TWI738329B - Conductive ink and conductive element with tensile property - Google Patents

Abstract

A conductive ink with tensile property, including a flexible resin and plastic particles and a conductive agent mixed in the flexible resin. The conductive agent includes at least one conductive carbon material selected from a group consisting of conductive carbon black and carbon nanotubes. A mass ratio of the conductive carbon material in the conductive ink is from 20% to 40%. The present application also provides a conductive element made of the conductive ink.

Description

Conductive ink and conductive element with tensile properties

This application relates to the field of stretchable materials, and in particular to a conductive ink with stretchability and a conductive element prepared from the above-mentioned conductive ink.

In recent years, with the development of artificial skin, robotic arms, smart wearable clothing and other fields, stretchable materials have attracted more and more attention. The preparation of existing stretchable materials is mainly based on engineering structure design. For example, if stretchable metal conductive materials need to be prepared, the metal lines can be designed in a horseshoe shape, or the metal lines can be woven to form a metal grid to make The metal conductive material that does not originally have stretchability gains stretchability.

However, the stretchable material produced by this method will increase its resistance sharply after being stretched many times, and it can only stretch in a single direction. Moreover, the engineering structure design process is complicated, the cost is high, and it is difficult to realize mass production.

In view of this, it is necessary to provide a stretchable material that can be stretched in multiple directions, the resistance value does not rise sharply after being stretched, and is easy to produce.

The present application provides a conductive ink with tensile properties, which includes a flexible resin, plastic particles and a conductive agent mixed in the flexible resin, and the conductive agent includes at least one conductive carbon material among conductive carbon black and carbon nanotubes, The mass ratio of the conductive carbon material in the conductive ink is 20%-40%.

In some embodiments of the present application, the material of the plastic particles includes but is not limited to at least one of polyvinyl chloride, polymethyl methacrylate, polyethylene, and nylon.

In some embodiments of the present application, the conductive agent further includes metal powder, and the mass ratio of the conductive carbon material and the metal powder is greater than 2:1.

In some embodiments of the present application, the mass ratio of the flexible resin in the conductive ink is 60%-80%.

In some embodiments of the present application, the flexible resin includes but is not limited to at least one of rubber-based resin and polyurethane-based resin.

The conductive ink further includes a solvent including but not limited to at least one of toluene, high flash point aromatic naphtha and ethylene glycol butyl ether. In some embodiments of the present application, the rubber includes at least one of styrene-ethylene-butylene-styrene block copolymer rubber and styrene-butadiene-styrene block copolymer rubber, and the polyurethane It is water-based polyurethane or oil-based polyurethane.

In some embodiments of the present application, the flexible resin includes a two-component polyurethane, and the two-component polyurethane includes a polyol and a diisocyanate.

In some embodiments of the application, the density of the two-component polyurethane is less than 30 m ³ /kg.

In some embodiments of the present application, the flexible resin includes at least one of a thermoplastic resin or a thermosetting resin, and the conductive ink further includes a foaming agent.

The application also provides a conductive element, which is made of the conductive ink described above.

Compared with the engineering structure design in the prior art, this application adds plastic particles in the flexible resin, so that the conductive ink has alternately arranged flexible structure (ie, flexible resin) and hard structure (ie, flexible resin) along any direction. , Plastic particles), which not only facilitates the simplification of the manufacturing process and reduces the cost, but also the conductive element prepared according to the conductive ink has stretchability and flexibility in multiple directions. Moreover, the plastic particles can increase the tensile recovery rate of the conductive element. In addition, when the conductive carbon material is used as the conductive agent, compared with the traditional metal particle conductive agent, the present application can make the resistance value change rate of the conductive element after stretching smaller.

This application provides a conductive ink with stretching properties. The conductive ink includes a flexible resin, plastic particles and a conductive agent mixed in the flexible resin. The conductive agent includes at least one conductive carbon material among conductive carbon black and carbon nanotubes. Wherein, the mass ratio of the conductive carbon material in the conductive ink is 20%-40%.

