Rubber is a typical viscoelastic material and is very easy to handle, as two different properties can be adjusted for elasticity (energy storage) and viscosity (energy loss) according to purpose. Rheology treats this viscoelastic property academically. The mechanical properties of solids such as crosslinked rubber are quantified by viscoelastic measurements. Viscoelastic behavior indicates mechanical properties and indicates the effects of molecular motion and molecular structure. This measuring device is called a rheometer. This section describes the measurement method using a rheometer and examples of evaluation of various rubber materials.
Addition method of silane coupling agent (SCA) to improve the water absorption and mechanical strength of silica particle-filled epoxy resin was investigated. Two addition methods were compared, a pre-treatment method and an integral blend method in which all components were mixed simultaneously. Bonding, hydrocarbon and fluorocarbon type SCAs were employed. The bonding type has glycidoxy or amino groups that react with epoxy resin, whereas the other types have only hydrophobic chains. The silica particle-content was in the range from 10 to 50 wt%. The integral blend method was determined to be superior to the pre-treatment method for both water absorption and mechanical strength, which was contrary to the conventional view. The effect of water absorption was consequently lowered in the order of hydrocarbon > bonding types. The fluorocarbon type SCA was also effective at low silica content. Modification of the epoxy phase by SCA addition was clarified to have a more dominant effect than the adhesion of silica/epoxy interface for the lowering of water absorption, whereas it had been conventionally considered that interfacial adhesion had a more dominant effect. The mechanical strength was higher for the bonding type than the other type.
Diffusion, permeation and swelling are the mixing processes of materials. Diffusion is a mixing process of solute and solvent, permeation is a mixing process of liquid and porous media, and swelling of a gel is a mixing process of polymer network and solvent. Here the dynamics of such phenomena is discussed from a general principle called Onsager principle. Onsager principle is a general principle working in many non-equilibrium systems, and the governing equations for diffusion and swelling are derived from this principle.
The present article deals with the structural characteristics and synthetic methods of rotaxanes, polyrotaxanes, and polyrotaxane networks having cyclodextrin and crown ether as the wheel components, following to the description of the importance of the rotaxane cross-links in the light of stimuli-responsive polymer materials. The formation of rotaxane structure usually requires the enthalpy gain capable of compensating the entropy loss arising from the assembly of the rotaxane components. In particular, the structures and synthetic methods of rotaxane-crosslinked polymers are discussed from viewpoints of controllability of the cross-link density and versatility of the matrix polymers.