WO2023217065A1 - Preparation method for electrically and thermally stimulated shape memory fpc electromagnetic shielding film - Google Patents

Abstract

A preparation method for an electrically and thermally stimulated shape memory FPC electromagnetic shielding film, belonging to the technical field of polymer science. The method comprises: first preparing an EVA fiber film by means of electrostatic spinning and ultraviolet curing; after curing, dipping same into a dopamine solution; then placing into a Tollens' reagent the fiber film on the surface of which a polydopamine thin film is deposited; then adding a glucose solution for reaction; and after the reaction is finished, drying same to obtain the electrically and thermally stimulated shape memory FPC electromagnetic shielding film. The prepared FPC electromagnetic shielding film has ultrahigh conductivity, ultra-high EMI SE and an electrically/thermally stimulated shape memory effect. In aspect of comprehensive performance, the FPC electromagnetic shielding film under electrical stimulation can freely deform according to the dimension of an FPC and closely fit electronic components in a high-density layout, and meanwhile, still hold stable high EMI SE; and when a waste mobile phone is recycled, a shape memory polymer based conductive composite fiber film is driven by thermal stimulation to recover the shape and EMI SE, thus exhibiting relatively high recycling performance.

Description

A preparation method for electrothermal stimulation shape memory FPC electromagnetic shielding film Technical field

The invention relates to a preparation method of electrothermal stimulation shape memory FPC electromagnetic shielding film, and belongs to the field of polymer science and technology.

Background technique

At present, the size of my country's 3C digital product recycling market has exceeded 100 billion yuan. Some used mobile phones are seriously damaged and have lost their repair value. However, the parts in the mobile phones still need to be dismantled. They will be disassembled into motherboards, screens, and batteries. , camera, memory, etc. At this stage, my country's annual e-waste processing volume has reached about 80 million tons, but the standard recycling rate is less than 20%, while in Europe it has reached 42.5%, and in the category of mobile phones, the recycling rate has plummeted to 2% .

The low-cost recycling of scrapped mobile phones is an unsolved problem that affects the overall development of the industry. Improving the recyclability of mobile phone parts not only promotes the development of the recycling industry, but also avoids resource waste and environmental damage.

5G foldable mobile phones have ultra-high data transmission rates, large portable screens and expensive prices, and deserve to be the leader in smartphones. However, when it is in a complex electromagnetic environment, it will inevitably be subject to electromagnetic interference from electronic components on the internal and external flexible circuit boards (FPC), causing signal attenuation and incomplete signal transmission.

The emergence of electromagnetic shielding film provides a solution for electromagnetic shielding of FPC and has good application effects. The polymer-based conductive composite fiber membrane has outstanding advantages such as thinness, high flexibility, strong durability, high conductivity, high electromagnetic interference shielding efficiency and wide shielding band, and is expected to become a new generation of high-performance electromagnetic interference (EMI) shielding materials. For example, the flexible composite electromagnetic shielding film constructed of conductive nanofibers in the patent CN113265908 achieves the shielding of electromagnetic waves by the flexible self-supporting conductive nanofiber film. However, it requires subsequent processing to fit FPCs of various sizes, and when the mobile phone is scrapped When recycled, the shielding film will inevitably be scrapped.

When the existing FPC electromagnetic shielding film was designed, it only considered production and application, and did not consider the recycling process, such as easy disassembly and recycling, to achieve low-cost recycling of electronic waste.

Contents of the invention

In order to solve the above problems, the first object of the present invention is to provide a method for preparing an electrothermal stimulation shape memory FPC electromagnetic shielding film. The steps are:

(1) Electrospinning and UV curing to prepare ethylene-vinyl acetate copolymer (EVA) fiber membrane;

(2) Dip the EVA fiber membrane into a dopamine solution for reaction. After the reaction, remove excess polydopamine microspheres on the surface of the EVA fiber membrane to obtain an EVA fiber membrane with a polydopamine film deposited on the surface;

(3) The fiber membrane with the polydopamine film deposited on the surface is immersed in the silver ammonia solution, stirred, and the glucose solution is added dropwise to react. After the reaction is completed, it is washed and dried to obtain an FPC electromagnetic shielding film with electrothermal stimulation shape memory effect.

