CN114889269B

CN114889269B - Ultrathin conductive foam and preparation method thereof

Info

Publication number: CN114889269B
Application number: CN202210460536.6A
Authority: CN
Inventors: 张文; 蒋顺江
Original assignee: Shenzhen Jintian Electron Co ltd
Current assignee: Shenzhen Jintian Electron Co ltd
Priority date: 2022-04-28
Filing date: 2022-04-28
Publication date: 2024-03-15
Anticipated expiration: 2042-04-28
Also published as: CN114889269A

Abstract

The application relates to the field of foam, and particularly discloses ultrathin conductive foam and a preparation method thereof. The ultrathin conductive foam comprises a conductive film and a foam body, wherein the conductive film is adhered to the surface of the foam body, and the conductive film is prepared from the following raw materials: polymethyl methacrylate, polybutylene terephthalate fiber, cross-linking agent, graphene powder, silicon dioxide, polyvinyl alcohol and formaldehyde, wherein the foam body is prepared from the following raw materials: 107 silicone rubber, vinyl silicone oil, antimony trioxide, aluminum hydroxide and methyl silicone oil; the preparation method comprises the following steps: and (3) utilizing supercritical carbon dioxide to act on the film to obtain a foaming film, soaking the foaming film in a soaking solution to obtain a conductive film, and adhering the conductive film on the surface of the prepared foam body to obtain the ultrathin conductive foam. The method and the device are effectively applicable to miniaturized and thinned electronic equipment.

Description

Ultrathin conductive foam and preparation method thereof

Technical Field

The application relates to the field of foam, in particular to ultrathin conductive foam and a preparation method thereof.

Background

The foam is foamed material of plastic particles, and has the characteristics of elasticity, light weight, quick pressure-sensitive fixation, convenient use, free bending and the like.

The conductive foam is flame-retardant foam with conductive cloth wrapped on the outer surface, has good surface conductivity, and is not separated from electronic equipment serving as a carrier for data transmission and data processing, and the conductive sponge is used for filling gaps between an external space and an internal circuit space communicated between motor equipment and the electronic equipment or is used for electric connection between a metal shell or a metal cover of electronic components in the electronic equipment and a reference ground so as to avoid electromagnetic interference between the electronic components and other electronic components in the electronic equipment.

However, in recent years, as electronic devices are gradually miniaturized and thinned, the width of a gap for installing conductive foam in the electronic device is smaller and smaller, and the applicability of the conventional conductive foam in the miniaturized and thinned electronic devices is poor, and when the thickness of the conductive foam is too thin, a breakage phenomenon is likely to occur.

Disclosure of Invention

The application provides an ultrathin conductive foam and a preparation method thereof, which can be effectively applied to miniaturized and thinned electronic equipment.

In a first aspect, the present application provides an ultrathin conductive foam, which adopts the following technical scheme:

the ultrathin conductive foam comprises a conductive film and a foam body, wherein the conductive film is adhered to the surface of the foam body, and the conductive film is prepared from the following raw materials in parts by weight: polymethyl methacrylate: 5-10 parts; polybutylene terephthalate fiber: 2-5 parts; crosslinking agent: 1-2 parts; graphene powder: 1-2 parts; silica: 1-2 parts; polyvinyl alcohol: 2-5; formaldehyde: 3-5, the foam body is prepared from the following raw materials in parts by weight: 107 silicone rubber: 20-25 parts of a lubricant; vinyl silicone oil: 6-8 parts of a lubricant; antimony trioxide: 3-5 parts; aluminum hydroxide: 2-4 parts; methyl silicone oil: 10-15 parts.

Through adopting above-mentioned technical scheme, polybutylene terephthalate combines with polymethyl methacrylate under the effect of cross-linking agent, polybutylene terephthalate's short fiber structure provides stable binding site for graphene powder and silicon dioxide, make graphene powder and silicon dioxide firmly and fully disperse in polymethyl methacrylate under the effect of cross-linking agent, the viscose liquid that polyvinyl alcohol and formaldehyde addition produced permeates in the porous structure that polybutylene terephthalate's short fiber supported, thereby make the conducting film have the conducting property, still possess better stickness, the porous structure that polybutylene terephthalate's short fiber supported makes the conducting film have better toughness and resilience, make the conducting film be difficult for taking place to break down the phenomenon, in addition, compared with traditional conductive foam using the adhesive tape bonding between foam and the conducting film, the conducting film that this application made can direct bonding with the lateral surface of foam on, thereby effectively reduce the volume of conductive foam, effectively be applicable to miniaturized and slim electronic equipment.

