CN110746563B

CN110746563B - A kind of PEG ball mill intercalation h-BN modified polyurethane thermal conductive composite material and preparation method thereof

Info

Publication number: CN110746563B
Application number: CN201911018092.5A
Authority: CN
Inventors: 杨菁菁; 向萌; 周仕龙; 张苏圆
Original assignee: Jiangsu University of Technology
Current assignee: Jiangsu University of Technology
Priority date: 2019-10-24
Filing date: 2019-10-24
Publication date: 2021-06-29
Anticipated expiration: 2039-10-24
Also published as: CN110746563A

Abstract

The invention relates to a PEG ball-milled intercalation h-BN modified polyurethane heat-conducting composite material and a preparation method thereof. The ball-milling intercalation peeling technology is adopted to insert the PEG layer into the h-BN sheet, and the obtained product is obtained after the intercalation is peeled off. The PEG intercalated BN nanosheets are added during the synthesis of polyurethane, and the PEG ball-milled intercalated h-BN modified polyurethane thermally conductive composite material is prepared in situ; the composite material of the present invention has high thermal conductivity and excellent insulating properties. and mechanical properties; the method of the invention 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, which is favorable for industrial production and application.

Description

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

Technical Field

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

Background

With the rapid development of science and technology and industry, research on heat-conducting composite materials is promoted to a great extent, wherein the filling type heat-conducting material becomes a hotspot of research due to simple preparation process, low cost, convenient process control and high efficiency, but the heat-conducting performance of the filling type heat-conducting composite material is influenced by the particle size of the filler, the property of the filler, the compounding of the filler, the using amount of the filler and the microstructure of the filler.

The polyurethane is a macromolecular material with a macromolecular main chain containing a carbamate (-NH-COO-) repeating structural unit, and is an ester derivative of carbamic acid. Polyurethane has a series of properties such as good mechanical strength, solvent resistance, high hardness, wear resistance, good elasticity, excellent low-temperature performance and the like, and is widely applied to the fields of coatings, adhesives, fibers, foamed plastics and paving materials. In addition, in recent years, due to rapid development of industry, polyurethane materials are increasingly used in high-power heavy-duty electronic machinery, electronic products, artificial organs and the like, but the polyurethane materials have poor performance and a thermal conductivity of 0.19W/(m · K), and when the products are used, a large amount of heat is easily generated, and if the heat cannot be discharged in time, the performance of the polyurethane materials is necessarily reduced, so that the service life of the materials is not only reduced, but also safety accidents can be caused.

Hexagonal boron nitride (h-BN), which is a crystal composed of nitrogen atoms and boron atoms, has a graphite lattice structure and is also called as white graphene, each layer of B and N atoms forms 3B-N covalent bonds after being hybridized by sp2 to form a hexagonal network structure similar to a graphite plane, and the atoms in the layer are strongly covalently bonded. In addition, the h-BN energy band width gap is 5.8eV, the dielectric constant is about 5, the breakdown voltage is 800mV/m, the theoretical thermal conductivity coefficient can reach 2000W/(m.K), the actually used h-BN nano sheet has the thermal conductivity coefficient (lambda) of about 600W/(m.K), meanwhile, the h-BN nano sheet has larger length-diameter ratio, the thermal conductivity anisotropy is obvious, the thermal conductivity coefficient in the horizontal direction is about 20-30 times of that in the vertical direction, and the h-BN nano sheet has the characteristics of good insulation, high thermal conductivity coefficient, low thermal expansion coefficient, low dielectric constant, good thermal stability and the like, and is the most ideal insulation type thermal conductive filler so far.

Disclosure of Invention

In order to solve the technical problem of poor heat conductivity of polyurethane materials, a PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material and a preparation method thereof are provided. The polyurethane composite material prepared by the method has good thermal conductivity, insulativity and excellent comprehensive mechanical properties.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a preparation method of a PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following steps:

(1) putting the h-BN and the intercalation agent PEG into a ball milling tank, adding a ball milling auxiliary agent, a solvent, water and a NaOH solution to form a material, carrying out ball milling, obtaining a mixture after ball milling, and drying the mixture to obtain PEG intercalation BN nanosheets;

(2) primarily stirring and dispersing Polyether Polyol (PPG), PEG intercalated BN nanosheets and a dispersing agent, then carrying out ultrasonic treatment, and then drying to obtain a prepolymer;

(3) placing the prepolymer in a closed reaction container, adding 4, 4' -diphenylmethane diisocyanate (MDI) under the stirring condition for heating reaction, simultaneously vacuumizing, and obtaining a polyurethane precursor after the in-situ polymerization reaction is finished; and heating and curing the polyurethane precursor to obtain the PEG ball-milling intercalated h-BN modified polyurethane heat-conducting composite material.

