刘伯温致力打造火热全网_性感美女毛片_日韩在线小视频_中文字幕久久欲求不满

With the rapid development of the national economy and the progress of people' s living standards, plastics have been integrated into every bit of life, ranging from household appliances and daily necessities to automobiles and aviation, and general plastics and engineering plastics are widely used.

When it comes to general plastics, let' s talk about the fresh-keeping film that is used almost every day, especially for things placed in the refrigerator. People are used to wrapping things with fresh-keeping film before putting them in, just to keep things from losing nutrition and make them tasteless in the refrigerator; But we all just know that the plastic wrap belongs to plastic, but we don' t know what kind of plastic it is made of. Engineering plastics online: in fact, most of the plastic wrap is made of PE (polyethylene) and PVC (polyvinyl chloride), one of the general plastic types. It is understood that in terms of function and technology, PVC fresh-keeping films with different functions are toxic (a variety of PVC fresh-keeping films are toxic), and CCTV has also exposed them. But how to identify whether PVC fresh-keeping film is toxic or non-toxic? Most people really don' t know. Today, engineering plastics online teaches you three ways to identify: touch, burn and see.

The first method: touch with your hand, take out a roll of PE fresh-keeping film, rub it with your hand, the stickiness is poor, it is easy to open, and it will not stick to the food when wrapping the food, so you can use it safely; The PVC fresh-keeping film has good viscosity. It is not easy to unfold after being rubbed by hand. It will not only stick to the food, but also break easily when it is placed.

The second method: fire, take a little PE fresh-keeping film and light it. If the flame is yellow after burning, it will not go out if it is separated from the fire source. The fresh-keeping film drops down like wax oil and emits a candle smell, which is a non-toxic polyethylene film. The PVC fresh-keeping film is not easy to ignite, and will be extinguished after being separated from the fire source. After burning, there is an unpleasant and irritating smell, which will damage people' s health.

The third method: seeing, seeing is the simplest and most direct of the three methods; When you buy fresh-keeping film in the mall, you can pay attention to the product description on the outer package of the fresh-keeping film. If it is marked with "PE" or clearly marked with polyethylene, you can use it with confidence; Because the Chinese name of PE is polyethylene, it is a general engineering plastic thermoplastic resin, non-toxic. But if the word "PVC" is written, or the PVC material is written, or there is no mark.

Source: Jiangmen engineering plastics http://www.latexbbs.com/