To tell a bad joke, it is not recommended to wear snow boots on a snowy day. There are cave shoes in the summer and snow boots in the winter. Under the siege of heavy snow, snow boots represented by UGG exploded in popularity with their thick and warm effect visible to the naked eye. But many netizens put on UGG snow boots on a snowy day, but they almost cried because of these shoes, "I split a fork when I went out", "my feet slipped 20 times on a 2-kilometer road", "I became tie-dye when I came back", ......Not slippery or waterproof, good snow boots have become "snow assassins"?Snow boots that are not waterproofUGG snow boots are not waterproof, mainly because their fabric (leather) is not waterproof, and the merchant has not done waterproof treatment on them. In **"UGG official***, the top selling snow boots are mainly made of cow cut leather or shearle. This is a type of leather. Leather is the product of animal skin processed by physical, chemical and biological methods, and the common material names on the leather product certificate are the first layer of leather and the cut leather. The first layer of leather is cowhide and sheepskin, but in order to improve the utilization rate of thicker natural leather, they will be cut into two or more layers during the tanning process.
two, three layers or other leather. Whereas, genuine leather does not have the effect of being completely waterproof. This is not only because the side chains of collagen fibers in its microstructure have hydrophilic groups such as amino groups, carboxyl groups, and hydroxyl groups, but also because many hydrophilic substances such as surfactants and inorganic salts are added to the leather during the tanning process. 
Source: **ugg official*** Product detail page To make leather waterproof, the mainstream ideas are as follows: seal the hydrophilic groups on the collagen fiber side chain and remove the internal hydrophilic substances;Substances with hydrophobic properties are added to the interior of the leather or the finishing layer through the leather production process such as retanning, grease, and finishing, and the waterproof performance of the leather is improved. So why aren't UGG's snow boots universally waterproof?Because of the cost. Affordable snow boots are made of artificial leather or synthetic leather, which is simple to operate, low cost, and easy to mass-produce, but has relatively poor thermal performance. Snow boots such as UGG that use genuine leather need to be coated with adhesive film for waterproofing, which is complex and costly. But a pair of ugg is about 1,000 yuan, can't you upgrade the waterproof after making money?The answer is yes, but not necessarily. UGG's brand positioning is "an international high-end lifestyle brand". As a luxury item in snow boots, it pays more attention to the symbolic meaning of the product than to the functionality, and will deliberately weaken the practical function to maintain a high-end pricing strategy. And UGG does not indicate in a conspicuous position that their shoes are not waterproof, many consumers may take it for granted that snow boots must be waterproof, right?As a result, after buying it, I found out that this was not the case. Friction rubbing, how it is not slipperySnow boots are not slippery, one reason is that the ice surface after the snow is more slippery than we think, and the other reason is that the soles of UGG snow boots are "not up to standard". Some netizens ridiculed that the icy road surface can be called the road to death, and flies have to slip when they fall on it. As for why the ice surface is so slippery, some scholars believe that the pressure melts the ice and causes the ice surface to produce waterSome scholars believe that friction generates heat, and the melting of the ice surface produces water;There is also a theory that there is already a layer of water molecules on the ice. In 1987, scientists discovered the existence of a layer of water molecules about 100 nanometers thick on the ice surface through X-ray imaging. 2017, Huib JBakker's group used sum-frequency spectroscopy to observe the existence of a layer of "quasi-liquid" on the ice surface. 
Schematic diagram of the liquid water layer on the ice surface|**Ref. [9]Don't underestimate this layer of water on the ice, it can reduce the coefficient of sliding friction on the ice surface. Under normal circumstances, when people walk on the road, the friction force is about equal to mg, and the weight of the individual is unchanged, which affects the friction of different road conditions. It is affected by road conditions (such as ice or dry ground), and also by the material and pattern of the sole. As far as the pattern is concerned, the sole of the same material, the pattern is distributed in the forefoot force part and the heel force part and is oblique design, which is relatively non-slip, and the several UGG snow boots shown in front are sun patterns, which are generally in line with the design of "anti-slip patterns". 