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

zirconia ball grinding beads are used in the ball milling process, the particle size of the zirconia ball grinding beads is 2-15mm, and the mass ratio of the materials to the zirconia ball grinding beads is 1 (1-1.5).

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

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

Further, the rotation speed of the ball milling in the step (1) is 300rpm-360rpm, the ball milling time is 12h-24h, and the ball milling is alternately carried out every 1 h.

Further, in the step (2), the dispersant is cetyl ammonium bromide (CTAB) or polyvinylpyrrolidone (PVP). CTAB plays a role in electrostatic repulsion and steric hindrance in BN to prevent agglomeration of BN, and the ethylene long chain of PVP surrounds the BN to play a role in steric hindrance, so that the CTAB and the PVP are both favorable for dispersion of the BN.

Further, the mass ratio of the polyether glycol, the PEG intercalated h-BN nano sheet and the dispersing agent in the step (2) is 100 (5-25) to (0.3-0.6).

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

Further, the mass ratio of the polyether glycol (PPG) to the 4, 4' -diphenylmethane diisocyanate (MDI) in the prepolymer in the step (3) is 100 (20-23).

Further, the vacuum degree of the vacuum pumping in the 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 ℃, and the reaction time is 0.8-1.2 h; the heating solidification is drying solidification carried out in an electric heating constant temperature air blast drying oven, the solidification temperature is 80-110 ℃, and the solidification time is 6-8 h.

The invention also provides a PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material prepared by the preparation method, which comprises the following components in parts by weight: 100 parts of polyether polyol resin, 20-23 parts of 4, 4' -diphenylmethane diisocyanate, 5-25 parts of PEG intercalated BN nanosheets and 0.3-0.6 part of dispersing agent.

The beneficial technical effects are as follows:

(1) the invention adopts a ball milling intercalation stripping technology, utilizes the strong shearing action among rigid abrasive particles in a high-energy ball mill to strip h-BN, and generates high temperature by using huge shearing energy during ball milling so as to activate the surface of an h-BN lamella, and then a large amount of active sites can be introduced on the surface of the h-BN lamella by introducing an alkaline solvent, thereby increasing the interfacial action among the h-BN nanosheets and being more beneficial to the stripping of the h-BN.

(2) The h-BN is of a laminated structure, but most of the h-BN is stacked and aggregated together, the force applied in the mechanical ball milling process is mainly shear force and impact force, the cross section size and the plane size of the boron nitride are reduced under the combined action of the two mechanical external forces, but the specific surface area of the h-BN is increased in the process of reducing the layer number, the h-BN is in a thermodynamic unsteady state, the van der Waals force between layers is enhanced, the polarity between B-N atoms between the layers is enhanced, and secondary aggregation is easy to occur.

(3) In the traditional process of mechanically milling boron nitride, the phenomenon that grinding balls impact raw material particles exists, and severe shearing action easily causes structural defects in the surface of the boron nitride, so that the oxidation resistance, the chemical corrosion resistance and the like of a ball-milling product are weakened.

(4) Compared with the traditional liquid phase stripping technology, the method has the advantages of less organic solvent consumption, environmental protection, simple operation, easy control of conditions, low sensitivity to environment, low energy consumption and low production cost, and is beneficial to industrial production and application.

(5) The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material has high heat-conducting property and excellent insulating property and mechanical property.

Drawings

Fig. 1 is a scanning electron microscope image of the PEG intercalated BN nanosheets obtained in example 8, where a is h-BN that was not subjected to ball milling intercalation, and b is the PEG intercalated BN nanosheets, and the scale bars in the image are 2 μm.

Detailed Description

The invention is further described below with reference to the figures and specific examples, without limiting the scope of the invention.

Example 1

The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following components in parts by weight: 100g of PPG resin, 22.52g of MDI, 20g of PEG intercalation BN nano-sheet (h-BN particle size is 6 mu m, and the relative molecular mass of PEG is 6000g/mol), and 0.5g of dispersant CTAB.

Example 2

The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following components in parts by weight: 100g of PPG resin, 22.52g of MDI, 20g of PEG intercalation BN nano-sheet (h-BN particle size is 12 mu m, and the relative molecular mass of PEG is 10000g/mol), and 0.5g of dispersant CTAB.

Example 3

The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following components in parts by weight: 100g of PPG resin, 22.52g of MDI, 20g of PEG intercalation modified BN nano-sheet (h-BN particle size is 16 mu m, and the relative molecular mass of PEG is 10000g/mol), and 0.5g of dispersant CTAB.

Example 4

The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following components in parts by weight: 100g of PPG resin, 22.52g of MDI, 20g of PEG intercalation modified BN nano-sheet (h-BN particle size is 6 mu m, and the relative molecular mass of PEG is 10000g/mol), and 0.5g of dispersant PVP.

