A novel SBS compound via blending with PS-b-PMBL diblock copolymer for enhanced mechanical properties

Abstract

Styrene-butadiene-styrene (SBS) rubbers stand as one of the most frequently employed thermoplastic elastomers globally. The upper operating temperature of SBS is limited by the glass transition temperature (Tg) of polystyrene, circa 100 °C. This study demonstrates a noteworthy enhancement in the properties of SBSs by introducing a diblock copolymer consisting of styrene and α-methylene-γ- butyrolactone (α-MBL). Polymers derived from α-MBL exhibit exceptional thermal stability, attributable to a glass transition temperature of 195 °C. Notably, α-MBL, also recognized as Tulipalin A, is a bio-renewable compound naturally found in tulips. This investigation encompasses both crosslinked and non-crosslinked blends of poly(styrene)-b-poly(α- methylene-γ-butyrolactone) diblock copolymer (PS-PMBL) and poly(styrene)-b-poly(butadiene)-b- poly(styrene) triblock copolymer, within the 0-20 wt.% PS-PMBL range. Thorough examination employing thermal analysis and linear shear rheology reveals that all blends surpass the properties of their pure SBS counterparts. Specifically, blending at 200 °C induces crosslinking between the polymers, yielding heightened Young’s modulus and complex viscosity, thereby resulting in a robust and rigid material compared to non-crosslinked blends. For non-crosslinked blends, an increase in strength is observed while maintaining commendable rubbery properties. Notably, the non-crosslinked blends permit the recycling of components (SBS and PS- PMBL) through the re-dissolving of rubber in tetrahydrofuran (THF). These findings present a promising avenue for the enhancement of rubbers through the incorporation of bio-renewable compounds.