Glass transition and thermodynamic state of densified polymeric glasses

Brown, Iain; Wetton, R.E.; Richardson, M.J.; Savill, N.G.

doi:10.1016/0032-3861(78)90119-2

Cited by 45 publications

(33 citation statements)

References 15 publications

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“…As stated earlier, as sub-Tg annealing time increases the free volume related to nolecular mobility decreases, and thus the temperature at which the molecular rearrangement occurs will increase with annealing time since more thermal energy will be required to cause motion. Also, the enthalpy recovery peak will occur at higher temperatures for faster heating rates (18). This is also explained on the basis of molecular mobility.…”

Section: Differential Scanning Calorimetrymentioning

confidence: 88%

“…Glassy polymers in this nonequilibrium condition exhibit quite dramatic structural and property changes upon annealing below the glass transition temperature (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). This observed aging behavior -variously referred to as nonequilibrium behavior, enthalpy or volume recovery, or simply physical agingis a direct result of the nonequilibrium nature of the glassy state.…”

Section: Introductico-mentioning

confidence: 99%

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Physical aging studies of semicrystalline poly(ethylene terephthalate)

Tant

Wilkes

1981

J of Applied Polymer Sci

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Physical aging of semicrystalline poly(ethylene terephthalate) has been investigated as a function of crystalline content. Stress–strain, stress relaxation, and differential scanning calorimetry experiments were used to monitor the physical aging process. Both the overall extent and the rate of physical aging in this material decrease with increasing crystallinity. Several possible reasons for this behavior are advanced and discussed. It was also found that the drawing behavior of amorphous PET changes significantly as physical aging progresses. Specifically, for samples aged and then elongated, the extent of localized deformation (necking) and associated strain‐induced crystallization was greater for samples aged for longer periods of time.

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Section: Differential Scanning Calorimetrymentioning

confidence: 88%

Section: Introductico-mentioning

confidence: 99%

Physical aging studies of semicrystalline poly(ethylene terephthalate)

Tant

Wilkes

1981

J of Applied Polymer Sci

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“…Figure Brown, et al [36] have also reported DSC and dilatometric studies on densified polymeric glasses. Their work showed that the volumetric behavior of densified glasses is that which would be expected; i.e.…”

Section: XImentioning

confidence: 96%

An overview of the nonequilibrium behavior of polymer glasses

Tant¹,

Wilkes²

1981

Polymer Engineering & Sci

216

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“…had originally found that a glass formed at a high p has a higher density at low p than a glass formed at low p. The subject was briefly reviewed by Weitz and Wunderlich 12 by Brown et al 13 and by Johari 14 , the last providing extensive references to previous studies of glasses formed under high pressure and studied at 1 bar (0.1 MPa) pressure. In contrast, Bree et al, 15 found that, in general, densification affects the thermomechanical properties only slightly.…”

mentioning

confidence: 98%

Sub-T g features of glasses formed by cooling glycerol under pressure – Additional incompatibility of vibrational with configurational states in the depressurized, high density glass

Andersson

Johari

2016

The Journal of Chemical Physics

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PostprintThis is the accepted version of a paper published in Journal of Chemical Physics. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. Citation for the original published paper (version of record):Andersson, O., Johari, G P. (2016) Sub-Tg features of glasses formed by cooling glycerol under pressure -Additional incompatibility of vibrational with configurational states in the depressurized, high density glass. Journal of Chemical Physics AbstractThe vibrational state of a glass is naturally incompatible with its configurational state, which makes the glass structurally unstable. When a glass is kept at constant temperature, both the vibrational and configurational states of a glass change with time until (equilibrium) liquid state is reached, and the two states become compatible. The process, known as structural relaxation, occurs at a progressively higher rate during heating and the properties of a glass change accordingly. We add to this incompatibility by depressurizing a glass that had been formed by cooling a liquid under a high pressure, p, and then investigate the effects of the added incompatibility by studying thermal conductivity, , and the heat capacity per unit volume C p of the depressurized glass. We use glycerol for the purpose, and study first the changes in the features of , and of C p during glass formation on cooling under a set of different p. We then partially depressurize the glass and study the effect of the p-induced instability on the features of  and C p as the glass is isobarically heated to the liquid state. At a given low p, the glass configuration that was formed by cooling at high-p had a higher  than the glass configuration that was formed by cooling at a low p. The difference is more when the glass is formed at a higher p and/or is depressurized to a lower p. On heating at a low p, its  decreases before its glass-liquid transition range is reached. The effect is the opposite of the increase in  observed on heating a glass at the same p under which it was formed. It is caused by thermallyassisted loss of the added incompatibility of configurational and vibrational states of a high-p formed glass kept at low p. If a glass formed under a low-p is pressurized and then heated under high p, it would show the opposite effect, i.e., its  would first increase to its high p value before its glass-to-liquid transition range. a joharig@mcmaster.ca 2

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Glass transition and thermodynamic state of densified polymeric glasses

Cited by 45 publications

References 15 publications

Physical aging studies of semicrystalline poly(ethylene terephthalate)

Physical aging studies of semicrystalline poly(ethylene terephthalate)

An overview of the nonequilibrium behavior of polymer glasses

Sub-T g features of glasses formed by cooling glycerol under pressure – Additional incompatibility of vibrational with configurational states in the depressurized, high density glass

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