PVC is the abbreviation of polyvinyl chloride plastic. This kind of delightful plastic products is actually a vinyl polymer.
Simply put, the salt aqueous solution is chemically decomposed in the current action. This process produces chlorine, caustic soda and hydrogen. Refining, cracking oil or gasoline can produce ethylene. When the chlorine and ethylene mixed, it will produce dichloroethylene; dichloroethylene can be converted to produce vinyl chloride, which is the basic part of PVC. The polymerization process combines chlorinated vinyl molecules together to form a polyvinyl chloride chain. Polyvinyl chloride produced in this manner is white powder. It can not be used alone, but can be mixed with other ingredients to generate many products.
The vinyl chloride was originally synthesized in 1835 at the Justus von Liebig laboratory. While the polyvinyl chloride was synthesized by Baumann in 1872. But it was not until the 1920s that the first commercial product of polyvinyl chloride was produced in the United States and that mass production began in Europe over the next 20 years.
Polyvinyl chloride has become the world's second largest general resin after polyethylene resin, which is rich in raw materials (petroleum, limestone, coke, salt and natural gas), mature manufacturing process, low price and wide use. Accounting for 29% of the world's total consumption of synthetic resin. PVC is easy to process, can be molded, laminated, injection molding, extrusion, calendering, blow molding hollow, etc. processing. PVC is mainly used for the production of artificial leather, film, wire sheath and other plastic soft products, but also the production of sheet metal, doors and windows, pipes and valves and other plastic hard products.
Polyvinyl chloride has a flame retardant (flame retardant value of 40 or more), high chemical resistance (resistant to hydrochloric acid, 90% concentration of sulfuric acid, the concentration of 60% nitric acid and 20% concentration of sodium hydroxide), mechanical Strength and electrical insulation of the advantages of good. But the heat resistance is poor, the softening point is 80 ℃, at 130 ℃ began to decompose discoloration, and precipitation of HCI.
In fact, the narrative so much, we should most understand is: to provide a lot of convenience to the human, PVC has its most deadly shortcomings; it is the most destructive plastic products. PVC production, use and treatment process will lead to the release of toxic chlorides. These toxins will be very easy to enter the water, air and food chain, and then cause great damage to the environment. And PVC is said to be indirectly associated with cancer, hormonal imbalance, birth defects, diabetes, nerve damage and immunosuppressive consequences. In PVC toys, phthalates are used as softeners, and health conscious parents have begun to worry about whether the substance is harmful to their children: because children will chew and suck their toys if these additives How to do poisonous?
In fact, the role of chlorine in the PVC is also let people love and hate, the original most of the daily plastic products is carbon and hydrogen as the main component of the elements of. PVC is different in that it contains chlorine (about 57% by weight) in addition to carbon and hydrogen. The use of chlorine in the molecule makes the role of PVC particularly rich, because it can make PVC and many other substances compatible. The composition of chlorine also helps to delay the burning of PVC, and it can also be used as a "mark" for polyvinyl chloride in the automatic classification system for plastic recycling. We can also use a variety of technologies to develop PVC manufacturing methods, almost do not use energy can be made into the final product form. Therefore, the presence of chlorine is so that the PVC has such a fast and broad application areas.
But at the same time, we can not forget: chlorine is also known as "PVC fatal structural unit." It is the main pollutant pollution of the environment. In fact, it is also an essential component of many notorious toxic substances such as CFC (CFC), dioxin pollution, PCB (polychlorinated biphenyls) and DDT pesticides. A large amount of chlorinated toxins invade air, water and food chains. Most of these chemicals - organochlorine - are not easily decomposed, will remain in the environment for decades, humans and animals can not effectively exclude it from the body ... ... so that the danger of such an ambush down.
PVC production in the 20th century, 60 years has been rapid development. As other products that use industrial chlorine are banned (such as polychlorinated biphenyls (PCBs), chlorofluorocarbons (CFCs) and chlorine-containing solvents, etc.), the chlorine industry turns to PVC to consume its additional chlorine. PVC production is increasing, especially in Asia and Latin America. Now more than 30% of the world's chlorine products are used to produce PVC.