CN113214621B - A kind of preparation and recovery method of liquid metal composite material with anisotropy - Google Patents

Abstract

A liquid metal composite material is prepared through mixing Liquid Metal (LM) with Polycaprolactone (PCL), stirring while heating to 170-180 deg.C to obtain a flowing composite, and cooling at ordinary temp. The method is simple and easy to obtain, and the prepared liquid metal composite material (LM-PCL) has excellent stretchability and plasticity; the conductive film has excellent anisotropy of one surface being conductive and one surface being insulating, and the conductivity of the conductive surface is high; has degradable recoverability and simple recovery method.

Description

A kind of preparation and recovery method of liquid metal composite material with anisotropy

technical field

The present invention is in the technical field of liquid metal materials, in particular to a method for preparing and recycling liquid metal composite materials.

Background technique

Liquid metal has excellent properties such as low melting point, high electrical conductivity, high thermal conductivity, low viscosity and fluidity, and has good thermal conductivity and fluidity on the macroscopic level. Therefore, it can flow freely while maintaining good electrical conductivity. At the same time, liquid metal is also the best material for microfluidics. Due to its low toxicity and biocompatibility, gallium-based liquid metal is non-toxic and harmless to the human body. It can be used in the field of biological materials and can also be used as a drug delivery carrier. Through phase transition, liquid metal can achieve reversibility between solid and liquid, thereby adjusting the stiffness of composite materials. Because the atoms in liquid metal cannot move freely like in solid state, they vibrate around the equilibrium node position. The vibration energy and frequency of liquid metal are several million times higher than those of solid atoms.

Liquid metal composite materials have good application prospects due to their manufacturing advantages such as stretchability, flexibility, impact resistance, high efficiency, and low cost. The liquid metal is used as a modified filler to infiltrate the flexible polymer, and the liquid metal can be redirected with the deformation of the matrix. Stretchable composite materials have good application prospects in wearable implantable fields, self-healing materials, electromagnetic shielding materials and other fields. High molecular polymers have the characteristics of flexibility and light weight. Polycaprolactone (PCL/(C ₆ H ₁₀ O ₂ ) _n ) has good biocompatibility and biodegradability, and is used in surgery in the medical field Sutures, drug release carriers, tumor therapy carriers, etc. The composite material of liquid metal and high molecular polymer has very high design flexibility. At present, liquid metal is synthesized with most other high molecular polymers. Due to the properties of the polymer, the composite material cannot be degraded and recycled, nor does it have anisotropic properties, and its application in medical and other fields is limited.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of a liquid metal composite material.

Another object of the present invention is to provide a method for recovering the liquid metal composite material prepared by the above method.

The object of the present invention is achieved through the following technical solutions:

A preparation method of a liquid metal composite material is characterized in that: liquid metal (LM) is mixed with polycaprolactone (PCL), and the temperature is raised to 170-180° C. while stirring to form a fluid dynamic composite, and then placed in a The surface of the PET film is cooled and solidified at room temperature.

Further, in the mixing, the liquid metal (LM) is first heated to 80-90° C., and then polycaprolactone (PCL) is added one by one while stirring.

Further, the above stirring is performed by using a glass rod, and the stirring rate is 50-60 rpm. After the temperature rise is completed, the end of the glass rod is placed in the mixture formed by LM and PCL, close to 1/3 of the surface of the mixture, and the stirring is continued for 30-60min.

In the preparation process, we found that if the amount of PCL is too large, the prepared composite will lose its electrical conductivity, but very little PCL and liquid metal (LM) are difficult to completely penetrate into its interior, and because PCL itself has a large Sticky, easy to stick to the stirrer, and it is difficult to distribute the liquid metal evenly inside it.

In the present invention, by first heating LM to a melting point slightly higher than PCL, slowly adding PCL, stirring slowly, and then slowly heating up to a higher temperature, in this process, with the slow change of temperature and the participation of liquid metal, synergistic The viscosity of PCL was regulated, and EGaIn was completely infiltrated into PCL by stirring with a glass stirring rod, and it was ensured that it had excellent hardness and toughness. According to the larger density difference between PCL and LM, adjust the stirring position of the glass stirring rod in the mixture at high temperature, and promote the liquid metal to form most of the LM in PCL at a slow stirring rate to sink, and from bottom to top component content Gradually decrease, while PCL moves up, and the structure gradually decreases from top to bottom, forming anisotropy of front (upper end) insulation and back (lower end) conduction, and since LM is mainly concentrated on the back of the material, its conductive end is more uniform The structure dispersed in the composite material has more excellent electrical conductivity.

