Dynamic–mechanical properties of modified poly(ethylene‐co‐vinyl acetate)

Barbosa, Roseane Moreira Sampaio; Neto, Ricardo Baumhardt; Mauler, Raquel Santos; Gorga, Carlos José Perez; Schneider, C.; Simanke, Adriane G.

doi:10.1002/app.21883

Cited by 3 publications

(2 citation statements)

References 22 publications

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“…Complexity of the structure of EVA copolymer, especially the crystallinity, has been a subject of intense research. While some research focused on the nature of change in crystallinity and microstructure as the VA content varies, ,, others studied its effect on the mechanical and dielectric properties. − Two types of crystalline structures, with different crystalline lamellae and morphologies, were attributed to EVA structures, with one type obeying Flory’s general theory of copolymer crystallization and the other disregarding the theory when VA content is increased. , …”

Section: Introductionmentioning

confidence: 99%

“…Because of the presence of crystalline microstructures, a three-phase model, comprising fully crystalline regions with only polyethylene units, interfacial regions with coexisting VA and crystallized polyethylene units, and complex amorphous regions with coexisting VA and noncrystallized polyethylene units, has been presented for the structure of EVA copolymers. , The effect of changes in the crystallinity and microstructures on the physical properties of EVA copolymers were actively investigated by probing the dynamics of the copolymer using DSC, ,, 13 C NMR spectroscopy, , dynamic mechanical analysis (DMA) and dielectric spectroscopy, ,,− and fluorescence spectroscopy, , to name some.…”

Section: Introductionmentioning

confidence: 99%

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Study of the Dynamic Heterogeneity in Poly(ethylene-ran-vinyl acetate) Copolymer by Using Broadband Dielectric Spectroscopy and Electrostatic Force Microscopy

et al. 2013

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Dynamic heterogeneities in ethylene−vinyl acetate (EVA) random copolymers were studied using broadband dielectric spectroscopy (BDS) over a broad frequency and temperature range. BDS data for EVA copolymers show relatively broad spectra extending over several frequency decades, which make interpretation of the data complicated. Thus, microscopic dielectric characterizations of the samples were done using single pass electrostatic force microscopy (SP-EFM) images. From these experiments two distinct dielectric contributions were found in the semicrystalline samples. Dielectric spectra of EVA copolymers were fitted using a model based on the SP-EFM images. According to this analysis, the broad dielectric responses of semicrystalline EVA copolymers were constituted from two dielectrically active phases, referred to as the constrained and nonconstrained phases, exhibiting different segmental relaxations. In the constrained phase, vinyl acetate (VA) motions were greatly restricted by crystalline microstructures, whereas in the nonconstrained phase, VA monomers were assumed to be completely free from crystalline effect. The glass transition temperature derived from the dynamics of the VA segments in the constrained phase was found to correspond well with that determined from DSC representing the overall amorphous phase in the more crystallized state. Moreover, crystallinity of the sample obtained using DSC was found to follow a similar variation with temperature to that of the dielectric relaxation strength of the constrained phase of the copolymers. However, at the earlier stage of crystallization, where crystallinity increases rapidly, the dielectric relaxation remains insensitive to it.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Study of the Dynamic Heterogeneity in Poly(ethylene-ran-vinyl acetate) Copolymer by Using Broadband Dielectric Spectroscopy and Electrostatic Force Microscopy

et al. 2013

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Segmental mobility and glass transition of poly(ethylene-vinyl acetate) copolymers: Is there a continuum in the dynamic glass transitions from PVAc to PE?

Puente

Rijal

Delbreilh

et al. 2015

Polymer

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A Saiter, et al.. Segmental mobility and glass transition of poly(ethylene-vinyl acetate) copolymers : Is there a continuum in the dynamic glass transitions from PVAc to PE?. Polymer, Elsevier, 2015, 76, pp.213-219. 10.1016/j.polymer.2015 The segmental dynamics of amorphous poly(ethylene-vinyl acetate) copolymers (from PVAc to EVA50) were studied. In that sample set with similar backbone stiffness and different amount of dipoles, the dynamic glass transition was investigated by Modulated Temperature Differential Scanning Calorimetry and Broadband Dielectric Spectroscopy measurements. A decrease of the cooperativity length scale was obtained with the vinyl acetate (VAc) content decreasing. On the other hand, there was no modification of the temperature dependence of the relaxation time. Thus, the fragility value is quite constant whatever the VAc content. These results show that fragility and cooperativity have two different origins. An extrapolation to nonconstrained polyethylene amorphous phase was proposed and new glass transition temperature and fragility values were determined. Highlights 1.Amorphous phase mobility is studied for poly(ethylene-vinyl acetate) copolymers 2.Fragility is constant from PVAc to EVA50 while cooperativity length decreases 3.New extrapolated T g and fragility values are proposed for PE 4.Fragility and cooperativity are not governed by the same macromolecular properties Keywords Amorphous phase, dynamic glass transition, poly(ethylene-vinyl acetate) . Therefore, structural relaxation temperature dependences can be defined as Super-Arrhenius, due to a possible behavior between two extreme limits: "strong" glass forming liquids for which the viscosity variations (or relaxation time) are very slow and follow an Arrhenius law, and the "fragile" glass forming liquids for which a very abrupt and steep non-Arrhenian variations can be observed.The fragility index (m) quantifies the steepness of the temperature dependence of the relaxation time () close to T g (defined at τ = 100s) and can be calculated as follows:The fragility values for different materials such as polymers, metallic glasses, organic and inorganic ionic glasses, and for small organic molecules were summarized Several approaches have been proposed to explain the correlation between the fragility and the molecular mobility near T g [10,16,17]. According to the theory proposed by Adam and Gibbs [18], it is well accepted that the α relaxation process is cooperative in nature: a structural unit can move only if a certain number of neighboring structural units move also. Besides, the molecular motions are mainly governed by the intermolecular interactions having important effects in the viscous slowing down of molecular dynamics when the glass-forming liquid is cooled-down close to T g . Thus, the notion of Cooperative Rearranging Region (CRR) was introduced, and the CRR size can be estimated according to different models and theories in terms of characteristic length scale or in terms of structural unit number [16,19-22]. Accordi...

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Comprehensive investigation into the thermal rheological behavior and relaxation characteristic of single/composite polymers in laminated glass

Xie,

Yang,

Zhao

et al. 2024

Thin-Walled Structures

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Dynamic–mechanical properties of modified poly(ethylene‐co‐vinyl acetate)

Cited by 3 publications

References 22 publications

Study of the Dynamic Heterogeneity in Poly(ethylene-ran-vinyl acetate) Copolymer by Using Broadband Dielectric Spectroscopy and Electrostatic Force Microscopy

Study of the Dynamic Heterogeneity in Poly(ethylene-ran-vinyl acetate) Copolymer by Using Broadband Dielectric Spectroscopy and Electrostatic Force Microscopy

Segmental mobility and glass transition of poly(ethylene-vinyl acetate) copolymers: Is there a continuum in the dynamic glass transitions from PVAc to PE?

Comprehensive investigation into the thermal rheological behavior and relaxation characteristic of single/composite polymers in laminated glass

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