A sandwich fabric with high coating adhesion strength having a gradient interface enhancement structure and a preparation method thereof

Abstract

The present invention provides a laminated fabric with a gradient interface enhancement structure and high coating adhesion strength, and a preparation method thereof, belonging to the technical field of coated fabrics. The laminated fabric of the present invention is composed of multiple layers of materials, including a high-performance fabric as the central layer, and thermoplastic fiber glue nets 1, non-woven fiber felts, thermoplastic fiber glue nets 2, and thermoplastic polymer film layers symmetrically arranged in sequence; wherein, the high-performance fabric exerts the advantages of tensile and puncture properties, and the non-woven fiber felt provides the advantage of tear resistance. By roughening the surface of the high-performance fiber itself to generate micro-nano fibers, and combining with the non-woven fiber felt to realize the interface transition between the high-performance fiber and the polymer matrix, that is, using the micro-nano fibers in the high-performance fabric and the fibers in the non-woven fiber felt to provide a gradient interface structure, thereby improving the coating adhesion strength. The present invention realizes the interface combination between the high-performance fiber and the polymer matrix through the combination of multiple mechanisms, and at the same time, the non-woven fiber felt can also improve the tear strength.

Description

Technical Field

[0001] The present invention relates to the technical field of coated fabrics, and in particular to a high-coated adhesion strength sandwich fabric with a gradient interface enhancement structure and a preparation method thereof. Background Art

[0002] At present, polymer-coated polyester fabrics are widely used in the fields of industry and protective materials due to their low cost and strong durability. However, their mechanical properties such as tensile strength, tear strength, and puncture resistance are poor, making it difficult to meet high-performance requirements. Para-aramid is a chain-like polymer material with high strength and high modulus, having excellent dimensional stability, impact resistance, chemical resistance, and excellent heat resistance, and is widely used as a reinforcing fiber for advanced composite materials. However, aramid has a high crystallinity, lacks polar groups on its surface, and has a smooth surface, resulting in a low surface energy and poor surface wettability, which is not conducive to the adhesion between aramid and the matrix resin, leading to interface defects between aramid and the polymer matrix, restricting the performance of composite materials. At present, the main surface modification methods of aramid include plasma treatment, high-energy ray treatment, chemical etching, surface grafting, surface coating, etc. The invention patent CN202010824820.8 discloses a surface-coated PUR aramid fiber and a preparation method thereof. The aramid fiber is immersed in a hot-melt moisture-curing reaction-type polyurethane hot melt adhesive. After the PUR on the surface of the aramid fiber is heated and melted, self-bonding of the aramid fiber can be achieved, and the surface adhesion between the aramid fiber and other substrates can be improved. Although the surface energy of the aramid fiber coated with PUR is increased, the interfacial bonding between the original aramid fiber and the surface PUR coating layer has not been fundamentally improved. During loading, peeling is likely to occur between the aramid fiber and the PUR coating. Therefore, it is necessary to design the interfacial bonding between aramid and the thermoplastic polymer to achieve strong interfacial bonding between aramid and the polymer matrix. The surface of the aramid fiber is smooth. Constructing a rough structure on the surface of aramid to improve its inlay bonding with the polymer matrix is an effective way to improve the interfacial bonding between the two. A typical method is to deposit nanoparticles on the surface of aramid, such as nano-polyacrylonitrile, carbon, nano-SiO 2 、TiO 2 and zinc oxide. However, the deposited nanoparticles are usually combined with aramid fibers through physical adsorption or weak chemical bonds, and the nanoparticles are easy to fall off, and there are certain difficulties in controlling the uniformity and thickness of the deposited layer. Especially when the size of the nanoparticles is large or the distribution is uneven, excessive deposition of nanoparticles may lead to an increase in the thickness of the interfacial layer, resulting in a stress concentration effect at the interface and affecting the mechanical properties of the composite fiber material. Summary of the Invention

[0003] The purpose of the present invention is to provide a high-coated adhesion strength sandwich fabric with a gradient interface enhancement structure and a preparation method thereof, which can improve the coated adhesion strength of the sandwich fabric.

