CN110746563A - PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material and preparation method thereof - Google Patents

Abstract

The invention relates to a PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material and a preparation method thereof, wherein a ball-milling intercalation stripping technology is adopted, PEG intercalation is put into a lamella of h-BN, and PEG intercalation BN nanosheets obtained after intercalation stripping are added in the synthesis process of polyurethane, so that the PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material is prepared in situ; the composite material has high heat-conducting property, and excellent insulating property and mechanical property; the method has the advantages of less solvent consumption, environmental protection, simple operation, easy control of conditions, low sensitivity to the environment, low energy consumption and low production cost, and is beneficial to industrial production and application.

Description

A kind of PEG ball mill intercalation h-BN modified polyurethane thermal conductive composite material and its preparation method

technical field

The invention relates to the technical field of polymer materials, in particular to a PEG ball-milled intercalation h-BN modified polyurethane thermally conductive composite material and a preparation method thereof.

Background technique

With the rapid development of science and technology and industry, the research on thermally conductive composite materials has been greatly promoted. Among them, filled thermally conductive materials have become a research hotspot due to their simple preparation process, low cost, convenient process control and high efficiency. The thermal conductivity of the filled thermally conductive composites will be affected by the particle size of the filler, the properties of the filler, the compounding of the filler, the amount of the filler and the microstructure of the filler.

Polyurethane is a polymer material containing repeating structural units of carbamate groups (-NH-COO-) in the main chain of macromolecules, and is an ester derivative of carbamate. Polyurethane is widely used in coatings, adhesives, fibers, foams, and paving materials due to its good mechanical strength, solvent resistance, high hardness, wear resistance, good elasticity, and excellent low temperature performance. . In addition, due to the rapid development of industry in recent years, polyurethane materials have been increasingly used in high-power heavy electronic machinery, electronic products and artificial organs, etc., but the performance of polyurethane is poor, and its thermal conductivity is 0.19W/( m·K), these products are prone to generate a lot of heat during use. If the heat cannot be discharged in time, the performance of the polyurethane material will be degraded, which will not only reduce the service life of the material, but also lead to safety accidents.

Hexagonal boron nitride (h-BN), a crystal composed of nitrogen atoms and boron atoms, has a graphite lattice structure, also known as white graphene, each layer of B and N atoms is sp2 hybridized to form 3 B-N Covalent bonds form a graphite-like plane hexagonal network structure, and there is a strong covalent bond between atoms in the layer. In addition, h-BN has an energy bandgap of 5.8 eV, a dielectric constant of about 5, a breakdown voltage of 800 mV/m, and a theoretical thermal conductivity of 2000 W/(m·K). The thermal conductivity (λ) is about 600W/(m·K), and h-BN nanosheets have a large aspect ratio and significant thermal anisotropy. The thermal conductivity in the horizontal direction is about 20-30 times that in the vertical direction. With good insulation, high thermal conductivity, low thermal expansion coefficient, low dielectric constant and good thermal stability, it is the most ideal insulating thermal conductive filler so far.

SUMMARY OF THE INVENTION

In order to solve the technical problem of poor thermal conductivity of polyurethane materials, a PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material and a preparation method thereof are provided. The polyurethane composite material prepared by the method of the invention has good thermal conductivity, insulation and excellent comprehensive mechanical properties.

To achieve the above object, the present invention realizes through the following technical solutions:

A preparation method of a PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material, comprising the following steps:

(1) put h-BN and intercalating agent PEG into the ball milling tank, add ball milling aid, solvent, water and NaOH solution to form material, carry out ball milling, obtain mixture after ball milling, and dry the mixture to obtain PEG intercalation layer BN nanosheets;

(2) After preliminary stirring and dispersion of polyether polyol (PPG), PEG intercalated BN nanosheets and dispersant, ultrasonic treatment is carried out, and then the prepolymer is obtained by drying;

(3) placing the prepolymer in a closed reaction vessel, adding 4,4'-diphenylmethylmethane diisocyanate (MDI) under stirring conditions to carry out heating reaction, vacuuming simultaneously, and obtaining polyurethane after the in-situ polymerization reaction finishes Precursor; the polyurethane precursor is heated and cured to obtain a PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material.

