Preparation method of PVDF piezoelectric induction film, piezoelectric sensor and application of piezoelectric sensor in rail gnawing of crane
阅读说明：本技术 一种pvdf压电感应薄膜的制备方法和压电传感器及其在起重机啃轨中的应用 (Preparation method of PVDF piezoelectric induction film, piezoelectric sensor and application of piezoelectric sensor in rail gnawing of crane ) 是由 王水明 施永昌 沈策 胡萍 李军 夏乐 吕宽新 蒋龙 赵碧霞 于 2020-12-22 设计创作，主要内容包括：本发明提供了一种PVDF压电感应薄膜的制备方法和压电传感器及其在起重机啃轨中的应用,方法包括以下步骤:将PVDF初始膜进行拉伸,保温,冷却后极化,降温后再磁控溅射,得到PVDF压电感应薄膜；所述PVDF压电薄膜中压电相含量为70～75％。本发明采用拉伸方法对PVDF膜改性,诱导薄膜内发生相变,生成压电β相,相较于初始薄膜,压电相含量增加了3.5～4倍。该PVDF压电感应薄膜具有较大的静态压电系数。该薄膜制备的压电传感器能够用于起重机的防啃轨监测中。(The invention provides a preparation method of a PVDF piezoelectric induction film, a piezoelectric sensor and application of the PVDF piezoelectric induction film in rail gnawing of a crane, wherein the method comprises the following steps of stretching a PVDF initial film, preserving heat, polarizing after cooling, performing magnetron sputtering after cooling to obtain the PVDF piezoelectric induction film; the content of a piezoelectric phase in the PVDF piezoelectric film is 70-75%. According to the invention, the PVDF film is modified by a stretching method, phase change in the film is induced, and a piezoelectric beta phase is generated, and compared with an initial film, the piezoelectric phase content is increased by 3.5-4 times. The PVDF piezoelectric induction film has a larger static piezoelectric coefficient. The piezoelectric sensor prepared by the film can be used for rail gnawing prevention monitoring of a crane.)
1. A preparation method of a PVDF piezoelectric induction film comprises the following steps:
stretching the PVDF initial film, preserving heat, cooling, polarizing, cooling, and performing magnetron sputtering to obtain a PVDF piezoelectric induction film;
the content of a piezoelectric phase in the PVDF piezoelectric induction film is 70-75%.
2. The method according to claim 1, wherein the temperature of the drawing is 85 to 95 ℃, and the draw ratio is 3.5 to 4.5; the drawing speed is 18-22 mm/min.
3. The preparation method according to claim 1, wherein the temperature of the heat preservation is 85-95 ℃, and the time of the heat preservation is 18-23 min;
the tensile force of the stretching is kept during the cooling process.
4. The production method according to claim 1, characterized in that the polarization is performed in a silicone oil;
the temperature of polarization is 85-95 ℃; the polarization time is 20-60 min.
5. The preparation method according to claim 1, wherein the temperature is reduced to 20-30 ℃.
6. The method according to claim 1, wherein the sputtering growth vacuum degree is 10-3～10-5Pa, gas pressure of 1-5 Pa, sputtering power of 50-120W, growth time of 1-3 min (Pt) and 5-10 min (Au).
7. A piezoelectric sensor includes a PVDF piezoelectric sensing film;
the epoxy resin adhesive layer is coated on the surface of the PVDF film;
and a rubber layer coated on the surface of the epoxy resin adhesive layer;
the PVDF piezoelectric film is prepared by the preparation method of any one of claims 1-6.
8. The piezoelectric sensor of claim 7, wherein the epoxy glue layer is selected from a PET glue layer or a polyimide glue layer.
9. Use of the piezoelectric sensor according to any one of claims 7 to 8 in crane rail gnawing prevention monitoring.
Technical Field
The invention belongs to the technical field of piezoelectric films, and particularly relates to a preparation method of a PVDF piezoelectric induction film, a piezoelectric sensor and application of the PVDF piezoelectric induction film in rail gnawing of a crane.
