New insights into the beta-form crystal toughening mechanism in pre-oriented PHBV films

Yang, Jian; Zhu, Haijin; Zhao, Ying; Jiang, Qianhong; Chen, Haiming; Liu, Guoming; Chen, Peng; Wang, Dujin

doi:10.1016/j.eurpolymj.2017.03.017

Cited by 11 publications

(15 citation statements)

References 59 publications

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“…The PCL processing aid in fiber (I) seems to have no particular effect on the P3HB structure since the same trends are observed for both fibers. A similar coupled increase-decrease behavior for the equatorial peaks has been previously observed for P3HB and poly(3-hydroxybutyrate-co-3hydroxyvalerate) (PHBV) films, respectively [34,47].…”

Section: Msupporting

confidence: 79%

“…The diameter of the lamellar sizes D 2 is slightly decreasing under applied tension with reversible changes (Figure 12c). The larger size D 1 is, however, steadily decreasing during the cycling of Previous publications have shown two-point SAXS patterns of PHBV films with single longspacings in the range of 7-11 nm [47] or in P3HB films with long-spacings in the range of 8 nm (low tension) to 16 nm (high tension) [34]. This matches well with the second long-spacing (7.7-9.6 nm) that we observe in our fibers and we therefore attribute the second peak to arise from P3HB α-crystals.…”

Section: Mmentioning

confidence: 91%

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Tensile study of melt-spun poly(3-hydroxybutyrate) P3HB fibers: Reversible transformation of a highly oriented phase

Perret

Reifler

Gooneie

et al. 2019

Polymer

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Poly-3-hydroxybutyrate (P3HB) typically crystallizes into the orthorhombic α-form. The additional intense and rather broad equatorial reflection in wide-angle X-ray diffraction (WAXD) patterns seen in our melt-spun P3HB fibers cannot be attributed to the α-form crystals.We propose that a non-crystalline mesophase, which consists of disordered but highly oriented and stretched molecules located between α-crystals, leads to the observed broad equatorial reflection. We show that the transformation of this mesophase from and into the α-form phase is partially reversible under cyclic tensile loading. Structure factor calculations, which are based on atomic positions from molecular dynamics simulations of a set of stretched P3HB molecules, support this model. The WAXD patterns were analyzed with azimuthal, radial, equatorial and meridional scans and the changes in the crystal orientation, changes in the percentages of individual phases and changes in the α-crystal lattice spacings were analyzed as a function of the applied tension. Changes in long spacings, crystal sizes and coherence lengths under cyclic loading were determined with small-angle X-ray scattering (SAXS) measurements. The long spacing between α-crystals increases when tensile stress is applied and it snaps back to the original spacing when the tensile stress is released. Highlights• Reversibility behavior of structural transformations in P3HB under cyclic loading.• Detailed SAXS, WAXD analysis of P3HB fibers under cyclic loading.

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Section: Msupporting

confidence: 79%

Section: Mmentioning

confidence: 91%

Tensile study of melt-spun poly(3-hydroxybutyrate) P3HB fibers: Reversible transformation of a highly oriented phase

Perret

Reifler

Gooneie

et al. 2019

Polymer

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“…The β-form of PHB (and also PLLA) is said to possess higher mechanical property than the α-form because of the more highly extended chain conformation. 4,21,24,76 The present structural study may encourage us to study such a mechanical property of PHB from the atomic level, once we know the concrete crystal structure of the PHB β-form.…”

Section: Discussionmentioning

confidence: 80%

“…As well known, an increment of the molecular weight may improve the brittleness of the sample, as already reported in refs. [17][18][19][20][21][22][23][24][25][26][27]30 However, even when the PHB sample of an ultrahigh molecular weight of 10 6 g/ mol order is stretched, the transition from the αto βform is still not perfect. 17 The LP values increase in an aff ine mode with an increase of strain up to 240 Å (α-form) and 400 Å (β-form).…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, the details of the crystal structure of the β-form have not yet been determined. The β-form is obtained by applying a tensile force to the oriented α-form. − However, the transition does not occur completely, and the α- and β-forms coexist even in the sample tensioned strongly just before the occurrence of the breakage. − The reason for such an incomplete transition behavior must be understood from the structural point of view, including the higher-order structural change.…”

