Elasticity, Rubber‐like

Abstract

Long, flexible polymer chains with high mobility and weak interchain interactions may be covalently linked together to form network structures. These materials exhibit a unique behavior called rubber‐like elasticity, which is high and reversible deformability (up to 10 times the original dimension). The origin of elasticity at thermodynamic equilibrium is the decrease in entropy of the chains between cross‐linking points resulting from the extension. Elastomers therefore follow thermodynamic laws similar to those for gases. There is a minor intramolecular energetic component in the retractive force which can be extracted from thermoelasticity experiments and is related to conformational energy changes of the chains. Most of the theoretical and experimental works in the field of rubber‐like elasticity have been devoted to the characterization of network structures. Molecular models based on statistical mechanics have been applied to the analysis of equilibrium properties such as stress–strain measurements in uniaxial extension and swelling by a solvent. The real behavior of rubbers is between the predictions of the simple affine and phantom models and is well represented by molecular models which include entanglement constraints. These models associated with topological descriptions of networks are powerful tools to describe network structures.

Hierarchical Polymerized High Internal Phase Emulsions Synthesized from Surfactant-Stabilized Emulsion Templates

“…The code was specifically designed to solve 2D plane strain problems with periodic boundary conditions for a mesh of individual units that make up the pore structures derived earlier. An average Young’s modulus of 3.2 GPa and Poisson’s ratio of 0.33, both values extracted from the literature for (bulk) cross-linked polystyrene, , were used as input parameters for polymer properties. Using the FEM, small periodic compressive displacements were applied to the top edge of each unit, keeping the bottom edge fixed in the vertical direction.…”

Orientational effect of mica in fumed silica reinforced composites

“…A plot of the reduced stress [σ*] = σ/(α 2 − α −1 ) against α −1 , as suggested by the Mooney–Rivlin equation12, 13 in which 2 C 1 and 2 C 2 are constants independent of α, are reported, as an example, in Figure 4 for the sample containing only silica and that containing 2 phr of unsilanized mica. Both curves exhibit some features that are specific of filled elastomers: (1) at low deformations, a decrease in the modulus attributed to the Payne effect,14, 15 and (2) at high deformations, an upturn in the modulus due to limited chain extensibility.…”