Surface-functionalized layered double hydroxides (LDHs) nanoplatelets for enhanced thermal stability of plasticized polyvinyl chloride (PVC) films

Polyvinyl chloride (PVC) is the third most produced plastic globally and a significant contributor to plastic waste. Thermal stabilizers are essential for PVC processing to prevent degradation, a role that becomes even more critical in recycling techniques where repeated reprocessing exacerbates degradation issues. Recent studies have explored layered double hydroxides (LDHs) as promising PVC stabilizers, offering a balance between stabilization efficiency, environmental impact, and cost. However, achieving effective compatibilization with PVC remains a challenge. In this study, we provide mechanistic insights into LDH stabilization by proposing a four-stage reaction mechanism during PVC degradation. This mechanism highlights the roles of interlayer anions, the interactions of basic metal components (Mg, Zn, Al), and the contribution of each element to LDH’s acid-neutralizing capabilities in suppressing HCl release. Raman spectroscopy confirmed that Zn contributes the most to HCl absorption due to its higher electronegativity and affinity for HCl, while Mg exhibits a delayed interaction, and Al contributes at later stages, indicating a progressive role in stabilization. To further enhance LDH stabilization efficiency, we modified LDH by retaining oleic acid (OA) on its surface. The introduction of OA improved LDH-PVC compatibility and enhanced HCl absorption through the reactivity of OA’s C=C bonds under acidic conditions. Unlike stearic acid, OA contributed to neutralization reactions and reinforced PVC stabilization. The OA-modified LDH (MC-9OA) demonstrated more than a twofold increase in static thermal stability compared to unmodified LDH-PVC compounds. These findings highlight both the fundamental stabilization mechanism of LDHs in PVC and the enhancement achieved through OA modification. This dual approach contributes to the sustainability of PVC products by improving their thermal stability, particularly in recycling applications.