Principal features of structural relaxation in glassy polymers. A Review

Mijović, Jovan; Nicolais, L.; D’Amore, Alberto; Kenny, J. M.

doi:10.1002/pen.760340502

Cited by 56 publications

(30 citation statements)

References 53 publications

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“…More on the TNM model limitations can be found e.g. in [37][38][39][40][41][42], where several attempts for improvement of relaxation phenomenology can also be found. Nevertheless, the TNM model is considered a standard in the field of structural relaxation; thus, all theoretical curves shown in this work were calculated using TNM model without any extensions.…”

Section: Discussionmentioning

confidence: 99%

Enthalpy relaxation of selenium observed by fast scanning calorimetry

et al. 2015

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Section: Discussionmentioning

confidence: 99%

Enthalpy relaxation of selenium observed by fast scanning calorimetry

et al. 2015

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“…More references and examples on the TNM model limitations can be found in Refs. [183,184,185,186,187].…”

Section: Limitationsmentioning

confidence: 99%

Relaxation and physical aging in network glasses: a review

Micoulaut

2016

Rep. Prog. Phys.

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Abstract. Recent progresses in the description of glassy relaxation and ageing are reviewed for the wide class of network-forming materials such as GeO 2 , Ge x Se 1−x , silicates (SiO 2 -Na 2 O) or borates (B 2 O 3 -Li 2 O), all of them having an important usefulness in domestic, geological or optoelectronic applications. A brief introduction of the glass transition phenomenology is given, together with the salient features that are revealed both from theory and experiments. Standard experimental methods used for the characterization of the slowing down of the dynamics are reviewed. We then discuss the important role played by aspect of network topology and rigidity for the understanding of the relaxation of the glass transition, while also permitting analytical predictions of glass properties from simple and insightful models based on the network structure. We also emphasize the great utility of computer simulations which probe the dynamics at the molecular level, and permit to calculate various structure-related functions in connection with glassy relaxation and the physics of ageing which reveals the off-equilibrium nature of glasses. We discuss the notion of spatial variations of structure which leads to the picture of "dynamic heterogeneities", and recent results of this important topic for network glasses are also reviewed.PACS numbers: 61.43. Fs, 64.70.kj Relaxation and physical ageing in network glasses 2 Figure 1. Typical network-forming glasses: a) A stoichiometric glass former (SiO 2 , B 2 S 3 ) whose structure and network connectivity can be altered by the addition (b) of 2-fold coordinated atoms (usually chalcogens, S, Se) that lead to cross-linked chains. The structure can also be depolymerized (c) by the addition of a network modifier (alkali oxides or chalcogenides, Na 2 O, Li 2 S, etc.). Glassy dynamics depends strongly on the network topology, i.e. the way bonds and angles arrange to lead to a connected atomic network. Note that only chalcogenides can produce a mixture of these three kinds of basic networks, e.g. (1-x)Ge y Se 1−y -xAg 2 Se [2], and for the latter system x=0 corresponds to case (b), y=33% corresponds to case (c), and both conditions together (x=0,y=33 %) to case (a).

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“…Some reviews of the principal phenomenological models of structural relaxation, such as the one proposed by Narayanaswamy [4] and then by Moynihan et al [5] (the NM model), the Scherer-Hodge (SH) model [7,8] or the Kovacs-Aklonis-Hutchinson-Ramos (KAHR) model [13] are available in literature [1,2,14] and also recent discussions involving this type of models can be found (see for example [15][16][17]). Several works have shown that the NM or SH models fail to reproduce the DSC thermograms measured after different thermal histories using a single set of model parameters [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Enthalpy relaxation studies in polymethyl methacrylate networks with different crosslinking degrees

Alves

Ribelles

Mano

2005

Polymer

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Structural relaxation of PMMA networks with distinct crosslink density has been studied by differential scanning calorimetry (DSC). The crosslinking agent used was ethylene glycol dimethacrylate (EGDMA). The experiments were carried out on heating after the samples have been subjected to distinct thermal histories, namely isothermal stages at different temperatures below the glass transition temperature for distinct times and cooling at different rates. These studies revealed a broadening of the glass transition with increasing crosslinking degree due to the constraints imposed by the crosslinks and suggested the presence of crosslink heterogeneity in the networks. A phenomenological model based on the configurational entropy concept was used to simulate the structural relaxation phenomenon and to evaluate the temperature dependence and distribution of the relaxation times of the conformational rearrangements for these networks. The agreement between the experimental results and the simulated thermograms was quite satisfactory.In addition, the kinetic fragility of the networks was evaluated from the results corresponding to the thermal treatments at distinct cooling rates. It was found an increase of the fragility index m with increasing crosslinking degree. q

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Principal features of structural relaxation in glassy polymers. A Review

Cited by 56 publications

References 53 publications

Enthalpy relaxation of selenium observed by fast scanning calorimetry

Enthalpy relaxation of selenium observed by fast scanning calorimetry

Relaxation and physical aging in network glasses: a review

Enthalpy relaxation studies in polymethyl methacrylate networks with different crosslinking degrees

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