CYANOGUANIDINE AND ITS COMPLEXES AS THERMAL STABILIZERS FOR RIGID POLY(VINYL CHLORIDE)

Cyanoguanidine and its complexes with cadmium and zinc have been investigated as thermal stabilizers for rigid PVC, at 180-degrees-C, in air. The results reveal the higher stabilizing efficiency of the investigated materials as shown by the longer induction periods obtained in their presence relative to those using dibutyl tin maleate, cadmium-barium stearate and basic lead carbonate, which are commonly used industrial stabilizers. The stabilizing efficiencies of the complex derivatives are higher than those of the parent cyanoguanidine. A synergistic effect is observed when cyanoguanidine is blended in various molar ratios with either of the soap stabilizers. The synergistic effect is probably due to the ability of cyanoguanidine for in-situ complexation with the metal chlorides which result as stabilization by-products, thus protecting the polymer from their deleterious accelerating degradative effect. An ionic mechanism for the stabilizing effect of cyanoguanidine and its derivatives is proposed.