A NOVEL SBS COMPOUND VIA BLENDING WITH PS-B-PMBL DIBLOCK COPOLYMER FOR ENHANCED MECHANICAL PROPERTIES
Styrene–butadiene–styrene (SBS) rubbers are one of the most frequently used thermoplastic elastomers globally. The upper operating temperature of SBS is limited by the glass transition temperature (Tg) of poly(styrene) (PS), 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 Tg of 195 °C. Notably, α-MBL, also recognized as Tulipalin A, is a biorenewable compound naturally found in tulips. This investigation encompasses both crosslinked and noncrosslinked blends of poly(styrene)-block-poly(α-methylene-γ-butyrolactone) diblock copolymer (PS-b-PMBL) and poly(styrene)-block-poly(butadiene)-block-poly(styrene) triblock copolymer, within the 0–20 wt% PS-b-PMBL range. Thorough examination using 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 with noncrosslinked blends. For noncrosslinked blends, an increase in strength is observed while maintaining commendable rubbery properties. Notably, the noncrosslinked blends permit the recycling of components (SBS and PS-b-PMBL) through the redissolving of rubber in tetrahydrofuran. These findings present a promising avenue for the enhancement of rubbers through the incorporation of biorenewable compounds.ABSTRACT
Results of DSC analysis of diblock copolymers. The heating/cooling rate was 10°C/min. The second heating ramp is presented here.
(A) Results of DSC analysis of SBS blends with PS1-PMBL. (B) Close-up of panel (A) of the 180–220°C region. The heating/cooling rate was 10 °C/min. The second heating cycle is here presented. The vertical dashed line in panel (B) indicates the Tg of PMBL.
Frequency spectra in terms of complex viscosity as a function of oscillation frequency for (A) SBS/PS1-PMBL, (B) SBS/PS2-PMBL, and (C) SBS/PS3-PMBL at various diblock copolymer content. The experimental temperature is 110 °C.
Frequency spectra in terms of complex viscosity as a function of oscillation frequency for SBS samples (A) PS4-PMBL, (B) PS5-PMBL, (C) PS6-PMBL with different diblock copolymer content. The experimental temperature is 110°C.
Young’s modulus as a function of the diblock copolymer content for the blends SBS/PS1-PMBL, SBS/PS2-PMBL, and SBS/PS3-PMBL. Experiments were conducted at room temperature.
Stress–strain curve of pure SBS compared with the SBS/PS5-PMBL at 15 wt%. Experiments were performed at room temperature.
Young’s modulus results for blends PS4/PS5/PS6 with the diblock copolymer weight percentage.
SEM images of SBS/PS1-PMBL blends of 5 wt% (left) and 20 wt% (right) by TLD.
GPC results of the five different PS polymers.
HNMR spectra of PS.
1H NMR analysis of diblock polymer PS(28k)-b-PMBL(32k).
GPC results for the diblock polymerizations of poly(styrene-b-α-methylene-γ-butyrolactone).
Two variants of butadiene.
1H NMR analysis of SBS from Kraton.
TGA results of SBS/PS1-PMBL blend.
Comparison of complex viscosity of blends PS4–PS6 at high and low angular frequencies.
Dimensions of dumbbell-like molds. Crosslinked blends have a thickness of 1 mm and noncrosslinked blends have a thickness of 4 mm.
Break point (bars) and elongation (line + symbol) of SBS/PS1-PMBL.
Break point (bars) and elongation (line + symbol) of SBS/PS2-PMBL.
Break point (bars) and elongation (line + symbol) of SBS/PS3-PMBL.
Break point (bars) and elongation (line + symbol) of SBS/PS4-PMBL.
Break point (bars) and elongation (line + symbol) of SBS/PS5-PMBL.
Break point (bars) and elongation (line + symbol) of SBS/PS6-PMBL.
Additional SEM image of SBS/PS1-PMBL of 5 wt% (left) and 20 wt% (right).
Contributor Notes