Electrospinning/electrospray of polyvinylidene fluoride (PVDF): piezoelectric nanofibersby F. Mokhtari, M. Latifi, M. Shamshirsaz

The Journal of The Textile Institute

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Electrospinning/electrospray of polyvinylidene fluoride (PVDF): piezoelectric nanofibers

F. Mokhtaria, M. Latifia & M. Shamshirsazb a Textile Engineering Department, Textile Excellence & Research Centers, Amirkabir

University of Technology, Tehran, Iran b New Technologies Research Centre, Amirkabir University of Technology, Tehran, Iran

Published online: 01 Sep 2015.

To cite this article: F. Mokhtari, M. Latifi & M. Shamshirsaz (2015): Electrospinning/electrospray of polyvinylidene fluoride (PVDF): piezoelectric nanofibers, The Journal of The Textile Institute, DOI: 10.1080/00405000.2015.1083300

To link to this article: http://dx.doi.org/10.1080/00405000.2015.1083300

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Electrospinning/electrospray of polyvinylidene fluoride (PVDF): piezoelectric nanofibers

F. Mokhtaria, M. Latifia* and M. Shamshirsazb aTextile Engineering Department, Textile Excellence & Research Centers, Amirkabir University of Technology, Tehran, Iran; bNew

Technologies Research Centre, Amirkabir University of Technology, Tehran, Iran (Received 9 March 2015; accepted 2 August 2015)

Polyvinylidene fluoride (PVDF) is one of the most studied polymer systems that exhibits piezoelectric, pyroelectric, and ferroelectric properties. It is well known that PVDF is able to crystallize in four different forms that involve three different chain conformations, namely α, β, γ, and δ phases. Among the four polymorphs, the β-phase has the largest spontaneous polarization per unit cell and thus exhibits the highest electro active properties. In the past few decades, many researches have been done to increase the β-phase content in PVDF using various processing techniques and additives. One of these processing methods is electrospinning/electrospray with organic/inorganic additives, nanoparticles or carbon nanotubes. Material and structural analyses on fabricated nanofibers using instruments such as X-ray diffraction, Fourier transform infrared, Differential Scanning Calorimetry, and Scanning Electron Microscope as the characterizations of piezoelectric nanofibers are carried out. This article attempts to have an overview on the electrospinning process of PVDF as a piezoelectric polymer, method of characterization of its β-phase and its application as a nanogenerator.

Keywords: polyvinylidene fluoride (PVDF); piezoelectric; electrospinning; electrospray; nanofiber

Introduction

Piezoelectric materials have been widely used for various applications such as biomedical engineering, damage detection, automotive engines, and electronics. Also, piezoelectric materials exclusively use sensors, actuators, or energy harvesters (Dodds, Meyers, & Loh, 2012). As a piezoelectric polymer, Poly (vinylidene fluoride) (PVDF) is attractive in energy conversion applications between electrical and mechanical forms because of its low cost, high flexibility, and biocompatibility. The piezoelectric property of PVDF has been developed in various device applications, such as strain sensors (Chen,

Kwon, & Tan, 2008; Choi & Jiang, 2006; Toda & Dahl, 2007; Yang, Hsu, Ho, & Feng, 2007), mechanical actuators (Lee, Joo, Han, & Koh, 2005; Snis, Edqvist,

Simu, & Johansson, 2008; Wiederkehr, Salvadori,

Brugger, Degasperi, & Cattani, 2008), energy harvesters (Granstrom, Feenstra, Sodano, & Farinholt, 2007;

Shenck & Paradiso, 2001; Wang & Ko, 2010; Wu,

Chen, & Liu, 2009), artificial muscles (Shahinpoor, 2004), and force sensor (Wang, Zhang, Ren, Zhang, &

Xu, 2011). Recent advancements in nanotechnology have further explored the possibility of using PVDF nanofibers for possible applications in nano sensors, actuators, and energy generators. The mentioned applications rely on the good piezoelectric property of

PVDF. Proper mechanical stretching and electrical poling are necessary to achieve good piezoelectricity.

The ability of piezoelectric materials to convert electrical to mechanical energy and conversely mechanical to electrical energy has been exploited in an application closely related to power generation. Many works have already gone into the design and characterization of piezoelectric transformers (Richards,

Anderson, Bahr, & Richards, 2004). PVDF is a semicrystalline thermoplastic polymer in which processing conditions affect its physical properties and can be strongly influenced by the presence of nanoparticles, which affect the crystallization behavior (Mago, Kalyon, & Fisher, 2008). There are at least four crystalline phases in PVDF named the α, β, γ, and δ phase. Among them, the β-phase has all the dipolar moments pointing to the same direction and has the best piezoelectric responses. The α-phase is the common form and most stable one in the commercial PVDF that is formed by the simple crystallization process upon cooling from the melt in quiescent conditions (Zheng et al., 2011).