The chemical mechanisms of outdoor weathering in polyvinyl chloride

Polyvinyl chloride weathering is a free radical mechanism started by absorption of energy sufficient to break chemical bonds. Absorption chromophores are often related to PVC heat history. Chemical bond energies are examined to indicate weak sites susceptible to initial degradation. Mechanisms of yellowing, oxidation, bleaching, and surface erosion are described. Some of the techniques for controlling the degradation of PVC are described. These techniques allow the PVC degradation to be controlled sufficiently so that PVC is accepted commercially as an excellent outdoor weathering material.