Preparation method of high-crystallinity polyvinylidene fluoride (PVDF)

Abstract

The invention discloses a preparation method of high-crystallinity polyvinylidene fluoride (PVDF), which comprises the following steps: adding a microsphere expanding agent of which the thermal expansion coefficient is far higher than that of PVDF in the preparation of the PVDF material, wherein when the temperature rises from room temperature to the melting temperature of the PVDF, the microsphere sharply expands, and the volume of the microsphere is increased by about 10-20 times in comparison with the situation at room temperature; and then, cooling the PVDF from the melting temperature to room temperature to ensure that the PVDF is gradually solidified and crystallized, wherein in the cooling process, the microsphere sharply shrinks, so that uniform tensile stress can be formed in the PVDF in the solidification process, and the tensile stress can improve the crystallinity of a beta phase in the PVDF. For the PVDF prepared by the method, the crystallinity of the beta phase is obviously improved; and the pyroelectric property of the material is superior to that of the PVDF material prepared by a common method. The PVDF organic ferroelectric material prepared by the invention has high beta-phase crystallinity and spontaneous polarization rate and favorable pyroelectric property, and conforms to the use requirements of ferroelectric organic materials.

Description

technical field [0001] The invention belongs to the preparation technology of high-performance organic functional materials, in particular, it relates to a preparation method of polyvinylidene fluoride with high crystallinity. Background technique [0002] Among various materials, ferroelectric materials are widely used in the preparation of large-capacity capacitors, electrical energy storage devices, energy harvesters, pressure sensors and uncooled infrared detectors due to their good dielectric, piezoelectric and pyroelectric properties. . [0003] Ferroelectric materials can be divided into two categories: inorganic ferroelectric materials and organic ferroelectric materials. Inorganic ferroelectric materials (such as barium titanate, lead zirconate titanate and other ceramics and single crystals) have good ferroelectric properties and have been widely used. However, the disadvantages of inorganic ferroelectric materials are that the preparation cost is high, the prepa...

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Problems solved by technology

Using the pulling method to apply tensile stress to PVDF during its solidification process can effectively improve the crystallinity of the β phase, but this method requires high preparation equipment and complicated processes, and is not suitable for mass production; adding trifluoroethylene to PVDF (TrFE), forming a polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) ferroelectric copolymer, can also increase the crystallinity of the β phase of the material, but the (P(VDF-TrFE)) copolymer is expensive ; Adding chlorides, such as bismuth chloride, etc. to PVDF is also a conventional method to increase the β-phase content of the material. This method is simple and easy to operate, but the effect of improving the crystallinity of the β-phase is not ideal

[0006] Although PVDF has the incomparable softness, transparency, low manufacturing cost, simple process and easy processing of inorganic ferroelectric materials, and its ferroelectricity is superior to other organic materials, but its ferroelectricity still needs to be widely used to make PVDF widely used. to be further improved

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