Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636196
Title: The deformation of polymers upon uniaxial loading studied by Raman spectroscopy
Author: Callaghan, R.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1980
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Abstract:
Zhurkov uniaxially loaded thin film polymer specimens and observed a decrease in the frequency of the band maxima of the skeletal vibrations, together with a pronounced low frequency asymmetry of the shifted bands. These shifts were interpretated as arising from the weakening of the force constants of the skeletal vibrations upon loading. So the low frequency asymmetry is related to bonds whose force constants have been even more weakened than those associated with the band maxima frequency shift. American workers extended the proposed mechanisms of frequency shifts to include bond angle variations, conformational changes and defect contributions. Even using laser Raman studies injection and compression moulded samples. The previous work used I.R. Evans noted increases and decreases in skeletal shifts together with side group shifts. These shifts were explained in terms of the orientation, new secondary valence forces and complex morphological changes which occur on deforming a polymer. This study examined polythene, polytetrafluozoetheie and nylon using a jig to stress the samples in the laser beam. Thus the stress produced in the sample could be directly related to the shift observed. Inflation blown, injection and compression moulded samples were studies as well as low and high density and ultra-drawn samples. On stressing these samples it can be seen skeletal shift discontinuities and side group shifts are widespread. The primacy of morphological disorder via orientation and new secondary valence forces is asserted as a mechanism of frequency shifts. This proposal received confirmatory evidence from the various elevated drawing and annealing experiments carried out. Hence the simple stressed bond theory originally proposed by Zhurkov is incomplete and inadequate to explain the frequency shifts observed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.636196  DOI: Not available
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