Background
The rail gnawing means that under the normal operation condition of the crane, the wheel rim of the crane is not in contact with the side face of the rail, a certain gap is reserved between the wheel rim and the rail, and the maximum gap is generally designed to be 30-40 mm. However, the contact between the wheel rim and the side surface of the rail generates horizontal lateral thrust, so that the contact surface between the running wheel and the rail is not positioned in the middle of the tread (namely, the center line of the tread of the wheel is not superposed with the center line of the rail), the vehicle body deflects, and the whole crane is contacted and walks against one side of the rail, thereby generating rail gnawing. Gnawing the rail and can make the life of wheel reduce greatly, aggravate orbital wearing and tearing, make the stability of cart dolly of hoist reduce, influence production efficiency, can cause the cart to derail even when serious, cause the incident.
At present, the interference phenomenon caused by the error of a crane body is generally solved by adjusting the speeds of the trolleys on two sides to keep the actual walking distances of the wheels on two sides consistent, but the deviation of the track distance is required to be ensured within a small range. However, in this method, the track and the wheel still have very serious interference phenomena, as shown in fig. 1.
Disclosure of Invention
In view of this, the present invention aims to provide a preparation method of a PVDF piezoelectric sensing film, a piezoelectric sensor and an application of the piezoelectric sensor in a crane rail gnawing, where the piezoelectric sensing film prepared by the method has a strong piezoelectric property.
The invention provides a preparation method of a PVDF piezoelectric induction film, which comprises the following steps:
stretching the PVDF initial film, preserving heat, cooling, polarizing, cooling, and performing magnetron sputtering to obtain a PVDF piezoelectric induction film;
the content of a piezoelectric phase in the PVDF piezoelectric induction film is 70-75%.
Preferably, the stretching temperature is 85-95 ℃, and the stretching ratio is 3.5-4.5; the drawing speed is 18-22 mm/min.
Preferably, the heat preservation temperature is 85-95 ℃, and the heat preservation time is 18-23 min;
the tensile force of the stretching is kept during the cooling process.
Preferably, said poling is performed in silicone oil;
the temperature of polarization is 85-95 ℃; the polarization time is 20-60 min.
Preferably, the temperature is reduced to 20-30 ℃.
Preferably, the vacuum degree of the sputtering growth is 10-3～10-5Pa, gas pressure of 1-5 Pa, sputtering power of 50-120W, growth time of 1-3 min (Pt) and 5-10 min (Au).
The invention provides a piezoelectric sensor, which comprises a PVDF piezoelectric induction film;
an epoxy resin adhesive layer coated on the PVDF film;
and a rubber layer coated on the surface of the epoxy resin adhesive layer;
the PVDF piezoelectric film is prepared by the preparation method of the technical scheme.
Preferably, the epoxy glue layer is selected from a PET glue layer or a polyimide glue layer.
The invention provides an application of the piezoelectric sensor in the technical scheme in rail gnawing prevention monitoring of a crane.
The invention provides a preparation method of a PVDF piezoelectric induction film, which comprises the following steps of stretching a PVDF initial film, preserving heat, polarizing after cooling, performing magnetron sputtering after cooling to obtain the PVDF piezoelectric induction film; the content of a piezoelectric phase in the PVDF piezoelectric film is 70-75%. According to the invention, the PVDF film is modified by a stretching method, phase change in the film is induced, and a piezoelectric beta phase is generated, and compared with an initial film, the piezoelectric phase content is increased by 3.5-4 times. The PVDF piezoelectric induction film has a larger static piezoelectric coefficient. The piezoelectric sensor prepared by the film can be used for rail gnawing prevention monitoring of a crane.
Drawings
FIG. 1 is a schematic view illustrating a phenomenon between a rail and a wheel in the prior art;
FIG. 2 is a schematic structural diagram of a piezoelectric sensor according to the present invention;
fig. 3 is a schematic view of the position of the piezoelectric sensor additionally arranged on the track.
