CN110216826A - The expanded polypropylene and its preparation method that can be used for piezoelectric material with orientation hole - Google Patents

The expanded polypropylene and its preparation method that can be used for piezoelectric material with orientation hole Download PDF

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Publication number
CN110216826A
CN110216826A CN201910581575.XA CN201910581575A CN110216826A CN 110216826 A CN110216826 A CN 110216826A CN 201910581575 A CN201910581575 A CN 201910581575A CN 110216826 A CN110216826 A CN 110216826A
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polypropylene
piezoelectric material
mold
pressure
expanded polypropylene
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CN110216826B (en
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曹堃
姜自印
姚臻
徐佳慧
龚昌景
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Zhejiang University ZJU
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Zhejiang University ZJU
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34—Auxiliary operations
    • B29C44/36—Feeding the material to be shaped
    • B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
    • B29C44/42—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length using pressure difference, e.g. by injection or by vacuum
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials
    • H10N30/857—Macromolecular compositions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/10—Polymers of propylene
    • B29K2023/12—PP, i.e. polypropylene

Abstract

The invention discloses a kind of the preparation methods of expanded polypropylene that can be used for piezoelectric material with orientation hole to be then uniformly mixed with supercritical fluid first by polypropylene fusion, obtains uniformly mixed melt；The mass ratio of the polypropylene and supercritical fluid is 1:0.005~0.05；The uniformly mixed melt is injected into inner cavity and is filled in the mold for setting supercritical carbon dioxide, pressure in mold inner-cavity is 8~30Mpa, after uniformly mixed melt injection, by prior to 80~140 DEG C 2~120min of holding of mold, then it is warming up to 150~170 DEG C of 30~240min of holding and foams；Then release cooling and shaping obtains the expanded polypropylene that can be used for piezoelectric material with orientation hole.Foamed material with high-orientation can be prepared using this method, after handling by electric polarization, static pressure electrostrictive coefficient can reach about 590pC/N.

Description

The expanded polypropylene and its preparation method that can be used for piezoelectric material with orientation hole
Technical field
The present invention relates to a kind of technologies for preparing the expanded polypropylene that can be used for piezoelectric material with orientation hole, specifically It is to change polyacrylic thermal history under supercritical fluid atmosphere, the perfect crystallization that inductive formation strand is closely piled up, then It foams in restricted clearance, obtains the polypropylene foam of orientation foam structure, then obtain the piezoelectricity of function admirable to its electric polarization The technology of material.
Background technique
Polypropylene, chemical formula (C3H6) n, 164~170 DEG C of fusing point, household electrical appliance, tubing, high saturating material can be used to prepare Material, film.
PP foam material has the performance advantage of itself in application aspect, but prepares the polypropylene with ideal abscess Foam is current maximum difficulty.The melt strength of plain polypropylene (such as linear isotactic polypropylene) is very low, when temperature reaches When crystalline melt temperature, the melt strength of matrix sharply declines, and blowing temperature window narrows, too low melt strength makes cell wall It is difficult to resist external force, causes abscess to collapse, rupture.So must the polyacrylic foam performance of improved method raising.
The method for improving the foam performance of PP there are two main and widening the blowing temperature section of PP, first is that improving PP base The melt strength of body, including chain modified, blending and modifying of drawing money on credit；Second is that improving foaming technique strategy.The modified linear isotactic of raising is poly- The melt strength of propylene (iPP) has apparent effect to the polypropylene foam of preparation high quality, but these methods improve PP Cost, and the introducing of blend will affect other performances of foamed material, so low melt strength can be utilized directly The polypropylene foam that general purpose grade iPP prepares high quality is more valuable.Chinese patent (publication number CN101580599A) disclose with Macromolecule polyalcohol is raw material, by changing foam process, overcomes in existing foaming technique that saturation time is long, solubility is small Disadvantage greatly improves production efficiency, improves foam structure.