[0004] To achieve the above-mentioned invention objectives, the present invention provides the following technical solutions:

[0005] The present invention provides a preparation method of a sandwich fabric with high coating adhesion strength and a gradient interface enhancement structure, comprising the following steps:

[0006] Ultrasonically compound a high-performance fabric with an alkali solution and an organic solvent for surface roughening treatment to obtain a high-performance fabric with a micro-nano structure; the high-performance fibers used in the high-performance fabric include one or more of aramid fiber, polybenzimidazole fiber, polyimide fiber, polyether ether ketone fiber, and polyhydrazide fiber;

[0007] Apply a first thermoplastic fiber glue net on the surface of the high-performance fabric with a micro-nano structure to obtain a high-performance fabric covered with a fiber glue net;

[0008] After applying a non-woven fiber felt on the surface of the high-performance fabric covered with a fiber glue net, perform a first hot pressing treatment, and then apply a second thermoplastic fiber glue net on the surface of the non-woven fiber felt to obtain a composite net fabric;

[0009] Apply a thermoplastic polymer film on the surface of the composite net fabric and perform a second hot pressing treatment to obtain a sandwich fabric with high coating adhesion strength and a gradient interface enhancement structure.

[0010] Preferably, the parameters of the high-performance fabric include: the areal density is 150 - 500 g / m 2 , the fineness of the filament yarn used is 800 - 1800 D, the warp and weft yarn densities are independently 15 - 30 pieces per inch, and the fabric weave is plain weave or twill weave.

[0011] Preferably, the alkali solution includes one or more of potassium hydroxide solution, sodium hydroxide solution, and ammonia water solution; the organic solvent includes one or more of dimethyl sulfoxide, N-methylpyrrolidone, and N,N-dimethylformamide; the volume ratio of the alkali solution to the organic solvent is 1 - 3:100, and the concentration of the alkali solution is 0.1 - 0.2 g / mL.

[0012] Preferably, the time for the surface roughening treatment is 1 - 4 h; the ultrasonic frequency for the ultrasonic compounding is 20 - 30 kHz, and the stirring speed is 300 - 800 rpm.

[0013] Preferably, the areal densities of the first thermoplastic fiber glue net and the second thermoplastic fiber glue net are independently 30 - 50 g / m 2 .

[0014] Preferably, both the first thermoplastic fiber glue net and the second thermoplastic fiber glue net are prepared by a melt-blown non-woven forming method.

[0015] Preferably, based on the mass percentage, the raw materials for preparing the first thermoplastic fiber glue net and the second thermoplastic fiber glue net include: 50-70% of ethylene-vinyl acetate copolymer, 10-20% of polyurethane, and 20-30% of copolyester.

[0016] Preferably, the non-woven fiber felt is prepared by a thermo-bonding non-woven forming method from polyester fibers and high-strength fibers. The high-strength fibers include aramid fibers and / or glass fibers. The mass ratio of the polyester fibers to the high-strength fibers is 20:80 to 50:50, and the areal density of the non-woven fiber felt is 20-60 g / m 2 .

[0017] Preferably, the conditions for the first hot pressing treatment include: a pressure of 0.5-0.8 MPa, a temperature of 150-180 °C, and a time of 0.5-1 min;

[0018] The conditions for the second hot pressing treatment include: a pressure of 0.5-0.8 MPa, a temperature of 140-160 °C, and a time of 1-2 min.

[0019] The present invention provides a high-coated adhesion strength sandwich fabric with a gradient interface enhancement structure prepared by the preparation method described in the above technical solution.

[0020] The present invention provides a preparation method for a high-coated adhesion strength sandwich fabric with a gradient interface enhancement structure. The sandwich fabric of the present invention is composed of multiple layers of materials, including a high-performance fabric as the central layer, and thermoplastic fiber glue net 1, non-woven fiber felt, thermoplastic fiber glue net 2, and thermoplastic polymer film layer symmetrically arranged in sequence. Among them, the high-performance fabric exerts the advantages of tensile and puncture properties, and the non-woven fiber felt provides the advantage of tear resistance. By roughening the surface of the high-performance fiber itself, micro-nano fibers are generated, and the interface transition between the high-performance fiber and the polymer matrix is realized in combination with the non-woven fiber felt, that is, the micro-nano fibers in the high-performance fabric and the fibers in the non-woven fiber felt are used to provide a gradient interface structure, thereby improving the coating adhesion strength. The present invention realizes the interfacial bonding between the high-performance fiber and the polymer matrix through the combination of multiple mechanisms, and at the same time, the non-woven fiber felt can also improve the tear strength.

