Roussel department of chemistry and biochemistry university of lethbridge february 21, 2009 a rubber is a material that can undergo large deformations e. Why do rubber bands heat up when you stretch them and cool down when you allow them to compress. Thermodynamics of rubber elasticity and discussion jstor. For rubber bands we are most interested in the relationships among the.
Jan 27, 2016 thermodynamics demonstration originally prepared for the coursera mooc. Thermodynamics of rubber elasticity at constant volume. Pdf thermodynamics of rubber elasticity jose manzanares. This also gives a measure of reproducibility of the present experimental method. The arguments advanced by wall and flory against the network. The process of vulcanization, which links the polymer molecules into a three dimensional network, enables reversible thermodynamic. Bertrand, professor of chemistry thermodynamics in two dimensions surface tension. Thermodynamics of rubber elasticity journal of chemical. In this chapter, we study the structures and mechanical properties of rubbers on the basis of the statisticalmechanical models of polymer networks.
Most rubber bands are manufactured out of natural rubber or, especially at larger sizes, elastomer, and are sold in a variety of sizes. It is fundamentally different from the restoring force in a spring, which relies on the mechanical stiffness of the material. If we can develop a theory for the thermodynamic properties of rubbers, then equation 2 will give us an equation for the force which must be. Dec 22, 2004 two principal differences between the theories of rubber elasticity advanced by james and guth and by other authors are examined in the light of certain fundamental concepts. Theory of rubber elasticity thermodynamics, statistical mechanics and chain statistics kelvin, kuhn, guth, mark, james, treloar and flory second law of thermodynamics. The libretexts libraries are powered by mindtouch and are supported by the department of education open textbook pilot project, the uc davis office of the provost, the uc davis library, the california state university affordable learning solutions program, and merlot. In summary, the average reader should find rubberlike elasticity, a molecular primer useful and quite interesting. The arguments advanced by wall and flory against the network theory of the authors are shown to be without. Gale rhodes department of chemistry university of southern maine portland, maine 041049300. For rubber bands we are most interested in the relationships among the tension or restoring force, f. A section of the topic gels, is attached, because both rubber and gels are in the same physical state. Very large deformability with complete recoverability. In fact, natural rubber is a special type of chemical compound called an elastomer, composed of unique molecules that can stretch to nearly double their normal length.
In rubber the elastic force is due to the thermal interactions of the molecules within the material. By using the following basic equations for helmholtz free energy and its discussion about entropy, the force generated from the deformation of a rubber chain from its. The arguments advanced by wall and flory against the network theory of the authors are shown to be without foundation. Assuming a relaxed network to be isotropic and a network subject to. It summarizes the rst part of the course, and demands a working knowledge of linear elasticity. We also acknowledge previous national science foundation support under grant numbers 1246120, 1525057. Jan 04, 2018 the modern rubber band is made out of natural rubber, a polymer derived from the latex of a rubber tree synthetic rubber is generally not as stretchy. Equation of state and molecular structure objective to determine the macroscopic thermodynamic equation of state of an elastomer, and relate it to its microscopic molecular properties. By using the following basic equations for helmholtz free energy and its discussion about entropy, the force generated from the deformation of a rubber chain from its original unstretched conformation can be derived. Abstract a thermodynamic study of an isotropic rubber band under uniaxial stress is presented on the basis of its equation of state. The equation of state is expressed as a functional relationship connecting the various parameters needed to specify. When we write down the differential of u in courses in chemical thermodynamics, we nor mally only consider. The behavior of the rubber band is compared with both that of an ideal elastomer and that of an ideal gas, considering the generalized joules law as the ideality criterion. The flory theory of rubber elasticity has pointed out the rubber elasticity has primarily entropic origins.
That means that the heated rubber band takes more tension in stretching, i. This book is an introductory level, thoroughly referenced presentation of rubberlike elasticity in a concise but clear manner. Geoffrey allen, umberto bianchi, and colin price 1964 thermodynamics of elasticity of natural rubber. Two general types of theories have been advanced, one from a macroscopic point of view and the other from a molecular point of view. Using rubberelastic materialideal gas analogies to teach introductory thermodynamics. Without this property, the rubber band would have no reason to tend towards a tangled state, since the entropy would be about the same in both states. At room temperature, a rubber band snaps back due to its elastic molecular properties. What rises with temperature, is the force that returns stretched rubber to. The energy component of the stress supported by the network is more or less independent of the network cure at a value of 0.
