A new insight into the synergetic thermal stability effect of acetylacetone derivatives and zinc arginine on polyvinyl chlorine under static and dynamic thermal aging conditions

Zinc arginine [Zn(Arg)₂] was a zinc salt stabilizer with excellent initial whiteness and long-term thermal stability for PVC, as reported by our previous work. Clarifying the synergistic thermal stability mechanisms of Zn(Arg)₂ and its auxiliary stabilizers under dynamic and static conditions was an important scientific issue to guide the practical application of Zn(Arg)₂. In this work, acetylacetone (ATE) was found to be a good auxiliary thermal stabilizer with Zn(Arg)₂ for PVC, especially at the 4:6 ratio of ATE and Zn(Arg)₂. However, the best ATE derivatives under static and dynamic conditions were not the same, which were ATE and stearoylbenzoylmethane (SBM), dibenzoylmethane (DBM), and benzoylacetone (BZT), respectively. The reasons were that ATE derivatives could react with Zn(Arg)₂ and produce zinc acetylacetonate (Zn-ATE) under the static thermal aging condition. However, under dynamic thermal aging conditions, ATE derivatives replaced unstable chlorine atoms on the PVC chains by the α-C between two carbonyl groups through an alkylation reaction. The conclusions were confirmed by the calculation results of the natural population analysis (NPA) charge. In addition, the compatibility of ATE derivatives and PVC was another reason for the thermal stability and transparency of PVC samples.

Highlights

• The synergistic effect of zinc, arginine, and acetylacetone derivatives was investigated.
• There are two different synergistic effects under static and dynamic thermal aging conditions.
• Zinc, arginine, and acetylacetone reacted under static thermal aging conditions.
• The natural population analysis charge was used to confirm the two mechanisms.