Percent moisture uptake

The amount of water adsorbed by a solid can be expressed in a number of ways. Many investigators report the amount of water sorbed, but do not taken into account the amount of water initially in the sample. The calculation of percent moisture uptake relative to the dry weight of the sample normalizes samples to the same initial point, and makes data from various samples comparable. The percent sorbed relative to dry weight is calculated from the following ... 

Figure 16 Percent moisture uptake versus time thickness is 0.07 inch.

Figure 17 Percent moisture uptake versus time, thickness is 0.128 inch.

Table II. Percent Moisture Uptake and Diffusion Coefficient for Samples with and without Post Mold Curing as Functions of Relative Humidity and Temperature...

There also appears to exist a critical water concentration within the adhesive below which water-induced damage of the joint will not occur. This also infers that there is a critical humidity for deterioration. For an epoxy system, it is estimated that the critical water concentration is about 1.35 to 1.45 percent and that the critical humidity is 50 to 65 percent.39,40 Any loss in joint strength by the absorbed water can be restored upon drying if the equilibrium moisture uptake is below the critical water concentration. 

Fig. 37. Swelling efficiency and free volume estimation in well-cured Fi-berite 934 network epoxies, as affected by sub-Tf annealing. Percent swelling is plotted on the ordinate axis while percent of moisture uptake is plotted on the abscissa...

Nylons can reversibly absorb up to about 10 percent moisture. The moisture uptake changes dimensions and mechanical properties. Nylons 11 and 12, which have a higher proportion of hydrophobic methylene groups than nylon 6, for example, have a lower moisture uptake. Nylons can be mineral-filled or reinforced with fiber. Modifications of this... 

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