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PVC material is polyvinyl chloride material, referred to as PVC, which is a polymer formed by the polymerization of vinyl chloride monomer (VCM) in the presence of initiators such as peroxides and azo compounds or under the action of light and heat according to the free radical polymerization mechanism.
In 1872, the preparation process of VCM (monomer polyethylene) was first described by Baumanu. In 1916, Ostromislensky used VCM for research and successfully synthesized some polymers, which he called Cauprene Chloride. In 1926, Waldo Semon of BFGoodrich successfully synthesized polyvinyl chloride (PVC) and submitted relevant patent applications in the United States.
PVC is a white powder with an amorphous structure, with a glass transition temperature of 77~90¡æ, and begins to decompose at around 170¡æ, with poor stability to light and heat. At the same time, as a brittle solid, it has the characteristics of light weight, heat insulation, heat preservation, moisture resistance, flame retardancy, stability, good dielectric properties, durability, anti-aging, strong bending strength and impact toughness, and high elongation when broken.
PVC comes in two basic forms: rigid and flexible. Widely used in pipes, doors and windows, it can be used for soft pipes, cable insulation, imitation leather, soft signs, inflatable products, and replace rubber in many applications by adding plasticizers. PVC was included in the list of Class 3 carcinogens published by the World Health Organization's International Agency for Research on Cancer on October 27, 2017.
The history of PVC (polyvinyl chloride) can be traced back to the late 19th and early 20th centuries.
As early as 1835, Henri Victor Regnault of the United States V. Regnault discovered that a white solid was generated when vinyl chloride was exposed to sunlight, which was the earliest PVC.
In 1872, Baumanu described the preparation of VCM (monomer polyethylene), which was converted into an insoluble amorphous substance when exposed to sunlight.
In 1912, German Fritz Klatte synthesized PVC and applied for a patent in Germany, but failed to use the patent to develop commercial uses.
In 1916, Ostromislensky obtained some polymers from VCM research, which he called Cauprene Chloride. The ¦Ã type is a high molecular weight PVC that is completely unprocessable and difficult to handle.
In 1926, Waldo Semon of BFGoodrich successfully synthesized polyvinyl chloride (PVC) and submitted a related patent application in the United States. At the same time, Semon and BFGoodrich worked together to develop a technology that plasticized PVC by adding additives to make it more flexible and processable. This innovation led to the rapid widespread use of PVC in the commercial field and made it an important material. Prior to this, because the common vinyl chloride monomer (VCM) and vinyl acetate copolymer could not form a rubber-like substance, Union Carbide used a bulk prepolymerization method of liquid VCM to meet BFGoodrich's demand for PVC. This method became an early synthesis method for PVC.
In 1928, Union Carbide successfully copolymerized vinyl chloride with vinyl acetate, giving it internal plasticizing properties, which enabled it to be processed and used as lacquer and hard molded products.
Before World War II, scientist Waldo Semon conducted extensive research on plasticizing high molecular weight materials. Germany and the United Kingdom achieved industrial production of this material to replace wood and metal. In the United States, the rapid development of this material occurred during and after the war. The production of resins and plasticizers increased significantly. The industry promoted the widespread application and market expansion of these materials in the civilian market by developing new materials such as PVC.
Before the 1960s, the production method of polyvinyl chloride (PVC) mainly used acetylene and chlorine to react to produce chloroacetylene (VCM), while producing hydrogen chloride (HCl). By the late 1950s, BFG used ethylene and chlorine to crack ethylene dichloride to produce VCM and HCl, and then produced more VCM by reacting with acetylene.
In the early 1960s, as the price of calcium carbide rose, countries began to adopt the half-ethylene-half-acetylene method to produce VCM.
In the 1980s, the ethylene method basically replaced the calcium carbide method worldwide.
By the end of 2006, the calcium carbide method was the mainstream in China, and the output and capacity of PVC rose to the first place in the world.
Polyvinyl chloride is a polymer material that uses a chlorine atom to replace a hydrogen atom in polyethylene. It is an amorphous polymer with a small amount of crystalline structure. The structure of this material is as follows: -(CH2-CHCl)n-.
Rigid PVC performs well in outdoor environments and has excellent mechanical properties, rigidity, weather resistance and chemical resistance. Widely used in the fields of construction and engineering, it can be used to make pipes, window frames, floors, wall panels, etc.
Flexible PVC is soft, bendable and plastic, and is suitable for applications that require deformability. It is widely used in wire and cable insulation, extruded products (such as sealing strips, pipes), inflatable toys, etc. It is also commonly used in medical devices, such as infusion tubes, artificial blood vessels, etc.
