A hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film and preparation method thereof

Abstract

The present invention discloses a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film and a preparation method thereof. Hexagonal boron nitride is ball-milled in a hydroxyethyl cellulose aqueous solution, and then the hydroxyethyl cellulose is removed with deionized water to obtain a boron nitride nanosheet / water suspension; para-aramid fiber and KOH are uniformly dispersed in dimethyl sulfoxide to obtain a para-aramid nanofiber / dimethyl sulfoxide dispersion; the boron nitride nanosheet / water suspension is homogenized and uniformly mixed with the para-aramid nanofiber / dimethyl sulfoxide dispersion, and then vacuum filtered and hot pressed in sequence to obtain a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film. The present invention uses para-aramid nanofiber (ANF) as a polymer substrate and BNNS as a thermal conductive filler, and through vacuum filtration and hot pressing, the composite material is endowed with excellent thermal conductivity.

Description

Technical Field

[0001] The invention relates to the field of preparation of fiber-based composite films, in particular to a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film and a preparation method thereof. Background Art

[0002] Heat dissipation is critical to the performance, lifespan and reliability of electronic equipment. With the rapid development of communication technology and electronic technology, heat dissipation issues have become more prominent in the fields of integrated electronic packaging, light-emitting diodes, energy storage and aerospace.

[0003] There are many types of heat sinks currently, but most of them are in direct contact with the surface of electronic components, directly absorbing heat and then dissipating it. Of course, for general electronic devices, this method of directly taking away heat through the heat sink can barely meet its heat dissipation needs. However, for large precision instruments, the heat dissipation power is far from meeting the heat dissipation requirements of the instrument. Therefore, new high thermal conductivity materials are needed to help solve this challenge. In this context, high-performance thermal interface materials (TIMs) have received widespread attention. However, there are still problems with its thermal conductivity, such as the thermal conductivity (TC) is still low.

[0004] Selecting fillers and polymer matrices with high intrinsic TC is an effective way to improve the thermal conductivity of TIMs. Common inorganic thermal conductive fillers are divided into three types: metal materials, carbon-based materials, and ceramic materials. Among them, metal materials will increase the conductivity and density of polymer composites, reduce the chemical stability of the materials, and are easily corroded, limiting their application in the field of electrical insulation. Carbon-based materials are difficult to disperse evenly in the substrate and also have high conductivity, so they may cause intermittent failures of electronic devices, limiting their application range as fillers. However, composite materials prepared from ceramic materials can have both high thermal conductivity and electrical insulation properties. Boron nitride nanosheets (BNNS), one of the ceramic materials, have high chemical stability, electrical insulation and chemical corrosion resistance, so BNNS can be used to improve the thermal conductivity of TIMs, but the inherent low TC of most polymers currently severely limits their wide application in fields that require high TC values ​​and rapid heat dissipation, so they cannot be compounded with BNNS, and it is difficult to improve the thermal conductivity of TIMs. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film and a preparation method thereof, taking para-aramid nanofiber (ANF) as a polymer substrate and BNNS as a thermal conductive filler, and through vacuum filtration and hot pressing, giving the composite material excellent thermal conductivity.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film comprises the following steps:

[0008] S1, ball-milling hexagonal boron nitride in a hydroxyethyl cellulose aqueous solution, wherein the mass ratio of hexagonal boron nitride to hydroxyethyl cellulose in the hydroxyethyl cellulose aqueous solution is (1-3):(0.3-0.5), and then removing the hydroxyethyl cellulose with deionized water to obtain a boron nitride nanosheet / water suspension;

[0009] The para-aramid fiber and KOH are uniformly dispersed in dimethyl sulfoxide, wherein the mass ratio of the para-aramid fiber to KOH is (300-500): (300-500), to obtain a para-aramid nanofiber / dimethyl sulfoxide dispersion;

[0010] S2, homogenizing the boron nitride nanosheet / water suspension and evenly mixing it with the para-aramid nanofiber / dimethyl sulfoxide dispersion, and then vacuum filtering and hot pressing in sequence to obtain a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film.

[0011] Preferably, in the hydroxyethyl cellulose aqueous solution described in S1, the ratio of hydroxyethyl cellulose to deionized water is (300-500) mg: (100-300) mL.

[0012] Preferably, the ratio of hexagonal boron nitride to the hydroxyethyl cellulose aqueous solution in S1 is (1-3) g: (10-30) ml, and the hexagonal boron nitride is ball-milled in the hydroxyethyl cellulose aqueous solution for 12-24 hours.

