What is PVC ?
What is PVC
Plastics are also called synthetic resins and are broadly classified into two categories: thermosetting resins and thermoplastic resins. The thermosetting resins include phenolic resin and melamine resin, which are thermally hardened and never become soft again. Thermoplastic resins include PVC, polyethylene (PE), polystyrene (PS) and polypropylene (PP), which can be re-softened by heating.
Main synthetic resins and their raw materials chart
Usually, thermoplastics are supplied in the form of pelletised material (compounds) with additives (antioxidants, etc.) already blended in it. However, PVC resin is often supplied in powder form and long term storage is possible since the material is resistant to oxidation and degradation. Various additives and pigments are added to PVC during the processing stage, and the blend is then converted into PVC products. PVC is sometimes known as ‘Vinyl’ in Europe and predominantly so in North America. In Europe, ‘Vinyl’ usually refers to certain specific flexible applications, such as flooring, decorative sheets and artificial leather. PVC_pellets_(Ineos)WEB
PVC is a thermoplastic made of 57% chlorine (derived from industrial grade salt) and 43% carbon (derived predominantly from oil / gas via ethylene). It is less dependent than other polymers on crude oil or natural gas, which are nonrenewable, and hence can be regarded as a natural resource saving plastic, in contrast to plastics such as PE, PP, PET and PS, which are totally dependent on oil or gas. This chlorine gives to PVC excellent fire resistance. A Petrochemical Product
Although PVC can be produced from a range of hydrocarbons including coal, and derivatives of plants such as sugar cane, the bulk of world production is currently manufactured using the chemical compound ethylene. Ethylene (or ethene) which has the chemical formula C2H4, is a product of the oil & gas industry. PVC is therefore considered to be a petrochemical product. At the start of the ethylene-based PVC production process, the ethylene is combined with chlorine to produce an intermediate chemical known as EDC (ethylene dichloride or 1,2-dichloroethane).
Almost all EDC is used for PVC production in Europe, although a small portion is used for manufacturing of ethylenediamine, organic solvents and various pharmaceutical products. Three major applications, polyethylene (PE), EDC and styrene monomer (SM) account for about 78% of all ethylene consumption (almost all styrene is used for PS).
Western European ethylene consumption (kt) in 2004
The petroleum refining industry and the basic petrochemical industry in Western Europe are predominantly located in coastal areas or where rivers or pipelines provide easy access to imported natural resources such as crude oil. They form petrochemical complexes, where refineries, crackers and petrochemical plants are connected by pipelines. The chlor-alkali (caustic soda) industry is often located together with petrochemical complexes or near deposits or rock salt. VCM plants, which use ethylene and chlorine as major raw materials, and PVC plants, are generally located in petrochemical complexes due to this background. Ethylene which is one of five types of products that are yielded by cracking of naphtha, and downstream on to the production of petrochemical products such as general purpose plastics.
Production flow of a typical petrochemical complex
PVC and chlorine
Ethylene and chlorine are the major raw materials for VCM. Therefore, VCM is affected by the supply-demand conditions of both ethylene and chlorine, respectively. In Western Europe the share of VCM amounts to 14% of all ethylene use (ethylene requirement). In contrast, VCM amounts to 35% of all chlorine use. This is why the demandsupply balance of chlorine has a greater impact on VCM than that of ethylene.
The balance between chlorine and caustic soda
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