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Sueños de un visionario

  • Kant, Inmanuel
  • Canterla , Cinta
Edición crítica del texto alemán. Prólogo de Rudolf Malter. Introducción, traducción y notas de Cinta Canterla, Universidad Pablo de Olavide, Versión del editor
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Effect of crosslinker on swelling and thermodynamic properties of polyacrylamide gels

  • Baselga Llidó, Juan
  • Llorente Muga, Amaia
  • Hernández-Fuentes, I.
  • Masegosa, R.M
PAA networks have been prepared by crosslinking copolymerization of acry- lamide (AA) and N,N'-methylen-bis-acrylamide (BA) in water. The degree of swelling was measured in the range v2 =0-0.16 as a function of crosslinker proportion, C (%w/w) and total concentration, Cr (g/ 100 ml). The swelling of two networks with BA contents of 3 ,;; and 10% were measured as a function of temperature in the range 10-30°C. The interpretation of elastic and swelling data in terms of the scaling law lfh I =Av 2m, shows a transition from a good solvent regime to a collapsed state for the polymer chains, when the crosslinker proportion is around 5 to 7%. Results of elastic and swelling measurements were used to determine the x parameter. A different dependence of x with v2 was found for gels with BA contents below and above 5-7%. The enthalpic contribution to the interaction parameter XH was calculated from swelling experiments as a function of temperature. The results show that when the BA proportion is increased, the enthalpic, Financial support from CAICYT (SPAIN) under grant nc PA86/0370 is gratefully acknoweldged.
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Network defects in polyacrylamide gels

  • Baselga Llidó, Juan
  • Llorente Muga, Amaia
  • Hernández-Fuentes, I.
  • Fernández de Piérola, Inés
The weight conversion at the gel point (αGᵂ) was determined by the gas bubble method in two sets of polyacrylamide (PAA) gels crosslinked with N,N′-methylene-bisacrylamide (BA). αGᵂ remained practically constant when the crosslinker ratio was C = 10% (w/w) and the total concentration of comonomers in the feed ranged from CT = 5 to 10 g/100 ml. When CT was kept constant at 5 g/100 ml and C changed from 0 to 25% (w/w), αGᵂ showed a minimum at C = 7%. By comparing the experimental values of αGᵂ with those calculated for an ideal network, it was concluded that the crosslinking efficiency of BA is very low. The dependence on C of αGᵂ and other properties like the elastic phantom modulus, |ƒₚₕ*|, and the polymer volume fraction at swelling equilibrium, v₂ₛo, was explained in terms of the formation of network defects: the formation of BA sequences longer than unity and that of intramolecular cycles both have an increasing contribution at C > 7% but can be neglected at lower values of C., This work has been supported by a grant from CAICYT No. GG85-0013. The authors thank Dr A. Horta and Dr J. J. Freire for many helpful discussions.
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Polyacrylamide gels. Process of network formation

  • Baselga Llidó, Juan
  • Llorente Muga, Amaia
  • Hernández-Fuentes, I.
  • Fernández de Piérola, Inés
This paper refers to the crosslinking copolymerization of acrylamide (AA or monomer-1) and N,N′-methylene-bisacrylamide (BA or monomer-2) in aqueous solution at 22°, covering a broad range of comonomer concentrations. The extent of reaction, pT, the composition of the remaining comonomer mixture, f₂, and the copolymer composition, F₂, have been determined by high resolution 1H-NMR with polymerization in situ. The non-linear regression fit of f₂ as a function of pT yields almost the same values for the reactivity ratios for any of the studied comonomers feeds. The instant copolymer composition changes with the copolymerization time due to a shift in the residual comonomer composition and, to a smaller extent, to changes in the comonomer relative reactivities. This effect contributes to the heterogeneity of the final network., Financial support from CAICYT (Spain) under Grants No. GG85/0013 and PA86/0370 is gratefully acknowledged. We are also indebted to Dr R. Gonzalez Rubio for his computer assistance, and to Dr J. Guzman for sorne interesting comments.
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Factorial Design in Cement Raw Mix Reactivity Investigation, Diseño factorial en la investigación de la reactividad de los crudos de cemento

  • Duque Fernández, Gabriel Luis
  • Cardoso Camacho, Josefina de las Mercedes
  • Rubio Frías, Ester
  • Muller, Wilhem
The present paper corroborates, that experimental design technics are applicable to raw mix burnability investigations, and with it the obtained results could cover all the range of possible concentrations of industrial interest. Obtained results agree with theory. A negative interaction was found between lime saturation factor (LSF) and silicate module (Ms) in raw mix burnability and in cement reactivity. In the concentration range studied, working with high LSF and low Ms is recommended., En el presente trabajo se corrobora que las técnicas de diseño de experimento son aplicables a las investigaciones de facilidad de quema de los crudos de cemento, obteniéndose resultados que, abarcando el rango de concentraciones de interés industrial, concuerdan de forma satisfactoria con lo esperado por la teoría, con considerable ahorro de tiempo y dinero. Se encontró una interacción con signo negativo entre el factor de saturación de cal (FSC) y el módulo de sílice, tanto en facilidad de quema de crudos como en reactividad del cemento. Se recomienda trabajar con factor de saturación de cal alto y módulo de sílice bajo para el rango de concentraciones estudiado.
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Influence on the physical-mechanical properties of portland-cement mortar, have admixtures of colophony and tannin, Influencia que sobre las propiedades físico-mecánicas de los morteros de cemento Portland tiene la adición de colofonia y tanino

  • Fernández Cánovas, M.
  • Hurtado Selva, N.
  • Kawiche, G. M.
The colophony has been used as an admixture in the Portland cement mortar with the intention to observe its influence on the air content, water absorption, adhesive capacity and mechanical properties. The results obtained have shown that, the colophony acts as air entrainment, reduces the permeability and improves the adhesion between the past and aggregates. Likewise, the addition of tannin and montan wax to the colophony has the efect of reducing the formation of foam and improves the impermeability of the mortar., Se ha empleado la colofonia como aditivo en el mortero de cemento portland con el fin de observar su influencia sobre el contenido de aire, absorción de agua, capacidad adhesiva y propiedades mecánicas. Los resultados obtenidos han puesto de manifiesto que la colofonia actúa como aireante, aumenta la impermeabilidad y mejora la adherencia de la pasta al árido. Asimismo, la adición de tanino y cera montana a la colofonia tiene el efecto de reducir la formación de espuma y mejorar también la impermeabilidad del mortero.
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Study by X-ray difraction of the alites and the influency of the quenching in it's structure and it's crystalline system, Estudio por difracción de rayos X de alitas y la influencia del templado en la estructura y en el sistema cristalino

  • Triviño Vázquez, F.
It is studied the influence of Fe, Al and Mg in the changes that have been produced by quench in the crystalline system of the alite and so it possible relation with the mechanical resistances., Este trabajo trata sobre el estudio de la influencia del Fe, Al y Mg en los cambios que han sido producidos por templado en el sistema cristalino de las alitas y su posible relación con las resistencias mecánicas.
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