Gough Joule effect

In 1805, Gough discovered that a rubber shrinks when heated under a constant load. The rubber was restored to its initial length when cooled down, which showed that the change was thermoreversible. Contraction of a rubber by heat was confirmed in detail by 

4 (a) Magnification of the small deformation region. Thermoelastic inversion is seen around 

as indicated hy the thin broken line, (b) Temperature rise (depression) by adiabatic elongation (contraction) of a rubber. 

Joule in 1859, and hence it is called the Gough-Joule effect. The Gough-Joule effect suggests that the temperature coefficient of tension is positive. 

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Gough-Joule effect When an elastomer/ rubber is stretched adiabatically (without heat entering or leaving the system), heat is evolved, This effect was first reported discovered by Gough in 1805 and rediscovered by Joule in 1859. 

The fact that mbber shows mbber elasticity was discovered more than 100 years earlier than professor H. Staudinger s proposal. The memory effect acquired by vulcanization, so-called Gough-Joule effect, and its thermodynamic explanation were the great achievements in the nineteenth century. As seen in many textbooks, this thermodynamic approach was the easiest one to gain consistency between ever-performed experiments and theory. In fact, thermodynamics of mbbery material can be treated in parallel with thermodynamics of gas. One could show experimentally that... 

An apparatus which demonstrates the Gough-Joule effect. It comprises a pendulum adjusted so that a rubber sample is under stretch. Heat from a lamp causes the rubber to contract and swing the pendulum. This pulls the rubber into a shaded section where it extends and moves the pendulum back to the original position, whereupon the cycle is repeated. 

The Gough Joule effect, shown as an increase in modulus with an increase in temperature and the retraction of stressed rubber on heating An ability of some elastomers to undergo strain-induced crystallization The susceptibility of un.saturated rubbers to ozone attack and subsequent cracking in the stretched state... 

Moreover, rubbers exhibit unique thermo-elastic effects unknown in metals, as noted first by Gough as early as 1805. Gough (1805) reported two distinctive responses, namely that (a) a rubber when held stretched under a constant force contracts reversibly on heating, and (b) it gives off heat reversibly when stretched at constant temperature (Treloar 1975). These important characteristics that were confirmed later by Joule (1859) are now referred to as the Gough-Joule effect and are key in the mechanistic understanding of the elastic behavior of rubbers. 

Fig. 3.5 Illustration of the experiment demonstrating the Gough-Joule effects. The light will heat the rubber strip, increases the latter s elastic modulus and then decreases the displayed weight in the electronic balance. Switched-off the light, the displayed weight will be gradually recovered...

Thus, the Gough-Joule effect can be understood as the manifestation of the thermoelastic inversion when seen from a different viewpoint. 

Physically, the temperature rise in a lament must be due to a combination of viscous dissipation and elastic (i.e., entropic) heating the Gough-Joule effect.(D The former is no doubt dominant in the case of fracture of high polymers(40) see below. But it is not possible at present to estimate the proportions of these two causal factors. It is to be expected that their... 

A unique quality of rubber is the Gough-Joule effect. Unlike other materials, when rubber is stretched rapidly it heats up. If rubber is stretched under a load, it will retract as the temperature is raised and it is held at the other end. 

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