Preparation method of waterborne polyurethane / carbon nanotube composite adhesive for fiber bulletproof material

Abstract

The invention discloses a preparation method of a waterborne polyurethane / carbon nanotube composite adhesive for a fiber bulletproof material. The preparation method comprises the following steps: synthesizing a waterborne polyurethane prepolymer under the protection of a nitrogen atmosphere by taking polyisocyanate and polyol as polymeric monomers, dibutyltin dilaurate as a catalyst and 2, 2-bis (hydroxymethyl) propionic acid as a hydrophilic chain extender; the preparation method comprises the following steps: synthesizing waterborne polyurethane containing a maleimide group by taking 4-maleimidophenol as a modified monomer; the waterborne polyurethane / carbon nanotube composite adhesive is prepared through a covalent chemical reaction. According to the preparation method disclosed by the invention, the waterborne polyurethane / carbon nanotube composite adhesive is applied to the surface of the ultra-high molecular weight polyethylene fiber, so that the problems of low friction coefficient, large back bulge and the like when the fiber composite material is used as a bulletproof material are effectively solved while the interface performance of the fiber composite material is improved.

Description

Technical Field

[0001] This invention belongs to the field of modified adhesive technology and is applicable to fiber-reinforced resin-based composite materials. Specifically, it relates to a method for preparing a waterborne polyurethane / carbon nanotube composite adhesive for fiber bulletproof materials. Technical Background

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] In current military warfare, the emergence of various advanced technologies has led to increasingly severe challenges to personnel safety, resulting in a growing demand for and improved performance of bulletproof materials. Currently, bulletproof materials mainly include metals, ceramics, and high-performance fibers. While traditional metal bulletproof materials offer advantages such as good protective performance and low cost, they are generally heavy, inconvenient to wear, and severely impact the mobility of personnel and equipment. In recent years, high-performance fibers, with their advantages of high specific strength, high specific modulus, and low density, have enabled a leap forward in the overall protective performance of bulletproof materials. These fibers mainly include aramid fibers, ultra-high molecular weight polyethylene (UHMWPE) fibers, polyimide fibers, and poly(p-phenylenebenzobisoxazole) fibers. Among them, UHMWPE fibers have already found widespread application in the field of protection. However, UHMWPE fibers have a low coefficient of friction, are prone to large back convexity, and have strong surface chemical inertness.

[0004] In the field of bulletproofing, commonly used adhesives include waterborne polyurethane and polyolefin resins. Waterborne polyurethane possesses excellent bending, impact resistance, and low-temperature resistance, as well as good design flexibility and environmental friendliness. He Yemao et al. used waterborne polyurethane as an adhesive to prepare a unidirectional orthogonal structure of ultra-high molecular weight polyethylene fiber / waterborne polyurethane composite material through a winding-composite-hot-pressing process. The area severely damaged by penetration was limited to a circle with a radius of 35 mm centered on the impact point, demonstrating excellent resistance to multiple impacts.

[0005] Carbon nanotubes possess a large specific surface area, excellent mechanical, electrical, optical, and thermal properties, and good compatibility with resins, making them widely used to improve the interfacial bonding performance of composite materials. Zamani et al. prepared multi-walled carbon nanotube-reinforced polypropylene nanocomposites using melt composite and injection molding processes. The resulting target material was lightweight and exhibited excellent ballistic protection performance. Therefore, introducing carbon nanotubes into adhesive systems holds promise for improving some of the problems existing in fiber-reinforced bulletproof materials. Summary of the Invention

[0006] To address some problems existing in the current application of fiber-based bulletproof materials, this invention provides a method for preparing a waterborne polyurethane / carbon nanotube composite adhesive. This method, through chemical structure design, introduces functionalized carbon nanotubes into waterborne polyurethane containing maleimide groups to prepare a waterborne polyurethane / carbon nanotube composite adhesive. Applying this adhesive to the fiber surface improves the interfacial properties of the fiber composite material while effectively solving problems such as low friction coefficient and large back convexity of ultra-high molecular weight polyethylene fibers.

