Thermodynamics of the densification process for polymer glasses

McKinney, John E.; Simha, Robert

doi:10.6028/jres.081a.018

Cited by 46 publications

(33 citation statements)

References 23 publications

(59 reference statements)

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“…This value is in agreement with values reported in the literature for polystyrene which range from 0.25 to 0.40 K/ MPa. [26][27][28][29][30][31][32] Also shown in Figure 1 are comparisons of our data to those of Oels and Rehage 33 and Quach and Simha. 22 Oels and Rehage used a lower molecular weight polystyrene (M w ¼ 20,400 g/mol, M w /M n ¼ 1.06); hence, their T g values are $ 7 K lower than ours at low pressures.…”

Section: Resultsmentioning

confidence: 97%

Pressure relaxation of polystyrene and its comparison to the shear response

Meng

Simon

2007

J Polym Sci B Polym Phys

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Isothermal pressure relaxation as a function of temperature in two pressure ranges has been measured for polystyrene using a self-built pressurizable dilatometer. A master curve for pressure relaxation in each pressure regime is obtained based on the time-temperature superposition principle, and time-pressure superposition of the two master curves is found to be applicable when the master curves are referenced to their pressure-dependent T g . The pressure relaxation master curves, the shift factors, and retardation spectra obtained from these curves are compared with those obtained from shear creep compliance measurements for the same material. The shift factors for the bulk and shear responses have the same temperature dependence, and the retardation spectra overlap at short times. Our results suggest that the bulk and shear response have similar molecular origin, but that longtime chain mechanisms available to shear are lost in the bulk response.

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Section: Resultsmentioning

confidence: 97%

Pressure relaxation of polystyrene and its comparison to the shear response

Meng

Simon

2007

J Polym Sci B Polym Phys

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“…Since T g depends on the way the glass was prepared, the pressure dependence of T g , d T g /d P , is a function of the thermodynamic history. In analogy to the Ehrenfest derivation, formally setting f ( T , P , h ) = 0, one obtains P ‐derivative at T g as:34, 55, 56, 62, 78 where (∂ T /∂ h ) P is computed from the isobaric data in the molten state near T g , using eqs 6 and 7, and (d h /d P ) = d h ( T g , P g )/d P is calculated along the T g = T g ( P ) line.…”

Section: Discussionmentioning

confidence: 99%

Pressure–volume–temperature of molten and glassy polymers

Utracki

2006

J Polym Sci B Polym Phys

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The pressure–volume–temperature (PVT) dependencies of several amorphous polymers (PS, PC, PPE, and PPE/PS 1:1 blend) in the glassy and molten state were studied. The Simha–Somcynsky (S–S) lattice‐hole equation of state (EOS) was used. Fitting the PVT data in the molten state to the EOS yielded the free volume quantity, h = h(T, P), and the characteristic reducing parameters, P*, V*, and T*. The data within the glassy region were interpreted assuming that the latter parameters are valid in the molten and vitreous state, than calculating h = h(T, P) from the experimental values of V = V(T, P). Next, the frozen free volume fraction in the glass was computed as FF = FF(P). The FF values of polystyrene (PS) resins at ambient pressure showed little scattering (FFP=1 = 0.691 ± 0.008), while their P‐dependencies varied, reflecting the thermodynamic history of the glass formation as well as the PVT measurements protocol. The pressure gradient of Tg was compared with the Ehrenfest relation for the second‐order transition; here also agreement depended on the method of vitrification. The experimental values of FF at ambient pressure decreased with increasing values of the characteristic temperature reducing parameter, T*. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 270–285, 2007.

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“…Subsequently, exhaustive tests of the theory against PVT data in both the molten and vitreous states were carried out by a succession of students (Phil Wilson, Shirley Lee, Jim Berg, Olagoke Olabisi, and Jim Roe). With John McKinney, Robert extended the S-S theory to nonequilibrium polymeric systems, such as glasses [McKinney and Simha, 1974, 1976, 1977. Other important theoretical developments were, with Raj Jain, an extension of singlecomponent S-S treatment to binary mixtures [Jain and Simha, 1984] and, with Eric Nies and co-workers, an introduction of nonrandomness in the hole distribution by Xie et al [1992].…”

Section: Cleveland 1968-2008mentioning

confidence: 99%