[0013] Preferably, S1 washes the ball-milled suspension with 30-50 mL of deionized water for 3-5 times, and then dilutes it with deionized water to a concentration of 1-4 mg / mL of boron nitride nanosheets to obtain a boron nitride nanosheet / water suspension.

[0014] Preferably, S1 stirs the para-aramid fiber and KOH in dimethyl sulfoxide at a rate of 300 to 400 rpm for 156 to 180 hours to obtain a para-aramid nanofiber / dimethyl sulfoxide dispersion.

[0015] Furthermore, the ratio of KOH to dimethyl sulfoxide is (300-500) mg: (100-300) mL.

[0016] Preferably, S2 homogenizes the boron nitride nanosheets / water suspension at 50-90 MPa for 120-180 min.

[0017] Preferably, the vacuum filtration described in S2 is carried out at 0.06-0.09 MPa for 10-20 min.

[0018] Preferably, the hot pressing in S2 is performed at 200-240° C. for 10-15 min.

[0019] A hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film obtained by any of the above methods for preparing a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] The invention discloses a method for preparing a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film, wherein para-aramid nanofiber (ANF) is used as a polymer substrate and boron nitride nanosheet (BNNS) is used as a thermal conductive filler, wherein hydroxyethyl cellulose is used to assist in ball-milling hexagonal boron nitride to prepare a high aspect ratio BNNS with large lateral size and small thickness, which can greatly improve the intrinsic thermal conductivity of BNNS, and the intrinsic TC value of ANF is 1.07 W m -1 K -1 , which is higher than other polymers, making the interface density of the composite material lower and the contact area of ​​the interface larger, resulting in a longer phonon mean free path, reduced phonon scattering, and giving the composite material excellent thermal conductivity. Through vacuum filtration and hot pressing, ANF and BNNS are effectively compounded, and BNNS are oriented in the plane to construct a continuous thermal conductive network in the plane, so that the composite material has good thermal conductivity and can be applied in fields with high thermal conductivity requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1a This is the SEM image of BNNS obtained by deionized water stripping under 50 MPa conditions in comparative example 1.

[0023] Figure 1b This is the SEM image of the BNNS obtained by peeling under 50 MPa conditions in Example 1 of the present invention.

[0024] Figure 2 for Figure 1a The obtained BNNS and Figure 1b Size comparison of the obtained BNNS.

[0025] Figure 3 is the in-plane thermal conductivity of the BNNS / ANF composite film homogenized under different pressures.

[0026] Figure 4 This is a cross-sectional SEM image of the BNNSS / ANF composite film obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0028] The present invention discloses a method for preparing a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film, and the specific steps are as follows:

[0029] (1) Weigh 300-500 mg of hydroxyethyl cellulose and dissolve it in 100-300 mL of deionized water to obtain a hydroxyethyl cellulose aqueous solution with a concentration of 1 mg / mL to 5 mg / mL.

[0030] (2) Take 10-30 ml of the hydroxyethyl cellulose aqueous solution prepared in (1), add 1-3 g of hexagonal boron nitride (h-BN), ball mill for 12-24 h, wash with deionized water 3-5 times, i.e., add 30-50 mL of deionized water each time, then centrifuge, finally combine the supernatant, dilute the obtained boron nitride nanosheets to a concentration of 1 mg / mL to 4 mg / mL with deionized water, and obtain a boron nitride nanosheet (BNNS) / water suspension.

[0031] (3) The BNNS / water suspension prepared in (2) is homogenized at 50-90 MPa using a microfluidizer for 120-180 min to obtain a uniformly dispersed BNNS / water suspension for later use.

[0032] (4) Weigh 300-500 mg of para-aramid fiber and 300-500 mg of KOH, add them into 100-300 mL of DMSO, and stir at a rate of 300-400 rpm for 156-180 h to obtain a para-aramid nanofiber (ANF) / DMSO dispersion with a concentration of 1 mg / mL to 5 mg / mL.

[0033] (5) Take the BNNS / water suspension prepared in (3), add it to the ANF / DMSO dispersion obtained in (4) to obtain a mixed solution, and then vacuum filter it at 0.06-0.09 MPa for 10-20 min and hot press it at 220-240° C. for 10-15 min to finally obtain a BNNS / ANF composite film.

