Elasticity, rubber-like

Polyurethane adhesives are formed by the reaction of various types of isoeyanates with polyols. The polar urethane group enables adhesion to various surfaees. Depending on the raw materials, glue lines with rubber-like elastic to brittle-hard behavior ean be aehieved. The presence of reactive terminal groups provides a ehemieally hardened adhesive. When polymerized to a high enough molecular weight, the adhesive ean be physically rather than chemically hardened, i.e. a hot melt. 

Rubber-like elasticity that a rigid plastic displays caused by elevated temperatures. 

In recent years PETN sheet explosive, consisting of PETN in a rubber-like elastic matrix, has found considerable use in metal-forming, metalcladding and metal-hardening. Physical expl characteristics of rubber-bonded sheet expl are described by W. Kegler R. Schall (Ref 45, p 496), by Kegler (Ref 59), and in Refs 30c,... 

Mark, J. E. The Use of Model Polymer Networks to Elucidate Molecular Aspects of Rubber like Elasticity. Vol. 44, pp. 1-26. 

It is also possible to estimate the cross-link density from the stress-strain data, using the statistical theory of rubber-like elasticity [47,58]. For a swollen rubber the relationship is... 

The ratios of mean-squared dimensions appearing in Equation (13) are microscopic quantities. To express the elastic free energy of a network in terms of the macroscopic (laboratory) state of deformation, an assumption has to be made to relate microscopic chain dimensions to macroscopic deformation. Their relation to macroscopic deformations imposed on the network has been a main area of research in the area of rubber-like elasticity. Several models have been proposed for this purpose, which are discussed in the following sections. Before that, however, we describe the macroscopic deformation, stress, and the modulus of a network. 

These Monte Carlo distributions can be used in the standard three-chain model for rubber-like elasticity to generate, for example, stress-strain isotherms [5]. Non-Gaussian effects can cause large increases in modulus at high... 

J.E. Mark and B. Erman, Molecular aspects of rubber-like elasticity. In R.F.T. Stepto (Ed.), Polymer Networks, Blackie Academic, Chapman Hall, Glasgow, 1998. 

Hu, Y. and Mackenzie J.D. (1992) Rubber-like elasticity of organically modified silicates. Journal of Materials Science, 27, 4415 1420. 

Polymer that displays rubber-like elasticity. 

Gummidynamit. A German rubber-like, elastic mass obtd by dissolving Collod Cotton in NG. Its compn is similar to Sprenggelatine (Blasting Gelatin)... 

It has been recognised for several decades that most of the characteristic properties of polymers (except the untypical globular proteins), such as their high solution and melt viscosities, their rubber-like elasticity, and their viscoelastic behaviour generally, can be ascribed to the fact that their molecules, unless constrained as in the crystal, are free to adopt extended but coiled configurations, so that each molecule affects a region of space of many times its own volume ... 

For long chains, the modulus at about 106-107 dynes/cm2 passes into a domain of much slower relaxation (the plateau region). The width of the plateau depends strongly on molecular weight, while the characteristic modulus of the plateau region G is independent of molecular weight. The presence of the plateau confers rubber-like elastic properties over an intermediate range of frequencies or times. 

The molecular movements of the chain determine the elastic range of polymers. In this unique state of rubber like elasticity there is freedom of the micro-Brownian motion of the chain units and a high relaxation time for the macro-Brownian motion of the entire chain. This state can be described as a liquid with a fixed structure U6). 

Mark, J.E. Erman, B. Rubber-like Elasticity. A Molecular Primer, Wiley-Interscience New York, 1988. 

Flory [3] formalized the equation of state for equilibrium swelling of gels. It consists of four terms the term of rubber-like elasticity, the term of mixing entropy, the term of polymer solvent interaction and the term of osmotic pressure due to free counter ions. Therefore, the gel volume is strongly influenced by temperature, the kind of solvent, free ion concentrations and the degree of dissociation of groups on polymer chains. 

Elastomers. Elastomer is a generic name for polymers that exhibit rubber-like elasticity. Elastomers are soft yet sufficiently elastic that they can usually be stretched several hundred percent under tension. When the stretching force is removed, they quickly retract and recover their original dimensions. 

A good operational definition of rubber-like elasticity is high deformability with essentially complete recoverability.81 84 The high deformability can be remarkably high, with some rubbery materials extending up to 15 times their original lengths. 

The gelation process that leads to the network structures required for rubber-like elasticity have been extensively studied, by experiments, theory, and simulations.245-249 In some case, the gelation can be made to be reversible.250... 

Priss LS (1981) Molecular origin of constants in the theory of rubber-like elasticity considering network chains steric interactions. J Pure Appl Chem 53 1581-1596 Priss LS, Gamlitski YuA (1983) Mechanism of conformation transitions in polymer chains. Polym Sci USSR 25 117-123... 

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