Graphene grafted flame retardant modified polyurethane composite material and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane, and discloses a graphene grafted flame retardant modified polyurethane composite material, which is characterized in that epoxidized graphene and p-hydroxybenzaldehyde are subjected to a ring-opening reaction, aldehyde group modified graphene and 2-aminobenzimidazole are subjected to a Schiff base reaction, and Schiff base grafted graphene and phosphoric acid-1, 2, 3-triazole are subjected to a reaction to obtain the graphene grafted flame retardant modified polyurethane composite material. The graphene grafted flame retardant is obtained by carrying out addition reaction on 1, 2-phenylene diester, graphene is well dispersed in a matrix, a uniform and compact carbon layer is formed on the surface of the matrix, and in the combustion process of polyurethane, a phosphorus structure is decomposed to generate more acidic substances such as phosphoric acid, so that dehydration and carbonization of the matrix are promoted, and formation of the carbon layer on the matrix is promoted; according to the flame-retardant polyurethane matrix disclosed by the invention, the phosphorus-containing heterocyclic ring and the benzimidazole are added, the combustion chain reaction is quenched, the nitrogen element can generate non-combustible gas in the combustion process to dilute the concentration of oxygen around the matrix, and a nitrogen-phosphorus synergistic flame-retardant effect is generated between the phosphorus-containing heterocyclic ring and the benzimidazole, so that the obtained polyurethane matrix has excellent flame-retardant property.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane, in particular to a graphene-grafted flame retardant modified polyurethane composite material and a preparation method thereof. Background Art

[0002] Polyurethane has excellent flexibility, elasticity and damping capacity, and is oil-resistant and heat-resistant. It is one of the most widely used polymer materials in the world and is often used in insulation boards, foams, adhesives and coatings. As a thermosetting plastic, polyurethane material is easy to burn in the air and easily produces a large amount of smoke when burning, which greatly limits the scope of use of polyurethane. Flame-retardant modification of polyurethane has important practical significance and value.

[0003] Chinese patent CN110655634A discloses a highly flame-retardant polyurethane foam composition and a highly flame-retardant polyurethane foam prepared therefrom. Graphene aerogel is modified by using at least one of nitride, phosphide and bromide, and the modified graphene aerogel filler is added to polyurethane. The prepared polyurethane has excellent flame retardant properties, and graphene has excellent mechanical properties, flame retardant properties and thermal stability. However, the flame retardant properties of single inorganic flame retardant graphene are poor. It is difficult to improve the shortcomings of poor compatibility and dispersibility of graphene by adding organic flame retardants by a mixing method, and the flame retardant effect is general. Common organic flame retardants include phosphorus flame retardants, nitrogen flame retardants, etc. These flame retardants are green and environmentally friendly, and have good flame retardant effects. Graphene is grafted onto organic flame retardants, and the flame retardant obtained has the characteristics of good effect and long duration, and can well improve the flame retardant properties of the polyurethane matrix.

[0004] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a graphene-grafted flame retardant modified polyurethane composite material and a preparation method thereof, which solves the problem of poor flame retardant effect of polyurethane.

[0005] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a graphene-grafted flame retardant-modified polyurethane composite material, the graphene-grafted flame retardant-modified polyurethane composite material and the preparation method are as follows: (1) Add N,N-dimethylformamide solvent, graphene oxide, epichlorohydrin and potassium iodide to the reactor in sequence, stir and mix evenly, heat and reflux, react at 90-110° C. for 12-18 hours, and after the reaction is completed, wash with ethanol and deionized water, and dry to obtain epoxy graphene; (2) adding N,N-dimethylformamide solvent, epoxidized graphene and p-hydroxybenzaldehyde to the reactor in sequence, heating under reflux in a nitrogen atmosphere to react, and after the reaction is completed, filtering, washing with ethanol and deionized water, and drying to obtain aldehyde-modified graphene; (3) adding methanol solvent, aldehyde-modified graphene, 2-aminobenzimidazole and glacial acetic acid to the reactor in sequence, stirring and mixing evenly, heating under reflux to react, filtering after the reaction is completed, washing with methanol, and drying to obtain Schiff base grafted graphene; (4) Add 1,4-dioxane solvent, Schiff base grafted graphene and 1,2-phenylene diester phosphate to the reactor in sequence, stir and mix evenly, pre-react at 20-40° C. for 1-3 h, heat and heat, react at 60-80° C. for 3-6 h, and after the reaction is completed, cool, filter, wash with acetone, and dry to obtain a graphene grafted flame retardant; (5) Adding polyurethane, graphene grafted flame retardant and defoaming agent polysiloxane into a twin-screw extruder in sequence, melt blending at 170-190° C. for 8-15 min, extruding after mixing evenly, and hot pressing in a flat plate vulcanizer at 140-160° C. for 6-12 min under a pressure of 8-12 MPa to obtain a graphene grafted flame retardant modified polyurethane composite material.

