Sustainable Reinforcement for Rubbers─Potential Application of Recycled Carbon Fibers

This study shows the utilization of recycled carbon fibers (rCF) in nitrile butadiene rubber (NBR) to produce sustainable, high-performance elastomer-based mixtures. Recycled carbon fibers, sourced from composite waste, were incorporated into the NBR matrix with different concentrations using an internal mixer for compounding and hot pressing for vulcanization. Tensile, hardness, tear and abrasion tests, and a scanning electron microscopy study were performed to show the effects of rCF. The results indicate that moderate fiber contents significantly enhance the stiffness and tensile strength of NBR without compromising its inherent elasticity. Twenty phr recycled carbon fiber increased tensile strength by 15% but decreased strain by 16% and almost doubled stiffness compared to the reference. The addition of carbon fibers caused an increase in hardness proportionally with the amount of reinforcement. 50 phr rCF increased Shore A hardness by 30%. When rCF was added, abrasion resistance increased significantly; 10 phr carbon fiber halved the amount of abraded material. Microscopic examinations confirmed the significance of fiber dispersion and adequate bonding at the matrix–fiber interface for optimal load transfer. The possibility of foaming was analyzed, and the hypothesis was proved. The results demonstrate the viability of recycled carbon fibers as a reinforcement in NBR, which also highlight the environmental and economic benefits associated with recycling composite materials in the rubber industry.