According to the different auxiliary agents added to the PVC material, it can be divided into plasticizer PVC (Plasticized PVC) and unplasticizer PVC (Unplasticized PVC, also known as rigid PVC). Plasticizer PVC increases the softness and plasticity of the material by adding plasticizers. Plasticizers can make PVC more bendable and deformable, and increase its impact resistance. Common plasticizers include phthalates and esters. Plasticizer PVC is widely used in applications that require softness, such as plastic floors, automotive interiors, and artificial leather. Non-plasticizer PVC has no plasticizer added, so it has higher hardness and rigidity. It has excellent chemical resistance and heat resistance, and has good weather resistance in outdoor environments. Non-plasticizer PVC is often used to manufacture pipes, window frames, wire and cable sheathing and other applications that require high strength and durability.
According to the specific application field of PVC materials, it can be divided into building materials, electronic and electrical materials, medical equipment materials, packaging materials, etc. Each field has different requirements for the performance and requirements of PVC materials.
PVC (polyvinyl chloride) is a common synthetic polymer. It has excellent chemical resistance and high wear resistance. It has a wide range of applications, such as pipes, doors and windows, wall panels, wire and cable insulation and floors.
PVC materials can have different hardness according to the amount of plasticizer added to them. They can be divided into hard and soft materials. The gap between the two is large, and other properties are also quite different.
When the polyvinyl chloride (PVC) molecular chain containing chlorine is burned, it releases substances such as carbon monoxide (CO), hydrogen chloride (HCl) and benzene. This makes PVC self-extinguishing, that is, when the flame burns on the surface of PVC, the hydrogen chloride produced can prevent the spread of fire and slow down the burning speed, thereby improving fire safety. In addition, PVC shows excellent wear resistance at room temperature, which exceeds that of chlorinated rubber. This means that PVC products have good scratch and wear resistance and are not easily affected by daily wear and tear.
PVC has two major disadvantages, namely thermal instability and brittleness (poor impact resistance), which limit the development of PVC. Therefore, researchers have done a lot of work to improve these two aspects. Under the conditions of light or heat, PVC begins to soften from 80¡ãC, and the material begins to degrade when the temperature reaches above 100¡ãC. At the same time, the color of the product begins to gradually change from white to brown and finally to black, which has a great impact on the appearance of the product. The notched impact strength of hard PVC finished products is about 3~5KJ/©O. The material is very brittle. When the temperature drops, the material will quickly become hard and brittle, which seriously affects its performance. However, soft PVC products have small molecular plasticizers (such as DOP) that migrate to the surface of the material.
The synthesis process of polyvinyl chloride (PVC) resin involves dispersing liquid vinyl chloride monomer into small droplets by stirring, and then suspending it in a deionized water medium containing a dispersant. At a polymerization temperature of about 60 degrees Celsius, the initiator can decompose into active free radicals, which catalyze the polymerization reaction of the monomer. Polymerization under high temperature conditions will produce low molecular weight resins, while polymerization under low temperature conditions can produce high molecular weight resins.
The bulk polymerization of PVC resin is usually prepared using a batch method. This polymerization process can be divided into two steps: prepolymerization and postpolymerization. The first is prepolymerization. In the prepolymerization stage, a certain amount of resin monomer and initiator are added to the reaction vessel. The prepolymerization reaction is started by controlling the conversion rate within a specific range (usually between 8% and 12%) under heating and strong stirring conditions. Then the post-polymerization is carried out. The polymer "seed" generated by the prepolymerization is transferred to the polymerizer, and then the remaining VCM monomer and initiator are added. The stirring speed is relatively low to ensure uniform mixing of the reactants. When the conversion rate reaches a preset value (usually 60%-85%), the polymerization process is terminated. Next, degassing and recovery of unreacted VCM monomer are carried out.
The emulsion method is a commonly used method for producing polyvinyl chloride (PVC) resin. This method adopts intermittent operation for production and mainly includes two steps:
(1) VCM monomer is used to generate PVC latex through emulsion polymerization, that is, an emulsion of PVC primary particles suspended in water. (2) The PVC latex generated in the previous step is sprayed, dried and other steps to obtain PVC resin, which is PVC secondary particles (diameter 20~40¦Ìm) formed by the aggregation of PVC primary particles.
The solution method is a method of polymerization in solution, using an oil-soluble initiator for reaction. However, due to the presence of solvent chain transfer in the dissolution polymerization process, the resulting polymer molecular weight is low and the polymerization rate is slow. In addition, the recovery and treatment of the solvent also increase the production cost and may cause environmental pollution. Therefore, with the development of suspension and emulsion technology, the application of solution method in PVC resin production has decreased.
