Method for preparing high-oriented gamma phase polyvinylidene fluoride PVDF thin film

Abstract

The invention relates to a method for preparing a high-oriented gamma phase polyvinylidene fluoride PVDF thin film. The method comprises the following steps of: 1) first, casting a thin film for PVDF liquor to heat, insulate and eliminate thermal history, and quickly cooling the PVDF thin film at 50 DEG C/min to 160-170 DEG C; and 2) applying pressure to melt by a polymethylsiloxane plate to apply a shear stress, standing at 160-170 DEG C, wherein the crystallizing form at 160-163 DEG C is converted to alpha crystallizing form, and conversion from alpha crystallizing form to gamma crystallizing form occurs at 168-170 DEG C; the crystallizing crystal nucleus is alpha crystal nucleus at 164-167 DEG C, and the crystallizing form at 168-170 DEG C is gamma crystallizing form. A polarizing microscope, a scanning electron microscope and an infrared spectrometer represent crystallization of the melt in a shear stress field and a crystal structure after crystallization, so that the method is simple in process, and simple, convenient and accessible, and the problem that pure gamma phase PVDF thin film cannot be obtained by isothermal crystallization is solved. The gamma phase PVDF thin film which is high in purity, high in orientation and excellent in thermodynamic property can be prepared.

Description

technical field [0001] The invention belongs to the technical field of polyvinylidene fluoride PVDF film preparation, and in particular relates to a method for preparing highly oriented γ-phase polyvinylidene fluoride PVDF film. Background technique [0002] Polyvinylidene fluoride PVDF combines the characteristics of general-purpose resins and fluororesins. In addition to good high temperature resistance, chemical corrosion resistance, oxidation resistance, radiation resistance, and weather resistance, it also has piezoelectricity, dielectricity, Special properties such as pyroelectricity are currently the second largest products in the output of fluorine-containing plastic films. [0003] The diverse performance of PVDF is closely related to its complex and variable crystal structure (α, β, γ, δ, and ε are equal), and various crystal forms can be transformed into each other under certain conditions. However, people generally pay attention to the three crystal forms of α, ...

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Problems solved by technology

[0004] However, the γ crystal phase needs a small degree of undercooling to be obtained. Through melting high-temperature crystallization or high-temperature annealing methods, even at a small degree of undercooling due to the low nucleation and growth rates, a large amount of γ cannot be obtained. crystalline phase, and α crystalline phase also exists in large quantities; the method of successfully preparing γ-type PVDF n