Is "Ice Silk" bedding a "tax on IQ"? How should bedding be selected?

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"Ice silk fabric is a tax on IQ?"

Some netizens believe that "Ice Silk" is an exaggerated propaganda, a waste of money, and will not bring cool things down.

Rumor Analysis

This statement is debatable.

At present, there is no relevant national standard or textile industry standard to clearly define the concept of "ice silk". "Ice silk" is just a name used for marketing. And "ice silk" products themselves can indeed bring some coolness, but it is not so long-lasting.

In the hot summer, how to choose the right bedding to improve the comfort of sleep has become the focus of many consumers. Comfortable bedding can not only help us fall asleep better, but also improve the overall quality of sleep. There are many products in this direction on the market, such as "Ice Silk", etc. So is this so-called "Ice Silk" really effective or just a waste of money? How should we choose bedding? Let's start with the characteristics of human body heat dissipation.

How do we stay cool?

The most prominent environmental feature in summer is the high temperature, which is often accompanied by high humidity. When the outside temperature is higher than the human body temperature (36.5°C ~ 37.5°C), the human body will increase the body's heat dissipation through sweating in order to maintain a constant body temperature. The evaporation of sweat can take away some of the body's heat. In the case of high humidity, the moisture content in the air is very high, and the evaporation efficiency of sweat will be affected. The body will increase the amount of sweating to increase heat dissipation, and sweating will be more obvious.

A full night of sleep usually lasts 6-8 hours, during which the temperature will change. Summer bedding should help the human body to do a good job of "heat and humidity management" during this period, mainly to help the human body dissipate heat and absorb moisture and sweat. There are three ways to transfer heat: heat conduction, heat convection and heat radiation. When bedding is in direct contact with the human body, or even "close contact" (for example, when a person lies on the sheets), heat transfer mainly occurs through heat conduction. At this time, we need to pay attention to the thermal conductivity of bedding.

Thermal conductivity is an important indicator to measure the thermal conductivity of materials. The larger the thermal conductivity, the more efficient the material is in conducting heat, and the cooler the human body will feel. The thermal conductivity of common textile materials is generally between 0.042 and 0.337 W/(m·K), among which nylon (also known as nylon) has the highest thermal conductivity, which can reach 0.244 to 0.337 W/(m·K), and is used in many products that provide cooling functions. In addition to thermal conductivity, the smoother the surface of the fabric structure, the larger the contact area with the skin, and the higher the efficiency of its heat conduction. Knowing this, and looking back at the various types of fabrics, we will have a clearer mind when choosing.

Is “Ice Silk” a tax on your IQ?

Many businesses are vigorously launching new concepts in the summer - is the "ice silk" bedding a waste of money?

This can be divided into two aspects. First of all, it should be made clear that there is no relevant national standard or textile industry standard to clearly define the concept of "ice silk". "Ice silk" is just a name used for marketing. And "ice silk" products themselves can indeed bring some coolness, but it is not so long-lasting. Next, let's talk about it in detail, hoping to help you make a choice.

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At present, ice silk bedding on the market is mainly woven with chemical synthetic fibers polyester or nylon, or woven with these two fibers and regenerated cellulose fibers by blending, interweaving, etc. Merchants promote the "cool feeling" feature of "ice silk bedding", and here we must introduce a professional term for textiles - instant cool feeling when touching.

The national standard GB/T 35263-2017 "Testing and Evaluation of the Instantaneous Cooling Properties of Textiles upon Contact" defines "instantaneous cooling upon contact" as "the moment when the skin comes into contact with a fabric that is lower than its temperature, causing rapid loss of heat from the skin surface and an instant drop in temperature, which is then fed back to the brain through the temperature-sensitive nerve endings in the skin to form a cool feeling", and uses the "contact cooling coefficient qmax" to quantitatively evaluate the coolness of the fabric.

When qmax≥0.15J/(cm2·s), the textile can be considered to have instantaneous cool feeling upon contact. Among commonly used textile fibers, nylon and polyester have relatively high thermal conductivity, which can quickly take away the heat from the skin surface when in contact with the human body, giving people a more obvious cool feeling.

In addition, during the manufacturing process of synthetic fibers, a small amount of nano-powder of minerals such as jade or mica is added to the fibers. The good thermal conductivity and slow heat absorption of these minerals can further enhance the cooling function of the fibers. However, this instantaneous cooling sensation often does not last. You may need to turn over and lie on the sheets next to you to feel the "coolness" again after lying down for a long time.

When consumers choose this type of ice silk bedding, they should give priority to products that meet the above national standards and check whether the product is clearly marked with "contact cooling coefficient qmax ≥ 0.15 J/(cm2·s)". It is best if this value can reach 0.2 or above.

In addition, it is very important to pay attention to the moisture absorption and breathability of the product. It is recommended to give priority to products woven from synthetic fibers and regenerated cellulose fibers (such as viscose fibers and lyocell fibers), because pure polyester or pure nylon fabrics have weaker moisture absorption and breathability. The addition of regenerated cellulose fibers can improve the moisture absorption and breathability of the product.

Ultra-high molecular weight polyethylene fiber (UHMWPE) has particularly excellent thermal conductivity, with a thermal conductivity coefficient of up to 0.3-0.5W/(m·K), which is significantly higher than that of common textile fibers. At present, ultra-high molecular weight polyethylene fiber has been used in cooling bedding, blended and interwoven with other textile fibers, and developed high-quality bedding that is both cooling and moisture-absorbent and breathable.

