Suchergebnisse

[EN] Poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) copolymer containing ionizable moieties is here investigated as a melt processing additive for PVDF to develop high-quality ferro/piezoelectric polymer films by extrusion-calendering. The PVDF/PMMA-co-MAA miscibility and the β-phase crystallization from the melt state at high cooling rates were first explored by Flash DSC. Transposition to the melt-processing of thin films by extrusion-calendering is attempted and a direct production of β-crystals in high amounts is attested at a specific content of 5 wt-% PMMA-co-MAA. Ferro/piezoelectric properties were subsequently investigated and classical ferroelectric-type hysteresis loops clearly appear at room temperature for AC electric fields higher than 900 – 1200 kV/cm. Enhanced remanent polarizations (P) are observed with only 5 wt-% PMMA-based additives and the best ferroelectric performances are identified for PVDF/PMMA-co-MAA blends, in agreement with a higher β-phase content. Stable piezoelectric properties are also highlighted with maximal piezoelectric coefficient (d) of 11 pC/N for these formulations. A linear relationship is found between d and P in accordance with several models and, in this respect, the origin/optimization of the remanent polarization was investigated. Crystal transformations are revealed during high-voltage AC poling and high-quality ferroelectric behaviors with high P values up to 7 µC/cm are obtained at elevated poling temperatures for PVDF/PMMA-co-MAA blends (theoretical d up to 16 pC/N) approaching the theoretical limit value for perfectly-poled β-crystals. This study clearly opens up interesting perspectives in the development of cost-effective electroactive polymer films using industrially-relevant processes and demonstrates that PVDF-based blends with miscible functional PMMA copolymers represent an interesting approach for this purpose. ; Authors gratefully acknowledge the Wallonia Region/Service Public de Wallonie (Belgium), West Vlaanderen Region (Belgium), Agentschap Innoveren Ondernemen (Belgium) and European Commission (FEDER) for the financial support in the framework of the INTERREG V FWVL program (BIOHARV project, GoToS3 portofolio). Authors particularly thank Samuel Devisme from Arkema (France) for supplying raw materials. UMons (LPCM) gratefully acknowledges the Belgian Federal Government Office of Science Policy/Belgian Federal Science Policy Office (SSTC – PAI 6/27, Belgium) for general support and is much indebted to both the Wallonia Region/Service Public de Wallonie (Belgium) and the European Commission (FEDER) for financial support in the frame of phasing-out Hainaut. IMT Lille Douai and Université de Lille acknowledge both the International Campus on Safety and Intermodality in Transportation (CISIT, France), the Hauts-de-France Region (France) and the European Commission (FEDER) for their contributions to funding extrusion equipments, SAXS-WAXS laboratory equipments and calorimetric characterization tools. Authors also thanks the Spanish Ministerio de Economía y Competitividad (MINECO) for financial supports of MAT2017-88788-R and MAT2016-76851-R projects.