Co‐Precipitated Stearic Acid@β‐Cyclodextrin Anchors Zinc Species and Enhances Aging Stability of Natural Rubber

Vollständiger Abstract

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ABSTRACT Natural rubber (NR) composites frequently suffer from zinc stearate (ZnSt 2 ) blooming and performance degradation due to zinc migration. Herein, a host–guest strategy encapsulates stearic acid (SA) inside β‐cyclodextrin (β‐CD) to anchor Zn species and suppress blooming. Inclusion complexes prepared via co‐precipitation, ball milling, and physical mixing were systematically evaluated. Characterizations confirmed the superior structural stability of co‐precipitated SA@β‐CD, showing a reduced crystallinity index (43.2% vs. 86.4% for pure SA) and a higher onset decomposition temperature (278°C vs. 247°C for physical mixture). In NR composites, co‐precipitated SA@β‐CD extended scorch time (ts1 = 4.725 min vs. 3.125 min for standard NR) and achieved balanced mechanical strength (tensile strength: 23.01 MPa; tear strength: 63.23 kN/m) with minimized filler networking ( Δ G' = 424.55 kPa). After 96 h of thermo‐oxidative aging, the co‐precipitated composite retained 43.06% of tensile strength (25.43% for standard NR). XPS and EDS analyses revealed net surface Zn accumulation after 48 h aging was restricted to +0.39% (+0.63% for physical mixture), representing a 38.10% reduction in relative zinc enrichment. This supramolecular approach effectively restricts additive migration and improves long‐term rubber durability.