A method for preparing modified lignin-based conductive gel

Abstract

A method for preparing a modified lignin-based conductive gel comprises the following steps: adjusting the pH value of black liquor with a sulfuric acid solution, stirring for 1 hour and then keeping the mixture in a constant temperature water bath for 1 hour, vacuum filtering to separate the filter cake, washing the filter cake with deionized water several times and then drying to obtain black liquor lignin; carbonizing the black liquor lignin under N2 atmosphere, and ball milling the carbonized lignin to obtain a conductive filler; heating and stirring an α-lipoic acid monomer and a cross-linking agent until they are melted, and then continuously stirring for 1 hour to obtain a yellow transparent liquid, adding a conductive filler under stirring and continuing stirring for 10 minutes, and then placing the mixture in an oil bath for ultrasonic treatment to obtain a CLP / ALA suspension; adding a FeCl3 solution to the CLP / ALA suspension to obtain a mixed solution and cooling it at room temperature. The gel prepared by the method has high sensitivity to tensile deformation and excellent skin fit, and can quickly self-repair and restore good tensile properties when damaged by external stimulation.

Description

Technical Field

[0001] The present invention relates to the technical field of wearable hydrogel preparation, and in particular to a method for preparing a modified lignin-based conductive gel. Background Art

[0002] The development of health monitoring devices such as wearable hydrogel sensing materials not only facilitates timely medical assistance for athletes, but also provides real-time monitoring. The gel can also monitor human activities remotely by connecting to a wireless transmitter, which has attracted considerable attention. However, hydrogel sensors still have problems such as poor mechanical properties, narrow application temperature range, difficulty in repairing physical damage, and poor adhesion. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for preparing a modified lignin-based conductive gel, the purpose of which is to prepare a lignin-based conductive gel with excellent stretchability, self-healing properties and high conductivity. The lignin-based conductive gel has high sensitivity to tensile deformation and excellent skin adhesion, and can be assembled into a multifunctional sensor to detect human body movement. The specific scheme is as follows:

[0004] A method for preparing a modified lignin-based conductive gel comprises the following steps:

[0005] (1) Preparation of black liquor lignin: The pH value of the black liquor was adjusted to 2 using a 50% sulfuric acid solution, and the mixture was stirred for 1 hour and then placed in a constant temperature water bath for 1 hour. The filter cake was then separated by vacuum filtration. The filter cake was washed several times with deionized water and dried for 24 hours to obtain black liquor lignin.

[0006] (2) carbonizing the black liquor lignin obtained in step (1) at 900° C. for 2 h under N2 atmosphere protection to obtain carbonized lignin, and the carbonized lignin is ball-milled in a ball mill to serve as a conductive filler;

[0007] (3) heating and stirring the α-lipoic acid monomer and the cross-linking agent until they are melted, and then continuously stirring for 1 hour after obtaining a yellow transparent liquid, and adding the conductive filler of step (2) under stirring and continuing stirring for 10 minutes, and then placing in an oil bath for ultrasonic treatment to prepare a CLP / ALA suspension;

[0008] (4) Add a 0.01 mol / L FeCl3 solution to the CLP / ALA suspension prepared in step (3) to obtain a mixed solution, and cool the mixed solution to room temperature.

[0009] Furthermore, the black liquor lignin in step (2) is carbonized in a tubular furnace.

[0010] Furthermore, the stirring is carried out using a magnetic stirrer at a stirring speed of 200 rpm.

[0011] Furthermore, in step (3), the amount of the cross-linking agent added is 3wt% of the α-lipoic acid monomer, and the cross-linking agent is polyvinyl alcohol 20000.

[0012] Furthermore, the amount of the conductive filler added in step (3) is 2% to 30% of the mass of the α-lipoic acid monomer, and the amount of FeCl3 added is 0.02 to 0.5% of the total mass of the α-lipoic acid monomer and the crosslinking agent.

[0013] Furthermore, the FeCl3 solution described in step (4) is added dropwise using a constant pressure separatory funnel, with a drop rate of 10s / drop and a room temperature of 20-30°C.

[0014] An improved lignin-based conductive gel (hereinafter referred to as PALA-CLPx gel) prepared by the preparation method of the improved lignin-based conductive gel.

