Thermal analysis of the double‐melting behavior of poly(<scp>L</scp>‐lactic acid)

Yasuniwa, Munehisa; Tsubakihara, Shinsuke; Sugimoto, Yuichi; Nakafuku, Chitoshi

doi:10.1002/polb.10674

Cited by 337 publications

(237 citation statements)

References 39 publications

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“…The double peak is explained in different ways [33]: (a) formation of a disordered alpha phase of PLA owing to the low crystallization temperature, (b) nucleation of more than one crystal structure and (c) different morphology of the lamellae formed prior to the heating process. Increasing the number of extrusions, the shape of the endotherms changes from a bimodal to an unimodal distribution, which might be attributed to the homogenization of crystals type and size dependant on chain shortening of the PLA [44,45]. In PLA + OM-HT samples bimodal distribution disappears after the first recycle.…”

Section: Resultsmentioning

confidence: 97%

Structure-properties relationships in melt reprocessed PLA/hydrotalcites nanocomposites

Scaffaro¹,

Sutera²,

Mistretta³

et al. 2017

Express Polym. Lett.

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Abstract. In this work the effect of multiple reprocessing was studied on molecular structure, morphology and properties of poly(lactic acid)/hydrotalcites (PLA/HT) nanocomposites compared to neat PLA. In addition, the influence of two different kinds of HT -organically modified (OM-HT) and unmodified (U-HT) -was evaluated. Thermo-mechanical degradation was induced by means of five subsequent extrusion cycles. The performance of the recycled materials was investigated by mechanical and rheological tests, differential scanning calorimetry (DSC), intrinsic viscosity measurements and SEM observation. The results indicated that the best morphology was achieved in the systems incorporating OM-HT. On increasing the extrusion reprocessing cycles, the properties showed behavior due to two opposite effects: i) chain scission due to thermo-mechanical degradation and ii) filler dispersion effect resulting from multiple processing. In particular, at low reprocessing cycles, both tensile and rheological properties seem to be mainly affected by HT dispersion, especially when OM-HT was added. After five reprocessing cycles, on the contrary, chain scission, i.e. thermo-mechanical degradation, dominated. As regards the effect of the presence of organic modifier in HT, the results indicated that this variable apparently did not affect the macroscopic performance of the nanocomposites, especially at high reprocessing cycles.

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Section: Resultsmentioning

confidence: 97%

Structure-properties relationships in melt reprocessed PLA/hydrotalcites nanocomposites

Scaffaro¹,

Sutera²,

Mistretta³

et al. 2017

Express Polym. Lett.

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“…Isto foi observado em outros estudos sendo fortemente dependentes da taxa de aquecimento [11] , sendo explicados pela ocorrência de efeitos competitivos de fusão e recristalização durante o processo de aquecimento. Cristais imperfeitos e pequenos [11] . Neste trabalho somente a taxa de 10 °C/min foi utilizada, e nestas condições este efeito esteve presente.…”

Section: Resultsunclassified

Estudo do comportamento térmico e mecânico do PLA modificado com aditivo nucleante e modificador de impacto

