Cattail-leaf-like degradable flexible composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of non-woven materials, and particularly relates to a cattail-leaf-like degradable flexible composite material and a preparation method and application thereof. The preparation method comprises the following steps: firstly, by taking polylactic acid, paraffin and inorganic particles as raw materials, preparing a superfine fiber main body material with an oriented structure through a melt-blowing process; viscose fibers and polyvinyl alcohol fibers are used as raw materials, and the viscose / polyvinyl alcohol fiber framework material is prepared through the processes of opening treatment, cross lapping and needling net fixing. The main body material and the framework material are compounded through a spunlace net fixing process to prepare the polylactic acid flexible composite material; the cattail-leaf-like degradable flexible composite material is obtained after the composite material is subjected to water etching finishing. The cattail-leaf-like degradable flexible composite material disclosed by the invention has excellent waterproof and breathable characteristics, radiation cooling characteristics and mechanical characteristics, and shows a wide application prospect in the field of protective materials.

Description

Technical Field

[0001] This invention belongs to the technical field of nonwoven materials, specifically relating to a cattail leaf-like biodegradable flexible composite material, its preparation method, and its application. Background Technology

[0002] With social development and the improvement of people's living standards, people have increasingly higher requirements for personal protection in outdoor activities, medical care, and special protection. Protective materials, as the basic materials in the field of protection, are being used extensively.

[0003] In recent years, extreme weather events have become more frequent globally, with summer temperatures repeatedly exceeding 40°C and lasting longer. People face the threat of high temperatures when engaging in outdoor activities or working for extended periods. Prolonged exposure to high temperatures makes heat protection crucial for safeguarding the lives and health of outdoor workers. Traditional protective materials, such as GORE-TEX fabric, can block rainwater penetration while allowing sweat vapor to escape, making them suitable for outdoor clothing and keeping outdoor workers dry and comfortable in damp environments. Sunscreen fabrics, with their excellent UV protection properties, can block harmful UV rays from damaging the skin and are used in outdoor sun hats and sun-protective clothing, reducing the risk of sunburn and tanning. However, these materials still cannot meet the growing demands for heat protection.

[0004] Medical protective materials are directly related to the health and safety of medical staff, patients, and the public. Therefore, stringent requirements are placed on the protective performance, biosafety, comfort, and practicality of these materials. Common examples include medical masks, which are mostly made of three-layer spunbond nonwoven materials. These masks effectively filter bacteria, viruses, and dust from the air, serving as the last line of defense against cross-infection between patients and medical staff. They are widely used in medical environments and during outbreaks of infectious diseases such as influenza. Medical protective clothing, on the other hand, often uses breathable, waterproof, and antibacterial materials to effectively block viruses, bacteria, and harmful chemicals, protecting medical staff from infection and harm when in contact with patients and handling medical waste. However, these materials have limitations in terms of softness and breathability.

[0005] Specialty protective materials are high-performance protective materials used in specific hazardous environments or high-risk scenarios. Examples include chemical protective suits used in chemical production, and multifunctional integrated materials that combine waterproofing, fireproofing, breathability, and softness for military protection or emergency safety rescue. Currently, they are rapidly developing towards high performance, intelligentization, and environmental friendliness.

[0006] Furthermore, traditional protective materials are mostly based on petroleum-based raw materials such as PP, PE, and PET. Petroleum is a non-renewable fossil energy source with limited reserves; with long-term large-scale extraction, resources face the risk of depletion. Petroleum-based raw materials are energy-intensive to process, and the products are difficult to degrade, causing environmental pollution. Therefore, finding a biodegradable fiber material for protective applications has become a hot topic in various protective fields.

[0007] In nature, the surfaces of plants such as cattail leaves, lotus leaves, and rice exhibit micro- and nano-papillary structures, parallel vein structures, and multi-layered cross-sections. The papillary and parallel vein structures reduce the contact area with water, resulting in a contact angle far exceeding 90°, effectively shielding the liquid. Furthermore, the parallel vein structure significantly scatters and reflects solar radiation, reducing heat absorption, while the multi-layered cross-section effectively provides radiative cooling, thus maintaining a relatively stable leaf temperature, which is beneficial for normal leaf growth and the maintenance of physiological functions.

[0008] Therefore, it is of great significance to develop a biomimetic textile material based on the structure of cattail leaves, which is a biodegradable, waterproof and breathable fiber material. This biomimetic textile material is safe and pollution-free, lightweight and comfortable, with high mechanical strength and efficient thermal management performance, and is of great significance for personal protection, outdoor protection, medical protection and special protection. Summary of the Invention

[0009] Based on this, the purpose of this invention is to provide a method for preparing a cattail-leaf-like biodegradable flexible composite material. This method uses biodegradable polylactic acid (PLA) microfibers as the main body, with a viscose and polyvinyl alcohol combed fiber web as the skeleton, and employs a hydroentangled flexible composite reinforcement technology to obtain a flexible PLA fiber material. Then, the flexible PLA fiber material is water-etched and finished to prepare a cattail-leaf-like biodegradable flexible composite material.

