The full name of PVC is Polyvinylchlorid. Its main component is polyvinyl chloride. Its color is bright, corrosion-resistant and durable. Due to the addition of some toxic and auxiliary materials such as plasticizers and antiaging agents during the manufacturing process, its heat resistance, toughness and ductility are increased, so its products generally do not store food and medicine. It is a popular and widely used synthetic material in the world. It is the second most widely used synthetic material in the world. According to statistics, in 1995 alone, the production of PVC in Europe was about 5 million tons, while its consumption was 5.3 million tons. In Germany, the average production and consumption of PVC is 1.4 million tons. PVC is being produced and applied all over the world with a growth rate of 4%. In recent years, the growth of PVC in Southeast Asia is particularly significant, which is due to the urgent need for infrastructure construction in Southeast Asian countries. PVC is the most suitable material for producing three dimensional surface film.
Chemical and physical properties:
Rigid PVC is one of the most widely used plastic materials. In fact, PVC is a vinyl polymer, its material is a non crystalline material. Stabilizers, lubricants, auxiliary processing agents, pigments, anti impact agents and other additives are often added to PVC materials in practical use. It has the characteristics of non flammability, high strength, weather resistance and excellent geometric stability. PVC has strong resistance to oxidant, reducing agent and strong acid. However, it can be corroded by concentrated oxidizing acids such as concentrated sulfuric acid and concentrated nitric acid, and is not suitable for contacting with aromatic hydrocarbons and chlorinated hydrocarbons.
Melting temperature is a very important process parameter in PVC processing. If this parameter is improper, it will lead to the problem of material decomposition. The flow characteristic of PVC is rather poor, and its process range is very narrow. In particular, the high molecular weight PVC materials are more difficult to process (this kind of materials usually need to add lubricants to improve the flow characteristics), so the low molecular weight PVC materials are usually used. The shrinkage of PVC is very low, generally 0.2 ~ 0.6%.
Process conditions of injection mold
Drying: usually no drying is required.
Melting temperature: 185 ~ 205C mold temperature: 20 ~ 50c
Injection pressure: up to 1500 bar, holding pressure: up to 1000 bar, injection speed: in order to avoid material degradation, it is generally necessary to use a considerable injection speed.
Runner and gate: all conventional gates can be used. If machining smaller parts, it is better to use needle gate or submerged gate; For thicker parts, fan gates are preferred. The minimum diameter of needle gate or submerged gate shall be 1 mm; The thickness of fan gate shall not be less than 1 mm.
Typical uses: PVC has the outstanding characteristics of rich raw materials (petroleum, limestone, coke, salt and natural gas), mature manufacturing process, low price and wide application. Now it has become the second largest general resin in the world next to polyethylene resin, accounting for 29% of the total consumption of synthetic resin in the world. PVC is easy to process. It can be processed by molding, laminating, injection molding, extrusion, calendering, blow molding, etc. PVC is mainly used in the production of artificial leather, film, wire sheath and other plastic soft products, water supply pipes, household pipes, house wallboard, commercial machine shell, electronic product packaging, medical equipment, food packaging, also can produce plastic hard products such as plates, doors and windows and valves.
PVC can be divided into soft PVC and hard PVC. Among them, hard PVC accounts for about 2 / 3 of the market, soft PVC accounts for 1 / 3. Soft PVC is generally used for floor, ceiling and leather surface, but because soft PVC contains softener (which is also the difference between soft PVC and hard PVC), it is easy to become brittle and difficult to preserve, so its application scope is limited. Rigid PVC does not contain softener, so it has good flexibility, easy molding, not brittle, non-toxic and pollution-free, long storage time, so it has great development and application value. Hereinafter referred to as PVC. The essence of PVC is a kind of vacuum plastic film, which is used for surface packaging of all kinds of panels, so it is also known as decorative film, adhesive film, and used in building materials, packaging, medicine and many other industries. Among them, the building materials industry accounts for the largest proportion, accounting for 60%, followed by the packaging industry, and a number of other small-scale application industries.
PVC is PVC plastic,
In short, the aqueous solution of salt decomposes under the action of electric current. This process produces chlorine, caustic soda and hydrogen. Ethylene can be produced by refining or cracking petroleum or gasoline. When chlorine and ethylene are mixed, dichloroethylene is produced; Vinyl chloride can be converted to vinyl chloride, which is the basic component of PVC. In the polymerization process, vinyl chloride molecules are linked together to form PVC chains. The PVC produced in this way is white powder. It can not be used alone, but can be mixed with other ingredients to produce many products.
Vinyl chloride was first synthesized in the laboratory of Justus von liebigin 1835. PVC was synthesized by Baumann in 1872. However, it was not until the 1920s that the first commercial product of PVC was produced in the United States, and it was not until the next 20 years that large-scale production began in Europe.
PVC has the advantages of flame retardant (flame retardant value is more than 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, the softening point is 80 ℃, it begins to decompose and discolor at 130 ℃, and HCI precipitates.