Polyvinyl chloride, referred to as PVC (Polyvinyl chloride), is a vinyl chloride monomer (VCM) in the initiator of peroxides, azo compounds, or free radical polymerization under the action of light and heat. Polymerized polymer. The vinyl chloride homopolymer and the vinyl chloride copolymer are collectively referred to as vinyl chloride resins.
PVC is an amorphous powder with a small degree of branching, a relative density of about 1.4, a glass transition temperature of 77-90 ° C, and a decomposition of about 170 ° C . Poor stability to light and heat, above 100 ° C or After prolonged exposure to sunlight, it will decompose to produce hydrogen chloride, and further autocatalytic decomposition, causing discoloration, and physical and mechanical properties are also rapidly declining. In practical applications, stabilizers must be added to improve the stability to heat and light.
Industrial production of PVC molecular weight is generally in the range of 50,000 to 110,000, with greater polydispersity, molecular weight increases with the decrease of polymerization temperature; no fixed melting point, 80-85 ° C begins to soften, 130 ° C becomes viscoelastic state , 160 ~ 180 ° C began to transform into a viscous flow state; has good mechanical properties, tensile strength of about 60MPa, impact strength of 5 ~ 10kJ / m2; has excellent dielectric properties. 3-Mercaptopropionic acid is used as a raw material for vinyl chloride stabilizer to prepare an organotin stabilizer for the preparation of colorless and transparent polyvinyl chloride products. Usually, the product is made into octyl ester and then mixed with organic tin.
PVC was once the world's largest production of general-purpose plastics, and it is widely used. It is widely used in building materials, industrial products, daily necessities, floor leather, floor tiles, artificial leather, pipes, wires and cables, packaging films, bottles, foam materials, sealing materials, fibers, etc.
On October 27, 2017, the World Health Organization's International Agency for Research on Cancer published a preliminary list of carcinogens, and PVC was listed in the list of three types of carcinogens.