In one embodiment of the present invention, the electrospinning of step (1) prepares an EVA fiber membrane by mixing ethylene-vinyl acetate copolymer (EVA) particles, benzophenone (BP) powder and triallyl isocyanate Urea ester (TAIC) is mixed and dissolved in a mixed solvent of toluene and N,N-dimethylformamide (DMF) to obtain a uniform spinning liquid, and then the uniform spinning liquid is transferred to a syringe for electrostatic spinning to prepare electrostatic Spun EVA fiber membrane.

In one embodiment of the present invention, the ultraviolet light curing in step (1) is to place the electrospun EVA fiber membrane under 365nm ultraviolet light for 1 hour.

In one embodiment of the present invention, the mass ratio of EVA particles, BP powder and TAIC in the electrospinning solution of step (1) is 100:2-5:1-3, and the preferred mass ratio is 100: 3:1.

In one embodiment of the present invention, the VA of the EVA particles accounts for 20wt% to 30wt%, and preferably the VA of the EVA particles accounts for 25wt%.

In one embodiment of the present invention, the volume ratio of toluene and DMF in the electrospinning spinning solution of step (1) is 2 to 3:1, and the preferred volume ratio is 7:3.

In one embodiment of the present invention, the mass concentration of EVA in the electrospinning solution of step (1) is 8wt%~15wt%, and the preferred mass concentration of EVA in the spinning solution is 10wt%~12wt%. The optimal mass concentration of EVA in the spinning solution is 10wt%.

In one embodiment of the present invention, the voltage of electrospinning in step (1) is 15-18kV, the preferred voltage is 16±0.5kV, and the optimal voltage is 16kV.

In one embodiment of the present invention, the specific steps of preparing EVA fiber membrane by electrospinning in step (1) are:

① Under magnetic stirring at 50°C, dissolve 5g of EVA particles, BP powder and TAIC in a mixed solvent of 50ml of toluene and DMF in a volume ratio of 7:3 at a mass ratio of 100:3:1 for 5h to obtain a uniformly spun silk liquid;

② Transfer 20ml of uniform spinning solution into a plastic syringe equipped with a heating jacket (temperature maintained at 50°C) and a metal needle, and connect the positive electrode of the high-voltage power supply to the metal needle;

③ Turn on the infrared lamp (the temperature is maintained at 50°C) and the collection drum 20cm away from the syringe pump and rotating at 100r/min, and connect the negative electrode of the high-voltage power supply to the collection drum;

④ Under the conditions of an ambient temperature of 30±2℃ and a relative humidity of 45±5%, turn on the syringe pump with a feed rate of 2ml/h and the high-voltage power supply with a voltage of 16kV. The electrospun EVA fiber membrane can be collected after 8 hours. ;

⑤After the electrospun EVA fiber membrane has been resting in a ventilated place for 24 hours, it is peeled off from the dense stainless steel mesh and placed in a UV curing machine for 1 hour;

⑥ Use ethanol solution for ultrasonic cleaning to remove surface impurities and obtain an EVA fiber membrane.

In one embodiment of the present invention, the dopamine solution in step (2) is a mixture of dopamine hydrochloride and trishydroxymethylcarbamate. Alkane (Tris) was mixed and dissolved in deionized water.

In one embodiment of the present invention, the dopamine solution in step (2) is prepared by dissolving dopamine hydrochloride in deionized water to form a dopamine solution, and adding Tris to adjust the pH to 8.5-9.5.

In one embodiment of the present invention, the dopamine concentration in the dopamine solution of step (2) is 2-5g/L, the preferred dopamine concentration is 2-3g/L, and the optimal dopamine concentration is 2g/L.

