Local and segmental motions of the mobile amorphous fraction in semi-crystalline polylactide crystallized under quiescent and flow-induced conditions

Monnier, Xavier; Chevalier, Laurence; Esposito, Antonella; Fernandez-Ballester, Lucia; Saiter, Allisson; Dargent, Éric

doi:10.1016/j.polymer.2017.08.021

Cited by 13 publications

(9 citation statements)

References 70 publications

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“…The decrease of the physical aging rate with increasing crystallinity degree has been reported for several semiecrystalline polymers, including polypropylene [59], poly (phenylene sulfide) [60], or PEEK [61]. Monnier et al [62] observed that the structural recovery functions between semiecrystalline PLA crystallized under quiescent or floweinduced conditions were similar, with an aging rate of 1.1 ± 0.1 J/decade, if rescaled to the MAF content. These results are consistent with ours.…”

Section: Influence Of the Constraint Nature On The Physical Aging Kinmentioning

confidence: 75%

Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry

Monnier

Nassar

Domenek

et al. 2018

Polymer

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The physical aging behavior of amorphous polylactide constrained against polystyrene in layers of 300 nm, thanks to the layeremultiplying coeextrusion process, was investigated by fastescanning calorimetry (FSC). By cooling down the sample from the liquid state to the glassy one at very fast scanning rates, it was possible to investigate the structural relaxation of the polymer glass at high temperatures for which the time needed to reach the equilibrium was shortened. Therefore it was possible to perform the study of physical aging in experimental conditions providing an expanded view of the structural relaxation for short aging times. Taking benefit of this property, it was highlighted that the aging kinetics of polylactide occurred significantly slower in the multilayer film, in comparison with a bulk amorphous film. The process of recovery in the multilayer system was found to occur at similar rates, or even slower, than in a threeelayer film in which polylactide reached its maximum extent of crystallinity. This was attributed to mobility hindrance that might be inherent to the extrusion conditions or associated with the presence of capped interfaces with polystyrene.

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Section: Influence Of the Constraint Nature On The Physical Aging Kinmentioning

confidence: 75%

Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry

Monnier

Nassar

Domenek

et al. 2018

Polymer

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“…We can envisage that the kinetic endotherm observed in our work is an enthalpy recovery peak that mostly arises out of the molecular orientation due to the shear exerted on the polymer jet below T g during the spinning process. Such recovery occurs only in the mobile amorphous fraction (MAF) and could not be attributed to the rigid amorphous fraction (RAF) or mesophase. , We will bring further evidence on the origin of the recovery peak and its relation to the structural features of ES fibers in Section .…”

Section: Resultsmentioning

confidence: 94%

On the Importance of Noncrystalline Phases in Semicrystalline Electrospun Nanofibers

Soleimani

Mazaheri

Pellerin

et al. 2021

ACS Appl. Polym. Mater.

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Tailoring the properties of electrospun fibers requires a detailed understanding and control of their microstructure. We investigate the structure/property relationships in fabrics of randomly aligned fibers of polylactide, a prevalent biopolymer, either as-spun or after annealing and solvent-induced crystallization. In-depth characterization by field-emission scanning electron microscopy (FESEM), wide-angle X-ray diffraction (WAXD), attenuated total reflection Fourier transform infrared (ATR-FTIR), and modulated temperature differential scanning calorimetry (MT-DSC) reveals that the as-spun fibers comprise crystalline and mesomorphic phases, as well as oriented but mobile amorphous chain segments. These chains are mostly responsible for the low-temperature cold crystallization and for the recovery endotherm around the glass transition, while the mesophase transforms into crystals with nearly zero enthalpy. Such behaviors are attributed to high molecular orientation, which is further evidenced by unveiling a fibrillar superstructure in nanofibers. The thermodynamics and structural evolution under different conditions are described from an energy landscape perspective. Finally, we propose a micromechanism, based on a modified supramolecular model, which helps to elucidate the fibers' molecular dynamics.

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“…The samples were quenched using liquid nitrogen prior to cutting to prevent ductile failure from the blade. A similar sampling approach was developed to observe the relaxation of FIC precursors in poly(lactic acid) using fast calorimetric techniques, but crystallization behaviors were not observed . Prior to placing the sample on the FSC chip, a thin layer of thermally stable silicone fluid (Wacker AK 60000) was applied to the surface of the chip to aid in heat transfer and to prohibit the sample from fusing to the chip.…”

Section: Methodsmentioning

confidence: 99%

Sensitivity of Polymer Crystallization to Shear at Low and High Supercooling of the Melt

et al. 2018

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Flow-induced crystallization (FIC) is a dominant mechanism of polymer self-assembly, but the process is poorly understood at high supercooling and under fast cooling conditions because of structural rearrangements that occur during slow heating and cooling conditions typically used for investigation. Incorporating fast-scanning chip calorimetry techniques, the influence that specific amounts of shear flow have on the subsequent crystallization of polyamide 66 over a wide range of temperatures, 85–240 °C, is determined. At high temperatures, heterogeneous nucleation dominates and crystallization rate increases with increasing shear. Low-temperature crystallization, driven by homogeneous nucleation, is not influenced by previous shear flow, but sheared samples are able to crystallize via the heterogeneous nucleation route at temperatures 15 K lower than unsheared materials. The magnitude of previous shear flow also dictates α-/γ-crystalline phase development and crystallization during cooling at rates below 200 K/s. This approach provides a route to develop important thermodynamic and kinetic insights that describe the crystallization behavior of many important polymers to enable the advanced engineering of polymer processing and injection molding applications, where practical cooling rates typically range between 10 K/s and 1000 K/s.

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Local and segmental motions of the mobile amorphous fraction in semi-crystalline polylactide crystallized under quiescent and flow-induced conditions

Abstract: Local and segmental motions of the mobile amorphous fraction Local and segmental motions of the mobile amorphous fraction in semi-crystalline polylactide crystallized under quiescent and

Cited by 13 publications

References 70 publications

Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry

Reduced physical aging rates of polylactide in polystyrene/polylactide multilayer films from fast scanning calorimetry

On the Importance of Noncrystalline Phases in Semicrystalline Electrospun Nanofibers

Sensitivity of Polymer Crystallization to Shear at Low and High Supercooling of the Melt

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