Mechanical processing and fabrication

Both PVDF and its copolymer with TrFE are thermoplastic, and as such can be easily processed in conventional thermoforming equipment. PVDF has an almost unique combination of processability, mechanical strength and chemical resistance. Because of this, it has found a niche in the speciality polymers market unconnected with its unusual electrical properties, and a substantial body of processing information is available both from manufacturers literature and from other publications [15-17]. 

The copolymer is a similar material to PVDF, and while as yet no large commercial usage has emerged, the same processing methods can be used. 

The ease with which a plastic material such as PVDF can be formed into large areas or complex shapes is one of the significant advantages that polymer ferroelectric materials have over the conventional ceramic types. 

Historically, nearly all the early investigations into the ferroelectric properties of PVDF were carried out on thin ( 25 jam) films. This was necessary for very good reasons. Most importantly, the material must be oriented to develop an incipient ferroelectric structure. This is most conveniently done by using conventional thin film making equipment, which stretches a preformed polymer strip in either one or two in-plane directions. In addition to this requirement, very high fields (typically 100 kV mm ) must be applied to the oriented polymer during the poling 

The most straightforward method of producing a thin film by mechanical means is to stretch the preform in one direction only. In the laboratory this can be done by applying a load to one edge of a preformed sheet held at elevated temperature. The load and the temperature are adjusted to produce a suitable elongation, typically about four times the original length. 

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