[0010] This invention also provides a cattail-like biodegradable flexible composite material prepared by the above method and its application in outdoor protection, medical protection and special protection.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a biodegradable flexible composite material resembling cattail leaves, comprising the following steps: S1 is an ultrafine fiber material with an oriented structure, prepared by melt-blowing process using polylactic acid, paraffin and inorganic particles as raw materials. S2 is a viscose / polyvinyl alcohol fiber skeleton material prepared by opening treatment, cross-laying and needle punching and fixing processes using viscose fiber and polyvinyl alcohol fiber as raw materials. S3, using the oriented structure of ultrafine fiber material as the upper and lower layers, and the viscose / polyvinyl alcohol fiber skeleton material as the middle layer, stacking them into a three-layer structure along the thickness direction, and then preparing polylactic acid flexible composite material by hydroentanglement web forming process. S4. After water etching treatment, the polylactic acid flexible composite material is used to prepare a cattail leaf-like biodegradable flexible composite material.

[0012] Furthermore, the meltblown process parameters described in S1 are as follows: die head temperature 215~230 ℃, hot air temperature 250~270 ℃, hot air pressure 35~42 kPa, screw extruder zone one temperature 170~190 ℃, zone two temperature 210~220 ℃, and zone three temperature 215~230 ℃.

[0013] Furthermore, the mass ratio of polylactic acid, paraffin and inorganic particles in S1 is 94~98:1~3:1~3, and the inorganic particles are obtained by mixing silicon dioxide and aluminum oxide in a mass ratio of 3~7:7~3.

[0014] Furthermore, the needle punching frequency of the needle punching and bonding process described in S2 is 22~30 Hz; the mass ratio of the viscose fiber and polyvinyl alcohol fiber is 3~7:7~3.

[0015] Furthermore, the hydroentangled web-forming process parameters described in S3 are: hydroentanglement pressure of 130~170 bar and fabric speed of 3~7 m / min.

[0016] Furthermore, the water etching finishing process described in S4 is as follows: the polylactic acid flexible composite material is immersed in a sodium hydroxide aqueous solution at 45±5 ℃, dispersed under ultrasonic vibration for 1~2 hours, taken out, rinsed with water and dried to obtain the final product; the mass fraction of the sodium hydroxide aqueous solution is 0.8~1.2%.

[0017] The present invention further provides a method for preparing the above-mentioned cattail leaf-like biodegradable flexible composite material to obtain the cattail leaf-like biodegradable flexible composite material.

[0018] Furthermore, the biodegradable flexible composite material resembling cattail leaves exhibits excellent thermal management performance, with a cooling effect superior to ordinary fabrics; it also boasts superior waterproof and breathable properties, with a porosity of 87-43%, an air permeability of 244-350 mm / s, and a water contact angle of 132-141°.

[0019] Furthermore, the biodegradable flexible composite material resembling cattail leaves exhibits superior mechanical properties, with a bursting strength of 40-81 N and a softness score of 70-85.

[0020] The present invention further provides an application of the above-mentioned cattail leaf-like biodegradable flexible composite material in outdoor protection, medical protection and special protection.

[0021] The beneficial effects of this invention are: 1. The method for preparing the biodegradable flexible composite material resembling cattail leaves provided by the present invention preferably employs melt-blown molding process, carding molding process, cross-laying and needle-punching composite process, hydroentangled flexible composite reinforcement process and water etching finishing process. The biomimetic textile material is prepared through the synergistic effect between the various processes. The preparation process is simple, the equipment is highly versatile, the cost is low and the efficiency is high, and it is suitable for industrial-scale production.

[0022] 2. The biodegradable flexible composite material resembling cattail leaves provided by this invention utilizes biomimetic design to innovate the structural design of composite materials, exhibiting a clear cattail leaf-like structure with a tight outer layer and a loose inner layer. Multiple scattering effects between fibers enhance the overall thermal management capability of the material and improve its overall mechanical properties. Among them, the paraffin hydrophobic modification of the outer polylactic acid ultrafine fiber material and the deposition of inorganic particles construct a multi-scale rough surface structure, giving it excellent waterproof performance and efficient radiative cooling performance.

[0023] 3. The cattail leaf-like biodegradable flexible composite material provided by the present invention has an outer layer mainly composed of biodegradable polylactic acid microfibers. The fiber diameter is normally distributed in the range of 1~7 μm, and the orientation angle is concentrated in the range of -30~30°. The microfibers and polyvinyl alcohol fiber skeleton are reinforced by hydroentangling technology, which gives it excellent softness and comfort, with a softness score of 70~85. It also has high-efficiency waterproof and breathable performance, with a water contact angle of 132~141° and a breathability of 244~350mm / s.

