The main composition structure of polyvinyl chloride resin

PVC is polyvinyl chloride (English: Polyvinyl Chloride, abbreviated as: PVC), which is a polymer material obtained by addition polymerization of vinyl chloride. It is the third most widely produced synthetic plastic polymer after polyethylene and polypropylene. .

PVC is a white powder with amorphous structure, poor stability to light and heat, no fixed melting point, good mechanical properties, and excellent dielectric properties.

Polyvinyl chloride is a polymer material that uses one chlorine atom to replace one hydrogen atom in polyethylene, and is an amorphous polymer with a small amount of crystalline structure. The structure of this material is as follows: [-CH2-CHCl-]n. PVC is a linear polymer in which VCM monomers are mostly linked in a head-tail structure. The carbon atoms are arranged in a zigzag pattern, and all atoms are connected by σ bonds. All carbon atoms are sp3 hybridized.

There is a short syndiotactic stereoregular structure on the PVC molecular chain. As the polymerization temperature decreases, the syndiotactic tacticity increases. In the macromolecular structure of PVC, there are unstable structures such as head-to-head structure, branched chain, double bond, allyl chloride, tertiary chlorine, etc., which make thermal deformation and aging resistance poor. After pretending to be cross-linked, such disadvantages can be eliminated.

Crosslinking is divided into radiation crosslinking and chemical crosslinking.

1. Radiation crosslinking. High-energy rays are used, generally the rays generated by cobalt 60 radiation sources or the electron rays generated by electron acceleration, and the latter is mainly used. Then add a crosslinking assistant (monomer with two or more carbon-carbon double bond structures) for crosslinking. However, it is difficult to operate and requires high equipment.

2. Chemical cross-linking. Triazole dimercaptoamine salt (FSH) is used for cross-linking. The cross-linking mechanism is that amine and sulfhydryl combine to attack carbon-chlorine polar bonds to carry out substitution reaction. After cross-linking, the UV resistance, solvent resistance, temperature resistance, impact toughening and other properties of the product will be comprehensively improved.