[0015] Advantages of the present invention

[0016] 1. The preparation method of the improved lignin-based conductive gel of the present invention can greatly improve the strength and conductivity of the prepared PALA-CLPx gel by adding conductive filler (hereinafter referred to as CLP) after ball milling of carbonized lignin and FeCl3 solution. The PALA-CLPx gel has high sensitivity to tensile deformation and excellent skin conformability. As the CLP content increases from 5% to 12.5%, the ultimate stress of the PALA-CLPx gel increases monotonically from 0.15MPa to 0.58Mpa. When the PALA-CLPx gel is damaged by external stimuli, it can achieve rapid self-repair and restore good tensile properties, and can be assembled into a multifunctional sensor to detect human body movement.

[0017] 2. The PALA-CLPx gel prepared by the method of the present invention has good uniformity, lignin particles are evenly dispersed in the base glue, and the elongation is as high as 3000% and has excellent adhesion performance, and the bonding strength can reach 278kpa. When it is used as a strain sensor, it can easily capture weak motion signals such as bending of elbows and fingers and the peristalsis of the Adam's apple when pronouncing and drinking water, and can accurately and stably convert the motion signals into electrical signals to realize the sensing function. The prepared PALA-CLPx gel is a material with excellent sensing performance, and the preparation process is simple and recyclable. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a preparation flow chart of the preparation method of the modified lignin-based conductive gel of the present invention;

[0019] Figure 2It is a schematic structural diagram of a device for preparing a modified lignin-based conductive gel according to the present invention.

[0020] In the figure:

[0021] 1: Constant pressure separatory funnel; 2: Iron clamp; 3: Beaker; 4: Oil bath; 5: Mixed liquid; 6: Iron stand; 7: Magnetic stirrer. DETAILED DESCRIPTION

[0022] The present invention is further explained below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that this specific implementation method is not intended to limit the scope of rights of the present invention.

[0023] like Figure 1 and Figure 2 As shown, the preparation method of a modified lignin-based conductive gel provided in this specific embodiment comprises the following steps:

[0024] (1) Preparation of black liquor lignin: The pH value of the black liquor was adjusted to 2 using a 50% sulfuric acid solution, and the mixture was stirred with a magnetic stirrer for 1 hour and then placed in a constant temperature water bath for 1 hour. The filter cake was then separated by vacuum filtration, and the filter cake was washed several times with deionized water and dried in a blast dryer for 24 hours to obtain black liquor lignin;

[0025] (2) carbonizing the black liquor lignin obtained in step (1) at 900° C. for 2 h in a tube furnace under N2 atmosphere protection to obtain carbonized lignin, and the carbonized lignin was ball-milled in a ball mill to serve as a conductive filler (hereinafter referred to as CLP);

[0026] (3) Figure 2 As shown, a beaker 3 is placed in an oil bath 4 filled with heat-conductive silicone oil, and the oil bath 4 is placed on an existing magnetic stirrer 5, and then alpha lipoic acid monomer (hereinafter referred to as ALA) and a cross-linking agent added in an amount of 3 wt% of ALA are placed in the beaker 3, heated at a temperature of 125° C. by a magnetic stirrer 7 and stirred at a speed of 200 rpm until melted, and after obtaining a yellow transparent liquid, stirring is continued at a speed of 200 rpm for 1 hour, and a conductive filler added in an amount of 2% to 30% of the mass of ALA in step (2) is added under stirring and stirring is continued for 10 minutes, and the mixture is placed in an oil bath 4 for oil bath ultrasonic treatment to prepare a CLP / ALA suspension; the cross-linking agent is polyvinyl alcohol 20000 (hereinafter referred to as PVA).

[0027] (4) A constant pressure diversion funnel 1 clamped on an iron stand 6 by an iron clamp 2 is added dropwise with a 0.01 mol / L FeCl3 solution to the CLP / ALA suspension prepared in step (3). The dropping rate is 10 s / drop, and the amount of FeCl3 solution added is 0.02-0.5% of the total mass of the α-lipoic acid monomer and the cross-linking agent to obtain a mixed solution. The mixed solution is placed in a culture dish and cooled at room temperature of 20-30° C. to obtain a modified lignin-based conductive gel (hereinafter referred to as PALA-CLPx gel).

[0028] The improved lignin-based conductive gel is prepared by the method for preparing the improved lignin-based conductive gel.

