This study explores the optimization of organomodified montmorillonites (OMMT)—Cloisite 20A (20A), MAX CT 4260 (CT), and Cloisite SE 3000 (SE)—in combination with alumina trihydrate (ATH) for enhancing natural rubber (NR) formulations used in conveyor belt cover applications. The combined effects of OMMT and ATH on the mechanical, thermal, and flame-retardant properties of NR compounds were systematically evaluated. Morphological characteristics were examined using wide angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). Polymer-filler and filler-filler interactions were assessed via rubber process analyzer (RPA), Dynamic mechanical analysis (DMA), and standard mechanical testing. Flame retardancy and thermal stability were analyzed through limiting oxygen index (LOI), UL-94 horizontal flammability tests, and thermogravimetric analysis (TGA). Additionally, thermal degradation kinetics were investigated using iso-conversional models—Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Friedman’s method. The results reveal a synergistic enhancement in both flame retardancy and thermal stability with the OMMT-ATH hybrid system, demonstrating its potential as a high-performance filler combination for NR-based conveyor belt cover compounds.

Keywords: natural rubber, nanoclay, intumescent flame retardants, activation energy, thermal degradation kinetics.