Piezoelectric material is one kind under the action of ambient pressure, can be by itself special material structure, by mechanical energy It is converted into the intellectual material of electric energy.The piezoelectric material applied earliest is mainly the nothing of representative with quartz crystal and inorganic ceramic etc. There is thereafter the organic polymer piezoelectric material with Kynoar (PVDF) for representative in machine piezoelectric material.Twentieth century nine The ten's, Finland scientist Kari Kirjavainen charge to the PP hole prepared, and having prepared first has The hole film of piezoelectric property.Not only piezoelectric modulus is high, flexibility is good but also low in cost for hole type piezoelectric material, so reporting The research boom of a wave hole type piezoelectric material has just been started later.By the development of recent two decades, researchers device to hole The preparation process and optimization method of hole type piezoelectric material have carried out detailed research, and have developed PET, PEN, FEP and PTFE Etc. novel hole piezoelectric material and using die pressing as the new preparation process of representative.It applies more and has realized commercialized at present Mainly foam polypropylene piezoelectric material.After piezoelectricity polypropylene foam through a long time reported in the literature is stable at normal temperature Static pressure electrostrictive coefficient (d33) it is about 200pc/N.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of foaming that can be used for piezoelectric material with orientation hole is poly- The preparation method of propylene can prepare the foamed material with high-orientation using this method, quiet after being handled by electric polarization Piezoelectric modulus can reach about 590pC/N.
In order to solve the above technical problem, the present invention provides a kind of foaming that can be used for piezoelectric material with orientation hole Polyacrylic the preparation method:
It first by polypropylene fusion, is then uniformly mixed with supercritical fluid, obtains uniformly mixed melt；The polypropylene with The mass ratio of supercritical fluid is 1:0.005~0.05；
The uniformly mixed melt is injected into inner cavity and is filled in the mold for setting supercritical carbon dioxide, in mold inner-cavity Pressure be 8~30Mpa, after uniformly mixed melt injection, by prior to 80~140 DEG C 2~120min of holding of mold, then 150~170 DEG C of 30~240min of holding are warming up to foam；Then release cooling and shaping, obtain with orientation hole can Expanded polypropylene for piezoelectric material.
Above-mentioned mold is limited mold, and polypropylene can only be most two-dimensional growths in this three-dimensional of XYZ in mold； That is, the limited mold limits the direction of growth of abscess when foaming, so that polypropylene is in one-dimensional or two-dimensional growth.
The improvement of the preparation method as the expanded polypropylene that can be used for piezoelectric material with orientation hole of the invention:
Melting temperature is 170~220 DEG C (preferably 170~180 DEG C).
Illustrate: the selection principle of melting temperature is as follows, is higher than crystalling propylene melting temperature, so that in polypropylene-base body Crystalline fusion and can process.
As the further of the preparation method with the expanded polypropylene that can be used for piezoelectric material for being orientated hole of the invention It improves:
Injection temperature is 150~180 DEG C (preferably 150~170 DEG C), and injection pressure is 8.5~30.5Mpa.
Illustrate: injection temperature and injection pressure selection principle are as follows: can make supercritical fluid within a short period of time with it is poly- Polypropylene matrix is uniformly mixed and no phase separation generates.That is, melt polypropylene under the plastication of supercritical fluid, has suitable stick It spends and can flow.
This is the temperature and pressure of melt before injecting.
As the further of the preparation method with the expanded polypropylene that can be used for piezoelectric material for being orientated hole of the invention It improves:
Mold temperature is 80~140 DEG C (preferably 80~120 DEG C)；Die pressure is 8~30MPa.
Illustrate: the selection principle of mold original temperature and pressure is as follows: under the plastication of supercritical fluid, the temperature It can induce polypropylene with pressure and generate high-melting-point crystallization.That is, being lower than crystalling propylene melting temperature, enable polypropylene molecular chain It is enough to pile up again, generate a certain amount of dystectic perfect crystallization.
Injection pressure need to be greater than die pressure, to complete to inject.
