The intercalation compounds Ti(C3H7NH2)(HPO4)2·H2O (18.4 Å) (-TiP/n-Pr) and Ti(C4H9NH2)(HPO4)2·H2O (20.5 Å) (-TiP/n-Bu) have been prepared using -titanium phosphate, Ti(HPO4)2·2H2O (11.6 Å), as precursor. The retention of UO
, in aqueous solutions by -TiP is very low being only a superficial adsorption phenomenon. When the intercalated materials are used, the retention is quantitative until 95% of the cation exchange capacity in the -TiP/n-Pr case (c.e.c.=6.30 mequiv./g), and over 80% for the -TiP/n-Bu compound (c.e.c.=6.04 mequiv./g).
Authors:J. Pérez, F. Rodríguez, M. Alonso, M. Oliet, and J. Domínguez
The curing kinetics of lignin-novolac and methylolated lignin-novolac resins were studied using non-isothermal methods employing
differential scanning calorimetry (DSC) at different heating rates. The Belichmeier, Ozawa and Kissinger methods were applied,
which give the kinetic parameters of the curing process studied. In addition, the model-fitting Coats-Redfern method was used
to analyze the experimental data. The kinetic study evaluated the effect of the lignin (softwood ammonium lignosulfonate),
methylolated or not, on the resin curing process. Results for lignin-novolac and modified lignin-novolac resins were compared
with a commercial novolac resin as a reference. When lignosulfonate is modified by methylolation and is incorporated in the
novolac resin, there is an important reduction in activation energy. The lignin-novolac showed slightly higher values of activation
energy than methylolated-lignin resins, but lower values than commercial resins. This behavior has been attributed to the
extra methyol groups introduced by lignosulfonate.
Authors:M. Alonso, M. Oliet, J. García, F. Rodríguez, and J. Echeverría
Kinetics of thermosetting polymers curing is difficult to study by isothermal
methods based on the differential scanning calorimetry (DSC) technique. The
difficulty is due to the low sensitivity of the equipment for total reaction
heat measurements during high temperature process. The aim of this paper is
to display the equivalence between a dynamic model, the Ozawa method, and
an isothermal isoconversional fit, which allows predicting the isothermal
behavior of the resol resins cure through dynamic runs by DSC. In this work,
lignin–phenol–formaldehyde and commercial phenol–formaldehyde
resol resins were employed. In addition, the isothermal kinetic parameters
for both resins were performed by means of transformation of the data obtained
from the dynamic Ozawa method.
Authors:M. Villanueva, I. Fraga, J. Rodríguez-Añón, and J. Proupín-Castiñeiras
The rheological behaviour of the materials diglycidil ether of bisphenol A (n = 0), 1, 2 diamine-cyclohexane and the epoxy reactive diluent vinylcyclohexane dioxide have been studied both separately
and mixed before the beginning of the curing reaction. Different kinds of tests such as: preshear and time sweep, flow curve
and stress sweep experiments were carried out. From these experiments, interesting information about: viscosity-shear stress
and viscosity-shear rate dependences, storage modulus and the linear viscoelastic region were found out. Relationships between
concentration of diluent and the final viscosity of the mixed sample and also between percentage of diluent and storage modulus
Authors:J. Gascón, M. Rodríguez, and J. Suárez Del Rey
The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates.
Authors:R. Lucas, M. Rodríguez-Quijano, J. Vázquez, and J. Carrillo
The effects of environment and the high molecular weight glutenins on some quality properties (sedimentation volume, % protein content, and starch pasting viscosity) of bread wheat mutant waxy lines were evaluated. Thirty-eight 100% amylose-free F
lines were used. The results indicated that the environment did not influence sedimentation volume, mixograph parameters and starch viscosity parameters of waxy flour. Variation in the % protein content was determined mainly by the environment. The sedimentation volume and the mixograph peak development time were influenced by the variation at over expression of Bx7 and the mixograph peak development time was influenced by the
locus. One starch viscosity parameter, time to peak viscosity, was influenced by variation at the
locus. This parameter is significantly lower in the waxy lines than the parent line, which shows the influence of the waxy loci. No significant correlation was observed for sedimentation volume, mixograph parameters, protein content and viscosity parameters of waxy lines.
