also attributable to the lower reactivity. This preliminary study serves as a mean to investigate potential utilisation of reactive MgO as a supplementary cementitious material in eco-friendly cements.

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Journal of Thermal Analysis and Calorimetry
Authors: D. Giron, Ch. Goldbronn, M. Mutz, S. Pfeffer, Ph. Piechon, and Ph. Schwab

Abstract  

Manufacturing processes may involve the presence of water in the crystallization of the drug substance or in manufacturing or in the composition of the drug product through excipients. Dehydration steps may occur in drying, milling, mixing and tabletting processes. Furthermore, drug substances and drug products are submitted to different temperatures and relative humidities, due to various climatic conditions giving rise to unexpected hydration or dehydration aging phenomena. Therefore the manufacture and the characterization of hydrates is part of the study of the physical properties of drug substances. Several hydrates and even polymorphic forms thereof can be encountered. Upon dehydration crystal hydrates may retain more or less their original crystal structure, they can lose crystallinity and give anamorphous phase, they can transform to crystalline less hydrated forms or to crystalline anhydrous forms. The proper understanding of the complex polyphasic systemhydrates–polymorphs–amorphous state needs several analytical methods. The use of techniques such as DSC-TG, TG-MS, sorption-desorption isotherms, sub-ambient experiments, X-ray diffraction combined with temperature or moisture changes as well as crystal structure and crystal modelling in addition to solubilities and dissolution experiments make interpretation and quantitation easier as demonstrated with some typical examples.

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Abstract  

Aerosol particles smaller than 1.8 m were size-fractionated with micro-orifice impactors at two urban sites near Washington, DC, and analyzed for 44 elements including, As, Se, Sb, and Zn, i.e., elements strongly associated with coal combustion, incineration, and regionally transported secondary aerosol, by Instrumental Neutron Activation. Size distribution parameters were determined nonparametrically and with a least-squares peak-fitting method using impactor calibration data. Geometric and fitted mass mean aerodynamic diameters typically differed by <10% and increased continuously with increasing relative humidity (RH) in the range 56 to 79%, but along different curves for samples influenced by local and distant sources. The geometric mass mean diameters for samples influenced by winds from the direction of local sources were uniformly smaller than those influenced by westerly winds bearing aerosol from distant, regional, sources. At 60% RH, gmmads were As, 0.30±0.03 and 0.46±0.04; Se, 0.33±0.06 and 0.54±0.04; Sb, 0.39±0.03 and 0.53±0.04; and Zn, 0.39±0.06 and 0.53±0.08; respectively.

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Abstract  

The system of sulfoaluminate ferrite belite (SAFB) clinkers premixed with Portland cement (PC) in mass ratio 85:15 in combination with hydroxypropylmethyl cellulose (HPMC) or polyphosphates(poly-P) was used for the syntheses of Macro-Defect-Free (MDF) materials. The subsequent moisture treatment and thermal stability of these MDF materials were investigated. The effect of individual humidity upon the evolution of mass is more intensive than the effects of composition of MDF materials or duration of the original MDF material synthesis. Detailed values of mass changes at 100% relative humidity (RH) and under ambient conditions are strongly affected by the nature of polymer used. A significant improvement of moisture resistance of MDF materials is achieved when the materials are dried after 24 h of finishing the pressure application. In the inter-phase section of MDF material samples, the content ofC-(A,F)-S hydraulic phases, mainly tetracalcium aluminate ferrite monosulphatehydrate (AFm) decomposing by 250°C and CaCO3 decomposing at 600–700°C increase after the moisture attack, while cross-links in AFm-like section with typical thermoanalytical traces in temperature region 250–550°C remain intact.