As the further of the preparation method with the expanded polypropylene that can be used for piezoelectric material for being orientated hole of the invention Improve: injection mold after heat up again temperature achieved (that is, blowing temperature) be 150~170 DEG C (preferably 150~160 DEG C)； Blow pressure is 8~30MPa.
Illustrate: the temperature selection principle achieved that heats up again after uniformly mixed melt injection mold is as follows: in the temperature It spends in range, polypropylene molecular chain has certain mobility, most of crystalline fusion, but also there are a certain amount of perfect knots Crystalline substance, reinforced polypropylene melt strength.In limited foaming process, polyacrylic melt strength is conducive to cell growth, while also can Support abscess deformation.
Pressure can rise when heating, after reaching blow pressure, need to adjust relief valve, make it stable in blow pressure.
As the further of the preparation method with the expanded polypropylene that can be used for piezoelectric material for being orientated hole of the invention It improves:
Supercritical fluid is supercritical CO2, overcritical N2, supercritical methanol, overcritical butane or overcritical chloromethanes.
The supercriticality fluid refers to that temperature is higher than supercritical temperature, while pressure is higher than supercritical pressure, example Such as, supercritical CO2Refer to CO2Temperature be greater than 31.1 DEG C, pressure be higher than 7.4MPa.
In the present invention, fast pressure relief refers to by decompressor such as subtracting high-pressure fluid in a supercritical state Pressure control valve, moment are rapidly depressured, and average decompression rate is up to 5~30MPa/s.
The present invention, which goes back while providing, can be used for piezoelectric material with orientation hole using what method as above was prepared Expanded polypropylene: 1.5~9 times of volume expansion, abscess hole major diameter is 20~200 μm, and the hole degree of orientation is 2~7, and hole density is 105~108A/cm3。
The present invention, which goes back while providing, can be used for piezoelectric material with orientation hole using what method as above was prepared Expanded polypropylene purposes: first it is electrode coated on expanded polypropylene two sides, be then polarised with high voltage electric field, thus Obtain piezoelectric material.
Expanded polypropylene is first applied in a manner of vacuum evaporation, ion sputtering or solution coating etc. on expanded polypropylene two sides Cover electrode.
Electric polarization processing mode is corona charging method or contact mise-a-la-masse method；
The corona charging method are as follows: the voltage of corona charging is -150~-5kv or 5~150kv, and grid voltage is -500 The spacing of~-10000v or 500~10000v, charging temperature≤120 DEG C, charging time 5ms~1h, electrode and film be 1.5~ 10cm；
The contact mise-a-la-masse method are as follows: be connected to the power supply with high pressure on the electrode of expanded polypropylene two sides coating, then Apply the charging of 4~10kv or -4~-10kv voltage to it, the charging time is 5ms~1h.
Technical concept of the invention are as follows: it is contemplated by the invention that it is special that crystallization of the polypropylene under supercritical fluid atmosphere is utilized Sign, first certain pressure and at a temperature of swelling infiltration is carried out to polypropylene melted so that initial crystalline in polypropylene is most of, It is then poured into low temperature to be limited in mold, be crystallized again, dystectic crystallization is contained in the crystallization of generation, to improve molten Body intensity then heats to temperature required for foaming and is further swollen infiltration, and fast pressure relief makes supercritical fluid supersaturated, To be nucleated foaming, the porous, expanded polypropylene with orientation hole is obtained.Finally the porous polypropylene foam of preparation is plated Electrode is placed in electric field, is applied voltage appropriate and is polarised to it, to prepare piezoelectric material.
The technical solution of the present invention is as follows: polypropylene material is melted in an extruder, supercritical fluid is added, it will be overcritical Fluid and melt polypropylene after mixing, are injected into the limited mold of lower temperature；Melt is cooled to mold temperature and lays equal stress on New crystallization certain time；It is warming up to blowing temperature infiltration and swelling a period of time again, fast pressure relief to normal pressure is placed in ice-water bath Middle cooling and shaping obtains finally being plated top electrode with the PP foam material for being uniformly directed hole, applying certain electricity , it is taken out after charging, the piezoelectric material with higher static pressure electrostrictive coefficient can be made.