[0007] The technical solution provided by this invention is as follows:

[0008] In a first aspect, a method for preparing an aqueous polyurethane / carbon nanotube composite adhesive for fiber-based bulletproof materials includes the following steps:

[0009] A waterborne polyurethane prepolymer was synthesized under nitrogen atmosphere protection using isocyanate and polyol as monomers, dibutyltin dilaurate as catalyst, and 2,2-bis(hydroxymethyl)propionic acid as hydrophilic chain extender.

[0010] 4-maleimide-based phenol was added as a modifying monomer to the waterborne polyurethane prepolymer to obtain waterborne polyurethane containing maleimide groups.

[0011] Furan-functionalized carbon nanotubes were added to an aqueous polyurethane containing maleimide groups. These nanotubes were introduced covalently via Diels-Alder reaction and esterification. Triethylamine was then added for neutralization, and finally deionized water was added for high-speed shear emulsification to obtain an aqueous polyurethane / carbon nanotube composite adhesive.

[0012] In some embodiments, the polyisocyanate in the polymer monomer is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, and the polyol is selected from one or more of poly(1,4-butanediol adipate), poly(ethylene adipate), polycaprolactone polyol, poly(ethylene adipate) diol, and polycarbonate polyol.

[0013] In some embodiments, 4-maleimide-phenol accounts for 0.1-20 wt% of the system, preferably 5-10 wt%.

[0014] In some embodiments, the reaction temperature of the aqueous polyurethane prepolymer reaction system containing maleimide groups is 40-90°C, and the reaction time is 0.5-2h.

[0015] In some embodiments, the amount of furan-functionalized carbon nanotubes added in the aqueous polyurethane / carbon nanotube composite adhesive system is 0.005-5%, preferably 0.01%-2%.

[0016] In some embodiments, the Diels-Alder reaction and esterification reaction are carried out at temperatures of 50-90°C and for a reaction time of 0.5-2 h.

[0017] In some embodiments, the mass ratio of triethylamine to 2,2-bis(hydroxymethyl)propionic acid is 1:0.5, the neutralization reaction temperature is 30-60°C, and the reaction time is 0.5-1h.

[0018] In some embodiments, the mass ratio of ethylenediamine to deionized water is 1:10, the proportion of ethylenediamine / deionized water in the waterborne polyurethane / carbon nanotube composite adhesive system is 50%-80%, the high-speed shear emulsification speed is 500-5000 rpm, and the treatment time is 0.5-3h.

[0019] Secondly, the present invention provides an aqueous polyurethane / carbon nanotube composite adhesive for fiber bulletproof materials, which is prepared by the aforementioned preparation method.

[0020] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0021] (1) This invention introduces carbon nanotubes into the adhesive system through chemical grafting, which effectively improves the interfacial properties of fiber-adhesive composite materials.

[0022] (2) The excellent mechanical properties of carbon nanotubes effectively improve the problems of low friction coefficient and large back convexity of ultra-high molecular weight polyethylene fibers. Detailed Implementation

[0023] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] The present invention will be further described below with reference to the embodiments.

[0025] Example 1

[0026] Step 1: Mix 6g of hexamethylene diisocyanate, 25g of poly(ethylene adipate diol), 2μL of dibutyltin dilaurate, and 2g of 2,2-bis(hydroxymethyl)propionic acid at 105℃ under a nitrogen atmosphere with mechanical stirring for 2 hours to obtain an aqueous polyurethane prepolymer.

[0027] Step 2: Add 1.2g of 4-maleimide-based phenol to the waterborne polyurethane prepolymer and react with mechanical stirring at 90℃ for 1h to obtain a waterborne polyurethane prepolymer containing maleimide groups.

[0028] Step 3: Add 0.5g of furan-functionalized carbon nanotubes to the aqueous polyurethane prepolymer containing maleimide groups, and stir mechanically at 60℃ for 1h. Then add 1g of triethylamine for neutralization reaction, and finally add 80mL of ethylenediamine / deionized water for high-speed shear emulsification at a shear rate of 3000rpm to obtain the aqueous polyurethane / carbon nanotube composite adhesive.