Detailed Description
The invention provides a preparation method of a PVDF piezoelectric induction film, which comprises the following steps:
stretching the PVDF initial film, preserving heat, cooling, polarizing, cooling, and performing magnetron sputtering to obtain a PVDF piezoelectric induction film;
the content of a piezoelectric phase in the PVDF piezoelectric induction film is 70-75%.
According to the invention, the PVDF film is modified by a stretching method, phase change in the film is induced, and a piezoelectric beta phase is generated, and compared with an initial film, the piezoelectric phase content is increased by 3.5-4 times. The PVDF piezoelectric induction film has a larger static piezoelectric coefficient.
In the present invention, the PVDF initial film is preferably prepared as follows:
dissolving polyvinylidene fluoride powder in N-methyl pyrrolidone, stirring at 60-90 ℃ for 55-65 min, removing bubbles, and performing tape casting to form a film, thereby obtaining the PVDF initial film.
In the invention, the method is preferably kept stand in vacuum for 35-45 min to remove bubbles. The film forming temperature is 115-125 ℃, and more preferably 120 ℃; the drying time is 55-65 min, and more preferably 60 min.
In the invention, the thickness of the PVDF piezoelectric induction film is preferably 30-50 μm.
PVDF is a semi-crystalline high molecular polymer, a crystal region of the PVDF has a plurality of crystal phase structures, and at least four crystal phase structures observed in the current experiment are alpha phase, beta phase, gamma phase and delta phase. Wherein the alpha phase has no piezoelectricity. The beta phase is the most polar phase of PVDF. The gamma phase is slightly polar. The most studied phase structures in PVDF materials are the alpha and beta phases. Normal PVDF exists primarily as the α -phase with the lowest molecular potential, while its piezoelectricity depends primarily on the polar β -phase. Because the beta-phase molecular chain structure forms a strong electric dipole moment, the microstructure of the molecular chain is changed under the action of external force, so that the original electric neutrality is destroyed, and bound charges are released.
The invention adopts a stretcher to stretch. The stretching temperature is 85-95 ℃, and the stretching ratio is 3.5-4.5; the drawing speed is 18-22 mm/min. In a specific example, the stretching temperature is 90 ℃, the stretching ratio is 4, and the stretching rate is 20 mm/min.
Stopping stretching after reaching the specified stretching ratio, and keeping the temperature; the heat preservation temperature is 85-95 ℃, and the heat preservation time is 18-23 min; in a specific embodiment, the temperature for heat preservation is 90 ℃ and the time is 20 min.
Preserving heat and then cooling; the invention cools while maintaining the tension.
After cooling, polarization is carried out. The temperature of polarization is preferably 85-95 ℃; the time for polarization is preferably 20-60 min, more preferably 35-45 min, and most preferably 40 min. The invention clamps the cooled PVDF film between a pair of plane electrodes, dips under the liquid level of the silicon oil, heats and polarizes. The polarization adopts direct current high voltage; the polarization electric field is 50-100 mV/m.
The temperature of the silicone oil is preferably reduced to normal temperature by keeping the polarization electric field at 85-95 mV/m, more preferably reduced to 20-30 ℃ at 90 mV/m; the electric field is then removed and the polarization is complete.
The invention provides a piezoelectric sensor, which comprises a PVDF piezoelectric induction film;
performing magnetron sputtering on the film on the surface of the PVDF piezoelectric film; during magnetron sputtering, two mask plates are adopted to place the polarized film in the middle, and then the film is placed on a magnetron sputtering sample table for sputtering; the vacuum degree of the sputtering growth is 10-3～10-5Pa, gas pressure of 1-5 Pa, sputtering power of 50-120W, growth time of 1-3 min (Pt) and 5-10 min (Au).
The epoxy resin adhesive layer is coated on the surface of the film;
and a rubber layer coated on the surface of the epoxy resin adhesive layer;
the PVDF piezoelectric film is prepared by the preparation method of the technical scheme.
