The thermal performance of down has to start with the way of heat transfer. Generally speaking, heat is mainly transmitted in three ways: conduction, convection and radiation. In the cold season, the heat of the human body is also dissipated to the surrounding colder space through these three ways. But in the case of wearing clothes or covering the quilt, the heat dissipation is mainly conduction.
This requires that the thermal conductivity of the thermal insulation material should be low. Feather down has the characteristics of low thermal conductivity.
Bulk Density Table of Gray Duck Down Filling
High-quality down has a high loft, which is unmatched by any other thermal material.
The loftier the insulation, the more voids there are between the fibers of the material and the more air it can hold without moving. Air is a poor conductor of heat, which can prevent heat from being conducted to the surroundings. Therefore, the higher the bulkiness, the better the thermal performance.
If the difference in thermal conductivity between fabric fibers is not considered (in fact, the difference is very small), then the thermal conductivity of down products is 20-50% lower than that of ordinary fabrics of the same thickness, that is, the warmth retention is 1-4 times higher. The higher the density of the product filler, the greater the thermal conductivity and the more heat lost. Down with a high down content has a higher bulkiness, so that the product has a lower density under the same thickness, so it has higher warmth retention.
Therefore, the use of down with a higher down content can properly reduce the weight of the filler, which can not only obtain the same warmth retention, but also reduce the weight of the product. This is why down products have the characteristics of "light, soft and warm".
The higher the down content of down, the higher its bulkiness, the better the relative warmth retention and the more comfortable it is.
The down content of down is not 100%, unless it can be achieved by manual selection, and the down content of machine sorting can reach up to 95%. The down filling must contain a certain proportion of small flakes, because the flakes can rebound quickly. Therefore, determining the appropriate down content can relatively reduce the amount of down filling and achieve the same purpose of keeping warm.
Down and other insulation materials compared
It can be seen that among the natural thermal insulation materials, the thermal insulation is the best.Down, followed by camel hair, followed by wool, camel hair and cotton.