Photostabilization of PVC

The low cost and excellent performance of poly(vinyl chloride) (PVC) make it a very attractive and suitable plastic for a wide variety of applications. With respect to the production and consumption of synthetic materials, it stands third in the world after polyethylene and polypropylene. However, PVC suffers from poor thermal and light stability. It undergoes rapid autocatalytic dehydrochlorination upon exposure to heat and light during its molding and use, respectively. As a result, conjugated polyene sequences are formed from the beginning of the reaction, and they give rise to discoloration of the polymer and seriously change its physical properties. Degradation also causes a drastic change in the mechanical properties of the polymer, which is accompanied by a decrease or increase in its average molecular weight as a result of either chain scission or crosslinking of the polymer molecules, respectively.