Its full name is Polyvinylchloride, and its main component is polyvinyl chloride, which is bright in color, corrosion resistant, firm and durable. Because some toxic auxiliary materials such as plasticizer and anti-aging agent are added in the manufacturing process to enhance its heat resistance, toughness, ductility, etc., its products generally do not store food and drugs. It is a widely loved, popular, and widely used synthetic material in the world today. Its global usage ranks second among various synthetic materials. PVC (polyvinyl chloride), with its monomer structure simplified as CH2=CHCl, is a plastic substance commonly used in pipe materials.

Polyvinyl chloride is a polymer material that uses a chlorine atom to replace a hydrogen atom in polyethylene. A thermoplastic resin formed by the polymerization of vinyl chloride under the action of an initiator is a homopolymer of vinyl chloride. Polyvinyl chloride is one of the largest plastic products in the world in terms of production, price, and wide application. Polychloroethylene resin is a white or light yellow powder. PVC is a homopolymer of vinyl chloride, a thermoplastic resin formed by the polymerization of vinyl chloride under the action of an initiator; It is a polymer material that uses a chlorine atom to replace a hydrogen atom in polyethylene.

The natural color of polyvinyl chloride is slightly yellow and translucent, with a glossy appearance. Transparency is better than polyethylene and polypropylene, but worse than polystyrene. Depending on the amount of additives used, it can be divided into soft and hard polyvinyl chloride. Soft products are soft and tough, with a sticky feel. Hard products have a higher hardness than low-density polyethylene, but lower hardness than polypropylene, and may exhibit whitening at the bends. Common products: boards, pipes, soles, toys, doors and windows, wire skins, stationery, etc

Chemical and Physical Properties:

Rigid PVC is one of the most widely used plastic materials. PVC is actually a vinyl based polymer, and its material is an amorphous material. It has non flammability, high strength, weather resistance, and excellent geometric stability. PVC has strong resistance to oxidants, reducing agents, and strong acids. However, it can be corroded by concentrated oxidizing acids, such as concentrated sulfuric acid and concentrated nitric acid, and is not suitable for contact with Aromatic hydrocarbon and chlorinated hydrocarbons. PVC can be divided into soft PVC and hard PVC. Hard PVC accounts for approximately two-thirds of the market, while soft PVC accounts for one-third.

Simply put, the aqueous solution of salt undergoes chemical decomposition under the action of electric current. This process produces chlorine, caustic soda, and hydrogen gas. Refining and cracking petroleum or gasoline can produce ethylene. When chlorine and ethylene are mixed, dichloroethylene is produced; Dichloroethylene can also be converted into vinyl chloride, which is a fundamental component of polyvinyl chloride. The polymerization process connects vinyl chloride molecules together to form a polyvinyl chloride chain. The polyvinyl chloride generated in this way appears as a white powder. It cannot be used alone, but can be mixed with other ingredients to produce many products.

Vinyl chloride was initially synthesized in the laboratory of Justus von Liebug in 1835. PVC was synthesized by Baumann in 1872. PVC has the advantages of flame retardant (flame retardant value is above 40), high chemical resistance (resistance to concentrated hydrochloric acid, 90% sulfuric acid, 60% nitric acid and 20% sodium hydroxide), good mechanical strength and electrical insulation. But its heat resistance is poor, with a softening point of 80 ℃. It begins to decompose and discolor at 130 ℃, and HCI is precipitated.

There are two main preparation processes for PVC production. The first is the ethylene method, with petroleum as the main raw material; The second type is the calcium carbide method, which mainly produces raw materials such as calcium carbide, coal, and raw salt. The production of PVC in the international market is mainly based on the ethylene method, while in China, due to the resource endowment of rich coal, poor oil, and limited gas, the calcium carbide method is usually the main method. As of December 2007, the calcium carbide method accounted for over 70% of China's total PVC production capacity.

Due to the fact that in the preparation of PVC by the calcium carbide method, hydrogen chloride is used to produce PVC after electrolysis of the raw salt, and the remaining sodium is used to produce caustic soda, there is actually a symbiotic relationship between chlorine and alkali, and the chlorine alkali balance is also an important factor that must be considered in the entire industry development process.

From the perspective of production costs, there is a significant cost difference between the two processes in different economic development cycles. Usually, in the stage of rapid international macroeconomic development, due to high oil prices, the production cost of ethylene method is higher, and the cost advantage of calcium carbide method is obvious; Once the international economy enters a recession, oil prices will operate at a low level, and the cost advantage of the carbide method will disappear due to its high energy consumption and supported prices for coal, electricity, and oil transportation. Since 2003, the significant increase in international oil prices has led to an increase in the cost of ethylene based PVC production, while the production of calcium carbide has been less affected by this, leading to a new wave of construction of domestic calcium carbide based PVC production equipment. This has led to a sharp expansion of the production capacity of calcium carbide based PVC, posing a great challenge to the production of ethylene based PVC, and many ethylene based enterprises are on the brink of losses. But with the continuous decline in crude oil prices after May 2008, the cost advantage of ethylene method is obvious, and carbide method manufacturers are operating at a low profit, which may even be difficult to sustain.

The cost composition of calcium carbide method mainly consists of calcium carbide expenses, hydrogen chloride expenses, and water and electricity expenses. According to national standards, the production of 1 ton of PVC consumes 1.45-1.5 tons of calcium carbide (usually calculated as 1.45, but the actual consumption in the production process is generally higher than this proportion, and only a few can meet the standard), consumes 0.75-0.85 tons of hydrogen chloride gas (usually calculated as 0.76), and consumes approximately 450-500kw of electricity per ton? h. Other project expenses, such as packaging fees, initiators, dispersants, water fees, and management personnel fees, vary depending on the manufacturer and production scale. Overall, the cost distribution ratio of the carbide method is approximately 65-70% for carbide, 15% for hydrogen chloride, 6% for electricity, and 6% for other manufacturing expenses. A significant feature of the calcium carbide method is its high power consumption, which not only consumes electricity in the production of PVC, but also consumes a large amount of electricity in the preparation of calcium carbide from coke. For example, producing 1 ton of calcium carbide requires approximately 3450 kW of electricity? H of electricity, 0.6 tons of coke, and 0.9 tons of limestone.

The main factors affecting the cost of ethylene production include ethylene consumption, processing aids, electricity consumption, chlorine consumption, and management labor costs. The ethylene method consumes 0.5 tons of ethylene and 0.65 tons of chlorine gas for each ton of PVC produced, accounting for approximately 60% of the cost. Therefore, the price of ethylene has a significant impact on the cost of polyvinyl chloride. Although the ethylene method consumes less energy than the calcium carbide method, its equipment investment is huge, so equipment depreciation accounts for a large proportion of the cost. The equipment investment is fixed, so the changes in the prices of vinyl chloride and ethylene are the main factors affecting the price changes of polyvinyl chloride resin.