More or less universally, bis(3-triethoxysilyl propyl) tetrasulfide (TESPT) has been used as a coupling agent during dispersion of silica filler in a virgin nonpolar rubber compound. It is for the first time that TESPT has been used as a devulcanizing agent and as-grown devulcanized rubber facilitates the silica dispersion in nonpolar rubber compound without any coupling agent. Dual functionalities of TESPT have been modeled and validated in this work. Various factors like the role of sol-gel content, inherent viscosity of sol rubber, crosslink density, and degree of devulcanization were investigated as a function of devulcanization time and amount of TESPT to optimize devulcanization time and TESPT amount. To study the silica reinforcement, revulcanization of devulcanized SBR was carried out with silica filler and the curing characteristics of the material were evaluated. From the mechanical properties and thermogravimetry analysis the optimum time for devulcanization is determined. Further, scanning electron microscopy (SEM) studies were undertaken to check the coherency and homogeneity of the material. POLYM. ENG. SCI., 58:74-85, 2018.
Each
year, hundreds of millions of tires are produced and ultimately
disposed into nature. To address this serious environmental issue,
devulcanization could be one of the sustainable solutions that still
remains as one of the biggest challenges across the globe. In this
work, sulfur-vulcanized natural rubber (NR) is mechanochemically devulcanized
utilizing a silane-based tetrasulfide as a devulcanizing agent, and
subsequently, silica (SiO2)-based rubber composites are
prepared. This method not only breaks the sulfur–sulfur cross-links
but also produces reactive poly(isoprene) chains to interact with
silica. The silica natural rubber composites are prepared by replacing
30% fresh NR by devulcanized NR with varying contents of silica. The
composites exhibit excellent mechanical properties, tear strength,
abrasion resistance, and dynamic mechanical properties as compared
with the fresh natural rubber silica composites. The tensile strength
of devulcanized rubber-based silica composites is ∼20 MPa,
and the maximum elongation strain is ∼921%. The devulcanized
composites are studied in detail by chemical, mechanical, and morphological
analyses. Thus, the value added by the devulcanized rubber could attract
the attention of recycling community for its sustainable applications.
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