Durable flame-retardant super-hydrophobic fabric coating, method and application thereof

Abstract

The invention belongs to the field of new materials, and particularly relates to a durable flame-retardant super-hydrophobic fabric coating as well as a method and application thereof. According to the invention, the flame-retardant layer is formed by using the flame retardant ammonium polyphosphate (APP) and pentaerythritol (PER), the hydrophobic layer is prepared by using the flame-retardant layer and hydrophobic silica nanoparticles (SiO2)-polydimethylsiloxane (PDMS), and the coated fabric material has good antifouling property on water, cola, orange juice and the like, and has very good flame-retardant property. The static contact angle (WCA) between the flame-retardant super-hydrophobic fabric coating (HFRC) and water is larger than 150 degrees, and the flame-retardant super-hydrophobic fabric coating still has very good water resistance and self-cleaning performance after 150 times of abrasion or 100 times of kneading. The limit oxygen index of the material treated by the HFRC is 39%. Therefore, the HFRC has very good super-hydrophobicity, durability and flame retardance, and a new thought is provided for simple and low-cost preparation of the flame-retardant super-hydrophobic fabric coating.

Description

Technical Field

[0001] This invention belongs to the field of new materials, and specifically relates to a durable, flame-retardant, superhydrophobic fabric coating, its method, and its application. Background Technology

[0002] Textiles, cotton fabrics, and polyurethane are widely used in people's daily lives, appearing in clothing and bedding. With technological advancements, the demand for textiles is increasing. However, there are two major obstacles in developing durable fabrics. First, most textiles are highly flammable, posing a fire hazard in daily life and endangering people's safety. The second challenge is that textile-based materials are easily stained by liquids such as water, coffee, tea, or cola. Therefore, enabling these materials to simultaneously achieve waterproofing, flame retardancy, and durability would greatly benefit the textile industry and significantly improve people's lives.

[0003] The most common method for flame-retardant treatment of fabric-based materials is surface modification. There are reports of preparing flame-retardant coatings by cyclic deposition of polycationic / anionic bilayer films on cotton-based materials; however, these coatings are water-soluble and lose their properties after washing, which greatly hinders their practical application.

[0004] Lotus-effect-inspired superhydrophobic surfaces remain dry and clean upon contact with water. Water droplets can easily roll off a lotus leaf surface, removing dust and achieving self-cleaning properties. Superhydrophobic surfaces have already demonstrated their anti-fouling and self-cleaning applications on fabrics. However, the micro- and nanostructures necessary for superhydrophobic properties are fragile and easily damaged by external forces, leading to superhydrophobic failure. Therefore, fabricating a durable superhydrophobic fabric coating is crucial for practical applications.

[0005] While flame-retardant superhydrophobic coatings are typically achieved separately, some studies have addressed both challenges in a single material. Research has used mapping methods to create flame-retardant / self-healing waterproof surfaces on cotton substrates. However, modifications, such as those containing fluorocarbons, are expensive and may cause environmental and safety issues, especially when applying such coatings to clothing. Therefore, creating durable, environmentally friendly, and inexpensive coatings that combine flame retardancy with the waterproof properties of fabric materials remains challenging.

[0006] This invention develops a fabric coating with excellent flame retardancy, superhydrophobicity, and durability. The coating uses APP, which has excellent flame retardant properties, and crosslinks PER and APP to form a flame-retardant layer. A low-surface-energy non-fluorinated superhydrophobic layer is formed using PDMS and fumed silica. This coating can easily adhere to cotton fabrics, PU sponges, and cotton to prevent them from burning. It is also waterproof, repellent of everyday liquids such as tea, coffee, and milk. The coating retains its function even after mechanical wear. The coating preparation process is simple and low-cost, providing a new approach to flame-retardant superhydrophobic coatings. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention provides a durable, flame-retardant, superhydrophobic fabric coating, a method thereof, and its application.

