The arguments advanced by wall and flory against the network. 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 31 were reversible. It is fundamentally different from the restoring force in a spring, which relies on the mechanical stiffness of the material.
The basic concepts and procedures underlying the theory of rubber elasticity are analyzed. Thermodynamics of rubber elasticity proceedings of the. 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. Why do rubber bands heat up when you stretch them and cool down when you allow them to compress. Thermodynamics of rubber elasticity proceedings of the royal. To understand the molecular properties and theoretical concepts that characterize rubber elasticity. A thermodynamic study of an isotropic rubber band under uniaxial stress is presented on the basis of its equation of state. The process of vulcanization, which links the polymer molecules into a three dimensional network, enables reversible thermodynamic.
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. This allows students to experimentally check the predictions of the entropic spring model for elastomers and observe that the entropy does. Sup2 rubber bands and entropic elasticity ucsd nano. Thermodynamics of rubber elasticity at constant volume. Some aspects of rubberlike elasticity useful in teaching basic concepts in physical chemistry. Theory thermodynamics provides us with relationships among different properties of a material. 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. 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. The molecular processes responsible for rubber elasticity are most readily interpreted in terms of the constant volume coefficients.
What rises with temperature, is the force that returns stretched rubber to. Introduction we are all familiar with the very useful properties of such objects as rubber bands, solid rubber balls. The alternative theory which they advocate, and which is rather widely used, is criticized on two grounds. Rubber elasticity in the introductory thermodynamics course. 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. Need to change conformation and extension under stress. Thermoelastic measurements at constant volume are reported for a series of natural rubber samples. It also serves as an experimental link to statistical thermodynamics models for a rubber band, which is taught to students in more advanced courses. 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. Rubber elasticity physical chemistry of macromolecules. The connection to thermodynamics was firmly established in 1859 when. We will focus on isotropic elasticity and consider anisotropy later on.
How temperature affects the stretch of a rubber band. Both thermodynamics and statistical mechanical approach to describe rubber elasticity are reminiscent of the gas behavior. Thermodynamics of elasticity of natural rubber rubber. First the distribution functions for molecular chain lengths in vulcanized rubber networks are considered from the point of view of symmetry. Thermodynamics of rubber elasticity request pdf researchgate. 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. Elasticity and thermo elasticity note this hw set, especially the last question, is purposely longer and more di cult than the previous ones. Gale rhodes department of chemistry university of southern maine portland, maine 041049300. 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. Thermodynamics of rubber elasticity chemistry libretexts.
Rubber isnt a manmade creation, although we do use it in countless applications to make our life easier. Rubber elasticity in thermodynamics courses netsu sokutei 43 w43 2016 33 stable rubber sample e. This equation cannot be deduced from thermodynamics because no hypothesis on the structure of matter can be made in any rigorous thermodynamic study. What rises with temperature, is the force that returns stretched rubber to its relaxed shape. Very large deformability with complete recoverability. In this chapter, we study the structures and mechanical properties of rubbers on the basis of the statisticalmechanical models of polymer networks. This book is an introductory level, thoroughly referenced presentation of rubberlike elasticity in a concise but clear manner. The energy component of the stress supported by the network is more or less independent of the network cure at a value of 0. Bertrand, professor of chemistry thermodynamics in two dimensions surface tension. We also acknowledge previous national science foundation support under grant numbers 1246120, 1525057. The equation of state is expressed as a functional relationship connecting the various parameters needed to specify.
Using rubberelastic materialideal gas analogies to teach introductory thermodynamics. 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. Roussel department of chemistry and biochemistry university of lethbridge february 21, 2009 a rubber is a material that can undergo large deformations e. Rubber elasticity in the introductory thermodynamics course article in journal of thermal analysis and calorimetry 693. Please, help me with this formula derivation of equation 9, taken from the article thermodynamics of rubber elasticity by j. Rubber elasticity in the introductory thermodynamics. 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 molecular processes responsible for rubber elasticity are most readily interpreted in terms of the constant. In summary, the average reader should find rubberlike elasticity, a molecular primer useful and quite interesting. 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.
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. 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 crosslinking property of polymers is vital to the bands elasticity. Thermodynamics of rubber elasticity and discussion jstor. When we write down the differential of u in courses in chemical thermodynamics, we nor mally only consider. 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. Definition of rubber elasticity and requirements definition of rubber elasticity. At room temperature, a rubber band snaps back due to its elastic molecular properties. Thermodynamics of rubber elasticity journal of chemical. This may be explained by the different time rate of deformation in his and our experiments. Elasticity of thermodynamical substances numericana. The arguments advanced by wall and flory against the network theory of the authors are shown to be without.
