Wearing technology on your body brings both warmth and style

During the just-concluded Spring Festival holiday, affected by the cold wave, the temperature in some parts of the country dropped sharply and was in "quick-freeze" mode.

According to information from the Central Meteorological Observatory, during the holiday period, temperatures in parts of Northeast my country and North China hit a new low this winter, with the lowest temperature in Mohe City, Heilongjiang Province even falling to minus 53 degrees Celsius.

In order to keep out the cold, even many young people who "value style over temperature" put on thick coats.

However, if you want to keep warm, you don’t have to wrap yourself up like a “dumpling”. Nowadays, the “black technology” used in winter clothes can help people “have both style and warmth”.

"The loss of human body heat is caused by heat transfer, which has three basic ways of heat transfer: conduction, convection and radiation." Xia Zhaopeng, senior engineer and doctoral supervisor at the School of Textile Science and Engineering of Tianjin Polytechnic University, said in an interview with reporters that in order to achieve the thermal insulation effect, the design of winter cold-proof clothing should do everything possible to reduce the loss of heat through these three ways. Winter thermal insulation materials and thermal insulation clothing are also developed and designed around this principle.

Imitation goose down:

Retains warmth even when wet

"In winter, there is a huge temperature difference between the human body and the external low-temperature environment, which causes heat conduction, that is, heat will be conducted from a high temperature to a low temperature. If you add a high-fluff thermal filling with low thermal conductivity to the clothes, you can prevent heat conduction, thereby reducing the loss of heat from the human body and achieving the purpose of keeping warm." Xia Zhaopeng introduced that this type of thermal filling mainly plays a role in blocking heat conduction. Currently, the more common natural materials are cotton, wool, down, etc., and the more common chemical fiber materials are hollow polyester, spray-coated cotton, etc.

Compared with traditional thermal insulation filling materials, some new thermal insulation filling materials have emerged in recent years, among which the most representative one is the imitation goose down structure high thermal insulation flakes. This filling material is not only highly thermal and lightweight, but also can continue to keep warm in a humid environment. At the 2022 Beijing Winter Olympics, Chinese athletes' winter clothing will use this imitation goose down structure high thermal insulation flakes as filling materials, which can still achieve a 98% warmth retention rate when completely soaked.

The main component of the imitation goose down structure high-warmth wadding is imitation goose down with a diameter and length similar to that of goose down fibers, mixed with far-infrared polyester and hot-melt polyester. "Xia Zhaopeng explained that the imitation goose down is mainly composed of hollow polyester and Y-shaped polyester, which can store still air to the maximum extent, and still air can better preserve heat. In addition, even when soaked in water, hollow polyester and Y-shaped polyester can still store a certain amount of still air.

The highly thermal insulation wadding with imitation goose down structure can overcome the shortcomings of natural goose down such as being bulky, having odor, being easy to shed and being expensive. It is also ultra-light, ultra-thin, warm in wet state and highly fluffi. It also has good resilience after washing, does not shrink and its warmth retention rate does not decrease.

Carbon nanotube heating film:

Heats up as soon as power is turned on, temperature is adjustable

Electric heating clothing made of heating materials is one of the most studied winter clothing at home and abroad.

"Common heating materials include nickel-chromium heating wire, composite heating wire, carbon fiber heating wire, carbon nanotube heating film, etc. These materials are built into clothes to make electric heating clothes. When the electric heating clothes are connected to the charging device, the electric current passing through the heating material inside the clothes will generate heat, just like putting an electric blanket on the body." Xia Zhaopeng introduced that in addition to this, this type of clothes also has built-in sensors, which can achieve intelligent temperature control of the clothes through Bluetooth. Users only need to download an App, and they can use their mobile phones to adjust the temperature of the clothes at any time.

Among them, carbon nanotube heating film, as an important component in the temperature control and heating system, has very good application prospects. "The carbon nanotube heating film can be washed repeatedly, and can withstand bending times of more than 100,000 times. The film thickness is about tens of microns, and it has very good flexibility, and the heating efficiency is greater than 65%." Xia Zhaopeng added

In addition, relatively cheap metal wire linear heating elements, such as nickel-chromium heating wire, composite heating wire, etc., are also heating "experts".

"Metallic wire materials have high conductivity, good electrical heating performance, and have sensing, electromagnetic shielding and other properties. Take the composite heating wire as an example. Molybdenum is added to the metal wire, which not only reduces the oxidation of the metal, but also improves the durability of the metal electric heating element." Xia Zhaopeng introduced that the metal wire containing molybdenum is transformed into micron-level metal microwires through a cold stretching process, so that it is transformed from metal wire to fiber. The fiber can be blended with polyester yarn to prepare yarn, and the fabric made of it has conductivity.

Compared with ordinary conductive fabrics, this conductive fabric is more flexible and comfortable. "Its flexibility and shape are very similar to traditional fibers and yarns, and its comfort is also improved." Xia Zhaopeng said, however, this type of clothing material still has disadvantages such as not being able to withstand long-term washing and being relatively heavy.

Human body infrared reflective materials:

The human body's thermal radiation reflectivity can reach 60%

Infrared heat radiation is another form of heat loss from the human body. Traditional textiles have high infrared radiation rates and lose heat quickly. Studies have shown that cotton will inevitably radiate more than 50% of the body's heat in the form of mid-infrared. Human infrared reflective materials can reduce infrared heat radiation losses by reflecting infrared waves emitted by the human body back to the human body, thereby achieving a warming effect.

"Most human body infrared reflective materials are made of metal particles. These particles exist in the form of a microstructure. Attaching this material to the fabric forms an infrared wave reflection layer. This reflective layer can reflect back most of the infrared waves radiated by the human body, thereby achieving a thermal insulation effect." Xia Zhaopeng added.

"Human body infrared reflective materials are usually used to make the lining of winter outerwear. Generally, the human body thermal radiation reflectivity can reach 60%, which can significantly improve the cold-proof and warm-keeping effect of clothing." Xia Zhaopeng said, however, if you are in an ultra-low temperature environment for a long time, the material may not be able to achieve the ideal warming effect due to the limited heat radiated by the human body.

Polytetrafluoroethylene microporous membrane:

Breathable and waterproof in low temperature conditions

In winter, there may be rain, snow, frost and other weather outdoors. The high-density waterproof layer can block the invasion of rain, snow and frost, and avoid the reduction of the thermal insulation coefficient, the reduction of the thermal insulation efficiency or even the failure due to the inner thermal insulation material of the clothing being soaked.

"Waterproof material is a layer of polytetrafluoroethylene microporous membrane, water-based polyurethane membrane or polyurethane membrane attached to the outside of high-density fabric." Xia Zhaopeng explained that the polytetrafluoroethylene microporous membrane has more than one billion holes per square centimeter. In a low-temperature environment, the opening rate of these holes can reach 80%. The diameter of the hole is 700 times larger than the diameter of a water vapor molecule, so the sweat vapor produced by the human body can pass through it, thereby maintaining the breathability of the clothes. The diameter of the hole on the polytetrafluoroethylene microporous membrane is many times smaller than the diameter of ordinary water, so the liquid water outside cannot pass through, thus achieving the purpose of waterproofing.

Source: Science and Technology Daily, Inner Mongolia Association for Science and Technology's "Cloud Science Popularization" APP

Editor: Qiao Yuxin

Reviewer: Naren Na Zhao Lewen