[0008] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a durable flame-retardant superhydrophobic fabric coating, the coating comprising a flame-retardant layer formed by flame retardant ammonium polyphosphate (APP) and pentaerythritol (PER), and a hydrophobic layer prepared by hydrophobic silica nanoparticles (SiO2-polydimethylsiloxane PDMS). The flame-retardant superhydrophobic fabric coating HFRC has a static contact angle (WCA) with water greater than 150° and still has excellent water resistance and self-cleaning properties after 150 abrasion cycles or 100 kneading cycles. The limiting oxygen index of the material treated with HFRC is 39%.

[0009] Secondly, the present invention provides a method for preparing a durable, flame-retardant, superhydrophobic fabric coating, comprising the following steps: Step 1: Preparation of flame-retardant APP / PER coating Dissolve ammonium polyphosphate and pentaerythritol in 40-80 mL of deionized water, immerse the fabric, and place it at 50-90°C. o React in an oil bath for 0.5-1.5 hours, then remove and place at 60-100°C. o Dry in an oven at temperature C for 1-3 hours to obtain the flame-retardant APP / PER flame-retardant coating.

[0010] Step Two: Hydrophobic silica and PDMS were dispersed in 100 ml of anhydrous ethanol and incubated in an ice-water bath for 0-4 hours. o Under C conditions, ultrasonic treatment is performed for 20 minutes. After ultrasonic treatment, a curing agent is added, and mechanical stirring is carried out until homogeneous to obtain anhydrous ethanol precursor solution. The pre-made flame-retardant cotton fabric is immersed in the anhydrous ethanol precursor solution and stirred and impregnated for 30-40 minutes in a sealed environment at room temperature. Then, it is placed at 50°C. o Process in a C-type forced-air drying oven for 30 minutes, then raise the temperature to 80°C. o After curing at C for 2 hours, HFRC-coated cotton fabric is obtained.

[0011] The hydrophobic silica, PDMS, and curing agent were dispersed in 100 ml of anhydrous ethanol and placed at 60 °C. o Stir in a water bath at C, immerse the cotton fabric for 0.5-2 hours, then heat at 60-100°C. o Curing at C for 1-3 hours yields HFRC-coated cotton fabric.

[0012] Furthermore, the cotton fabric material includes cotton and sponge.

[0013] Furthermore, in step one, the concentration of ammonium polyphosphate is 2-11 wt%.

[0014] Furthermore, in step one, the concentration of pentaerythritol is 0.6-4 wt%.

[0015] Furthermore, in step one, the fabric area is 10-50 cm². 2 .

[0016] Furthermore, in step two, the concentration of hydrophobic silica is 0.5-2 wt%.

[0017] Furthermore, in step two, the concentrations of PDMS and 0.1-0.4 wt% Dow Corning PDMS curing agent are 1-4 wt% and 0.1-0.4 wt%, respectively.

[0018] Thirdly, the present invention provides the application of durable, flame-retardant, superhydrophobic fabric coatings in the textile and apparel fields.

[0019] Compared with the prior art, the advantages of the present invention are as follows: This invention develops a fabric coating with excellent flame retardancy, superhydrophobicity, and durability. The coating uses APP, which has excellent flame retardant properties, and crosslinks PER and APP to form a flame-retardant layer. A low-surface-energy non-fluorinated superhydrophobic layer is formed using PDMS and fumed silica. This coating can easily adhere to cotton fabrics, PU sponges, and cotton to prevent them from burning. It is also waterproof, repellent of everyday liquids such as tea, coffee, and milk. The coating retains its function even after mechanical wear. The coating preparation process is simple and low-cost, providing a new approach to flame-retardant superhydrophobic coatings. Attached Figure Description

[0020] The invention will now be further described with reference to the accompanying drawings.