[0021] Compared with the prior art, the present invention has significant advantages in the following aspects:

[0022] By roughening the surface of the fiber in the high-performance fabric itself, on the one hand, surface active sites generated by chemical etching treatment of the fiber are produced, and on the other hand, nano-scale fiber whiskers are formed on the fiber surface, resulting in a mechanical locking effect with the polymer matrix (thermoplastic polymer film layer) or thermoplastic fiber glue net, and the interfacial bonding performance is significantly improved.

[0023] The addition of the non-woven fiber mat in the present invention can solve the problem of insufficient tear strength after the composite of high-performance fibers and a thermoplastic polymer matrix. The non-woven material is an isotropic material. By applying the non-woven fiber mat on the surface of the high-performance fabric, stress can be dispersed in multiple axial directions, improving durability and anti-destruction performance, enhancing the anti-tear characteristics, and meeting the application requirements of high tear performance.

[0024] The present invention uses a thermoplastic fiber glue network as the adhesive layer. The thermoplastic fibers are in the micron or sub-micron scale. Under the high-temperature conditions of hot pressing and compounding the high-performance fabric and the thermoplastic fiber glue network, the micron or sub-micron scale thermoplastic fibers melt, which can achieve better penetration of the fiber bundles in the high-performance fiber plain fabric, and then form a better interfacial bond with the high-performance fibers, thereby obtaining high coating adhesion strength. Brief Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of the sandwich fabric with high coating adhesion strength and a gradient interface enhancement structure of the present invention;

[0026] Figure 2 is a schematic diagram of the micro-nano anchor point structure on the surface of the aramid fabric in Example 1 of the present invention;

[0027] Figure 3 is an SEM image of the aramid fabric with a micro-nano structure in Example 1 of the present invention;

[0028] Figure 4 is a schematic diagram of the aramid fiber not treated with alkali solution and organic solvent in Comparative Example 1 of the present invention;

[0029] Figure 5 is an SEM image of the aramid fiber not treated with alkali solution and organic solvent in Comparative Example 1 of the present invention;

[0030] Figure 6 is a schematic structural diagram of the sandwich fabric without a non-woven fiber mat layer in Comparative Example 2 of the present invention;

[0031] Among them, 1. High-performance fabric; 1-1. High-performance fiber; 1-2. Micro-nano anchor point structure on the surface of the high-performance fiber; 2. Thermoplastic fiber glue network 1; 3. Non-woven fiber mat; 4. Thermoplastic fiber glue network 2; 5. Thermoplastic polymer film. Detailed Embodiments

[0032] In the present invention, unless otherwise specified, the required preparation raw materials or reagents are all commercially available products well-known to those skilled in the art.

[0033] The present invention provides a preparation method of a sandwich fabric with high coating adhesion strength and a gradient interface enhancement structure, including the following steps:

[0034] The high-performance fabric is ultrasonically compounded with an alkali solution and an organic solvent for surface roughening treatment to obtain a high-performance fabric with a micro-nano structure; the high-performance fibers used in the high-performance fabric include one or more of aramid fiber, polybenzimidazole fiber, polyimide fiber, polyetheretherketone fiber, and polyhydrazide fiber;

[0035] A first thermoplastic fiber glue net is applied to the surface of the high-performance fabric with a micro-nano structure to obtain a high-performance fabric coated with a fiber glue net;

[0036] After a non-woven fiber felt is applied to the surface of the high-performance fabric coated with a fiber glue net and then subjected to a first hot pressing treatment, a second thermoplastic fiber glue net is applied to the surface of the non-woven fiber felt to obtain a composite net cloth;

[0037] A thermoplastic polymer film is applied to the surface of the composite net cloth and subjected to a second hot pressing treatment to obtain a high-coated adhesion strength sandwich net cloth with a gradient interface enhancement structure.

[0038] In the present invention, the high-performance fabric is ultrasonically compounded with an alkali solution and an organic solvent for surface roughening treatment to obtain a high-performance fabric with a micro-nano structure.

[0039] In the present invention, the high-performance fibers used in the high-performance fabric include one or more of aramid fiber, polybenzimidazole fiber, polyimide fiber, polyetheretherketone fiber, and polyhydrazide fiber, and more preferably aramid fiber; when the high-performance fabric contains two or more of the above fibers, the present invention has no special limitation on the ratio of different types of fibers, and it can be adjusted according to actual needs.

[0040] In the present invention, the parameters of the high-performance fabric preferably include: the areal density is 150~500 g / m 2 , more preferably 240~400 g / m 2 , further preferably 280~300 g / m 2 , the fineness of the filament yarn used is 800~1800 D, more preferably 1000~1500 D, the warp and weft yarn densities are independently 15~30 pieces / inch, more preferably 18~24 pieces / inch, and further preferably 20~22 pieces / inch, and the fabric weave is plain weave or twill weave.