[0024] 4. The biodegradable flexible composite material resembling cattail leaves provided by this invention, with its biomimetic innovative structural design principle of being tight on the outside and loose on the inside, overcomes the shortcomings of polylactic acid's high brittleness and obtains excellent mechanical properties, with a bursting strength of 40~81 N.

[0025] 5. The cattail-leaf-like biodegradable flexible composite material provided by this invention has excellent cooling effect, an emissivity of 97%, and can withstand sunlight intensity of 887 W / m². 2 At that time, the cooling effect of the sample was nearly 15 °C higher than that of ordinary cotton fabric.

[0026] 6. The cattail-like biodegradable flexible composite material provided by this invention can be widely used in outdoor protection, medical protection, and special protection. Attached Figure Description

[0027] To more clearly illustrate the technical solution of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Appendix Figure 1 Electron micrograph of a cattail leaf; among which Figure 1 a is an electron micrograph of the surface of a cattail leaf. Figure 1 b is an electron microscope image of a cross-section of a cattail leaf.

[0029] Appendix Figure 2 These are cross-sectional electron microscope images of different polyvinyl alcohol ratios in the cattail-leaf-like biodegradable flexible composite material of this invention; wherein, Figure 2 a is a cross-sectional electron micrograph of the adhesive:polyvinyl alcohol ratio of 3:7. Figure 2 b is a cross-sectional electron microscope image of the adhesive:polyvinyl alcohol ratio of 4:6. Figure 2 c is a cross-sectional electron microscope image of the adhesive:polyvinyl alcohol ratio of 5:5. Figure 2 d is a cross-sectional electron micrograph of the adhesive:polyvinyl alcohol ratio of 6:4. Figure 2 e is a cross-sectional electron microscope image of the adhesive:polyvinyl alcohol ratio of 7:3. Figure 2 f is a pore size distribution diagram of the cattail leaf-like biodegradable flexible composite material under different polyvinyl alcohol ratios; Appendix Figure 3 The structural characteristics of a biodegradable flexible composite material resembling cattail leaves; among which, Figure 3 Image a is an electron microscope image of the surface of the cattail-like biodegradable flexible composite material. Figure 3 b is a diameter distribution diagram of the cattail-like biodegradable flexible composite material. Figure 3 c is the orientation angle distribution diagram of the cattail-like biodegradable flexible composite material; Appendix Figure 4 The results are EDS test results for the cattail-leaf-like biodegradable flexible composite material; among them, Figure 4 Image a is an electron micrograph of the overall elemental distribution of the cattail-like biodegradable flexible composite material. Figure 4 b is an electron micrograph showing the distribution of carbon elements. Figure 4 c is an electron micrograph showing the distribution of O element. Figure 4 d is an electron micrograph of the Al elemental distribution. Figure 4 e is an electron micrograph showing the distribution of Si elements. Figure 4 f is the element distribution curve; Appendix Figure 5 The waterproof properties of the biodegradable flexible composite material resembling cattail leaves; among which, Figure 5 a is a three-dimensional distribution diagram of the cattail-like biodegradable flexible composite material. Figure 5 b shows the water contact angle of the cattail-like biodegradable flexible composite material under different hydroentangling pressures. Figure 5 c represents the water contact angle diagram of different polyvinyl alcohol ratios in the cattail-like biodegradable flexible composite material; Appendix Figure 6 The optical properties of the biodegradable flexible composite material resembling cattail leaves; among which, Figure 6 a is the infrared spectrum of the cattail-like biodegradable flexible composite material. Figure 6b is the emissivity diagram of the cattail-like biodegradable flexible composite material under different hydroentanglement pressures. Figure 6 c represents the reflectance of the cattail-like biodegradable flexible composite material under different hydroentanglement pressures. Figure 6 d represents the reflectance of the biodegradable flexible composite material with different polyvinyl alcohol ratios; Appendix Figure 7 The radiative cooling properties of the biodegradable flexible composite material resembling cattail leaves; among which, Figure 7 a is a solar irradiance map. Figure 7 b is a radiation cooling graph of the cattail-like biodegradable flexible composite material under different hydroentangling pressures. Figure 7 c is a radiation cooling graph of different polyvinyl alcohol ratios in the cattail-like biodegradable flexible composite material; Appendix Figure 8 The mechanical properties of biodegradable flexible composite materials resembling cattail leaves; among which, Figure 8 Figure a shows the longitudinal tensile fracture diagram of the cattail-like biodegradable flexible composite material under different hydroentangling pressures. Figure 8 b shows the transverse tensile fracture diagram of the cattail-like biodegradable flexible composite material under different hydroentangling pressures. Figure 8 c is the bursting diagram of the cattail-like biodegradable flexible composite material under different hydroentanglement pressures; Figure 8 d shows the longitudinal tensile fracture diagram of the cattail-like biodegradable flexible composite material with different polyvinyl alcohol ratios. Figure 8 e shows the transverse tensile fracture diagram of the biodegradable flexible composite material resembling cattail leaves with different polyvinyl alcohol ratios. Figure 8 f represents the bursting curves of different polyvinyl alcohol ratios in the cattail-like biodegradable flexible composite material. Appendix Figure 9 The soft and comfortable properties of the biodegradable flexible composite material, resembling cattail leaves; among which, Figure 9 Figure a shows the test results for the softness properties of the cattail-leaf-like biodegradable flexible composite material. Figure 9 b is a graph showing the flexibility score of the cattail-like biodegradable flexible composite material under different hydroentanglement pressures. Figure 9 c is a softness score graph of different polyvinyl alcohol ratios in the cattail leaf-like biodegradable flexible composite material; Appendix Figure 10 The permeability of the biodegradable flexible composite material resembling cattail leaves; among which, Figure 10 Figure a shows the water vapor permeation test process of the cattail-like biodegradable flexible composite material. Figure 10 b is the air-moisture permeability diagram of the cattail-like biodegradable flexible composite material under different hydroentanglement pressures. Figure 10 c is the air-moisture permeability diagram of different polyvinyl alcohol ratios in the cattail-like biodegradable flexible composite material. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All mentioned embodiments are implemented based on the technical solutions of the present invention, and detailed implementation processes are given. However, it should be stated that the scope of protection of the present invention is not limited to the following embodiments.