Section: Introductionmentioning

confidence: 99%

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X-ray Crystal Structure Analysis of Poly(3-hydroxybutyrate) β-Form and the Proposition of a Mechanism of the Stress-Induced α-to-β Phase Transition

Phongtamrug

Tashiro

2019

Macromolecules

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The crystal structure of poly(3-hydroxybutyrare) β crystal form has been analyzed on the basis of two-dimensional X-ray diffraction data. The all-trans zigzag chains are packed in the hexagonal unit cell of a = b = 9.22 Å, c (chain axis) = 4.66 Å, and γ = 120° with the space group P3221. The upward and downward chains are statistically located at one lattice site at 50% probability. By combining the thus-analyzed structure information of the β-form with the previously reported structure information of the α-form, the geometrical relation between these two crystalline phases has been clarified in detail. The tension-induced α-to-β phase transition affects the higher-order structural change, as known from the small-angle X-ray scattering (SAXS) data collected in the tensile deformation process. By analyzing all experimentally obtained wide-angle X-ray diffraction and SAXS data, the following transition model has been proposed: the high tension to the oriented sample causes the increase of the long period of the α-form lamellae. As the tensile force is increased, the local stress concentration starts to occur at the short tie chain segmental parts in the amorphous region sandwiched between the stacked lamellae. These highly tensioned tie chains induce the α-to-β structural change in both amorphous and directly connected crystalline regions and generate the 40 Å-wide bundles of zigzag chain segments passing through several neighboring lamellae along the draw direction. These bundles are repeated with the averaged period of about 90 Å in the lateral direction perpendicular to the draw axis. Further stretching causes the cut of the highly tensioned extended chain parts, resulting in the formation of voids and finally the breakage of the whole sample before the completion of the phase transition from the α- to β-form.

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Evaluation of spherulite growth in PHB‐based systems – A DoE approach

Majerczak

Liggat

2023

J of Applied Polymer Sci

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Formulations based on poly(hydroxybutyrate) (PHB) and poly(hydroxybutyrate‐co‐valerate) were studied to statistically assess the importance of process parameters (temperature) and chemistry in filled and/or plasticized PHB‐based formulations on spherulite growth rate (SGR) and nucleation density (ND). It was found that in binary systems, addition of a plasticizer results in shift of the maximum SGR towards lower temperatures, with the value of the shift dependent on polymer‐plasticizer compatibility. The presence of the filler does not significantly influence SGR, instead resulting in ND changes dependent on filler chemistry, with Cloisite Ca++ showing the strongest nucleating action in all formulations among fillers studied. In ternary systems, statistical analysis shows that SGR strongly depends on the crystallization temperature (Tc), plasticizer type and concentration, and hydroxyvalerate content in the polymer chain while being independent of the presence and chemistry of the filler in the system. ND has, however, proven to be dependent on all investigated parameters, including both filler type and its concentration, with Tc being the most important factor. These results expand the understanding of factors controlling crystallization in polymer systems and provide an initial set of design tools that can be used to control mechanical properties in new generations of packaging materials.

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New insights into the beta-form crystal toughening mechanism in pre-oriented PHBV films

Cited by 11 publications

References 59 publications

Tensile study of melt-spun poly(3-hydroxybutyrate) P3HB fibers: Reversible transformation of a highly oriented phase

Tensile study of melt-spun poly(3-hydroxybutyrate) P3HB fibers: Reversible transformation of a highly oriented phase

X-ray Crystal Structure Analysis of Poly(3-hydroxybutyrate) β-Form and the Proposition of a Mechanism of the Stress-Induced α-to-β Phase Transition

Evaluation of spherulite growth in PHB‐based systems – A DoE approach

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