[0006] Preferably, in step (1), the mass ratio of N,N-dimethylformamide, graphene oxide, epichlorohydrin and potassium iodide is 15000-30000:10:2000-2500:4000-5000.

[0007] Preferably, in step (2), the mass ratio of ethanol, epoxidized graphene and p-hydroxybenzaldehyde is 6000-12000:100:80-150.

[0008] Preferably, the reaction temperature in step (2) is 75-105° C., and the reaction time is 8-15 h.

[0009] Preferably, in step (3), the mass ratio of methanol, aldehyde-modified graphene, 2-aminobenzimidazole and glacial acetic acid is 1500-3500:100:60-120:1-3.

[0010] Preferably, the reaction temperature in step (3) is 50-70° C., and the reaction time is 6-12 h.

[0011] Preferably, in step (4), the mass ratio of 1,4-dioxane, Schiff base grafted graphene and 1,2-phenylene phosphate is 2000-4000:100:55-85.

[0012] Preferably, in step (5), the mass ratio of polyurethane, graphene grafted flame retardant and polysiloxane is 100:0.5-6:0.2-2.

[0013] 3. Beneficial technical effects Compared with the prior art, the present invention has the following beneficial technical effects: The invention discloses a graphene grafted flame retardant modified polyurethane composite material. Graphene oxide is modified by epichlorohydrin to obtain epoxidized graphene. In an N,N-dimethylformamide solvent, epoxy groups on the epoxidized graphene and hydroxyl groups on p-hydroxybenzaldehyde undergo a ring-opening reaction to obtain aldehyde-modified graphene. The aldehyde groups on the aldehyde-modified graphene and amino groups on 2-aminobenzimidazole undergo a Schiff base reaction to obtain Schiff base-grafted graphene. The Schiff base on the Schiff base-grafted graphene and the PH bond on 1,2-phenylene diester phosphate undergo an addition reaction to obtain a graphene grafted flame retardant. The obtained flame retardant is added to polyurethane to prepare a graphene grafted flame retardant modified polyurethane composite material.

[0014] The invention discloses a graphene-grafted flame retardant modified polyurethane composite material. The graphene has excellent flame retardant performance. The graphene is grafted onto the nitrogen-phosphorus flame retardant, effectively avoiding the agglomeration of nanographene, being well dispersed in a matrix, and forming a uniform and dense carbon layer on the surface of the matrix. The phosphorus-containing heterocycle decomposes the phosphorus structure to generate more acidic substances such as phosphoric acid during the combustion process of the polyurethane, promoting the dehydration and carbonization of the matrix, promoting the formation of a carbon layer on the matrix to a great extent, improving the carbonization efficiency of the matrix, generating PO· free radicals, and being able to quench the combustion chain reaction and prevent the combustion reaction from proceeding. The nitrogen element will generate non-flammable nitrogen, ammonia and other gases during the combustion process, diluting the oxygen concentration around the matrix and reducing the elements required for the combustion reaction. The phosphorus-containing heterocycle and the benzimidazole generate a nitrogen-phosphorus synergistic flame retardant effect, and the obtained polyurethane matrix has excellent flame retardant performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the synthesis of Schiff base grafted graphene.

[0016] Figure 2 Schematic diagram of the synthesis of graphene grafted flame retardant.

