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The Gough–Joule effect (a.k.a. Gow–Joule effect) is originally the tendency of elastomers to contract when heated if they are under tension. Elastomers that are not under tension do not see this effect. The term is also used more generally to refer to the dependence of the temperature of any solid on the mechanical deformation. [1]
The T-V diagram of the rubber band experiment. The decrease in the temperature of the rubber band in a spontaneous process at ambient temperature can be explained using the Helmholtz free energy = where dF is the change in free energy, dL is the change in length, τ is the tension, dT is the change in temperature and S is the entropy.
An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus (E) ...
Popular Science magazine, January 1972: "A stretched piece of rubber contracts when heated. In doing so, it exerts a measurable increase in its pull. This surprising property of rubber was first observed by James Prescott Joule about a hundred years ago and is known as the Joule effect." [7]
The time–temperature superposition principle is a concept in polymer physics and in the physics of glass-forming liquids. [1] [2] [3] This superposition principle is used to determine temperature-dependent mechanical properties of linear viscoelastic materials from known properties at a reference temperature.
The engineering stress (by definition) is the first derivative of the energy in terms of the extension ratio, which is equivalent to the concept of strain: = = and the Young's Modulus is defined as derivative of the stress with respect to strain, which measures the stiffness of the rubber in laboratory experiments.
where is the vacuum permittivity, is the dielectric constant of the polymer and is the thickness of the elastomer film in the current state (during deformation). Usually, strains of DEA are in the order of 10–35%, maximum values reach 300% (the acrylic elastomer VHB 4910, commercially available from 3M, which also supports a high elastic energy density and a high electrical breakdown strength.)
Photo-crosslinking is achieved by using one wavelength of light, while a second wavelength of light reversibly cleaves the photo-crosslinked bonds. The effect achieved is that the material may be reversibly switched between an elastomer and a rigid polymer.