Production of Materials
The production of PVC(polyvinyl chloride) begins with the production of the monomer vinyl chloride. Main components include ethylene and chlorine. Ethylene(or ethane) may be produced by a variety of methods, these include catalytic cracking long hydrocarbon chains and steam cracking either by naphtha(methane) or ethane and propane. Depending on the cost each method has its place, typically steam cracking is utilised. Chlorine is sourced simply from the electrolysis of industrial grade salt(NaCl). These two compounds are combined in a ‘catalyst-containing reactor’ which creates the next necessary molecule known as Ethyl Dichloride(EDC). It is then heated to induce the thermal cracking of EDC and form the Vinyl Chloride Monomer. (Refer to ** for further information).
The most common method of polymerisation of the monomer Vinyl Chloride involves an addition polymerisation via a free radical all in suspension. In an aqueous dispersed solution it is heated at a temperature of approximately 50C under 13 atmospheres, keeping the Vinyl Chloride in liquid form. The initiator(free racial) is an organic peroxide typically Benzoyl Peroxide
Uses and Applications
PVC(Polyvinyl Chloride) has a widespread amount of uses in all aspects of society and industry. It may be found in all corners of the globe today.
Productions which contain the polymer are as follows, but not limited:
-Piping for water and gas in homes
The chemical properties of the product pertain to specific use it being tailored for. Primarily the structure of the polymer as well as addition plasticisers determine this.
Isotactic Polyvinyl Chloride-
The arrangement of the chlorine atoms in the structure allow chains to pack together closely & maximise intermolecular forces. It is therefore a hard and inflexible material.
Potential Developments and Directions
The process whereby polystyrene is produced involves the polymerisation of the monomer styrene or phenylethene via an addition reaction. Production naturally starts with its monomer, which undertakes makes reaction to be finalised and then polymerised. Initially via catalytic alkylation of Aluminium Chloride or zeolite catalysts into ethylbenzene(EB). It undergoes dehydrated into styrene via being in contact with steam over iron oxide catalysts, this reaction is ironically endothermic. For every kilogram is styrene produced 2.5-3 kilograms is required. The product is cooled rapidly to prevent premature polymerisation. Styrene as well as other by products as a result of the reaction include foulene, benzene and unreacted ethylbenzene is fractionally condensed and hydrogen is ‘flashed’ from the stream(refer to **). A polymerisation inhibitor is also added called phenol, thereafter the styrene is vacuum distilled in a series of four columns which react to a 99.8% purity.