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Processing of PVDF-based Electroactive/Ferroelectric Films: Importance of PMMA and Cooling Rate From the Melt State on the Crystallization of PVDF Beta-Crystals

Abstract

Poly(vinylidene difluoride) (PVDF) displays attractive ferroelectric/piezoelectric properties and its polar β-crystals are specifically targeted for achieving electroactive applications. However, their direct crystallization from the melt state represents a challenging task that has never been addressed using melt-state processes. The use of poly(methyl methacrylate) (PMMA) is herein investigated to promote the PVDF polar β-phase using melt-blending and extrusion-calendering technologies. The presence of the β-phase is here confirmed by ATR-FTIR and WAXS experiments with blends at PMMA content as low as 5wt-%. The key role of PMMA for the β-phase crystallization from the melt state was unambiguously highlighted with the help of Flash DSC experiments on non-isothermal cooling mode from the melt state. PMMA is able to efficiently shift the α-to-β crystal transition to lower cooling rates (> 100 – 200°C/s), making the achievement of PVDF polar β-phase for these blends compatible with conventional processing tools. A crystal phase diagram is proposed for PVDF/PMMA blends to highlight dual effects of both PMMA and cooling rate on the PVDF crystallization during melt-processing. Ferroelectric properties were even observed for blends containing PMMA up to 10wt-% with the highest remanent polarization obtained at 5wt-% PMMA. After 10wt-% PMMA, a progressive transition from ferroelectric to pseudo-linear dielectric behavior is observed more likely due to the presence of PMMA in the interlamellar amorphous phase of polar PVDF spherulites as shown by SAXS experiments. In this work, we successfully demonstrated that PMMA plays a key role on the crystallization of PVDF polar crystals from the melt state, enabling a large-scale and continuous extrusion processing of PVDF-based materials with attractive dielectric properties for sensing and harvesting applications.

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Publication details

The article was received on 06 Feb 2018, accepted on 13 Apr 2018 and first published on 16 Apr 2018


Article type: Paper
DOI: 10.1039/C8SM00268A
Citation: Soft Matter, 2018, Accepted Manuscript
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    Processing of PVDF-based Electroactive/Ferroelectric Films: Importance of PMMA and Cooling Rate From the Melt State on the Crystallization of PVDF Beta-Crystals

    A. De Neef, C. Samuel, G. Stoclet, M. Rguiti, C. Courtois, P. Dubois, J. Soulestin and J. Raquez, Soft Matter, 2018, Accepted Manuscript , DOI: 10.1039/C8SM00268A

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