Strain recovery of post-yield compressed semicrystalline poly(butylene terephthalate)

Pegoretti, Alessandro; Pandini, Stefano; Riccò, T.

doi:10.1016/j.polymer.2006.06.020

Cited by 6 publications

(6 citation statements)

References 52 publications

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“…This irreversible recovery phenomenon, which was not observed in isostatically compacted specimens, is probably related to the (visco)plastic behavior of the amorphous and crystalline compound constituting the PTFE powder, and must not be mixed up with the standard recovery related to the viscoelastic behavior of most polymers. Different experimental techniques and modeling approaches have been used to tackle this complex phenomenon that may have various microscopic origins in different semicrystalline polymers (see for instance [33–36]). Different authors have observed, including in sintered PTFE [24, 36], or used in their micro–macro models, different microscopic phenomena induced by mechanical loading of the material such as crystalline phase change, rotation of the crystalline domains within the amorphous matrix, or tilts and slips within the crystalline phase.…”

Section: Results and Analysismentioning

confidence: 99%

“…Different experimental techniques and modeling approaches have been used to tackle this complex phenomenon that may have various microscopic origins in different semicrystalline polymers (see for instance [33–36]). Different authors have observed, including in sintered PTFE [24, 36], or used in their micro–macro models, different microscopic phenomena induced by mechanical loading of the material such as crystalline phase change, rotation of the crystalline domains within the amorphous matrix, or tilts and slips within the crystalline phase. To the authors' knowledge, very few experimental analyses have yet been dedicated to and published on such microscopic phenomena in PTFE green compacts, with the notable exception [37].…”

Section: Results and Analysismentioning

confidence: 99%

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Experimental identification of the deformation mechanisms during sintering of cold compacted polytetrafluoroethylene powders

Canto

Schmitt

Carvalho

et al. 2011

Polymer Engineering & Sci

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The influence of the cooling rate after melting on the crystalline weight fraction of pure poly(tetrafluoroethylene) (PTFE) was derived from differential scanning calorimetry tests. Specimens made of pure or filled PTFE were manufactured by isostatic or constrained uniaxial cold pressing, up to different values of the porosity. Dilatometry tests were carried out on these specimens while imposing various heating–cooling treatments. The deformations recorded during these tests strongly depend on the mode and level of compaction. The original procedures presented, herein, made it possible to identify that these macroscopic deformations, which are strongly anisotropic for uniaxially pressed specimens, result from the combination of different independent mechanisms. The mechanisms that were distinguished are reversible thermal expansion, void closure, crystalline to amorphous and vice versa transformations, and recovery, which were not observed for isostatically pressed specimens. It was also shown that, after being subjected to a standard sintering treatment, anisotropically pressed specimens still exhibit anisotropic crystallization strains. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

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Section: Results and Analysismentioning

confidence: 99%

Section: Results and Analysismentioning

confidence: 99%

Experimental identification of the deformation mechanisms during sintering of cold compacted polytetrafluoroethylene powders

Canto

Schmitt

Carvalho

et al. 2011

Polymer Engineering & Sci

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“…We emphasize that this function is at best an approximation for r . For one, there is (to the best of our knowledge) no general theory that predicts such a bilinear behavior for the residual strain, despite ample experimental evidence [19,12,17,22,23]. Moreover, we physically expect that a = 0, but as has been noted practical simulations often return small, non-zero values of r when → 0.…”

Section: Hyperbola Fits Of Residual Strainmentioning

confidence: 91%

“…2 and Refs. [12,17,22,23]. Moreover, they identified the onset of permanent deformation with the appearance of a non-zero slope in their r .…”

Section: Comparison With Experimentsmentioning

confidence: 99%

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Estimating yield-strain via deformation-recovery simulations

Patrone

Tucker

Dienstfrey

2017

Polymer

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In computational materials science, predicting the yield strain of crosslinked polymers remains a challenging task. A common approach is to identify yield as the first critical point of stress-strain curves simulated by molecular dynamics (MD). However, in such cases the underlying data can be excessively noisy, making it difficult to extract meaningful results. In this work, we propose an alternate method for identifying yield on the basis of deformation-recovery simulations. Notably, the corresponding raw data (i.e. residual strains) produce a sharper signal for yield via a transition in their global behavior. We analyze this transition by nonlinear regression of computational data to a hyperbolic model. As part of this analysis, we also propose uncertainty quantification techniques for assessing when and to what extent the simulated data is informative of yield. Moreover, we show how the method directly tests for yield via the onset of permanent deformation and discuss recent experimental results, which compare favorably with our predictions.

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Sequential Motion of 4D Printed Photopolymers with Broad Glass Transition

Inverardi

Pandini

Bignotti

et al. 2019

Macro Materials & Eng

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The term “4D printing” refers to the development of stimulus‐responsive structures through 3D printing of active smart materials, typically shape memory polymers. A noteworthy aim of this research field is to obtain objects able to display complex shape‐shifting motions, such as sequential transformations over time. In this work, this peculiar response is studied on a commercial photopolymer, printed by stereolithography and featuring, on the basis of its inherent broad glass transition, the so‐called “temperature‐memory effect” (TME). The TME, that is, a response in which the shape memory effect occurs on a region controlled by the deformation temperature, is studied in shape memory cycles where the deformation temperature is systematically varied, so to provide a correlation between deformation and recovery temperatures. This also allows to properly select two temperatures at which deforming a specimen along a multistep history, so as to finally separate each recovery process on the temperature and time scales. This sequential recovery is studied in double folded bars, with arms deformed at different temperatures, and on a properly designed self‐locking clamp. The obtained results are promising for the realization of smart temperature‐responsive structures printed with one single polymer and capable of multiple shape transformations.

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Strain recovery of post-yield compressed semicrystalline poly(butylene terephthalate)

Cited by 6 publications

References 52 publications

Experimental identification of the deformation mechanisms during sintering of cold compacted polytetrafluoroethylene powders

Experimental identification of the deformation mechanisms during sintering of cold compacted polytetrafluoroethylene powders

Estimating yield-strain via deformation-recovery simulations

Sequential Motion of 4D Printed Photopolymers with Broad Glass Transition

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