Review on sustainable, eco-friendly novel reinforcing fillers for rubber composites

Purpose This review aims to present the problems facing the rubber industry, including a shortage of raw materials such as fillers and ways to overcome them by finding renewable, environmentally friendly natural alternatives that can be used as fillers in the rubber industry, with the aim of preserving the environment from pollution and reducing the cost of products. This research also presents new varieties of eco-friendly and renewable fillers for rubber composites including agricultural waste, biochar and biofiller and also presents methods of treating them to improve the mechanical properties of the composites. Design/methodology/approach Agricultural waste is a sustainable energy resource that possesses various potential applications, such as its utilization in the production of construction materials and multifunctional components for automobiles. Researchers have focused on how to channel agricultural waste fibers into valuable materials while preserving environmental and human health by considering their potential for industrial use. These fillers have an excellent chance to replace or supplement the current carbon black derived from petroleum or the undesirable bulky mineral fillers. To improve the efficiency of waste natural fibers in rubber composites, several types of surface treatment techniques have been investigated including alkaline treatment, silane treatment and permanganate treatment. Findings Adding 10 phr of cereal straw to natural rubber increases the tensile strength and hardness compared to blank natural rubber, as the tensile strength increased from 13.53 MPa for natural rubber to 15.3 for rubber containing 10 phr of untreated cereal straw filler and became 19.6 MPa in the case of using filler treated with peroxide. Also, tensile strength, tensile modulus and elongation at break of the kenaf fiber-filled natural rubber composites are higher for composites with silane coupling agent. The utilization of sustainable biofillers as reinforcement in rubber composites has shown promising results in enhancing the performance of tires and other rubber products. Originality/value This review presents a new approach to evaluating the effect of using eco-friendly and sustainable reinforcing fillers for the rubber industry to preserve the environment and reduce production costs.