Polyvinyl chloride (PVC) is a polymer polymerized by vinyl chloride monomer (VCM) in peroxide, azo compound and other initiators or according to the free radical polymerization mechanism under the action of light and heat. Vinyl chloride homopolymer and vinyl chloride copolymer are collectively referred to as vinyl chloride resin.

PVC is a white powder with amorphous structure, with small branching degree, glass transition temperature of 77 ~ 90 ℃, and it begins to decompose at about 170 ℃ [1]. It has poor stability to light and heat. When it is above 100 ℃ or exposed to sunlight for a long time, it will decompose to produce hydrogen chloride, and further Autocatalytic Decomposition will cause discoloration, and its physical and mechanical properties will also decline rapidly, In practical application, stabilizer must be added to improve the stability to heat and light.

The molecular weight of industrial PVC is generally in the range of 50000 ~ 110000, with great polydispersity. The molecular weight increases with the decrease of polymerization temperature. There is no fixed melting point. It begins to soften at 80 ~ 85 ℃, changes to viscoelastic state at 130 ℃, and changes to viscous flow state at 160 ~ 180 ℃; It has good mechanical properties, with tensile strength of about 60MPa and impact strength of 5 ~ 10kj / m2; It has excellent dielectric properties.

PVC was once the world’s largest general-purpose plastic, which was widely used. It is widely used in building materials, industrial products, daily necessities, floor leather, floor tiles, artificial leather, pipes, wires and cables, packaging film, bottles, foaming materials, sealing materials, fibers and so on.

Polyvinyl chloride (PVC) is a kind of polymer material that uses one chlorine atom to replace one hydrogen atom in polyethylene. It is an amorphous polymer containing a small amount of crystalline structure. The structure of this material is as follows: – (ch2-chcl) n -. PVC is a linear polymer of VCM monomers, most of which are connected by head tail structure. Carbon atoms are arranged in a zigzag shape, and all atoms are arranged in a zigzag shape σ Key connection. All carbon atoms are SP3 hybrid.

There is a short syndiotactic regular structure on the PVC molecular chain. With the decrease of polymerization temperature, the regularity of syndiotactic structure increases. There are some disadvantages in the macromolecular structure of PVC, such as head structure, branched chain, double bond, allyl chloride, tertiary chloride and so on. Therefore, such shortcomings can be eliminated after crosslinking.

Crosslinking can be divided into radiation crosslinking and chemical crosslinking.

1. Radiation crosslinking. High energy rays are used, generally those generated by cobalt 60 radiation source or electron rays generated by electron acceleration, and the latter is mainly used. Then, crosslinking AIDS (monomers with two or more carbon carbon double bond structures) are added for crosslinking. However, the operation is difficult and requires high equipment.

2. Chemical crosslinking. Triazole dimercaptoamine salt (FSH) was used for crosslinking. The crosslinking mechanism was that amine combined with sulfhydryl group attacked carbon chlorine polar bond and carried out substitution reaction. After crosslinking, the UV resistance, solvent resistance, temperature resistance, impact toughening and other properties of the product will be comprehensively improved.