Effect of plastic deformation on the microstructure and properties of amorphous polycarbonate

G’Sell, C.; Bari, Hassan El; Pérez, Joseph; Cavaillé, J.Y.; Johari, G. P.

doi:10.1016/0921-5093(89)90174-3

Cited by 41 publications

(20 citation statements)

References 10 publications

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“…[32,33] A theory for nucleation of quasi-point defects with high molecular mobility [34] in glassy polymers and their coalescence into clusters (shear micro-domains) under loading was suggested in ref. [35,36] This concept is in qualitative agreement with a model of liquid-like regions [37] which treats shear micro-domains as molecular-scale lubricants accelerating cooperative motion of relaxing units. [1] Two shortcomings of this approach may be mentioned: (i) it does not distinguish the viscoelastic and viscoplastic responses of amorphous media and (ii) the model is confined to the qualitative description of anelastic deformations and it does not provide constitutive equations for the analysis of experimental data.…”

Section: Introductionsupporting

confidence: 61%

The Nonlinear Viscoelastic Response of Glassy Polymers Subjected to Physical Aging

Drozdov¹

2001

Macromol. Theory Simul.

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Section: Introductionsupporting

confidence: 61%

The Nonlinear Viscoelastic Response of Glassy Polymers Subjected to Physical Aging

Drozdov¹

2001

Macromol. Theory Simul.

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“…Reversal of the effects of physical ageing is known as rejuvenation. Equivalently, it has been observed that under various kinds of loading (G'sell et al, 1969;Aboulfaraj et al, 1994;Govaert et al, 2000) imparting plastic deformation to an aged polymer sample can reverse the effect of ageing. For example, Govaert et al (2000) has shown that when a cylindrical bar of polycarbonate is torqued to and fro and then subjected to a tensile test, the strain softening is almost completely removed from the stress-strain response.…”

Section: Introductionmentioning

confidence: 97%

Ageing and rejuvenation in glassy amorphous polymers

Mahajan

Estevez

Basu

2010

Journal of the Mechanics and Physics of Solids

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“…By extrapolating the dependence in Figure 12 to σ = 0, the E A (0) = 220 kJ mol −1 is obtained similar to the activation energy determined for unstrained PMMA using DSC 44 or the apparent activation energy for the contribution of the α-process to the plastic deformation of PMMA. 15,36 This observation may be related to the hypothesized 13 strain-induced polyamorphic phase transition changing both segment scale conformational and orientational distribution.…”

Section: ■ Results and Discussionmentioning

confidence: 85%

Temperature, Frequency, and Small Static Stress Dependence of the Molecular Mobility in Deformed Amorphous Polymers near Their Glass Transition

Ondreáš

Jančář

2015

Macromolecules

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For the first time, we report on using dynamic mechanical analysis (DMA) to directly follow molecular mobility in PMMA and PC deformed by small constant tensile stress (σ) over the temperature interval from T g − 60 K to T g + 60 K. At T α′ > T g , a pronounced secondary α′-relaxation was observed exhibiting larger frequency shift and stronger σ-dependence compared to the main α-relaxation. After reaching its maximum at approximately the T g , the strain rate was progressively reduced at the onset of the α′-relaxation, attaining its minimum value at approximately the T α′ . Above the T α′ , the strain rate increased gradually again, suggesting that mobility has again been enhanced. We ascribe the observed variation in mobility to the strain-induced transition of segments from less mobile into more mobile domains, resulting in the alteration of conformational and orientational distribution. The macroscopic deformation (ε) dependence of the transient modulus, defined to characterize the system stiffness between the α and α′ relaxation (Γ*(ε)) and above the α′-relaxation (Ω*(ε)), collapsed to a single linear master curve for Γ*(ε) and the nonlinear Ω*(ε) master curve. Our results seem to indicate that the observed α′-relaxation may be caused by the process of intrabasin jump diffusion of small portions of the backbone chain over the characteristic length scale smaller than or equal to the dynamic Kuhn segment length (l K ). The existence of the α′-relaxation may be a manifestation of the large strain-altered chain packing associated with the polyamorphic phase transition as the process accompanying yielding in polymer glasses. ■ INTRODUCTIONPolymer glasses are generally considered random packing of low and high density nanometer scale domains bound together by intra-and intermolecular forces. 1 Because of chain connectivity, local strain affects the degree of freedom of structural units, an effect not observed in molecular glasses. 1 Macroscopic deformation and temperature both alter the potential energy landscape and modify structural disorder, segmental mobility, and dynamic heterogeneity in polymer glasses. In a single step isothermal creep photobleaching experiment and MD simulation, it was shown 2−4 that deformation-induced segmental mobility correlates with strain rate, increasing at the onset of yielding and decreasing during postyield strain hardening. The reduced mobility during strain hardening was related to the segment scale thermally activated yielding processes, 5−9 supposedly coupled with the increase in rate of nonaffine segmental displacements represented by the increase of the effective stiffness length (Kuhn length, l K ) with deformation. 10 However, using a multistep creep photobleaching experiments, Lee et al. 11 found no correlation between strain rate and mobility, suggesting that most likely the connection between any simple mechanical variable and segmental mobility is much more complex than anticipated originally, 12,13 and despite significant progress, the understanding of this phenomeno...

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Effect of plastic deformation on the microstructure and properties of amorphous polycarbonate

Cited by 41 publications

References 10 publications

The Nonlinear Viscoelastic Response of Glassy Polymers Subjected to Physical Aging

The Nonlinear Viscoelastic Response of Glassy Polymers Subjected to Physical Aging

Ageing and rejuvenation in glassy amorphous polymers

Temperature, Frequency, and Small Static Stress Dependence of the Molecular Mobility in Deformed Amorphous Polymers near Their Glass Transition

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