Double-step moulding: An effective method to induce the formation of β-phase in PVDF. (10th April 2020)

• Record Type: Journal Article
• Authors: Brunengo, E.; Luciano, G.; Canu, G.; Canetti, M.; Conzatti, L.; Castellano, M.; Stagnaro, P.
• Is Part Of: Polymer. Volume 193(2020)
• Publication Date: 2020-04-10
• Subjects: PVDF polymorphism -- Polymer processing -- Infrared spectroscopy -- Dielectric properties; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2020.122345
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: 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. Graphical abstract: Image 1 Highlights: 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.