Further, the ball milling aid in step (1) is benzyl benzoate; the solvent is absolute ethanol; the concentration of NaOH solution is 0.2-0.5mol/L; the particle size of the h-BN is 6 μm, 12 μm, 16 μm One or more of the PEG; the relative molecular mass of the PEG is one or more of 6000g/mol, 10000g/mol, and 20000g/mol;

In the process of the ball milling, zirconia balls are used, the particle size of the zirconia balls is 2mm-15mm, and the mass ratio of the material to the zirconia balls is 1:(1-1.5).

The larger the molecular weight of PEG, the larger the interlayer spacing.

Further, the mass ratio of h-BN, PEG, ball milling aid, solvent, water and NaOH solution described in step (1) is (15-50):(15-18):(0.1-0.5):(70 -85):100:(0.05-0.1).

Further, in the step (1), the rotational speed of the ball milling is 300rpm-360rpm, the ball milling time is 12h-24h, and the ball milling is alternately performed forward and reverse every 1h.

Further, the dispersant in step (2) is cetylammonium bromide (CTAB) or polyvinylpyrrolidone (PVP). CTAB plays an electrostatic repulsion and steric hindrance effect in BN to prevent BN agglomeration, and the long ethylene chain of PVP surrounds BN to play a steric hindrance effect, both of which are beneficial to the dispersion of BN.

Further, in step (2), the mass ratio of polyether polyol, PEG intercalated h-BN nanosheet, and dispersant is 100:(5-25):(0.3-0.6).

Further, the preliminary stirring time in step (2) is 2min-12min; the ultrasonic treatment temperature is 35°C-65°C, the ultrasonic treatment power is 100W-6000W, and the ultrasonic treatment time is 0.5h-5h; The drying is vacuum drying at 120° C., the drying vacuum degree is 0.03 atm-0.12 atm, and the drying time is 0.5 h-1.5 h.

Further, the mass ratio of ether polyol (PPG) and 4,4'-diphenylmethylmethane diisocyanate (MDI) in the prepolymer described in step (3) is 100:(20-23).

Further, the vacuum degree of vacuuming in step (3) is 2000Pa-4000Pa, the speed of the stirring condition is 0.2r/s-0.4r/s, the temperature of the heating reaction is 65 ℃-75 ℃, the reaction The time is 0.8h-1.2h; the heating and curing is drying and curing in an electric heating constant temperature blast drying oven, the curing temperature is 80°C-110°C, and the curing time is 6h-8h.

Another aspect of the present invention provides a PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material prepared by the above preparation method, comprising the following components in parts by weight: 100 parts of polyether polyol resin, 4,4'-diol 20-23 parts of benzyl methane diisocyanate, 5-25 parts of PEG intercalated BN nanosheets, and 0.3-0.6 parts of dispersant.

Beneficial technical effects:

(1) The ball milling intercalation peeling technology adopted in the present invention utilizes the strong shearing action between rigid abrasive particles in the high-energy ball mill to peel off h-BN, and at the same time of ball milling, the huge shear energy generates high temperature, which makes h-BN The surface of the sheet is activated, and the introduction of an alkaline solvent can introduce a large number of active sites on the surface of h-BN, thereby increasing the interfacial interaction between the h-BN nanosheets, which is more conducive to the exfoliation of h-BN.

(2) h-BN has a layered structure, but most of them are stacked and agglomerated together. The forces received during the mechanical ball milling process are mainly shear force and impact force. Under the combined action of these two mechanical external forces, boron nitride The cross-sectional size and plane size of h-BN become smaller, but in the process of reducing the number of layers, the specific surface area of h-BN increases, and it is in a thermodynamically unsteady state. In the present invention, the guest molecule intercalating agent PEG is added between the h-BN layers, and the interlayer force is reduced by the intercalation method, thereby reducing the peeling resistance to achieve effective peeling. Distinct flake boron nitride, BN nanosheets obtained after PEG intercalation and exfoliation have better thermal conductivity.

(3) In the process of traditional mechanical ball milling of boron nitride, there is the phenomenon that the grinding ball impacts the raw material particles, and the severe shearing action can easily cause structural defects in the boron nitride plane, resulting in the anti-oxidation ability and chemical resistance of the ball-milled product. Corrosion ability and the like are weakened, and the present invention adds benzyl benzoate as a ball-milling aid when ball-milling the intercalated h-BN, which can reduce the collision and destruction of the boron nitride by the balls during ball-milling.

