Modification of bentonite by solution plasma treatment: Implications for reinforcement in natural rubber latex-based nanocomposites

Abstract

This study aimed to modify bentonite through the solution plasma process (SPP), with and without the silane coupling agent Si69, and investigated its performance in sulfur-prevulcanized natural rubber (SPNR) composites. X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy results showed that plasma treatment modified the bentonite surface by removing weakly bound carbon compounds, introducing oxygen-containing functional groups, and reducing the size of bentonite particles. With the presence of Si69 during plasma, the XPS results suggested the alteration of Si69 molecules with Si–O components forming complex bonding with bentonite. Thermogravimetric analysis, energy dispersive X-ray spectroscopy, and XPS results suggested that the sulfur-containing component of Si69 was physically adsorbed on bentonite. The X-ray diffraction pattern indicated that the increase in interlayer spacing resulted from the dispersion of bentonite in the ethanol/water medium rather than from the plasma treatment effect. For SPNR/bentonite nanocomposites, plasma-treated bentonite, with or without Si69, improved the tensile strength of SPNR composites because of particle size reduction and removal of weakly bound carbon compounds. Under the studied conditions, Si69 provided no added benefit beyond plasma treatment alone, as its fragmented S-containing parts were physically adsorbed onto bentonite.