[0041] The present invention has no special limitation on the source of the high-performance fabric, and commercially available products well-known in the art can be used.

[0042] In the present invention, the lye preferably includes one or more of potassium hydroxide solution, sodium hydroxide solution, and ammonia water solution; the organic solvent preferably includes one or more of dimethyl sulfoxide, N-methylpyrrolidone, and N,N-dimethylformamide; the volume ratio of the lye to the organic solvent is preferably 1-3:100, more preferably 2:100, and the concentration of the lye is preferably 0.1-0.2 g / mL, more preferably 0.15 g / mL.

[0043] In the present invention, the time for the surface roughening treatment is preferably 1-4 h, more preferably 1-2 h; the ultrasonic frequency for the ultrasonic compounding is preferably 20-30 kHz, more preferably 20-25 kHz, and the stirring speed is preferably 300-800 rpm, more preferably 500-600 rpm.

[0044] The present invention uses a mixed solution of lye and organic solvent to treat high-performance fabrics. Under the ultrasonic cavitation effect and mechanical stirring, the surface of the high-performance fibers fibrillates, and a fibrillated surface micro-nano anchor structure is formed on the fabric surface to achieve the construction of a micro-nano scale rough structure.

[0045] After obtaining the high-performance fabric with a micro-nano structure, the present invention applies a first thermoplastic fiber glue net on the surface of the high-performance fabric with a micro-nano structure to obtain a high-performance fabric covered with a fiber glue net.

[0046] In the present invention, in terms of mass percentage, the preparation raw materials of the first thermoplastic fiber glue net and the second thermoplastic fiber glue net independently include: ethylene-vinyl acetate copolymer (EVA) 50-70%, polyurethane (PU) 10-20%, and copolyester (Co-PES) 20-30%.

[0047] In the present invention, the first thermoplastic fiber glue net and the second thermoplastic fiber glue net are both preferably prepared by a melt-blown nonwoven forming method. The melt-blown nonwoven forming method of the present invention is preferably as follows: EVA, PU, and Co-PES are uniformly mixed using a twin-screw mixer, and then melt-extruded and formed using a twin-screw extruder to obtain a thermoplastic fiber glue net; the temperature of the feeding section of the twin-screw extruder is 150-170 °C, the temperature of the compression section is 180-200 °C, the temperature of the homogenization section is 200-220 °C, the rotation speed is 100-200 rpm, and the pressure is 5-10 MPa; the diameter of the melt-blown spinneret die is 0.2-0.4 mm, the temperature of the spinneret die is 210-240 °C, the air temperature is 230-270 °C, and the air pressure is 0.6-1.2 MPa. The temperature of the feeding section of the twin-screw extruder is more preferably 160-170 °C, the temperature of the compression section is more preferably 185-190 °C, the temperature of the homogenization section is more preferably 200-210 °C, the rotation speed is more preferably 120-150 rpm, and the pressure is more preferably 8-10 MPa; the diameter of the melt-blown spinneret die is more preferably 0.2-0.3 mm, the temperature of the spinneret die is more preferably 220-230 °C, the air temperature is more preferably 250-260 °C, and the air pressure is more preferably 1 MPa.

[0048] In the present invention, the areal density of the first thermoplastic fiber glue net and the second thermoplastic fiber glue net is independently preferably 30-50 g / m 2 , more preferably 50 g / m 2 . In the present invention, the thermoplastic fiber glue net is used as an adhesive layer, and the areal density of the overall sandwich fabric after lamination is controlled through this areal density.

[0049] The present invention has no special limitation on the application method, and it is only necessary to lay the first thermoplastic fiber glue net on the surface of the high-performance fabric with micro-nano structure.

[0050] In the present invention, the addition amount of the first thermoplastic fiber glue net or the second thermoplastic fiber glue net is preferably adjusted by grammage. Glue nets with different grammages can be produced according to requirements. Multiple layers of low-grammage fiber glue nets can be applied, or a single layer of high-grammage fiber glue net can be applied, preferably to meet the requirements of the coating adhesion strength.

[0051] In the present invention, the first thermoplastic fiber glue net and the second thermoplastic fiber glue net are preferably the same.

