阅读说明：本技术 一种阻燃复合材料及其制备方法 (Flame-retardant composite material and preparation method thereof ) 是由 刘志启 郭凡 李娜 李丽娟 姬连敏 宋雪雪 聂锋 曾忠民 时东 宋福根 于 2019-11-18 设计创作，主要内容包括：本发明公开了一种阻燃复合材料及其制备方法。该阻燃复合材料的制备方法包括步骤：将可溶性二价镁盐加入氧化石墨烯溶液中,得到混合溶液；将碱加入上述混合溶液,反应得到混合料浆；固液分离混合浆料,在固相中得到氢氧化镁/氧化石墨烯杂化材料；将氢氧化镁/氧化石墨烯杂化材料加入聚丙烯中,制得阻燃复合材料。本发明提供的阻燃复合材料,包括互相混合的氢氧化镁/氧化石墨烯杂化材料和聚丙烯,阻燃复合材料兼具优异的导热性能和阻燃性能。同时,本发明提供的阻燃复合材料的制备方法简单高效、成本低廉,可很好地在工业生产中应用。(The invention discloses a flame-retardant composite material and a preparation method thereof. The preparation method of the flame-retardant composite material comprises the following steps: adding a soluble divalent magnesium salt into a graphene oxide solution to obtain a mixed solution; adding alkali into the mixed solution, and reacting to obtain mixed slurry; solid-liquid separation of the mixed slurry to obtain a magnesium hydroxide/graphene oxide hybrid material in a solid phase; and adding the magnesium hydroxide/graphene oxide hybrid material into polypropylene to prepare the flame-retardant composite material. The flame-retardant composite material provided by the invention comprises the magnesium hydroxide/graphene oxide hybrid material and polypropylene which are mixed with each other, and the flame-retardant composite material has excellent heat-conducting property and flame-retardant property. Meanwhile, the preparation method of the flame-retardant composite material provided by the invention is simple, efficient and low in cost, and can be well applied to industrial production.)

1. The flame-retardant composite material is characterized by comprising a magnesium hydroxide/graphene oxide hybrid material and polypropylene which are mixed with each other.

2. The flame retardant composite material according to claim 1, wherein the mass fraction of graphene oxide in the magnesium hydroxide/graphene oxide hybrid material is 0.1-10%.

3. The flame-retardant composite material according to claim 1 or 2, wherein the mass fraction of the magnesium hydroxide/graphene oxide hybrid material in the flame-retardant composite material is 10-50%.

4. A method for preparing a flame retardant composite material according to any one of claims 1 to 3, comprising the steps of:

s1, adding a soluble divalent magnesium salt into the graphene oxide solution to obtain a mixed solution;

s2, adding alkali into the mixed solution, and reacting to obtain mixed slurry;

s3, separating solid from liquid to obtain mixed slurry, and obtaining the magnesium hydroxide/graphene oxide hybrid material in the solid phase;

s4, adding the magnesium hydroxide/graphene oxide hybrid material into polypropylene to obtain the flame-retardant composite material.

5. The method according to claim 4, wherein the reaction time of step S2 is 0.5-1 h.

6. The method according to claim 4 or 5, wherein the mixed slurry obtained in step S2 is further subjected to hydrothermal reaction at a reaction temperature of 100 to 200 ℃ for a reaction time of 0.5 to 48 hours.

7. The method according to claim 4, wherein the soluble divalent magnesium salt is magnesium chloride, magnesium nitrate, magnesium sulfate, or a hydrate thereof.

8. The method according to claim 4, wherein the concentration of magnesium ions in the mixed solution is 0.5 to 2.0 mol/L.

9. The method according to claim 4 or 8, wherein the base is a solid base or an alkaline solution.

10. The preparation method of claim 9, wherein the concentration of the alkali liquor is 1-4 mol/L.

Technical Field

The invention belongs to the technical field of flame-retardant materials, and particularly relates to a flame-retardant composite material and a preparation method thereof.

Background

Magnesium hydroxide is the most common inorganic flame retardant, the decomposition temperature is about 340 ℃, and magnesium oxide and water generated after decomposition belong to non-toxic and harmless substances and environment-friendly flame retardants, so the application prospect is very wide. However, magnesium hydroxide has the disadvantages of easy agglomeration and low flame-retardant efficiency, and the addition amount of the magnesium hydroxide in a polymer is very large, and the polymer can reach the flame-retardant level when the addition amount is usually more than 50%. However, such a large amount of addition has greatly affected the mechanical properties of the polymer, and severely limits the application of magnesium hydroxide in particular fields. In order to reduce the amount of magnesium hydroxide added to a polymer, improvement of magnesium hydroxide is required.

There are many methods for improving magnesium hydroxide, including making the magnesium hydroxide flame retardant additive into nanometer size, considering the synergistic effect of magnesium hydroxide flame retardant and other materials, and surface treatment and modification of magnesium hydroxide flame retardant to reduce the addition of magnesium hydroxide flame retardant in the polymer. Research shows that when the nano-scale magnesium hydroxide is used as a flame retardant of a high polymer material, the required filling amount is small, the nano-scale magnesium hydroxide has good compatibility with the high polymer material, and the nano-scale magnesium hydroxide also has a certain enhancing effect on the mechanical property of the high polymer material.