The sole pattern of a certain snow boot of ugg|Source: **The focus of the screenshot is still the sole material. UGG snow boots are mostly made of EVA material. EVA stands for ethylene vinyl acetate copolymer, and studies have found that although EVA is lightweight, its anti-slip performance is more general. According to the test results of different sole materials in the wet state of the wooden floor, the anti-slip performance of different sole materials is: TPR > rubber > EVA two materials " MD > polyurethane. For snow boots, according to the QB T 4556-2013 product standard, the requirements for the wet static friction coefficient of snow boots should not be less than 03。Research by Underwriters Laboratories and the American Society for Materials and Testing ASTM found that when the coefficient of friction is 0At 4 o'clock, people are in a dangerous state during walking. In experiments with EVA, it was 0The ratio of 4 is also only 833%, let alone on slippery ice. 
Indicators of anti-slip performance in technical specifications of domestic and foreign footwear product standardsSource: References[4] All in all, shoes without non-slip soles are certainly not non-slip. If you really want to wear fluffy but non-slip snow boots, smart netizens gave us the answer again: snow boots are equipped with "serrated teeth", and you can't fall a little. 
Source: Screenshot of XiaohongshuIt's not slippery or waterproof, why are snow boots called?UGG may not really be called snow boots. ugg originally means ugly boots. Regarding the origin of Ugly Boots, some say that it originated in Australia during World War I, when Australian pilots used two pieces of sheepskin wrapped into shoes to keep out the cold. It is also said that it was born on the beaches of Australia. In Perth, Australia's surfing destination, people feel very cold when they come ashore, so they use sheepskin boots to keep warm. So the original "UGG" was not a brand, but a general term for a class of shoes, just like we say "high heels" and "flip-flops". What we now know as UGG Australia is actually an American brand, dating back to the 70s of the last century. In 1978, Australian surfer Smith, who lived in California, founded UGG Australia. In 1995, Smith sold the UGG Australia brand to the American company Deckers. There are also many UGG brands in Australia, such as Shearers UGG and Jumbo UGG. The origin of "UGG" has also led to a disagreement between Australian manufacturers and Deckers over the use of trademarks. DECKERS has registered the UG trademark in more than 100 countries around the world, preventing other brands with the word "UGG" from entering its market. But Australian manufacturers have formed the UGG Snow Boots Association, which calls Australia the country of origin of UGG, and manufacturers have been making such boots for decades, advocating for UGG as a generic name. Australian courts have upheld the use of UGG as a generic name for goods, although in many countries, including China, such as the United States, the Netherlands and Turkey, have rejected claims that "UGG" is a generic name for goods. But then again, whether UGG is a generic name or a specific brand, and whether it was born because of pilots or beaches, there is no snow in the birth story of UGG, how did it become snow boots?
The title of the product comes with snow boots|Source: Screenshot of Hanguang Department Store applet People use "snow boots" to describe it, perhaps just because UGG looks fluffy and feels that it must be warm to wear in the ice and snow. In fact, the ugg is really warm to wear. There are three ways in which heat is lost to the human body: heat conduction, heat convection, and heat radiation. In 2015, Martino Colonna et al. showed that thermal convection is the main cause of heat loss in shoes in cold environments. Therefore, in order to keep the shoes warm, it is necessary to reduce the heat loss inside the shoe cavity, that is, to prevent heat conduction and seal the convection. The amount of thermal conductivity of textile materials is mainly affected by the thermal conductivity. In general, the lower the thermal conductivity, the warmer the material. But in the case of very small differences in thermal conductivity, what is more important is the amount of still air stored in the fiber layer. 
Thermal conductivity of textile materials|Source: References [10] Let's take the previous UGG shoes as an example, their inner material is mainly wool. As a naturally curly and elastic protein fiber, wool fiber has high crimping density and good fluffiness, and there are many micro-gaps between its cortical cells, between the fibrils and microfibrils and other microstructural units, which can lock the air, slow down the hot convection between the hot air between the fibers and the cold air outside, and avoid taking away the heat. 
Wool construction|Source: Reference [10] Humidity is another important factor affecting the thermal comfort of shoes. Kuklane et al.'s study showed that sweat condensation increased the internal humidity of the shoe and reduced the insulation of the footwear, which in turn made the warmth of the shoe poorer. Wool fiber has good moisture absorption, and the moisture absorption (moisture regain rate) of wool fiber is 15% to 17% under general atmospheric conditions, which is the strongest among common fibers. In other words, although "UGG" is not slippery or waterproof, it is really warm!(Forehead with a wry smile) 100 help plan