Biobased poly(butadiene‐ co ‐myrcene) elastomers reinforced with treated sargassum: tailoring filler–rubber interactions through myrcene content

Poly(butadiene‐ co ‐myrcene) elastomeric composites were developed using treated sargassum particles as a bio‐filler (TS), while maintaining constant low silica and silane loadings. This dual marine‐ and plant‐derived design simultaneously valorizes β ‐myrcene as a plant‐derived comonomer and invasive sargassum biomass as a marine‐derived filler. The effects of myrcene composition and TS loading on vulcanization behavior, filler‐network response, morphology, mechanical properties, crosslink density, thermal stability, and viscoelastic behavior were investigated. Increasing myrcene content generally reduced rheometric torque, cure rate, crosslink density, hardness, and stiffness, while prolonging scorch and optimum cure times and increasing network extensibility. The effect of TS on cure kinetics depended on rubber composition and filler loading and was accompanied by increased reversion relative to the corresponding references without TS. Payne effect analysis showed a lower strain‐dependent filler‐network contribution with increasing myrcene composition, although changes in matrix stiffness and crosslink density also contributed to this response. Dynamic mechanical analysis showed that TS increased storage modulus in the biobased rubber composites with TS at appropriate loadings without substantial changes in glass transition temperature. TS also increased Young's modulus, hardness, and elongation at break, but did not systematically improve tensile strength and reduced crosslink density at higher myrcene compositions and TS loadings. Scanning electron microscopy indicated adequate physical contact at moderate TS loading but not conclusive evidence of improved filler dispersion. Overall, β ‐myrcene composition and TS loading provide complementary methods for modifying the stiffness, extensibility, filler‐network response, and viscoelastic behavior of these biobased rubber composites.