[0031] The cattail-leaf-like biodegradable flexible composite material in this invention is prepared using polylactic acid, paraffin wax, and inorganic particles as raw materials. A highly oriented ultrafine fiber matrix material is obtained through melt-blown in-situ stretching molding. A viscose / polyvinyl alcohol fiber mesh skeleton material is prepared using viscose fiber and polyvinyl alcohol fiber as raw materials through carding, cross-laying, and needle-punching processes. The highly oriented ultrafine fiber matrix material is then used as the upper and lower layers, and the viscose / polyvinyl alcohol fiber mesh skeleton material is used as the middle layer. These three layers are stacked sequentially from top to bottom along the thickness direction and then subjected to a hydroentanglement experimental system for composite processing to prepare the polylactic acid flexible composite material. After water etching finishing, a biodegradable flexible composite material with a cattail-leaf-like structure is prepared.

[0032] The melt-blowing process used to prepare the highly oriented ultrafine fiber main material has the following preferred settings: die temperature 215-230 ℃, hot air temperature 250-270 ℃, hot air pressure 35-42 kPa, screw extruder zone 1 temperature 170-190 ℃, zone 2 temperature 210-220 ℃, and zone 3 temperature 215-230 ℃. Polylactic acid, paraffin wax, and inorganic particles are mixed evenly and then prepared into an ultrafine fiber web through a melt-blowing experimental system. The fiber web is stretched and oriented by adjusting the speed difference between the winding roller and the receiving screen in the melt-blowing experimental system. The receiving screen speed is 4-6 Hz, and the winding screen speed is 3-5 Hz. The preferred mass ratio of polylactic acid, paraffin wax and inorganic particles is 94~98:1~3:1~3, and the inorganic particles are a mixture of silicon dioxide and alumina, with the preferred mass ratio of silicon dioxide and alumina being 3:7, 4:6, 5:5, 6:4 or 7:3.

[0033] The preparation of viscose / polyvinyl alcohol (PVA) fiber mesh skeleton material employs an opening treatment, cross-laying, and needle-punching process. Specifically, viscose and PVA fibers of a certain mass ratio are manually opened and mixed evenly. The mixture is then fed into a carding machine, where it is carded and peeled by cylinder rollers, doffer rollers, and peeling rollers to form a loosely structured viscose / PVA primary fiber web. This web is then conveyed to a laying curtain, where layers are stacked to form a viscose / PVA fiber web of a certain thickness. Finally, under the action of needles, the viscose fibers move downwards and entangle with the PVA fibers, obtaining the viscose / PVA fiber mesh skeleton material. Preferably, the needle-punching frequency of the needle-punching process is 22-30 Hz. The preferred mass ratio of viscose fiber to PVA fiber is 3:7, 4:6, 5:5, 6:4, or 7:3.

[0034] The three-layer composite polylactic acid flexible composite material is prepared using a hydroentangled web bonding process, with the preferred hydroentanglement pressure being 130~170 bar and the fabric speed being 3~7 m / min.

[0035] The water etching finishing process used to prepare the biodegradable flexible composite material with a cattail leaf structure is preferably a process in which the polylactic acid flexible composite material is immersed in a sodium hydroxide aqueous solution at 45±5 ℃, dispersed under ultrasonic vibration for 1~2 h, taken out, rinsed with clean water and dried; the mass fraction of the sodium hydroxide aqueous solution is 0.8~1.2%.

