Wool keeps us warm even though it has low thermal conductivity due to its unique structure and properties. Here are some reasons why wool is effective at providing insulation and retaining heat:
Air Trapped within the Fibers: Wool fibers have a three-dimensional structure with overlapping scales or cuticles. These scales create tiny air pockets between the fibers, effectively trapping air. Air is a poor conductor of heat, so the trapped air acts as an insulating layer, reducing heat transfer.
Moisture Management: Wool has the ability to absorb and release moisture, making it a hygroscopic material. When the air surrounding the wool fibers becomes humid, the wool absorbs moisture, preventing the accumulation of sweat or water vapor on the skin. The absorption of moisture generates heat, which helps to keep the body warm.
High Bulk and Loft: Wool fibers are crimped, meaning they have natural bends and curls. This crimped structure gives wool a high bulk and loft, creating more air spaces within the fabric. These air pockets further enhance the insulating properties by trapping more warm air and reducing convective heat loss.
Natural Resistance to Fire: Wool has a higher ignition temperature compared to many synthetic fibers. This fire-resistant property makes it suitable for insulation, as it provides an additional layer of protection against heat loss due to combustion.
Moisture Vapor Transmission: While wool can absorb moisture, it also has the ability to release it through a process called moisture vapor transmission. This allows the fabric to stay dry and maintain its insulating properties even when exposed to moisture.
Overall, the combination of wool's ability to trap air, manage moisture, provide bulk and loft, resist fire, and maintain insulation even in the presence of moisture contributes to its effectiveness in keeping us warm, despite its low thermal conductivity.