The stability of Supersulphated Cement (SSC) is investigated at 95°C when subjected to relative humidities of 100, 53 and
11% of water vapour. Previously  investigations at 25, 50, 75°C under the same conditions of humidity reported the stability
of ettringite, one of the initial hydration products. At 95°C, decomposition of ettringite, is found at all humidities and
is rapid at 100% relative humidity. The hydration products of cement pastes at a water cement ratio of 0.27 were determined
by thermogravimetry (TG) and X-ray diffraction (XRD).
The formation of the hydragarnet, plazolite is recorded during the decomposition/dehydration process enhanced by possible
carbonation. Rehydration studies on the products after storage for up to 9 months were carried out using distilled water and
the samples tested for ettringite content. It is concluded that ettringite in SSC is inherently unstable at 95°C.
Authors:J. KŐmives, K. Tomor, J. Sztatisz, L. Lassu, and S. Gál
Changes in the water content of aluminium sulphate hydrate were investigated gravimetrically at room temperature in air with different relative humidities. The samples conditioned in this way were characterized by thermoanalytical (TG, DTG, DSC) and X-ray diffraction measurements. Industrial aluminium sulphate hydrate obtained by freezing the melt has a partly crystalline structure. After grinding, this material crystallizes during storage. This process requires a humid atmosphere; increasing relative humidity brings about more intensive crystallization.
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.
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.
using the blends of sulfoaluminate ferrite belite (SAFB) clinkers and ordinary
Portland cement (OPC) in mass ratio 85:15 with Al2O3,
and starch, polyphosphate (poly-P) or butylacrylate/acrylonitrile were subjected
to moist atmospheres (ambient, 52 and 100% relative humidity (RH)) to investigate
their moisture resistance. Their chemical, thermal, electron microscopic and
magnetic properties were also studied before and after moisture attack. Butylacrylate/acrylonitrile
(BA/AN) copolymer was found to be the most suitable for MDF cement synthesis
since the sample containing BA/AN showed the best moisture resistant. There
are significant differences in scanning electron microscopy (SEM) of MDF cements
before and after moisture attack and with different polymers. New data on
the paramagnetic nonhysteresis magnetization curves for all the samples are
observed. The MDF cements synthesized from SAFB clinker with dissolved poly-P
give the best signal/noise (S/N) ratio. Three main temperature regions on TG curves
of both series of MDF cements are observed. In the inter-phase section of
MDF cements, the content of classical cement hydrates decomposing by 250C
is increased. Combustion of organic material took place by 550C. In the
temperature range 550-800C, the decomposition of CaCO3
Authors:I. Bravo-Osuna, A. Muńoz-Ruiz, M. Jiménez-Castellanos, J. Ford, and M. Whelan
The use of modulated temperature differential scanning calorimetry (TMDSC) and differential scanning calorimetry (DSC) in the measurement of the glass transition temperature (Tg) 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 Tg 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.
Authors:D. Giron, Ch. Goldbronn, M. Mutz, S. Pfeffer, Ph. Piechon, and Ph. Schwab
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.
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.
The interaction between samples of metallic zinc and water vapour was studied gravimetrically, both in the absence and in
the presence of oxygen. The experimental total mass gain vs. time curves exhibited two plateaus, whose heights increased with,
elevations both of relative humidity and of temperature. The amount of product retained on the surface after desorption was
also determined as a function of time. The product was identified as hydrated zinc oxide. In the runs conducted without oxygen,
the retained product curves displayed a time delay with respect to the total mass gain curves. In the presence of oxygen,
however, there was practically only one chronogravimetric curve. This behaviour is interpreted on the basis of a common mechanism
involving the formation of an intermediate precursor oxide, which is more readily formed in the presence of oxygen than in
its absence. A set of mathematical equations was derived, from which the rate constants for both processes were obtained.
The second step was ascribed to a further weak adsorption of water.
The CISORP Water Sorption Analyser has been used to characterise a selection of solid samples at relative humidities from
0 to 100% and at ambient pressure. The analysis reveals many interesting features about the samples and shows the scope of
Hysteresis due to porosity and differences in the physical properties of similar chemical samples show up clearly in isotherm
curves. Kinetic curves reveal features such as the level of stability of dehydrated food products, changes in the hydration
states of salts, and the effect of adding powdered excipient on the water sorption behaviour of a pharmaceutical compound.
Kinetic curves were also used to compare the water sorption behaviour of two types of wood found inside a pine cone, and to
determine equilibrium moisture sorption by calculation.
It was shown that many samples take up moisture irreversibly under the experimental conditions such as amorphous sucrose and
other freeze-dried samples, as well as unstable crystalline forms of compounds. Wet samples such as soaked brick and archaeological
wood from a well dry out irreversibly even at 100% RH.
Recording isotherms at different temperatures allows the calculation of enthalpies of water sorption. If these are compared
with the enthalpy of water condensation the two processes can be compared quantitatively.