Mechanical reinforcement in magadiite/styrene‐butadiene rubber composites

Abstract

This work investigates mechanical properties of styrene-butadiene rubber (SBR) composites incorporating magadiite (MGD), a synthetic layered silicate (Na 2 Si 14 O 29 Á9H 2 O) with surface chemistry similar to precipitated silica used in tire tread formulations. Treatment with cetyltrimethylammonium (CTA 1 ) expands the MGD layers and makes the interlayer face surfaces accessible to sulfur-functional silane TESPT (Si69) and SBR, primarily during batch mixing. DMA and tensile testing of cured CMGD/SBR composites show that CTA-treated MGD (CMGD) provides substantially higher levels of mechanical reinforcement than equivalent amounts of silica. However, CMGD/SBR composites exhibit larger loss tangent values above T g , probably due to lower SBR-SBR crosslink density resulting from interlayer trapping of sulfur released by Si69 during vulcanization. DMA and tensile testing also demonstrate Si69's critical role in forming MGD-SBR graft sites essential to mechanical reinforcement. Replacing silica with CMGD reduces composite weight without sacrificing tensile modulus, suggesting that use of CMGD in tire rubber formulations could improve vehicle energy efficiency.

The role of interlayer grafting on the mechanical properties of magadiite/styrene‐butadiene rubber composites

“…Na‐MGD was cation‐exchanged in an aqueous suspension containing 1.16 mmol cetyltrimethyl ammonium (CTA + ) per gram of Na‐MGD, resulting in uniform exchange of CTA + for Na + as reported previously and references cited therein. Cetyltrimethyl ammonium bromide (CTAB, Sigma‐Aldrich) was used as received.…”

“…However, neither of these studies fully explored the impact of silane‐mediated MGD‐SBR crosslinks on composite mechanical properties. Omission of Si69 from the CMGD/SBR formulation correlates with decreased rubbery storage moduli, tensile moduli, and toughness . This could be due to the absence of Si69‐mediated MGD‐SBR crosslinks, or it could simply be the result of decreased sulfur content.…”

“…Since its commercialization nearly 25 years ago, tire treads incorporating silane‐modified silica have achieved simultaneous improvements in rolling resistance, wet traction, and wear resistance . To further “stretch tires' magic triangle,” we have investigated the use of a layered silicate, magadiite (MGD), as a candidate active filler in styrene‐butadiene rubber composites . In contrast with well‐studied clay mineral fillers like montmorillonite, the face surfaces of MGD platelets have a high density of silanol groups that can react with bifunctional silanes.…”

“…We started to explore this hypothesis in two recent publications . The first study showed that MGD pretreated with cetyltrimethylammonium (CTA + ) expands the MGD layers and makes the interlayer face surfaces accessible to sulfur‐functional silane TESPT (Si69) and SBR, primarily during batch mixing.…”

“…We started to explore this hypothesis in two recent publications . The first study showed that MGD pretreated with cetyltrimethylammonium (CTA + ) expands the MGD layers and makes the interlayer face surfaces accessible to sulfur‐functional silane TESPT (Si69) and SBR, primarily during batch mixing. Styrene‐butadiene rubber (SBR) composites incorporating CTA‐treated MGD (CMGD) manifested significantly higher levels of mechanical reinforcement than silica/SBR composites with the same level of inorganic filler loading.…”