Optionally, the cross-linking agent is one or more of boric acid, sodium sulfate and zinc sulfate.

More preferably, the cross-linking agent is boric acid.

By adopting the technical scheme, the boric acid can effectively improve the combination of the polybutylene terephthalate and the polymethyl methacrylate on one hand and the tensile strength of the prepared conductive film on the other hand, so that the toughness of the conductive film is improved, and the fracture phenomenon of the conductive film in the bending process is reduced.

Optionally, the raw materials of the conductive film further comprise 3-5 parts by weight of polypyrrole.

By adopting the technical scheme, polypyrrole is mixed in the addition reaction process of polyvinyl alcohol and formaldehyde, so that the conductivity of the conductive film can be effectively improved.

Optionally, the foam body also comprises 2-3 parts by weight of melamine.

By adopting the technical scheme, the melamine can be doped to effectively improve the higher temperature resistance and flame retardant effect of the prepared foam, effectively inhibit the fire disaster phenomenon generated when the circuit is short-circuited and reduce the spread of fire.

Optionally, the particle size of the graphene powder is 3-6 μm.

Through the adoption of the technical scheme, when the particle size of the graphene is too large, the graphene agglomerates cannot be sufficiently and uniformly dispersed, meanwhile, the brittleness of the conductive film is increased due to the graphene agglomerates, the bending phenomenon is more likely to occur, and the conductive performance of the conductive film is affected; when the particle size of the graphene is too small, the short fiber structure of the polybutylene terephthalate is not good for capturing the graphene particles, so that the graphene cannot be effectively and uniformly dispersed in the conductive film.

Optionally, the silica has a particle size of 2-3 μm.

Through adopting above-mentioned technical scheme, when the particle diameter of silica is too big, can lead to the toughness of conducting film to reduce, the brittleness increases for the conducting film can not effectively stretch, appears buckling phenomenon easily, when the particle diameter of silica is too little, then can increase the surface area that the silica disperses to occupy, reduces the resilience of conducting film equally.

In a second aspect, the present application provides a method for preparing an ultrathin conductive foam, which adopts the following technical scheme:

the preparation method of the ultrathin conductive foam comprises the following steps of:

preparation of conductive film:

a1, mixing polymethyl methacrylate, polybutylene terephthalate fiber, a cross-linking agent, graphene powder and silicon dioxide in proportion, blending at 150-155 ℃, cooling to obtain a polymer, and stretching the polymer into a film;

a2, utilizing supercritical carbon dioxide to act on the film prepared in the A1, so as to obtain a foaming film with a plurality of micropores;

a3, mixing polyvinyl alcohol and formaldehyde at the temperature of 80-85 ℃ and the pH value of 3-5 to obtain a soaking solution;

a4, soaking the foaming film prepared in the step A2 in the soaking liquid prepared in the step A3 to obtain a conductive film;

preparation of foam: mixing 107 silicon rubber, vinyl silicone oil, antimony trioxide, sodium hydroxide, methyl silicone oil and a platinum catalyst together, and then placing the fully mixed materials in a drying device at 120-125 ℃ for 5-10min to obtain a foam body;

cutting: cutting the prepared foam body into a required shape;

sticking: and adhering the conductive film to the outer surface of the foam body to obtain the ultrathin conductive foam.

By adopting the technical scheme, supercritical carbon dioxide diffuses in the membrane, thereby causing a homogeneous system to generate phase separation and induce cell nucleation, leading the surface of the conductive membrane to generate a plurality of micropore structures, limiting the micropore expansion size by silicon dioxide, leading the micropore aperture of the conductive membrane to be thin and distributed densely, further improving the toughness of the conductive membrane, effectively reducing the bending and breakage phenomenon of the conductive membrane, simultaneously, the micropore structure is beneficial to the subsequent soaking liquid to permeate the conductive membrane and be effectively adsorbed on the conductive membrane, thereby enhancing the cohesiveness of the conductive membrane to foam bodies.

Optionally, polypyrrole is also added in the preparation process of the soaking liquid, and the weight part is 3-5.

