Electroactivity of PVDF electrospun fiber mats and ZNO-PVDF composites
Öğüt, Erdem (2007) Electroactivity of PVDF electrospun fiber mats and ZNO-PVDF composites. [Thesis]
Poly (vinylidene fluoride) (PVDF), an electroactive polymer, has great distinctions for its mechanical properties compared to highly brittle electroceramics. Its piezoelectricity however is not immediately utilizable after being cast in film form, and the cast PVDF film requires additional processes, such as mechanical stretching and poling. In this thesis, alternative to cast PVDF film, electroactive characteristics of PVDF fibrous mats produced by electrospinning are investigated to seek whether it is sufficient to use them as piezoelectric actuator directly after their production. The measurements revealed that under studied electrospinning parameter settings piezoelectricity of electrospun PVDF fibrous mat was not apparent, but the mat rather behaved as a linear dielectric. The transition from this linear to second order electric field dependence -that is interpreted as electrostrictive behaviour- is recorded. Moreover, ZnO/PVDF electroactive composites, to combine features of ceramic and polymer materials, are produced by two methods. While ZnO is utilized as primary piezoelectric component, which does not require poling, PVDF is chosen as the matrix material to enhance the flexibility of the composite material. In the first process, a ZnO fibrous mat via electrospinning of precursor fibers and their calcination is dipped into a PVDF solution. In the second, ZnO and PVDF powders are mixed and casted as composite. Electroactive characterization showed that both processes result in a composite material with piezoelectric properties.
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