Mechanical, swelling, and thermal aging properties of marble sludge-natural rubber composites

Background: A large amount of post-consumer marble sludge waste is thrown away into landfills. The need to reuse this waste is increasing day by day due to the environmental concern and energy conservation. The purpose of this work is to explore the use of this waste for low-cost natural rubber composites. In the experimental part, three different microsizes: 10, 20, and 75 μm, with five different levels of loading up to 90 parts per hundred of rubber (pphr) were used in natural rubber (NR) composites to study the effect of marble sludge (MS) loading on the mechanical properties. Results: Application of MS as filler enhanced many properties such as tensile strength, modulus, tear strength, hardness, and rebound resilience. It is observed that compression set, abrasion loss, cross-link density, and shear modulus increased, while rebound resilience and swelling ratio values decreased with increasing MS loading. Mechanical properties of the NR composite filled with 10-μm MS are higher than those of NR composites containing 20- and 75-μm MS. The effect of thermal aging at 70°C and 100°C for 96 h has also been studied. Conclusions: This study has thus shown that MS from marble processing industrial waste can be used as economical alternative filler in NR compounding.