Among inorganic flame retardants, carbon nanomaterials are also a commonly used flame retardant, and graphene has attracted attention of researchers due to its excellent mechanical properties and synergistic flame retardant properties. The two-dimensional structure of the graphene can play a role of a protective layer, the graphitization degree of the residual carbon layer can be greatly improved when the graphene is added into a high polymer material, the thermal stability of the residual carbon layer is improved, and the flame retardant effect is achieved.

Chinese patent application (publication No. CN 106191901A) discloses a preparation method of a magnesium hydroxide/graphene composite material with a high specific surface area, which takes bischofite as a magnesium source, then adds graphene for ultrasonic dispersion, adjusts the pH value of the solution, takes a graphite plate as a cathode, and takes metal or alloy material thereof as an anode to electrolyze magnesium chloride/graphene electrolyte to obtain a product. The method has complex experimental process, adopts an electrolytic method to prepare the composite material, has higher production cost and higher difficulty in realizing industrial production. Chinese patent application (CN106430172A) discloses a preparation method of a magnesium hydroxide/graphene oxide composite material, which uses a supergravity method to prepare the magnesium hydroxide/graphene oxide composite material by taking graphene oxide dispersion liquid, magnesium salt solution and alkali solution as raw materials. But the invention has to use special supergravity equipment, and the production cost is high.

Disclosure of Invention

In order to solve the problems that the preparation cost of the magnesium hydroxide/graphene oxide composite material in the prior art is high, and the prepared material cannot have excellent heat conduction and flame retardant properties, the invention adopts a simple and low-cost preparation method to prepare the flame retardant composite material with excellent heat conduction property and excellent flame retardant property.

In order to achieve the purpose of the invention, the invention adopts the following technical scheme:

a flame retardant composite comprising a magnesium hydroxide/graphene oxide hybrid material and polypropylene intermixed.

Preferably, in the magnesium hydroxide/graphene oxide hybrid material, the mass fraction of graphene oxide is 0.1-10%.

Preferably, in the flame-retardant composite material, the mass fraction of the magnesium hydroxide/graphene oxide hybrid material is 10-50%.

The invention also provides a preparation method of the flame-retardant composite material, which comprises the following steps:

s1, adding a soluble divalent magnesium salt into the graphene oxide solution to obtain a mixed solution;

s2, adding alkali into the mixed solution, and reacting to obtain mixed slurry;

s3, separating solid from liquid to obtain mixed slurry, and obtaining the magnesium hydroxide/graphene oxide hybrid material in the solid phase;

s4, adding the magnesium hydroxide/graphene oxide hybrid material into polypropylene to obtain the flame-retardant composite material.

Preferably, the reaction time of step S2 is 0.5-1 h.

Further preferably, the mixed slurry in step S2 is subjected to hydrothermal reaction at a reaction temperature of 100 to 200 ℃ for 0.5 to 48 hours.

Preferably, the soluble divalent magnesium salt is magnesium chloride, magnesium nitrate, magnesium sulfate, or a hydrate thereof.

Further preferably, the concentration of magnesium ions in the mixed solution is 0.5-2.0 mol/L.

Preferably, the base is a solid base or a lye base.

Further preferably, the concentration of the alkali liquor is 1-4 mol/L.

The flame-retardant composite material provided by the invention comprises the magnesium hydroxide/graphene oxide hybrid material and polypropylene which are mixed with each other, and has excellent heat-conducting property and flame-retardant property. Meanwhile, the preparation method of the flame-retardant composite material provided by the invention is simple, efficient and low in cost, and can be well applied to industrial production.

Drawings

The above and other aspects, features and advantages of embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

fig. 1 is an XRD pattern of graphene oxide of example 1 of the present invention;

fig. 2 is an SEM image of graphene oxide of example 1;

FIG. 3 is an XRD pattern of the product obtained in example 1;

FIGS. 4 and 5 are TEM images of the product obtained in example 1 at different magnifications;

FIGS. 6 and 7 are SEM images of the magnesium hydroxide/graphene oxide hybrid material in example 1 at different magnifications;

FIG. 8 is a graph of heat release rate for PP materials and the flame retardant composite of examples 1-3;

FIG. 9 is a graph showing the total heat release of PP material and the flame retardant composite of examples 1 to 3;

FIG. 10 is a graph of smoke release rate for PP material and the flame retardant composite of examples 1-3;

FIG. 11 is a graph showing the total smoke emission of PP material and the flame retardant composite of examples 1 to 3;

FIG. 12 is an XRD pattern of the product obtained in example 5;

FIG. 13 is an SEM photograph of the product obtained in example 5;

FIG. 14 is an XRD pattern of the product obtained in example 6;

FIGS. 15 and 16 are SEM images of the product obtained in example 6 at different magnifications.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application to thereby enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated.

