Rate-determining factors for enthalpy relaxation of glassy polymers. Molecular weight

Marshall, A. S.; Petrie, S. E. B.

doi:10.1063/1.321447

Cited by 114 publications

(51 citation statements)

References 12 publications

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“…Our preliminary interpretation of this phenomenon is that it is due to enthalpy relaxation . Similar effects are observed in other polymers annealed at temperatures up to 30°C below their glass transition temperatures (11,12). This effect has important practical consequences for the conditioning of materials prior to measurement of any properties .…”

Section: A Differential Scanning Calorimetry (Dsc)supporting

confidence: 52%

Molecular Structure and Cohesive Properties of Polymeric Adhesives.

Doyle¹

1978

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Section: A Differential Scanning Calorimetry (Dsc)supporting

confidence: 52%

Molecular Structure and Cohesive Properties of Polymeric Adhesives.

Doyle¹

1978

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“…Petrie and coworker 21,22 compute the areas by using a sigmoidal baseline. However, the choice of sigmoidal baseline is not unique.…”

Section: Resultsmentioning

confidence: 99%

“…To quantify the relationship of the overshoot with respect to the annealing period, we have adopted a technique similar to that used by Petrie and coworker, 21,22 but using a different algorithm for evaluating the area under the curve. Petrie and coworker 21,22 compute the areas by using a sigmoidal baseline.…”

Section: Resultsmentioning

confidence: 99%

Enthalpic relaxation of silica–polyvinyl acetate nanocomposites

Amanuel

Gaudette

Sternstein

2008

J Polym Sci B Polym Phys

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Although the effects of filler nanoparticles size and surface treatment on the glass transition temperature of the matrix phase have received well-deserved attention, nanofiller effects on other physical parameters associated with the glass transition have received less interest. To better understand how the incorporation of nanofillers affects the enthalpic relaxations associated with the glass transition, differential scanning calorimeter measurements were carried out on silica-polyvinyl acetate nanocomposites with respect to filler content, annealing temperature, and annealing period. As expected, longer annealing periods below the glass transition temperature resulted in an increase of the subsequent enthalpic relaxations. However, the presence of filler substantially reduces the enthalpic relaxation relative to that of the neat polymer at longer annealing periods only. The underlying enthalpic relaxations and the effects suppressed by the fillers are specific to the annealing temperature. These results suggest a significant alteration in the physical state of the matrix because of the presence of the filler particles. However, this does not imply the existence of a glassy layer or layers with a glass transition gradient near the filler surface.

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“…In particular, the diagram of enthalpy-temperature curve is displayed in many literatures to illustrate enthalpic T g , unrelaxed enthalpy, equilibrium glassy state and so on. [35][36][37][38] However, this paper is the first, to the author's knowledge, that S c curve was constructed concerning the real material for the specified T A and t A .…”

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confidence: 99%

Enthalpy Relaxation of Liquid Crystalline Polymer with Cyanobiphenyl Group in the Side Chain: Analysis based on Configurational Entropy Model with the AG Expression

Tanaka

2009

Polym. J.

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The enthalpy relaxation of poly(cyanobipheny hexylacrylate) has been studied by differential scanning calorimetry. The experimental results of the heat capacity (c p ) were compared with the prediction of a phenomenological model for the process of structural relaxation based on the configurational entropy (S c ) and the relaxation time expressed by the Adam-Gibbs equation. This model follows the evolution of the configurational entropy of the sample during the whole thermal history including an isothermal annealing. The parameters of the model were calculated by simultaneous fits to the experimental results. With the calculation result, the peak position appeared in DSC curve of c p was interpreted using the plot of temperature dependence of S c . The plot showed that S c rapidly approached to the configurational entropy of equilibrium (S c eq ) in the narrow temperature range around T g , which is often referred to as the recovery of enthalpy, and thus the recovery of S c , in interpreting the enthalpy relaxation. As the measure of structural relaxation upon the isothermal ageing, the value of relaxation function () was considered, which estimates the departure from the equilibrium. The correlation between of S c and of enthalpy is also presented. The physical properties of the liquid crystalline polymer with cyanobiphenyl groups in the side chain (PCBA) have been studied with respect to the effects of molecular weight and spacer length.1,2 In the previous paper, the enthalpy relaxation measured using Differential Scanning Calorimetry (DSC) was analysed with the activation energy spectrum (AES) model. 3This model provides information about thermally activated processes which are available to contribute to observed changes in the properties upon physical ageing. For the enthalpy relaxation of PCBA6 (PCBA in which the spacer length is 6), the analysis gives the relation between the process number and the activation energy, in other words, the distribution of the relaxation process.In general, the decrease in enthalpy upon the isothermal ageing at temperature below the glass transition temperature T g , is closely related to the structural relaxation toward equilibrium in the glassy state. Concerning the relaxation of PCBA6, the optical texture was shown to vary in the previous paper, as an evidence of structural change. The change in optical texture is being considered as the coarsening dynamics of the disclinations. That is to say, the dynamics of PCBA6 molecules bring about the change in structure.On the other hand, the modelling approaches for enthalpy relaxation of polymer have been reported, which attempts to reproduce the measured DSC curve using quantities of state. The quantities of state employed are the configurational entropy, S c , and the fictive temperature, T f . 4,5 It has been shown that the main features of the relaxation process can be modelled on the basis of a distribution of relaxation times that depends both on the temperature and on the structure of the material represented by the value o...

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Rate-determining factors for enthalpy relaxation of glassy polymers. Molecular weight

Cited by 114 publications

References 12 publications

Molecular Structure and Cohesive Properties of Polymeric Adhesives.

Molecular Structure and Cohesive Properties of Polymeric Adhesives.

Enthalpic relaxation of silica–polyvinyl acetate nanocomposites

Enthalpy Relaxation of Liquid Crystalline Polymer with Cyanobiphenyl Group in the Side Chain: Analysis based on Configurational Entropy Model with the AG Expression

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