N-Substituted maleimides as thermal stabilizers for plasticized poly(vinyl chloride)

Abstract

N-Substituted maleimides have been investigated as thermal stabilizers for plasticized PVC at 180°C in air by measuring the rate of dehydrochlorination and the extent of discoloration of the degraded polymer. The results reveal a higher stabilizing efficiency of the products investigated compared with basic lead carbonate, dibutyl tin maleate, and barium-cadmium stearate stabilizers which are commonly used industrially. The induction period (Ts) is influenced by the nature and position of substituents in the aryl ring together with the nature of the plasticizer used. Moreover, it has been found that the stabilizers investigated impart better color stability to the degraded samples compared with the stearate stabilizer. A synergistic effect was achieved when the products investigated were used as mixtures with the reference stabilizer in equimolar ratios. A radical mechanism is proposed which illustrates the stabilizing action of the products investigated. © 1990.