The wool fibers in road maintenance felt absorb moisture vapor from the air, which is then retained within the fibers over time—a phenomenon known as hygroscopicity of wool fibers.
Mohair fibers have a higher moisture absorbency than any other fiber. The amount of moisture absorbed by mohair is closely related to the temperature and humidity of the air. Higher relative humidity in the air results in more moisture absorption, while lower humidity leads to less. When the rate of moisture absorption by mohair equals the rate of moisture release, it is referred to as saturation.
Mohair fibers, when exposed to moisture over time, tend to experience a decrease in mechanical properties, such as strength, bending stiffness, and torsional stiffness. Therefore, semi-finished products in felt manufacturing should not be stored in excess or for extended periods. Mohair fibers release a significant amount of heat when absorbing moisture. Hence, it is crucial to store wool properly, particularly to prevent mildew when storing wool from leather factories.
After wool fibers are soaked in water, water molecules enter between the wool fiber molecules, causing the fiber molecules to expand and increase the distance between them. This results in an elongation of the fiber in the long direction and an increase in the cross-sectional diameter. This phenomenon is known as wool fiber expansion. After wool fiber expansion, it can enhance the felting property, also known as woolen felting.