Fig. 2 is a schematic structural diagram of a piezoelectric sensor provided in the present invention.
In the present invention, the epoxy glue layer is preferably selected from a PET glue layer or a polyimide glue layer.
The thickness of the epoxy resin adhesive layer is 400-500 mu m; the thickness of the rubber layer is 0.5-1 cm.
The piezoelectric sensor is an early warning device, and plays a role in alarming in rail gnawing monitoring of a crane.
The invention provides an application of the piezoelectric sensor in the technical scheme in rail gnawing prevention monitoring of a crane.
When the cart is in a rail gnawing phenomenon in the walking process, the cart bears changed external acting forces, the changed external acting forces promote the PVDF film to deform, the polarization phenomenon can be generated in the PVDF film, meanwhile, opposite positive and negative charges can be generated on two opposite surfaces of the PVDF film, and the PVDF film can restore to an uncharged state after the external acting forces are removed, namely, the charges caused by the deformation of the PVDF film change. The charge signal generated by the PVDF piezoelectric film can be collected only after being converted into a voltage signal through a charge amplifier, and the charge amplifier is an operational amplifier with deep negative feedback capacitance and high gain. Since the PVDF piezoelectric sensor generates weak electric signals and has large internal resistance, the pre-charge amplifier is used for amplifying the weak electric signals and converting the high-impedance output of the piezoelectric sensor into the low-impedance output of the pre-charge amplifier. The PVDF piezoelectric sensor signal acquisition process is as follows:
piezoelectric sensor → charge amplifier → filter → oscilloscope → computer.
The pressure change of the wheels in the running process of the cart is converted into a voltage signal through the processes of amplification, filtration, collection and the like, so that the dynamic pressure distribution is acquired, and the relevant information in the running process of the cart is acquired.
The piezoelectric sensor is additionally arranged between the track and the wheel (as a schematic diagram shown in figure 3), and the piezoelectric effect of the piezoelectric film is utilized to convert mechanical energy into electric energy so as to detect the gap between the inner rim of the wheel of the cart and the track. The piezoelectric induction film is placed on the inner side of the wheel, and when the protective early warning material on the wheel contacts with the track, a piezoelectric signal is generated to judge whether to gnaw the track. The invention improves the detection precision through the piezoelectric sensing film, the piezoelectric sensing film is made of flexible organic materials, has stronger piezoelectric property and higher mechanical strength, has wide frequency response range, can resist chemical and oily corrosion, has small volume and simple structure, can be adhered to the surface of the material, and has good compatibility with the structure. The piezoelectric sensing film is used for detecting the pressure change of the track, so that the track gnawing is avoided.
In order to further illustrate the present invention, the following will describe the preparation method of a PVDF piezoelectric sensing film and the piezoelectric sensor in detail with reference to the examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Mixing and dissolving 10g of polyvinylidene fluoride (PVDF) powder and 100ml of N-methylpyrrolidone (NMP), magnetically stirring for 60min at 70 ℃, standing for 40min under vacuum to remove bubbles, pouring into a casting dish, placing in a drying box, volatilizing the NMP by heating and evaporating, wherein the film forming temperature is 120 ℃, and the drying time is 60min, namely, a PVDF initial film is formed on the casting dish. And (3) placing the prepared PVDF initial film into a stretching machine, keeping the stretching temperature at 85 ℃ by using a temperature control machine, setting the stretching rate after the temperature is constant, stretching, wherein the stretching ratio R is 4.5, the stretching rate is 22mm/min, and stopping stretching after the specified stretching ratio is reached. Adjusting a temperature control machine to a proper temperature, preserving heat for a certain time, preserving heat for 20min at 90 ℃, and cooling under the condition of keeping tension;
and (3) clamping the cooled initial PVDF film between a pair of plane electrodes, immersing the cooled initial PVDF film below the liquid level of the silicon oil, heating to the polarization temperature of 90 ℃, applying direct current high voltage to the two electrodes (the polarization time is 30min, and the polarization electric field is 70 mV/m), keeping the direct current high voltage for 40min, then keeping the electric field at the condition of 90MV/m, reducing the temperature of the silicon oil to the normal temperature, then removing the electric field, and finishing the polarization. During magnetron sputtering, two mask plates are needed to place the polarized film in the middle, and the mask plates are placed on a magnetron sputtering sample table. Sputtering growth vacuum degree of 10-3Pa, gas pressure of 3Pa, sputtering power of 70W, and growth time of 3min (Pt) and 5min (Au).
