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Title: The influence of pressure on relaxations in glassy-state polymers
Author: Moneypenny, Henry G.
ISNI:       0000 0001 3414 764X
Awarding Body: Loughborough University of Technology
Current Institution: Loughborough University
Date of Award: 1976
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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.
Supervisor: Not available Sponsor: Science Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available