The static friction of compliant elastomers has proven important for industrial applications, including seals, and grips on tools and sports equipment. The design of load-dependent contact state may provide characteristic load-dependent frictional properties beyond that found on conventional rubber surfaces. Here we investigate the static friction, over a wide range of normal loads, between a flat glass surface and polyester meshes adhered on an elastomer surface. At low load the glass is supported only by the mesh members and the static friction is low. As normal load increases, the mesh members tend to dent into the elastomer and at the pore of the mesh the elastomer surface may make contact with the glass. The newly created contact with the elastomer makes the static friction increase with the higher friction coefficient. By tuning the structures, e.g., the aperture ratio, of meshes, we can extend the monotonic load-dependency of static friction of rubbers into the highly nonlinear range.

There are a lot of functional surfaces in nature, for example, a superhydrophobic surface of lotus leaves. Although there have been various artificial superhydrophobic surfaces, those are difficult to use in daily purposes because those have been built on brittle, stiff and breakable materials. In this report, we have focused on durable hydrophobic material of a vulcanized rubber, and attempted to prepare durable superhydrophobic surfaces by forming micro-structures on rubber surfaces. The surface micro-structured silicon molds were prepared by common lithographical techniques. Unvulcanized rubber was put on the silicon molds, and then pressed and vulcanized at 180 °C for 10 min. After peeling off from the silicon mold, vulcanized rubber surfaces were observed by field emission scanning electron microscope. Water contact angles and sliding angles on the vulcanized rubber surfaces were analyzed with 1.5 µL purified water droplets. As the results, micro pincushion arrays were successfully formed on the surfaces of the vulcanized rubbers with quite small defect and those surfaces showed superhydrophobicity. Furthermore, the structure of the micro pincushion arrays was not damaged by multiple elongations. The sliding angles were decreased with increasing degree of stretching of superhydrophobic micro-structured rubbers.

This review summarizes the development of stimuli-responsive materials based on the topology transformable polymers from branched to linear. The junction point of the rotaxane components bearing plural polymer chains is the key for the topology transformation which cannot be attained by the fixed junction point formed by the covalent bond. Crown ether-containing macromolecular [2]rotaxane with both ammonium and urethane moieties (M2R) as the stations for the crown ether wheel on the axle polymer chain produces the controllable and movable junction point of the polymer chains via the control of the component interaction, which enables the construction of sophisticated dynamic polymer systems. The rotaxane-linked star polymers with a fixed rotaxane linkage owing to the ammonium/crown ether interaction were synthesized by the introduction of two additional polymer chains to the components of M2R. The star polymers altered their topology to linear by the N-acetylation of the ammonium moiety, which broke the ammonium/crown ether interaction and generated the urethane/crown ether interaction to move the wheel component to the polymer chain terminal, eventually affording the linear polymer. The change in physical property caused by the topology transformation was confirmed in hydrodynamic volume and viscosity, demonstrating an effective way to the development of novel stimuli-responsive materials.

The frictional properties of rubber when rubbed against the dry glass surface, water lubricated surface, and ice are shown. Especially the mechanisms of friction for natural rubber (NR), butadiene rubber (BR), and NR-BR blends are discussed when they are rubbed against ice under various temperatures and contact pressures.

The rubber-brass adhesion is influenced by the chemical composition and thickness of interfacial layer. The adhesion build-up mechanism involves the chemical reaction of the rubber skim compound and copper of the brass coating, forming Cu_xS, ZnS and ZnO layers at the rubber-brass interface.
All factors which affect the reactivity of a brass surface for Cu_xS formation, have an effect on the adhesion but excessive Cu_xS leads to the loss of adhesion. The adhesion force tends to maximum value with optimum copper content in the plating but better retention of after aging achieves at a lower copper content.
A higher sulfur content is necessary than for ordinary rubber. There is an optimum amount of organic acid cobalt salt, as adhesion diminishes when the rubber is formulated with large amounts.
A high level of unaged adhesion can be obtained if products with a combination of low cobalt and high sulfur content are formed on the brass surface.