Effect of crystalline forms (α′ and α) of poly(lactic acid) on its mechanical, thermo-mechanical, heat deflection temperature and creep properties

Tábi, Tamás; Hajba, Sándor; Kovács, József

doi:10.1016/j.eurpolymj.2016.07.024

Cited by 116 publications

(97 citation statements)

References 44 publications

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“…The lower temperature melting peak shifted toward a higher temperature and became more endothermic with increase of the annealing temperature, suggesting that at higher annealing temperatures the predominant crystal form developed was the α, which is in agreement with the literature . Furthermore, this peak was found to be endothermic for LL600 and LL650 crystallized at 140 °C.…”

Section: Resultssupporting

confidence: 89%

Effect of the annealing procedure and the molecular weight on the crystalline phase morphology and thermal properties of polylactide

Hortós

Anakabe

Arrillaga

et al. 2019

Polymer International

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The thermomechanical properties of poly(lactide) (PLA) are strongly related to its semicrystalline microstructure and morphology. Thermal annealing is a strategy to improve the crystallinity of PLA. However, the different techniques and specimen types needed for each kind of characterization could lead to misleading conclusions. In this work, annealed samples of three PLA grades with different molecular weights were studied by DSC, wide angle X‐ray scattering and polarized optical microscopy (POM) and the results are related to their thermomechanical and impact properties. Special focus is put on the POM results obtained by different approaches and the suitability of each of them to be related to the thermomechanical properties. By annealing medium molecular weight PLA specimens at 140 °C an important increase of the heat distortion temperature was obtained, which was not related to the spherulite size but to the combination of high crystallinity degree together with high α/α′ crystal type ratio. However, the impact properties of annealed PLA decreased with increase in the annealing temperature according to an increment in crystallinity and in the α/α′ crystal ratio. © 2019 Society of Chemical Industry

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Section: Resultssupporting

confidence: 89%

Effect of the annealing procedure and the molecular weight on the crystalline phase morphology and thermal properties of polylactide

Hortós

Anakabe

Arrillaga

et al. 2019

Polymer International

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“…PLLA samples annealed between 80 and 120 °C display practically the same crystallinity of 40%–42%, but the HDT markedly increases from 97 °C to 140 °C. Since in this temperature range, related to the low heating rate of 2 K min –1 on approaching the isothermal annealing step and the rather long annealing time of 1 h, conversion of α′‐ into α‐crystals was detected by calorimetry, but no significant difference in crystallinity, the sudden rise in HDT can be directly linked to the varied crystal structure . The HDT is in direct correlation with the storage modulus which, measured by dynamic‐mechanical analysis, was also found to increase with the α‐/α′‐crystal ratio .…”

Section: Mechanical Properties and Barrier Properties Of Plla Containmentioning

confidence: 86%

“…Since in this temperature range, related to the low heating rate of 2 K min –1 on approaching the isothermal annealing step and the rather long annealing time of 1 h, conversion of α′‐ into α‐crystals was detected by calorimetry, but no significant difference in crystallinity, the sudden rise in HDT can be directly linked to the varied crystal structure . The HDT is in direct correlation with the storage modulus which, measured by dynamic‐mechanical analysis, was also found to increase with the α‐/α′‐crystal ratio . The latter can also be related to the increased Young's modulus observed in PLLA containing a higher α/α′ fraction …”

Section: Mechanical Properties and Barrier Properties Of Plla Containmentioning

confidence: 87%

“…The heat deflection temperature (HDT) and creep properties of injection‐molded PLLA, subjected to post‐production annealing in the temperature range 80–140 °C, i.e. with varied ratios of α′‐ and α‐crystals, were also investigated . Figure illustrates the crystallinity dependence of the HDT of PLLA for samples annealed at various temperatures and times.…”

Section: Mechanical Properties and Barrier Properties Of Plla Containmentioning

confidence: 99%

“…Heat deflection temperature (HDT) plotted as a function of crystallinity for PLLA annealed at 80 °C for various times and at various temperatures from 80 to 140 °C for 1 h. Adapted from reference , Copyright (2016), with permission from Elsevier.…”

