Electrical Aplication - Essay Example

In a typical VCM plant these are initially reacted together to form an important process intermediate, ethylene dichloride (EDC). 2.) an EDC cracking unit, in which EDC is thermally decomposed into VCM and hydrogen chloride. The hydrogen chloride is recycled as feedstock to a further stage, the oxychlorination unit, while unconverted EDC is separated and recycled. The VCM is purified for use in PVC production. 3.) an oxychlorination unit, in which recycled hydrogen chloride is reacted with further ethylene feedstock in the presence of copper chloride catalyst and oxygen.

This produces further quantities of EDC, while excess hydrogen is oxidised to form water. VCM is polymerised in large scale batch reactors in the presence of water, initiators (catalysts) and other additives. The suspended droplets of liquid monomer are progressively converted to solid or porous PVC particles, depending on grade. Unreacted VCM is stripped from the polymer, and water is separated by centrifuging. The polymer is then dried, typically in fluidised bed drying equipment. Suspension PVC is used for virtually all extrusion, injection moulding and film making processes.

Individual grades are characterised by their melt flow properties and their suitability for rigid (unplasticised) or flexible (plasticised) applications. The polymerisation stage involves an emulsion of very fine droplets of VCM in water, and the process forms a stable emulsion, or latex, of polymer in water. After the removal of unreacted monomer, the water is removed by evaporation in spray drying equipment. PVC compounds are prepared by blending PVC resin with additives to give the required properties in the fabricated finished product.

The additives, which include plasticisers, stabilisers, lubricants, fillers, impact modifiers and pigments, will make the PVC either flexible or rigid. In the calendering process, the PVC mixture is initially melted in the gap between two