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Abstract  

The chemical stability of a propellant and its influence on the ballistic properties during aging is a subject of interest. The effect of aging on ballistic properties, viz., ignition delay, burning rate, and heat of combustion for an aluminised ammonium perchlorate–hydroxyl-terminated polybutadiene (AP/HTPB) composite propellant during accelerated aging were investigated. Samples of composite propellants were aged at 60 and 70 °C at relative humidity of 50% in a climatic chamber. The propellant samples were tested with pressurized nitrogen gas environment for ignition delay measurement. Test results indicate that aging does not have any appreciable effect on ignition delay. The change in ignition delay time is less than 3% within the scatter of the data. Experiment results indicate that burn rate do affect with pressure but aging does not have much effect on burn rate. It was also observed that the burning rate at low pressures did not undergo significant changes during the aging period. The most significant of all the ballistic properties of this propellant is the burning rate exponent which increased by about 10% during the aging period.

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Abstract  

South-Eastern part of Romania has a highest potential seismic risk in Europe due to the earthquake-prone Vrancea zone placed at conjunction of four tectonic blocks in the South-Eastern part of Carpathian Arc. This paper is an attempt to analyze the development of radon pre-earthquake anomaly in relation with moderate seismic events in Vrancea area through permanent monitoring with solid state nuclear track detectors CR-39 detectors. Radon in air above the ground was measured during 1 year period (November 2010–October 2011) in four selected test sites: Vrancioaia (VRI) and Plostina (PLOR) located in Vrancea zone, and Muntele Rosu-Cheia and Bucharest. During sampling period recorded earthquakes that occurred mostly in Vrancea epicentral region were minor-moderate of moment magnitudes in range of
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. The average radon concentration in air above the ground measured with CR-39 detectors and 10 days period recorded simultaneously at all test sites, registered the following values: (1) in Vrancea area (similar in VRI and PLOR) was 1094.58 
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 150.3 Bq/m3; (2) at Muntele Rosu-Cheia seismic station measured in a mountain tunnel laboratory was 3695.91 ± 440 Bq/m3; (3) at Bucharest station was 380.53 
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 69.17 Bq/m3, and 10 days CRn fluctuations in the range of (88 
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 40 to 912
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 130 Bq/m3). Clear radon anomalies, mostly at VRI and PLOR in Vrancea epicentral area as well as at Muntele Rosu-Cheia have been measured before seven minor earthquakes which were recorded in the range of moment magnitude
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in Vrancea area. Temporal variation of radon in air near the ground have been examined in relation with meteorological parameters like as air temperature, relative humidity, air pressure and wind velocity. Permanent monitoring of radon concentration anomalies in seismic area Vrancea is an important issue as surveillance tool in the field of earthquake hazard for Romania.
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Acta Chromatographica
Authors: M. Pacenti, S. Dugheri, R. Gagliano-Candela, G. Strisciullo, E. Franchi, F. Degli Esposti, N. Perchiazzi, P. Boccalon, G. Arcangeli, and V. Cupelli

Summary

2-Chloroacetophenone (CA) is widely used as tear gas by law-enforcement agents, and by civilians for personal protection. Crimes involving robbery and rape using tear gas sprays have recently increased. Experimental and in-field evaluations have been performed to validate use of solid-phase microextraction (SPME) with a porous fiber for sampling and analysis of CA in air before analysis by fast gas chromatography-mass spectrometry equipped with a new device called a multi-fiber system. CA vapor was generated by use of a syringe pump in a dynamic system in which temperature, relative humidity, and air velocity were monitored. The theoretical sampling rate for time-weighted average and rapid-SPME were, furthermore, estimated by use of the Fuller-Schettler-Giddings diffusion coefficient and the theory of heat transfer, respectively, and were in accordance with experimental values. Concentrations of CA were analyzed in a military store containing tear gas canisters, to evaluate the risk. The results obtained in this field study showed values ranging from 0.206 to 2.46 mg m−3.

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factors such as light, relative humidity, and pollutants on objects both in outdoor and indoor environments are studied in preventive conservation. To achieve this, monitoring is performed of the microclimate surrounding the object using both diffusive

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.03 Paste cubes were manufactured with a water/cement ratio equal to 0.5 and with dimensions of 3.5 cm 3 . They were cured for 24 h in a humidity chamber at 20 °C with a relative humidity greater than 95%. After the initial curing, the test specimens were

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