Thesis-1976-Moneypenny.pdf (8.13 MB)
The influence of pressure on relaxations in glassy-state polymers
thesisposted on 2018-11-21, 11:39 authored by Henry G. Moneypenny
Glass-forming high polymers have been densified by application of high hydrostatic pressure (≈ 1.5 kbar) in the melt, followed by cooling under pressure to ambient. A density increase of about 1% was induced in each of the following polymers: polyvinyl chloride, polymethyl methacrylate, polystyrene, poly-4-chlorostyrene, poly-3-chlorostyrene, poly-4-methoxystyrene and poly-4-phenoxystyrene. Differential thermal analysis (DSC) and volume relaxation techniques were used to study the reversion of the densified glass to a more normal glass at a temperature ≈Tg–15K in general. Enthalpy relaxation (a change from glass I to glass II) in this region gives a peak or diffuse hump on the DSC scan prior to a normal glass transition temperature. It is considered that although the densified glasses may become thermodynamically stable at a sufficiently low temperature they are inherently unstable at ambient. Reversion to a more normal class is kinetically too slow to measure at ambient in all cases studied except polymethyl methacrylate. [Continues.]
Science Research Council (research scholarship).
Publisher© H.G. Moneypenny
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NotesA Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of the degree of Doctor of Philosophy at Loughborough University.