In one embodiment of the present invention, the time for the EVA fiber membrane to be immersed in the dopamine solution in step (2) is 20 to 25 hours.

In one embodiment of the present invention, in step (2), the reacted fiber membrane also needs to be moved to deionized water and ultrasonicated for 1 to 5 minutes.

In one embodiment of the present invention, the silver ammonia solution in step (3) is obtained by dissolving AgNO ₃ crystals in water to obtain an AgNO ₃ solution. Under continuous stirring, ammonia water is slowly dripped into the AgNO ₃ solution until the solution becomes clear. .

In one embodiment of the present invention, the AgNO ₃ solution concentration in step (3) is 9 to 11 g/L, and the preferred AgNO ₃ solution concentration is 9 to 10 g/L.

In one embodiment of the present invention, the silver ammonia solution in step (3) is specifically to dissolve 1gAgNO ₃ crystals in 100 ml of deionized water to obtain a homogeneous AgNO ₃ solution. Under continuous stirring, add AgNO ₃ with a concentration of 10g/L. Slowly drip ammonia solution with a concentration of 25% into the solution until the solution becomes clear.

In one embodiment of the present invention, the reaction temperature in step (3) is 30-50°C.

In one embodiment of the present invention, the stirring time in step (3) is 20 to 40 minutes, and the optimal stirring time is 30 minutes.

In one embodiment of the present invention, the concentration of the glucose solution in step (3) is 15-25g/L.

In one embodiment of the present invention, the concentration ratio of the AgNO ₃ solution and the glucose solution in step (3) is 1:1 to 2, and the volume ratio is 1:1.

In one embodiment of the present invention, the reaction of step (3) is to slowly drop the glucose solution into the silver ammonia solution, conduct it in an ultrasonic environment for 3 minutes, and then conduct it with magnetic stirring at 40°C for 2 hours.

The present invention uses the above method to prepare an electrical/thermal stimulation shape memory FPC electromagnetic shielding film.

The second object of the present invention is to apply the above-mentioned electrical/thermal stimulation shape memory FPC electromagnetic shielding film to the field of electronic equipment manufacturing.

Beneficial effects:

(1) In addition to being light, thin and highly flexible, the shape memory polymer fiber membrane prepared by electrospinning also has high porosity and large specific surface area, which can provide enough space for multiple reflections of incident electromagnetic waves and is flexible. Ideal matrix for EMI shielding materials;

(2) The chemical silver plating process can be used to firmly modify the dense and uniform silver layer on the surface of the polymer fiber, giving the composite fiber high electrical conductivity and strong EMI shielding ability;

(3) Under electrical stimulation, the FPC electromagnetic shielding film prepared by the present invention can not only deform freely according to the size of the FPC, but also can completely adhere to the densely arranged uneven or staggered electronic components on the FPC. At the same time, its Electromagnetic interference shielding effectiveness remains at a relatively high level;

(4) When electronic equipment is discarded and recycled, thermal stimulation of the fiber membrane can restore its shape and electromagnetic interference shielding effectiveness, making it highly recyclable.

Description of the drawings

Figure 1 is a schematic diagram of the preparation method of the FPC electromagnetic shielding film with electrical/thermal stimulation shape memory effect of the present invention.

Figure 2 shows the thermally induced shape memory effect of EVA fiber membrane.

Figure 3 shows the thermally induced shape memory effect of the FPC electromagnetic shielding film prepared in Example 1.

Figure 4 is the electromagnetic shape memory effect of the FPC electromagnetic shielding film prepared in Example 1. a is the shape fixation rate (R _f ) and shape recovery of the FPC electromagnetic shielding film prepared in Example 1 in the electric response stretching shape memory behavior. rate (R _r ); b is the electrical response stretching shape memory behavior of the FPC electromagnetic shielding film prepared in Example 1; c is the R _f and R in the electrical response pressing shape memory behavior of the FPC electromagnetic shielding film prepared in Example 1 _r ; d is the electrical response to pressing shape memory behavior of the FPC electromagnetic shielding film prepared in Example 1.