Compared with the engineering structure design in the prior art, this application adds plastic particles to the flexible resin so that the conductive ink has alternately arranged flexible structures (ie, flexible resins) and hard structures (ie, flexible resins) along any direction. , Plastic particles), which not only facilitates the simplification of the manufacturing process and reduces the cost, but also the conductive element prepared according to the conductive ink has stretchability and flexibility in multiple directions. Moreover, the plastic particles can increase the tensile recovery rate of the conductive element (up to 98.5%). Furthermore, by changing the mass proportion of the plastic particles in the conductive ink, the stretch rate of the conductive element can be changed within a certain range to meet specific requirements. Wherein, the stretch rate is defined as the ratio between the current length L of the stretched material and the initial size L _0.

In addition, when the conductive carbon material is used as the conductive agent, compared with the traditional metal particle conductive agent, the application can make the resistance value change rate of the conductive element after stretching smaller (less than 10%). Wherein, the resistivity change value is defined as the ratio of the difference (RR ₀ ) between the current resistance value and the initial resistance value of the stretched material to the initial resistance value R ₀ .

Wherein, the flexible resin is a soft and bendable resin after curing. In some embodiments, the mass ratio of the flexible resin in the conductive ink is 60%-80%. When the mass proportion of the flexible resin is less than 60%, the conductive element prepared according to the conductive ink has insufficient stretchability; conversely, when the mass proportion of the flexible resin is greater than 80%, the conductive ink The proportion of the conductive agent or the mass of the plastic particles needs to be relatively reduced, which is not conducive to ensuring the conductivity of the conductive ink or the resistance change rate after stretching, and it is also not conducive to improving the tensile recovery rate of the conductive element.

In some embodiments, the material of the plastic particles includes but is not limited to at least one of polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polyethylene (PE), and nylon.

In some embodiments, the conductive agent may further include graphite, graphene and other conductive carbon materials and metal powders. The metal powder may be dendritic, such as dendritic silver and dendritic silver-coated copper. By adding metal powder, the conductivity of the conductive ink can be improved, but at the same time, the water washing resistance of the conductive ink will be reduced, and the resistance value change rate of the conductive ink after stretching will be improved. Therefore, the mass ratio of the conductive carbon material and the metal powder in this embodiment is greater than 2:1. Wherein, when the conductive agent includes conductive carbon material and metal powder at the same time, compared with the traditional metal particle conductive agent, the resistance value change rate of the conductive element after stretching can be made smaller, but compared with the conductive agent. The electrical resistance change rate of the conductive carbon material is large.

In one embodiment, the conductive ink may be a solvent-based conductive ink.

At this time, the flexible resin includes at least one of rubber-based resin and polyurethane-based resin. Among them, the rubber is preferably at least one of styrene-ethylene-butylene-styrene block copolymer (SEBS) rubber and styrene-butadiene-styrene block copolymer (SBS) rubber, which is advantageous further Improve the tensile recovery rate of the conductive element. The polyurethane may be water-based polyurethane or oil-based polyurethane.

The conductive ink further includes a solvent. The solvent can be a high-boiling solvent with a boiling point greater than 100 degrees Celsius, such as toluene, high-flash point aromatic naphtha (such as High-Flash Aromatic Naphtha-100 or High-Flash Aromatic Naphtha-150), ethylene glycol butyl ether At least one. The solvent is used to disperse the plastic particles and the conductive agent.

During preparation, the flexible resin is first added to the solvent to obtain a mixed solution, and then the plastic particles and the conductive agent are mixed in the mixed solution and dispersed to obtain the solvent-based conductive ink. Among them, it can be mixed and dispersed by three drums, homogenizer or planetary disperser.

In another embodiment, the conductive ink may also be a foamed conductive ink.

The difference from the above-mentioned solvent-based conductive ink is that the flexible resin of the foamed conductive ink includes two-component polyurethane. The two-component polyurethane includes a polyol and a diisocyanate mixed in a certain ratio, wherein the polyol and the diisocyanate can be introduced into a mold after stirring to be foamed to form a polyurethane foam material. The density of the two-component polyurethane is less than 30 m ³ /kg. When the density of the two-component polyurethane is greater than or equal to 30 m ³ /kg, the conductivity and foaming properties are poor, and the addition of the conductive agent will have a greater impact on the density.