Example 5

The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following components in parts by weight: 100g of PPG resin, 22.52g of MDI, 20g of PEG intercalation modified BN nano-sheet (h-BN particle size 6 μm:16 μm ═ 1:1, PEG relative molecular mass is 20000g/mol), 0.5g of dispersant CTAB.

Example 6

The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following components in parts by weight: 100g of PPG resin, 22g of MDI, 10g of PEG intercalation modified BN nanosheets (h-BN particle size 6 μm:12 μm ═ 1:1, PEG relative molecular mass 10000g/mol:20000g/mol ═ 2:1), 0.4g of dispersant PVP.

Example 7

The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following components in parts by weight: 100g of PPG resin, 23g of MDI, 25g of PEG intercalation modified BN nanosheet (h-BN particle size 12 μm, PEG relative molecular mass 10000g/mol:20000g/mol ═ 2:1), 0.6g of dispersant CTAB.

Example 8

The preparation method of the PEG ball-milling intercalated h-BN modified polyurethane heat-conducting composite material of embodiments 1-5 comprises the following specific steps:

(1) putting 48gh-BN and 16g of intercalator PEG into a ball milling tank, adding 0.2g of ball milling auxiliary agent, 100mL of absolute ethyl alcohol, 100mL of water and 5mL of 0.5mol/L NaOH solution, carrying out ball milling, adding 330g of zirconia ball milling beads (30 wt% of zirconia with the particle size of 12-15mm, 50 wt% of zirconia with the particle size of 8-10mm and 20 wt% of zirconia with the particle size of 2 mm), carrying out ball milling at the rotating speed of 360rpm for 20h, carrying out ball milling alternately every 1h to obtain a mixture, and drying the mixture to obtain PEG intercalated BN nanosheets;

(2) according to the formulas in the embodiments 1-5, respectively, accurately weighing corresponding PPG, PEG intercalated BN nanosheets and dispersing agents by an electronic balance, primarily stirring and dispersing for 2-3min, then carrying out ultrasonic treatment, wherein the ultrasonic treatment temperature is 45 ℃, the ultrasonic treatment power is 2000W, after 30min of treatment, placing the treated;

(3) placing the prepolymer in a closed reaction container (an experimental device is set up, a four-mouth flask is fixed in a heat collection type constant-temperature heating magnetic stirrer, a middle port is connected with the stirrer, a left port is sealed by a rubber plug, a right port is connected with a circulating water type multipurpose vacuum pump, a front port is a feeding port and is sealed by the rubber plug), carrying out heating reaction at 70 ℃ under the condition that the stirring speed is 0.3r/s, slowly adding MDI (diphenyl diisocyanate) for in-situ polymerization and simultaneously vacuumizing (the vacuum degree is 3000Pa), and reacting for 1h to obtain a polyurethane precursor; and after the reaction is finished, pouring the polyurethane precursor into a mold preheated to 100 ℃, then placing the mold into an electric heating constant-temperature air blast drying oven for heating and curing, setting the temperature to be 100 ℃, and taking out a cured sample after drying for 360min to obtain the PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material.

Observing the PEG intercalated BN nano-sheet obtained in the step (1) by a scanning electron microscope, wherein an SEM picture is shown in figure 1, wherein a is h-BN without ball milling intercalation, and b is the PEG intercalated BN nano-sheet, as can be seen from figure 1, comparing the h-BN without ball milling intercalation in the figure a with the h-BN without ball milling intercalation in the figure b, the sheet layer of the h-BN is thinned, so that the BN nano-sheet is formed, and the PEG can effectively intercalate and strip the BN in the ball milling process.

Example 9

The preparation method of the PEG ball-milling intercalated h-BN modified polyurethane heat-conducting composite material of embodiments 6 to 7 comprises the following specific steps:

(1) putting 48gh-BN and 16g of intercalator PEG into a ball milling tank, adding 0.2g of ball milling auxiliary agent, 100mL of absolute ethyl alcohol, 100mL of water and 5mL of 0.3mol/L NaOH solution, carrying out ball milling, adding 330g of zirconia ball milling beads (30 wt% of zirconia with the particle size of 12-15mm, 50 wt% of zirconia with the particle size of 8-10mm and 20 wt% of zirconia with the particle size of 2 mm), carrying out ball milling at the rotating speed of 320rpm for 24h, carrying out ball milling alternately every 1h to obtain a mixture, and drying the mixture to obtain PEG intercalated BN nanosheets;

(2) according to the formulas in the embodiments 6-7, respectively, accurately weighing corresponding PPG, PEG intercalated BN nanosheets and dispersing agents by an electronic balance, primarily stirring and dispersing for 5-10min, then carrying out ultrasonic treatment, wherein the ultrasonic treatment temperature is 55 ℃, the ultrasonic treatment power is 4000W, after 30min of treatment, placing the treated;

Comparative example 1

The PEG ball-milling intercalation h-BN modified polyurethane heat-conducting composite material comprises the following components in parts by weight: 100g of PPG resin, 22.52g of MDI, 10g of PEG intercalation BN nano-sheet (h-BN particle size is 6 mu m, and the relative molecular mass of PEG is 10000g/mol), and 0g of dispersant CTAB.