[0036] The following Examples 1 to 21 detail the implementation processes of the technical solutions of the present invention. Unless otherwise specified, the experimental methods used in the following experimental examples are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0037] Example 1 (1) Using polylactic acid, paraffin wax, and inorganic particles as raw materials, a highly oriented first-layer (upper layer) and third-layer (lower layer) ultrafine fiber material was prepared by melt-blowing molding process: Polylactic acid, paraffin wax, and inorganic particles were mixed evenly and then ultrafine fiber web was prepared by melt-blowing experimental system. The fiber web was stretched to achieve orientation by adjusting the speed difference between the receiving roller and the receiving screen in the melt-blowing experimental system. The melt-blowing process parameters were: die temperature 225 ℃, hot air temperature 260 ℃, hot air pressure 39 kPa, screw extruder zone 1 temperature 180 ℃, zone 2 temperature 215 ℃, and zone 3 temperature 225 ℃. The mass ratio of polylactic acid, paraffin wax, and inorganic particles was 97:3:3, and the mass ratio of silica particles to alumina particles in the inorganic particles was 5:5.

[0038] (2) Using viscose fiber and polyvinyl alcohol fiber in a mass ratio of 3:7 as raw materials, after opening treatment, a second layer (intermediate layer) of viscose / polyvinyl alcohol fiber skeleton with adjustable pore structure was prepared by carding and forming process and needle punching and web-bonding process. The needle punching process parameters are: the needle punching frequency of the needle punching and web-bonding technology is 26 Hz.

[0039] (3) The first, second, and third layers of fiber materials were stacked along the thickness direction and composited using a hydroentangled web forming process to prepare a flexible polylactic acid composite material. The hydroentanglement process parameters were: hydroentanglement pressure of 150 bar and fabric speed of 5 m / min. Under the impact of high-pressure water jet, the number of flexible entanglements between the multilayer fibers increased, the material structure became more complete, and the flexible polylactic acid composite material was finally obtained.

[0040] (4) The polylactic acid flexible composite material was water-etched at 45 °C to obtain a cattail leaf-like biodegradable flexible composite material. The water etching process was as follows: the polylactic acid flexible composite material was first immersed in a sodium hydroxide solution with a solute mass fraction of 1% in distilled water at 45 °C, dispersed under ultrasonic vibration for 1.5 h, rinsed with clean water, and then dried in a dryer; the porosity of the cattail leaf-like biodegradable flexible composite material was 65%.

[0041] Examples 2, 3, 4, and 5 In this set of examples, the preparation of the cattail-like biodegradable flexible composite material differs from that in Example 1 in that the mass ratios of viscose fiber and polyvinyl alcohol used are 4:6, 5:5, 6:4, and 7:3, respectively.

[0042] Examples 6, 7, 8, and 9 In this set of embodiments, the preparation of the cattail-like biodegradable flexible composite material differs from that in Example 1 in that the hydroentanglement pressure used in the hydroentanglement web-forming process is 130 bar, 140 bar, 160 bar, and 170 bar, respectively.

[0043] Examples 10, 11, 12, and 13 In this set of embodiments, the preparation of the cattail leaf-like biodegradable flexible composite material differs from that in Example 1 in that the mass ratio of silicon dioxide to aluminum oxide in the inorganic particles used in the meltblown process is 3:7, 4:6, 6:4 and 7:3, respectively.

[0044] Examples 14, 15, 16, and 17 In this set of embodiments, the difference between the preparation of the cattail-like biodegradable flexible composite material and that in Example 1 is that the acupuncture frequency used in the acupuncture process is 22~30 Hz, specifically 22 Hz, 24 Hz, 28 Hz and 30 Hz.

[0045] The morphology, elemental distribution, waterproof properties, optical properties, radiative cooling properties, mechanical properties, softness, and permeability of the biodegradable flexible composite materials prepared in Examples 1 to 17 were tested and analyzed, as follows: 1. Morphological structure According to GB / T 36422-2018 "Determination of Microstructure and Diameter of Chemical Fibers by Scanning Electron Microscopy", the morphology and structure of cattail leaves and cattail-like biodegradable flexible composite materials were observed and electron micrographs were taken using a scanning electron microscope (JSM-IT200, JEOL Ltd., Japan). The images were then analyzed using Smile View Map software (V9.3, JEOL Ltd., Japan) to obtain fiber diameter and three-dimensional structural diagrams. Before testing, the samples were sputtered with gold using an ion sputtering instrument (SBC-12, Beijing Zhongke Keyi Technology Development Co., Ltd.). According to GB / T 21650.3-2011 "Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Intrusion Porosimetry and Gas Adsorption Method", the pore size distribution of the materials was tested using a pore size analyzer (PSM 165, Topas Ltd., Germany).