The present invention is overcome and was foamed by the way of limited foaming by changing foam process using polypropylene as raw material In journey the shortcomings that polypropylene matrix melt strength, polypropylene expanded temperature window has been widened, has improved foam structure, has been obtained uniform It is orientated abscess.Then the foam film with orientation hole of preparation is placed in electric field and is polarized, it is excellent to be transformed into piezoelectric property Different material.The present invention is resulting to have the expanded polypropylene for being uniformly directed hole, after the processing of its electric polarization, static pressure electrostrictive coefficient Between 300~600pC/N.
For existing foaming preparation method, the invention belongs to alternating temperatures to be limited foaming, and which overcome existing hairs Following technological deficiency in brewed Preparation Method:
1, blowing temperature action pane is narrow, and sample quality is unstable after foaming；
2, sample rate is larger after foaming, and cell orientation is poor.
Detailed description of the invention
Fig. 1 is the scanning electron microscope (SEM) photograph for the section that polypropylene is limited foamed sample in embodiment 1；
Fig. 2 is the scanning electron microscope (SEM) photograph for the section that polypropylene is limited foamed sample in embodiment 2；
Fig. 3 is the scanning electron microscope (SEM) photograph for the section that polypropylene is limited foamed sample in embodiment 3；
Fig. 4 is the scanning electron microscope (SEM) photograph for the section that polypropylene is limited foamed sample in embodiment 4；
Fig. 5 is the scanning electron microscope (SEM) photograph for the section that polypropylene is limited foamed sample in embodiment 5；
Fig. 6 is the scanning electron microscope (SEM) photograph for the section that polypropylene is limited foamed sample in comparative example 1.
Specific embodiment
Single screw extrusion machine used in following case, screw rod nominal diameter are 30mm, draw ratio 25.Single screw rod is squeezed Machine is divided into three sections out, and leading portion accounts for the 1/3 of overall length；Middle section accounts for the 1/3 of overall length, and back segment accounts for the 1/3 of overall length；It is set in the section start of leading portion Main feed mouth is set, side entry feed mouth is arranged in the intersection in leading portion and middle section；Polypropylene granules enter extruder from main feed mouth In, supercritical carbon dioxide is added in extruder from the side entry feed mouth from 1/3 overall length of main feed mouth.
The flat plate mold is the limited limited mold in the direction XY, that is, polypropylene can only be along Z long in the mold.
Polypropylene foam film with a thickness of≤500 μm, preferably 100~200 μm.
Following part is parts by weight.
Embodiment 1
100 parts of polypropylene granules are melted in single screw extrusion machine leading portion, front-end temperature is 190 DEG C, and material is preceding The section residence time is about 1.0 minutes；1.5 parts of supercritical carbon dioxide is added in middle section, and material is 1.5 points in the middle section residence time Clock；Back segment is injection portion, polypropylene and supercritical carbon dioxide is injected into after mixing in limited mold, temperature is 175 DEG C, pressure 10Mpa, material is 2.0 minutes in the injection portion residence time；Uniformly mixed melt is discharged when injection.
Then uniformly mixed melt is injected into 175 DEG C, 10Mpa and (is filled with filled with a certain amount of supercritical carbon dioxide Supercritical carbon dioxide until meet setting pressure) flat plate mold in, mold temperature be 100 DEG C, pressure 8Mpa, keep 15min then heats to 165 DEG C, keeps 100min；Finally open pressure reducing valve pressure release (average pressure release rate is about 20Mpa/s) Foaming, and the mold after pressure release is cooled to 20 DEG C, so that polypropylene abscess is formed；Obtain polypropylene foam film.