And coating a proper amount of conductive silver adhesive on the surface of the piezoelectric film for bonding, and curing at normal temperature. And (3) attaching the poly-p-phthalic Plastic (PET) and the piezoelectric film by using epoxy resin glue, and coating the outermost layer with rubber to obtain the piezoelectric sensor. The static piezoelectric coefficient d33 reaches 17.9 PC/N.
The invention simulates data collection when the piezoelectric sensor is applied to a track for crane walking, and the data collection is shown in table 1:
table 1 data collected by the piezoelectric sensor of example 1 in the crane running track
Serial number
stress/MPa
PVDF maximum Charge/. mu.C
1
13.32
0.05172
2
17.47
0.07782
3
24.89
0.11175
4
32.93
0.14282
5
39.72
0.18938
6
43.15
0.21436
As can be seen from table 1: along with the increase of stress, electric charge can increase, and this sensor device is early warning device, and the contact stress that takes place increases when gnawing the rail, can make the electric current rise, has the risk of gnawing the rail promptly.
Example 2
Mixing and dissolving 10g of polyvinylidene fluoride (PVDF) powder and 100ml of N-methylpyrrolidone (NMP), magnetically stirring for 60min at 70 ℃, standing for 40min under vacuum to remove bubbles, pouring into a casting dish, placing in a drying box, volatilizing the NMP by heating and evaporating, wherein the film forming temperature is 120 ℃, and the drying time is 60min, namely, a PVDF initial film is formed on the casting dish. And (3) placing the prepared PVDF initial film into a stretching machine, keeping the stretching temperature at 90 ℃ by using a temperature control machine, setting the stretching speed for stretching after the temperature is constant, setting the stretching ratio R to be 4 and the stretching speed to be 20mm/min, and stopping stretching after the specified stretching ratio is reached. Adjusting a temperature control machine to a proper temperature, preserving heat for a certain time, preserving heat for 20min at 90 ℃, and cooling under the condition of keeping tension;
and (3) clamping the cooled initial PVDF film between a pair of plane electrodes, immersing the cooled initial PVDF film below the liquid level of the silicon oil, heating to the polarization temperature of 90 ℃, applying direct current high voltage to the two electrodes (the polarization time is 30min, and the polarization electric field is 70 mV/m), keeping the direct current high voltage for 40min, then keeping the electric field at the condition of 90MV/m, reducing the temperature of the silicon oil to the normal temperature, then removing the electric field, and finishing the polarization. During magnetron sputtering, two mask plates are needed to place the polarized film in the middle, and the mask plates are placed on a magnetron sputtering sample table. Sputtering growth vacuum degree of 10-3Pa, gas pressure of 3Pa, sputtering power of 70W, and growth time of 3min (Pt) and 5min (Au).
And coating a proper amount of conductive silver adhesive on the surface of the piezoelectric film for bonding, and curing at normal temperature. And (3) attaching the poly-p-phthalic Plastic (PET) and the piezoelectric film by using epoxy resin glue, and coating the outermost layer with rubber to obtain the piezoelectric sensor. The static piezoelectric coefficient d33 reaches 18.5 PC/N.
