Interfacial interaction modes construction of various functional SSBR–silica towards high filler dispersion and excellent composites performances

Abstract

In this study, various interfacial interaction modes between silica and in-chain functionalized solution styrene butadiene rubbers (F-SSBRs) with –OH (3-mercaptopropanol, MPL), –COOH (11-mercaptoundecanoic acid, MUA), and –Si–(OCH₂CH₃)₃ (3-mercaptopropyltriethoxysilane, MPTES) were constructed at the molecular level. As the modes of interfacial interaction followed the order of single hydrogen bond interactions to dual hydrogen/covalent bond interactions to single covalent bond interactions, the interfacial interactions presented silica/SSBR-g-MPL < silica/SSBR-g-MUA < silica/SSBR-g-MPTES. Moreover, the interfacial interactions were enhanced as the grafting percentages of the functional group increased. The results showed that silica dispersion was enhanced upon improving the interfacial interaction. As the filler–rubber networks improved and filler–filler networks decreased, the dynamic mechanical properties of the silica/F-SSBR composites improved and were even superior to those of the silica/SSBR/bis(γ-triethoxysilylpropyl)-tetrasulfide (Si69) composite. The rolling resistances of silica/SSBR-g-MPL, silica/SSBR-g-MUA, and silica/SSBR-g-MPTES composites decreased by 21.2%, 27.3%, and 50.8%, respectively. The wet skid resistances of silica/SSBR-g-MPL, silica/SSBR-g-MUA, and silica/SSBR-g-MPTES composites increased by 112.7%, 161.2%, and 184.3%, respectively. However, the excessively strong rubber–rubber networks led to poor mechanical properties. Filler–rubber, filler–filler, and rubber–rubber networks reached equilibrium in the silica/SSBR-g-MUA composite, which had excellent overall performances of high strength, low rolling resistance, and high wet skid resistance.