THE EFFECTS OF SEPIOLITE LOADINGS ON MECHANICAL, THERMAL, AND MORPHOLOGICAL CHARACTERISTICS OF NATURAL RUBBER/EPOXIDISED NATURAL RUBBER (NR/ENR-25) BLENDS

Sepiolite has been used widely as nanofillers to improve the properties and compatibility of rubber blends, and due to its magnesium silicate hydrates contents, the sepiolite may also function as a thermal stabilizer. These works investigate the effects of sepiolite loadings on curing, mechanical, thermal, and morphological characteristics of natural rubber/epoxidized natural rubber (NR/ENR-25) blends. The blends were made using a two-roll mill technique using standard vulcanization reagents of sulfur and carbon black as the main filler, and their vulcanization characteristics were investigated using the rheometry technique. Furthermore, the thermal, mechanical, and morphological characteristics of the blends were evaluated using thermogravimetry, tensile tests, and electron microscopy, respectively. It was found that an increase in the sepiolite loadings decreased scorch times (ts2 and t90), whereas optimum sepiolite loading with higher tensile strength was 3 phr, which lowered down when the sepiolite loading was increased up to 9 phr. The thermogram of blend specimen with 3 phr sepiolite loading also exhibited superior thermal stability, that is, has higher degradation temperature at 5% weight loss. Fracture surface SEM photographs of the blend specimens showed finely distributed sepiolite particles at optimum sepiolite loading 3 phr and exhibited agglomerations when the loadings were increased up to 9 phr.