The inventor of the invention provides a flame-retardant composite material with excellent heat conduction performance and flame retardance performance based on the problems that a magnesium hydroxide/graphene oxide composite material in the prior art cannot have excellent heat conduction performance and flame retardance performance, is high in preparation cost and is complex in preparation method, and provides a preparation method of the flame-retardant composite material.

The two-dimensional structure of the graphene can play a role of a protective layer, and the graphitization degree of the residual carbon layer can be greatly improved by adding the graphene into a high polymer material, so that the thermal stability of the residual carbon layer is improved, and the flame retardant effect is achieved. The surface of the graphene oxide contains a large number of active groups, and the organic-inorganic hybrid composite material can be prepared through non-covalent interaction, wherein the preparation mechanism of the flame-retardant composite material is as follows: firstly, stripping graphite oxide into graphene oxide by a chemical method; then, adsorbing metal cations on the surface of the graphene oxide; then, adding a precipitator to enable the metal ions adsorbed on the surface to be self-combined into a metal oxide/graphene oxide composite material; and finally, adding the composite material into a high polymer material to obtain the high polymer flame-retardant composite material.

The preparation method of the flame-retardant composite material provided by the invention comprises the following steps:

s1, adding a soluble divalent magnesium salt into the graphene oxide solution to obtain a mixed solution;

the soluble divalent magnesium salt is selected from various kinds, and may be magnesium chloride, magnesium nitrate, magnesium sulfate or their hydrates.

The Graphene Oxide (GO) is prepared from natural crystalline flake graphene by a chemical oxidation method.

The magnesium ion concentration is low, which is beneficial to the dispersion of magnesium hydroxide, but the output efficiency of the product is low; the magnesium ion concentration is high, the yield is high, but the agglomeration of magnesium hydroxide is serious. Therefore, in order to integrate the output efficiency and the agglomeration problem, the concentration of magnesium ions in the mixed solution is preferably 0.5-2.0 mol/L.

And S2, adding alkali into the mixed solution, and reacting to obtain mixed slurry.

The alkali can be selected from solid alkali or alkali liquor, and when the alkali liquor is used, the concentration of the alkali liquor is preferably 1-4 mol/L.

The specific method comprises the following steps: firstly, reacting alkali and magnesium salt for a period of time to generate a magnesium hydroxide crystal nucleus in a reaction system, wherein the reaction time of the nucleation is preferably 0.5-1 h; and then preferably transferring the mixed system of the primary reaction into a high-pressure reaction kettle for hydrothermal reaction, wherein the preferred temperature of the hydrothermal reaction is 100-200 ℃, and the preferred time of the hydrothermal reaction is 0.5-48 h. The hydrothermal reaction is carried out in a closed reaction kettle, so that hexagonal flaky magnesium hydroxide can be formed, and the magnesium hydroxide with the morphology has a good flame retardant effect in application.

S3, separating solid from liquid, mixing the slurry, and obtaining the magnesium hydroxide/graphene oxide hybrid material in the solid phase.

There are various solid-liquid separation methods, and the present invention does not limit the specific selection thereof, and may employ suction filtration, drying, centrifugal separation, and the like.

S4, adding the magnesium hydroxide/graphene oxide hybrid material into polypropylene to obtain the flame-retardant composite material.

The embodiment of the invention provides a flame-retardant composite material which comprises a magnesium hydroxide/graphene oxide hybrid material and polypropylene which are mixed with each other.

In the magnesium hydroxide/graphene oxide hybrid material, the mass fraction of the graphene oxide is 0.1-10%.

In the flame-retardant composite material, the mass fraction of the magnesium hydroxide/graphene oxide hybrid material is preferably 10-50%.

It is worth to be noted that polypropylene (PP) contains a large amount of methyl groups, which results in a limited oxygen index (LOI value) of only 17.4%, and is a flammable polymer material. In addition, a large amount of black smoke and toxic gas are generated in the combustion process of PP, and the molten drops are dripped, so that great threat is brought to the life and property safety of people, and potential safety hazards exist when the PP material is used alone. Compared with a pure PP material, the flame-retardant composite material disclosed by the invention has higher thermal conductivity and lower smoke release amount, the smoke release rate and the heat release rate are both obviously reduced, and the excellent heat conduction and flame retardance properties enable the flame-retardant composite material to have great application value.

According to the invention, magnesium hydroxide is attached to the surface of graphene oxide by adopting a simple and efficient non-covalent effect to form a magnesium hydroxide/graphene oxide hybrid material, and then the hybrid material is added into polypropylene. The particle size of the magnesium hydroxide/graphene oxide hybrid material is in a nanometer scale and is about 50nm, so that the magnesium hydroxide/graphene oxide hybrid material has a good nanometer effect, and the thermal conductivity of the graphene oxide is good, so that the obtained flame-retardant composite material has high thermal conductivity and high flame-retardant performance, and particularly, the dispersion performance of the material is greatly improved by adding the graphene oxide.

The above flame-retardant composite material and the method for preparing the same according to the present invention will be described below with reference to specific examples, and it will be understood by those skilled in the art that the following examples are only specific examples of the above flame-retardant composite material and the method for preparing the same according to the present invention, and are not intended to limit the entirety thereof.