2023, Majka, Jerzy, Perdoch, Waldemar, Czajkowski, Łukasz, Mazela, Bartłomiej, Olek, Wiesław

AbstractSorption properties of paper products are important when applying paper as the packaging material. Hydrophobicity, i.e. reduced affinity of paper surface to liquid water, is of particular importance from the point of view of the direct impact on packed goods. However, hygroscopicity of the material is significant during storage of goods. The analysis of changes in the hygroscopic properties of paper products induced by the treatment with silane modified starch was presented. The results on the hygroscopicity of treated paper were related to the previously published results on the hydrophobicity. The discrete values of equilibrium moisture content allowed constructing adsorption and desorption isotherms. The three-parameter Guggenheim, Anderson, and De Boer (GAB) model, the four-parameter Generalized D’Arcy and Watt (GDW), and Yanniotis and Blahovec (Y-B) sorption isotherm models were used to quantify the hygroscopic properties for all options of untreated and modified paper samples. The effectiveness of silanes for improving hygroscopic properties was determined and compared to their impact on hydrophobicity of the studied materials. It was found that 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane was the only silane improving hydrophobic and hygroscopic properties. The analysis of the applied models of sorption isotherms depicted that the GAB model was not valid for describing water sorption isotherms in the case of the tested materials, while the GDW and Y-B models provided a much more realistic description of water sorption mechanisms. The evaluation of the results of fitting the GDW model indicated that water molecules bonding to the primary sites was the dominating mechanism of sorption.

2025, Zelinka, Samuel L., Glass, Samuel V., Farkas, Natalia, Thybring, Emil E., Altgen, Michael, Rautkari, Lauri, Curling, Simon, Cao, Jinzhen, Wang, Yujiao, Künniger, Tina, Nyström, Gustav, Dreimol, Christopher Hubert, Burgert, Ingo, Roper, Mark G., Broom, Darren P., Schwarzkopf, Matthew, Yudhanto, Arief, Subah, Mohammad, Lubineau, Gilles, Fredriksson, Maria, Olek, Wiesław, Majka, Jerzy, Pedersen, Nanna Bjerregaard, Burnett, Daniel J., Garcia, Armando R., Dreisbach, Frieder, Waguespack, Louis, Schott, Jennifer, Esteban, Luis G., García‑Iruela, Alberto, Colinart, Thibaut, Rémond, Romain, Mazian, Brahim, Perré, Patrick, Emmerich, Lukas

Abstract Automated sorption balances are widely used for characterizing the interaction of water vapor with hygroscopic materials. This paper is part of an interlaboratory study investigating the stability and performance of automated sorption balances. A previous paper in this study investigated the mass, temperature, and relative humidity (RH) stability of automated sorption balances by looking at the mass change of a non-hygroscopic sample over time. In this study, we examine the mass stability of wood samples held at constant RH for seven to ten days after a step change. The reason for the long hold times was to collect data to “operational equilibrium” where the change in mass is on the order of the inherent operational stability of the instrument. A total of 80 datasets were acquired from 21 laboratories covering absorption with final RH levels ranging from 10 to 95%. During these long hold times, several unusual behaviors were observed in the mass-vs-time curves. Deviations from expected sorption behavior were examined by fitting the data to an empirical sorption kinetics model and calculating the root mean square error (RMSE) between the observed and smoothed behavior. Samples that had a large RMSE relative to the median RMSE of the other datasets often had one of several types of errors: abrupt disturbances, diurnal oscillations, or long-term mass decline during an absorption step. In many cases, mass fluctuations were correlated with changes in the water reservoir temperature of the automated sorption balance. We discuss potential errors in sorption measurements on hygroscopic materials and suggest an acceptable level of RMSE for sorption data.