Authors:J. Doležal, J. Stejskal, M. Tympl, and V. Kouřím
The possibility of using the sol-gel method for preparation of inorganic ion-exchangers with a silica gel matrix has been
demonstrated on the ammonium molybdophosphate-silica gel (AMP-SG) system. For the preparation of the ion-exchanger a sodium
silicate solution, containing AMP and components to cause gelling to silica gel after increase of the temperature of the solution,
is poured into a hot stirred silicone oil. The solution forms droplets, which are filtered off after their gelling, washed
and dried. Beads containing 65 wt.% of AMP per gram of dry material have been prepared by this method and tested in ion-exchange
columns for caesium removal from nitric acid solutions. Caesium may easily be desorbed with ammonium chloride or nitrate solutions.
The ion-exchanger is suitable for long-time reversible column operation, having not only good chemical, thermal and radiation
stabilities but also good mechanical and hydrodynamic properties and resistance to abrasion. It combines the advantage of
the good kinetics of ion-exchange obtained with microparticles of precipitated inorganic ion-exchanger, with the low flow
resistance of large particles.
Effect of hydrolysis time on molar mass, glass transition temperature, crystallinity, and resistance to thermooxidation at
elevated temperatures was analyzed for Estanes 54600, 54610, and 54650. Kinetics of the hydrolysis can be plausibly described
in terms of the first-order reaction with an average induction period of about 7 days. Reduction of molar mass induced by
hydrolysis brings about an appreciable decrease in glass transition temperature, fraction of crystalline domains of soft segments,
and thermooxidative stability. The latter effect is manifested by shortening of the lifetimes (related to 5% mass loss) the
temperature dependence of which obeys the Arrhenius plot. The observed differences in hydrolysis resistance of Estanes can
be related to their chemical composition.
Authors:E. Renacco, J. Kaloustian, C. Arfi, A. Pauli, and J. Pastor
Fire resistance of polyethylene is realized by magnesium hydroxide which is distinguished from halogenated fire-proofing agents
by its lower cost and its non toxicity. Magnesium hydroxide decomposed by an endothermic reaction with liberation of water,
contributing to fire proofing. The sample used (Kisuma 5A-N*) is constituted from a powder (0.6–0.8 micrometre) its surface is treated by plastic material in order to ameliorate its
We studied the thermal decomposition by DTA and TG, of mixtures constituted by polyethylene and magnesium hydroxide. A sudden
decomposition began at 385°C for pure polyethylene and decomposition took place at 429°C for the mixture polyethylene-Kisuma
(50–50). Incorporation of magnesium hydroxide in polyethylene increases fire resistance.
Authors:T. Nakanishi, K. Don-Jin, T. Kitamura, R. Ishii, and M. Matsubayashi
Cowpea (Vigna unguliculata Walp) is considered one of the most drought resistant species among the pulse crops. It was suggested that in the lower part
of the stem, parenchymatous tissue for storing water has been developed for the function of drought resistance. However, such
tissue has not been identified yet. In order to identify the water storing tissue in the stem of cowpea plant, the authors
performed neutron radiography, which provides a non-destructive image of water distribution pattern in a plant. Common bean
plant and soybean plant were used as references. Comparing the neutron radiograph for the stems of the plants, i.e., cowpea,
common bean and soybean plants, the parenchymatous tissue with water storing function was distinguished in the intermode between
primary leaf and the first trifoliate leaf specifically in cowpea plant.
Authors:N. Jaffrezic-Renault and H. Andrade-Martins
We have studied the phenomenon of retention of uranium, as a carbonato complex UO2(CO3)
on titanium oxide. We first proposed a method for preparing titanium oxide whose ion-exchange capacities (2.9 meq Na+/g, 0.11 meq UO
/g) and physical properties (mechanical resistance and granulometry) make it quite suitable for liquid chromatography and
particularly for the extraction process of uranium from sea-water. We prepared the sodium tricarbonatouranate, the major form
of uranium in sea-water. We studied the retention of this compound on titanium oxide. From a thermodynamic study of the retention
equilibrium we proposed a retention mechanism of the ligang-exchange type: uranyl is retained on titanium oxide, surrounded
with two CO
ligands and two ≥TiO− ligands. We shown that 2/3 of the exchanged hydroxyl groups have pKH1=4.9 and 1/3 of them have pKH2=9.3.
Authors:Michelle Mothé, Leni Leite, and Cheila Mothé
The quality of a road relies on the good use of the on road surface and its maintenance along the years. The technology used
and the corrections contributes to the prevention of early road destructions. Pavement with polmyer and others additives exhibits
greater resistance to rutting, thermal cracking, and decreased fatigue damage, stripping and temperature susceptibility. Samples
of CAP 40, SBS 440/02, L 1861/04, L 784/05 and L 2000/04 were analyzed by thermogravimetry (TG), derivative thermogravimetry
(DTG), differential thermal analysis (DTA) and FTIR. Thermal characterizations showed that the main decomposition stage refers
to asphaltenes and samples with additives exhibited a slight increase in thermal stability. The kinetic study, by Kissinger,
showed that the sample with the highest stability was the SBS 440/02. Fourier transform infrared spectroscopy (FTIR) analysis
suggested that these asphalt samples were originated from light oil.
Authors:J. Pak, W. Qiu, M. Pyda, E. Nowak-Pyda, and B. Wunderlich
During a prior study of gel-spun fibers of ultrahigh-molar-mass polyethylene, a substantial error was observed on calculating
the heat capacity with a deformed pan, caused by the lateral expansion of the fibers on shrinking during fusion. In this paper,
the causes of this and other effects that limit the precision of heat capacity measurements by DSC and TMDSC are explored.
It is shown that the major cause of error in the DSC is not a change in thermal resistance due to the limited contact of the
fibers with the pan or the deformed pan with the platform, but a change in the baseline. In TMDSC, the frequency-dependence
is changed. Since irreversible changes in the baseline can occur also for other reasons, inspections of the pan after the
measurement are necessary for precision measurements.
Authors:J. Gonçalves, R. Toledo Filho, and E. Fairbairn
This paper reports an experimental study on the magnesium sulphate resistance of mortar specimens incorporating 0, 10 and
20% of metakaolin (MK). The evidence of the attack was evaluated through the content of calcium hydroxide (portlandite) and
formation of magnesium hydroxide (brucite) by thermal analysis (thermogravimetric and derivative thermogravimetric analysis).
The mechanical degradation of the mortar specimens was evaluated through splitting tensile tests after 200 days of exposition
to the magnesium solution. The addition of metakaolin resulted in a reduction in the content of calcium hydroxide and in a
smaller formation of brucite in comparison with reference mixture. A tensile strength loss of about 7% was observed for the
metakaolin mortars submitted to the magnesium solution attack for 200 days.