[0034] Embodiment 1:

[0035] (1) Weigh 300 mg of hydroxyethyl cellulose and dissolve it in 300 mL of deionized water to obtain a hydroxyethyl cellulose aqueous solution with a concentration of 1 mg / mL.

[0036] (2) Take 10 ml of the hydroxyethyl cellulose aqueous solution prepared in (1), add 1 g of hexagonal boron nitride (h-BN), ball mill for 12 h, wash with deionized water 5 times, i.e., add 30 mL of deionized water each time, then centrifuge, finally combine the supernatants, and dilute the obtained boron nitride nanosheets to a concentration of 1 mg / mL with deionized water to obtain a BNNS / water suspension.

[0037] (3) The BNNS / water suspension prepared in (2) was homogenized at 50 MPa using a microfluidizer for 120 min to obtain a uniformly dispersed BNNS / water suspension for later use.

[0038] (4) Weigh 300 mg of para-aramid fiber and 300 mg of KOH, add them to 100 mL of DMSO, and stir at 400 rpm for 168 h to obtain an ANF / DMSO dispersion with a concentration of 3 mg / mL.

[0039] (5) Take the BNNS / water suspension prepared in (3), add it to the ANF / DMSO dispersion obtained in (4) to obtain a mixed solution, and then vacuum filter it at 0.09 MPa for 10 min and hot press it at 220°C for 10 min to finally obtain a BNNS / ANF composite film.

[0040] like Figure 1b Shown in combination Figure 1a The suspension in step (2) was freeze-dried to obtain a BNNS solid, which was recorded as 1% HEC, while 1 g of hexagonal boron nitride (h-BN) was directly dissolved in 10 ml of deionized water according to step (2) to obtain a BNNS / water suspension, which was then freeze-dried to obtain a solid, which is Comparative Example 1, and the solid is recorded as DI. It can be seen that the boron nitride nanosheets ball-milled with the assistance of hydroxyethyl cellulose have larger lateral dimensions and thinner thickness.

[0041] from Figure 2 It can be seen that the lateral size of the BNNS obtained by stripping with HEC aqueous solution is larger, 5.583 μm, while the lateral size of the BNNS obtained by stripping with deionized water is 1.879 μm, see the table below for details.

[0042]

[0043] from Figure 4 It can be seen that the interface bonding degree between BNNS and ANF is relatively good, the in-plane orientation degree of BNNS is high, and the interface contact area is large, so the interface density is low, which will reduce phonon scattering and make the composite material have excellent thermal conductivity.

[0044] Example 2

[0045] (1) Weigh 300 mg of hydroxyethyl cellulose and dissolve it in 300 mL of deionized water to obtain a hydroxyethyl cellulose aqueous solution with a concentration of 1 mg / mL.

[0046] (2) Take 10 ml of the hydroxyethyl cellulose aqueous solution prepared in (1), add 1 g of hexagonal boron nitride (h-BN), ball mill for 12 h, wash with deionized water 5 times, i.e., add 30 mL of deionized water each time, then centrifuge, finally combine the supernatants, and dilute the obtained boron nitride nanosheets to a concentration of 1 mg / mL with deionized water to obtain a BNNS / water suspension.

[0047] (3) The BNNS / water suspension prepared in (2) was homogenized at 60 MPa using a microfluidizer for 120 min to obtain a uniformly dispersed BNNS / water suspension for later use.

[0048] (4) Weigh 300 mg of para-aramid fiber and 300 mg of KOH, add them to 100 mL of DMSO, and stir at 400 rpm for 168 h to obtain an ANF / DMSO dispersion with a concentration of 3 mg / mL.

[0049] (5) Take the BNNS / water suspension prepared in (3), add it to the ANF / DMSO dispersion obtained in (4) to obtain a mixed solution, and then vacuum filter it at 0.09 MPa for 10 min and hot press it at 220°C for 10 min to finally obtain a BNNS / ANF composite film.

[0050] Example 3

[0051] (1) Weigh 300 mg of hydroxyethyl cellulose and dissolve it in 300 mL of deionized water to obtain a hydroxyethyl cellulose aqueous solution with a concentration of 1 mg / mL.

[0052] (2) Take 10 ml of the hydroxyethyl cellulose aqueous solution prepared in (1), add 1 g of hexagonal boron nitride (h-BN), ball mill for 12 h, wash with deionized water 5 times, i.e., add 30 mL of deionized water each time, then centrifuge, finally combine the supernatants, and dilute the obtained boron nitride nanosheets to a concentration of 1 mg / mL with deionized water to obtain a BNNS / water suspension.