Further, the liquid metal is preferably a gallium indium alloy (EGaIn).

Further, the mass ratio of the above-mentioned gallium indium alloy and polycaprolactone is 7-9:1.

Further, the above-mentioned heating rate is 1 to 1.5° C./min.

The most specific, a kind of preparation method of liquid metal composite material is characterized in that, carry out according to the following steps:

Step (1): Take the liquid metal (LM) and heat it to 80~90℃. At 50~60rpm, add polycaprolactone (PCL) one by one while stirring with a glass rod. The mass ratio of LM and PCL is 7~ 9:1;

Step (2): After the addition is completed, continue stirring, and slowly raise the temperature to 170~180°C;

Step (3): After the heating is completed, move the end of the glass rod to 1/3 of the surface of the mixture formed by LM and PCL, and continue stirring for 30-60 min to obtain a fluid dynamic complex in which PCL completely coats LM;

Step (4): The liquid composite is placed on the PET surface, and cooled and solidified at room temperature.

The recovery method of the liquid metal composite material prepared by the above method is characterized in that: the recovery is to place the liquid metal composite material in a 3 mol/L hydrochloric acid solution, let it stand for 12 to 18 hours, remove the solution and its surface floats, collect Liquid metal that settles at the bottom.

The present invention has the following technical effects:

The method of the invention is simple and easy to obtain, the prepared liquid metal composite material (LM-PCL) has excellent stretchability and plasticity, and can be prepared into different shapes; it exhibits excellent anisotropy in which one side is conductive and the other side is insulating, and the conductive The electrical conductivity of the surface is high, which can be effectively used in fields with special requirements of anisotropy such as acupuncture and moxibustion in traditional Chinese medicine; it has degradability and recyclability, and the recycling method is simple.

Description of drawings

Fig. 1 is a schematic flow chart of the preparation of the liquid metal composite material according to the present invention.

Figure 2: Front and back and longitudinal cross-sectional views of the liquid metal composite material prepared by the present invention.

Figure 3: Schematic diagram of the anisotropy of the liquid metal composite material prepared by the present invention.

Figure 4: SEM image of the liquid metal composite material prepared by the present invention.

Figure 5: The drawable state and the fiber state of the liquid metal composite material prepared by the present invention.

Figure 6: Infrared spectrum analysis diagram of the liquid metal composite material prepared by the present invention.

Fig. 7: The front energy spectrum analysis diagram of the liquid metal composite material prepared by the present invention.

Detailed ways

The present invention will be specifically described by the following examples. It is necessary to point out that the following examples are only used to further illustrate the present invention, and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can SUMMARY OF THE INVENTION Some non-essential improvements and adjustments are made to the present invention.

Example 1

A preparation method of liquid metal composite material is carried out according to the following steps:

Step (1): Take gallium indium alloy (EGaIn) and heat it to 80 ℃, at 50 rpm, add polycaprolactone (PCL) one by one while stirring with a glass rod, the mass ratio of EGaIn and PCL is 7:1;

Step (2): After the addition is completed, continue stirring, and slowly raise the temperature to 170°C;

Step (3): after the temperature rise is completed, move the end of the glass rod to the mixture formed by LM and PCL near 1/3 of the surface of the mixture, and continue stirring for 30 min to obtain a fluid dynamic complex in which PCL completely coats LM;

Step (4): The liquid composite is placed on the PET surface, and cooled and solidified at room temperature.

Example 2

A method for preparing a liquid metal composite material, characterized in that, the steps are as follows:

Step (1): Take gallium indium alloy (EGaIn) and heat it to 90 ℃, at 60 rpm, add polycaprolactone (PCL) one by one while stirring with a glass rod, the mass ratio of EGaIn and PCL is 8:1;

Step (2): After the addition is completed, continue stirring, and slowly raise the temperature to 175°C;

Step (3): After the temperature rise is completed, move the end of the glass rod to the mixture formed by LM and PCL near 1/3 of the surface of the mixture, and continue stirring for 60 min to obtain a fluid dynamic complex in which PCL completely coats LM;

Step (4): The liquid composite is placed on the PET surface, and cooled and solidified at room temperature.