[0052] After obtaining the high-performance fabric coated with the fiber glue net, in the present invention, after applying a nonwoven fiber felt on the surface of the high-performance fabric coated with the fiber glue net and performing the first hot pressing treatment, a second thermoplastic fiber glue net is applied on the surface of the nonwoven fiber felt to obtain a composite net fabric.

[0053] In the present invention, the non-woven fiber felt is preferably prepared by a thermo-bonded non-woven forming method from polyester fibers and high-strength fibers. The high-strength fibers preferably include aramid fibers and / or glass fibers. The mass ratio of the polyester fibers to the high-strength fibers is preferably 20:80 to 50:50, more preferably 20:80.

[0054] In the present invention, the polyester fibers and the high-strength fibers are preferably mixed evenly and then subjected to opening, carding, and thermo-bonding in sequence to obtain the non-woven fiber felt. By utilizing the thermoplasticity of the polyester fibers, the polyester fibers are softened or melted by heating to achieve the mutual bonding of the fibers.

[0055] The present invention has no special limitation on the opening and carding, and it can be carried out according to the processes well-known in the art.

[0056] In the present invention, the thermo-roll pressing method is preferably used for thermo-bonding and fixing the polyester fibers and the high-strength fibers. The conditions of the thermo-roll pressing method are preferably as follows: the temperature of the upper roll: 120 - 160 °C, the temperature of the lower roll: 110 - 140 °C, the pressure: 0.5 - 2 MPa. The temperature of the upper roll is more preferably 140 - 160 °C, the temperature of the lower roll is more preferably 120 - 140 °C, and the pressure is more preferably 1.0 - 1.5 MPa.

[0057] In the present invention, the areal density of the non-woven fiber felt is preferably 20 - 60 g / m 2 , more preferably 30 - 50 g / m 2 .

[0058] The present invention has no special limitation on the way of applying the non-woven fiber felt. The non-woven fiber felt can be directly laid on the high-performance fabric coated with a fiber glue net according to the ways well-known in the art.

[0059] In the present invention, the conditions of the first thermo-pressing treatment preferably include: the pressure is 0.5 - 0.8 MPa, more preferably 0.6 - 0.75 MPa; the temperature is 150 - 180 °C, more preferably 150 - 160 °C, and the time is 0.5 - 1 min, more preferably 0.5 - 0.8 min.

[0060] In order to improve the peel strength, a thermoplastic fiber glue net is applied on the surface of the non-woven fiber felt as a melt-blown layer, and the melt-blown layer covers the surface of the non-woven fiber felt.

[0061] After obtaining the composite net cloth, a thermoplastic polymer film is applied on the surface of the composite net cloth and the second thermo-pressing treatment is carried out to obtain the high-coated adhesion strength sandwich net cloth with a gradient interface enhancement structure.

[0062] In the present invention, the thermoplastic polymer film is preferably a PVC film or a TPU film; the areal density of the thermoplastic polymer film is preferably 100 - 300 g / m2 , more preferably 200 - 300 g / m 2 . The present invention uses a thermoplastic polymer film as the surface film material of the sandwich fabric material, so that the sandwich fabric material has waterproof, sealing and decorative properties. The present invention has no special limitation on the thermoplastic polymer film and its source, and any thermoplastic polymer film for sandwich fabric well-known in the art can be used.

[0063] The present invention has no special limitation on the method of applying the thermoplastic polymer film, and the thermoplastic polymer film can be directly laid on the surface of the composite fabric according to the method well-known in the art.

[0064] In the present invention, the conditions of the second hot pressing treatment preferably include: the pressure is 0.5 - 0.8 MPa, more preferably 0.6 - 0.75 MPa; the temperature is 140 - 160 °C, more preferably 145 - 160 °C; the time is 1 - 2 min, more preferably 2 min.

[0065] In the preparation method of the present invention, the surface roughening treatment, applying the first thermoplastic fiber glue net on the surface of the high-performance fabric, applying the non-woven fiber felt on the surface of the high-performance fabric covered with the fiber glue net, applying the second thermoplastic fiber glue net on the surface of the non-woven fiber felt, and applying the thermoplastic polymer film on the surface of the composite fabric are all bilateral surfaces, forming a high-coated adhesion strength sandwich fabric with a gradient interface enhancement structure as Figure 1 shown.

[0066] The present invention provides a high-coated adhesion strength sandwich fabric with a gradient interface enhancement structure prepared by the preparation method described in the above technical solution.