Authors:Ewa Stepkowska, M. Aviles, J. Blanes, and J. Perez-Rodriguez
The low temperature
of decomposition of some calcium carbonates and the bending of the TG curves
of hydrated cement between 500 and 800°C suggested the presence of some
complex compound(s), which needed complementary investigation (XRD, TG). Stepwise
transformation of portlandite (and/or lime) into calcium carbonate, with intermediate
steps of calcium carbonate hydroxide hydrates (CCH-1 to CCH-5), was indicated
by the previous study of two OPC.
This was checked here on four
cements ground for tg=15,
20, 25 and 30 min and hydrated either in water vapour, successively at RH=1.0,
0.95 and 0.5 for 2 weeks each (WR1, WR2 and WR3, respectively) or as mortars
in liquid water (1m), followed by WR as above. The d spacing of portlandite
was confirmed to vary: here between the lowest and the highest standard values.
The diffractograms of n=32 different samples
were analyzed for presence of standard CCH peaks, generally slightly displaced.
These were: CCH-1 [Ca3(CO3)2(OH)2]: N=11 peaks, of three different d[hkl] spacings, CCH-2 [Ca6(CO2.65)2(OH657)7(H2O)2]: N=10 for two d[hkl], CCH-3 [Ca3(CO3)2(OH)2·1.5H2O]: N=14 for five d[hkl], CCH-4,
ikaite [CaCO3(H2O)6]: N=13 for six d[hkl], CCH-5[CaCO3(H2O)]: N=15 for five d[hkl]. Thus the most probable is the presence of the
last three. The stepwise transformation of Ca(OH)2
into CaCO3 was confirmed:
portlandite (varying d)→CCH-1→CCH-2→CCH-3→CCH-4→CCH-5→CaCO3
The content of CCH was the highest at tgr=15
min, decreasing down to tgr=25
min and increasing slightly at 30 min, as inferred from the number of the
peaks observed. After cement powder hydration at RH=1.0 (WR1) peak number
increased gradually from CCH-1 to CCH-5, whereas in the hydrated mortar (1m)
the peak number decreased from CCH-1 to CCH-5, indicating the respective progress
of the carbonation reaction.
We proposed Parmelia maculoides Gyeln. as a synonym of Punctelia stictica (Delise ex Duby) Krog;Physcia hosseana Gyeln. as a synonym of Physcia stellaris (L.) Nyl. and Teloschistes exilis (Michx.) Vain. f. inaequalis Gyeln. as a synonym of Teloschistes nodulifer (Nyl.) Hill- mann based on the study of the Argentinian type material of Kofarago-Gyelnik. We also confirmed the presence of Oropogon loxensis (syn. Bryopogon hosseusianus Gyeln.) in Central Argentina by comparing the type specimen with samples collected recently. Finally we excluded the presence of Parmotrema stuppeum (Taylor) Hale from Argentina.
Authors:M. Rodríguez de Rivera, F. Socorro, and J. Matos
In this paper, it has been carried out a study to analyze the effect of the stirring velocity in the experimental determination
of the mixture enthalpies of several binary mixtures by using a Titration Calorimetric TAM2277-201/2250 by Thermometric AB.
The tested liquid mixtures have been ethanol+water and those containing 1-methyl-2-pyrrolidone and (ethanediol, 1,2-propanediol
or 1,2-butanediol). The stirring aim is to keep the homogeneity in the mixture process, but the stirring velocity must not
be increased in excess in order not to favour the evaporation during the measurement process. This study reveals that every
mixture process shows an optimum stirring velocity.