Evidence of two mobile amorphous phases in semicrystalline polylactide observed from calorimetric investigations

Delpouve, Nicolas; Arnoult, M.; Saiter, Allisson; Dargent, Éric; Saiter, Jean‐Marc

doi:10.1002/pen.23657

Cited by 40 publications

(51 citation statements)

References 57 publications

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“…According to the literature, this observation can be ascribed to a confinement effect, as reported for other semicrystalline polymers. 32,69,71 Rev-C p curves in Figure 5 also point out that the predictions made on the basis of a simple two-phase model (X MA 2ph = 0.34 for Melt isoT Cryst sample and X MA 2ph = 0.56 for Cold isoT Cryst sample) are unfulfilled in the region of the glass transition and that the RAF must be considered. For example, according to the ΔC p (T g ) values estimated from 75 poly(trimethylene terephthalate) (PTT), 8 and poly(3-hydroxybutyrate) (P3HB).…”

Section: Articlementioning

confidence: 92%

From a Three-Phase Model to a Continuous Description of Molecular Mobility in Semicrystalline Poly(hydroxybutyrate-co-hydroxyvalerate)

et al. 2016

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In most cases, a three-phase model consisting of crystalline domains surrounded by rigid amorphous areas dispersed in the mobile amorphous phase is required and eventually sufficient to accurately describe the microstructure of semicrystalline polymers. This work shows that the microstructure developed by poly(hydroxybutyrate-co-hydroxyvalerate) by cold crystallization is better described by a complex two-phase model in which the boundaries of the crystalline domains and the surrounding amorphous environment form a “continuum of mobility”. This concept can be extended to a wide range of semicrystalline polymers. When the crystalline and the amorphous phases are strongly coupled, the rigid and mobile amorphous fractions are hardly fractionated, and the whole noncrystalline phase should be rather depicted as continuum with a broad distribution of the relaxation times associated with the glass transition. Such a depiction of the amorphous phase allows taking into account any modification of the mobility landscape with time, which can be evidenced as the progressive spreading of the relaxation functions. From a practical point of view, the rigidification of the “continuum of mobility” upon storage in conditions of cold crystallization could be considered as a cause of the progressive embrittlement sometimes observed in semicrystalline materials during physical aging and would be explained by a redistribution of the relaxation times translated in terms of relaxation temperatures

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Section: Articlementioning

confidence: 92%

From a Three-Phase Model to a Continuous Description of Molecular Mobility in Semicrystalline Poly(hydroxybutyrate-co-hydroxyvalerate)

et al. 2016

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“…PLA can crystallize in a, a 0 , b and c forms [6], and crystal perfection, recrystallization and change of modification may result in multiple peaks during heating and sometimes also during crystallization [6]. Even the amorphous phase of semicrystalline PLA has a complicated structure; it is claimed to contain three types of amorphous molecules: the rigid amorphous fraction, the interspherulitic mobile amorphous phase and the intraspherulitic mobile amorphous phase [31].…”

Section: Introductionmentioning

confidence: 98%

Physical ageing and molecular mobility in PLA blends and composites

Müller

Imre

Bere

et al. 2015

J Therm Anal Calorim

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Poly(lactic acid) (PLA) blends and composites were prepared from thermoplastic starch, poly(butyleneadipate-co-terephtalate), polycarbonate, wood flour and CaSO 4 in a wide range of compositions. The thermal transitions of PLA were studied by differential scanning calorimetry. The detailed analysis of the transitions of PLA/thermoplastic starch blends indicated that they all are determined by the molecular mobility of PLA chains. Blending changes molecular mobility, and thus it often decreases glass transition temperature and modifies the extent of enthalpy relaxation. All other transitions and characteristics, i.e. cold crystallization, melting and the corresponding enthalpies, change accordingly. Increased molecular mobility accelerates also the physical ageing of the polymer. The interaction between PLA and the various components used for modification changed in a wide range, but no direct correlation was found between the strength of interaction and molecular mobility.

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“…For an equivalent path of crystallization, T g was higher when crystallizing at 85 C. The shift of T g towards higher values upon crystallization is characteristic of the constrained amorphous phase between crystalline lamellae, which relaxes only at higher temperatures [19,20]. Among crystallized samples, it has been shown that T g also shifts to higher temperatures when the crystallization conditions did not allow a correct decoupling between the amorphous and the crystalline phase [26].…”

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confidence: 98%

“…The values of C p glass Ta and C p liquid Ta were obtained by prolonging the glass and liquid lines to dynamic glass transition temperature after normalization to the MAF content [18]. When the crystallization is not performed to its maximum extent, the MAF splits into intra-and inter-spherulitic amorphous regions and calorimetric measurements can show two separate signatures within the glass transition temperature range [20]. To overcome the issues related to such a complex molecular mobility landscape, the investigation of the CRR size was limited to the samples having reached their maximum degree of crystallinity.…”

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Multi-scale analysis of the impact of polylactide morphology on gas barrier properties

Nassar

Guinault

Delpouve

et al. 2017

Polymer

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scale analysis of the impact of polylactide morphology on gas barrier properties. Polymer, Elsevier, 2017, 108, pp.163-172. 10.1016/j.polymer.2016 Multi-scale analysis of the impact of polylactide morphology on gas barrier properties Samira Fernandes Nassar t r a c tSemicrystalline polylactide (PLA) films with controlled morphology were produced by thermal crystallization to optimize the oxygen barrier properties. The crystalline morphology of PLA at the scales of the lamella and the spherulite was investigated and the mobile amorphous phase dynamics were studied. The crystalline morphology had a negligible impact on the oxygen diffusion coefficient. The occurrence of a rigid amorphous fraction (RAF) in the amorphous phase due to its insufficient decoupling from the crystalline phase provided an accelerated pathway for diffusion, though. As a conclusion, for reaching optimal barrier properties, semicrystalline PLA should be pre-nucleated and rapidly crystallized from the glass in the a-polymorph in the aim to reach a high crystallinity degree and decoupling of the amorphous and the crystalline phase. These recommendations can benefit to industry for the optimization of PLA annealing treatments.

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Evidence of two mobile amorphous phases in semicrystalline polylactide observed from calorimetric investigations

Cited by 40 publications

References 57 publications

From a Three-Phase Model to a Continuous Description of Molecular Mobility in Semicrystalline Poly(hydroxybutyrate-co-hydroxyvalerate)

From a Three-Phase Model to a Continuous Description of Molecular Mobility in Semicrystalline Poly(hydroxybutyrate-co-hydroxyvalerate)

Physical ageing and molecular mobility in PLA blends and composites

Multi-scale analysis of the impact of polylactide morphology on gas barrier properties

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