[0067] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention. Example 1

[0068] 1) Aramid fabric is woven with aramid filament yarn, the areal density of the aramid fabric is 280 g / m 2 , the fineness of the filament yarn used is 1000 D, the warp and weft yarn densities are both 22 pieces per inch, and the fabric structure is plain weave;

[0069] The aramid fabric is ultrasonically treated with a mixed solution of potassium hydroxide aqueous solution with a concentration of 0.15 g / mL and dimethyl sulfoxide, the volume ratio of the alkali solution to the organic solvent is 2:100, the treatment time is 1 h, the ultrasonic frequency is 20 kHz, and the magnetic stirring speed is 600 rpm, to obtain an aramid fabric with a micro-nano structure, as Figure 2 shown;

[0070] 2) The nonwoven fiber mat is prepared by a thermal bonding nonwoven forming method. The nonwoven fiber mat is made of polyester fiber and glass fiber, and the mass ratio of polyester fiber to glass fiber is 20:80. The polyester fiber and glass fiber are mixed evenly, and after being opened and carded in sequence, the thermal roll pressing method is used for thermal bonding and net setting. The temperature of the upper roll is 160 °C, the temperature of the lower roll is 140 °C, and the pressure is 1.5 MPa, obtaining the nonwoven fiber mat with a basis weight of 30 g / m 2 ;

[0071] 3) Sizing and compounding: In the thermoplastic fiber glue net, the mass proportion of EVA (molecular weight 25000 g / mol) is 50%, the mass proportion of PU (molecular weight 50,000 g / mol) is 20%, and the mass proportion of Co-PES (molecular weight 30000 g / mol) is 30%. Use a twin-screw mixer to mix EVA, PU, and Co-PES evenly, and perform melt extrusion and forming on a twin-screw extruder. The temperature of the feeding section of the twin-screw extruder: 170 °C, the temperature of the compression section: 185 °C, the temperature of the homogenization section: 210 °C, the rotation speed is 120 rpm, and the pressure is set to 10 MPa; the diameter of the melt spraying spinneret die is 0.2 mm, the temperature of the spinneret die: 230 °C, the air temperature: 250 °C, the air pressure: 1 MPa, obtaining the thermoplastic fiber glue net, as thermoplastic fiber glue net 1 or thermoplastic fiber glue net 2;

[0072] Lay the thermoplastic fiber glue net 1 with a basis weight of 50 g / m 2 on the surface of the aramid fabric with a micro-nano structure. Subsequently, lay the nonwoven fiber mat on the surface of the glue net, and perform the first hot pressing treatment, with a pressure of 0.75 MPa, a temperature of 150 °C, and a time of 0.5 min; Subsequently, lay the thermoplastic fiber glue net 2 with a basis weight of 50 g / m 2 on the surface of the nonwoven fiber mat. The thermoplastic fiber glue net 2 is the same as the thermoplastic fiber glue net 1; Subsequently, lay the PVC film with a basis weight of 200 g / m 2 on the surface of the thermoplastic fiber glue net 2, and perform the second hot pressing treatment, with a pressure of 0.75 MPa, a temperature of 145 °C, and a time of 2 min, completing the compounding to obtain the sandwich fabric with a gradient interface enhanced structure and high coating adhesion strength. Example 2

[0073] 1) Weave an aramid fabric with aramid filaments. The basis weight of the aramid fabric is 300 g / m 2 , the fineness of the used filament yarn is 1500 D, the warp and weft yarn density is 20 pieces per inch, and the fabric structure is plain weave;

[0074] The aramid fabric was ultrasonically treated with a mixed solution of potassium hydroxide aqueous solution with a concentration of 0.15 g / mL and dimethyl sulfoxide. The volume ratio of the alkali solution to the organic solvent was 2:100, the treatment time was 1 h, the ultrasonic frequency was 20 kHz, and the magnetic stirring speed was 600 rpm to obtain an aramid fabric with a micro-nano structure.

[0075] 2) The nonwoven fiber mat was prepared by a thermo-bonding nonwoven forming method. The nonwoven fiber mat was made of polyester fiber and aramid fiber. The mass ratio of polyester fiber to aramid fiber was 20:80. The polyester fiber and glass fiber were mixed evenly, and after being opened and carded in sequence, a thermo-bonding and net-fixing was carried out by a hot roll pressing method. The temperature of the upper roll: 160 °C, the temperature of the lower roll: 140 °C, the pressure: 1.5 MPa, and the areal density of the nonwoven fiber mat was 50 g / m 2 .

