The surface of water provides an excellent environment for gliding movement, in both nature and modern technology, from surface living animals such as the water strider, to LangmuirBlodgett films. The high surface tension of water keeps the contacting objects afloat, and its low viscosity enables almost frictionless sliding on the surface. Here we utilize the water surface as a nearly ideal underlying support for free-standing ultra-thin films and develop a novel tensile testing method for the precise measurement of mechanical properties of the films. In this method, namely, the pseudo free-standing tensile test, all specimen preparation and testing procedures are performed on the water surface, resulting in easy handling and almost frictionless sliding without specimen damage or substrate effects. We further utilize van der Waals adhesion for the damage-free gripping of an ultra-thin film specimen. Our approach can potentially be used to explore the mechanical properties of emerging twodimensional materials.

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Rheological behaviors in the rheographs and crosslink types of silica-filled natural rubber compounds with differing contents of silane coupling agent were investigated. Bis-(3-(triethoxysilyl)-propyl)-tetrasulfide (TESPT) was used as a silane coupling agent. In the rheographs of the silica-filled compounds containing TESPT, the local minimum torque regions after the maximum torque were observed, and the time to reach the local minimum torque was found to become faster with increase of the TESPT content. The reversion ratio, on the whole, was decreased by increasing the TESPT content. By increasing the TESPT content, the crosslink densities of the mono-, di-, and polysulfides were increased. Ratio of the polysulfides of the total crosslink density increased, while those of the monoand disulfides decreased with increase of the TESPT content. Changes of the crosslink densities after thermal aging were also investigated. The experimental results were explained with the reduction of curatives adsorbed on the silica, increase of sulfur content, and crosslink formation between the silica and rubber by adding TESPT.

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