Double-step moulding: An effective method to induce the formation of β-phase in PVDF

Nowadays, the investigation of smart methods promoting PVDF β phase has become an important research topic in many energy related fields. In this work, compression moulding was proposed as an effective, simple and easy-scalable technique to tune PVDF polymorphism and obtain the desired crystalline f...

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Bibliographic Details
Published in:Polymer (Guilford) 2020-04, Vol.193, p.1-9, Article 122345
Main Authors: Brunengo, E., Luciano, G., Canu, G., Canetti, M., Conzatti, L., Castellano, M., Stagnaro, P.
Format: Article
Language:English
Subjects:
Beta phase
Compression
Dielectric loss
Dielectric properties
Dielectric relaxation
Infrared analysis
Infrared spectra
Infrared spectroscopy
Mechanical measurement
Polymer processing
Polymers
Polymorphism
Pressure molding
Principal components analysis
PVDF polymorphism
Shear stress
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Summary:Nowadays, the investigation of smart methods promoting PVDF β phase has become an important research topic in many energy related fields. In this work, compression moulding was proposed as an effective, simple and easy-scalable technique to tune PVDF polymorphism and obtain the desired crystalline form, exploiting a procedure in two steps. After a preliminary principal component analysis of the infrared spectra, the different moulding conditions tested were correlated with the electroactive phase amount, obtaining a non-monotonous trend. Finally, dielectric and dynamic-mechanical measurements were carried out on selected samples. Experimental evidence indicates that the double-step moulding induces the β phase formation due to the orienting effect generated by the shear stresses in the not completely molten polymer. Moreover, this method determines an increase in permittivity, a reduction of the dielectric losses and a change of PVDF molecular relaxations with respect to the reference film moulded through a simple single-step moulding. [Display omitted] •A double-step (DS) moulding is proposed to promote β phase formation in PVDF.•PCA validates the quantitative evaluation of β phase achieved by ATR-FTIR.•The obtained β phase amount is correlated with moulding conditions through MLR.•The DS moulding allows to tune the PVDF polymorphism.•The DS moulding affects also molecular relaxations and enhances dielectric response.
ISSN:0032-3861
1873-2291
DOI:10.1016/j.polymer.2020.122345