阅读说明：本技术 一种ls-bn/cnf/pva导热复合膜材料及其制备方法 (LS-BN/CNF/PVA heat-conducting composite membrane material and preparation method thereof ) 是由 戴红旗 王秀 于 2021-10-21 设计创作，主要内容包括：本发明公开了一种LS-BN/CNF/PVA导热复合膜材料及其制备方法,属于微型化电子器件设备导热隔膜材料技术领域。该方法采用LS为BN的高效分散剂,得到LS-BN分散液；然后与CNF混合均匀,冷冻干燥制备得到LS-BN/CNF气凝胶；然后将PVA溶液浇铸于所述LS-BN/CNF气凝胶上,干燥压光后得到LS-BN/CNF/PVA导热复合膜材料。与传统复合膜相比,该导热复合膜具有更优异的力学及导热性能,在作为电子设备及其元器件内部导热和包装材料时具有广泛应用。(The invention discloses an LS-BN/CNF/PVA heat-conducting composite film material and a preparation method thereof, belonging to the technical field of heat-conducting diaphragm materials of miniaturized electronic device equipment. The method adopts LS as a high-efficiency dispersant of BN to obtain LS-BN dispersion liquid; then mixing the obtained product with CNF uniformly, and freeze-drying to obtain LS-BN/CNF aerogel; and then casting the PVA solution on the LS-BN/CNF aerogel, and drying and calendaring to obtain the LS-BN/CNF/PVA heat-conducting composite membrane material. Compared with the traditional composite film, the heat-conducting composite film has more excellent mechanical and heat-conducting properties, and can be widely applied as heat-conducting and packaging materials in electronic equipment and components thereof.)

1. A preparation method of an LS-BN/CNF/PVA heat-conducting composite membrane material is characterized in that sodium lignosulfonate is used as a green high-efficiency dispersant of BN to obtain LS-BN dispersion liquid; then mixing the obtained product with CNF uniformly, and freeze-drying to obtain LS-BN/CNF aerogel; and then casting the PVA solution on the LS-BN/CNF aerogel, and drying and calendaring to obtain the LS-BN/CNF/PVA heat-conducting composite membrane material.

2. The preparation method of the LS-BN/CNF/PVA heat-conducting composite film material as claimed in claim 1, which is characterized by comprising the following steps:

1) dissolving LS powder in water, dissolving at room temperature to obtain an LS solution, dispersing BN powder in the LS solution, and stirring at room temperature to obtain an LS-BN dispersion liquid;

2) mixing the LS-BN dispersion liquid and the CNF suspension liquid uniformly, and stirring and mixing the mixture uniformly at room temperature to obtain a uniform LS-BN/CNF mixed liquid; obtaining LS-BN/CNF aerogel after freeze drying;

3) casting the PVA solution on LS-BN/CNF aerogel, and then drying;

4) and (4) after drying, performing calendaring on the material to obtain the LS-BN/CNF/PVA heat-conducting composite film material.

3. The preparation method of the LS-BN/CNF/PVA heat-conducting composite film material as claimed in claim 1 or 2, wherein the concentration of the LS solution is 0.1-2.0 wt.%, and the concentration of BN in the LS-BN dispersion is 3 wt.%.

4. The preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material as claimed in claim 1 or 2, wherein the concentration of the LS solution is 0.5 wt.%.

5. The preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material as claimed in claim 1 or 2, wherein the solid content ratio of BN to CNF is 1:1, the concentration of the LS-BN/CNF mixed solution is 0.5 wt.%, and the LS-BN/CNF aerogel is obtained by stirring for 10min at room temperature and then freeze-drying.

6. The preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material as claimed in claim 1 or 2, wherein the concentration of the PVA solution is 1 wt.%, and the solid content ratio of the PVA solution to the LS-BN/CNF mixed solution is 1: 2.

7. The preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material as claimed in claim 1 or 2, wherein the LS-BN/CNF aerogel is air-dried at 25 ℃ after being cast.

8. The preparation method of the LS-BN/CNF/PVA heat-conducting composite film material as claimed in claim 1 or 2, wherein the LS-BN/CNF/PVA heat-conducting composite film material is obtained by calendaring the composite film under the pressure of 0.2MPa after the composite film is air-dried.

9. LS-BN/CNF/PVA heat-conducting composite membrane material prepared by the method of claim 1 or 2.

Technical Field

The invention belongs to the technical field of heat-conducting diaphragms and packaging materials of miniaturized electronic and electric equipment, and particularly relates to a sodium Lignosulfonate (LS) -hexagonal Boron Nitride (BN)/nano cellulose microfibril (CNF)/polyvinyl alcohol (PVA) heat-conducting composite film material and a preparation method thereof.