[0017] Figure 3 This is a flame retardant performance test chart. DETAILED DESCRIPTION

[0018] To achieve the above object, the present invention provides the following specific implementation methods and examples: A method for preparing a graphene-grafted flame retardant modified polyurethane composite material is as follows: (1) Add N,N-dimethylformamide solvent, graphene oxide, epichlorohydrin and potassium iodide in a mass ratio of 15000-30000:10:2000-2500:4000-5000 to a reactor in sequence, stir and mix evenly, heat to reflux, react at 90-110° C. for 12-18 hours, and after the reaction is completed, wash with ethanol and deionized water, and dry to obtain epoxy graphene; (2) Add N,N-dimethylformamide solvent, epoxidized graphene and p-hydroxybenzaldehyde in a mass ratio of 6000-12000:100:80-150 to the reactor in sequence, heat under reflux in a nitrogen atmosphere, react at 75-105° C. for 8-15 hours, and after the reaction is completed, filter, wash with ethanol and deionized water, and dry to obtain aldehyde-modified graphene; (3) adding methanol solvent, aldehyde-modified graphene, 2-aminobenzimidazole and glacial acetic acid in a mass ratio of 1500-3500:100:60-120:1-3 into the reactor in sequence, stirring and mixing evenly, heating under reflux, reacting at 50-70°C for 6-12h, filtering after the reaction, washing with methanol, and drying to obtain Schiff base grafted graphene; (4) Adding 1,4-dioxane solvent, Schiff base grafted graphene and 1,2-phenylene diester in a mass ratio of 2000-4000:100:55-85 to the reactor in sequence, stirring and mixing evenly, pre-reacting at 20-40° C. for 1-3 h, heating and heating, reacting at 60-80° C. for 3-6 h, cooling after the reaction, filtering, washing with acetone, and drying to obtain a graphene grafted flame retardant; (5) Adding polyurethane, graphene grafted flame retardant and polysiloxane in a mass ratio of 100:0.5-6:0.2-2 into a twin-screw extruder in sequence, melt blending at 170-190°C for 8-15 min, extruding after mixing evenly, and hot pressing in a flat plate vulcanizer at 140-160°C for 6-12 min under a pressure of 8-12 MPa to obtain a graphene grafted flame retardant modified polyurethane composite material.

[0019] Example 1

[0020] (1) Add 800 ml of N,N-dimethylformamide solvent, 0.5 g of graphene oxide, 100 g of epichlorohydrin and 200 g of potassium iodide to the reactor in sequence, stir and mix evenly, heat to reflux, react at 90° C. for 12 h, and after the reaction is completed, wash with ethanol and deionized water, and dry to obtain epoxy graphene; (2) Add 320 ml of N,N-dimethylformamide solvent, 5 g of epoxidized graphene and 4 g of p-hydroxybenzaldehyde to the reactor in sequence, heat and reflux in a nitrogen atmosphere, react at 75 °C for 8 h, and after the reaction is completed, filter, wash with ethanol and deionized water, and dry to obtain aldehyde-modified graphene; (3) Add 100 ml of methanol solvent, 5 g of aldehyde-modified graphene, 3 g of 2-aminobenzimidazole and 0.05 g of glacial acetic acid to the reactor in sequence, stir and mix evenly, heat to reflux, react at 50 ° C for 6 h, filter after the reaction, wash with methanol, and dry to obtain Schiff base grafted graphene; (4) Add 100 ml of 1,4-dioxane solvent, 5 g of Schiff base grafted graphene and 2.75 g of 1,2-phenylene diester phosphate into the reactor in sequence, stir and mix evenly, pre-react at 20° C. for 1 h, heat and heat, react at 60° C. for 3 h, and after the reaction is completed, cool, filter, wash with acetone, and dry to obtain a graphene grafted flame retardant; (5) 100 g of polyurethane, 0.5 g of graphene grafted flame retardant and 0.2 g of polysiloxane were added to a twin-screw extruder in sequence, melt-blended at 170 °C for 8 min, extruded after mixing evenly, and hot-pressed in a flat-plate vulcanizer at 140 °C for 6 min under a pressure of 8 MPa to obtain a graphene grafted flame retardant modified polyurethane composite material.

