Antioxidant Effects of the Blend of Garlic and Tmq on the Vulcanisate Properties of Natural Rubber

Natural rubber (NR) is essential across various industries due to its excellent mechanical properties; however, its service life is significantly limited by its inherent susceptibility to environmental degradation, particularly oxidation and thermal aging. Although traditional synthetic antioxidants like TMQ are effective, they pose serious environmental risks. This study addresses a critical research gap by proposing and evaluating a novel, eco-friendly hybrid antioxidant system: a combination of garlic (Allium sativum) and 2,2,4-Trimethyl-1,2-dihydroquinoline (TMQ). Garlic, rich in organosulfur compounds such as allicin, offers immediate free radical scavenging activity, while TMQ provides proven long-term oxidative stability. To evaluate the effectiveness of the garlic-TMQ blend, various formulations with different ratios were prepared and tested for their influence on the vulcanizate properties of NR. The investigation focused on hardness and abrasion resistance, both before and after accelerated thermal aging. Phytochemical analysis confirmed the presence of potent antioxidant compounds in garlic-including flavonoids, cardiac glycosides, and steroids-which enhance its antioxidative potential. The results demonstrated the blend's superior protective capability. A formulation containing 1.5 phr garlic and 7.5 phr TMQ exhibited the lowest abrasion loss (2.08%) prior to aging. A balanced 4.5 phr garlic and 4.5 phr TMQ formulation showed only a 12.8% increase in abrasion loss post-aging, maintaining excellent wear resistance (4.93%). Hardness retention was also significantly improved, with the same balanced blend exhibiting only a 3.9% decrease after aging. This study provides compelling evidence of the synergistic effect of the garlic-TMQ hybrid system, enhancing both short-term mechanical durability and long-term thermal stability. It presents a sustainable and effective approach to improving the performance of natural rubber, contributing to the advancement of environmentally friendly rubber materials.