In general, the molecular weight of PVC is only determined by the polymerization temperature and has little to do with other conditions. When the polymerization temperature is high, the chain transfer rate is fast and the polymerization degree of the product is low; conversely, when the polymerization temperature is low, the chain transfer rate is slow and the polymerization degree of the product is high. The method of lowering the polymerization temperature can be used to obtain PVC resin with a high polymerization degree, that is, the low-temperature synthesis method.
In the suspension polymerization of vinyl chloride, in addition to adding various additives such as commonly used suspending agents and initiators, a small amount of chain extender is added, and HPVC can be produced at a polymerization temperature slightly higher than that of the low-temperature method, which is the chain extender synthesis method.
In order to overcome the disadvantage that low-temperature method high-polymerization degree PVC is difficult to process, vinyl chloride can be copolymerized with certain internal plasticizer monomers to obtain modified HPVC with good processing performance, which is the internal plasticizer monomer copolymerization synthesis method.
Compared with other products, polyvinyl chloride (PVC) has low cost, long-term stability and excellent flame retardant properties. At the same time, the mechanical properties of PVC can be adjusted by the content of plasticizer, so that it can be used to manufacture both soft materials and hard materials. Because of this, PVC is widely used in various products in the railway field. For example, PVC is used to make sheath materials for cables and wires, which can protect wires and provide insulation. PVC can also be used as a material inside and outside railway engines, such as for manufacturing parts and shells. In addition, in railway construction, PVC is also often used as a covering material to protect lines, pipes and other facilities.
PVC film is a PVC product that is formed into a thin sheet of a certain thickness by adding stabilizers, plasticizers, flame retardants, etc. to polyvinyl chloride (PVC) resin, mixing and plasticizing, and then using a tablet press. This film is usually used for plastic greenhouses and ground films. They can provide good light transmittance and heat preservation properties, help protect plants from adverse weather conditions, and promote plant growth. In addition, transparent PVC films can also be used in tablecloths, raincoats, packaging and other applications. They can effectively prevent water and dust, and have the advantages of being clean, durable and easy to maintain.
PVC coating is a common and widely used coating. It is composed of polyvinyl chloride (PVC) resin, stabilizer, plasticizer, pigment, solvent and other additives. It is a widely used car paint, mainly used for the outer bottom plate and door seal of the car body. PVC coating is inexpensive and has the ability to resist stone impact. It can provide certain protection and reduce the damage to the car body. In addition, PVC coating has good compatibility with other coatings and can be used with other paint films to provide more comprehensive protection. Although the thick coating may lead to a rough appearance, it is still an ideal choice for use in areas where the appearance quality is not required.
PVC fiber is a fiber material made by spinning polymer chemical polyvinyl chloride (PVC). Due to the rich chlorine atoms in the PVC molecular chain, PVC fiber has good flame retardant properties. In addition, its strength is close to that of cotton fiber, but its elongation at break is greater than that of cotton fiber, and it has good elasticity and wear resistance. PVC fiber's excellent acid and alkali resistance, anti-oxidation and reduction properties, and almost no moisture absorption also make it an ideal fiber material. In addition, PVC fibers are easy to mass produce and have good electrostatic properties. However, PVC fibers have relatively poor heat resistance and the dyeing process is difficult. Despite this, PVC fibers are still widely used in many application areas. For example, PVC fiber fabrics can be used for industrial filter cloths, work clothes, carpets, fishing nets, medical fabrics, chair cushions, protective equipment and various types of knitwear. Its flame retardant properties make it suitable for use in environments where fire protection is required, while its strength, wear resistance and chemical resistance make it suitable for the production of various industrial and daily necessities.
According to the "Access Conditions for the Chlor-alkali (Caustic Soda, Polyvinyl Chloride) Industry" issued by the National Development and Reform Commission of China in 2007, measures have been taken to promote the upgrading of the industrial structure and regulate the development of the industry in response to the blind expansion trend of the chlor-alkali industry, while encouraging the construction of supporting devices for calcium carbide and chlor-alkali production enterprises, and strengthening the construction of industrial integration devices. Under the guidance of China's policies, the central and western regions have abundant coal, salt mines and limestone resources, so the establishment of industrial integration devices has become an inevitable trend. By building an industrial system of coal-electricity-calcium carbide-PVC-calcium carbide slag cement, we have achieved optimal allocation of resources and improved production efficiency.