A resource for teachers a script for classroom demonstration illustrating dg dh tds. Rubber elasticity in the introductory thermodynamics course. Entropy and rubbery elasticity journal of chemical education. Elasticity e is the increase in tension per unit of crosssectional area or a small relative increase in the elongation of a wire. The energy component of the stress supported by the network is more or less independent of. He does not give the time rate of elongation in his paper but it is likely that the large weight needed in his experiment took a much longer time to. The basic concepts and procedures underlying the theory of rubber elasticity are analyzed. The rubber band was patented in england on march 17, 1845 by stephen perry.
Thermodynamics demonstration originally prepared for the coursera mooc. Elasticity and thermo elasticity note this hw set, especially the last question, is purposely longer and more di cult than the previous ones. The intensive thermodynamic state of an isotropic elastic solid is determined by the stress components and the temperature. Thermodynamics of rubber elasticity chemistry libretexts. Elasticity and thermodynamics msae4215 documentation. Rubber elasticity in the introductory thermodynamics. How temperature affects the stretch of a rubber band.
The connection to thermodynamics was firmly established in 1859. Definition of rubber elasticity and requirements definition of rubber elasticity. During recent years, considerable progress has been made in connection with theories of rubber elasticity. Theory thermodynamics provides us with relationships among different properties of a material. Most materials, when stressed, exhibit a limited elastic in the next section, the choice of stress. Science and education thermodynamics of rubber elasticity j. This is a supplemental video on entropic elasticity and the direction of heat flow. What happens if you release the stress applied to a crosslinked coil. Elasticity of polymer networks chapter 4 polymer physics. First the distribution functions for molecular chain lengths in vulcanized rubber networks are considered from the point. Thermodynamics of rubber elasticity proceedings of the.
Tibbitt eth zuric h 31 march 2020 1 suggested reading polymer physics rubinstein and colby. First the distribution functions for molecular chain lengths in vulcanized rubber networks are considered from the point of view of symmetry. Rubber elasticity physical chemistry of macromolecules. Put another way, since youre asking about elasticity in the context of a hot and a cold rubber band loaded by the same weight, i should emphasize that one cant directly measure a systems stiffness by keeping the force constant and observing the displacement when changing other things. Umr chemlabs thermodynamics of rubber elasticity pch 599 gary l. An elastomer has rather unusual physical properties. Exploring the thermodynamics of a rubber band david roundy department of physics, oregon state university, corvallis, oregon 97331 michael rogers department of physics, ithaca college, ithaca, new york 14850 received 27 february 2012. Rubber elasticity in thermodynamics courses netsu sokutei 43 w43 2016 31 were reversible. Rubber isnt a manmade creation, although we do use it in countless applications to make our life easier. Abstract two principal differences between the theories of rubber elasticity advanced by james and guth and by other authors are examined in the light of certain fundamental concepts. This allows students to experimentally check the predictions of the entropic spring model for elastomers and observe that the entropy does. We describe an upperdivision experiment in thermal physics where students measure the tension of a rubber band as a function of temperature and length and use a maxwell relation to find the change in internal energy and entropy for an isothermal stretch. Two principal differences between the theories of rubber elasticity advanced by james and guth and by other authors are examined in the light of certain fundamental concepts. Thermodynamics of rubber elasticity proceedings of the royal.
The elasticity of rubbers is largely due to conformational rearrangements of the chains, which are obtained largely by rotations around. Thermoelastic measurements at constant volume are reported for a series of natural rubber samples. To understand the molecular properties and theoretical concepts that characterize rubber elasticity. The molecular processes responsible for rubber elasticity are most readily interpreted in terms of the constant volume coefficients. Thermodynamics of elasticity of natural rubber rubber. One measures the stiffness by changing the force while. This paper describes only the thermodynamic properties of vulcanized rubber. The alternative theory which they advocate, and which is rather widely used, is criticized on two grounds. The equation of state for a substance provides the additional information required to calculate the amount of work that the substance does in making a transition from one equilibrium state to another along some specified path. Dec 26, 2015 the libretexts libraries are powered by mindtouch and are supported by the department of education open textbook pilot project, the uc davis office of the provost, the uc davis library, the california state university affordable learning solutions program, and merlot. Rubber elasticity in thermodynamics courses netsu sokutei 43 w43 2016 33 stable rubber sample e.
