Polyvinyl Chloride PVC -1
Polyvinyl Chloride (PVC) is one of the most widely used polymers in the world. Due to its versatile nature, PVC is used extensively across a broad range of industrial, technical and everyday applications including widespread use in building, transport, packaging, electrical/electronic and healthcare applications.
PVC is a very durable and long lasting material which can be used in a variety of applications, either rigid or flexible, white or black and a wide range of colours in between.
The first patent for a polymerisation process to manufacture PVC was granted to German inventor Friedrich Klatte in 1913 and PVC has been in commercial production since 1933. The material now accounts for about 20% of all plastic manufactured world-wide, second only to polyethlene.
1 Production
The essential raw materials for PVC are derived from salt and oil. The electrolysis of salt water produces chlorine, which is combined with ethylene (obtained from oil) to form vinyl chloride monomer (VCM). Molecules of VCM are polymerised to form PVC resin, to which appropriate additives are incorporated to make a customised PVC compound .
The PVC production process consists of 5 steps:
- The extraction of salt and hydrocarbon resources
- The production of ethylene and chlorine from these resources
- The combination of chlorine and ethylene to make the vinyl chloride monomer (VCM)
- The polymerisation of VCM to make poly-vinyl-chloride (PVC)
- The blending of PVC polymer with other materials to produce different formulations providing a wide range of physical properties.
1.1 Raw Materials
PVC takes less non-renewable fossil fuel to make than any other commodity plastic because unlike other thermoplastics which are entirely derived from oil, PVC is manufactured from two starting materials;
- 57% of the molecular weight derived from common salt
- 43% derived from hyrdocarbon feedstocks (increasingly ethylene from sugar crops is also being used for PVC production as an alternative to ethylene from oil or natural gas)
Whilst PVC is most frequently made from salt and oil, in some regions of the world PVC is made without using oil feedstock at all (substituting oil-derived hydrocarbon with bio-derived hydrocarbon feedstock). PVC is therefore far less oil-dependent than other thermoplastics. It is also highly durable and energy efficient across a range of applications, which makes for an extremely effective use of raw materials.
- There are over 50 quadrillion tonnes of salt exist dissolved in the sea, with over 200billion tonnes of salt available underground - reserves of this material are clearly abundant
- Ethylene from oil equates to 0.3% of annual oil usage, but increasingly etheylene from sugar crops is also being used for PVC production.