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MATERIALS:

WOOD and PAPER

Artículos científicos

UNIVERSIDAD POLITÉCNICA DE MADRID © 2017

51

Thermodynamic properties of the water sorption isotherms of wood of limba (Terminalia superba Engl. & Diels), obeche (Triplochiton scleroxylon K. Schum.), radiata pine (Pinus radiata D. Don) and chestnut (Castanea sativa Mill.). Industrial crops and products. 94:122–131.



Abstract:   The sorption isotherms of limba (Terminalia superba Engl. & Diels), obeche (Triplochiton scleroxylon K.Schum.), radiata pine (Pinus radiata D. Don) and chestnut (Castanea sativa Mill.), were plotted at 15 ºC, 35 ºC and 50 ºC. The curves were fitted using the Guggenheim-Anderson-de Boer (GAB) model. The thermodynamic properties (net isosteric heat of sorption, total heat of wetting, differential entropy and spreading pressure) were determined from the isotherms to define the energy associated with the sorption processes. Net isosteric heat of sorption was obtained using the Clausius-Clapeyron equation and showed a negative relation with moisture content. Differential entropy showed the same behaviour. These two parameters were higher in desorption than in adsorption. Total heat of wetting was also higher in desorption than in adsorption and higher in chestnut than in the other species. The enthalpy-entropy theory was validated as there was a good linear fit between net isosteric heat of sorption and differential entropy, and the isokinetic temperatures were different from the harmonic mean temperature. Using the enthalpy-entropy theory, it was possible to conclude that the adsorption and desorption processes were enthalpy driven and spontaneous. Spreading pressure increased as water activity increased. The variation of spreading pressure with temperature depends on the species type.

 


Simón, C.

Esteban, L. G.

de Palacios, P.

García Fernandez, F.

García-Iruela, A.


2016

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WEB Science

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53

Sorption and thermodynamic properties of wood of Pinus canariensis C. Sm. ex DC. buried in volcanic ash during an eruption. 51(3):517–534



Abstract:   The hygroscopicity and thermodynamic properties of Pinus canariensis wood buried in volcanic ash and dating from 1100 BC were studied and compared with recently felled juvenile and mature wood of the same species. The sorption isotherms were obtained by the saturated salt method at 35 ºC and 50 ºC. The isotherms were fitted using the Guggenheim-Anderson-de Boer (GAB) model. The thermodynamic parameters were determined following the Clausius-Clapeyron integration method. To understand the behaviour of each type of wood, the chemical composition, infrared spectra (FTIR) and X-ray diffractograms were determined for each sample.

The mature wood has a higher sugar content and lower extractive content than the juvenile and the buried wood. For both temperatures, the isotherm of the mature wood is above the isotherm of the juvenile wood and this, in turn, is above the isotherm of the buried wood, primarily influenced by the higher cellulose and hemicellulose content and lower extractives content in the mature wood, resulting in a higher number of accessible -OH groups. Degradation of the buried wood due to high temperatures explains why its isotherms are below the isotherms of the recent wood.

The energy involved in the desorption process is greater than in adsorption. Similarly, more energy is involved in the mature wood than in the juvenile wood, and the energy involved in the juvenile wood is greater than in the buried wood.

 


Simón, C.

Esteban, L. G.

de Palacios, P.

García Fernandez, F.

García-Iruela, A.

Martín-Sampedro,  R.

Eugenio, M. E.


2017

52

Sorption/desorption hysteresis revisited. Sorption properties of Pinus pinea L. analysed by the parallel exponential kinetics and Kelvin-Voigt models. Holzforschung. 71(2):171-177.



Abstract:   The hygroscopic properties of Pinus pinea L. wood at 35 and 50°C were investigated by the dynamic vapour sorption (DVS) technique. The sorption kinetic behaviour was studied through the parallel exponential kinetics (PEK) model, which is subdivided into a fast and a slow process. The parameters obtained by PEK were interpreted based on the Kelvin-Voigt (KV) model to determine elasticity and viscosity values of the wood cell wall. The PEK data perfectly fit the experimental data. The temperature-dependent transition between the fast and slow processes is fluent. The slow process contributes more to the total hysteresis of sorption. The kinetic properties varied in relation to the type of cycle and the temperature. The moduli of elasticity and viscosity were higher in the slow process than in the fast one. In both processes, the moduli showed a decreasing tendency in relation to relative humidity.

 


Simón, C.

Esteban, L. G.

de Palacios, P.

García Fernandez, F.

García-Iruela, A.


2017

54

Comparative wood anatomy of the Cupressaceae and correspondence with phylogeny, with special reference to the monotypic taxa. Plant Systematics and Evolution. 303(2): 203–219



Abstract:   Wood anatomy is one of the tools used for taxonomic classification of species. By combining this tool with molecular phylogeny, the current groupings made in morphological studies can be discussed. This study describes the wood anatomy of the monotypic genera of Cupressaceae and analyses the features that could represent synapomorphies of the principal clades recovered by molecular phylogeny. The wood anatomical study shows the high homogeneity of this family, revealing the presence of common ancestral features that support the union between Taxodiaceae and Cupressaceae s.s. and the separation of Sciadopitys. It also supports the group formed by Taxodiaceae in Cupressaceae s.l. No clear division was observed between the callitroid and cupressoid clades. Some wood anatomical differences were observed in the Fitzroya–Diselma–Pilgerodendron and Microbiota–Platycladus–Tetraclinis associations. The wood anatomical features common to the family, such as axial tracheids without helical thickenings, homogeneous rays, cupressoid cross-field pits and the presence of a warty layer, are put forward as possible synapomorphies for Cupressaceae s.l. The clade-specific synapomorphies are taxodioid cross-field pits for taxodioid and sequoioid clades, absence of a well-defined torus in Thuja–Thujopsis and torus extensions in Diselma–Fitzroya–Widdringtonia.

 

Román-Jordán, E.

Esteban, L. G.

de Palacios, P.

García Fernandez, F.



2017

55

Comparison of the saturated salt and dynamic vapor sorption methods in obtaining the sorption properties of Pinus pinea L. Eur. J. Wood Prod. 

DOI 10.1007/s00107-016-1155-6



Abstract:   Several  methods  are  available  for  obtaining  the  sorption isotherms  of  wood.  Among  these,  the  saturated  salt  and  dynamic  vapor  sorption methods  are  the most  frequently  used ones.  For  the  first  time,  the  hygroscopic response  of  wood  obtained  using  these  two  methods  is  compared. This  is  done  by determining  the  35 and 50 °C  adsorption  isotherms  of  juvenile  and  mature  wood of Pinus  pinea  L.  The  hygroscopic  behavior  of  the  two types of wood is different, as the mature wood has a higher moisture content than the juvenile wood in the isotherms studied. Comparison of the static saturated salt method and dynamic  vapor  sorption  shows  few  significant  differences between the equilibrium moisture content obtained by each method  during  the  adsorption  process,  both  in  a  point  by point comparison and in the comparison of quadratic polynomial forms of the Guggenheim Anderson de Boer model. Moreover,  in both methods  the point  of relative humidity from which multilayer  sorption  predominates  over  monolayer sorption is similar.

 

Simón, C.

García Fernandez, F. Esteban, L. G.

de Palacios, P.

Hosseinpourpia, R. Carsten, M.


2017

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