Figure 5 is the conductivity of the FPC electromagnetic shielding film prepared in Example 1 during the shape memory process.

Figure 6 shows the electromagnetic interference shielding effectiveness (EMI SE) of the FPC electromagnetic shielding film prepared in Example 1 during the shape memory process.

Figure 7 is a schematic diagram of the EMI shielding mechanism of FPC electromagnetic shielding film.

Figure 8 is a schematic diagram of the practical application of FPC electromagnetic shielding film. The original electrothermal stimulation shape memory FPC electromagnetic shielding film is stretched to the size of FPC at 0.55V. The stretched electrothermal stimulation shape memory FPC electromagnetic shielding film is stretched at 0.55V. The shape memory FPC electromagnetic shielding film is driven to return to its original shape at 80°C by the cooled electrothermal stimulus that is pressed to closely adhere to the densely laid out electronic components.

Detailed ways

The electrical/thermal stimulation shape memory process of FPC electromagnetic shielding film is as follows: (1) Test the conductivity and EMI SE of the initial FPC electromagnetic shielding film. (2) Apply a voltage of 0.55V to the initial sample, stretch the sample, turn off the power, and remove the external force. The deformed sample can be obtained and its conductivity and EMI SE can be tested. (3) Under stress-free conditions, apply a high temperature of 80°C to the deformed sample to obtain a recovered sample, and test its conductivity and EMI SE.

Conductivity: Measurement of electrothermal stimulation shape memory FPC electromagnetic shielding film using a four-probe resistometer.

EMI SE: Measurement of electrothermal stimulation shape memory FPC electromagnetic shielding film using vector network analyzer.

The EVA particles used in the following examples were purchased from Aladdin, with a VA content of 25wt% and a melt index of 19g/10min.

Example 1:

A method for preparing an FPC electromagnetic shielding film with electrothermal stimulation of shape memory effect. Figure 1 is a schematic diagram of the preparation method of the FPC electromagnetic shielding film of the present invention. The sequence of preparation process steps includes:

(1) Preparation of EVA fiber membrane by electrospinning and UV curing:

① Under magnetic stirring at 50°C, dissolve 5g EVA particles, 0.15g BP powder and 0.05g TAIC in a mixed solvent of 50ml toluene and DMF with a volume ratio of 7:3 for 5h to obtain a uniform spinning solution;

② Transfer 20ml of uniform spinning solution into a plastic syringe equipped with a heating jacket (temperature maintained at 50°C) and a metal needle, and connect the positive electrode of the high-voltage power supply to the metal needle;

③ Turn on the infrared lamp (the temperature is maintained at 50°C) and the collection drum 20cm away from the syringe pump and rotating at 100r/min, and connect the negative electrode of the high-voltage power supply to the collection drum;

④ Under the conditions of an ambient temperature of 30°C and a relative humidity of 50%, turn on the syringe pump with a feed rate of 2ml/h and the high-voltage power supply with a voltage of 16kV. The electrospun EVA fiber membrane can be collected after 8 hours;

⑤After the electrospun EVA fiber membrane has been resting in a ventilated place for 24 hours, it is peeled off from the dense stainless steel mesh and placed in a UV curing machine for 1 hour;

⑥ Use ethanol solution for ultrasonic cleaning to remove surface impurities and obtain an EVA fiber membrane.

(2) Dissolve dopamine hydrochloride in deionized water to form a dopamine solution with a concentration of 2g/L. Add Tris to adjust the pH to 8.5; immerse the cleaned EVA fiber membrane into the dopamine solution and continue stirring for 24 hours. The reacted EVA fiber membrane was transferred to deionized water and ultrasonicated for 5 minutes to obtain an EVA fiber membrane with a polydopamine film deposited on the surface;

