PVC is the English abbreviation for polyvinyl chloride plastic. This kind of plastic product that makes people happy is actually a vinyl polymer.
Simply put, the aqueous solution of the salt is chemically decomposed by the action of electricity. This process produces chlorine, caustic soda and hydrogen. Refined, cracked petroleum or gasoline can produce ethylene. When chlorine and ethylene are mixed, dichloroethylene is produced; and dichloroethylene can be converted to produce a vinyl chloride, which is an essential component of polyvinyl chloride. The polymerization process joins the chlorinated vinyl molecules together to form a polyvinyl chloride chain. The polyvinyl chloride produced in this manner was in the form of a white powder. It cannot be used alone, but can be mixed with other ingredients to produce many products.
Vinyl chloride was originally synthesized in the Justus von Liebig laboratory in 1835. Polyvinyl chloride was synthesized by Baumann in 1872. However, it was not until the 1920s that the first commercial products of polyvinyl chloride were produced in the United States, and in the next 20 years, large-scale production began in Europe.
Polyvinyl chloride has the outstanding characteristics of rich raw materials (oil, limestone, coke, salt and natural gas), mature manufacturing process, low price and wide application. It has become the second largest general-purpose resin in the world after polyethylene resin. It accounts for 29% of the world's total synthetic resin consumption. Polyvinyl chloride is easy to process and can be processed by molding, laminating, injection molding, extrusion molding, calendering, and blow molding. Polyvinyl chloride is mainly used for the production of plastic soft products such as artificial leather, film, wire sheath, etc. It can also produce plastic hard products such as plates, doors and windows, pipes and valves.
Polyvinyl chloride is flame retardant (flame retardant value is 40 or higher), high chemical resistance (concentrated hydrochloric acid, 90% sulfuric acid, 60% nitric acid and 20% sodium hydroxide), machinery Good strength and electrical insulation. However, the heat resistance was poor, the softening point was 80 ° C, and the discoloration began to decompose at 130 ° C, and HCI was precipitated.
In fact, narrating so much, we should know the most: after providing many conveniences to humans, PVC has its most deadly shortcomings; it is the most destructive plastic products for the environment. The production, use and handling of PVC can lead to the release of toxic chlorides. These toxins can easily enter the water, air and food chains, causing great damage to the environment. It is also said that PVC is indirectly related to 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 chew and suck their toys, if these additives What about poison?
Why is polyvinyl chloride loved and hated by people like this? In fact, the role of chlorine in PVC is also to make people love and hate. Most of the daily plastic products are mainly composed of carbon and hydrogen. of. Polyvinyl chloride differs in that it contains chlorine in addition to carbon and hydrogen (about 57% by weight). Due to the presence of chlorine in the molecule, the role of polyvinyl chloride is particularly rich because it allows polyvinyl chloride to be compatible with many other substances. The chlorine component also helps to delay the burning of PVC, and it can be used as a "marker" for distinguishing polyvinyl chloride in an automated sorting system for plastics recycling. We can also use a variety of techniques to develop PVC manufacturing methods, and almost no energy can be used to make the final product form. Therefore, it is the presence of chlorine that makes polyvinyl chloride such a fast and broad application.
But, at the same time, we must not forget: chlorine is also known as "a deadly structural unit in PVC." It is the main criminal of PVC pollution. In fact it is also a fundamental component of many notorious toxic substances such as CFC (CFC), dioxin contamination, PCB (polychlorinated biphenyls) and DDT pesticides. A large amount of chlorinated toxins invade the air, water stream and food chain. Most of these chemicals, organochlorine, are not easily decomposed and will remain in the environment for decades. Humans and animals cannot effectively exclude it from the body... so that the danger is ambushed.
The production of PVC was rapidly developed in the 1960s. As other products using industrial chlorine are banned (such as polychlorinated biphenyls (PCBs), chlorofluorocarbons (CFCs) and chlorine-containing solvents, etc.), the chlorine industry is turning to PVC to consume its extra chlorine. The production of PVC is gradually increasing, especially in Asia and Latin America. More than 30% of the world's chlorine products are now used to produce PVC.