Polymer‐Crosslinking System‐Filler Interactions in Polychloroprene Adhesives: Experimental and Molecular Modeling Insights

ABSTRACT Polychloroprene (CR), widely used in rubber and adhesives, is typically crosslinked with ZnO/MgO, but environmental concerns over metal oxides have led to the search for safer alternatives. This study evaluates Fe(acac) 3 as a crosslinking catalyst in solvent‐based CR adhesives. Fumed silica (2–6 phr) was added to CR‐Fe(acac) 3 adhesives to enhance mechanical and adhesion properties, while CR‐ZnO controls used higher loadings of micrometric fillers (15–53 wt%). Swelling and rheometric analyses showed Fe(acac) 3 increased crosslink density by 1.5–3 times. However, higher filler content slowed crosslink reaction in both systems. In CR‐Fe(acac) 3 compounds, increasing silica from 2 to 6 phr reduced crosslink density by ~15% but improved adhesive and mechanical performance. Based on molecular modeling, a crosslinking reaction mechanism was proposed in which the rate‐determining step exhibits a barrier height of approximately 90 kcal·mol −1 . The in silico experiments also confirmed a competing reaction between silanol groups on the silica surface and the Fe(acac) 3 catalyst, which presents an activation energy ~92% lower than CR‐CR crosslinking reaction, thereby reducing the catalytic effectiveness of Fe(acac) 3 . Furthermore, the formation of hydrogen bonds between the silanol groups on the silica surface and the CR chains was identified, which can explain the enhancement in the secondary relaxation temperature of CR as silica content increases.