Crystallization and morphology of poly(vinylidene fluoride)/poly(3-hydroxybutyrate) blends. II. Morphology and crystallization kinetics by time resolved X-ray scattering

• Published in: Journal of polymer science. Part B, Polymer physics Polymer physics, 2004-03, Vol.42 (6), p.974-985
• Main Authors: Liu, Jieping, Jungnickel, Bernd-J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Crystallization; crystallization kinetics; Exact sciences and technology; morphology; Organic polymers; Physicochemistry of polymers; poly(3-hydroxybutyrate); poly(vinylidene fluoride); Properties and characterization; time-resolved X-ray scattering
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.10683

The development of the morphology in poly(vinylidene fluoride)/poly(3‐hydroxybutyrate) (PVDF/PHB) blends upon isothermal and anisothermal crystallization is investigated by time‐resolved small‐ and wide‐angle X‐ray scattering. The components are completely miscible in the melt but crystallize separately; they crystallize stepwise at different temperatures or sequentially with isothermal or anisothermal conditions, respectively. The PVDF crystallizes undisturbed whereas PHB crystallizes in a confined space that is determined by the existing supermolecular structure of the PVDF. The investigations reveal that composition inhomogeneities may initially develop in the remaining melt or in the amorphous phases of the PVDF upon crystallization of that component. The subsequent crystallization of the PHB depends on these heterogeneities and the supermolecular structure of PVDF (dendritically or globularly spherulitic). PHB may form separate spherulites that start to grow from the melt, or it may develop “interlocking spherulites” that start to grow from inside a PVDF spherulite. Occasionally, a large number of PVDF spherulites may be incorporated into PHB interlocking spherulites. The separate PHB spherulites may intrude into the PVDF spherulites upon further growth, which results in “interpenetrating spherulites.” Interlocking and interpenetrating are realized by the growth of separate lamellar stacks (“fibrils”) of the blend components. There is no interlamellar growth. The growth direction of the PHB fibrils follows that of the existing PVDF fibrils. Depending on the distribution of the PHB molecules on the interlamellar and interfibrillar PVDF regions, the lamellar arrangement of the PVDF may contract or expand upon PHB crystallization and the adjacent fibrils of the two components are linked or clearly separated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 974–985, 2004