The invention simulates data collection when the piezoelectric sensor is applied to a track for crane walking, and the data collection is shown in table 2:
table 2 data collected by the piezoelectric sensor of example 2 in a track on which a crane travels
Serial number
stress/MPa
PVDF maximum Charge/. mu.C
1
13.45
0.0646
2
17.45
0.0973
3
24.94
0.1397
4
32.82
0.1786
5
39.56
0.2367
6
43.14
0.2679
As can be seen from table 2: along with the increase of stress, the charge can be increased, the sensor device is an early warning device, the contact stress is increased when the rail is gnawed, the current can be increased, and the risk of gnawing the rail is realized
Example 3
Mixing and dissolving 10g of polyvinylidene fluoride (PVDF) powder and 100ml of N-methylpyrrolidone (NMP), magnetically stirring for 60min at 70 ℃, standing for 40min under vacuum to remove bubbles, pouring into a casting dish, placing in a drying box, volatilizing the NMP by heating and evaporating, wherein the film forming temperature is 120 ℃, and the drying time is 60min, namely, a PVDF initial film is formed on the casting dish. And (3) placing the prepared PVDF initial film into a stretching machine, keeping the stretching temperature at 90 ℃ by using a temperature control machine, setting the stretching speed for stretching after the temperature is constant, setting the stretching ratio R to be 4 and the stretching speed to be 20mm/min, and stopping stretching after the specified stretching ratio is reached. Adjusting a temperature control machine to a proper temperature, preserving heat for a certain time, preserving heat for 20min at 90 ℃, and cooling under the condition of keeping tension;
and (3) clamping the cooled initial PVDF film between a pair of plane electrodes, immersing the cooled initial PVDF film below the liquid level of the silicon oil, heating to the polarization temperature of 90 ℃, applying direct current high voltage to the two electrodes (the polarization time is 40min, and the polarization electric field is 80 mV/m), keeping the direct current high voltage for 40min, reducing the temperature of the silicon oil to the normal temperature under the condition of keeping the electric field at 90MV/m, and then removing the electric field to finish polarization. During magnetron sputtering, two mask plates are needed to place the polarized film in the middle, and the mask plates are placed on a magnetron sputtering sample table. Sputtering growth vacuum degree of 10-3Pa, gas pressure of 3Pa, sputtering power of 70W, and growth time of 1min (Pt) and 9min (Au).
And coating a proper amount of conductive silver adhesive on the surface of the piezoelectric film for bonding, and curing at normal temperature. And (3) attaching the poly-p-phthalic Plastic (PET) and the piezoelectric film by using epoxy resin glue, and coating the outermost layer with rubber to obtain the piezoelectric sensor. The static piezoelectric coefficient d33 reaches 19.8 PC/N.
The invention simulates the data collection when the piezoelectric sensor is applied to the track of the crane, as shown in table 3:
table 3 data collected by the piezoelectric sensor of example 3 in a track on which a crane travels
Serial number
stress/MPa
PVDF maximum Charge/. mu.C
1
13.56
0.0713
2
17.45
0.1023
3
24.65
0.1445
4
32.98
0.1907
5
39.45
0.2598
6
43.54
0.2906
As can be seen from table 3: along with the increase of stress, electric charge can increase, and this sensor device is early warning device, and the contact stress that takes place increases when gnawing the rail, can make the electric current rise, has the risk of gnawing the rail promptly.
The embodiments can show that the invention provides a preparation method of a PVDF piezoelectric induction film, which comprises the following steps of stretching a PVDF initial film, preserving heat, polarizing after cooling, and performing magnetron sputtering after cooling to obtain the PVDF piezoelectric induction film; the content of a piezoelectric phase in the PVDF piezoelectric film is 70-75%. According to the invention, the PVDF film is modified by a stretching method, phase change in the film is induced, and a piezoelectric beta phase is generated, and compared with an initial film, the piezoelectric phase content is increased by 3.5-4 times. The PVDF piezoelectric induction film has a larger static piezoelectric coefficient. The piezoelectric sensor prepared by the film can be used for rail gnawing prevention monitoring of a crane.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.