Effect of allantoin on the stabilization efficiency of Ca–Zn thermal stabilizers for poly(vinyl chloride)

The influence of allantoin (ALL) combined with zinc stearate (ZnSt 2 ), calcium stearate (CaSt 2 ), and ZnSt 2 –CaSt 2 (1:1), respectively, in different mass ratios on thermal stability of poly(vinyl chloride) (PVC) was investigated by Congo red test, discoloration test, and thermogravimetric analysis. The results indicated that ALL behaved as a good long-term thermal stabilizer for PVC, which was attributed to its ability to absorb hydrogen chloride released from the degradation of PVC. Moreover, ALL was able to extend the stabilization time of PVC containing ZnSt 2 –CaSt 2 and postpone “zinc burning.” Fourier transform infrared spectra confirmed that ALL can react with ZnCl 2 to produce an inert complex, which is responsible for postponing “zinc burning.”