[0029] Example 2

[0030] Step 1: Mix 6g of hexamethylene diisocyanate, 25g of poly(ethylene adipate diol), 2μL of dibutyltin dilaurate, and 2g of 2,2-bis(hydroxymethyl)propionic acid at 105℃ under a nitrogen atmosphere with mechanical stirring for 2 hours to obtain an aqueous polyurethane prepolymer.

[0031] Step 2: Add 0.6g of 4-maleimide-based phenol to the waterborne polyurethane prepolymer and react with mechanical stirring at 90℃ for 1h to obtain a waterborne polyurethane prepolymer containing maleimide groups.

[0032] Step 3: Add 0.1g of furan-functionalized carbon nanotubes to the aqueous polyurethane prepolymer containing maleimide groups, and react with mechanical stirring at 60℃ for 1h. Then add 1g of triethylamine for neutralization reaction, and finally add 80mL of ethylenediamine / deionized water for high-speed shear emulsification at a shear rate of 3000rpm to obtain the aqueous polyurethane / carbon nanotube composite adhesive.

[0033] Comparative Example 1

[0034] Step 1: Mix 6g of hexamethylene diisocyanate, 25g of poly(ethylene adipate diol), 2μL of dibutyltin dilaurate, and 2g of 2,2-bis(hydroxymethyl)propionic acid at 105℃ under a nitrogen atmosphere with mechanical stirring for 2 hours to obtain an aqueous polyurethane prepolymer.

[0035] Step 2: Add 1g of triethylamine for neutralization reaction, and finally add 60mL of ethylenediamine / deionized water for high-speed shear emulsification at a shear rate of 3000rpm to obtain waterborne polyurethane adhesive.

[0036] Comparative Example 2

[0037] Step 1: Mix 6g of hexamethylene diisocyanate, 25g of poly(ethylene adipate diol), 2μL of dibutyltin dilaurate, and 2g of 2,2-bis(hydroxymethyl)propionic acid at 105℃ under a nitrogen atmosphere with mechanical stirring for 2 hours to obtain an aqueous polyurethane prepolymer.

[0038] Step 2: Add 0.6g of 4-maleimide-based phenol to the waterborne polyurethane prepolymer and react with mechanical stirring at 90℃ for 1h to obtain a waterborne polyurethane prepolymer containing maleimide groups.

[0039] Step 3: Then add 1g of triethylamine for neutralization reaction, and finally add 60mL of ethylenediamine / deionized water for high-speed shear emulsification at a shear rate of 3000rpm to obtain waterborne polyurethane adhesive.

[0040] According to the JC / T 773-2010 standard, interlaminar shear test samples were prepared, and the interlaminar shear strength (ILSS) of UHMWPE / adhesive composites was determined using a universal tensile tester. Specific test results are shown in Table 1.

[0041] Fabrication of bulletproof chips for bulletproof testing:

[0042] (1) Preparation of UHMWPE nonwoven fabric:

[0043] The above adhesive is placed in a glue tank, and UHMWPE fibers are impregnated, spread, fixed and dried to obtain fiber cloth; then the two layers of fiber cloth are stacked at 0° / 90° and pressed to obtain UHMWPE non-woven fabric.

[0044] (2) Press UHMWPE nonwoven fabric through a specific pressing process to obtain a fiber bulletproof layer;

[0045] (3) The bulletproof layer and the cushioning material are combined with a waterproof cloth and then sealed to obtain the bulletproof chip. The bulletproof chip is obtained by impregnating it with the adhesive prepared in Examples 1 and 2 and Comparative Examples 1 and 2.

[0046] The ballistic performance of the aforementioned bulletproof chip was tested using a target practice test conducted according to the U.S. Department of Justice NIJ0101.06 Class IIIA standard for body armor. This involved using a 15.6g .44 Magnum semi-jacketed hollow-point (SJHP) bullet with a velocity of (408±9.1) m / s. Specific test results are shown in Table 1.