Example 3

A method for preparing a liquid metal composite material, characterized in that, the steps are as follows:

Step (1): Take gallium indium alloy (EGaIn) and heat it to 85 ℃, at 55 rpm, add polycaprolactone (PCL) one by one while stirring with a glass rod, the mass ratio of EGaIn and PCL is 9:1;

Step (2): After the addition is completed, continue stirring, and slowly raise the temperature to 180°C;

Step (3): after the temperature rise is completed, move the end of the glass rod to the mixture formed by LM and PCL near 1/3 of the surface of the mixture, and continue stirring for 50 min to obtain a fluid dynamic complex in which PCL completely coats LM;

Step (4): The liquid composite is placed on the PET surface, and cooled and solidified at room temperature.

The surface state of the liquid metal composite material prepared by the invention is black on the front, the main component is PCL, and the back is gray and contains a large amount of liquid metal. Its cross section is a composite material of many granular liquid metals mixed with PCL, as shown in Figure 2. Its internal composition distribution is shown in Figure 3. PCL is mainly distributed in the upper part of the composite material, and the liquid metal is deposited in the lower part of the composite material. anisotropy.

Fig. 4 is the SEM image of the transverse cross-section near the back of the liquid metal composite materials prepared in the present invention and the comparative example, wherein Fig. 4(a) is the LM prepared by 90wt% liquid metal and mass ratio of 10wt% PCL in Example 3 of the present invention -PCL composite material, from the figure, the smooth droplet shape is liquid metal, the size of the droplet is relatively uniform, the average size is about 80 μm, the rough part is PCL, the liquid metal and PCL are mixed, and the liquid metal droplets are connected to each other, And the liquid metal is evenly distributed. Figure 4(b) is a cross-sectional SEM image of the LM-PCL composite prepared with 80 wt% liquid metal and 20 wt% PCL by mass. The liquid metal droplets in the figure have poor uniformity in size, with an average size of about 150 μm. The connection between the droplets was blocked by PCL, and the droplet distribution was uneven, and it was detected that it did not have electrical conductivity. Figure 4(c) shows the LM-PCL composite prepared with 60 wt% liquid metal and 40 wt% PCL by mass. The cross section of the composite material shows that a small amount of liquid metal is distributed in a large amount of PCL material. The liquid metal composite material has no electrical conductivity and is an insulator.

At high temperature, the composite material is in a dark gray fluid state, and has high viscosity and plasticity. Through high temperature compression molding, wire drawing or injection of the LM-PCL composite material, different morphological structures at room temperature can be obtained, as shown in Figure 5. .

，1471~1396cm^-1处有（—CH₂—）的变形振动吸收峰刚出现；2943~2867cm^-1有（—CH₂—）伸缩振动吸收峰出现；1364cm^-1和1418cm^-1处均有（—CH₃）的特征吸收峰出现，表明了—CH₃结构的存在。PCL的黑色波峰在3341cm^-1处有—OH的伸缩振动峰，而LM-PCL复合材料中的红色波峰中并无—OH结构。Fig. 6 shows that at 1729~1239 cm ^-1 , the infrared image of PCL has a strong peak position, which belongs to the characteristic absorption peak of ester group, indicating that both pure PCL and the LM-PCL composite material prepared by the present invention contain ester group

, 1471~1396cm ^-1 has (—CH ₂ —) deformation vibration absorption peak just appeared; 2943~2867cm ^-1 has (—CH ₂ —) stretching vibration absorption peak; 1364cm ^-1 and 1418cm ^-1 have both The characteristic absorption peak of (—CH ₃ ) appeared, indicating the existence of the—CH ₃ structure. The black peak of PCL has a stretching vibration peak of —OH at 3341cm ^-1 , while the red peak of LM-PCL composite has no —OH structure.