[0021] Example 2

[0022] (1) Add 950 ml of N,N-dimethylformamide solvent, 0.5 g of graphene oxide, 108 g of epichlorohydrin and 210 g of potassium iodide to the reactor in sequence, stir and mix evenly, heat to reflux, react at 95° C. for 14 h, and after the reaction is completed, wash with ethanol and deionized water, and dry to obtain epoxy graphene; (2) Add 400 ml of N,N-dimethylformamide solvent, 5 g of epoxidized graphene and 5 g of p-hydroxybenzaldehyde to the reactor in sequence, heat and reflux in a nitrogen atmosphere, react at 85 °C for 9 h, and after the reaction is completed, filter, wash with ethanol and deionized water, and dry to obtain aldehyde-modified graphene; (3) Add 120 ml of methanol solvent, 5 g of aldehyde-modified graphene, 3.5 g of 2-aminobenzimidazole and 0.08 g of glacial acetic acid to the reactor in sequence, stir and mix evenly, heat to reflux, react at 55 °C for 8 h, filter after the reaction, wash with methanol, and dry to obtain Schiff base grafted graphene; (4) Add 120 ml of 1,4-dioxane solvent, 5 g of Schiff base grafted graphene and 3 g of 1,2-phenylene phosphate to the reactor in sequence, stir and mix evenly, pre-react at 25° C. for 1.5 h, heat and heat, react at 65° C. for 4 h, and after the reaction is completed, cool, filter, wash with acetone, and dry to obtain a graphene grafted flame retardant; (5) 100 g of polyurethane, 2 g of graphene grafted flame retardant and 0.6 g of polysiloxane were added to a twin-screw extruder in sequence, melt blended at 175 °C for 9 min, extruded after mixing evenly, and hot pressed in a flat-plate vulcanizer at 145 °C for 8 min under a pressure of 9 MPa to obtain a graphene grafted flame retardant modified polyurethane composite material.

[0023] Example 3

[0024] (1) Add 1200 ml of N,N-dimethylformamide solvent, 0.5 g of graphene oxide, 115 g of epichlorohydrin and 225 g of potassium iodide to the reactor in sequence, stir and mix evenly, heat to reflux, react at 100° C. for 15 h, and after the reaction is completed, wash with ethanol and deionized water, and dry to obtain epoxy graphene; (2) Add 480 ml of N,N-dimethylformamide solvent, 5 g of epoxidized graphene and 6 g of p-hydroxybenzaldehyde to the reactor in sequence, heat and reflux in a nitrogen atmosphere, react at 90 °C for 10 h, and after the reaction is completed, filter, wash with ethanol and deionized water, and dry to obtain aldehyde-modified graphene; (3) Add 150 ml of methanol solvent, 5 g of aldehyde-modified graphene, 4.5 g of 2-aminobenzimidazole and 0.1 g of glacial acetic acid to the reactor in sequence, stir and mix them evenly, heat and reflux, react at 60 ° C for 9 h, filter after the reaction, wash with methanol, and dry to obtain Schiff base grafted graphene; (4) Add 140 ml of 1,4-dioxane solvent, 5 g of Schiff base grafted graphene and 3.5 g of 1,2-phenylene diester phosphate into the reactor in sequence, stir and mix evenly, pre-react at 30° C. for 2 h, heat and heat, react at 70° C. for 4 h, and after the reaction is completed, cool, filter, wash with acetone, and dry to obtain a graphene grafted flame retardant; (5) 100 g of polyurethane, 4 g of graphene grafted flame retardant and 1 g of polysiloxane were added to a twin-screw extruder in sequence, melt-blended at 180 °C for 10 min, extruded after mixing evenly, and hot-pressed in a flat-plate vulcanizer at 150 °C for 9 min under a pressure of 10 MPa to obtain a graphene grafted flame retardant modified polyurethane composite material.

