PVC and PVC stabilizers

Poly(vinyl chloride), PVC, is a common commodity plastic, and its production is the third largest, after polyethylene and polypropylene (Yoshioka et al., 2008). It is cost-effective, highly versatile and is used in many construction applications as water, sewage and drainage pipes, and a variety of extruded profiles (Van Es et al., 2008).

Thousands of rigid, semi-flexible and flexible (plasticized) materials and products based on PVC are widely used in practically all spheres of the world economy and will remain so for a very long time. From volume estimates, the world production of PVC grew from a few hundred million pounds to about 44 billion pounds in 2000 (Skip, 2006) as new uses and markets were
developed.

However, it is known that PVC degrades at elevated temperatures, giving off hydrochloric acid (HCl) that in turn accelerates the degradation process.

Depending on the number of conjugated double bonds formed, it becomes yellow, orange, red, brown and finally black (Sabaa and Mohamed, 2007). The splitting-off of HCl from the polymer backbone affects the physical, chemical and the mechanical properties of the polymer.

Until the discovery of thermal stabilizers, PVC was not an industrially very useful polymer, as it could not be processed to useful articles without degradation at elevated temperatures. Quantum improvements in extrusion and injection moulding machinery and extrusion die design, together with significant improvements in stabilizers and lubricant technology have all contributed to increased tonnage production and usage of PVC.