Chapter 7 2 thermodynamics of rubber in the last section, we considered crosslinking and gelation reactions that formed polymer networks and gels. If you released a rubber band with properties like that, it would. James, department of physics, purdue university, lafayette, indiana. Geoffrey allen, umberto bianchi, and colin price 1964 thermodynamics of elasticity of natural rubber. As reaction proceeds su ciently far beyond the gel point, p. Science and education thermodynamics of rubber elasticity j. Elasticity and thermodynamics in this chapter, we will introduce elasticity and elastic moduli, and see what elasticity has to do with thermodynamic quantities. Elasticity of polymer networks chapter 4 polymer physics. One measures the stiffness by changing the force while. Elasticity e is the increase in tension per unit of crosssectional area or a small relative increase in the elongation of a wire. A section of the topic gels, is attached, because both rubber and gels are in the same physical state. Theory of rubber elasticity thermodynamics, statistical mechanics and chain statistics kelvin, kuhn, guth, mark, james, treloar and flory second law of thermodynamics.
This paper describes only the thermodynamic properties of vulcanized rubber. Using rubber elastic materialideal gas analogies to teach introductory thermodynamics. In rubber the elastic force is due to the thermal interactions of the molecules within 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. The elasticity of rubbers is largely due to conformational rearrangements of the chains, which are obtained largely by rotations around. 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. Please, help me with this formula derivation of eq. 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. Rubber elasticity wikimili, the best wikipedia reader. An elastomer has rather unusual physical properties. 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. The rubber band was patented in england on march 17, 1845 by stephen perry.
Umr chemlabs thermodynamics of rubber elasticity pch 599 gary l. First the distribution functions for molecular chain lengths in vulcanized rubber networks are considered from the point. Dwrev3d pdv, and occasionally with work in onedimension. For rubber bands we are most interested in the relationships among the. Tibbitt eth zuric h 31 march 2020 1 suggested reading polymer physics rubinstein and colby. It was first described in 1807 by thomas young 17731829. Pdf thermodynamics of rubber elasticity jose manzanares. This is a supplemental video on entropic elasticity and the direction of heat flow. 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. It summarizes the rst part of the course, and demands a working knowledge of linear elasticity. The different microscopic gaussian models so far available 8.
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. Elasticity and thermoelasticity note this hw set, especially the last question, is purposely longer and more di cult than the previous ones. A resource for teachers a script for classroom demonstration illustrating dg dh tds. Entropy and rubbery elasticity journal of chemical education. Later, this would be associated with a change in entropy. The energy component of the stress supported by the network is more or less independent of.
The strands that make up the rubber band stretch, but forces in the rubber molecules pull them back to their original shape. Request pdf thermodynamics of rubber elasticity a thermodynamic study of an isotropic rubber band under uniaxial stress is presented on. Apr 07, 2017 why do rubber bands heat up when you stretch them and cool down when you allow them to compress. This also gives a measure of reproducibility of the present experimental method. The connection to thermodynamics was firmly established in 1859. During recent years, considerable progress has been made in connection with theories of rubber elasticity.
Now, is elasticity intended to mean the elastic spring constant. Abstract a thermodynamic study of an isotropic rubber band under uniaxial stress is presented on the basis of its equation of state. The characteristic elasticity of polymeric materials appears from the conformational entropy of these random coils. The arguments advanced by wall and flory against the network theory of the authors are shown to be without foundation. Sup2 rubber bands and entropic elasticity ucsd nano 4. 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. The intensive thermodynamic state of an isotropic elastic solid is determined by the stress components and the temperature. Elasticity and thermodynamics msae4215 documentation. 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.
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. Most materials, when stressed, exhibit a limited elastic in the next section, the choice of stress. That means that the heated rubber band takes more tension in stretching, i. Thermodynamics demonstration originally prepared for the coursera mooc.
Assuming a relaxed network to be isotropic and a network subject to. Jan 27, 2016 thermodynamics demonstration originally prepared for the coursera mooc. The flory theory of rubber elasticity has pointed out the rubber elasticity has primarily entropic origins. Dec 23, 2004 the basic concepts and procedures underlying the theory of rubber elasticity are analyzed. Polymers are essentially long, chainlike molecules composed of many identical or nearly identical subunits. What happens if you release the stress applied to a crosslinked coil. When relaxed, the strands roll into tiny tangled balls. E is called youngs modulus, to distinguish it from other elasticity coefficients.
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