Chap._500005 - Degradation and Stabilization of PVC...

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Degradation and Stabilization of PVC Althought PVC is unaffected by acids and alkalis, the uncompounded PVC has relatively poor heat and light (UV) stability, which advisely effects the properties of polymer. In the degradation, a noteable discoloration (yellowing) occur, starting from white to yellow, to orange, to brown and black. Further heating causes a general deterioration in mechanical and electrical propertes. The commercial success of PVC has been very largely due to the discovery of stabilizers, the incorporation of which alleviates the effects of degradation and enables technologically useful materials to be made. The most important stabilizers include basic metal compounds, such as basic lead carbonate, dibasic lead phthalate, zinc carboxylate (laurate) and tin maleate, and epoxidized vegitable oils (linseed and soya bean). Stabilizing systems are very commonly made up of mixtures of stabilizers which have a synergistic effect on each other. The degadation of PVC has been the subject of extensive investigation and much information has been
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