[0053] (3) The BNNS / water suspension prepared in (2) was homogenized at 75 MPa using a microfluidizer for 120 min to obtain a uniformly dispersed BNNS / water suspension for later use.

[0054] (4) Weigh 300 mg of para-aramid fiber and 300 mg of KOH, add them to 100 mL of DMSO, and stir at 400 rpm for 168 h to obtain an ANF / DMSO dispersion with a concentration of 3 mg / mL.

[0055] (5) Take the BNNS / water suspension prepared in (3), add it to the ANF / DMSO dispersion obtained in (4) to obtain a mixed solution, and then vacuum filter it at 0.09 MPa for 10 min and hot press it at 220°C for 10 min to finally obtain a BNNS / ANF composite film.

[0056] Example 4

[0057] (1) Weigh 300 mg of hydroxyethyl cellulose and dissolve it in 300 mL of deionized water to obtain a hydroxyethyl cellulose aqueous solution with a concentration of 1 mg / mL.

[0058] (2) Take 10 ml of the hydroxyethyl cellulose aqueous solution prepared in (1), add 1 g of hexagonal boron nitride (h-BN), ball mill for 12 h, wash with deionized water 5 times, i.e., add 30 mL of deionized water each time, then centrifuge, finally combine the supernatants, and dilute the obtained boron nitride nanosheets to a concentration of 1 mg / mL with deionized water to obtain a BNNS / water suspension.

[0059] (3) The BNNS / water suspension prepared in (2) was homogenized at 90 MPa using a microfluidizer for 120 min to obtain a uniformly dispersed BNNS / water suspension for later use.

[0060] (4) Weigh 300 mg of para-aramid fiber and 300 mg of KOH, add them to 100 mL of DMSO, and stir at 400 rpm for 168 h to obtain an ANF / DMSO dispersion with a concentration of 3 mg / mL.

[0061] (5) Take the BNNS / water suspension prepared in (3), add it to the ANF / DMSO dispersion obtained in (4) to obtain a mixed solution, and then vacuum filter it at 0.09 MPa for 10 min and hot press it at 220°C for 10 min to finally obtain a BNNS / ANF composite film.

[0062] like Figure 3 The thermal conductivity of the composite films with different BNNS loadings is shown in Figure 1. The horizontal axis is the homogenization pressure, and the vertical axis is the in-plane thermal conductivity of the composite film. The in-plane thermal conductivity of the composite film of boron nitride nanosheets and ANF homogenized at 50, 75, and 90 MPa is shown. It can be seen that the thermal conductivity of the composite film of boron nitride nanosheets and ANF homogenized at 75 MPa is the highest, which is 31.5 W m-1 K -1 。

Claims

1. A method for preparing a hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film, characterized in that: The steps include: Step (1), weighing 300 mg of hydroxyethyl cellulose, dissolving it in 300 mL of deionized water to obtain a hydroxyethyl cellulose aqueous solution with a concentration of 1 mg / mL; Step (2), taking 10 ml of the hydroxyethyl cellulose aqueous solution prepared in step (1), adding 1 g of hexagonal boron nitride, ball milling for 12 h, washing with deionized water 5 times, i.e., adding 30 mL of deionized water each time, then centrifuging, and finally combining the supernatants, and diluting the obtained boron nitride nanosheets to a concentration of 1 mg / mL with deionized water to obtain a BNNS / water suspension; Step (3), homogenizing the BNNS / water suspension prepared in step (2) at 75 MPa using a microfluidizer for 120 min to obtain a uniformly dispersed BNNS / water suspension for later use; Step (4), weighing 300 mg of para-aramid fiber and 300 mg of KOH, adding them to 100 mL of DMSO, and stirring at a rate of 400 rpm for 168 h to obtain an ANF / DMSO dispersion with a concentration of 3 mg / mL; Step (5), taking the BNNS / water suspension prepared in step (3), adding it to the ANF / DMSO dispersion obtained in step (4) to obtain a mixed solution, and then vacuum filtering at 0.09 MPa for 10 min and hot pressing at 220° C. for 10 min to finally obtain a BNNS / ANF composite film.

2. A hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film obtained by the preparation method of the hydroxyethyl cellulose ball-milled boron nitride nanosheet / aramid nanofiber composite film according to claim 1.

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