Pereira¹,

Morales²

2014

Polímeros

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Resumo: O poliácido lático (PLA) é, dentre os polímeros biodegradáveis, o que apresenta o maior potencial para substituição aos polímeros derivados do petróleo na indústria de embalagens. No entanto uma de suas principais limitações está na baixa estabilidade térmica dimensional. O presente trabalho apresenta um estudo da influência da utilização de dois aditivos: modificador térmico (nucleante) e modificador de impacto, na Temperatura de Distorção Térmica (HDT), no Ponto de Amolecimento Vicat (Vicat) e nas propriedades mecânicas do PLA. Os mecanismos de atuação destes aditivos foram estudados por alterações na temperatura de transição vítrea (Tg) e na cristalinidade medidas por calorimetria diferencial exploratória (DSC) em corpos de prova injetados sem e com tratamento de recozimento. Aplicou-se um planejamento experimental para tratamento estatístico dos dados. Os valores de HDT e de Vicat foram pouco alterados pela presença dos aditivos, embora tenha sido observado aumento nos valores do módulo elástico de tração. O tratamento de recozimento foi responsável pelo aumento tanto na HDT como na Vicat devido ao aumento no grau de cristalinidade. As curvas de DSC mostraram uma grande complexidade no comportamento térmico do PLA, sendo fortemente influenciado pelas condições de tratamento térmico. Palavras-chave: PLA, aditivos nucleantes, propriedades mecânicas, propriedades térmicas. Study of Mechanical and Thermal Behavior of PLA Modified with Nucleating Additive and Impact ModifierAbstract: Poly(lactic acid) (PLA) is the biodegradable polymer with greatest potential to replace petroleum-based polymers for the packaging industry. However one of its major limitations is the poor thermal dimensional stability. This paper presents a study of the influence of two additives: thermal modifier (nucleating) and impact modifier on the Heat Distortion Temperature (HDT), Vicat Softening Temperature (Vicat) and mechanical properties of PLA. The mechanism of these additives was evaluated by analyzing the glass transition temperature (Tg) and degree of crystallinity by Differential Scanning Calorimetry (DSC) in the samples with and without annealing treatment. An experimental design was applied for the statistical treatment of the data. The values of HDT and Vicat were slightly altered by the presence of additives, although the tensile elastic modulus increased. Annealing was responsible for the increase in HDT as well as in Vicat due to an increased degree of crystallinity. DSC curves showed a great complexity in the thermal behavior of PLA, being strongly influenced by the conditions of heat treatment.

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“…Other authors have explained double melting behavior with a melt-recrystallization model, where the low-temperature and high-temperature peaks in the DSC curve are attributed to the melting of some amount of the original crystals and to the melting of crystals formed through a melt-recrystallization process during the heating scan, respectively [33]. As lignin content increases, there is a greater contribution from the melting of major crystals to the specific melting enthalpy of the sample or from crystals formed through a melt-recrystallization process, which is implied by the increase in the higher temperature melting peak in Figure 8.…”

Section: Thermal Characterizationmentioning

confidence: 99%

Production and 3D printing processing of bio-based thermoplastic filament

2017

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-In this work, an extrusion-based 3D printing technique was employed for processing of biobased blends of Poly(Lactic Acid) (PLA) with low-cost kraft lignin. In Fused Filament Fabrication (FFF) 3D printing process, objects are built in a layer-by-layer fashion by melting, extruding and selectively depositing thermoplastic fibers on a platform. These fibers are used as building blocks for more complex structures with defined microarchitecture, in an automated, cost-effective process, with minimum material waste. A sustainable material consisting of lignin biopolymer blended with poly(lactic acid) was examined for its physical properties and for its melt processability during the FFF process. Samples with different PLA/lignin weight ratios were prepared and their mechanical (tensile testing), thermal (Differential Scanning Calorimetry analysis) and morphological (optical and scanning electron microscopy, SEM) properties were studied. The composition with optimum properties was selected for the production of 3D-printing filament. Three process parameters, which contribute to shear rate and stress imposed on the melt, were examined: extrusion temperature, printing speed and fiber's width varied and their effect on extrudates' morphology was evaluated. The mechanical properties of 3D printed specimens were assessed with tensile testing and SEM fractography.

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Thermal analysis of the double‐melting behavior of poly(L‐lactic acid)

Cited by 337 publications

References 39 publications

Structure-properties relationships in melt reprocessed PLA/hydrotalcites nanocomposites

Structure-properties relationships in melt reprocessed PLA/hydrotalcites nanocomposites

Estudo do comportamento térmico e mecânico do PLA modificado com aditivo nucleante e modificador de impacto

Production and 3D printing processing of bio-based thermoplastic filament

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