PVC - Suspension PVC（1）
DATE：2023/1/5 8:57:02 / READ： / SOURCE：This station
Polyvinyl chloride (PVC) resin is polymerized by vinyl chloride under the action of initiator. Polyvinyl chloride is one of the earliest industrialized plastics in the world. At present, the output of PVC resin and its products is second only to that of polyethylene, ranking the second in the output of various plastic products. In 2006, the output of PVC in China reached 7.641 million tons.
Polyvinyl chloride (PVC) is a kind of plastic with good comprehensive properties, such as flame retardancy, chemical corrosion resistance, abrasion resistance, good electrical insulation, and good mechanical strength; Because of its low price, it has always been a rapidly developing and widely used variety. In order to improve the poor thermal stability, easy decomposition, strain sensitivity and low temperature hardening of PVC, and to adapt to the application of various occasions and environments, copolymers with various special properties, mainly PVC, have been developed. At present, there are more than 1000 varieties and brands of products. PVC resin can be divided into suspension polychlorinated polyethylene, lotion PVC, bulk PVC and micro suspension PVC according to different production polymerization methods; In addition, chlorinated polyvinyl chloride, cross-linked polyvinyl chloride, high molecular weight polyvinyl chloride and some special polyvinyl chloride with special properties are widely used in the modified varieties of polyvinyl chloride. Among them, suspension PVC is the most widely used, accounting for 85% of the total PVC resin production.
Suspension PVC resin structure can be divided into tight type and loose type. At present, the PVC resin used is loose type. See Table 2-64 for the technical indexes of loose PVC specified in the standard GB/T 5761-93.
The PVC resin produced in the domestic chlor alkali plant is named according to the degree of polymerization, and its technical indicators are shown in Table 2-65.
2.3.1.1 Performance characteristics
① White amorphous powder with particle size of 60-250 μ Within the range of m, the apparent density is 400~600kg/m3, the product density is 1.4~1.6g/cm3 for hard products, and 1.2~1.4g/cm3 for soft products
② Thermal property of PVC: there is no obvious melting point. It begins to soften at 80~85 ℃ and becomes viscoelastic at about 130 ℃, becomes viscous fluid at 160~180 ℃, decomposes at 200~210 ℃, and embrittlement at - 60~- 50 ℃.
③ It has poor stability to light and heat. If it is exposed to sunlight for more than 100 ℃ or for a long time, it will decompose and produce hydrogen chloride.
④ Compared with other thermoplastics, it has higher mechanical strength, abrasion resistance than vulcanized rubber, and hardness and rigidity than polyethylene.
⑤ It is difficult to burn and can extinguish itself without fire source.
⑥ The dielectric property is very good, and the insulating capacity of DC and AC is similar to that of hard rubber, which is a kind of insulating material with low dielectric loss.
⑦ It is insoluble in water, alcohol and gasoline, and can expand and dissolve in ether, ketone, chlorinated fatty hydrocarbon and aromatic hydrocarbon; It is resistant to hydrochloric acid of different concentrations, sulfuric acid of less than 90%, nitric acid of 50%~60% and caustic soda solution of less than 20% under normal temperature, and is quite stable to salts.
⑧ PVC plastics have hard and soft types. In the resin of molded products, the plasticizer added less than 10% is hard plastic, the plasticizer added more than 30% is soft plastic, and the plasticizer added between 10% and 30% is semi hard plastic. See Table 2-66 for performance indexes of PVC. The disadvantage of PVC is its poor thermal stability, and the formulation and process of raw material molding products are relatively complex.
Author：admin