Resulting polypropylene foam film carries out following performance test:
1, polypropylene foam film two sides is coated into copper electrode, applies 8kv voltage, between electrodes to contact charging modes By its electric polarization, charge 15s, measures its static pressure electrostrictive coefficient and is up to about 520pC/N.
2, polypropylene foam film is impregnated into liquid nitrogen 30min, the hole knot of scanning electron microscope characterization section is utilized after brittle failure Structure.As shown in Figure 1, the expansion ratio of limited expanded polypropylene sample is 5.5, abscess major diameter is 80~200 μm, and the degree of orientation is 4.4, cell density is 8.2 × 107A/cm3。
Embodiment 2
100 parts of polypropylene granules are melted in single screw extrusion machine leading portion, front-end temperature is 175 DEG C；Middle section is added 3.6 parts of supercritical carbon dioxide；Back segment is injection portion, by polypropylene and supercritical carbon dioxide be injected into after mixing by It limits in mold, temperature is 168 DEG C, pressure 16Mpa；Uniformly mixed melt is discharged when injection.
Then uniformly mixed melt is injected into 168 DEG C, 16Mpa and (is filled with filled with a certain amount of supercritical carbon dioxide Supercritical carbon dioxide until meet setting pressure) flat plate mold in, mold temperature be 120 DEG C, pressure 14Mpa, protect 4min is held, then heats to 163 DEG C, keeps 240min；Finally open pressure reducing valve pressure release (average pressure release rate is about 10Mpa/s) Foaming, and the mold after pressure release is cooled to 20 DEG C, so that polypropylene abscess is formed；Obtain polypropylene foam film.
Resulting polypropylene foam film carries out following performance test:
1, polypropylene foam film two sides is coated into copper electrode, applies 8kv voltage, between electrodes to contact charging modes By its electric polarization, charge 80s, measures its static pressure electrostrictive coefficient and is up to about 410pC/N.
2, polypropylene foam film is impregnated into liquid nitrogen 30min, the hole knot of scanning electron microscope characterization section is utilized after brittle failure Structure.As shown in Fig. 2, the expansion ratio of limited expanded polypropylene sample is 8.5, abscess major diameter is 80~200 μm, and the degree of orientation is 3.5, cell density is 6.5 × 107A/cm3。
Embodiment 3
100 parts of polypropylene granules are melted in single screw extrusion machine leading portion, front-end temperature is 180 DEG C；Middle section is added 2.8 parts of supercritical carbon dioxide；Back segment is injection portion, by polypropylene and supercritical carbon dioxide be injected into after mixing by It limits in mold, temperature is 151 DEG C, pressure 28Mpa；Uniformly mixed melt is discharged when injection.
Then uniformly mixed melt is injected into 151 DEG C, 28Mpa and (is filled with filled with a certain amount of supercritical carbon dioxide Supercritical carbon dioxide until meet setting pressure) flat plate mold in, mold temperature be 120 DEG C, pressure 25Mpa, protect 84min is held, then heats to 153 DEG C, keeps 240min；Finally opening pressure reducing valve pressure release, (average pressure release rate is about 15Mpa/ S) it foams, and the mold after pressure release is cooled to 10 DEG C, so that polypropylene abscess is formed；Obtain polypropylene foam film.
Resulting polypropylene foam film carries out following performance test:
1, polypropylene foam film two sides is coated into platinum electrode, applies 8kv voltage, between electrodes to contact charging modes By its electric polarization, charge 210s, measures its static pressure electrostrictive coefficient and is up to about 590pC/N.
2, polypropylene foam film is impregnated into liquid nitrogen 30min, the hole knot of scanning electron microscope characterization section is utilized after brittle failure Structure.As shown in figure 3, the expansion ratio of limited expanded polypropylene sample is 4.7, abscess major diameter is 120~200 μm, and the degree of orientation is 6.6, cell density is 4.0 × 107A/cm3。
Embodiment 4
100 parts of polypropylene granules are melted in single screw extrusion machine leading portion, front-end temperature is 220 DEG C；Middle section is added 0.7 part of supercritical carbon dioxide；Back segment is injection portion, by polypropylene and supercritical carbon dioxide be injected into after mixing by It limits in mold, temperature is 159 DEG C, pressure 20Mpa；Uniformly mixed melt is discharged when injection.