The composite material of comparative example 1 was prepared in the same manner as in example 8.

The performance data for the composites prepared in examples 1-7 and comparative example 1 are shown in Table 1.

TABLE 1 Performance data for composites of examples 1-7 and comparative example 1

Claims

1. a preparation method of polyethylene glycol ball milling intercalation hexagonal boron nitride modified polyurethane thermally conductive composite material, is characterized in that, comprises the steps:

(1) Put hexagonal boron nitride and intercalating agent polyethylene glycol into a ball mill tank, add ball milling aid, solvent, water and sodium hydroxide solution to form materials, carry out ball milling, obtain a mixture after ball milling, and dry the mixture , namely to obtain polyethylene glycol intercalated boron nitride nanosheets; the mass ratio of the hexagonal boron nitride and polyethylene glycol is (15-50): (15-18); the ball milling aid is benzoic acid benzyl ester;

(2) after preliminary stirring and dispersing the polyether polyol, polyethylene glycol intercalated boron nitride nanosheets, and dispersant, ultrasonic treatment is carried out, and then the prepolymer is obtained by drying; the polyether polyol, polyethylene glycol The mass ratio of alcohol-intercalated boron nitride nanosheets is 20:(1-5);

(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; heating and curing the polyurethane precursor and finally obtaining a polymer Glycol ball mill intercalated hexagonal boron nitride modified polyurethane thermally conductive composites.

2. the preparation method of a kind of polyethylene glycol ball milling intercalation hexagonal boron nitride modified polyurethane thermal conductive composite material according to claim 1, is characterized in that, solvent described in step (1) is dehydrated alcohol; Hydrogen The concentration of sodium oxide solution is 0.2mol/L～0.5mol/L; the particle size of the hexagonal boron nitride is one or more of 6 μm, 12 μm, and 16 μm; the relative molecular mass of the polyethylene glycol is 6000g/ mol, one or more of 10000g/mol and 20000g/mol.

3. the preparation method of a kind of polyethylene glycol ball milling intercalation hexagonal boron nitride modified polyurethane thermally conductive composite material according to claim 1, is characterized in that, described in step (1), hexagonal boron nitride, ball milling aid The mass ratio of agent, solvent, water and sodium hydroxide is (15-50):(0.1-0.5):(70-85):100:(0.05-0.1).

4. the preparation method of a kind of polyethylene glycol ball milling intercalation hexagonal boron nitride modified polyurethane thermally conductive composite material according to claim 1, it is characterized in that, in the process of described ball milling, use zirconia ball mill beads, described The particle size of the zirconia ball mill beads is 2mm to 15mm, and the mass ratio of the material to the zirconia ball mill beads is 1:(1-1.5); 1h forward and reverse ball milling alternately.

5. the preparation method of a kind of polyethylene glycol ball milling intercalation hexagonal boron nitride modified polyurethane thermally conductive composite material according to claim 1, is characterized in that, the dispersant described in step (2) is hexadecyl Ammonium bromide or polyvinylpyrrolidone.

6. the preparation method of a kind of polyethylene glycol ball milling intercalation hexagonal boron nitride modified polyurethane thermal conductive composite material according to claim 1, is characterized in that, in step (2), polyethylene glycol intercalation boron nitride The mass ratio of nanosheet and dispersant is (5-25):(0.3-0.6).

7. the preparation method of a kind of polyethylene glycol ball milling intercalation hexagonal boron nitride 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; 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 polyethylene glycol ball mill intercalation hexagonal boron nitride modified polyurethane thermally conductive composite material according to claim 1, is characterized in that, the diisocyanate described in step (3) is 4,4' -Diphenylmethylmethane diisocyanate; the mass ratio of polyether polyol and diisocyanate in the prepolymer is 100:(20-23).

9. the preparation method of a kind of polyethylene glycol ball milling intercalation hexagonal boron nitride modified polyurethane thermal conductive composite material according to claim 1, is characterized in that, in step (3), the vacuum degree of evacuation 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℃, 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 polyethylene glycol ball mill intercalated hexagonal boron nitride modified polyurethane thermally conductive composite material prepared according to the preparation method of any one of claims 1 to 9 .