CN101045795A - Beta phase polyvinylidene fluoride composite film and preparation method thereof - Google Patents

Abstract

This invention relates to a kind of beta phase polyvinylidene difluoride film laminate and its preparation method. The composition and quality ratio: inorganic hydrated salt 1 to 20 percent, polyvinylidene fluoride 80 to 99 percent; the inorganic hydrated salt is: Fe ( NO3) 3. 9H2O, Ni ( NO3) 2. 6H2O, or Co ( NO3) 2. 6H2O; The polyvinylidene fluoride is: polyvinylidene fluoride homopolymer or polyvinylidene fluoride- hexafluoropropylene copolymer. According to certain quality composition, dissolve polyvinylidene fluoride and inorganic hydrated salt in dimethyl formamide solvent, after misce bene, spincoating on glass or silicon chip, evaporate and crystallize for 24 hours at 20 to 100 deg, obtain polyvinylidene fluoride film laminate. This method avoids using of noxious solvent hexametapol.

Description

A kind of beta phase polyvinylidene fluoride composite film and preparation method thereof

Technical field

The invention belongs to the piezoelectric polymeric materials field, particularly a kind of beta phase polyvinylidene fluoride composite film and preparation method thereof.

Background technology

Polyvinylidene difluoride (PVDF) (PVDF) piezoelectric compare with traditional piezoelectric ceramics have that flexibility is good, specific acoustic resistance is low, with the human body coupling, can be made into advantage such as big area film forming, used widely in industries such as space flight, electronics, medical treatment.

PVDF has α, β, four crystallization phasess of γ, δ, and wherein α does not possess piezoelectric activity, β phase piezoelectric activity maximum mutually.Yet fusion-crystallization commonly used or solution crystallization can only obtain not having the α phase or the active γ phase of the low tension PVDF film of piezoelectric activity, therefore how to obtain the preparation key that β phase PVDF film becomes the PVDF piezoelectric membrane.Studies show that stretches α phase PVDF film at a certain temperature with certain stretch ratio can make α change the β phase mutually into, thereby obtains β phase film.This method is widely used in preparation PVDF piezoelectric membrane because of it is simple.Yet this method also has its limitation, can only prepare the film of thickness more than 20 μ m, seems unable to do what one wishes for the film of thickness below 20 μ m.And bigger thickness has determined the PVDF piezoelectric membrane of stretching polarization method preparation to have bigger damping, makes film be difficult to have high frequency response, has limited the application of film in the high frequency field.

The develop rapidly of MEMS (micro electro mechanical system) (MEMS) is also more and more higher to the performance requriements of piezoelectric membrane in recent years, and the size of the many microstructures in the MEMS field is little, structural strength is low, very difficult tensile PVDF film well is bonded on the microstructure, realizes the application of PVDF piezoelectricity functional materials in the MEMS field.If can β phase PVDF film be produced on the microstructure then can overcome by solution and be difficult to bonding shortcoming.In addition, formulations prepared from solutions PVDF film can be done any regulation and control to film thickness by the concentration and the processing conditions that change solution.PVDF often can only obtain α phase or γ phase film after being dissolved in organic solvent, can obtain β phase PVDF film though there is report PVDF to be dissolved in hexamethylphosphoramide (HMPA) solvent in crystallizing at room temperature, yet the toxicity of HMPA has limited the application of these class methods.

Summary of the invention

The present invention is dissolved in a certain proportion of PVDF and inorganic hydrated salt in dimethyl formamide (DMF) solvent and is made into mixing solutions, then solution is spun on glass or the silicon substrate and carries out evaporative crystallization at a certain temperature.Thereby obtain having the β phase PVDF film of piezoelectric activity.Inorganic hydrated salt has played the effect of nucleator in this class material, has improved the content of β in the PVDF film significantly, and make β phase film have excellent temperature stability.

The invention provides a kind of β phase PVDF laminated film, the material prescription and the quality percentage of described β phase PVDF laminated film are: inorganic hydrated salt 1～20%, and PVDF 80～99%;

Described inorganic hydrated salt is: Fe (NO ₃) ₃9H ₂O, Ni (NO ₃) ₂6H ₂O or Co (NO ₃) ₂6H ₂O;

Described PVDF is: PVDF homopolymer or polyvinylidene difluoride (PVDF)-R 1216 (PVDF-HFP) multipolymer.

The step and the condition of method of the present invention are as follows:

(1) batching: take by weighing inorganic hydrated salt and PVDF according to above-mentioned prescription;

(2) join sample: it is 20% solution that the inorganic hydrated salt of (1) batching and PVDF are dissolved in the solvent dimethylformamide preparation mass percent concentration,, mixes the solution that obtains mixing with solution stirring;

(3) moulding: with the above-mentioned solution that mixes, being spun on glass or the silicon substrate with sol evenning machine, is evaporative crystallization 24 hours under 20～100 ℃ of conditions in temperature, obtains a kind of beta phase polyvinylidene fluoride composite film.

The invention has the beneficial effects as follows: mix that by simple solution inorganic hydrated salt is filled in the PVDF matrix as nucleator, make PVDF solution to generate β phase at the wide temperature range intercrystalline with piezoelectric activity.This method has been avoided the use of virose HMPA solvent, and all raw materials are common agents, and are simple.