Through adopting above-mentioned technical scheme, add polypyrrole in the soak for the soak is in the in-process of arranging the conductive film, and the polypyrrole is in the fibrous skeleton gap and the micropore of conductive film along with the soak infiltration, makes the conductive channel of conductive film have the wholeness more, effectively improves the conductive performance of conductive film with the cooperation graphite alkene, simultaneously, the knot of polypyrrole and fibrous skeleton makes the toughness of conductive film further increase.

Optionally, melamine is added in the preparation process of the foam body, and the weight part is 2-3.

In summary, the present application has the following beneficial effects:

1. the conductive film prepared by the method can be directly bonded on the outer side face of the foam body, so that the volume of the conductive foam body is effectively reduced, meanwhile, the conductive film has good flexibility due to the porous structure supported by the short fibers of the polybutylene terephthalate, the anti-breakage effect is good, and the conductive film is effectively applicable to miniaturized and thinned electronic equipment.

2. Boric acid can effectively improve the combination of polybutylene terephthalate and polymethyl methacrylate on one hand and the tensile strength of the prepared conductive film on the other hand, so that the toughness of the conductive film is improved; polypyrrole is mixed in the addition reaction process of polyvinyl alcohol and formaldehyde, so that the conductivity of the conductive film can be effectively improved; the supercritical carbon dioxide diffuses in the film, so that a plurality of micropore structures are generated on the surface of the conductive film, the toughness of the conductive film is further improved, the bending damage phenomenon of the conductive film is effectively reduced, meanwhile, the micropore structures are beneficial to the subsequent soaking liquid to permeate into the conductive film and are effectively adsorbed on the conductive film, and the cohesiveness of the conductive film to the foam body is enhanced.

Drawings

Fig. 1 is a cross-sectional view of an ultra-thin conductive foam of the present application.

1. A foam body; 2. a conductive film.

Detailed Description

The present application is described in further detail below with reference to fig. 1 and examples.

Polymethyl methacrylate was purchased from kewan engineering plastics materials limited, guan, korea LG PMMAHI535; polybutylene terephthalate was selected from PBT DURANEX 2002, available from Dongguan-heart-free plastic materials, inc.;

polyvinyl alcohol is selected from the company of Zongfang standard cellulose limited;

107 silicone rubber was selected from atanan silicon harbor chemical company;

polypyrrole is selected from Hubei Yunzhen technology Co., ltd.30604-81-0.

Examples

Example 1

Preparation of conductive film:

5kg of polymethyl methacrylate, 2kg of polybutylene terephthalate fiber, 1kg of sodium sulfate, 1kg of graphene powder and 1kg of silicon dioxide are put into a curing furnace, and are mixed for 1h at the temperature of 150 ℃, a polymer is obtained after cooling, the polymer is poured out of the curing furnace, and the polymer is placed into a drawing mill to be drawn, so that a film is obtained, wherein the average particle size of the graphene powder is 5 mu m, and the average particle size of the silicon dioxide is 2 mu m;

placing the prepared film into an autoclave, injecting carbon dioxide into the autoclave to ensure that the pressure in the autoclave is 7.38MPa, and placing the autoclave into a constant-temperature water tank with the temperature of 31.1 ℃ for standing for 10min to obtain a foaming film;

2kg of polyvinyl alcohol and 3kg of formaldehyde are mixed at the temperature of 80 ℃ and the pH value of 5 for 10min to obtain a soaking solution, ultrasonic equipment is opened to introduce ultrasonic waves with the frequency of 120KHz into the soaking solution, and the foaming film is soaked in the soaking solution and stands for 15min to obtain the conductive film.

Preparation of foam:

20kg of 107 silicone rubber, 6kg of vinyl silicone oil, 3kg of antimony trioxide, 2kg of sodium hydroxide, 10kg of methyl silicone oil, 2kg of melamine and 1kg of platinum catalyst were mixed together, and then the well-mixed materials were placed in a drying apparatus at 120℃for 5 minutes, thereby obtaining a foam body.

Cutting the conductive film and the foam body into a required shape by a cutting machine, wherein the thickness of the foam body is 0.05mm, the thickness of the conductive film is 0.01mm, and then adhering the conductive film on the outer surface of the foam body, thereby preparing the ultrathin conductive foam.