[0076] 3) Sizing and compounding: In the thermoplastic fiber glue net, the mass ratio of EVA (molecular weight 25000 g / mol) was 50%, the mass ratio of PU (molecular weight 50,000 g / mol) was 20%, and the mass ratio of Co-PES (molecular weight 30000 g / mol) was 30%. EVA, PU and Co-PES were mixed evenly by a twin-screw mixer, and melt extrusion and forming were carried out in a twin-screw extruder. The temperature of the feeding section of the twin-screw extruder: 170 °C, the temperature of the compression section: 185 °C, the temperature of the homogenization section: 210 °C, the rotation speed 120 rpm, and the pressure was set to 10 MPa; the diameter of the melt-spinning die head was 0.2 mm, the temperature of the die head: 230 °C, the air temperature: 250 °C, the air pressure: 1 MPa to obtain a thermoplastic fiber glue net, which was used as thermoplastic fiber glue net 1 or thermoplastic fiber glue net 2;

[0077] The thermoplastic fiber glue net 1 with an areal density of 50 g / m was laid on the surface of the aramid fabric with a micro-nano structure; then the nonwoven fiber mat was laid on its surface, and after the first hot pressing treatment, the pressure was 0.75 MPa, the temperature was 150 °C, and the time was 0.5 min; then the thermoplastic fiber glue net 2 with an areal density of 50 g / m was laid on the surface of the nonwoven fiber mat. The thermoplastic fiber glue net 2 was the same as the thermoplastic fiber glue net 1; then the PVC film with an areal density of 200 g / m 2 was laid on the surface of the thermoplastic fiber glue net 2, and after the second hot pressing treatment, the pressure was 0.75 MPa, the temperature was 145 °C, and the time was 2 min to complete the compounding and obtain a high-coated adhesion strength sandwich fabric with a gradient interface enhancement structure. 2 2

[0078] Comparative Example 1

[0079] The difference from Example 1 was only that: the aramid fabric was not treated with the alkali solution and the organic solvent, and the aramid fiber structure was as​​Figure 4 as shown

[0080] Comparative Example 2

[0081] The difference from Example 1 is that no non-woven fiber felt layer is provided, including 2 - thermoplastic fiber glue mesh 1 and 5 - PVC film symmetrically arranged in sequence with the aramid fabric as the central layer, and the structure is as Figure 6 shown

[0082] Characterization and performance testing

[0083] 1) Figure 3 This is the SEM image of the aramid fabric with micro-nano structure in Example 1 of the present invention; it can be seen from Figure 3 that micro-nano scale fiber whiskers are formed on the surface of aramid fibers. As the fibrillation surface micro-nano anchor structure, this structure increases the surface roughness of aramid fibers, and can form an interlock with the thermoplastic glue mesh during the forming of the press felt, improving the interfacial bonding effect.

[0084] 2) Figure 5 This is the SEM image of the aramid fiber without being treated with lye and organic solvent described in Comparative Example 1 of the present invention; it can be seen from Figure 5 that the surface of aramid fibers is smooth and there are no attachment points, making it difficult to form a firm interlock with the thermoplastic glue mesh.

[0085] 3) Test the properties of the press felt in Examples 1 - 2 and Comparative Examples 1 - 2:

[0086] Tear strength test: HG_T 2581.1 - 2009 Rubber or plastics coated fabrics - Determination of tear resistance - Part 1: Constant rate of tearing method

[0087] Peel strength test: HG T 3052 - 2008 Rubber or plastics coated fabrics - Determination of adhesion strength of coating

[0088] The test results are shown in Table 1.

[0089] Table 1 Performance data of the press felt in Examples 1 - 2 and Comparative Examples 1 - 2

[0090] Case Tear strength (N) Peel strength (N / 25mm) Example 1 751 63 Example 2 804 65 Comparative Example 1 703 52 Comparative Example 2 527 55

