Enhancing Eco-Friendly Natural Rubber Composites through the Incorporation of Spent Coffee Grounds

Abstract

Abstract This research aimed to enhance the physical properties of natural rubber (NR) by incorporating spent coffee grounds (SCGs) as a filler. SEM analysis displayed embedded and evenly dispersed SCG particles in the NR matrix, without any interaction due to the use of unmodified SCG particles. The addition of SCG resulted in a notable increase of up to 49.90 (~ 19% increment compared to unmodified sample) in Shore-A hardness of the composite material; however, the tensile strength and tear strength showed a decline with increasing SCG fraction. Optimal tear strength was achieved with 10 phr of SCG, attributed to the appropriate fraction and uniform dispersion of SCG in the NR matrix. The 300% modulus remained unaffected, indicating no chemical bonding between SCG and NR particles. The study also explored the odor of composites. Odor absorption efficiency (CO2 reduction) peaked at 2% compared to various SCG fractions (0–25 phr), and the highest increment of 69.2% in CO2 absorption observed at 25 phr compared to unmodified sample. Additionally, due to the unmodified surface of SCG influenced scorch and cure time when SCG content increased up to 20 phr. Scorch time increased (2.12% at 1 phr to 23.40% at 20 phr), and the cure time improved (3.12% at 1 phr to 76.82% at 20 phr).