In recent years, the escalating concerns regarding environmental sustainability and the need for greener alternatives in various industries have stimulated a growing interest in the development of ecologically friendly materials. Natural rubber (NR) based composites have received a lot of interest because of their renewability, biodegradability, and promise to reduce the environmental effect of traditional synthetic rubber composites [1]. To further enhance the eco-friendliness of these NR composites, researchers have explored the incorporation of various waste materials as potential fillers. The use of environmentally friendly materials and fillers, particularly natural polymers, and natural fillers, as part of polymeric composites. Natural fillers such as plastic and natural filler composites [1–13] and rubber filled with natural fillers [14–22] have been used as reinforcing fillers in many works because they are inexpensive as well as environmentally friendly. One such waste material with promising potential is spent coffee grounds (SCGs).
SCG has many advantages for improving the properties of polymer compounds, for example, it is an eco-friendly reinforcing agent that is renewable, lightweight, biodegradable, and low risk. Moreover, it is well known that natural fiber has a high polarity and plastic substrate has a low polarity, as a result, they are incompatible and thus affect the performance of composites [1]. SCG is difficult to get rid of because it needs high oxygen to decompose, and the decomposition process tends to release pollution, such as residues of caffeine, tannin, and polyphenol contaminants [8]. SCG is mainly made up of neutral detergent fiber, which contains hemicellulose, lignin, and cellulose compounds, and acid detergent fiber, which is composed of cellulose and lignin [23]. There are many works that focus on using SCG to strengthen the mechanical characteristics of polymers by incorporating them to produce sustainable green composites at an affordable cost [24–26].
The use of naturally available fillers in NR based composites has been widely investigated, as they can impart unique properties and characteristics to the resulting materials. SCGs possess several attractive attributes that make them potentially suitable as a filler in NR composites. Firstly, SCGs are abundant and easily accessible waste materials, making them a cost-effective and sustainable filler option. Secondly, SCGs are rich in natural compounds such as cellulose, hemicellulose, lignin, and polyphenols, which can potentially interact with the NR matrix, leading to improved mechanical properties and other beneficial effects. Moreover, the inherent porosity and surface structure of SCGs may contribute to enhanced interfacial bonding with NR, thereby influencing the overall performance of the composites.
Despite these promising attributes, limited research has been conducted to explore the use of SCGs in NR composites comprehensively. Previous studies have primarily focused on other waste materials such as fillers in rubber composites, leaving a gap in understanding the potential of SCGs in this context.
In this research study, we investigate the potential of incorporating (fraction ranging from 0–25 phr) spent coffee grounds (SCGs) into eco-friendly natural rubber composites. The preparation of the composites involved compounding and mixing the rubber matrix with SCGs using a two-roll mill, followed by vulcanization of the compounded mixture through hot compression molding. The microstructure and morphology of composites were examined using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Furthermore, the mechanical properties of the composites were evaluated through Tensile tests and hardness Shore-A measurements, while an odor absorption test was conducted to assess the composite's potential in odor control applications. The comprehensive analysis of these properties and characteristics will give useful insights regarding the suitability and effectiveness of SCGs as a sustainable filler in NR composites, contributing to the growing body of knowledge on eco-friendly materials in various industrial applications.