Example 2

Preparation of conductive film:

8kg of polymethyl methacrylate, 4kg of polybutylene terephthalate fiber, 1.5kg of sodium sulfate, 1.5kg of graphene powder and 1.5kg of silicon dioxide are put into a curing furnace, and are blended for 1h at 153 ℃, a polymer is obtained after cooling, the polymer is poured out of the curing furnace and is placed into a drawing mill to be drawn, and a film is obtained, wherein the average particle size of the graphene powder is 5 mu m, and the average particle size of the silicon dioxide is 2 mu m;

4kg of polyvinyl alcohol and 4kg of formaldehyde are mixed at 83 ℃ and pH value of 4 for 10min to obtain a soaking solution, ultrasonic equipment is opened to introduce ultrasonic waves with the frequency of 120KHz into the soaking solution, and the foaming film is soaked in the soaking solution and kept stand for 15min to obtain the conductive film.

Preparation of foam:

23kg of 107 silicone rubber, 7kg of vinyl silicone oil, 4kg of antimony trioxide, 3kg of sodium hydroxide, 13kg of methyl silicone oil, 2.5kg of melamine and 1kg of platinum catalyst were mixed together, and then the well-mixed material was placed in a drying apparatus at 123℃for 8 minutes, thereby obtaining a foam body.

Example 3

Preparation of conductive film:

10kg of polymethyl methacrylate, 5kg of polybutylene terephthalate fiber, 2kg of zinc sulfate, 2kg of graphene powder and 2kg of silicon dioxide are put into a curing furnace, and are mixed for 1h at 155 ℃, a polymer is obtained after cooling, the polymer is poured out of the curing furnace, and the polymer is placed into a drawing mill to be drawn, so that a film is obtained, wherein the average particle size of the graphene powder is 5 mu m, and the average particle size of the silicon dioxide is 2 mu m;

5kg of polyvinyl alcohol and 5kg of formaldehyde are mixed at the temperature of 85 ℃ and the pH value of 3 for 10min to obtain a soaking solution, ultrasonic equipment is opened to introduce ultrasonic waves with the frequency of 120KHz into the soaking solution, and the foaming film is soaked in the soaking solution and stands for 15min to obtain the conductive film.

Preparation of foam:

25kg of 107 silicone rubber, 8kg of vinyl silicone oil, 5kg of antimony trioxide, 4kg of sodium hydroxide, 15kg of methyl silicone oil, 3kg of melamine and 1kg of platinum catalyst were mixed together, and then the well-mixed material was placed in a drying apparatus at 125℃for 10 minutes, thereby obtaining a foam body.

Example 4

This example differs from example 2 only in that the sodium sulfate in this example is changed to boric acid.

Example 5

This example differs from example 2 only in that 4kg of polypyrrole was also added to the preparation of the soaking solution in this example.

Example 6

The present example differs from example 2 only in that the average particle diameter of the graphene powder in the present comparative example is 10 μm.

Example 7

The difference between this example and example 2 is only that the average particle diameter of the silica in this comparative example is 10. Mu.m.

Comparative example

Comparative example 1

The comparative example differs from example 2 only in that no supercritical carbon dioxide was used to act on the membrane in the comparative example.

Comparative example 2

The comparative example differs from example 2 only in that no silica was added to the comparative example.

Comparative example 3

The comparative example differs from example 2 only in that polybutylene terephthalate was not added thereto.

Comparative example 4

The comparative example differs from example 2 only in that polybutylene terephthalate and silica were not added thereto, nor was supercritical carbon dioxide used to act on the membrane.

Performance test

The following performance tests were conducted for examples 1 to 7 and comparative examples 1 to 4, and the results of the tests are shown in Table 1:

TABLE 1

As can be seen from the comparison of the data of examples 1-3 and example 4 in Table 1, when the cross-linking agent boric acid is substituted for sodium sulfate, the vertical resistance of the conductive foam is reduced, and at the same time, the shielding effectiveness is improved, the rebound rate and the tensile strength are both obviously improved, and boric acid can effectively improve the combination of polybutylene terephthalate and polymethyl methacrylate on the one hand and the tensile strength of the prepared conductive film on the other hand, so that the toughness of the conductive film is improved, and the fracture phenomenon of the conductive film in the bending process is reduced.

According to the comparison of the data of examples 1-3 and example 5 in table 1, when polypyrrole is added in the preparation of the soaking solution, the vertical resistance of the conductive foam is obviously reduced, and meanwhile, the shielding effectiveness is improved, and the polypyrrole permeates into the gaps and micropores of the fiber skeleton of the conductive film along with the soaking solution, so that the conductive channel of the conductive film has more integrity, and the conductive performance of the conductive film is effectively improved by matching with graphene.