[0021] Figure 1 is a flowchart of the preparation process of flame-retardant superhydrophobic fabric coating; Figure 2 shows the microstructure (a) of the HFRC coating and the corresponding distribution of Si (b), O (c) and P (d). Figure 3 shows the water repellency and stain resistance of (a) fabric, (b) PU sponge and (c) cotton with HFEC coating; and (d) the mirror effect of HFRC-coated PU sponge in water. Figure 4 shows (a1-a2) sandpaper abrasion test and WCA and SA tests after abrasion; (b1-b3) kneading test and WCA and SA tests after kneading cycles; and (c1-c3) stain removal performance of coated cotton fabric after 100 rubbing tests. Figure 5 shows the self-cleaning performance test of cotton fabrics with and without HFRC coating treatment; Figure 6 shows the flame ignition test results of the samples: flame ignition tests were performed on the original and HFRC coated (a) cotton fabric, (b) cotton and (c) PU sponge products; Figure 7 shows the limiting oxygen index of raw and HFRC-coated cotton fabrics. Detailed Implementation

[0022] The invention will now be further described with reference to the accompanying drawings.

[0023] raw materials Polydimethylsiloxane (PDMS) and curing agent (commercially available curing agent), Dow Corning; hydrophobic silica (SiO2), 50 nm particle size, Shandong Yousuo Chemical Technology Co., Ltd.; ammonium polyphosphate (APP), Shanghai Maclean Biochemical Technology Co., Ltd.; pentaerythritol (PER), Shanghai Aladdin Biochemical Technology Co., Ltd. All reagents were used as is without further purification. Example

[0024] Step 1: Preparation of flame-retardant APP / PER coating Dissolve 2-11 wt% ammonium polyphosphate and 0.6-4 wt% pentaerythritol in 40-80 mL of deionized water. Add the fabric (cotton fabric material includes cotton and sponge, fabric area 10-50 cm²) to the solution. 2 Place it in and set it at 50-90 degrees Celsius. o React in an oil bath for 0.5-1.5 hours, then remove and place at 60-100°C. o Dry in oven C for 1-3 hours to obtain the material with APP / PER flame-retardant skeleton; Step Two: Disperse 0.5-2 wt% 50nm hydrophobic silica and 1-4 wt% PDMS in 100 ml of anhydrous ethanol, and incubate in an ice-water bath for 0-4 hours. oUnder C conditions, ultrasonic treatment is performed for 20 minutes. After ultrasonic treatment, 0.1-0.4 wt% curing agent is added, and mechanical stirring is carried out until homogeneous to obtain anhydrous ethanol precursor solution. The pre-made flame-retardant cotton fabric is immersed in the anhydrous ethanol precursor solution and stirred and impregnated for 30-40 minutes in a sealed environment at room temperature. Then, it is placed at 50°C. o Process in a C-type forced-air drying oven for 30 minutes, then raise the temperature to 80°C. o After curing at C for 2 hours, HFRC-coated cotton fabric is obtained.

[0025] More specifically: HFRC coating preparation Add 3 g of ammonium polyphosphate (APP) and 1 g of pentaerythritol (PER) to 60 ml of deionized water and ultrasonically disperse for 30 minutes to completely break down the agglomerates and form a uniform micro / nano suspension. Immerse a cotton fabric (80 mm × 50 mm × 3 mm) in the suspension and place it at 80°C. o React in an oil bath at C with magnetic stirring (300 rpm) for 1 hour. Remove the fabric and place it in an 80°C container. o Dry in a C-type forced-air drying oven to constant weight; obtain the material with APP / PER flame-retardant skeleton.

[0026] Add 1 g of hydrophobic silica and 2 g of PDMS to 100 ml of anhydrous ethanol, and incubate in an ice-water bath (0-40°C). o Under condition C), ultrasonic treatment is performed for 20 minutes. After ultrasonic treatment, 0.2 g of curing agent is added, and the mixture is gently mechanically stirred for 5 minutes until homogeneous. The pre-made flame-retardant cotton fabric is then immersed in the above anhydrous ethanol precursor solution and heated at room temperature (25°C). o C) Stir and soak for 30-40 minutes in a sealed environment, then place at 50°C. o Process in a C-type forced-air drying oven for 30 minutes, then raise the temperature to 80°C. o C curing for 2 hours.

[0027] This method is also applicable to other fabric materials, such as cotton and sponge. Example

[0028] Testing of microstructure, elemental distribution and content The HFRC-coated fabric was cut into 0.3 cm × 0.3 cm pieces. The fabric was then attached to a stainless steel test stage with conductive adhesive using tweezers. The sample surface was then vacuum sputtered with gold. The microstructure, elemental distribution, and content were analyzed using a scanning electron microscope (Regulus 8220 Hitachi).