[0046] Figures 1-4 The present invention describes the biodegradable flexible composite material resembling cattail leaf prepared by the present invention and the morphological and structural characteristics of cattail leaf. Figure 1 The image shows that the surface of the cattail leaf is composed of parallel vein sequences formed by the overlapping of primary and secondary veins of varying thicknesses. Figure 1 a) The cross-section exhibits an integrated structure that is tight on the outside and loose on the inside. Figure 1 (b) is the structural basis for its excellent self-cleaning properties and outstanding mechanical strength. Based on the multi-layered structure of cattail leaves, Figure 2 a~2f show the cross-sectional morphology of the material under different polyvinyl alcohol (PVA) ratios. It can be seen that as the PVA ratio decreases, the arrangement of the second-layer PVA skeleton fibers becomes more compact, and the inter-fiber porosity gradually decreases, exhibiting a gradually decreasing cattail-like structural characteristic. Furthermore, combined with... Figure 2 The f-pore size distribution curve also shows that as the proportion of polyvinyl alcohol decreases, the pore size of the cattail-like biodegradable flexible composite material gradually shifts towards a smaller structural size. When the ratio of adhesive to polyvinyl alcohol is 3:7, the median pore size reaches its maximum of 46.9 μm. Figure 3The image shows the surface structure characteristics of the cattail-leaf-like biodegradable flexible composite material. Fibers with diameters ranging from 1 to 7 μm interconnect and exhibit a highly oriented longitudinal arrangement, resembling a cattail leaf structure. 80.16% of these fibers have an orientation angle between -30° and 30°, providing a structural basis for improved waterproofing. Notably, EDS testing results show that inorganic silica and alumina particles are uniformly distributed on the material surface, indicating successful loading onto the cattail-leaf-like biodegradable flexible composite material surface and improving surface roughness. Figure 4 ).

[0047] 2. Waterproof properties According to DB44 / T 1872-2016 "Determination of Wetting Properties of Textile Surfaces - Contact Angle Method", the water contact angle and roll-off angle of the samples were tested using an SDC-350 liquid contact angle measuring instrument (Dongguan Shengding Precision Instrument Co., Ltd.). The test liquid was distilled water, with a liquid volume of 3 μL for the water contact angle test and 30 μL for the roll-off angle test.

[0048] Figure 5 The image shows the three-dimensional structure and water contact angle of the cattail-like biodegradable flexible composite material prepared in this invention. Figure 5 Figure a shows a three-dimensional structural diagram of the cattail-leaf-like biodegradable flexible composite material prepared in Example 3. The figure shows that, thanks to the addition of inorganic particles, the surface roughness of the material is improved, thereby reducing the contact area with the liquid and enhancing its waterproof properties. Figure 5 Figures b and 5c show the water contact angle curves of the cattail-like biodegradable flexible composite material prepared according to this invention. The figures show that the water contact angles of the cattail-like biodegradable flexible composite material are all higher than 130°, indicating that the material has excellent waterproof performance. Simultaneously, the figures also show that the water contact angle gradually increases with increasing hydroentanglement pressure. Specifically, when the hydroentanglement pressure is 130 bar, the water contact angle is 132°; when the hydroentanglement pressure increases to 141°, this is because the increased hydroentanglement pressure leads to more entanglement points between fibers, thereby increasing the material roughness. Conversely, as the proportion of polyvinyl alcohol decreases, the water contact angle gradually decreases. This is because the increased number of viscose fibers enhances the material's adsorption force on the liquid, resulting in a gradual decrease in the water contact angle.

[0049] 3. Optical properties The infrared spectra, absorbance, and emissivity of the samples were measured using a Fourier transform infrared spectrometer (Nicolet 6700, Thermo Fisher, USA) with an integrating sphere. The reflectance of the samples was measured using a UV-Vis spectrophotometer (Colori5, X-rite, USA).

[0050] Figure 6 The figures shown are the emissivity and reflectivity diagrams of the cattail-leaf-like biodegradable flexible composite material prepared according to the present invention. Figure 6 As shown in Figure a, the material exhibits a distinct absorption peak near the "atmospheric window" of 8–14 μm, specifically at 757 cm⁻¹. -1 860 cm -1 1080 cm -1 1180 cm -1 These correspond to CH, C-C, and CO bonds, respectively. This phenomenon indicates that the material possesses excellent high infrared emission characteristics. Figure 6 b shows the emissivity curves of the material under different hydroentangling pressures. As the hydroentangling pressure increases, the overall trend of emissivity change is not significant, reaching a maximum of 97%. This phenomenon indicates that the material has excellent infrared radiation capability in the atmospheric window, enabling it to efficiently pass through the atmosphere and thus reduce temperature. Figure 6 Images c and 6d show the reflectance of the cattail-like biodegradable flexible composite material with different hydroentangling pressures and polyvinyl alcohol (PVA) ratios. The reflectance gradually increases with increasing hydroentangling pressure, reaching a maximum of 91.6% at 170 bar. This is because increasing the hydroentangling pressure leads to a more stable multilayer structure and a more significant scattering of visible light. Conversely, the reflectance gradually decreases with decreasing PVA ratio. This is because the increased number of viscose fibers reduces the material's porosity, resulting in a slight decrease in visible light scattering.

