Multiple melting in blends of isotactic and atactic poly(β-hydroxybutyrate)

Pearce, R.; Marchessault, R. H.

doi:10.1016/0032-3861(94)90285-2

Cited by 102 publications

(71 citation statements)

References 34 publications

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“…The slight shift of the melting peak to lower temperatures with increased (R,S)-BL content, suggests that crystals with lower thermal stability had been formed [46]. The higher temperature peak should be attributed to crystals recrystallized during the DSC heating process [8,48].…”

Section: Differential Scanning Calorimetry (Dsc) and Wide Angle X-raymentioning

confidence: 97%

“…Additionally, the most striking feature in Figure 7B is that all the DSC melting traces of the copolyesters show bimodal melting peaks, whereas the DSC melting curve of PCL only reveals a single peak in the absence of (R,S)-BL. In general, these peaks are attributed to a crystalline reorganization via melting, re-crystallization and re-melting at higher temperature [8,[46][47][48].…”

Section: Differential Scanning Calorimetry (Dsc) and Wide Angle X-raymentioning

confidence: 99%

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Ring-opening copolymerization of (R,S)-β-butyrolactone and ε-caprolactone using sodium hydride as initiator

Monsalve¹,

Contreras²,

Laredo³

et al. 2010

Express Polym. Lett.

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Abstract. Copolymers of racemic β-butyrolactone ((R,S)-BL) and ε-caprolactone (CL), were synthesized by ring-opening polymerization initiated by sodium hydride (NaH). The initiator exhibited a satisfactory catalytic activity, producing copolymers whose yields are greatly influenced by the feed monomer ratio, CL/BL. All polymers obtained were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and wide angle X-rays scattering, WAXS. The molar composition of copolyesters determined by 1 H-NMR spectra, showed that the incorporation of CL is favoured over the incorporation of (R,S)-BL. Gel permeation chromatography and 13 C-NMR spectra indicated that CL/BL copolymers had block sequence distribution. The TGA analysis of copolymers showed that these copolymers are stable up to temperatures near 200°C, followed by a decomposition process in two steps; the first one is attributed to the (R,S)-BL block degradation and the second to the remaining PCL block. The crystallization process of these copolymers was studied by DSC and WAXS showing that the amorphous (R,S)-BL segments chains did not affect the crystallinity of the PCL blocks.

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Section: Differential Scanning Calorimetry (Dsc) and Wide Angle X-raymentioning

confidence: 97%

Section: Differential Scanning Calorimetry (Dsc) and Wide Angle X-raymentioning

confidence: 99%

Ring-opening copolymerization of (R,S)-β-butyrolactone and ε-caprolactone using sodium hydride as initiator

Monsalve¹,

Contreras²,

Laredo³

et al. 2010

Express Polym. Lett.

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“…Melting peaks appearing around 70 and 170°C originated from the individual constituents P(3HP) and P(3HB). The multiple melting features can be interpreted by several factors as distribution of lamellar thickness, modification of crystals, perfectness of crystallites and re-crystallization during the heating scan as reported by Pearce et al 28 Melting point of the crystalline constituent in a compatible binary blend is lowered due to the mutual interaction arisen from the presence of a secondary amorphous partner. However, this behavior of a binary blend comprised of two semi-crystalline components may become more complicated.…”

Section: Thermal and Crystallization Behavior Of P(3hb)/p(3hp)mentioning

confidence: 99%

Phase Structure and Biodegradation of the Bacterial Poly(3-hydroxybutyric acid)/Chemosynthetic Poly(3-hydroxypropionic acid) Blend

Cao

Asakawa

Yoshie

et al. 1998

Polym J

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ABSTRACT:Two different aliphatic polyesters, bacterially synthesized polyester poly(3-hydroxybutyric acid) [P(3HB)] and chemically synthesized poly(3-hydoxypropionc acid) [P(3HP)], were blended via solvent casting. By differential scanning calorimetry. polarized optical microscopy. wide-angle X-ray diffractometer and dynamic mechanical thermal analytical instrument, thermal and crystallization behavior and dynamic mechanical relaxation of the as-prepared binary blends were systematically studied. Immiscible properties were ambiguously demonstrated for these blends over the whole range of constituent composition. Glass transition temperature and proton spin diffusion times (Tr and nip) obtained by the high-resolution solid state 13C NMR measurements indicated that the blend system was immiscible not only on an observation scale of DSC (about 10 nm). but on a Tr scale (several tens of nm). Enzymatic biodegradation of the blend samples by extracellular P(3HB)-depolymerase from the bacterium strain A.faecalis TI showed an approximately linear relation between the degradation rate and the component composition. In addition, on the basis of biochemical oxygen demand (BOD). pure P(3HP) could not be biodegraded in the river water, while environmental biodegradability was confirmed when it presents as one constitutive component of the binary P(3HB) /P(3HP) blend.KEY WORDS P(3HB)/P(3HP) Blend / Thermal and Crystallization Behavior/ Morphology ofSpherulite/ Dynamic Mechanical Thermal Analysis/ Proton Spin Diffusion/ Miscible Property/ Enzymatical and Environmental Biodegradation Behavior / Poly(hydroxyalkanoic acid)s (PH As) which accumulate as the intracellular storage compounds by the widely distributed microorganisms in the environments, are now of increasing importance due to more serious problem in plastical waste disposaL 1-4 Because of their bacterial origins, this class of aliphatic polyesters can be environmentally degraded into water and carbon dioxide, exhibiting unique features distinguishable from those of the conventional plastics. A wide range of bacterial biodegradable polyesters and copolyesters have been developed for various technical applications by constructing the desired repeating unit structures. 5 Poly(3-hydroxybutyric acid) [P(3HB)], a representative of PHAs, is a thermoplastics known to be suffered from its high melting point, excessive brittleness and poor impact resistance in applications. 2 -4 Although efforts have been made to bacterially co-polymerize 3HB repeating units with other monomers such as 3-hydroxypropionic acid (3HP),6-8 3-hydroxyvaleric acid (3HV),9 4-hydroxybutyric acid (4HB),2,10-12 and so forth, can improve its deficiencies. However, the considerably high cost of the cultivable substrates and/or precursor-substrates in fermentation impede broader applications of the bacterial polyesters. As an alternative route to provide materials with desirable properties, blending the natural P(3HB) with a secondary constituent is effective without loss of favorable features of biodegradabi...

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“…El termograma obtenido para el PHB puro presenta un pico endotérmico principal ubicado en 170 °C solapado con un pico de menor altura ubicado en 159 °C. El PHB tiene un proceso de cristalización complejo, y los dos picos observados en la fusión del PHB pueden ser atribuidos a fusión, recristalización y refusión [10] . Se puede concluir que existe una disminución del punto de fusión para las mezclas con respecto al PHB puro.…”

Section: Mediciones Mediante Calorimetría Diferencial De Barridounclassified

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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Multiple melting in blends of isotactic and atactic poly(β-hydroxybutyrate)

Cited by 102 publications

References 34 publications

Ring-opening copolymerization of (R,S)-β-butyrolactone and ε-caprolactone using sodium hydride as initiator

Ring-opening copolymerization of (R,S)-β-butyrolactone and ε-caprolactone using sodium hydride as initiator

Phase Structure and Biodegradation of the Bacterial Poly(3-hydroxybutyric acid)/Chemosynthetic Poly(3-hydroxypropionic acid) Blend

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

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