[0047] Table 1. ILSS and ballistic protection performance of different embodiments and comparative examples

[0048]

[0049] The comparison of ILSS performance between the examples and comparative examples shows that the present invention introduces carbon nanotubes into the adhesive system through chemical grafting, achieving a uniform dispersion effect. Due to the mechanical entanglement and excellent mechanical properties of carbon nanotubes, the interfacial bonding performance of fiber composite materials is improved, while effectively addressing the problem of large back concavity in UHMWPE as a bulletproof material.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an aqueous polyurethane / carbon nanotube composite adhesive for a fiber ballistic material, characterized by, The method comprises the following steps: An aqueous polyurethane prepolymer is synthesized under nitrogen atmosphere protection by using a polyisocyanate and a polyol as polymerization monomers, dibutyltin dilaurate as a catalyst, and 2.2-bis(hydroxymethyl)propionic acid as a hydrophilic chain extender; 4-maleimide phenol is added to the aqueous polyurethane prepolymer as a modified monomer to obtain an aqueous polyurethane containing a maleimide group; Furan-functionalized carbon nanotubes are added to the aqueous polyurethane containing a maleimide group, and are introduced in a covalent bond manner through Diels-Alder reaction and esterification reaction, then triethylamine is added for neutralization reaction, and finally ethylenediamine / deionized water is added for high-speed shearing emulsification, to obtain an aqueous polyurethane / carbon nanotube composite adhesive.

2. The method for preparing an aqueous polyurethane / carbon nanotube composite adhesive for a fiber ballistic material according to claim 1, characterized by: The ratio of isocyanate groups to hydroxyl groups in the polymerization monomers is 1.0-5.0, preferably 2.0-3.

5.

3. The method for preparing an aqueous polyurethane / carbon nanotube composite adhesive for a fiber ballistic material according to claim 1, characterized by: The content of 2.2-bis(hydroxymethyl)propionic acid in the aqueous polyurethane prepolymer reaction system is 1%-12%, preferably 4%-8%.

4. The method for preparing an aqueous polyurethane / carbon nanotube composite adhesive for a fiber ballistic material according to claim 1, characterized by: The reaction temperature of the aqueous polyurethane prepolymer reaction system is 60-100°C, and the reaction time is 1-3h.

5. The method for preparing an aqueous polyurethane / carbon nanotube composite adhesive for a fiber ballistic material according to claim 1, characterized by: The content of 4-maleimide phenol in the aqueous polyurethane prepolymer reaction system containing a maleimide group is 1%-12%, preferably 3%-8%.

6. The method for preparing the waterborne polyurethane / carbon nanotube composite adhesive for fiber bulletproof materials according to claim 1, characterized in that: The reaction temperature of the aqueous polyurethane reaction system containing a maleimide group is 40-90°C, and the reaction time is 0.5-2h.

7. The method for preparing the waterborne polyurethane / carbon nanotube composite adhesive for fiber bulletproof materials according to claim 1, characterized in that: The addition amount of the furan-functionalized carbon nanotubes in the aqueous polyurethane / carbon nanotube composite adhesive system is 0.005%-5%, preferably 0.01%-2%.

8. The process for preparing an aqueous polyurethane / carbon nanotube composite binder for fiber ballistic materials according to claim 1, characterized in that: The temperature of the Diels-Alder reaction and the esterification reaction is 50-90°C.

9. The process for preparing an aqueous polyurethane / carbon nanotube composite binder for fiber ballistic materials according to claim 1, characterized in that: The mass ratio of triethylamine to 2.2-bis(hydroxymethyl)propionic acid is 1:0.5, and the neutralization reaction temperature is 30-60°C.

10. The method for preparing the waterborne polyurethane / carbon nanotube composite adhesive for fiber bulletproof materials according to claim 1, characterized in that: The mass ratio of ethylenediamine to deionized water is 1:10, the content of ethylenediamine / deionized water in the aqueous polyurethane / carbon nanotube composite adhesive system is 50%-80%, and the high-speed shearing emulsification speed is 500-5000rpm.

11. An aqueous polyurethane / carbon nanotube composite binder for fiber ballistic materials, characterized by: Prepared by the preparation method of any one of claims 1-10.

12. The aqueous polyurethane / carbon nanotube composite adhesive of claim 11 is applied in fiber bulletproof materials.

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