[0051] 4. Radiative cooling characteristics The radiation cooling capability of the cattail leaf-like biodegradable flexible composite material was tested using a self-built radiation cooling test device. The self-built radiation cooling test device consisted of a closed microenvironment composed of a foam box wrapped in aluminum foil. A 10 cm × 10 cm square test hole was opened at the top of the foam box. The test sample was covered on the test hole, and finally covered with a layer of polyester film to isolate the interference of the external environment. The temperature change inside the microenvironment was monitored using a multi-channel temperature tester (JK808, Changzhou, Jiangsu, China). Cotton fabric was used as a control sample and tested under the same test conditions.

[0052] Figure 7 The figure shows the solar irradiance and the radiation cooling test curves of the cattail-leaf-like biodegradable flexible composite material prepared according to this invention. The figure shows that, compared with the control sample cotton cloth, this material can significantly reduce the temperature inside the microenvironment. The solar intensity gradually increases from 10:00 to 13:20, and correspondingly, the temperature inside the microenvironment of each material also increases. This stage is the heating stage for each material, and the temperature of the prepared cattail-leaf-like biodegradable flexible composite material is still lower than that of the control sample during this stage. As the solar intensity reaches 887 W / m², the temperature decreases further. 2The temperature difference between the sample prepared in the example and the control sample can reach nearly 15 °C.

[0053] 5. Mechanical properties According to GB / T 24218.3-2010 Textiles - Test Methods - Part 3: Determination of breaking strength and elongation at break (strip method), the longitudinal and transverse tensile properties of the samples were tested using a nonwoven material isothermal mechanical property analyzer (HD026S-100, Nantong Hongda Experimental Instrument Co., Ltd.). Test conditions: sample size 20 cm × 5 cm, clamping distance 100 mm, tensile speed 100 mm / min.

[0054] According to GB / T 24218.5-2016 Textiles - Nonwovens - Test Methods - Part 5: Determination of Mechanical Penetration Resistance (Steel Ball Bursting Test) . Bursting performance: The bursting strength of the sample was tested using a fabric tensile testing machine (YG026MD-250, Darong Textile Instrument Co., Ltd.). Test conditions: Sample size was 100 cm. 2 .

[0055] Figure 8 The figure shows the tensile fracture curve and bursting curve of the cattail leaf-like biodegradable flexible composite material prepared in this invention. Figure 8 As shown in figures a~8c, as the hydroentangling pressure increases from 130 bar to 170 bar, the longitudinal breaking strength, transverse breaking strength, and bursting strength all exhibit similar changing patterns, showing a trend of first increasing and then decreasing. The maximum values ​​are reached at a hydroentangling pressure of 160 bar, at 38 N, 37 N, and 82 N, respectively. This phenomenon may be due to increased fiber slippage and entanglement as the hydroentangling pressure increases, resulting in enhanced mechanical properties. However, excessive hydroentangling pressure damages the fiber structure, weakening its resistance to deformation. Furthermore, as the polyvinyl alcohol content decreases, the mechanical properties of the cattail-like biodegradable flexible composite material show a gradual increasing trend. This is because a denser interlayer structure enhances the material's resistance to external forces.

[0056] 6. Soft and comfortable properties According to GB / T 39371-2020 "Determination of Softness in Physical and Mechanical Tests of Leather", the softness and smoothness scores of the samples were tested using a Fibre Tester (F1S3-10, Nu Cybertek). The sample size was 100 cm. 2 A circle.

[0057] Figure 9The figure shows the softness and smoothness scores of the cattail-leaf-like biodegradable flexible composite material prepared according to the present invention. As shown, the material exhibits excellent softness properties, specifically: when the hydroentanglement pressure is 130 bar, 140 bar, 150 bar, 160 bar, and 170 bar, the softness scores are 70, 77, 80, 88, and 85, respectively, and the smoothness scores are 70, 71, 72, 73, and 72, respectively. This result is closely related to the hydroentanglement flexible entanglement process of polylactic acid microfibers. Furthermore, with the decrease in the proportion of polyvinyl alcohol, the softness and smoothness scores show a slight decrease, decreasing by 2.38% and 2.82%, respectively.

[0058] 7. Transparency According to GB / T 24218.15-2018 Textiles - Nonwovens - Test Methods - Part 15: Determination of Air Permeability, the air permeability of the samples was tested using a fully automatic air permeability meter (YG416E-Ⅲ, Ningbo Textile Instrument Factory). Test conditions: pressure difference between the upper and lower surfaces of the material was 100 Pa, and the sample area was 100 cm². 2 .