[0029] Contact angle roll-off test 5 μL of water was dropped onto the sample surface, and the contact angle and roll-off angle of the HFRC coated cotton fabric were tested and recorded using a contact angle test. Each sample was tested 5 times and the average value and standard deviation were taken.

[0030] Mechanical property testing The cotton fabric with HFRC coating was placed on 1000-grit sandpaper, and a 50 g weight was placed on top of the sample. The sample was dragged back and forth, with each 20 cm movement constituting one cycle. The contact angle and sliding angle of the sample were tested after 25, 50, 100, and 150 cycles. For the rubbing test, the cotton fabric with HFRC coating was rubbed and then unfolded.

[0031] Self-cleaning test and stain resistance test Self-cleaning and antifouling tests were conducted on HFRC samples. A turbid solution was prepared using mud and deionized water. HFRC material was placed into the solution using tweezers and then removed. The surface of the material was observed to determine whether it was contaminated and wetted. Eight liquids—milk, cola, orange juice, coffee, tea, potassium permanganate solution, and acid / base reagents—were dropped onto the surface of the HFRC material. The state of the droplets was observed to determine whether the material possessed the corresponding antifouling properties.

[0032] Flame retardant test HFRC-coated cotton fabric, cotton, polyurethane foam, and their respective untreated samples were clamped together. The materials were ignited with a flame generated from methane combustion for 5 seconds and then removed to compare the differences between the treated and untreated samples. The limiting oxygen index of both the untreated and HFRC-coated cotton fabrics was tested using a limiting oxygen index tester (JF-3 Testec).

[0033] Example 3 Results and Discussion Micromorphology of HFRC materials EDS and mapping imaging were used to characterize the distribution of elements in HFRC, such as Figure 2 It can be seen that Si, O, and P elements are uniformly distributed in HFRC materials and are consistent with the microstructure of the material. Figure 2The coating exhibits a high degree of overlap, and at the micrometer scale, it displays an irregular, raised structure. These micro- and nanostructures are the primary source of surface roughness. By combining with low surface energy materials, these structures stabilize and trap air layers, transforming intrinsic hydrophobicity into superior superhydrophobicity, thus achieving efficient repulsion of water-based liquids. The uniform distribution of Si on the fabric indicates good dispersion of hydrophobic SiO2 and PDMS. Regarding flame retardancy, this structure acts as an oxygen barrier, guiding the formation of a porous char layer during combustion and preventing further combustion. The reaction between pentaerythritol and ammonium polyphosphate in the material generates a phosphorus-containing flame-retardant layer; therefore, the distribution of phosphorus indicates a uniform distribution of the flame-retardant layer on the cotton fabric. This is consistent with experimental assumptions and is a crucial prerequisite for ensuring the hydrophobic and flame-retardant properties of the HPRC coating.

[0034] Superhydrophobicity and antifouling properties of HFRC materials To test the superhydrophobicity and stability of the materials, cotton fabrics, PU sponges, and cotton coated with HFRC were subjected to repulsion tests against various liquids such as tea, milk, coffee, orange juice, cola, saturated KMnO4 solution, and highly corrosive liquids. Figure 3 ac, the desired sample has a static contact angle (WCA) greater than 150°. Figure 3 When PU sponges with and without HFRC coating are immersed in water, a mirror-like effect appears on the surface of the coated PU sponge. This is due to the total reflection of light in the air layer of the surface structure, which water cannot penetrate. This demonstrates the high water resistance of the HFRC coating.

[0035] Mechanical properties and stability of HFRC materials Mechanical properties are a key issue for superhydrophobic surfaces. The mechanical stability of HFRC materials on cotton fabrics was assessed using 1000-grit sandpaper. Figure 4 As shown in a1-a2, the relationship between WCA and wear cycles is as follows: Figure 4 As shown in b1-b3, after 150 abrasion cycles, the WCA remained above 151° and the roll-off angle (SA) below 10°, indicating excellent mechanical properties of the coating. Importantly, the coated cotton fabric exhibits structural stability and durability; kneading does not damage its hydrophobic layer, and after 100 kneading cycles, the WCA remained above 150° and the SA remained below 10°. Figure 4 As shown in c1-c3. After kneading, the cotton fabric will not get wet even when impacted by water, and no water droplets will remain on the surface.