Description of drawings

Fig. 1: the infrared spectrum of PVDF-HFP film, wherein Fig. 1 (a)～(d) is respectively pure PVDF-HFP film, doped F e (NO ₃) ₃9H ₂The PVDF-HFP film of O, Ni doped (NO ₃) ₂6H ₂The PVDF-HFP film of O and doping Co (NO ₃) ₂6H ₂The PVDF-HFP film of O.Vibrational band 1276cm ^-1Characteristic absorption band for the β phase.

Fig. 2: doping different mass percentage composition Fe (NO ₃) ₃9H ₂The PVDF film infrared spectrogram of O, wherein Fig. 2 (a)～(d) Fe (NO ₃) ₃9H ₂The content difference 1%, 5%, 10% and 20% of O.

Embodiment

Embodiment 1

With mass percent concentration 5% Fe (NO ₃) ₃9H ₂O and mass percent concentration are that 95% PVDF-HFP is dissolved among the DMF, and the preparation mass percent concentration is 20% solution, with solution stirring, after mixing, be spun on the glass substrate, in 60 ℃ of crystallization and evaporations 24 hours, β phase PVDF film.Detected result as shown in Figure 1.

Embodiment 2

Concentration is with 5%Fe (NO by mass percentage ₃) ₃9H ₂O and mass percent concentration are that 95% PVDF-HFP is dissolved among the DMF, and the preparation mass percent concentration is 20% solution, with solution stirring, after mixing, be spun on the glass substrate, in 60 ℃ of crystallization and evaporations 24 hours, β phase PVDF film.Outcome record is in Fig. 1.

Embodiment 3

With mass percent concentration 5% Co (NO ₃) ₂6H ₂O and mass percent concentration are that 95% PVDF-HFP is dissolved among the DMF, and the preparation mass percent concentration is 20% solution, with solution stirring, after mixing, be spun on the glass substrate, after mixing, be spun on the silicon substrate, in 60 ℃ of crystallization and evaporations 24 hours, β phase PVDF film.Outcome record is in Fig. 1.

Embodiment 4

With mass percent concentration 1% Fe (NO ₃) ₃9H ₂O and mass percent concentration are that 99% PVD is dissolved among the DMF, and the preparation mass percent concentration is 20% solution, with solution stirring, after mixing, be spun on the glass substrate, in 60 ℃ of crystallization and evaporations 24 hours, β phase PVDF film.Outcome record is in Fig. 2.

Embodiment 5

With mass percent concentration 1% Fe (NO ₃) ₃9H ₂O and mass percent concentration are that 99% PVDF is dissolved among the DMF, and the preparation mass percent concentration is 20% solution, with solution stirring, after mixing, be spun on the glass substrate, in 80 ℃ of crystallization and evaporations 24 hours, β phase PVDF film.Outcome record is in Fig. 2.

Embodiment 6

With mass percent concentration 10% Fe (NO ₃) ₃9H ₂O and mass percent concentration are that 90% PVD is dissolved among the DMF, and the preparation mass percent concentration is 20% solution, with solution stirring, after mixing, be spun on the silicon substrate, in 100 ℃ of crystallization and evaporations 24 hours, β phase PVDF film.Outcome record is in Fig. 2.

Embodiment 7

With mass percent concentration 20% Fe (NO ₃) ₃9H ₂O and mass percent concentration are that 80% PVDF is dissolved among the DMF, and the preparation mass percent concentration is 20% solution, with solution stirring, after mixing, be spun on the silicon substrate, in 50 ℃ of crystallization and evaporations 24 hours, β phase PVDF film.Outcome record is in Fig. 2.

Claims (3)

1. a beta phase polyvinylidene fluoride composite film is characterized in that the mass percent prescription of material is: inorganic hydrated salt 1～20%, polyvinylidene difluoride (PVDF) 80～99%;

Described inorganic hydrated salt is: Fe (NO ₃) ₃9H ₂O, Ni (NO ₃) ₂6H ₂O or Co (NO ₃) ₂6H ₂O;

Described polyvinylidene difluoride (PVDF) is: polyvinylidene fluoride homopolymer or polyvinylidene difluoride (PVDF)-hexafluoropropylene copolymer.

2. a kind of preparation method of beta phase polyvinylidene fluoride composite film according to claim 1 is characterized in that step and condition are:

(1) batching: the prescription according to described material takes by weighing inorganic hydrated salt and polyvinylidene difluoride (PVDF);

(2) join sample: it is 20% solution that the inorganic hydrated salt of (1) batching and polyvinylidene difluoride (PVDF) are dissolved in the solvent dimethylformamide preparation mass percent concentration,, mixes the solution that obtains mixing with solution stirring;

(3) moulding: with the above-mentioned solution that mixes, being spun on glass or the silicon substrate with sol evenning machine, is evaporative crystallization under 20～100 ℃ of conditions in temperature, obtains a kind of beta phase polyvinylidene fluoride composite film.

3, as the preparation method of a kind of beta phase polyvinylidene fluoride composite film as described in the claim 2, it is characterized in that described inorganic hydrated salt is: Fe (NO ₃) ₃9H ₂O, Ni (NO ₃) ₂6H ₂O or Co (NO ₃) ₂6H ₂O;

Described polyvinylidene difluoride (PVDF) is: polyvinylidene fluoride homopolymer or polyvinylidene difluoride (PVDF)-hexafluoropropylene copolymer.

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