A rubber band also known as an elastic band, gum band or lacky band is a loop of rubber, usually ring shaped, and commonly used to hold multiple objects together. What rises with temperature, is the force that returns stretched rubber to its relaxed shape. Need to change conformation and extension under stress. It also serves as an experimental link to statistical thermodynamics models for a rubber band, which is taught to students in more advanced courses. The crosslinking property of polymers is vital to the bands elasticity. Rubber elasticity wikimili, the best wikipedia reader. Sup2 rubber bands and entropic elasticity ucsd nano.
As reaction proceeds su ciently far beyond the gel point, p. The gaussian theory of rubber elasticity as reformulated by flory is able to account satisfactorily for the temperature dependence of the force, but it does not lead to. We will focus on isotropic elasticity and consider anisotropy later on. The molecular processes responsible for rubber elasticity are most readily interpreted in terms of the constant. Dwrev3d pdv, and occasionally with work in onedimension. Chapter 7 2 thermodynamics of rubber in the last section, we considered crosslinking and gelation reactions that formed polymer networks and gels. This equation cannot be deduced from thermodynamics because no hypothesis on the structure of matter can be made in any rigorous thermodynamic study. James, department of physics, purdue university, lafayette, indiana.
When relaxed, the strands roll into tiny tangled balls. Elasticity and thermodynamics in this chapter, we will introduce elasticity and elastic moduli, and see what elasticity has to do with thermodynamic quantities. This may be explained by the different time rate of deformation in his and our experiments. The process of vulcanization, which links the polymer molecules into a three dimensional network, enables reversible thermodynamic measurements to be made on elastomeric materials from which the entropy and energy contributions to the free energy of deformation can be determined. Polymers are essentially long, chainlike molecules composed of many identical or nearly identical subunits. Price department of chemistry, university of manchester, manchester m 9pl the process of vulcanization, which links the polymer molecules into a three dimensional network, enables reversible thermodynamic measurements to be made on elastomeric materials from which the entropy and. Apr 07, 2017 why do rubber bands heat up when you stretch them and cool down when you allow them to compress. However, the rubberlike elasticity can also be studied using the methods of statistical mechanics.
Elasticity of thermodynamical substances numericana. Rubber elasticity in the introductory thermodynamics course article in journal of thermal analysis and calorimetry 693. It was first described in 1807 by thomas young 17731829. Crosslinked polymers and rubber elasticity chapter 9 sperling definition of rubber elasticity and requirements crosslinks, networks, classes of elastomers sections, 16 simple theory of rubber elasticity sections 48. Some aspects of rubberlike elasticity useful in teaching basic concepts in physical chemistry.
Introduction we are all familiar with the very useful properties of such objects as rubber bands, solid rubber balls. A thermodynamic study of an isotropic rubber band under uniaxial stress is presented on the basis of its equation of state. The strands that make up the rubber band stretch, but forces in the rubber molecules pull them back to their original shape. E is called youngs modulus, to distinguish it from other elasticity coefficients. Later, this would be associated with a change in entropy. Sup2 rubber bands and entropic elasticity ucsd nano 4. Thermodynamics of rubber elasticity request pdf researchgate. Dec 23, 2004 the basic concepts and procedures underlying the theory of rubber elasticity are analyzed. Please, help me with this formula derivation of equation 9, taken from the article thermodynamics of rubber elasticity by j. Elasticity and thermoelasticity note this hw set, especially the last question, is purposely longer and more di cult than the previous ones. Request pdf thermodynamics of rubber elasticity a thermodynamic study of an isotropic rubber band under uniaxial stress is presented on. If you released a rubber band with properties like that, it would.
Both thermodynamics and statistical mechanical approach to describe rubber elasticity are reminiscent of the gas behavior. Please, help me with this formula derivation of eq. Now, is elasticity intended to mean the elastic spring constant. The characteristic elasticity of polymeric materials appears from the conformational entropy of these random coils. Taken as a whole the results from thermodynamic studies on lightly crosslinked rubbery polymers support the view that the retractive force is primarily intramolecular in origin. The different microscopic gaussian models so far available 8. The connection to thermodynamics was firmly established in 1859 when. Using rubber elastic materialideal gas analogies to teach introductory thermodynamics.
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