[0036] Self-cleaning performance test of HFRC material To test the self-cleaning properties of the material, the material's self-cleaning ability against contaminants was evaluated by immersing coated cotton fabric in a mixture of soil and water (mud). The coated samples were removed from the mud and kept dry and clean. Figure 5 As shown in Figure ac, the HFRC coating imparts excellent self-cleaning properties to the fabric. Conversely, in the experiment, untreated cotton fabrics were easily wetted and contaminated by mud. Figure 5 df).

[0037] Flame retardant properties of HFRC materials Most fabric materials are considered highly flammable. To reduce their flammability and fire risk, APP and PER are included in composite coatings due to their excellent flame-retardant properties. To test the fire resistance of HFRC coatings, untreated and treated cotton fabrics ( Figure 6 a) Cotton Figure 6 b) and PU sponge clip ( Figure 6 c) On a metal rack and exposed to an open flame for 5 seconds, the untreated sample continued to burn until it was completely extinguished after being removed from the open flame, while the sample coated with HFRC extinguished immediately after being removed from the open flame.

[0038] Limiting oxygen index (LOI) is an important parameter for evaluating the flame retardancy of materials. When the LOI > 27%, the material is considered flame retardant. In LIO index tests on treated and untreated cotton fabric samples, the LIO index increased from 18% to 39% after the coating was applied. Figure 7 Therefore, the addition of a flame-retardant layer significantly improves the flame-retardant effect of the material.

[0039] The microstructure and interfacial bonding mechanism of the composite coating in this embodiment are as follows: Unlike the obvious "skin-core" layered structure formed by traditional physical coating, the coating obtained by this invention exhibits a unique "gradient interpenetrating interface".

[0040] This is attributed to the "solvent gradient penetration-stage curing" process introduced during preparation. In the initial stage of coating, the low surface tension (~22 mN / m) of anhydrous ethanol and the capillary action of the pores in the APP / PER layer are used to carry the PDMS prepolymer into the interior of the flame retardant layer through micro-penetration.

[0041] During the subsequent graded heat treatment process (first low-temperature solvent evaporation, then high-temperature crosslinking), the PDMS molecular chains crosslink in situ within the APP / PER micropores, forming a physically interlocked structure. Compared to simple stacked samples without permeation treatment, this gradient interpenetrating structure enhances the adhesion of the coating and effectively solves the technical bottleneck of easy peeling of the hydrophobic layer.

[0042] Surface wettability and dynamic durability Tests show that the static water contact angle (WCA) of the coating surface reaches 156° ± 2° and the roll-off angle (SA) is less than 5°, demonstrating excellent superhydrophobic properties.

[0043] Results Analysis: High-magnification SEM images revealed that the coating surface was not randomly stacked, but rather formed a hierarchical rough structure. This is because, under specific curing kinetic control, hydrophobic nano-SiO2 particles were semi-encapsulated by the PDMS matrix and directionally "pinned" to the surface. Durability Verification: After 50 sandpaper abrasion cycles, the coating's WCA remained above 150°. This further proves that the aforementioned "gradient interpenetrating network" not only enhances interlayer bonding but also provides robust mechanical support for the surface's micro / nano structure, avoiding the poor mechanical properties of conventional superhydrophobic coatings.

[0044] Flame retardant properties and the synergistic enhancement mechanism of silicon-carbon The flame-retardant behavior of the material was evaluated using the limiting oxygen index (LOI) test. This is not a simple additive effect, but rather induces an unexpected "silicon-carbon ceramicization synergistic effect." In the early stages of combustion, the surface PDMS and nano-SiO2 undergo thermal decomposition and transform in situ into an amorphous SiO2 ceramic hard shell. Traditional APP / PER expanded carbon layers are typically loose and porous, easily dispersed by hot airflow. However, in the special structure of this invention, the aforementioned SiO2 ceramic hard shell acts as an "exoskeleton," tightly covering and supporting the internal expanded carbon layer.

