Cold crystallization and multiple melting behavior of poly(l-lactide) in homogeneous and in multiphasic epoxy blends

Calafel, M. Itxaso; Remiro, P. M.; Cortázar, M.; Calahorra, M. E.

doi:10.1007/s00396-009-2156-3

Cited by 30 publications

(19 citation statements)

References 29 publications

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“…This bimodal melting peak was induced when the less perfect crystals have enough time to melt and reorganize into crystals with higher structural perfection, and later remelt at higher temperature 21. PLA can crystallize in several polymorphic forms, that is, α, β, and γ forms, depending on the preparation conditions 22. A double melting endotherm was often observed in PLA and depending on the crystallization temperature 23.…”

Section: Resultsmentioning

confidence: 99%

Mechanical, thermal, and morphological properties of injection molded poly(lactic acid)/SEBS‐g‐MAH/organo‐montmorillonite nanocomposites

Leu

Ishak

Chow

2011

J of Applied Polymer Sci

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Poly(lactic acid)/organo-montmorillonite (PLA/OMMT) nanocomposites toughened with maleated styrene-ethylene/butylene-styrene (SEBS-g-MAH) were prepared by melt-compounding using co-rotating twin-screw extruder followed by injection molding. The dispersibility and intercalation/exfoliation of OMMT in PLA was characterized using X-ray diffraction and transmission electron microscopy (TEM). The mechanical properties of the PLA nanocomposites was investigated by tensile and Izod impact tests. Thermogravimetric analyzer and differential scanning calorimeter were used to study the thermal behaviors of the nanocomposite. The homogenous dispersion of the OMMT silicate layers and SEBS-g-MAH encapsulated OMMT layered silicate can be observed from TEM. Impact strength and elongation at break of the PLA nanocomposites was enhanced significantly by the addition of SEBS-g-MAH. Thermal stability of the PLA/OMMT nanocomposites was improved in the presence of SEBS-g-MAH.

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Section: Resultsmentioning

confidence: 99%

Mechanical, thermal, and morphological properties of injection molded poly(lactic acid)/SEBS‐g‐MAH/organo‐montmorillonite nanocomposites

Leu

Ishak

Chow

2011

J of Applied Polymer Sci

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“…Besides, another possible interpretation was due to the phase transition from a 0 -form crystal to a one and the melting of the as-transformed a crystals. Obviously, there exist more or less divergences among these different melting mechanisms, and up to now, no consensus has been reached as for the exact origin of multiple melting behavior of PLLA [45][46][47][48][49]. Therefore, a further investigation of the melting behavior of PLLA is needed to deeply understand the origin of this phenomenon.…”

Section: Introductionmentioning

confidence: 94%

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

Song

Chen

Wei

et al. 2012

J Therm Anal Calorim

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The polymorphous crystallization and multiple melting behavior of poly(L-lactic acid) (PLLA) with an optical purity of 92 % were investigated after isothermally crystallized from the melt state by wide-angle X-ray diffraction and differential scanning calorimetry. Owing to the low optical purity, it was found that the disordered (a 0 ) and ordered (a) crystalline phases of PLLA were formed in the samples crystallized at lower (\95°C) and higher (C95°C) temperatures, respectively. The melting behavior of PLLA is different in three regions of crystallization temperature (T c ) divided into Region I (T c \ 95°C), Region II (95°C B T c \ 120°C), and Region III (T c C 120°C). In Region I, an exothermic peak was observed between the low-temperature and high-temperature endothermic peaks, which results from the solid-solid phase transition of a 0 -form crystal to a one. In Region II, the double-melting peaks can be mainly ascribed to the melting-recrystallization-remelting of less stable a crystals. In Region III, the single endotherm shows that the a crystals formed at higher temperatures are stable enough and melt directly without the recrystallization process during heating.