(4) the present invention uses less organic solvent consumption than traditional liquid phase stripping technology, is more environmentally friendly, and is simple to operate, easy to control conditions, relatively low in sensitivity to the environment, low in energy consumption, and low in production cost, Conducive to industrial production applications.

(5) The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material according to the present invention has high thermal conductivity, as well as excellent insulating properties and mechanical properties.

Description of drawings

1 is a scanning electron microscope image of the PEG intercalated BN nanosheets obtained in Example 8, wherein a is the h-BN without ball milling intercalation, b is the PEG intercalated BN nanosheets, and the scales in the figure are all 2 μm.

Detailed ways

The present invention is further described below with reference to the accompanying drawings and specific embodiments, but does not limit the scope of the present invention.

Example 1

The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material of this embodiment includes the following components by weight: 100 g of PPG resin, 22.52 g of MDI, 20 g of PEG intercalated BN nanosheets (h-BN particle size 6 μm , the relative molecular mass of PEG is 6000g/mol), 0.5g of dispersant CTAB.

Example 2

The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material of this embodiment includes the following components by weight: 100 g of PPG resin, 22.52 g of MDI, 20 g of PEG intercalated BN nanosheets (h-BN particle size 12 μm , the relative molecular mass of PEG is 10000g/mol), 0.5g of dispersant CTAB.

Example 3

The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material of this embodiment includes the following components by weight: 100 g of PPG resin, 22.52 g of MDI, 20 g of PEG intercalated modified BN nanosheets (h-BN particles The diameter is 16 μm, the relative molecular mass of PEG is 10000 g/mol), and the dispersant CTAB is 0.5 g.

Example 4

The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material of this embodiment includes the following components by weight: 100 g of PPG resin, 22.52 g of MDI, 20 g of PEG intercalated modified BN nanosheets (h-BN particles Diameter 6μm, the relative molecular mass of PEG is 10000g/mol), 0.5g of dispersant PVP.

Example 5

The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material of this embodiment includes the following components by weight: 100 g of PPG resin, 22.52 g of MDI, 20 g of PEG intercalated modified BN nanosheets (h-BN particles Diameter 6μm:16μm=1:1, the relative molecular mass of PEG is 20000g/mol), 0.5g of dispersant CTAB.

Example 6

The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material of the present embodiment includes the following components by weight: 100 g of PPG resin, 22 g of MDI, 10 g of PEG intercalated modified BN nanosheets (h-BN particle size 6μm:12μm=1:1, the relative molecular mass of PEG is 10000g/mol:20000g/mol=2:1), 0.4g of dispersant PVP.

Example 7

The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material of the present embodiment includes the following components by weight: 100 g of PPG resin, 23 g of MDI, 25 g of PEG intercalated modified BN nanosheets (h-BN particle size 12 μm, the relative molecular mass of PEG 10000g/mol:20000g/mol=2:1), 0.6g of dispersant CTAB.

Example 8

The preparation method of the PEG ball milling intercalation h-BN modified polyurethane thermally conductive composite material of embodiment 1-5, comprises the following specific steps:

(1) Put 48gh-BN and 16g of intercalating agent PEG into the ball milling tank, add 0.2g ball milling aid, 100mL absolute ethanol, 100mL water and 5mL of 0.5mol/L NaOH solution, carry out ball milling, add 330g zirconia Ball milling beads (zirconia with a particle size of 12-15mm accounts for 30wt%, zirconia with a particle size of 8-10mm accounts for 50wt%, and zirconia with a particle size of 2mm accounts for 20wt%), ball milling speed 360rpm, ball milling time 20h, positive and negative every 1h Alternately perform ball milling, obtain a mixture after ball milling, and dry the mixture to obtain PEG intercalated BN nanosheets;

(2) respectively according to the formula in the embodiment 1-5, after accurately weighing the corresponding PPG, PEG intercalated BN nano-sheets, dispersing agent with an electronic balance to carry out preliminary stirring and dispersing 2-3min, then carry out ultrasonic treatment, ultrasonic treatment The temperature of the prepolymer is 45°C, the power of ultrasonic treatment is 2000W, after 30min of treatment, it is placed in a 120°C vacuum drying oven to dry to obtain the prepolymer, the drying vacuum degree is 0.1atm, and the drying time is 1h;

