How to manufacturing PVDF piezoelectric film in laboratory

How to Manufacturing PVDF piezoelectric film in laboratory

In view of the manufacturing process of PVDF piezoelectric film, Guangzhou POTOP Experimental Analysis Instrument Co., Ltd. has developed a special PVDF piezoelectric film extrusion casting and stretching test line (Small Laboratory Extrusion Casting & MDO Line), which can finish PVDF resin melting extrusion, film forming, film longitudinal stretching, traction, edge cutting, coiling and so on. It consists of a small precision single screw extruder and a small precision casting & longitudinal stretching（MDO) machine.

Material introduction:

PVDF piezoelectric film has large piezoelectric constant, wide frequency response, good mechanical strength, shock resistance, light weight, flexible, easy to match acoustic impedance, easy to process into a large area, not easy to be polluted by water and general chemicals. It can be used not only in many fields, but also in situations where piezoelectric ceramics cannot be used.

Extrusion molding of PVDF films:

1. Screw selection

For the extruding screw of PVDF, the isometric gradient screw and the mutant screw can be used. The L / D is more than 25 and the compression ratio is 1.6-3.

2. Mould selection

The best choice for extrusion Die of PVDF film (sheet) is clothes hanger structure.

3. Extrusion temperature of PVDF film (sheet)

Barrel temperature: 175-187 ℃ / 190-215 ℃ / 220-230 ℃

Mold temperature: 210-220 ℃

Casting cooling roll (calendering) temperature: 80-100 ℃

4. Quality requirements of PVDF films

Smooth, smooth surface, free of any longitudinal or transverse folds and nebuly ripples.

Allowable thickness tolerance of ±0.005mm for product.

No bubbles or impurities in the product.

The surface of the product is bright and hard, when the thickness is less than 0.1 mm, it is colorless transparent film, when the thickness is 0.11-0.2 mm, it is milky translucent film, and when the thickness is more than 0.21 mm, it is milky white.

No dust or water droplets on the surface of products.

No scratches, indentation, and any impact or knife marks on the surface of the product.

Manufacturing method for PVDF piezoelectric film in laboratory

(1) The forming of PVDF film: extruding with a small precision single screw extruder, forming the melt film by Die, and then forming the film through the small casting film machine, the thickness is 50-400um.

(2) PVDF film stretching: PVDF film is cooled by a small tape roller and immediately enters a small film longitudinal stretch function roller group(MDO machine). The stretching multiple is 4 times. The stretching temperature is 60-80℃, and the stretching speed rate is 5m/min.

(3) PVDF film annealing treatment: the PVDF film, which maintains the tensile state, is placed in a thermostat at 100-200℃, and then stored naturally after 24h.

(4) Evaporating electrode: according to the requirements, evaporating100nm thickness metal layeron the surface of PVDF film.

(5) Thermal polarization: the PVDF film is placed in the polarization field at 60-90℃, the applied voltage is 600-1000KV/cm, the heat preservation and pressure timeis 20-120min.


Characteristics of PVDF piezoelectric Film Extrusion Casting & MDO Line

1. High torque single screw extruder

   The extruder of PVDF piezoelectric Film extrusion casting & MDO line is driven by high torque servo motor, which can provide constant torque output in the range of full rotational speed and ensure the stability of extrusion pressure.

Because PVDF is fluorine material, so screw, barrel and die need to adopt anti-corrosion and wear-resistant material;


2. Small plastic casting film and MDO machine

All rollers are driven by servo motor with high running stability and synchronicity, which can make the film keep good thickness tolerance.

All the rollers are designed with special runner, which can ensure the temperature of the roller surface to be uniform.

The longitudinal stretching function can provide 5-10 times stretching ratio.

PVDF Piezoelectric Film Extrusion Casting & MDO Line is uesd by Small Laboratory Extrusion Casting & MDO Line, this line can also use for PP, PE, PET etc. It is suitable for the preparation of plastic film by extrusion, casting, stretching, drawing and winding such processing.

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