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“…En este sentido la mezcla epoxy/PHB presenta algunos puntos en común con el sistema epoxy mezclado con PLLA, el cual es un polímero biodegradable sumamente estudiado. Sin embargo, una diferencia entre el PHB y el PLLA, la cual puede tener implicancias respecto al tipo de uso de ambos polímeros es que la T g del PLLA es de aproximadamente 61.7 °C [7] , considerablemente superior a la del PHB de 3 °C.…”

Section: Discussionunclassified

“…En los últimos años un importante número de trabajos han sido desarrollados en mezclas epoxy con un polímero biodegradable u obtenido de la biomasa, por ejemplo ácido Poli (L-láctico) (PLLA) [3] . Una característica típica de estos polímeros es que en general son semicristalinos, por lo que los procesos que se desarrollan durante el curado son más complejos ya que la separación de fases y la cristalización pueden ocurrir a la vez [7] . En particular, el poli-3-hidroxibutirato (PHB) es un polímero biodegradable obtenido de fuentes naturales y tiene características que posibilitan su uso para reemplazar a polímeros obtenidos del petróleo.…”

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Separación de fases y cristalinidad en mezclas epoxy/poli-3-hidroxibutirato

Tognana¹,

Salgueiro²,

Silva³

2013

Polímeros

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CONICETResumen: En este trabajo se estudiaron mezclas epoxy/poli-3-hidroxibutirato (PHB) en dos proporciones distintas 90/10 y 85/15. Para ello se prepararon muestras sometiéndolas a temperaturas de 80 °C y 120 °C, a efectos de producir el curado del epoxy. Se analizó la separación de fases y la cristalización del PHB mediante microscopía óptica y calorimetría diferencial de barrido. Asimismo la estructura lamelar del PHB se caracterizó mediante dispersión de rayos X de bajo ángulo. Se encontraron diferencias significativas entre las dos proporciones estudiadas; mientras que la muestra 90/10 presenta miscibilidad, la muestra 85/15 indica una separación de fases. Asimismo se encontró que, sobre todo para la muestra 90/10, el epoxy afecta considerablemente la estructura lamelar del PHB. Los resultados se analizaron en términos de la competencia entre los procesos de cristalización y separación de fases. Palabras clave: Mezclas poliméricas, epoxy, PHB, cristalización. Phase Separation and Crystallinity in Epoxy/poly-3-hydroxybutyrate BlendsAbstract: In this work, epoxy/poly-3-hydroxybutyrate (PHB) blends in two different proportions, 90/10 and 85/15, were studied. For this purpose, the samples were submitted to 80 °C and 120 °C for the curing process of epoxy. The phase separation and the crystallization were analyzed using optical microscopy and differential scanning calorimetry. Likewise, the lamellar structure of PHB was characterized using small angle X-ray scattering. Significant differences between the two proportions studied were found; while the 90/10 sample presents miscibility, the 85/15 sample indicates a phase separation. Besides, the lamellar structure of PHB is affected due to the epoxy, mainly in the 90/10 sample. The results were analyzed on the basis of the competition between crystallization and phase separation processes. Keywords: Blend, epoxy, PHB, crystallization. IntroducciónLos polímeros termoestables y en particular los epoxy son frecuentemente mezclados con diferentes tipos de elastómeros o termoplásticos con el fin de mejorar algunas de sus propiedades mecánicas, en particular su fragilidad. En la mayoría de los casos las mezclas se preparan a partir de una solución homogénea la cual se puede separar en diferentes fases durante la polimerización del termoestable [1] . La mezcla de un polímero termoestable con un termoplástico ha sido estudiada usando diferentes polímeros en particular [2][3][4] . Los procesos involucrados y la morfología final de la mezcla dependen de la miscibilidad inicial de las mismas. En general la miscibilidad entre dos polímeros depende de la temperatura, pero cuando se utiliza un polímero termoestable y el mismo es polimerizado a través de un proceso de curado el incremento en su peso molecular puede ocasionar una separación de fases inducida por la polimerización. Una extensa bibliografía puede ser encontrada sobre la separación de fases inducida por la polimerización [5,6] . En los últimos años un importante número de trabajos han sido desarrollados en mezclas e...

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Cold crystallization and multiple melting behavior of poly(l-lactide) in homogeneous and in multiphasic epoxy blends

Cited by 30 publications

References 29 publications

Mechanical, thermal, and morphological properties of injection molded poly(lactic acid)/SEBS‐g‐MAH/organo‐montmorillonite nanocomposites

Mechanical, thermal, and morphological properties of injection molded poly(lactic acid)/SEBS‐g‐MAH/organo‐montmorillonite nanocomposites

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

Separación de fases y cristalinidad en mezclas epoxy/poli-3-hidroxibutirato

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