Background

The development trend of miniaturization, integration and high power into modern electronic and electrical equipmentThis puts higher demands on the thermal conductive and insulating materials inside the device. Hexagonal Boron Nitride (BN) is considered to be one of the most promising fillers in the preparation of Thermal Interface Materials (TIMs) due to its advantages of good thermal conductivity (185-300W/mK), large energy band gap (5.5 eV), excellent oxidation resistance, good thermal stability and insulation, etc. However, BN exhibits poor dispersibility in water at room temperature, greatly hindering its further use. In order to solve this problem, researchers have made efforts and works in which chemical grafting and physical exfoliation are common methods for improving the dispersibility of BN. For example, researchers basify BN in NaOH solution at 120 ℃ for 24 hours to produce BN-OH, but the-OH grafting rate is only 6.5%, and the reaction temperature is high and the reaction time is long; in addition, mechanical exfoliation of BN by ball milling to prepare Boron Nitride Nanosheets (BNNS) to enhance their dispersion and stability has also been reported: BN, urea and H₂The ball milling of the mixture of O is carried out for 16h at 500rpm, and then the deionized water is used for washing for a plurality of times to remove the redundant urea, which not only causes the great consumption and waste of energy, but also causes the loss of chemicals and the generation of pollutants in the reaction process. Therefore, it is difficult to provide an effective way to improve the dispersibility of BN, whether by chemical grafting or physical exfoliation. Meanwhile, researches show that the aerogel prepared by the freeze drying method can improve more heat conduction channels for the transfer of phonons in the composite material, and the dispersibility of BN has a remarkable influence on the construction of the heat conduction channels, so that the heat conduction performance of the composite material is influenced. Obviously, improving the dispersibility of BN is key to expanding its further applications and optimizing its composite thermal conductivity properties.

Sodium Lignosulfonate (LS) is a derivative of lignin, is widely available and abundant, and can generate about 9.8X 10 during the pulping and papermaking production process every year⁵Tons of lignin. However, the high-value utilization of LS is not fully developed, and most of LS is directly burned as fuel, so that the utilization value is greatly reduced. LS has a hydrophobic main chain and hydrophilic branched chains and simultaneously has a three-dimensional space structure of lignin, so that the LS has good water solubility and provides possibility for the LS to become a high-efficiency dispersant of BN. PVA is a biodegradable high molecular material, and its preparation methodMature process and good film forming performance. Heating to 90 ℃ at room temperature, stirring for 2-3h to completely dissolve to form a uniform solution, and the uniform solution is commonly used as a reinforcing agent for the flexibility and the strength of the composite material. Cellulose is the first natural renewable resource in nature and is widely present in plants. The CNF prepared by the method of combining TEMPO and high-pressure homogenization has the advantages of large length-diameter ratio, uniform size and the like, and is a promising and sustainable green material. However, the intrinsic thermal conductivity of PVA and CNF is very low, and the thermal conductivity of PVA and CNF films at room temperature is only 0.28 and 0.41W/mK, so that the PVA and CNF films cannot be directly used as thermal conductive diaphragm materials.

Therefore, how to improve the dispersion performance of BN, and how to prepare a heat-conducting and insulating composite membrane material with good flexibility by using a proper composite method with PVA and CNF becomes a research direction. The existing CNF-based heat-conducting insulating film material is formed by directly blending BN and CNF and drying the mixture into a film by a blending casting method. The defects of the method are that the dispersion unevenness of BN causes poor heat-conducting property and mechanical strength property of the material, and interface pores among different media are generated in the film forming process, thereby further reducing the mechanical strength and the heat-conducting property of the composite film. The heat dissipation requirement inside the electronic device cannot be met.

Disclosure of Invention

Aiming at the defects of poor dispersibility of BN in water at room temperature and poor mechanical strength and thermal conductivity of a composite membrane prepared from the BN, the invention aims to solve the technical problem of providing an LS-BN/CNF/PVA/thermal conductive composite membrane material. The invention aims to solve another technical problem of providing a preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material. The composite membrane material prepared by the preparation method has excellent mechanical strength and heat conductivity, meets the internal heat conduction requirement of electronic and electric equipment, effectively improves the strength performance and the heat conductivity of the composite membrane, and improves the use efficiency of the composite membrane material.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a preparation method of an LS-BN/CNF/PVA heat-conducting composite membrane material adopts sodium lignosulfonate as a green high-efficiency dispersant of BN to obtain LS-BN dispersion liquid; then mixing the obtained product with CNF uniformly, and freeze-drying to obtain LS-BN/CNF aerogel; then casting the PVA solution on the LS-BN/CNF aerogel, and drying and calendaring to obtain an LS-BN/CNF/PVA heat-conducting composite membrane material; the method comprises the following steps:

1) dissolving LS powder in water, dissolving at room temperature to obtain an LS solution, dispersing BN powder in the LS solution, and stirring at room temperature to obtain an LS-BN dispersion liquid;

2) mixing the LS-BN dispersion liquid and the CNF suspension liquid uniformly, and stirring and mixing the mixture uniformly at room temperature to obtain a uniform LS-BN/CNF mixed liquid; obtaining LS-BN/CNF aerogel after freeze drying;

3) casting the PVA solution on LS-BN/CNF aerogel, and then drying;

4) and (4) after drying, performing calendaring on the material to obtain the LS-BN/CNF/PVA heat-conducting composite film material.

According to the preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material, the concentration of the LS solution is 0.1-2.0 wt.%, and the concentration of BN in the LS-BN dispersion liquid is 3 wt.%.

The LS-BN/CNF/PVA heat-conducting composite membrane material is prepared by the method, and the concentration of the LS solution is 0.5 wt.%.

According to the preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material, the solid content ratio of BN to CNF is 1:1, the concentration of the LS-BN/CNF mixed solution is 0.5 wt.%, and the LS-BN/CNF aerogel is obtained by stirring for 10min at room temperature and then freeze-drying.

According to the preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material, the concentration of a PVA solution is 1 wt.%, and the solid content ratio of the PVA solution to the LS-BN/CNF mixed solution is 1: 2.

The preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material comprises the step of air drying the LS-BN/CNF aerogel at 25 ℃ after the LS-BN/CNF aerogel is cast.

According to the preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material, after the composite membrane is air-dried, the composite membrane is calendered under the pressure of 0.2MPa to obtain the LS-BN/CNF/PVA heat-conducting composite membrane material.

The LS-BN/CNF/PVA heat-conducting composite membrane material prepared by the method.

Has the advantages that: compared with the prior art, the invention has the advantages that:

(1) the LS can be extracted and modified from black liquor generated in the pulping and papermaking processes, the solubility is good, the three-dimensional space structure of lignin is possessed, the LS which is green and environment-friendly and has wide sources is used as a dispersant of BN, and the dispersibility of BN in water at room temperature is improved.

(2) A freeze-drying method is adopted to construct abundant heat conduction network channels in the LS-BN/CNF aerogel, and a foundation is laid for improving the heat conduction coefficient of the composite membrane. The PVA with good film forming property is adopted to further enhance the mechanical strength of the composite film, overcome the defects of poor strength and low heat conductivity of the existing material, and obtain the LS-BN/CNF/PVA heat-conducting composite film material with excellent heat-conducting property and mechanical strength.

(3) The LS-BN/CNF/PVA heat-conducting composite film material disclosed by the invention has the advantages that the heat conduction and strength performance are improved, the heat conduction requirement in electronic and electric equipment can be met, and the practicability is good.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with examples are described in detail below.

Example 1

A preparation method of an LS-BN0/CNF/PVA heat-conducting composite film material specifically comprises the following steps:

1) 1.08g of BN powder was dispersed in 33.92g of water and stirred at room temperature for 10min to give a BN suspension with a concentration of 3 wt.%, designated LS-BN 0;

2) subsequently, 4.75g of the LS-BN0 dispersion and 5.89g of a CNF suspension with a concentration of 0.806 wt.% were mixed, and the system was stirred at room temperature for 10min by adding deionized water to a concentration of 0.5 wt.% to obtain a uniform LS-BN0/CNF mixture; pouring the mixed solution into a plastic culture dish with the diameter of 55mm, and freezing and drying at-70 ℃ and under the condition of 0.1Pa to obtain LS-BN0/CNF aerogel;

3) and then pouring 9.5g of PVA solution with the concentration of 1 wt.% on the LS-BN0/CNF aerogel, drying at room temperature (25 ℃), and finally calendaring the material under the pressure of 2MPa to obtain the LS-BN0/CNF/PVA heat-conducting composite film material.

The LS-BN0/CNF/PVA product is tested, and the result is as follows: the thermal conductivity coefficient is 0.644W/mK, and the maximum tensile strength is 12.92 MPa.

Example 2

A preparation method of an LS-BN/CNF/PVA heat-conducting composite membrane material is that 0.035g of LS is dissolved in 34.97g of deionized water to obtain an LS solution with the concentration of 0.1 wt.%, the preparation method of the LS-BN/CNF/PVA heat-conducting composite membrane material is the same as that of example 1, wherein 1.08g of BN is dispersed in 33.92g of LS solution with the concentration of 0.1 wt.%, and the label is LS-BN 0.1.

