Poly vinyl chloride(PVC)
Polyvinyl chloride forms from Resin, the main component. It is white, brittle solid material available in powder form or granules.
PVC is now replacing traditional constructional materials like ceramics, metal, concrete, wood, rubber and many more. However PVC forms by the process of polymerization of the vinyl chloride monomer.
Polyvinyl Chloride is amorphous in nature, and hence it easily combines with other chemicals/substances.
Physical properties of Polyvinyl Chloride
·They are brittle and solid in nature and insoluble in Alcohol, but soluble in Hydrofluran,
·They show high amount of Hardness and show thermoplasticity, as the mechanical properties increase with the Increase in temperature.
· Heat Stability of PVC is quite poor as they begin to decompose once the temperature reaches 140 °C,the melting point of PVC is 160 °C.
·The elasticity of PVC reaches to 1500-3000 Mpa. They have ordinary friction.
· PVC shows good insulation properties, but its insulating property is less than that of Polyethylene.
· As the dielectric constant, dielectric loss tangent value and volume resistivity are high, the corona resistance is not very good, it is generally suitable for medium or low voltage and low frequency insulation materials
Polymerization of PVC
The polymerization of VCM is starts by the droplets and mixes by compounds like initiators, the radical chain reaction begins when these initiators break down.
For instance initiators include dioctanoyl peroxide and diacetyl peroxydicarbonate, both of which have fragile O-O bonds .to bring about a uniform rate to a polymerization reaction, a combination of initiators is useful.
some initiators start the reaction rapidly but later slow down while others show the opposite therefore a combination of initiators are useful to bring a steady rate to polymerization reaction.
In the course of the reaction, a PVC slurry is formed which is subjected to degas and stripping to remove excess VCM which is also recycled.
The slurry is further dried in a hot air bed, and the resulting powder sieved before storage or pelletization. Normally, the resulting PVC has a VCM content of less than 1 part per million.
PVC in its hard form is used in:
· Machined Parts and chemical Resistant Applications
· They are useful in Wet Benches and Vinyl records, · Plumbing works and electrical fixtures
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