Section: Mechanical Properties and Barrier Properties Of Plla Containmentioning

confidence: 99%

See 2 more Smart Citations

Influence of α′‐/α‐crystal polymorphism on properties of poly(l‐lactic acid)

Lorenzo

Androsch

2018

Polymer International

109

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Poly(l‐lactic acid) (PLLA) is a biodegradable and biocompatible thermoplastic polyester produced from renewable sources, widely used for biomedical devices, in food packaging and in agriculture. It is a semicrystalline polymer, and as such its properties are strongly affected by the developed semicrystalline morphology. As a function of the crystallization temperature, PLLA can form different crystal modifications, namely α′‐crystals below about 120 °C and α‐crystals at higher temperatures. The α′ modification is therefore of special importance as it may be the preferred polymorph developing at processing‐relevant conditions. It is a metastable modification which typically transforms into the more stable α‐crystals on annealing at elevated temperature. The structure, kinetics of formation and thermodynamics of α′‐ and α‐crystals of PLLA are reviewed in this contribution, together with the effect of α′‐/α‐crystal polymorphism on the properties of PLLA. © 2018 Society of Chemical Industry

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Thermal behavior of extruded and injection‐molded poly(lactic acid)–talc engineered biocomposites: Effects of material design, thermal history, and shear stresses during melt processing

Barletta

Pizzi

Puopolo

et al. 2017

J of Applied Polymer Sci

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Reinforced biocomposites were compounded by the reactive extrusion of poly(lactic acid) (PLA) and chemically modified microlamellar talcs. Talc was functionalized by the hydrolysis and condensation reaction of its surface hydroxyl groups with different kinds of organosilanes, namely, 3‐aminopropyl triethoxysilane and (3‐glycidoxypropyl)trimethoxysilane, and commercially available tri‐isocyanates, namely, Bayhydur 3100 and Desmodur 3900, which feature hydrophilic and hydrophobic behaviors, respectively. PLA–talc biocomposites were also compounded by the addition of two types of reactive biodegradable compatibilizing agents, namely, maleic anhydride and glycidyl methacrylate modified PLA. The resulting compounds were melt‐processed by injection molding to get flat substrates with different formulations. The thermal responses of the extruded compounds and injection‐molded items, specifically the first and second thermal transitions, were analyzed by differential scanning calorimetry. In particular, the influence of the different material formulations, their thermal history, and/or shear stress in single‐ or multiple‐stage heating and/or melt processing on the glass transition, crystallinity, and melting behavior of the biocomposites was investigated. The experimental findings revealed that the macroscopic thermal response of the compounds (i.e., extruded pellets) and substrates (i.e., injection‐molded flat slabs) manufactured by the melt processing of the available formulations was controlled and significantly improved by the fine‐tuning of the chemical (i.e., reaction mechanisms, chemical bonds) and physical interactions (i.e., steric hindrances, physical bonds) among the modified talc, PLA, and compatibilizing agents. These results are of great practical importance and open up broader scenarios for the industrial application of biopolymers and biocomposites, specifically in all of those consumer goods where thermal stability and the preservation of mechanical performance at moderate and high temperatures of the materials are pivotal. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45179.

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Effect of crystalline forms (α′ and α) of poly(lactic acid) on its mechanical, thermo-mechanical, heat deflection temperature and creep properties

Abstract: Effect of crystalline forms (α' and α) of Poly(lactic acid) on its mechanical, thermo-mechanical, heat deflection temperature and creep properties

Cited by 116 publications

References 44 publications

Effect of the annealing procedure and the molecular weight on the crystalline phase morphology and thermal properties of polylactide

Effect of the annealing procedure and the molecular weight on the crystalline phase morphology and thermal properties of polylactide

Influence of α′‐/α‐crystal polymorphism on properties of poly(l‐lactic acid)

Thermal behavior of extruded and injection‐molded poly(lactic acid)–talc engineered biocomposites: Effects of material design, thermal history, and shear stresses during melt processing

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