Then uniformly mixed melt is injected into 159 DEG C, 20Mpa and (is filled with filled with a certain amount of supercritical carbon dioxide Supercritical carbon dioxide until meet setting pressure) flat plate mold in, mold temperature be 140 DEG C, pressure 16Mpa, protect 2min is held, then heats to 158 DEG C, keeps 120min；Finally open pressure reducing valve pressure release (average pressure release rate is about 12Mpa/s) Foaming, and the mold after pressure release is cooled to 20 DEG C, so that polypropylene abscess is formed；Obtain polypropylene foam film.
Resulting polypropylene foam film carries out following performance test:
1, polypropylene foam film two sides is coated into copper electrode, applies 8kv voltage, between electrodes to contact charging modes By its electric polarization, charge 19min, measures its static pressure electrostrictive coefficient and is up to about 310pC/N.
2, polypropylene foam film is impregnated into liquid nitrogen 30min, the hole knot of scanning electron microscope characterization section is utilized after brittle failure Structure.As shown in figure 4, the expansion ratio of limited expanded polypropylene sample is 3.5, abscess major diameter is 60~150 μm, and the degree of orientation is 3.8, cell density is 6.4 × 107A/cm3。
Embodiment 5
100 parts of polypropylene granules are melted in single screw extrusion machine leading portion, front-end temperature is 200 DEG C；Middle section is added 2.0 parts of supercritical carbon dioxide；Back segment is injection portion, by polypropylene and supercritical carbon dioxide be injected into after mixing by It limits in mold, temperature is 156 DEG C, pressure 14Mpa；Uniformly mixed melt is discharged when injection.
Then uniformly mixed melt is injected into 156 DEG C, 14Mpa and (is filled with filled with a certain amount of supercritical carbon dioxide Supercritical carbon dioxide until meet setting pressure) flat plate mold in, mold temperature be 80 DEG C, pressure 12Mpa, keep 10min then heats to 157 DEG C, keeps 240min；Finally open pressure reducing valve pressure release (average pressure release rate is about 30Mpa/s) Foaming, and the mold after pressure release is cooled to 15 DEG C, so that polypropylene abscess is formed；Obtain polypropylene foam film.
Resulting polypropylene foam film carries out following performance test:
1, polypropylene foam film two sides is coated into platinum electrode, applies 8kv voltage, between electrodes to contact charging modes By its electric polarization, charge 10ms, measures its static pressure electrostrictive coefficient and is up to about 480pC/N.
2, polypropylene foam film is impregnated into liquid nitrogen 30min, the hole knot of scanning electron microscope characterization section is utilized after brittle failure Structure.As shown in figure 5, the expansion ratio of limited expanded polypropylene sample is 6.4, abscess major diameter is 50~200 μm, and the degree of orientation is 4.1, cell density is 4.5 × 107A/cm3。
Comparative example 1
Raw material described in embodiment 3 is carried out according to existing isothermal foaming the preparation method, specific process parameter are as follows:
100 parts of polypropylene granules are melted in single screw extrusion machine leading portion, front-end temperature is 180 DEG C；Middle section is added 2.8 parts of supercritical carbon dioxide；Back segment is injection portion, by polypropylene and supercritical carbon dioxide be injected into after mixing by It limits in mold, temperature is 151 DEG C, pressure 28Mpa；Uniformly mixed melt is discharged when injection.
Then uniformly mixed melt is injected into 151 DEG C, 28Mpa and (is filled with filled with a certain amount of supercritical carbon dioxide Supercritical carbon dioxide until meet setting pressure) flat plate mold in, mold temperature be 155 DEG C, pressure 25Mpa, protect Hold 324min；Pressure reducing valve pressure release (average pressure release rate is about 15Mpa/s) foaming is finally opened, and the mold after pressure release is cooled down To 10 DEG C, so that polypropylene abscess is formed；Obtain polypropylene foam film.
