Structure-Property Relationships of Bio-based Organic Additives in Rubber Compounding: A Systematic Review and Meta-analysis

Abstract

The growing demand for sustainable elastomeric materials has accelerated the use of bio-based organic additives as alternatives to petroleum-derived rubber compounding ingredients. Although numerous renewable additives, including vegetable oils, epoxidized oils, lignin, tannins, and cellulose derivatives, have shown promising performance, quantitative evidence linking their molecular structure to rubber properties remains limited. This study presents a systematic literature review and meta-analysis of bio-based organic additives in rubber compounding following the PRISMA 2020 guidelines. A meta-analysis of 28 studies (16 comparisons) evaluated the effects of additive chemistry, concentration, and renewable feedstocks on mechanical, thermal, curing, and durability properties. The results indicated a significant overall reduction in tensile strength (Hedges' g = −0.788, p = 0.006) with substantial heterogeneity (I² = 63.05%). Subgroup analysis showed that epoxidized oils maintained nearly neutral mechanical performance, whereas conventional vegetable oils produced significant plasticization effects. Meta-regression further revealed a significant negative relationship between additive concentration and mechanical performance. To support sustainable material selection, this review proposes the Organic Additive Performance Index (OAPI), integrating mechanical performance, thermal stability, chemical compatibility, sustainability, biodegradability, economic feasibility, and industrial applicability. The findings provide quantitative guidance for optimizing bio-based additives and advancing the development of high-performance, environmentally sustainable rubber materials.