[0059] According to GB / T12704.1—2009 Textiles - Test methods for moisture permeability of fabrics - Part 1: Moisture absorption method, the water vapor transmission rate of the samples was tested using a cup-type water vapor transmission rate tester (W3, Jinan Langguang Electromechanical Technology Co., Ltd.).

[0060] Figure 10 The diagram shows the permeability characteristics of the cattail-leaf-like biodegradable flexible composite material prepared according to the present invention. Figure 10 a shows the water evaporation test process of the sample prepared in Example 1 on a hot stage at 100 °C. It can be seen that as the test time increases, the liquid height in the beaker decreases significantly, which indicates that the material exhibits excellent air permeability. Figure 10 b and 10c show that as the hydroentanglement pressure increases from 130 bar to 170 bar, the air permeability and water vapor transmission rate increase from 350 mm / s and 8322 g / (m²) respectively. 2 *24h) and 244 mm / s and 4457 g / (m 2 *24h), this result is closely related to the hydroentanglement process of polylactic acid microfibers. The reason for this phenomenon is that as the hydroentanglement pressure increases, the number of entanglements between fibers increases, the porosity decreases, and the material structure becomes more compact, thereby reducing the water vapor transport channels.

[0061] In summary, this invention provides a method for preparing a cattail-leaf-like biodegradable flexible composite material. This method can produce a fully biodegradable fiber material with a cattail-leaf-like structure. This material also has excellent waterproof and breathable properties, radiative cooling properties, and mechanical properties, showing broad application prospects in the field of protective materials.

[0062] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a biodegradable flexible composite material resembling cattail leaves, characterized in that, Includes the following steps: S1 is an ultrafine fiber material with an oriented structure, prepared by melt-blowing process using polylactic acid, paraffin and inorganic particles as raw materials. S2 is a viscose / polyvinyl alcohol fiber skeleton material prepared by opening treatment, cross-laying and needle punching and fixing processes using viscose fiber and polyvinyl alcohol fiber as raw materials. S3, using the oriented structure of ultrafine fiber material as the upper and lower layers, and the viscose / polyvinyl alcohol fiber skeleton material as the middle layer, stacking them into a three-layer structure along the thickness direction, and then preparing polylactic acid flexible composite material by hydroentanglement web forming process. S4. After water etching treatment, the polylactic acid flexible composite material is used to prepare a cattail leaf-like biodegradable flexible composite material.

2. The method for preparing the cattail-leaf-like biodegradable flexible composite material as described in claim 1, characterized in that, The meltblown process parameters described in S1 are as follows: die temperature 215~230 ℃, hot air temperature 250~270 ℃, hot air pressure 35~42 kPa, screw extruder zone 1 temperature 170~190 ℃, zone 2 temperature 210~220 ℃, and zone 3 temperature 215~230 ℃.

3. The method for preparing the cattail-leaf-like biodegradable flexible composite material as described in claim 1, characterized in that, The mass ratio of polylactic acid, paraffin wax and inorganic particles in S1 is 94~98:1~3:1~3, and the inorganic particles are obtained by mixing silicon dioxide and aluminum oxide in a mass ratio of 3~7:7~3.

4. The method for preparing the cattail-leaf-like biodegradable flexible composite material as described in claim 1, characterized in that, The needle punching frequency of the needle punching and web-bonding process described in S2 is 22~30 Hz; the mass ratio of viscose fiber to polyvinyl alcohol fiber is 3~7:7~3.

5. The method for preparing the cattail-leaf-like biodegradable flexible composite material as described in claim 1, characterized in that, The hydroentangled web-forming process parameters described in S3 are: hydroentanglement pressure of 130~170 bar and fabric speed of 3~7 m / min.

6. The method for preparing the cattail-leaf-like biodegradable flexible composite material as described in claim 1, characterized in that, The water etching finishing process described in S4 is as follows: the polylactic acid flexible composite material is immersed in a sodium hydroxide aqueous solution at 45±5 ℃, dispersed under ultrasonic vibration for 1~2 hours, taken out, rinsed with water and dried to obtain the final product; the mass fraction of the sodium hydroxide aqueous solution is 0.8~1.2%.

7. A biodegradable flexible composite material resembling cattail leaf prepared using the preparation method of any one of claims 1-6.

8. The biodegradable flexible composite material resembling cattail leaves as described in claim 7, characterized in that, It has excellent thermal management performance and a cooling effect higher than ordinary fabrics; it also has excellent waterproof and breathable performance, with a porosity of 87~43%, an air permeability of 244~350 mm / s, and a water contact angle of 132~141°.

9. The cattail-leaf-like biodegradable flexible composite material as described in claim 7, characterized in that, It has excellent mechanical properties, with a bursting strength of 40~81 N and a softness score of 70~85.

10. The application of the cattail-leaf-like biodegradable flexible composite material according to any one of claims 7-9 in outdoor protection, medical protection and special protection.

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