(3) Dissolve _1gAgNO3 crystals in 100ml deionized water to obtain a homogeneous _AgNO3 solution; with continuous stirring, slowly drop ammonia water with a concentration of 25% into the _AgNO3 solution with a concentration of 10g/L until the solution becomes For clarification, prepare a silver ammonia solution; put the EVA fiber membrane with polydopamine film deposited on the surface into the silver ammonia solution and stir magnetically for 30 minutes; slowly drip 100ml glucose solution with a concentration of 20g/L into the EVA fiber membrane with polydopamine film deposited on the surface. In the silver ammonia solution of the EVA fiber membrane, conduct it in an ultrasonic environment for 3 minutes, and then magnetically stir it at 40°C for 2 hours. The reacted fiber membrane is washed in deionized water and dried at room temperature to obtain the electrothermal stimulation shape memory FPC. Electromagnetic shielding film.

The prepared electrothermal stimulation shape memory FPC electromagnetic shielding film has excellent shape memory effect, R _f is 99%, R _r is 97%, and electromagnetic shielding performance is also excellent, with EMI SE of 87.71dB.

Example 2:

Referring to Example 1, only the spinning voltage of ④ in step (1) was changed to 16kV, 17kV and 18kV, and the other conditions remained unchanged, to prepare an electrothermal stimulation shape memory FPC electromagnetic shielding film.

Table 1 Performance comparison table of electrothermal stimulation shape memory FPC electromagnetic shielding films prepared with different spinning voltages

Example 3:

Referring to Example 1, change the concentrations of the AgNO ₃ solution and glucose solution in step (3) according to Table 2, and keep the other conditions unchanged, to prepare an electrothermal stimulation shape memory FPC electromagnetic shielding film.

Table 2 Performance comparison table of electrothermal stimulation shape memory FPC electromagnetic shielding films prepared with different AgNO ₃ solutions and glucose solutions

Example 4

(1) Preparation of ethylene-vinyl acetate copolymer (EVA) fiber membrane by hot pressing method:

① Dissolve 5g EVA particles and 0.15g cumene peroxide (DCP) in 50ml toluene solvent to obtain a uniform EVA solution;

② Dry the mixed solution at room temperature first and then in a vacuum drying oven to fully remove toluene.

③Cut the dried base material into pieces and spread it evenly on the hot pressing mold, and cure at 140°C, 150°C, and 160°C for 3 hours.

④ Take out the cured EVA film from the hot pressing mold at 25℃.

(2) Dissolve the mixture of dopamine hydrochloride and Tris in deionized water to obtain a dopamine solution with a pH of 8.5 and a concentration of 2g/L; immerse the cleaned EVA fiber membrane in the dopamine solution and continue stirring for 24 hours. The EVA fiber membrane was transferred to deionized water and ultrasonicated for 5 minutes to obtain an EVA fiber membrane with a polydopamine film deposited on the surface;

(3) The fiber membrane with the polydopamine film deposited on the surface is immersed in the silver ammonia solution, stirred, and the glucose solution is added dropwise to react. After the reaction is completed, it is washed and dried to obtain an FPC electromagnetic shielding film with electrothermal stimulation shape memory effect. Dissolve _1gAgNO3 crystals in 100ml deionized water to obtain a homogeneous _AgNO3 solution; with continuous stirring, slowly drop ammonia water with a concentration of 25% into the _AgNO3 solution with a concentration of 10g/L until the solution becomes clear. Configure it into a silver ammonia solution; put the EVA fiber membrane with the polydopamine film deposited on the surface into the silver ammonia solution and stir magnetically for 30 minutes; slowly drop 100ml glucose solution with a concentration of 20g/L into the EVA fiber membrane soaked with the surface deposited polydopamine film. In the silver ammonia solution, perform 3 min in an ultrasonic environment, and then magnetically stir at 40°C for 2 h. The reacted fiber membrane is washed in deionized water and dried at room temperature to obtain the electrothermal stimulation shape memory FPC electromagnetic shielding film. .

Table 3 Performance comparison table of electrothermal stimulation shape memory FPC electromagnetic shielding films prepared using different hot pressing temperatures.

