Abstract

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Four novel antimicrobial maleimido phenyl thiourea stabilizers 1-4 were synthesized from N-[4-(chlorocarbonyl) phenyl] maleimide with phenyl thiourea and its derivatives (p-methyl, o-chloro and p- carboxy). The effect of mixing maleimido phenyl thiourea stabilizer 2 with each of the reference stabilizers: dibasic lead carbonate (DBLC), cadmium-barium-zinc stearate (Cd-Ba-Zn stearate) or n-octyltin mercaptide (n-OTM) on the stabilization efficiency against thermal degradation of rigid PVC at 180oC, in air, has been investigated. Mixing was effected in the range of 0-100 wt% of stabilizer 2 relative to each of the reference stabilizers. The stabilizing efficiency was evaluated by measuring the length of the thermal stability period (Ts), the period during which no detectable amounts of hydrogen chloride gas could be observed, and also from the rate of dehydrochlorination as measured by continuous potentiometric determination on the one hand, and the extent of discoloration of the degraded polymer samples on the other. The results show a true synergistic effect from the combination of stabilizer 2 with any of the reference stabilizers. Mixing of the stabilizers improves the Ts values, decreases the rate of dehydrochlorination, and lowers the extent of discoloration of the polymer. The maximum synergism was attained when the stabilizer 2 is mixed with either of the three reference stabilizers in equivalent weight ratio (50%/50%). The observed synergism may be attributed to the different mechanisms by which the investigated and the reference stabilizers work.

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