Wherein, the polyol includes at least one of polypropylene glycol (PPG), polytetramethyl ether glycol (PTMEG), and polyether polyol. The diisocyanate includes toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), aliphatic isocyanate (HDI), isophorone diisocyanate (IPDI), hydrogenated phenylmethane diisocyanate ( H12MDI) and at least one of oligomeric diisocyanate.

During preparation, the plastic particles and the conductive agent are mixed in a polyol and dispersed, and then the diisocyanate is added to obtain the foamed conductive ink. The foamed conductive ink is emulsified and stirred at a certain speed, and then introduced into a mold to make it foam to obtain a polyurethane foam material.

In order to assist foaming or improve the properties of foaming materials, the conductive ink may also include at least one of a chain extender, a foaming structure stabilizer, an ammonia catalyst, a metal catalyst, a foaming agent, and a reinforcing additive. An additive. In addition, different colors of pigments can be added depending on the actual application.

The chain extender includes short-chain polyols, such as ethylene glycol (EG), butylene glycol (BG), diethylene glycol, triethylene glycol, 1,2-propylene glycol At least one of (1,2-propanediol), 1,3-propanediol (1,3-propanediol), and 1,6-hexanediol (1,6-hexanediol).

The foam structure stabilizer includes polysiloxane.

The ammonia catalyst is used to accelerate the reaction between polyol and diisocyanate. The ammonia catalyst includes triethylamine (TEA).

The metal catalyst is used to accelerate the reaction between polyol and diisocyanate. The metal catalyst includes at least one of stannous octoate (T9) and dibutyltin dilaurate (T12).

The blowing agent includes at least one of hydrofluorocarbon (HFC), water, dichloromethane, and acetone.

The reinforcing additive is used to increase the strength and hardness of the foamed material. The reinforcing additive includes at least one of calcium carbonate and silicon oxide.

In another embodiment, the flexible resin of the foamed conductive ink may further include at least one of a thermoplastic resin or a thermosetting resin.

Wherein, the thermoplastic resin may include polystyrene (PS), polyethylene (PE), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymer (ABS), polycarbonate (PC), At least one of polyester, nylon, and polyoxymethylene.

The thermosetting resin may include polyurethane (PU), polyisocyanuric acid resin, phenolic resin, urea-formaldehyde resin, self-foaming epoxy resin, composite epoxy resin, polyorganosiloxane (sponge), polyimide ( At least one of self-foaming) and polyimide (composite).

The conductive ink further includes a blowing agent including at least one of hydrofluorocarbon (HFC), water, methylene chloride, and acetone.

During preparation, the plastic particles and the conductive agent are mixed in the flexible resin and dispersed, and then the foaming agent is added to obtain the foamed conductive ink. The foamed conductive ink is emulsified and stirred at a certain speed, and is introduced into a mold to foam to obtain a foamed material.

The present application also provides a conductive element, which is formed by printing (such as screen printing or steel plate printing), coating, and wire drawing of the above-mentioned conductive ink. When the conductive ink is a foamed conductive ink, the conductive ink needs to be foamed and formed in a mold.

Wherein, the conductive element may be, but is not limited to one of a wire and a sensing electrode.

Compared with the engineering structure design in the prior art, the preparation method of the conductive element of the present application has a simple manufacturing process and a lower cost.

The following examples and comparative examples are used to illustrate the application in detail.

Example 1

The SEBS rubber, PVC particles and conductive agent are provided, mixed and dispersed to obtain the conductive ink. The conductive agent is conductive carbon black (produced by Cabot, USA, model VXC72). Wherein, the mass proportion of the SEBS rubber in the conductive ink is 68.72%, and the mass proportion of the PVC particles in the conductive ink is 10%. The mass ratio of the conductive agent in the conductive ink is 21.28%.

Example 2

The difference from Example 1 is that the plastic particles are PMMA particles.

Example 3

The difference from Example 1 is that the flexible resin is water-based PU.

Example 4

The difference from Example 1 is that the flexible resin is oily PU.

