Reactivity of Bis[3-(triethoxysilyl)propyl] Tetrasulfide (TESPT) Silane Coupling Agent over Hydrated Silica: Operando IR Spectroscopy and Chemometrics Study

Abstract

The presence of physisorbed water during the silanization of silica is well-known for strongly influencing the silane reactivity at the interface. In this work, the reactivity of bis [3-(triethoxysilyl)propyl] tetrasulfide (TESPT), widely used in the rubber industry, on hydrated precipitation silica was investigated by time-resolved operando FTIR spectroscopy and chemometrics. The predominating reaction scheme is elucidated in conditions representative of industrial mixing process at the molecular scale. Based on multivariate curve resolution analysis and a quantitative kinetic model, it is shown that TESPT chemisorption is governed by two competitive reaction routes both producing only ethanol in the gas phase: (i) direct grafting reaction between an ethoxy moiety and a silica surface silanol and (ii) silane hydrolysis followed by co-condensation with a vicinal silane species. Reactions involving silanol−silanol condensation with production of water were not found to be significant. Although several types of water coexist on hydrated silica surface, it is demonstrated that strongly adsorbed monolayer water (E a = 44 ± 2 kJ mol −1 ), which represents ∼5% w/w of the physisorbed water, is of primary importance in the hydrolysis reaction. Its relative surface concentration with respect to the amount of physisorbed silane is strongly correlated to the final ratio between co-condensation and grafting.

Enhancement of the Mechanical Properties of a Zeolite Based Composite Coating on an Aluminum Substrate by Silane Matrix Modification

“…In particular peaks at higher wavelengths are related to methyl groups, instead the peaks at lower wavelengths are related to methylene groups 46,47 . A second less relevant peak was observed at 1420-1380 cm -1 , due to bending of these bonds 48 .…”

Application of operando spectroscopy on catalytic reactions

“…To date, several spectroscopic systems, such as Raman [8*-14], UV [15][16][17][18][19], Infrared spectra [20][21][22][23][24], XRD [25*-28], X-ray adsorption [29][30][31][32][33] etc. have already been reassembled and operated under operando conditions with the advances on instruments.…”

Effects of Zinc-Free Processing Aids on Silica-Reinforced Tread Compounds for Green Tires

“…Silane coupling agents have been used to modify the surface of silica particles to enhance rubber-filler interactions. These include TESPT (bis(triethoxysilylpropyl)tetrasulfide) and TESPD (bis(triethoxysilylpropyl)disulfide), which, due to their bifunctional characteristics, act as chemical bonding agents between the rubber matrix and silica during vulcanization [15][16][17].…”