[0091] As can be seen from Table 1, the cross-woven fabric obtained in Example 1 has relatively high tear strength and peel strength; in Example 2, since coarser aramid filament bundles are used for weaving, and the areal density of the prepared aramid fabric is relatively higher than that in Example 1, and a non-woven fiber felt with a higher areal density is used as the reinforcing layer, the tear resistance of the prepared cross-woven fabric is improved, and there is no significant difference in the peel strength compared with Example 1; in Comparative Example 1, the aramid fabric is not treated with alkali solution and organic solvent, the surface of the aramid fiber is smooth, and the bonding strength between the aramid fiber and the thermoplastic fiber glue mesh is relatively weak, which not only affects the peel strength, but also the insufficient interfacial strength causes the fiber to debond from the thermoplastic fiber glue mesh during the tearing process of the cross-woven fabric, thereby reducing the tear resistance; in Comparative Example 2, no non-woven fiber felt layer is provided, and the tear resistance of the cross-woven fabric is mainly borne by the aramid fabric layer. Since the aramid fabric is woven by warp and weft interlacing spinning, after being compounded with the thermoplastic fiber glue mesh and PVC, when the cross-woven fabric bears the tearing load, stress concentration is likely to occur at the tear opening, resulting in insufficient tearing performance. Since the aramid fabric is treated with alkali solution and organic solvent, the peel strength of Comparative Example 2 is improved compared with that of Comparative Example 1.

[0092] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a high coating bonding strength sandwich fabric with a gradient interface enhancement structure, characterized in that: The following steps are involved: The high-performance fabric is subjected to ultrasonic treatment with alkali solution and organic solvent to perform surface roughening treatment to obtain a high-performance fabric with a micro-nano structure; the high-performance fiber used in the high-performance fabric includes one or more of aramid fiber, polybenzimidazole fiber, polyimide fiber, polyetheretherketone fiber and polyhydrazide fiber; Applying a first thermoplastic fiber adhesive web on the surface of the high-performance fabric having the micro-nano structure to obtain a high-performance fabric covered with the fiber adhesive web; After applying a non-woven fiber felt to the surface of the high-performance fabric covered with the fiber glue web, a first heat pressing treatment is performed, and then a second thermoplastic fiber glue web is applied to the surface of the non-woven fiber felt to obtain a composite mesh; Applying a thermoplastic polymer film on the surface of the composite mesh cloth and performing a second hot pressing treatment to obtain a mesh cloth with a high coating bonding strength and a gradient interface enhancement structure; The sandwich fabric is composed of multiple layers of materials, including a high-performance fabric as a central layer, a thermoplastic fiber rubber net 1, a non-woven fiber felt, a thermoplastic fiber rubber net 2 and a thermoplastic polymer film layer symmetrically arranged in sequence; The alkali solution includes one or more of potassium hydroxide solution, sodium hydroxide solution and ammonia solution; the organic solvent includes one or more of dimethyl sulfoxide, N-methylpyrrolidone and N,N-dimethylformamide; The volume ratio of the alkali solution to the organic solvent is 1-3:100, and the concentration of the alkali solution is 0.1-0.2 g / mL; The surface roughening treatment time is 1-4 hours; the ultrasonic frequency of the ultrasonic treatment is 20-30 kHz, and the stirring speed is 300-800 rpm; The nonwoven fiber felt is prepared by thermally bonding polyester fiber and high-strength fiber in a nonwoven molding method, wherein the high-strength fiber includes aramid fiber and / or glass fiber, the mass ratio of the polyester fiber to the high-strength fiber is 20:80-50:50, and the surface density of the nonwoven fiber felt is 20-60 g / m 2 .

2. The preparation method according to claim 1, characterized in that: The parameters of the high performance fabric include: surface density of 150-500 g / m 2 The filament yarn used is 800~1800D, the warp and weft yarn densities are 15~30 yarns / inch respectively, and the fabric structure is plain or twill.

3. The preparation method according to claim 1, characterized in that: The surface density of the first thermoplastic fiber rubber web and the second thermoplastic fiber rubber web is independently 30-50 g / m 2 .

4. The preparation method according to claim 1 or 3, characterized in that: The first thermoplastic fiber rubber web and the second thermoplastic fiber rubber web are both prepared by melt-blown nonwoven molding.

5. The preparation method according to claim 4, characterized in that: Calculated by mass percentage, the raw materials for preparing the first thermoplastic fiber adhesive web and the second thermoplastic fiber adhesive web include: 50-70% ethylene-vinyl acetate copolymer, 10-20% polyurethane and 20-30% copolyester.

6. The preparation method according to claim 1, characterized in that: The conditions of the first hot pressing treatment include: pressure of 0.5-0.8 MPa, temperature of 150-180°C, and time of 0.5-1 min; The conditions of the second hot pressing treatment include: a pressure of 0.5-0.8 MPa, a temperature of 140-160° C., and a time of 1-2 min.

7. A mesh cloth with high coating adhesion strength and having a gradient interface enhancement structure prepared by the preparation method according to any one of claims 1 to 6.

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