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Mechanistic aspects of silane coupling agents with different functionalities on reinforcement of silica‐filled natural rubber compounds
Author(s) -
Kaewsakul Wisut,
Sahakaro Kannika,
Dierkes Wilma K.,
Noordermeer Jacques W.M.
Publication year - 2015
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.23949
Subject(s) - silane , silanes , natural rubber , materials science , vulcanization , alkoxy group , moiety , silanization , sulfur , filler (materials) , polymer chemistry , composite material , chemical engineering , organic chemistry , chemistry , alkyl , engineering , metallurgy
Silane coupling agents containing different specific functionalities are studied to gain understanding of their roles in silica‐filled natural rubber (NR) compounds. Five different silane coupling agents, that is bis ‐(triethoxysilylpropyl) tetrasulfide (TESPT), bis ‐(triethoxysilylpropyl) disulfide (TESPD), octyltriethoxysilane, vinyltrimethoxysilane, and bis ‐(trimethyl‐silylmethyl) tetrasulfide (TMSMT), are comparatively investigated, by taking the most commonly used TESPT as a reference. The results reveal that alkoxy‐based silanes can effectively reduce the filler–filler interaction and lower compound viscosity owing to the effect of silane‐to‐silica hydrophobation which contributes to better compatibility between silica and NR. The alkoxy‐silanes with a sulfur moiety, that is TESPT and TESPD, show more pronounced improvement in overall properties as a result of filler–rubber interactions. The use of TMSMT which has no alkoxy groups but contains only a sulfur moiety elucidates that there are three reaction mechanisms involved in systems with sulfur‐alkoxy‐based silane. These are as follows: (1) the silane‐to‐silica or silanization/hydrophobation reaction; (2) the silane‐to‐rubber or coupling reaction; and (3) rubber–rubber crosslinking originating from active sulfur released by the polysulfide‐based silane TESPT. These simultaneous reactions are temperature dependent, and show an optimum level at a dump temperature of approximately 140–150°C, as depicted by filler–filler and filler–rubber interactions, as well as mechanical properties of such compounds. POLYM. ENG. SCI., 55:836–842, 2015. © 2014 Society of Plastics Engineers