scholarly journals Water Vapor Sorption and Diffusivity in Bio-Based Poly(ethylene vanillate)—PEV

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 524
Author(s):  
Greta Giacobazzi ◽  
Claudio Gioia ◽  
Micaela Vannini ◽  
Paola Marchese ◽  
Valérie Guillard ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Sorption Isotherms ◽  
Sorption Process ◽  
Water Vapor Sorption ◽  
Gravimetric Analysis ◽  
Vapor Sorption ◽  
Wide Range ◽  
Poly Ethylene ◽  
Segmental Flexibility

The dynamic and equilibrium water vapor sorption properties of amorphous and highly crystalline poly(ethylene vanillate) (PEV) films were determined via gravimetric analysis, at 20 °C, over a wide range of relative humidity (0–95% RH). At low RH%, the dynamic of the sorption process obeys Fick’s law while at higher relative humidity it is characterized by a drift ascribable to non-Fickian relaxations. The non-Fickian relaxations, which are responsible for the incorporation of additional water, are correlated with the upturn of the sorption isotherms and simultaneously the hysteresis recorded between sorption and desorption cycles. The sorption isotherms of amorphous and highly crystalline PEV are arranged in the same concentration range of that of PET proving the similarity of the two polyesters. Water diffusion coefficients, whose determination from individual kinetic sorption/desorption curves required treatment with the Barens–Hopfenberg model, were demonstrated to be ≈10× higher for amorphous PEV compared to amorphous PET. Such a difference originates from the enhanced segmental flexibility of PEV chains.

THE ADSORPTION OF ALIPHATIC ACIDS FROM AQUEOUS SOLUTIONS BY POROUS CARBONS

1955 ◽  
Vol 33 (2) ◽  
pp. 330-343 ◽  
Author(s):  
John L. Morrison ◽  
David M. Miller
Keyword(s):  
Water Vapor ◽  
Solid State ◽  
Aqueous Solutions ◽  
Pore Size ◽  
Carboxylic Acids ◽  
Sorption Isotherms ◽  
Water Vapor Sorption ◽  
Vapor Sorption ◽  
Melting Points ◽  
General Phenomenon

The maximum adsorptions of the lower members of the mono- and di-carboxylic acids from aqueous solutions were determined for coconut charcoals of different degrees of activation. Based on these results, a method for estimating pore size was applied to the more finely porous charcoals. To corroborate the pore sizes estimated from acid adsorption, pore size – area distributions were calculated from measurements of the water vapor sorption isotherms of the charcoals. An alternation in the maximum amounts of adsorbed acids was observed with the more active charcoals. Acids with an even number of carbon atoms had larger adsorptions than acids with an odd number. The alternation was much more marked for the di- than for the mono-carboxylic acids. A remarkable correlation between the alternation of adsorptions and of melting points of both acid series was observed. An explanation for the general phenomenon of alternation based on rotational motion of molecules in the solid state is given as an alternative to the widely held one based on tilting of molecular chains.

scholarly journals Phase Transitions in Ion-Exchange Materials during the Water Vapor Sorption

2021 ◽  
Vol 248 ◽  
pp. 01003
Author(s):  
Igor Ivanov ◽  
Oksana Ivanova
Keyword(s):  
Phase Transitions ◽  
Water Vapor ◽  
Ion Exchange ◽  
Liquid Film ◽  
Mutual Influence ◽  
Hysteresis Loops ◽  
Sorption Process ◽  
Water Vapor Sorption ◽  
Water Vapor Adsorption ◽  
Vapor Sorption

Water vapor sorption process on ion-exchange materials was investigated using a model taking into account the mutual influence of variations in hydration energy and osmotic effect. At realistic parameter values, phase transitions of the first kind of the thin adsorbed liquid film and thick adsorbed liquid film type can occur. Possible reasons and criteria of the phase transitions that led to stepwise change of ionite resistance were discussed. The phase transitions obtained in this work manifest themselves as hysteresis loops on water vapor adsorption-desorption experimental isotherms. Hysteresis was observed experimentally both at high and at low values of relative air humidity. It was explained using different models: for high and low humidity separately. The present work made it possible to explain these critical phenomena using single mathematical model.

scholarly journals Study of Hydrophilic Properties of Polysaccharides

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Michael Ioelovich
Keyword(s):  
Water Vapor ◽  
Structural Characteristics ◽  
Sorption Isotherms ◽  
Water Vapor Sorption ◽  
Water Molecules ◽  
Vapor Sorption ◽  
Direct Proportion ◽  
Polar Groups ◽  
Sorption Of Water Vapor ◽  
Chitin And Chitosan

In this research, the structural characteristics, specific surface area, sorption of water vapor, and wetting enthalpy of various polysaccharides (cellulose, hemicelluloses, starch, pectin, chitin, and chitosan) have been studied. It was confirmed that crystallites are inaccessible for water, and therefore water molecules can interact only with polar groups in noncrystalline (amorphous) domains of biopolymers. The isotherms of water vapor sorption for various polysaccharides had sigmoid shapes, which can be explained by the absorption of water molecules in heterogeneous amorphous domains having clusters with different packing densities. The method of contributions of polar groups to sorption of water molecules was used, which allowed to derivate a simple calculating equation to describe the shape of sorption isotherms. The wetting of biopolymers with water was accompanied by a high exothermic thermal effect, in direct proportion to the amorphicity degree. The sorption values and wetting enthalpies of amorphous domains of biopolymers were calculated, which allowed to find the hydrophilicity index and compare the hydrophilicity of the various polysaccharides.

scholarly journals Kinetics of Water Vapor Sorption in Wood Cell Walls: State of the Art and Research Needs

Forests ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 704 ◽  
Author(s):  
Emil Engelund Thybring ◽  
Samuel V. Glass ◽  
Samuel L. Zelinka
Keyword(s):  
Water Vapor ◽  
State Of The Art ◽  
Theoretical Models ◽  
Sorption Process ◽  
Sorption Kinetics ◽  
Water Vapor Sorption ◽  
Fundamental Aspect ◽  
Vapor Sorption ◽  
Transfer Resistance ◽  
New Models

Water vapor sorption is the most fundamental aspect of wood-moisture relations. It is directly or indirectly related to the physical properties of wood and the onset of wood-damage mechanisms. While sorption properties of cellulosic materials have been utilized since antiquity, the time-dependent transition from one moisture content to another (i.e., sorption kinetics) has received much less attention. In this critical review, we present the state-of-the-art of water vapor sorption kinetics in wood. We first examine different experimental methods that have been used to measure sorption kinetics, from the quartz helix vacuum balance beginning in earnest in the 1930s, to automated sorption balances used recently. We then give an overview of experimental observations and describe the physical phenomena that occur during the sorption process, which potentially govern the following kinetics: boundary layer mass transfer resistance, heat of sorption, cell wall diffusion, swelling, and polymer mobility. Finally, we evaluate theoretical models that have been proposed for describing sorption kinetics, considering both experimental data and the physical processes described in the previous section. It is clear that no previously developed model can phenomenologically describe the sorption process. Instead, new models are needed. We conclude that the development of new models will require more than simple gravimetric measurements. In addition to mass changes, complementary techniques are needed to probe other important physical quantities on multiple length scales.

A new model for soil water vapor sorption isotherms considering adsorption and condensation

2020 ◽  
Author(s):  
Chong Chen ◽  
Emmanuel Arthur ◽  
Hu Zhou ◽  
Xiang Wang ◽  
Jianying Shang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Soil Water ◽  
Sorption Isotherms ◽  
Water Vapor Sorption ◽  
Vapor Sorption ◽  
New Model
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