[0045] Due to the presence of the "gradient interpenetrating interface," no delamination occurs between the ceramic layer and the carbon layer; instead, a complete "ceramic-expanded carbon" integrated heat shield layer is formed. This dense composite structure effectively blocks the penetration of oxygen and the volatilization of combustible gases, thereby achieving unexpected flame retardant enhancement.

[0046] In summary, this invention synthesizes an HFRC coating by integrating flame retardants ammonium polyphosphate and pentaerythritol into silica nanoparticles-PDMS composite materials. This coating exhibits excellent water resistance, self-cleaning and anti-fouling properties in daily use, and a stable composite structure with significant abrasion resistance. Simultaneously, the HFRC coating demonstrates significant flame retardant properties, primarily due to coating carbonization, which prevents contact between oxygen and the substrate during combustion. The coating's superhydrophobicity provides protection against water-soluble flame retardants, resulting in better durability compared to traditional flame retardant materials. Compared to superhydrophobic materials, the HFRC coating significantly reduces the risk of fire. Therefore, the HFRC coating, with its advantages of simple processing and low cost, offers new prospects for the industrial production and application of flame-retardant superhydrophobic fabric coatings.

Claims

1. A durable, flame-retardant, superhydrophobic fabric coating, characterized in that, The coating comprises a flame-retardant layer formed by flame retardant ammonium polyphosphate (APP) and pentaerythritol (PER), and a hydrophobic layer prepared by hydrophobic silica nanoparticles (SiO2-polydimethylsiloxane PDMS). The flame-retardant superhydrophobic fabric coating HFRC has a static contact angle (WCA) with water greater than 150° and still has excellent water resistance and self-cleaning properties after 150 abrasion cycles or 100 kneading cycles. The limiting oxygen index of the material treated with HFRC is 39%.

2. The method for preparing a durable, flame-retardant, superhydrophobic fabric coating according to claim 1, characterized in that, Includes the following steps: Step 1: Preparation of flame-retardant APP / PER coating Dissolve ammonium polyphosphate and pentaerythritol in 40-80 mL of deionized water, immerse the fabric, and place it at 50-90°C. o React in an oil bath for 0.5-1.5 hours, then remove and place at 60-100°C. o Dry in oven C for 1-3 hours to obtain the material with APP / PER flame-retardant skeleton; Step Two: Hydrophobic silica and PDMS were dispersed in 100 ml of anhydrous ethanol and incubated in an ice-water bath for 0-4 hours. o Under C conditions, ultrasonic treatment is performed for 20 minutes. After ultrasonic treatment, a curing agent is added, and mechanical stirring is carried out until homogeneous to obtain anhydrous ethanol precursor solution. The pre-made flame-retardant cotton fabric is immersed in the anhydrous ethanol precursor solution and stirred and impregnated for 30-40 minutes in a sealed environment at room temperature. Then, it is placed at 50°C. o Process in a C-type forced-air drying oven for 30 minutes, then raise the temperature to 80°C. o After curing at C for 2 hours, HFRC-coated cotton fabric is obtained.

3. The method according to claim 2, characterized in that, The cotton fabric is made of materials including cotton and sponge.

4. The method according to claim 2, characterized in that, In step one, the concentration of ammonium polyphosphate is 2-11 wt%.

5. The method according to claim 2, characterized in that, In step one, the concentration of pentaerythritol is 0.6-4 wt%.

6. The method according to claim 2, characterized in that, In step one, the fabric area is 10-50 cm². 2 .

7. The method according to claim 2, characterized in that, In step two, the concentration of hydrophobic silica is 0.5-2 wt%.

8. The method according to claim 2, characterized in that, In step two, the concentrations of PDMS and curing agent are 1-4 wt% and 0.1-0.4 wt%, respectively.

9. The application of the durable, flame-retardant, superhydrophobic fabric coating according to claim 1 in the textile and apparel industry.

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