First aid blankets are generally made of tin foil or aluminum film, divided into double-sided gold, double-sided silver and gold and silver two-sided three, with warmth, cold and sun protection.
First aid blankets are mainly used in cold places, the purpose is to prevent hypothermia and death from human hypothermia, so it is common in the emergency of climbing snow-capped mountains, after being rescued after falling into the water, the first aid blanket is used to include the body. Seeing this, some people will ask, just said that it is a layer of composite film, how can it keep warm? Next, let's look at the principle of keeping warm.
There are two main ways to keep warm, one way is to add a home insulation layer, the thermal layer is generally some fluffy substances, the use of fluffy air mixed in the surface of the object to form a layer of non-flowing air. The air itself is a poor conductor of heat, so it can play a certain role in keeping warm, and general down, cotton, etc. are used in this way to keep warm. The second way is heat-reflective warmth. Highly reflective materials are used to reflect the thermal radiation back. We all know that white clothes are cooler than black clothes because white reflects more strongly than black and can reflect sunlight back. The first aid blanket uses a combination of these two principles. One of the functions of the aluminum film in the aluminum plastic film is to ensure that a layer of air on the surface of the human body is stable and does not flow, and its main role is that aluminum is a highly reflective material, which can reflect back the heat radiation emitted by the human body, and its heat reflection efficiency is as high as 90%. This effectively reduces the speed of heat dissipation by the human body. Because aluminum belongs to metal, it is easier to tear and the strength is not high. Therefore, the main purpose of composite plastic film is to increase the toughness and strength of the first aid blanket.