A novel zinc-containing additive for the long-term thermal stabilization of poly(vinyl chloride)

A Zn-containing complex ([ZnL2]·xH2O, x ≈ 4, abbreviated as ZnL2; HL = 1,3-dihydroxy-2-hydroxymethyl-2-(salicylidimino)propane) was synthesized and used as a thermal stabilizer. Through discoloration and dehydrochlorination tests at 180 °C, ZnL2 was proved to be a co-stabilizer of long-term thermal stability for poly(vinyl chloride) (PVC): compared with the PVC samples stabilized using typical metallic soap stabilizers with the mass ratio of calcium stearate (CaSt2) to zinc stearate (ZnSt2) ranging from 1.5/0 to 0/1.5, whose induction time (ti), stability time (ts) respectively ranged from 9 to 54 min, from 12 to 56 min, the PVC samples stabilized using combinations with the mass ratio of CaSt2 to ZnL2 from 1.5/0 to 0/1.5 showed apparent thermal stability with ti, ts ranging from 44 to 85 min, from 49 to 88 min. PVC sample (PVC resin = 50.0 g, ZnL2 = 1.5 g, pentaerythritol = 0.3 g, dioctyl phthalate = 2.5 g) displayed a significant long-term thermal stability with ti of 102 min, ts of 105 min, and totally-turning-black time of 170 min.