ABSTRACT
The ferroelectric and piezoelectric properties of poly(vioylidene fluoride) (PVDF), in particular, can be improved by chemical modification through copolymerization with trlfluoroethylene or tetrafluoroethylene [1]. The addition of ceramic ferroelectrics such as lead zirconium titanate in order to create composites with improved electric performance is common [2,3]. Sandwich arrays with poly(tetra fluoroethylene) or poly(ethylene terephthalate) [4] have been shown to affect strongly the magnitude and temporal stability of ferroelectric polarization. Laminates with other polymers can exhibit interesting new properties [5,6]. These issues will be treated in detail in other parts of this handbook. In this particular chapter, the ferroelectric properties of PVDF to which other polymers ("polyblending") or organic low-molecular-weight substances ("plastification") have
Materials which consist of more than one component are called blends or alloys. Their properties depend to a large extent on the miscibility of the components, i.e., on the ability to mix stably on a molecular level. We speak of "mixtures," and of miscibility in a narrow sense, if the intimately mixed state is favored by thermodynamic forces, and is therefore thermodynamically stable. In contrast, we speak of "compatibility" if the intimate mixing can be enforced, or is only enforced, by suitable processing conditions. Although the resulting structure is then not stable from a thermodynamic point of view, such a structure can nevertheless be sufficiently stable over the lifetime of the material because of the lack of structural relaxation possibilities. The properties of such a material are then almost the same as those of a truly miscible blend.