(3) Place the prepolymer in a closed reaction vessel (build an experimental device, fix the four-necked flask in a collector-type constant temperature heating magnetic stirrer, connect the stirrer to the middle port, seal the left port with a rubber stopper, and connect the right port to circulating water Type multi-purpose vacuum pump, the front port is the feeding port, sealed with a rubber stopper), the heating reaction at 70 ° C is carried out under the condition of a stirring speed of 0.3r/s, and MDI is slowly added to carry out in-situ polymerization while vacuuming (the degree of vacuum is 0.3 r/s). 3000Pa), the polyurethane precursor was obtained after the reaction for 1 h; after the reaction, the polyurethane precursor was poured into the mold that had been preheated to 100 ° C, and then placed in an electric heating constant temperature blast drying oven for heating and curing, and the setting temperature was 100 ° C, After a drying time of 360 min, the cured sample was taken out to obtain a PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material.

The PEG intercalated BN nanosheets obtained in step (1) were observed by scanning electron microscope, the SEM image is shown in Figure 1, wherein a is the h-BN without ball milling intercalation, and b is the PEG intercalated BN nanosheets , it can be seen from Figure 1 that compared with the h-BN without ball milling and intercalation in the a picture, the h-BN sheet in the b picture becomes thinner, forming BN nanosheets, which shows that PEG can be used for BN in the process of ball milling. Effective intercalation peeling.

Example 9

The preparation method of the PEG ball milling intercalation h-BN modified polyurethane thermally conductive composite material of embodiment 6-7, comprises the following specific steps:

(1) Put 48gh-BN and 16g of intercalating agent PEG into the ball milling tank, add 0.2g ball milling aid, 100mL absolute ethanol, 100mL water and 5mL of 0.3mol/L NaOH solution, carry out ball milling, add 330g zirconia Ball milling beads (zirconia with a particle size of 12-15mm accounts for 30wt%, zirconia with a particle size of 8-10mm accounts for 50wt%, and zirconia with a particle size of 2mm accounts for 20wt%), ball milling speed 320rpm, ball milling time 24h, positive and negative every 1h Alternately perform ball milling, obtain a mixture after ball milling, and dry the mixture to obtain PEG intercalated BN nanosheets;

(2) respectively according to the formula in the embodiment 6-7, after accurately weighing the corresponding PPG, PEG intercalated BN nano-sheets, dispersing agent with an electronic balance to carry out preliminary stirring and dispersing 5-10min, then carry out ultrasonic treatment, ultrasonic treatment The temperature of the prepolymer is 55°C, the power of ultrasonic treatment is 4000W, and after 30min of treatment, the prepolymer is dried in a vacuum drying oven at 120°C, the drying vacuum degree is 0.08atm, and the drying time is 1.5h;

(3) Place the prepolymer in a closed reaction vessel (build an experimental device, fix the four-necked flask in a collector-type constant temperature heating magnetic stirrer, connect the stirrer to the middle port, seal the left port with a rubber stopper, and connect the right port to circulating water Type multi-purpose vacuum pump, the front port is the feeding port, sealed with a rubber stopper), the heating reaction at 70 ° C is carried out under the condition of a stirring speed of 0.3r/s, and MDI is slowly added to carry out in-situ polymerization while vacuuming (the degree of vacuum is 0.3 r/s). 3000Pa), the polyurethane precursor was obtained after the reaction for 1 h; after the reaction, the polyurethane precursor was poured into the mold that had been preheated to 100 ° C, and then placed in an electric heating constant temperature blast drying oven for heating and curing, and the setting temperature was 100 ° C, After a drying time of 360 min, the cured sample was taken out to obtain a PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material.

Comparative Example 1

The PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material of this embodiment includes the following components by weight: 100 g of PPG resin, 22.52 g of MDI, 10 g of PEG intercalated BN nanosheets (h-BN particle size 6 μm , the relative molecular mass of PEG is 10000g/mol), 0g of dispersant CTAB.

The preparation method of the composite material of Comparative Example 1 is the same as that of Example 8.

The performance data of the composite materials prepared in Examples 1-7 and Comparative Example 1 are shown in Table 1.

