The Physical Ageing of Amorphous Poly(hydroxybutyrate)

Biddlestone, F.; Harris, Andrew T.; Hay, J. N.; Hammond, T.

doi:10.1002/(sici)1097-0126(199603)39:3<221::aid-pi511>3.0.co;2-o

Cited by 101 publications

(52 citation statements)

References 2 publications

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“…The thermal transition observed in the first heating curve at 60 °C (Fig. (A)) – hereafter T g2 – has previously been reported for samples stored at room temperature, and has been attributed to the glass transition temperature of the rigid amorphous fraction (RAF) . The RAF is formed even after very short periods (< 24 h) of storage at temperatures above the glass transition temperature of the mobile amorphous fraction .…”

Section: Resultsmentioning

confidence: 52%

“…During this process, the amorphous regions in contact with the crystals undergo a restriction of mobility. Moreover, small imperfect inter‐lamellar crystallites are formed (secondary crystallization) which further constrain the mobility of the amorphous regions . Above the T g of the RAF, melt and recrystallization start occurring, which translates into a negative slope in the DSC curve until the melting of the primary lamellae occur at the T m …”

Section: Resultsmentioning

confidence: 99%

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Polyhydroxyalkanoate (PHA) purification through dilute aqueous ammonia digestion at elevated temperatures

Burniol-Figols

Skiadas

Daugaard

et al. 2020

J of Chemical Tech & Biotech

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BACKGROUND Purification of polyhydroxyalkanoates (PHA) is a challenging step, given the difficulty of achieving high PHA purity, while maintaining polymer integrity, in a sustainable and cost‐efficient manner. This study evaluated the potential of dilute ammonia digestion as a method to purify PHA from mixed microbial consortia. RESULTS Digestion temperatures were critical to the obtainable purity and the amount of recovered PHA. At temperatures below 75 °C (regardless of the incubation time and ammonia concentration), a low PHA recovery (down to 65%) and no increase in purity was observed. By increasing the temperature above 75 °C, a significantly higher PHA purity and higher recovery (above 90%) could be achieved. Temperatures maximizing the purity (140 °C) led to a detrimental reduction in the molar mass of the isolated PHA, but the use of a sonication pre‐treatment enabled to increase the purity at temperatures leading to limited molar mass loss (75–115 °C). The impurities still present in the recovered PHA did not compromise its thermal stability, and no significant degradation occurred during melting of PHA with 86% purity (comparably to pure chloroform‐extracted PHA). Conversely, PHA recovered through sulphuric acid (H2SO4) digestion underwent severe degradation during melting, despite presenting higher purity (98%). CONCLUSIONS High PHA purity, recovery and thermal stability can be obtained with dilute ammonia digestion. These observations, combined with the possibility of reusing ammonia within the process, make this method a promising approach for a more sustainable purification of PHA. © 2020 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Polyhydroxyalkanoate (PHA) purification through dilute aqueous ammonia digestion at elevated temperatures

Burniol-Figols

Skiadas

Daugaard

et al. 2020

J of Chemical Tech & Biotech

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“…Galego et al, by means of X-ray diffraction technique, found the crystallinity of pure P(3HB) to be 69.0 ± 0.2% 36 . However, different values may be found, since PHB is very sensitive to secondary crystallization and physical aging, which may increase crystallinity 35,37,38 . According to what is presented on Table 2, the crystallinity decreased with addition of ND, regardless of ND content; it can be justified by presence of aggregation of ND on all formulation, obstructing their polymeric chains mobility, which limits P(3HB) crystallization.…”

Section: Resultsmentioning

confidence: 99%

Influence of Encapsulated Nanodiamond Dispersion on P(3HB) Biocomposites Properties

et al. 2017

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Studies regarding biodegradable nanocomposites to be used as orthopedics devices have been intensified. This work aims to investigate the influence of ND dispersion on thermal and mechanical properties of a biocomposite of poly(3-hydroxybutyrate) (P(3HB)) reinforced with nanodiamonds (ND) intended to be used as orthopedics devices, with advantages as biodegradability. In order to improve its dispersion, P(3HB) has encapsulated ND in three different mass ratios: P(3HB):ND(16:1), (12:1) and (8:1). However, for all formulations, NDs are presented as agglomerates, in different intensities. In order to relate the distribution of ND within the polymer matrix and biocomposite properties, TGA, DSC, and DMA analysis were done. The formulation with higher content of ND, P(3HB):ND(8:1), presents larger aggregates; thus, decreasing its properties. With smaller and more distributed agglomerates, the 12:1 ratio composite displayed superior storage modulus and glass transition temperature, probably due to better polymer chain restriction.

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“…Por un lado, la baja densidad de nucleación, conjuntamente con el alto grado de cristalinidad y la lenta velocidad de cristalización conducen a la formación de grandes esferulitas [77,78]. En el interior de estas grandes esferulitas se pueden formar fisuras circulares y radiales debido a la diferencia entre el coeficiente de expansión térmica radial y circunferencial [79].…”

Section: Propiedades Mecánicasunclassified

“…Este fenómeno no está claramente elucidado, pero se supone que las cadenas amorfas interlamelares son progresivamente restringidas de movimiento, lo que resulta en un aumento de la fracción amorfa rígida [83,84]. Se proponen dos explicaciones para esclarecer este fenómeno: la cristalización secundaria de la fase amorfa [77,78] y el envejecimiento físico de la fase amorfa [85][86][87].…”

Section: Propiedades Mecánicasunclassified

Desarrollo y caracterización de formulaciones poliméricas biodegradables y termoconformables para envasado

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The Physical Ageing of Amorphous Poly(hydroxybutyrate)

Cited by 101 publications

References 2 publications

Polyhydroxyalkanoate (PHA) purification through dilute aqueous ammonia digestion at elevated temperatures

Polyhydroxyalkanoate (PHA) purification through dilute aqueous ammonia digestion at elevated temperatures

Influence of Encapsulated Nanodiamond Dispersion on P(3HB) Biocomposites Properties

Desarrollo y caracterización de formulaciones poliméricas biodegradables y termoconformables para envasado

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