[0025] Example 4

[0026] (1) Add 1400 ml of N,N-dimethylformamide solvent, 0.5 g of graphene oxide, 120 g of epichlorohydrin and 240 g of potassium iodide to the reactor in sequence, stir and mix them evenly, heat and reflux, react at 105° C. for 16 h, and after the reaction is completed, wash with ethanol and deionized water, and dry to obtain epoxy graphene; (2) Add 550 ml of N,N-dimethylformamide solvent, 5 g of epoxidized graphene and 7 g of p-hydroxybenzaldehyde to the reactor in sequence, heat and reflux in a nitrogen atmosphere, react at 100 °C for 12 h, and after the reaction is completed, filter, wash with ethanol and deionized water, and dry to obtain aldehyde-modified graphene; (3) Add 200 ml of methanol solvent, 5 g of aldehyde-modified graphene, 5.5 g of 2-aminobenzimidazole and 0.12 g of glacial acetic acid to the reactor in sequence, stir and mix them evenly, heat and reflux, react at 65 ° C for 10 h, filter after the reaction, wash with methanol, and dry to obtain Schiff base grafted graphene; (4) Add 180 ml of 1,4-dioxane solvent, 5 g of Schiff base grafted graphene and 4 g of 1,2-phenylene phosphate to the reactor in sequence, stir and mix evenly, pre-react at 35° C. for 2.5 h, heat and heat, react at 75° C. for 5 h, and after the reaction is completed, cool, filter, wash with acetone, and dry to obtain a graphene grafted flame retardant; (5) 100 g of polyurethane, 5 g of graphene grafted flame retardant and 1.5 g of polysiloxane were added to a twin-screw extruder in sequence, melt-blended at 185 °C for 12 min, mixed evenly and extruded, and hot-pressed in a flat-plate vulcanizer at 155 °C for 10 min under a pressure of 11 MPa to obtain a graphene grafted flame retardant modified polyurethane composite material.

[0027] Example 5

[0028] (1) Add 1550 ml of N,N-dimethylformamide solvent, 0.5 g of graphene oxide, 125 g of epichlorohydrin and 250 g of potassium iodide to the reactor in sequence, stir and mix evenly, heat and reflux, react at 110° C. for 18 h, and after the reaction is completed, wash with ethanol and deionized water, and dry to obtain epoxy graphene; (2) Add 630 ml of N,N-dimethylformamide solvent, 5 g of epoxidized graphene and 7.5 g of p-hydroxybenzaldehyde to the reactor in sequence, heat and reflux in a nitrogen atmosphere, react at 105 °C for 15 h, and after the reaction is completed, filter, wash with ethanol and deionized water, and dry to obtain aldehyde-modified graphene; (3) Add 220 ml of methanol solvent, 5 g of aldehyde-modified graphene, 6 g of 2-aminobenzimidazole and 0.15 g of glacial acetic acid to the reactor in sequence, stir and mix them evenly, heat and reflux, react at 70 ° C for 12 h, filter after the reaction, wash with methanol, and dry to obtain Schiff base grafted graphene; (4) Add 190 ml of 1,4-dioxane solvent, 5 g of Schiff base grafted graphene and 4.25 g of 1,2-phenylene diester phosphate into the reactor in sequence, stir and mix evenly, pre-react at 40° C. for 3 h, heat and heat, react at 80° C. for 6 h, and after the reaction is completed, cool, filter, wash with acetone, and dry to obtain a graphene grafted flame retardant; (5) 100 g of polyurethane, 6 g of graphene grafted flame retardant and 2 g of polysiloxane were added to a twin-screw extruder in sequence, melt-blended at 190 °C for 15 min, extruded after mixing evenly, and hot-pressed in a flat-plate vulcanizer at 160 °C for 12 min under a pressure of 12 MPa to obtain a graphene grafted flame retardant modified polyurethane composite material.

