Polyvinyl chloride (PVC)
- Dec 22, 2018 -

The structure


PVC construction


PVC construction



PVC vertical structure of regular structure


PVC vertical structure of regular structure



Polyvinyl chloride (PVC) is a kind of polymer material that USES one chlorine atom to replace one hydrogen atom in polyethylene. The structure of this material is as follows: [-- CH2 -- CHCl --]n. PVC is a linear polymer of VCM monomer mostly connected by head - tail structure. The carbon atoms are in a zigzag arrangement. All the atoms are connected by sigma bonds. All carbon atoms are sp3 hybridized.



In PVC molecular chain, there is a short intersteroidal structure. With the decrease of polymerization temperature, the regularity of intermetric structure increases. Polyvinyl chloride macromolecular structure has the head structure, branch chain, double bond, allyl chloride, tertiary chlorine and other unstable structures, so that heat resistance deformation and poor aging resistance. Therefore, such defects can be eliminated by crosslinking.



Crosslinking is divided into radiation crosslinking and chemical crosslinking.



1. Radiation cross-linking. Use high-energy rays, generally those produced by cobalt-60 radiation sources or those generated by electron acceleration, mainly the latter. Additionally, two or more carbon - carbon double - bond monomers are added for crosslinking. But it is difficult to operate and requires high equipment.



2. Chemical crosslinking. Triazole dimercaptosulfhydrate (FSH) was used for crosslinking. The crosslinking mechanism was the substitution reaction of amines and mercaptosulfhydryl groups to attack the carbon-chlorine polar bonds. After crosslinking, the properties of the product, such as uv resistance, solvent resistance, temperature resistance, impact toughness and so on, will be comprehensively improved.