The finally obtained LS-BN0.1/CNF/PVA heat-conducting composite film material is tested, and the result is as follows: the thermal conductivity is 0.670W/mK, and the maximum tensile strength is 14.82 MPa.

Example 3

A preparation method of an LS-BN/CNF/PVA heat-conducting composite membrane material comprises the step of dissolving 0.175g of LS in 34.83g of deionized water to obtain an LS solution with the concentration of 0.5 wt.%. The preparation method of the LS-BN/CNF/PVA heat conductive composite membrane material was the same as in example 1, wherein 1.08g of BN was dispersed in 33.92g of LS solution with a concentration of 0.5 wt.%, labeled as LS-BN 0.5.

The finally obtained LS-BN0.5/CNF/PVA heat-conducting composite film material is tested, and the result is as follows: the thermal conductivity coefficient is 1.223W/mK, and the maximum tensile strength is 19.49 MPa.

Example 4

A preparation method of an LS-BN/CNF/PVA heat-conducting composite membrane material comprises the step of dissolving 0.35g of LS in 34.65g of deionized water to obtain an LS solution with the concentration of 1.0 wt.%. The preparation method of the LS-BN/CNF/PVA heat conductive composite membrane material was the same as in example 1, wherein 1.08g of BN was dispersed in 33.92g of LS solution with a concentration of 1.0 wt.%, labeled as LS-BN 1.0.

The finally obtained LS-BN1.0/CNF/PVA heat-conducting composite film material is tested, and the result is as follows: the thermal conductivity coefficient is 0.757W/mK, and the maximum tensile strength is 13.84 MPa.

Example 5

A preparation method of an LS-BN/CNF/PVA heat-conducting composite membrane material comprises the step of dissolving 0.70g of LS in 34.30g of deionized water to obtain an LS solution with the concentration of 2.0 wt.%. The preparation method of the LS-BN/CNF/PVA heat conductive composite membrane material was the same as in example 1, wherein 1.08g of BN was dispersed in 33.92g of LS solution with a concentration of 2.0 wt.%, labeled as LS-BN 2.0.

The finally obtained LS-BN2.0/CNF/PVA heat-conducting composite film material is tested, and the result is as follows: the thermal conductivity is 0.465W/mK, and the maximum tensile strength is 11.63 MPa.

The preparation method of the pure CNF membrane comprises the following steps:

(1) taking 23.57g of CNF suspension with the concentration of 0.806 wt.%, adding deionized water to enable the concentration of the CNF suspension to be 0.5 wt.%, stirring for 10min at room temperature to obtain uniformly dispersed CNF suspension, pouring the CNF suspension into a plastic culture dish with the diameter of 55mm, and freeze-drying at-70 ℃ and 0.1Pa to obtain CNF aerogel;

(2) 11.79g of a CNF suspension with a concentration of 0.806 wt.% were subsequently poured onto the CNF aerogel, dried at room temperature (25 ℃) and finally the material was calendered under a pressure of 2MPa to give pure CNF membrane material.

The properties of the thermally conductive composite films prepared in the above examples 1, 2, 3, 4 and 5 were compared with those of the pure CNF film, and the results are shown in the following table 1.

Table 1 examples 1-5 thermally conductive composite film properties

Heat conduction composite film sample	CNF membranes	Example 1	Example 2	Example 3	Example 4	Example 5
							Coefficient of thermal conductivity (W/mK)	0.41	0.64	0.67	1.22	0.76	0.47
Improvement in Heat conductivity (%)	/	56.10	63.41	197.56	85.37	14.63
							Maximum tensile Strength (MPa)	9.96	12.92	14.82	19.49	13.84	11.63
Maximum tensile Strength improvement (%)	/	29.72	48.80	95.68	38.96	17.40
							Maximum tensile Strength improvement (%)	/	29.72	48.80	95.68	38.96	17.40

As can be seen from the above examples, the thermal conductivity and tensile strength of the LS-BN/CNF/PVA thermal conductive composite film tend to increase and then decrease with the increase of the LS content. The pure CNF film had a thermal conductivity of 0.41W/mK and a tensile strength of 9.96 MPa. When the LS concentration is 0.5 wt.%, the thermal conductivity and the tensile strength of the composite membrane reach the highest values, namely 1.22W/mK and 19.49MPa respectively, and are respectively improved by 197.56% and 95.68% compared with a pure CNF membrane. When LS is not added, the thermal conductivity coefficient and the tensile strength of the composite film are respectively 0.64W/mK and 12.92 MPa; when the LS concentration is 2.0 wt.%, the thermal conductivity and the tensile strength of the composite film are respectively 0.47W/mK and 11.63MPa, and the thermal conductivity and the strength are reduced compared with the LS concentration of 0.5 wt.%.