[0029] Comparative Example 1 (1) Add 1200 ml of N,N-dimethylformamide solvent, 0.5 g of graphene oxide, 115 g of epichlorohydrin and 225 g of potassium iodide to the reactor in sequence, stir and mix evenly, heat to reflux, react at 100° C. for 15 h, and after the reaction is completed, wash with ethanol and deionized water, and dry to obtain epoxy graphene; (2) 100 g of polyurethane, 3.5 g of epoxidized graphene and 1.5 g of polysiloxane were added to a twin-screw extruder in sequence, melt-blended at 180 °C for 12 min, mixed evenly and extruded, and hot-pressed in a flat-plate vulcanizer at 150 °C for 9 min under a pressure of 10 MPa to obtain a graphene-modified polyurethane composite material.

[0030] The modified polyurethane composite materials synthesized in the examples and comparative examples were cut into strips of 100 mm×100 mm×3 mm and subjected to limiting oxygen index test on a JF-5 fully automatic oxygen index instrument. Each group of samples was tested three times and the average value was taken.

Claims

1. A method for preparing a graphene-grafted flame retardant modified polyurethane composite material, characterized in that: The preparation method is as follows: (1) Adding graphene oxide, epichlorohydrin and potassium iodide to N,N-dimethylformamide solvent, stirring and mixing evenly, heating under reflux, reacting at 90-110° C. for 12-18 hours, and obtaining epoxidized graphene after the reaction is completed; (2) adding epoxidized graphene and p-hydroxybenzaldehyde to N,N-dimethylformamide solvent, heating under reflux in a nitrogen atmosphere to react, and after the reaction is completed, aldehyde-modified graphene is obtained; (3) adding aldehyde-modified graphene, 2-aminobenzimidazole and glacial acetic acid to a methanol solvent, stirring and mixing them evenly, heating under reflux to react, and obtaining Schiff base-grafted graphene after the reaction is completed; (4) Adding Schiff base grafted graphene and 1,2-phenylene phosphate to 1,4-dioxane solvent, stirring and mixing evenly, pre-reacting at 20-40° C. for 1-3 hours, heating and heating, reacting at 60-80° C. for 3-6 hours, and obtaining a graphene grafted flame retardant after the reaction is completed; (5) Adding polyurethane, graphene grafted flame retardant and defoaming agent polysiloxane into a twin-screw extruder in sequence, melt blending at 170-190° C. for 8-15 min, extruding after mixing evenly, and hot pressing in a flat plate vulcanizer at 140-160° C. for 6-12 min under a pressure of 8-12 MPa to obtain a graphene grafted flame retardant modified polyurethane composite material.

2. The method for preparing a graphene-grafted flame retardant modified polyurethane composite material according to claim 1, characterized in that: In the step (1), the mass ratio of N,N-dimethylformamide, graphene oxide, epichlorohydrin and potassium iodide is 15000-30000:10:2000-2500:4000-5000.

3. The method for preparing a graphene-grafted flame retardant modified polyurethane composite material according to claim 1, characterized in that: In the step (2), the mass ratio of ethanol, epoxidized graphene and p-hydroxybenzaldehyde is 6000-12000:100:80-150.

4. The method for preparing a graphene-grafted flame retardant modified polyurethane composite material according to claim 1, characterized in that: The reaction temperature in step (2) is 75-105° C. and the reaction time is 8-15 h.

5. The method for preparing a graphene-grafted flame retardant modified polyurethane composite material according to claim 1, characterized in that: In the step (3), the mass ratio of methanol, aldehyde-modified graphene, 2-aminobenzimidazole and glacial acetic acid is 1500-3500:100:60-120:1-3.

6. The method for preparing a graphene-grafted flame retardant modified polyurethane composite material according to claim 1, characterized in that: The reaction temperature in step (3) is 50-70° C. and the reaction time is 6-12 h.

7. The method for preparing a graphene-grafted flame retardant modified polyurethane composite material according to claim 1, characterized in that: In the step (4), the mass ratio of 1,4-dioxane, Schiff base grafted graphene and 1,2-phenylene phosphate is 2000-4000:100:55-85.

8. The method for preparing a graphene-grafted flame retardant modified polyurethane composite material according to claim 1, characterized in that: In the step (5), the mass ratio of polyurethane, graphene grafted flame retardant and polysiloxane is 100:0.5-6:0.2-2.

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