Table 1 Performance data of the composite materials of Examples 1-7 and Comparative Example 1

Claims (10)

1. a preparation method of PEG ball milling intercalation h-BN modified polyurethane thermally conductive composite material, is characterized in that, comprises the steps: (1) put h-BN and intercalating agent PEG into the ball milling tank, add ball milling aid, solvent, water and NaOH solution to form material, carry out ball milling, obtain mixture after ball milling, and dry the mixture to obtain PEG intercalation layer BN nanosheets; (2) after preliminary stirring and dispersing of polyether polyol, PEG intercalated BN nanosheets and dispersant, ultrasonic treatment is carried out, and then the prepolymer is obtained by drying; (3) placing the prepolymer in a closed reaction vessel, adding diisocyanate under agitation to carry out a heating reaction, vacuuming simultaneously, and obtaining a polyurethane precursor after the in-situ polymerization reaction; the polyurethane precursor is heated and cured to finally obtain PEG Ball-milled intercalated h-BN modified polyurethane thermally conductive composites. 2. the preparation method of a kind of PEG ball milling intercalation h-BN modified polyurethane thermal conductive composite material according to claim 1, is characterized in that, ball milling aid described in step (1) is benzyl benzoate; Described The solvent is absolute ethanol; the concentration of NaOH solution is 0.2mol/L～0.5mol/L; the particle size of the h-BN is one or more of 6 μm, 12 μm and 16 μm; the relative molecular mass of the PEG is 6000g One or more of /mol, 10000g/mol, 20000g/mol. 3. the preparation method of a kind of PEG ball milling intercalation h-BN modified polyurethane thermal conductivity composite material according to claim 1, is characterized in that, described in step (1), h-BN, PEG, ball milling aid, solvent The mass ratio of , water and NaOH is (15-50):(15-18):(0.1-0.5):(70-85):100:(0.05-0.1). 4. the preparation method of a kind of PEG ball milling intercalation h-BN modified polyurethane thermal conductivity composite material according to claim 1, is characterized in that, in the process of described ball milling, use zirconia ball mill beads, described zirconia ball mill beads The particle size is 2mm～15mm, and the mass ratio of the material to the zirconia ball mill beads is 1:(1-1.5); the rotational speed of the ball mill is 300rpm～360rpm, the time of the ball mill is 12h～24h, and the front and back are alternated every 1h Perform ball milling. 5. the preparation method of a kind of PEG ball milling intercalation h-BN modified polyurethane thermal conductivity composite material according to claim 1, is characterized in that, described in step (2), dispersant is cetyl ammonium bromide or Polyvinylpyrrolidone. 6. the preparation method of a kind of PEG ball milling intercalation h-BN modified polyurethane thermal conductivity composite material according to claim 1, is characterized in that, in step (2), polyether polyol, PEG intercalation BN nano-sheet, dispersion The mass ratio of the agent is 100:(5-25):(0.3-0.6). 7. the preparation method of a kind of PEG ball milling intercalation h-BN modified polyurethane thermal conductive composite material according to claim 1, is characterized in that, the time of preliminary stirring described in step (2) is 2min～12min; Described The ultrasonic treatment temperature is 35°C to 65°C, the ultrasonic treatment power is 100W to 6000W, and the ultrasonic treatment time is 0.5h to 5h; The drying is vacuum drying at 120° C., the drying vacuum degree is 0.03 atm to 0.12 atm, and the drying time is 0.5 h to 1.5 h. 8. the preparation method of a kind of PEG ball milling intercalation h-BN modified polyurethane thermal conductivity composite material according to claim 1, is characterized in that, described in step (3), diisocyanate is 4,4 '-diphenylmethane Methane diisocyanate; the mass ratio of ether polyol and diisocyanate in the prepolymer is 100:(20-23). 9. the preparation method of a kind of PEG ball milling intercalation h-BN modified polyurethane thermal conductive composite material according to claim 1, is characterized in that, in step (3), the vacuum degree of vacuuming is 2000Pa～4000Pa, and described stirring The speed of the conditions is 0.2r/s～0.4r/s, the temperature of the heating reaction is 65°C～75°C, and the reaction time is 0.8h～1.2h; The heating and curing is drying and curing in an electric heating constant temperature blast drying oven, the curing temperature is 80°C-110°C, and the curing time is 6h-8h. 10. A PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material prepared according to the preparation method of any one of claims 1 to 9.

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