Resulting expanded polypropylene is prepared into piezoelectric material according to 3 the method for embodiment, measures its static pressure electrostrictive coefficient about For 100pC/N, scanning electron microscope (SEM) photograph is as shown in Figure 6.
The above list is only a few specific embodiments of the present invention for finally, it should also be noted that.Obviously, this hair Bright to be not limited to above embodiments, acceptable there are many deformations.Those skilled in the art can be from present disclosure All deformations for directly exporting or associating, are considered as protection scope of the present invention.

Claims (9)

1. the preparation method with the expanded polypropylene that can be used for piezoelectric material of orientation hole, it is characterised in that:
It first by polypropylene fusion, is then uniformly mixed with supercritical fluid, obtains uniformly mixed melt；The polypropylene faces with super The mass ratio of boundary's fluid is 1:0.005~0.05；
The uniformly mixed melt is injected into inner cavity and is filled in the mold for setting supercritical carbon dioxide, the pressure in mold inner-cavity Power is 8~30Mpa, after uniformly mixed melt injection, by prior to 80~140 DEG C 2~120min of holding of mold, then is heated up It foams to 150~170 DEG C of 30~240min of holding；Then release cooling and shaping obtains can be used for orientation hole The expanded polypropylene of piezoelectric material.
2. the preparation method of the expanded polypropylene that can be used for piezoelectric material with orientation hole according to claim 1, Be characterized in that: melting temperature is 170~220 DEG C.
3. the preparation method of the expanded polypropylene that can be used for piezoelectric material with orientation hole according to claim 1 or 2, It is characterized by: injection temperature is 150~180 DEG C, injection pressure is 8.5~30.5Mpa.
4. the preparation method of the expanded polypropylene that can be used for piezoelectric material with orientation hole according to claim 3, Be characterized in that: mold temperature is 80~120 DEG C；Die pressure is 8~30MPa.
5. the preparation method of the expanded polypropylene that can be used for piezoelectric material with orientation hole according to claim 4, Be characterized in that: the temperature achieved that heats up again after injection mold is 150~170 DEG C；Blow pressure is 8~30MPa.
6. the system of any expanded polypropylene that can be used for piezoelectric material with orientation hole according to claim 1~5 Standby method, it is characterised in that: supercritical fluid is supercritical CO2, overcritical N2, supercritical methanol, overcritical butane or overcritical chlorine Methane.
7. the foaming that can be used for piezoelectric material with orientation hole being prepared using such as claim 1~6 either method Polypropylene, it is characterised in that: 1.5~9 times of volume expansion, abscess hole major diameter is 20~200 μm, and the hole degree of orientation is 2~7, hole Density is 105~108A/cm3。
8. the foaming that can be used for piezoelectric material with orientation hole being prepared using such as claim 1~6 either method Polyacrylic purposes, it is characterised in that: it is first electrode coated on expanded polypropylene two sides, then carried out at polarization with high voltage electric field Reason, to obtain piezoelectric material.
9. purposes according to claim 8, it is characterised in that: electric polarization processing mode is corona charging method or contact charging Method；
The corona charging method are as follows: the voltage of corona charging be -150~-5kv or 5~150kv, grid voltage be -500~- The spacing of 10000v or 500~10000v, charging temperature≤120 DEG C, charging time 5ms~1h, electrode and film be 1.5~ 10cm；
The contact mise-a-la-masse method are as follows: be connected to the power supply with high pressure on the electrode of expanded polypropylene two sides coating, then to it Apply the charging of 4~10kv or -4~-10kv voltage, the charging time is 5ms~1h.
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CN112497556A (en) * 2020-10-28 2021-03-16 泰州诺盟新材料科技有限公司 Method for manufacturing polypropylene composite material

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