Possible use of sludge ash as filler in natural rubber

Abstract

Potential use of sludge ash as a filler in NR was studied. In this study, two grades of sludge ash namely SA-300 and SA-700 were prepared by sintering sludge waste obtained from concentrated natural rubber (NR) latex production at 300 and 700 °C, respectively. Properties of NR filled with various contents of SA-300 and SA-700 were then investigated and compared with those of NR filled with precipitated calcium carbonate (CaCO3). The results reveal that, regardless of the filler type, both scorch time (t s1) and optimum cure time (t c90) decrease whereas hardness and modulus increase with increasing filler loading. At a given loading, both SA-300 and SA-700 give shorter scorch time and cure time with higher hardness and modulus than CaCO3. Due to their higher specific surface area and greater cure activation efficiency, SA-300 and SA-700 provide better reinforcement, i.e., greater tensile strength; tear strength and abrasion resistance than CaCO3. Taken as a whole, it could be said that the two grades of sludge ash could be utilized as rubber fillers with economic advantage.