Table 1 Common moisture regain of common textile fibers

Note: The official moisture regain is an important indicator to measure the hygroscopicity of fiber materials. The higher the moisture regain, the better the hygroscopicity.

Now that we know about ice silk, let’s take a look at traditional bedding fabrics.

Bamboo mat

When it comes to the cool feeling of summer bedding, many people will think of bamboo mats, especially the popular mahjong mats. The processed bamboo pieces are woven together with ropes and threads, and people feel very cool when lying on the bamboo mat. This is because the thermal conductivity of bamboo is much better than that of textile fibers. The thermal conductivity coefficient of bamboo, the main material for making mats, is 0.3~0.5W/(m·K).

At the same time, the structure of the ropes and threads creates gaps between the bamboo blocks, which is conducive to increasing air circulation and improving air convection in a small area to increase heat dissipation. However, not everyone can "bear" the strong cool feeling of the mat, and the bamboo mat is relatively hard. Often when you wake up, there will be indentations of the bamboo mat on your face and body. At the same time, because bamboo contains a certain proportion of lignin, it has natural hydrophobicity, resulting in poor moisture absorption and poor comfort. Perhaps because of these reasons, mahjong mats seem to be getting farther and farther away from us in recent years.

Cotton bedding

Cotton bedding is still the most common type of bedding. Although the thermal conductivity of cotton fiber is not outstanding, its moisture absorption is very good. Cotton fiber is composed of cellulose, and the cellulose molecular chain contains a large number of hydroxyl (-OH) hydrophilic groups. These hydroxyl groups can form hydrogen bonds with water molecules, thereby attracting and retaining moisture, allowing cotton fibers to absorb and retain a considerable amount of moisture, and can quickly absorb sweat on the skin surface to keep the skin dry.

When using cotton bedding in summer, you can choose cotton bedding with a higher yarn count (40 or above in British standard) and a smooth feel. Air is a poor conductor of heat (thermal conductivity is only about 0.026W/(m·K)). Fabrics woven with high-count yarns can be relatively tight, and the air content between the gaps in the fabrics is less, which is conducive to heat dissipation when in contact with the skin. However, in the southern part of my country, during the continuous rainy days in summer, the humidity in the air is high, and cotton bedding will also absorb moisture from the environment, making people feel damp, wrinkled, and not dry enough, but it will be better in the dry northern regions.

"Old coarse cloth" bedding

"Old coarse cloth" bedding has gradually become popular in summer in recent years. Traditional old coarse cloth is a pure cotton fabric woven by hand on an old loom. The old coarse cloth bedding sold on the market now is generally woven on a high-efficiency automatic loom using a "double-stranded weaving" process with coarser yarns. There is a lot of air between the fibers and yarns of the old coarse cloth fabric, which increases air convection heat dissipation.

Hemp fiber bedding

Hemp fiber is particularly suitable for use in summer. It has a natural central cavity structure and many cracks and holes on the longitudinal surface of the fiber. This structure is conducive to the absorption and discharge of sweat on the skin surface.

At the same time, hemp fiber contains a variety of natural antibacterial ingredients, which have an "innate" antibacterial effect and are particularly suitable for use in summer. However, since hemp fiber is extracted from the bast tissue of the stem of the hemp plant, it is not as skin-friendly as cotton fiber. Consumers can also choose cotton and linen blended bedding, which has the moisture absorption and antibacterial properties of hemp, and the softness and comfort of cotton.

Silk bedding

Silk is a natural protein fiber, mainly composed of fibroin and sericin. These proteins are similar to the protein structure in human skin, so they are more compatible with the skin. Silk fiber has excellent hygroscopicity, and the surface of the woven fabric is smooth, which can provide a more obvious cool touch feeling. However, the price of silk bedding is usually high, and daily cleaning and care also require special attention, avoiding strong rubbing, high-temperature ironing and direct sunlight exposure to avoid damaging the fiber structure.

Regenerated cellulose fiber bedding

The main chemical component of regenerated cellulose fiber (common ones include viscose fiber, lyocell fiber, bamboo pulp fiber, etc.) is also cellulose, which has better moisture absorption than cotton fiber. The bedding woven with it has a smooth surface and a more prominent cool feeling. The price is reasonable, and it is also very suitable for the public's summer bedding.

In addition to paying attention to the breathability, moisture absorption, and coolness of the material when choosing summer bedding, some color choices can also bring a certain sense of freshness. It is recommended to choose light tones for summer bedding, such as white, light blue, light gray, etc. These colors not only give people a cool feeling visually, but also have lower heat absorption than dark colors, which helps to keep the surface of the bedding cool.

When purchasing bedding, consumers should choose regular sales channels, focus on checking the material and product standards marked on the product label or washing label, and choose bedding that complies with the national standard GB18401-2010 "National Basic Safety Technical Specifications for Textile Products". Bedding used by infants must meet Class A safety technical requirements. In terms of bedding cleaning, since it is easy to sweat in summer, it is recommended to increase the frequency of replacement and cleaning of bedding to keep it clean, dry and hygienic. The use of home air conditioners has become very common. Under the suitable ambient temperature and humidity created by air conditioners, the choice of summer bedding is also more flexible. I believe that these rich bedding can help you spend every summer night comfortably.

Looking in the mirror of rumors

It is true that some manufacturers are now fabricating concepts to confuse consumers, but we still need to distinguish such situations from normal advertising and marketing, and we don’t need to think that everything is a “tax on IQ”.

Author: Song Lidan, Senior Engineer, China Textile Construction Planning Institute

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