Absorption of Moisture by Fibrous Insulating Materials

Abstract

We studied the absorption of moisture by Various fibrous insulating materials. At first, the sample is dried for several days by placing it in a hygrostat containing concentrated diluted sulphuric acid, and its weight is measured; then the acid is step by step up to the relative humidity 95%. The relation between the absorption of moisture and relative humidity is expressed in the following formula which is concordant with observed values for a range of zero to 95 Percent by relative humidity.
Q=1/a/H+b-cH.
where Q=moisture absorbed in percentage.
H=relative humidity in percentage.
a.b.c=constants depending upon insulating materials.
The absorption of moisture by fibrous insulating Materials depends on the mode of variation of humidity. A considerable difference is observed in the quantity of moisture absorbed, whether the humidity varies from dry to wet or wet to dry. That is, there are hysteresis phenomena in the absorption of moisture by fibrous materials. All of the above experiments are conducted in a thermostat of constant temperature of 30°C.
In order to ascertain the effect of temperature rise on the absorption of moisture, the concentration of the sulphuric acid in the vessel being maintained constantly and the temperatere of the surrounding of the vessel being varied, the change of weight of the sample is observed. The weight of the sample does not change so much, but it decreases very little with temperature rise.
Lastly, by utilizing toe phenomena of temperature rise of a sample caused by the absorption of moisture, we compared the absorption of moisture by various samples in vacuum. This method does not give accurate absolute value of the absorption of moisture, but it is convenient to compare many samples in a short time.