# Insight on the impact of Acacia nilotica leaves extract on the characteristics of natural and synthetic rubber composites

## TL;DR

This study shows that Acacia nilotica leaf extract can act as a sustainable antioxidant in rubber composites, improving their resistance to aging.

## Contribution

The study introduces Acacia nilotica leaf extract as a natural antioxidant alternative to TMQ in rubber composites.

## Key findings

- Acacia extract significantly improves aging resistance in both natural and synthetic rubber composites.
- At 0.5 phr, the extract outperforms TMQ in preserving tensile strength during aging in natural rubber.
- In synthetic rubber, the extract at 0.5–1 phr improves tensile strength and elongation at break better than TMQ.

## Abstract

The purpose of this study is to assess the extract of Acacia nilotica leaves as a sustainable natural antioxidant for natural rubber (NR) and styrene-butadiene rubber (SBR) composites. The Acacia extract was incorporated to NR and SBR at concentrations from 0.5 to 2 phr, and its effectiveness was compared to that of commercial antioxidant polymerized 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ). Rubber compositions were evaluated for chemical interactions and dispersion using FTIR and FESEM, and curing behavior was realized by rheometric studies. Physico-mechanical characteristics were assessed prior to and following thermo-oxidative aging at 90°Cfor different periods (2, 4, 6, and 7 days). The findings show that in both rubber matrices, theAcacia extract significantly improves aging resistance. While greater loadings (≥ 1 phr) negatively impacted initial strength without further improving aging resistance in comparison to TMQ. NR composites demonstrated an optimal antioxidant performance at 0.5 phr, offering superior retention of tensile strength during aging. At ideal concentrations of 0.5–1 phr, the extract dramatically increased tensile strength and elongation at break in SBR composites, exceeding TMQ in preventing excessive modulus expansion during aging. These results validate the potential of Acacia extractas an environmentally friendly antioxidant for rubber applications, especially in automotive, sealing, and vibration-damping components where improved durability and sustainable material solutions are needed.

The online version contains supplementary material available at 10.1038/s41598-026-40512-8.