In Fig. 7, from Fig. 7(a) to Fig. 7(e) are the front SEM image of the liquid metal composite material, and the composition distribution diagram of C, Ga, In, and O elements on the front surface of the composite material. In the front element composition, the atomic composition content is 77.23% C atoms, 20.27% O atoms, 2.16 Ga atoms, 0.34% In atoms, the content of liquid metal on the front is very small, and the content of PCL is relatively high. Therefore, the front side of the composite material does not have electrical conductivity, and the resistance test is carried out on the front and longitudinal sections of the liquid metal composite material in turn. The test result is that the front resistance of the liquid metal composite material is infinite, and the resistance value of the middle longitudinal section is 4.03Ω. , the resistance value gradually decreases, which is consistent with the schematic representation of the structure in Figure 3.

Comparative Example 1:

To prepare 100% pure PCL, the specific steps are as follows:

Put 50ml of water in a 100ml beaker and heat to 60°C, take 5g of PCL solid particles into a glass container and stir with glass. The PCL in the beaker became mucus, then slowly heated to 180°C, and then the medicine spoon was taken out and placed on the solid PET film, and waited for it to solidify at room temperature.

Above 60°C, PCL can be melted into a liquid state, but its viscosity is extremely high.

During the process of heating and stirring, we found that the viscosity of PCL did not change significantly with the increase of temperature, and a mucus formed on the glass container and glass rod.

Comparative Example 2:

A method for preparing a liquid metal composite material, characterized in that, the steps are as follows:

Take gallium indium alloy (EGaIn) and heat it to 180 °C. At 55 rpm, add polycaprolactone (PCL) one by one with a glass rod close to the bottom of the container while stirring. The mass ratio of EGaIn and PCL is 9:1, and then continue to stir. After 50 min, EGaIn completely penetrated into PCL to form a fluid dynamic mixture, which was placed on the PET surface and cooled and solidified at room temperature.

At a lower temperature (below 170°C), it is difficult for high content of EGaIn to infiltrate into low-content PCL, and it needs to be above 170°C to achieve the above-mentioned high-content EGaIn infiltration into low-content PCL. Although the LM-PCL composite material was prepared in a high temperature environment, the composite material was fragile, not easy to deform and stretch, and could not form structures such as drawing state and fiber state, and the distribution uniformity of EGaIn droplets in PCL was poor. In the same transverse section of the material, there are places where there is a large amount of liquid metal accumulation, and there are places where there is no liquid metal at all.

We also tried to use water as a medium to prepare LM-PCL materials in water. Although PCL in water is less viscous and easier to stir, LM is extremely fluid in water, and it is difficult to form dispersed droplets, and LM is still very Difficult to fully enter the PCL.

Example 4

Degradation and recycling of liquid metal composites:

The LM-PCL composite material prepared in Example 3 was placed in a glass container, and 3 mol/L HCl solution was added to completely submerge the composite material, after soaking for 16.5 hours.

During this process, the edge of the composite material gradually turned white, and more white matter floated to the surface of the hydrochloric acid solution, while more droplets settled and aggregated at the bottom of the container. It can be seen that the ester group in PCL is hydrolyzed under acidic conditions, thereby realizing the separation of liquid metal and PCL.

Claims (3)

1. The preparation method of the liquid metal composite material is characterized by comprising the following steps of:

step (1): heating liquid metal LM to 80-90 ℃, and adding polycaprolactone PCL into the liquid metal LM by a glass rod while stirring at 50-60rpm;

step (2): after the addition is finished, continuously stirring, and slowly raising the temperature to 170-180 ℃;

and (3): after the temperature rise is finished, moving the tail end of the glass rod to a position, close to 1/3 of the surface of the mixture, in the mixture formed by the LM and the PCL, and continuously stirring for 30-60min to obtain a flow dynamic compound with the LM completely coated by the PCL;

and (4): and (3) placing the liquid compound on the surface of PET, and cooling and solidifying the liquid compound in a room-temperature environment.

2. The method of preparing a liquid metal composite of claim 1, wherein: the liquid metal is gallium-indium alloy, and the mass ratio of the gallium-indium alloy to the polycaprolactone is 7 to 9.

3. A method of recycling a liquid metal composite produced by the method of claim 1, wherein: and the recovery is to place the liquid metal composite material in a 3mol/L hydrochloric acid solution, stand for 12 to 18h, remove the solution and the surface floats thereof, and collect the liquid metal settled at the bottom.

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