In the development process of Chinese PVC enterprises, they pay more and more attention to the diversification of production equipment processes and put forward higher requirements for technical levels. The development trend of process diversification is unstoppable. With the further development of China's PVC production process, enterprises need to gradually introduce some new production processes on the basis of retaining the traditional calcium carbide process, such as ethylene oxychlorination process, natural gas acetylene process and combined process, so as to enrich the diversity of production processes. At the same time, PVC polymerization technology will also be significantly improved, especially in the production capacity of polymerization kettles, which will be greatly improved.
The production cost of resin in the United States has dropped, but due to the stable demand in the US market and the increase in exports, the price of pipe-grade resin in China has stabilized at the average price in 2000, without any decline. Since 2000, US polyvinyl chloride manufacturers have continued to expand their production capacity to prepare for a new round of market competition. Syntec, Formosa Plastics, Westlake, and Borden have successively expanded their resin production capacity.
Due to the low production profit and the influence of the Greenpeace movement, the production capacity of Western European polyvinyl chloride manufacturers has been stagnant, but due to the continuous growth in the demand for polyvinyl chloride products, especially the huge demand for polyvinyl chloride doors and windows, water supply and drainage pipes in Europe, the development of European polyvinyl chloride has added stamina, and European polyvinyl chloride industry companies have invested in increasing production.
Due to the long-term economic recession in Japan, the production of polyvinyl chloride resin and China's consumption have continued to decline. Japanese polyvinyl chloride is mainly exported to mainland China and the Asia-Pacific region. The sharp drop in the price of polyvinyl chloride resin in China's market has also reduced the export volume of Japanese resins. The sluggishness of the polyvinyl chloride industry has also led to the reorganization of Japanese production companies, striving to make the industrial layout more reasonable.
PVC food cling film contains harmful substances, which are very harmful to the human body. The harmful substances are easily dissolved and contacted with food, and then enter the human body, which may cause carcinogenic effects and interfere with the human endocrine system. This interference can cause health problems such as breast cancer in women, congenital defects in newborns, male reproductive disorders and even mental illness.
According to Weng Yunxuan, director of the National Plastic Products Supervision and Inspection Center, there are two aspects of PVC food cling film that are harmful to human health. First, PVC materials contain chlorine, and vinyl chloride monomers may evaporate, which is potentially dangerous to the human body. Secondly, PVC cling film usually uses plasticizers such as ethylhexylamine (DEHA), which may dissolve and come into contact with food. DEHA substances may seep out and enter the human body with food, causing potential carcinogenic effects on human health, especially interfering with the endocrine system and hormones, thus causing greater harm to human health.
In daily life, the most commonly used plasticizer is phthalate esters, which are mainly used in the production of plastic products made of polyvinyl chloride (PVC) materials, such as cling film, plastic bottles, etc.
Professor Wu Yongning, chief scientist of the special food safety project of the National Health Commission of the People's Republic of China, pointed out that the molecular structure of phthalate diesters is similar to that of hormones and can simulate the effects of estrogen, and is called "environmental endocrine disruptors" or "environmental estrogens." If consumed for a long time, it may cause abnormalities in the reproductive-endocrine system, including hormone imbalance and decreased immunity, feminization of males, gender confusion in children, including shortened genitals and unclear sexual characteristics, inducing precocious puberty in children, and even the risk of teratogenicity and cancer.
GB 15581¡ª2016 Pollutant emission standards for caustic soda and polyvinyl chloride industries
GB/T3402.1-2005 "Plastic vinyl chloride homopolymer and copolymer resins Part 1: Naming system and specification basis"
GB5761 "Standard for suspension polyvinyl chloride"
ISO 1060-2
ASTM D1755 "Standard specification for polyvinyl chloride resin"
Including ultra-high molecular weight PVC resin, ultra-low molecular weight PVC resin, spherical PVC resin, blended PVC resin, (no) less skin PVC resin, PVC resin for powder coating, ultra-high absorbency PVC resin, etc.
Includes vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-vinylidene chloride copolymer resins, vinyl chloride-acrylonitrile copolymer resins, vinyl chloride-acrylate copolymer resins, vinyl chloride-vinyl ether copolymer resins, etc.
PVC grafted resins prepared by grafting modification, such as ethylene-vinyl acetate-vinyl chloride grafted copolymer resins, ACR-vinyl chloride grafted copolymer resins
Special PVC resins prepared by chemically modifying the side groups or end groups of PVC resins, such as chlorinated PVC resins, fluorinated PVC resins, aminated PVC resins, etc.
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