There are so many types of winter clothes, why do we love down jackets the most?

Key Points

★ Down jackets are the first choice for many people to keep warm in winter. Its excellent cold-proof performance comes from the special structure of down.

★ When choosing a down jacket, you don’t have to just pursue cold-proof performance, just choose one that is suitable for local conditions.

Winter is coming, and various types of winter clothes such as cotton coats, wool coats, down jackets, etc. are the protagonists who help us fight the cold. Keeping warm is one of the most basic functions of clothing, so what is the principle of keeping warm in winter clothes? Many friends may blurt out - "thick enough", which is basically correct, but not comprehensive enough. Let's talk about it in detail.

01

Why can winter clothes keep you warm?

Generally speaking, the three factors of temperature, humidity and wind speed in the external environment directly affect the human body's perception of cold and warmth, among which the influence of temperature is the most obvious. In a cold environment, there is a temperature difference between the human body temperature (generally constant at 36-37 degrees) and the ambient temperature, and heat is transferred from the high temperature human body to the low temperature environment; the colder the outside world, the greater the temperature difference, and the easier it is for people to lose heat and feel cold.

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When the human body wears clothes, most of the heat is transferred by heat conduction between the fibers of the clothes and between the fibers and the air. Some of the heat is transferred by air convection between the clothes and the human body and between clothes. Some of the heat is transferred by radiation between the fibers.

The function of winter clothing is to form a "barrier" on the surface of the human body, preventing or slowing down the loss of body heat to the environment. On the one hand, the thermal conductivity of the winter clothing fiber material itself directly determines the warmth retention performance of the clothing. More importantly, the still air "locked" by the winter clothing plays a greater role in the warmth retention effect.

Dry still air is the best thermal insulator. The more still air a winter coat can lock in, the more warmth it provides. So, in theory, the thicker the same material, the warmer it is. But what if it is made of different materials?

02

Various winter warming materials

Decades ago, people mainly relied on cotton clothes to survive the winter. Cotton fibers are natural hollow fibers. The fluffy cotton fibers are filled between the fabric and lining of cotton clothes, which can "lock" a large amount of still air and provide very good warmth retention.

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However, cotton fibers have good moisture absorption but are not easy to dry. If the environment is humid, cotton fibers will become hard after absorbing moisture, and the static air in the fibers will be "squeezed" away, seriously reducing the warmth retention performance. Therefore, cotton fibers are especially not suitable for the cold and humid south. Although many clothes on the market today are called "cotton clothes", they no longer use pure cotton fibers for filling, but polyester staple fibers.

Polyester staple fiber is a chemical fiber that is widely used as a filler. It has high fluffiness and resilience, and can store a large amount of static air. There are also modified varieties such as three-dimensional curled staple fibers to improve its warmth retention. Polyester fiber is not easy to absorb moisture, and it is easy to dry and restore fluffiness even after washing in water. It is also more cost-effective than pure cotton fiber. It has replaced pure cotton fiber and is widely used in filling cotton clothes, bedding, etc.

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Wool fiber comes from sheep. It is an animal fiber with a hollow structure. The surface of the fiber is covered with tiny scales. The hollow fiber structure and the gaps between the scales on the surface are filled with air. Wool fiber is naturally curly, with a high curl density, high elasticity and high fluffiness. Fabrics woven from wool fibers can lock a thin layer of air on the surface of the fabric to achieve a good warmth-keeping effect. Wool is also used to fill bedding, which is especially suitable for sleeping and keeping warm in winter.

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Cashmere fiber comes from goats. It is a thin layer of fine wool that grows on the outer skin of goats and hides at the roots of their coarse hair. Cashmere fiber is finer than wool fiber and has a larger specific surface area. It can lock more air on the surface and feels softer. Since the output of cashmere is very small, the price of cashmere coats is also very high. However, wool coats and cashmere coats are directly sewn from woven fabrics, which have a large porosity. In cold and windy conditions, the wind will take away a lot of heat from the body surface, reducing the warmth effect.

However, when it comes to warmth, none of the materials mentioned above can compare to down.

03

Down jackets are the best choice for cold protection

Down jackets are the first choice for many people to keep warm in winter. Its excellent cold-proof performance comes from the special structure of down. Down is a mixture of "feather" and "down". Feather is feathers, and down is down.

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Different from the linear structure of fibers mentioned above, down is a three-dimensional structure in the form of a flower. Down flowers are composed of many tiny down fibers, which are hollow and contain still air.

More air can be locked between down threads and between down clusters. Down jackets are generally made of dense, windproof and waterproof fabrics, and the down is filled between the fabric and the lining. It is fluffy and resilient, making the down jacket have a high thermal resistance and achieve a good warmth-keeping effect.

Generally speaking, the larger the down cluster, the more air it can lock in, and the better the warmth retention of the down jacket. Goose down has relatively larger clusters, so goose down has a better warmth retention effect than duck down. In addition, the filling volume, down content and fluffiness are also the main indicators for measuring the quality of down jackets.

The filling volume refers to the weight of down in a down jacket. Generally speaking, the higher the filling volume, the better the warmth retention effect. The down content refers to the proportion of "down" in the down. The down content of high-quality down jackets is generally around 90%.

The fill power is the volume occupied by a certain weight of down under certain conditions. The higher the fill power, the more still air the down can lock in to keep warm with the same amount of filling, and the better the warmth retention of the down jacket.

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When choosing a down jacket, in theory, the higher the down content and the higher the fluffiness, the warmer it is, but such down jackets are often more expensive. Therefore, you don't have to blindly pursue cold resistance. It is often a more economical choice to choose a down jacket that best suits the local winter body temperature.

Author: Song Lidan, Consulting Engineer, Industrial Research Department, China Textile Construction Planning Institute

Review | Zhang Jie, Chief Engineer, China Textile Construction Planning Institute

Editor | Jiang Fan

Editor | Ding Zong

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