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Innovation application: Determination of Hygroscopic Sorption Properties for Solid Porous Materials

Title Determination of Hygroscopic Sorption Properties for Solid Porous Materials

The hygroscopic sorption properties of a porous material are described with sorption isotherm curves that determine the equilibrium moisture content depending on air relative humidity. This property exhibits hysteresis so both sorption (increasing the relative humidity from a dry state) and desorption (decreasing relative humidity from full saturation) is determined.

Keywords building materials testing, sorption curve, desorption curve, vapor sorption, moisture content, relative humidity
Authors Reinis Purviņš
Edīte Kamendere
Andra Blumberga
Department (11500) Vides aizsardzības un siltuma sistēmu institūts
Statistical Classification of Economic Activities, NACE 2 Other professional, scientific and technical activities
Description of the technology

A batch of samples is obtained by cutting the material. Then the batch is exposed to 6 different relative humidities according the standard EN ISO 12571:2013 and the mass is registered at regular intervals with an analytical balance. Climate is created in glass dessicators with specific saturated salt solutions. The air temperature and relative humidity is monitored during the test. Sorption curve measurements start with drying the sample while desorption curve measurements are started with full saturation of the material which can be realized in a 15 bar pressure plate extractor (this can be done in combination with the moisture retention curve test EN ISO 11274:1998 with adjustments for solid materials). Results include calculated moisture content values for all samples and derived sorption and desorption curves, including uncertainties.

Fig. 1. Determination of sorption curves with a dessicator.

Applications The hygroscopic sorption curves of a porous material describe adaptation to relative humidity and vapour transport in the material. The vapour sorption isotherms are used to synthesize the hygroscopic range of the water conductivity function. The use of these curves is incorporated in hygrothermal modelling tools such as Delphin, WUFI and others. By input of the measured values, it is possible to simulate the material in its real situation (for example, to evaluate the impact of internal insulation of a building wall constituted by previously unresearched materials).

The testing method is the most precise method available for this application so far. The sorption and desorption curves could be determined within 1 to 2 months.

Technology Readiness Level Experimental proof of concept
Partnership offer • Contracts for biofuel testing services, collaborative and interlaboratory study. • Research contracts.
ID 73
Contact information Linda Šufriča, e-mail: inovacijas@rtu.lv; phone.: 28442736