# Influence of Jojoba seed waste and carbon black hybrid filler on styrene butadiene rubber composites characteristics

## TL;DR

This study explores how mixing jojoba seed waste with carbon black affects the properties of rubber composites, showing trade-offs between flexibility and strength.

## Contribution

The novelty lies in using jojoba seed waste as a hybrid filler with carbon black to modify styrene butadiene rubber composites.

## Key findings

- Higher jojoba seed content reduces viscosity and scorch time but lowers tensile strength and hardness.
- Seed content increases water uptake due to the hydrophilic nature of the hybrid filler.
- Increased seed concentration improves insulating properties by reducing dielectric permittivity and conductivity.

## Abstract

This study investigates the effects of jojoba seed waste /carbon black hybrid filler on the mechanical, dielectric, and viscoelastic properties of styrene butadiene rubber composites. The ratios of the seed to carbon black are 0/50, 10/40, 20/30, 30/20, 40/10, and 50/0 phr, respectively. The study evaluates rheometric characteristics and mechanical properties, specifically tensile strength, elongation, and modulus at 100% elongation, both before and after thermo-oxidative aging at 90 °C for various periods of two, four, and six days. Further assessments involved hardness, swelling behavior, crosslink density, and water uptake as well. Moreover, Fourier transform infrared spectroscopy was used to characterize the chemical composition of the samples, while field emission scanning electron microscopy was used to evaluate the surface morphology. The results demonstrate that, increasing the ratio of jojoba seed leads to decreased viscosity and scorch time, improved elongation, and reduced tensile strength, modulus, and hardness. Filler agglomeration alters crosslinking, mechanical characteristics, and aging resistance. Measurements of water uptake demonstrated a positive correlation with seed content, ascribed to the hydrophilic characteristics of the hybrid filler. The dielectric study indicated that increased seed concentration led to a reduction in dielectric permittivity and electrical conductivity, implying enhanced insulating properties. Dynamic mechanical analysis revealed decreases in storage modulus E′ and damping factor tan δ, indicative of enhanced molecular mobility and a reduced glass transition temperature Tg, consistent with increased to the plasticizing influence of residual jojoba oil. In addition, viscosity-related parameters exhibited similar trends, signifying increased flexibility throughout the temperature spectrum. These findings highlight the trade-offs between flexibility and stiffness, allowing composite qualities to be tuned for a wide range of applications.

The online version contains supplementary material available at 10.1038/s41598-025-21649-4.