[0029] The PALA-CLPx gel prepared by the above method has high sensitivity to tensile deformation and excellent skin adhesion. When the CLP addition amount is 5%, the conductivity of the gel is 0.038sm -1 When the CLP addition amount is 7.5%, the conductivity of the gel is 0.574sm -1 When the CLP addition amount is 12.5%, the conductivity of the gel is 0.816sm -1 .

[0030] As the CLP content increases, the ultimate stress of PALA-CLPx gel increases monotonically from 0.15MPa to 0.58MPa. When PALA-CLPx gel is damaged by external stimuli, it can quickly self-repair and restore good tensile properties, and can be assembled into a multifunctional sensor to detect human movement.

[0031] Figure 2 The device shown includes an iron stand, an iron clamp, a constant pressure separating funnel, a magnetic stirrer, an oil bath and a beaker, wherein the iron clamp is mounted on the iron stand, the constant pressure separating funnel is mounted on the iron clamp, the magnetic stirrer is arranged below the constant pressure separating funnel, the oil bath is arranged on the magnetic stirrer, and the beaker is arranged in the oil bath and corresponds to below the nozzle of the constant pressure separating funnel.

[0032] The following is a comparison of the sensitivity factor, self-healing properties, self-healing efficiency, weight of the object supported by the hydrogel and the bonding strength of the present practical example with the existing stretchable conductive gel, as shown in Table 1:

[0033] Table 1 Comparison between this embodiment and existing stretchable conductive gel

[0034]

[0035] Note: [a] SM: Movement mode sensed by the sensor. [b] GF: Sensitivity factor. [c] SHP: Self-healing property. [d] HE: Self-healing efficiency. [e] AHW: Weight of an object supported by the hydrogel. [f] AS: Adhesion strength.

[0036] The analysis results in Table 1 show that compared with existing stretchable conductive gels, PALA-CLPx gel exhibits excellent multifunctional characteristics in terms of ultra-stretchability, autonomous self-healing, self-adhesion, high ionic conductivity and wide environmental tolerance range.

Claims

1. A method for preparing a modified lignin-based conductive gel, characterized in that: The following steps are involved: (1) Preparation of black liquor lignin: The pH value of the black liquor was adjusted to 2 using a 50% sulfuric acid solution, and the mixture was stirred for 1 hour and then placed in a constant temperature water bath for 1 hour. The filter cake was then separated by vacuum filtration. The filter cake was washed several times with deionized water and dried for 24 hours to obtain black liquor lignin. (2) carbonizing the black liquor lignin obtained in step (1) at 900° C. for 2 h under N2 atmosphere protection to obtain carbonized lignin, and ball milling the carbonized lignin to serve as a conductive filler; (3) heating the α-lipoic acid monomer and the cross-linking agent at a temperature of 125° C. and stirring until they are melted, wherein the amount of the cross-linking agent added is 3 wt % of the α-lipoic acid monomer, and the cross-linking agent is polyvinyl alcohol 20000, and stirring is continued for 1 hour after a yellow transparent liquid is obtained, and the conductive filler of step (2) is added under stirring and stirring is continued for 10 minutes, wherein the amount of the conductive filler added is 2% to 30% of the mass of the α-lipoic acid monomer, and then ultrasonically treated in an oil bath to prepare a CLP / ALA suspension; (4) Adding a 0.01 mol / L FeCl3 solution to the CLP / ALA suspension prepared in step (3), wherein the amount of FeCl3 added is 0.02-0.5% of the total mass of the α-lipoic acid monomer and the cross-linking agent, and cooling the obtained mixed solution to room temperature.

2. The method for preparing a modified lignin-based conductive gel according to claim 1, characterized in that: The black liquor lignin carbonization in step (2) is carried out using a tubular furnace.

3. The method for preparing a modified lignin-based conductive gel according to claim 1, characterized in that: The stirring was carried out using a magnetic stirrer at a stirring speed of 200 rpm.

4. The method for preparing a modified lignin-based conductive gel according to claim 1, characterized in that: The FeCl3 solution in step (4) is added dropwise using a constant pressure separatory funnel at a dropping rate of 10s / drop and a room temperature of 20-30°C.

5. An improved lignin-based conductive gel prepared by the method for preparing the improved lignin-based conductive gel according to any one of claims 1 to 4.

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