Example 5

Referring to Example 1, the ultraviolet curing in step (5) in step (1) is omitted, and the other conditions remain unchanged, to prepare an electrothermal stimulation shape memory FPC electromagnetic shielding film.

The electromagnetic shielding performance of the prepared electrothermal stimulation shape memory FPC electromagnetic shielding film was not affected, but the shape memory effect decreased, with R _f being 92% and R _r being 80%.

Although the present invention has been disclosed above with preferred examples, they are not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection of an invention shall be defined by the claims.

Claims (11)

1. A method for preparing an electrothermal stimulation shape memory FPC electromagnetic shielding film, which is characterized in that the steps are:

   (1) Preparation of EVA fiber membrane by electrospinning and UV curing;

   (2) The EVA fiber membrane is immersed in the dopamine solution and reacted. After the reaction is completed, an EVA fiber membrane with a polydopamine film deposited on the surface is obtained;

   (3) The fiber membrane with the polydopamine film deposited on the surface is immersed in the silver ammonia solution, stirred, and reacted with dropwise addition of glucose solution. After the reaction is completed, it is washed and dried to obtain an FPC electromagnetic shielding film with an electrothermal stimulation shape memory effect;

   The ultraviolet light curing in step (1) is to place the electrospun EVA fiber membrane under 365nm ultraviolet light for 1 hour;

   Step (3) The silver ammonia solution is made by dissolving AgNO ₃ crystals in water to obtain an AgNO ₃ solution. Under continuous stirring, slowly drop ammonia water into the AgNO ₃ solution until the solution becomes clear;

   The concentration of the AgNO ₃ solution in step (3) is 9-10g/L; the concentration ratio of the AgNO ₃ solution and the glucose solution in step (3) is 1:1, and the volume ratio is 1:1.
2. A method for preparing an electrothermal stimulation shape memory FPC electromagnetic shielding film, which is characterized in that the steps are:

   (1) Preparation of EVA fiber membrane by electrospinning and UV curing;

   (2) The EVA fiber membrane is immersed in the dopamine solution and reacted. After the reaction is completed, an EVA fiber membrane with a polydopamine film deposited on the surface is obtained;

   (3) The fiber membrane with the polydopamine film deposited on the surface is immersed in the silver ammonia solution, stirred, and reacted with glucose solution dropwise. After the reaction is completed, it is washed and dried to obtain an FPC electromagnetic shielding film with an electrothermal stimulation shape memory effect.
3. The method according to claim 2, characterized in that the electrospinning of step (1) is to mix and dissolve EVA particles, benzophenone powder and triallyl isocyanurate in toluene and N,N-bis In the mixed solvent of methylformamide, a uniform spinning liquid is obtained, and then the uniform spinning liquid is transferred to a syringe to prepare an electrospun EVA fiber membrane through electrospinning.
4. The method according to claim 2, characterized in that the ultraviolet light curing in step (1) is to place the electrospun EVA fiber membrane under 365nm ultraviolet light for 1 hour.
5. The method according to claim 3, characterized in that the mass ratio of EVA particles, BP powder and TAIC in the electrospinning spinning liquid of step (1) is 100:2~5:1~3.
6. The method according to any one of claims 3, characterized in that the volume ratio of toluene and DMF in the electrospinning spinning liquid of step (1) is 2 to 3:1.
7. The method according to claim 2, characterized in that the voltage of electrospinning in step (1) is 15-18kV.
8. The method according to claim 2, characterized in that the concentration of dopamine in the dopamine solution of step (2) is 2-5g/L.
9. The method according to any one of claims 2 to 8, characterized in that, after the reaction in step (2), the fiber membrane is moved to deionized water and ultrasonicated for 1 to 5 minutes.
10. An electrothermal stimulation shape memory FPC electromagnetic shielding film prepared by the method of any one of claims 2 to 9.
11. The application of the electrothermal stimulation shape memory FPC electromagnetic shielding film described in claim 10 in the field of electronic equipment manufacturing.