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Measuring the viscoelastic properties of polytetrafluoroethylene copolymers at ultrasonic frequencies
|dc.description||Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to email@example.com, referencing the URI of the item.||en_US|
|dc.description||Includes bibliographical references.||en_US|
|dc.description.abstract||Since polytetrafluoroethylene (PTFE) and its copolymers are insoluble in most common solvents, direct measurement of their molecular weight distribution by conventional techniques such as size exclusion chromatography (SEC) is not possible. Instead, the structure must be inferred from the linear viscoelastic properties of the melt. To make this inference, the spectrum over a wide enough range of relaxation times to include the plateau modulus, GNI is required. For most polymers this is accomplished by time-temperature superposition, but for PTFE and its copolymers, with their burning points being not much higher than the melting points, this is not possible. Since they do not exist in the melt state over a wide enough temperature range for superposition, their viscoelastic properties must be measured directly. A new technique employing a piezoelectric ultrasonic composite oscillator has been developed to measure the viscoelastic properties, GI(w) and G"(w), of Tefzel 280 (a high molecular weight copolymer of ethylene and tetrafluoroethylene) at ultrasonic frequencies (40-200 kHz). A discrete relaxation spectrum for Tefzel 280 has been determined.||en_US|
|dc.publisher||Texas A&M University||en_US|
|dc.rights||This thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries in 2008. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use.||en_US|
|dc.subject||Major mechanical engineering.||en_US|
|dc.title||Measuring the viscoelastic properties of polytetrafluoroethylene copolymers at ultrasonic frequencies||en_US|
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