THERMODYNAMICS OF DEFORMATION (CALORIMETRY, THERMOELASTICITY, STRESS-INDUCED CRYSTALLIZATION, RUBBER HEAT ENGINES)
The thermodynamics of uniaxial solid deformation was studied experimentally for a number of polymeric solids, including two polyurethane-urea elastomers, natural rubber, a thermoplastic elastomer and low density polyethylene. A deformation calorimeter was developed to measure the heat and work of un...
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| Language: | ENG |
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ScholarWorks@UMass Amherst
1985
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| Online Access: | https://scholarworks.umass.edu/dissertations/AAI8517128 |
| Summary: | The thermodynamics of uniaxial solid deformation was studied experimentally for a number of polymeric solids, including two polyurethane-urea elastomers, natural rubber, a thermoplastic elastomer and low density polyethylene. A deformation calorimeter was developed to measure the heat and work of uniaxial solid deformation and measurements were made on the above materials. A differential scanning calorimetry method was developed to characterize the melting behavior of stretched elastomers which were found to undergo stress-induced crystallization during stretching as deduced from the large but recoverable internal energy changes measured by deformation calorimetry during uniaxial extension and contraction. Wide angle x-ray diffraction and thermostatic measurements were also performed on the elastomers held in the extended state in order to characterize the amorphous-crystalline phase transition which occurs during deformation. The motivation for this work was to evaluate the performance of the two polyurethane-urea elastomers which were found to function effectively as working substances in rubber heat engines. These elastomers could generate 1 Joule of work per gram of elastomer at about 3% of Carnot efficiency in experimental Sterling cycles. |
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