As can be seen from the comparison of the data of example 2 and example 6 in table 1, when the average particle size of the graphene powder is 10 μm, the vertical resistance of the conductive foam is significantly increased, and when the particle size of the graphene is too large, the graphene agglomerates cannot be sufficiently and uniformly dispersed, and at the same time, the agglomerated graphene increases the brittleness of the conductive film, and the bending phenomenon is more likely to occur, and in addition, the conductive performance of the conductive film is also affected.

As can be seen from the comparison of the data of examples 2 and 7 and comparative examples 1 to 2 in Table 1, when the average particle diameter of the silica is 10. Mu.m, the vertical resistance of the conductive foam is significantly improved, the rebound rate and tensile strength are both reduced, and when the particle diameter of the silica is too large, the toughness of the conductive film is reduced, the brittleness is increased, so that the conductive film cannot be effectively stretched, and the bending phenomenon is easy to occur; when no silica is added, when supercritical carbon dioxide acts on the membrane, the pore diameter of the prepared foaming film is too large, so that the toughness of the membrane is reduced; when the supercritical carbon dioxide is not used for acting on the film, the vertical resistance of the conductive foam is obviously improved, and the rebound rate and the tensile strength are reduced.

As can be seen from the comparison of the data of examples 2 and 3 in table 1, when polybutylene terephthalate is not added into the conductive film, the vertical resistance of the conductive foam is significantly improved, both the rebound resilience and the tensile strength are reduced, the conductive film loses the short fiber skeleton structure, so that the conductive film cannot effectively capture graphene powder and silicon dioxide, the graphene powder and the silicon dioxide cannot effectively and uniformly disperse in the conductive film, the conductive performance and the shielding effectiveness of the conductive film are weakened, the adhesive solution generated by adding polyvinyl alcohol and formaldehyde cannot effectively be arranged on the conductive film, the conductive performance of the conductive film is further weakened, and the conductive film is not ideal in the subsequent foaming process due to the loss of the elastic skeleton, so that the rebound resilience and the tensile strength are further influenced.

The present embodiment is merely illustrative of the present application and is not intended to be limiting, and those skilled in the art, after having read the present specification, may make modifications to the present embodiment without creative contribution as required, but is protected by patent laws within the scope of the claims of the present application.

Claims

1. The ultrathin conductive foam is characterized by comprising a conductive film and a foam body, wherein the conductive film is adhered to the surface of the foam body, and is prepared from the following raw materials in parts by weight: polymethyl methacrylate: 5-10 parts; polybutylene terephthalate staple fiber: 2-5 parts; crosslinking agent: 1-2 parts; graphene powder: 1-2 parts; silica: 1-2 parts; polyvinyl alcohol: 2-5 parts; formaldehyde: 3-5 parts of foam body, wherein the foam body is prepared from the following raw materials in parts by weight: 107 silicone rubber: 20-25 parts of a lubricant; vinyl silicone oil: 6-8 parts of a lubricant; antimony trioxide: 3-5 parts; aluminum hydroxide: 2-4 parts; methyl silicone oil: 10-15 parts of a lubricant; wherein the particle size of the graphene powder is 3-6 mu m, and the particle size of the silicon dioxide is 2-3 mu m;

preparation of conductive film:

a1, mixing polymethyl methacrylate, polybutylene terephthalate short fiber, a cross-linking agent, graphene powder and silicon dioxide in proportion, blending at 150-155 ℃, cooling to obtain a polymer, and stretching the polymer into a film;

cutting: cutting the prepared foam body into a required shape;

2. The ultra-thin conductive foam of claim 1, wherein: the cross-linking agent is one or more of boric acid, sodium sulfate and zinc sulfate.

3. The ultra-thin conductive foam of claim 1, wherein: the raw materials of the conductive film also comprise 3-5 parts by weight of polypyrrole.

4. The ultra-thin conductive foam of claim 1, wherein: the foam body also comprises 2-3 parts by weight of melamine.

5. The ultra-thin conductive foam of claim 1, wherein: polypyrrole is also added in the preparation process of the soaking liquid, and the weight part is 3-5.

6. The ultra-thin conductive foam of claim 1, wherein: melamine is also added in the preparation process of the foam body, and the weight part is 2-3.