PVC – a thermoplastic
Plastics, or synthetic resins, are classified into two broad categories: thermosetting resins and thermoplastic resins. PVC falls into the thermoplastic resins, which also include polyethylene (PE), polystyrene (PS) and polypropylene (PP). These hard plastics can be softened again through heating. On the other hand, thermosetting resins, that include phenolic resin and melamine resin, are thermally hardened and never become soft again.
PVC is made of 57% chlorine and 43% carbon (derived predominantly from oil or gas via ethylene). PVC production uses less unrenewable resources - oil or natural gas - than other plastics, and it can therefore be regarded as a resource-saving plastic. In contrast, the production of plastics such as PE, PP, PET and PS is completely dependent on oil or gas.
Thermoplastic resins are often supplied in the form of pelletised material (compounds) with additives (antioxidants, etc.) already blended into it. However, PVC resin can also be supplied in powder form, which it often is, as this powder form is resistant to oxidation and degradation, allowing for a long storage period. Various additives and pigments are then added to the powder during the processing stage, producing a blend that is converted into various PVC products.
PVC is predominantly known as ‘Vinyl’ in North America, and while in Europe this is sometimes the case, ‘Vinyl’ usually refers to certain specific flexible applications, such as flooring, decorative sheets, musical records and artificial leather.
Building & constructionAbout 70% of the PVC is used for durable, affordable and recyclable building & construction products such as pipes, windows, cables, flooring and roofing.
Medical devicesFor over 60 years, PVC has been the material of choice for disposable medical devices such as blood bags and medical tubing. PVC medical devices are safe, affordable and pilot projects in several countries show a great potential for recycling of used PVC medical equipment. Go to pvcmed.org to find out more.
The history of PVC
From the earliest times, human kind has worked to develop synthetic materials that offer benefits not found in natural materials. PVC is one of the oldest synthetic materials, with the longest history in industrial production. Its discovery dates back to the 19th century, when PVC was accidentally discovered on two occasions, by French physicist Henri Regnault and by the German Eugen Baumann. On both occasions, the newly discovered vinyl chloride gas was left exposed to sunlight, producing a white solid – PVC. However, the material was difficult to work with, and its commercial application did not come until the 1920s.
In the early 1900s, American company BFGoodrich hired industrial scientist Waldo Semon to develop a synthetic replacement for the increasingly costly natural rubber. Semon’s experiments produced polyvinyl chloride, but the 1920s recession threatened the abandonment of the development of the material, However, Semon conceived the idea of PVC as a water resistant coating for fabrics, and sales took off quickly with a rapidly expanding product range. Demand accelerated again during the Second World War, when PVC quickly replaced traditional material to insulate wiring on military ships.
During the 1950's many more companies started to produce PVC and volumes increased dramatically around the world. Developers quickly found further, innovative uses and refined methods to enhance durability, opening the door to PVC being used in building and construction. PVC products rapidly became essential to the construction industry, due to the plastic's resistance to chemicals, corrosion and light.By the mid 20th century, five companies were producing PVC, and new uses continued to be found well into the 1960s.
After improvement was made to the material’s resistance to extreme temperatures, PVC began to be used for transporting water to homes and industries. By the 1980s, twenty companies were producing PVC. Today, PVC is the third largest-selling commodity plastic in the world, after polyethylene and polypropylene. PVC's low cost, ability to processed or recycled and excellent durability make it the material of choice for dozens of industries, such as health care, IT, transport, textiles and, of course, construction.