Example 5

The difference from Example 1 is that the conductive agent also includes metal powder (dendritic silver-coated copper), and the mass ratio of the metal powder in the conductive ink is 7.09%, and the conductive carbon material is in the The mass ratio in the conductive ink is 14.19%.

Example 6

The difference from Example 1 is that the conductive agent also includes metal powder (dendritic silver-coated copper), the metal powder in the conductive ink accounts for 4.256% of the mass, and the conductive carbon material is in the The mass ratio in the conductive ink is 17.024%.

Comparative example 1

The difference from Example 1 is that the conductive ink does not contain plastic particles, and the mass ratio of the SEBS rubber in the conductive ink is 78.72%.

Comparative example 2

The difference from Comparative Example 1 is that the flexible resin also includes SBS rubber, the mass proportion of SEBS rubber in the conductive ink is 68.72%, and the mass proportion of the SBS rubber in the conductive ink Is 10%.

Comparative example 3

The difference from Comparative Example 1 lies in that the mass ratio of the SEBS rubber in the conductive ink is 24.8%. The conductive agent also includes metal powder (dendritic silver-coated copper), the mass ratio of the metal powder in the conductive ink is 74.4%, and the mass ratio of the conductive carbon material in the conductive ink is 0.8%.

Comparative example 4

The difference from Comparative Example 1 lies in that the mass ratio of the SEBS rubber in the conductive ink is 24.8%. The conductive agent is all metal powder (dendritic silver-coated copper), and the mass ratio of the metal powder in the conductive ink is 75%.

The sensing electrodes were prepared according to the conductive inks prepared in Examples 1-6 and Comparative Examples 1-4. The initial resistance value of the sensing electrode, the resistance value after washing and drying 50 times, the 100-cell adhesion, the tensile recovery rate and the It can be tested for stretch times and other properties.

Among them, the initial resistance value is characterized by square resistance, and the test steps include: 1. Fix the sample on the measuring rod and measure the resistivity ρ of the sample; 2. Use a high-power optical microscope to observe the thickness t of the sample on the glass sheet; 3. The initial resistance value R _{0 is} calculated by the formula R ₀ =ρ/t. The test steps of resistance value after washing and drying 50 times include: cut a sample of 50×50cm with AATCC sampling ruler, weigh 1.8kg, use Whirlpool washing machine and dryer, set water level Medium, washing program Regular, warm water to dissolve 92gWOB washing powder and add The washing machine is turned on, and the test sample is taken out and put into the dryer after the end, the drying program and temperature are set, and the machine is turned on. After the operation is completed, the test sample is taken out and put in the washing machine again. Repeat the above washing and drying steps 50 times. The dried sample is placed in a constant temperature and humidity chamber for at least 4 hours, and then the resistance value after washing and drying 50 times is measured by referring to the above method.

The test steps of the 100-grid adhesion include: draw 100 1mm×1mm squares on the surface of the sample with a 100-grid knife, and then use 3M tape to stick to the 100-grid, and remove the air between the sample and the tape as much as possible. Tear off quickly at a vertical 90-degree angle for 30 seconds, continuously 3-6 times, and judge whether it is qualified (PASS) by the degree of ink peeling. The highest standard is 5B, which means there is no peeling, 0B is the lowest, and the peeling area is greater than 65% and unqualified (NG).

The test steps of the tensile recovery rate include: measuring the original resistance value R ₀ of the sample, after stretching the sample to a fixed length, staying for 1 minute to measure the resistance value R ₁ , after recording the data, returning the sample to the initial state and staying for 1 minute as well And measure the resistance value R ₂ . Among them, since the dimensional change of the sample after tensile recovery is weak, which is not conducive to the accuracy of the experimental results, the tensile recovery rate is defined by the resistance value change rate before and after the tensile recovery, which is calculated according to the following formula: (R ₁ -R ₂ )/ (R ₁ -R ₀ ).

The test steps for the number of stretch recovery times include: take a sample with a fixed length, stretch it 50% of the original length, and then put it back to the initial state, repeat the above stretch recovery step until the resistance change after stretching is not greater than the original resistance value 50%, record the number of stretch recovery times.

The preparation parameters and test results of Examples 1-6 and Comparative Examples 1-4 are recorded in Table 1.

From the above data in Table 1, it can be seen that the sensing electrodes prepared from the conductive inks of Examples 1-6 all have higher stretchable recovery times. Compared with Comparative Example 1-2, since the conductive ink of Examples 1-6 contains plastic particles, the corresponding sensing electrode has a relatively high tensile recovery rate.

Compared with Comparative Examples 3-4, the conductive inks of Examples 1-6 do not contain metal particles or the mass of metal particles is relatively low, so the resistance change rate of the corresponding sensing electrodes is relatively small. Compared with the addition of metal particles in Examples 5-6, the resistance change rate of the sensing electrodes of Examples 1-4 is relatively small.

Compared with the flexible resin of Example 3-4 using PU, the flexible resin of Example 1-2 uses SEBS rubber, so it has a greater tensile recovery rate.

Example 7

Provide PVC particles, polyol (PAPI-27) and conductive agent, mixed and add diisocyanate (XRP-3212) to obtain foamed conductive ink. The conductive agent is carbon nanotubes. Wherein, the weight ratio of the PVC particles in the foamed conductive ink is 15%, the weight ratio of the polyol in the foamed conductive ink is 24.8%, and the diisocyanate is in the foamed conductive ink. The mass ratio in the foamed conductive ink is 39.36%. The mass ratio of the conductive agent in the foamed conductive ink is 21.28%.

Example 8

The difference from Example 7 is that the plastic particles are PMMA particles.

Comparative example 5

The difference from Example 7 is that the conductive agent further includes metal powder. The mass ratio of the metal powder in the foamed conductive ink is 74.4%, and the mass ratio of the conductive carbon material in the foamed conductive ink is 0.8%.

Comparative example 6

The difference from Example 7 is that the conductive agent is all metal powder, and the mass ratio of the metal powder in the foamed conductive ink is 75%.

The foamed conductive inks prepared in Example 7 and Comparative Examples 5-6 were stirred at a speed of 3000 rpm and then introduced into a mold for foaming, thereby obtaining a foamed material. Then, a sensing electrode was prepared according to the foamed material, and the initial resistance value of the sensing electrode, the resistance value after washing and drying 50 times, the 100-cell adhesion, the tensile recovery rate and the number of stretches were tested. . The preparation parameters and test results of Example 7 and Comparative Examples 5-6 are recorded in Table 2.

It can be seen from the above data in Table 2 that the sensing electrodes prepared from the foamed conductive inks of Examples 7-8 all have higher stretchable recovery times. Compared with Comparative Examples 5-6, since the conductive inks of Examples 7-8 contain plastic particles, the corresponding sensing electrodes have relatively higher tensile recovery.

Compared with Comparative Examples 5-6, the conductive inks of Examples 7-8 do not contain metal particles, so the resistance change rate of the corresponding sensing electrodes is relatively small.

Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out. Modifications or equivalent replacements should not depart from the spirit and scope of the technical solutions of the present invention.

Claims (5)

A conductive ink with tensile properties, which is improved in that it is composed of a flexible resin, plastic particles mixed in the flexible resin, and a conductive agent. The flexible resin includes at least one of a rubber-based resin and a polyurethane-based resin. The conductive agent includes at least one conductive carbon material selected from conductive carbon black and carbon nanotubes, the flexible resin accounts for 60%-80% of the conductive ink by mass, and the conductive carbon material is contained in the conductive ink. The proportion of the quality in 20%-40%. The conductive ink with tensile properties according to claim 1, wherein the material of the plastic particles includes at least one of polyvinyl chloride, polymethyl methacrylate, polyethylene, and nylon. The conductive ink with tensile properties according to claim 1, wherein the conductive agent further includes metal powder, and the mass ratio of the conductive carbon material and the metal powder is greater than 2:1. The conductive ink with tensile properties according to claim 1, wherein the rubber includes styrene-ethylene-butylene-styrene block copolymer rubber and styrene-butadiene-styrene block copolymer At least one of rubber, and the polyurethane is water-based polyurethane or oil-based polyurethane. A conductive element, wherein the conductive element is made of the conductive ink according to any one of claims 1-4.