High-toughness plant fiber non-woven fabric based on ternary synergistic cross-linked network and preparation method of high-toughness plant fiber non-woven fabric

Abstract

The tensile strength of the high-toughness plant fiber non-woven fabric is larger than or equal to 20 MPa, the elongation at break of the high-toughness plant fiber non-woven fabric is larger than or equal to 25%, and the 24-hour water absorption rate of the high-toughness plant fiber non-woven fabric is smaller than or equal to 40%; the plant fiber non-woven fabric is prepared by dipping a plant fiber non-woven fabric in a mixed aqueous solution containing polyvinyl alcohol, cellulose nanofibers and citric acid and carrying out heat treatment. According to the preparation method, a plurality of carboxyl groups on citric acid molecules and hydroxyl groups on polyvinyl alcohol chains, on the surfaces of cellulose nanofibers and on plant fiber matrixes are subjected to esterification reaction to form a compact ternary synergistic cross-linked network, so that the mechanical property and the water resistance of the plant fiber non-woven fabric are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer composite materials technology, specifically relating to a method and product for significantly improving the mechanical properties and water resistance of plant fiber nonwoven fabrics by constructing a ternary synergistic crosslinking network through polyvinyl alcohol (PVA), cellulose nanofibers (CNF) and citric acid (CA). Background Technology

[0002] Plant fiber nonwoven fabrics have attracted much attention due to their biodegradability and environmental friendliness; however, their inherent weaknesses, such as poor mechanical strength, high brittleness, and poor water resistance, severely limit their applications. Current modification methods are mostly physical blending or simple coating, such as CN 113398661A which discloses treating nonwoven fabrics sequentially in polydopamine (PDA) and a PVA solution containing ZIF-8. However, these methods have the following drawbacks: 1. Weak interfacial bonding: The physical layered structure is easily peeled off, and functional components are easily detached.

[0003] 2. Limited performance improvement: It is difficult to significantly improve strength, toughness and water resistance at the same time.

[0004] 3. Insufficient environmental friendliness: Uses non-degradable synthetic polymers or toxic cross-linking agents (such as glutaraldehyde).

[0005] Therefore, developing a modification method that can form a robust, integrated structure and possess both high performance and green characteristics has become a pressing technical challenge in this field. Summary of the Invention

[0006] To address the above shortcomings, this invention aims to provide a plant fiber nonwoven fabric that can form a stable, integrated structure and possesses both high performance and entirely green characteristics, as well as a method for modifying it.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A high-strength and tough plant fiber nonwoven fabric based on a ternary synergistic cross-linking network has a tensile strength ≥20 MPa, an elongation at break ≥25%, and a 24-hour water absorption rate ≤40%.

[0008] The method for preparing the high-strength and tough plant fiber nonwoven fabric involves impregnating the plant fiber nonwoven fabric in a mixed aqueous solution containing polyvinyl alcohol (PVA), cellulose nanofibers (CNF), and citric acid (CA), followed by heat treatment to form a ternary synergistic cross-linked network in the plant fiber nonwoven fabric; specifically, it includes the following steps: 1) The plant fiber nonwoven fabric is pretreated by soaking in an alkaline solution to activate its surface; 2) Prepare a mixed aqueous solution containing PVA, CNF, and CA; 3) Immerse the pretreated plant fiber nonwoven fabric from step 1) into the mixed aqueous solution prepared in step 2), and control the liquid content by impregnation-rolling. 4) The impregnated plant fiber nonwoven fabric is then heat-treated to cause the hydroxyl groups of CA and PVA, CNF and the plant fibers in the nonwoven fabric to undergo esterification reaction, forming a dense ternary synergistic cross-linked network.

[0009] Further, the alkaline solution mentioned in step 1) is a 2-10 wt% sodium hydroxide solution.

[0010] Furthermore, the soaking temperature in step 1) is 50-80℃, and the soaking time is 0.5-2 h.

[0011] Further, in step 2), the concentration of PVA in the mixed aqueous solution is 30-80 g / L, the concentration of CNF is 5-30 g / L, and the concentration of CA is 10-50 g / L.

[0012] Furthermore, in step 2), the liquid carryover rate is controlled between 60% and 120%.

[0013] Further, the heat treatment in step 3) is performed at a temperature of 120-150°C for a time of 5-30 minutes.

[0014] The high-strength and tough plant fiber nonwoven fabric can be used in environmentally friendly packaging materials, medical dressing substrates, biodegradable agricultural covering materials, food contact grade packaging liners, and flexible substrates for wearable electronic devices.

[0015] The beneficial effects of this invention are as follows: This invention utilizes the multiple carboxyl groups present on the citric acid molecule to undergo esterification reactions with the hydroxyl groups present on the polyvinyl alcohol chain, the surface of cellulose nanofibers, and the plant fiber matrix itself, thereby constructing a unique "ternary synergistic crosslinking network" on plant fiber nonwoven fabric, which can effectively improve the mechanical properties and water resistance of plant fiber nonwoven fabric. Attached Figure Description

[0016] Figure 1 The figures show the FTIR spectra of pure plant fiber nonwoven fabric, PVA, CNF, CA, and the products obtained in the experimental examples. The figures demonstrate that the plant fiber nonwoven fabric prepared in the examples contains crosslinks of PVA, CNF, and CA.

[0017] Figure 2 The images show a comparison of the SEM microstructures of the experimental example and comparative examples 1 and 2. As can be seen from the images, a continuous and dense cross-linked film is formed on the surface of the plant fiber nonwoven fabric prepared in the examples.

[0018] Figure 3The figures show the stress-strain curves of the examples and comparative examples 1-4. As can be seen from the figures, the plant fiber nonwoven fabrics prepared in the examples possess both high strength and high toughness. Detailed Implementation

[0019] A high-strength and tough plant fiber nonwoven fabric based on a ternary synergistic crosslinking network is prepared by the following steps: 1) Immerse the plant fiber nonwoven fabric in a 2-10 wt% sodium hydroxide solution at 50-80℃ for 0.5-2 h to activate it; 2) Prepare a mixed aqueous solution containing 30-80 g / L polyvinyl alcohol (PVA), 5-30 g / L cellulose nanofibers (CNF), and 10-50 g / L citric acid (CA); 3) Immerse the pretreated plant fiber nonwoven fabric from step 1) into the mixed aqueous solution prepared in step 2), and control the liquid retention rate to 60%-120% by impregnation-roll-drying. 4) Heat-treat the impregnated plant fiber nonwoven fabric at 120-150℃ for 5-30 min to form a high-strength and tough plant fiber nonwoven fabric with a dense ternary synergistic cross-linked network.

[0020] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0021] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods. Example

[0022] 1. Pretreatment: Immerse 100g of wood pulp nonwoven fabric in a 5wt% NaOH solution, treat at 60℃ for 1 hour, then wash and dry.

[0023] 2. Preparation of the mixture: Dissolve 6g PVA, 1g CNF and 1.5g CA in deionized water and bring the volume to 100g.

[0024] 3. Impregnation and drying: The pretreated wood pulp nonwoven fabric is impregnated with the prepared mixture, and the liquid content is controlled to 80% by using a roller.

[0025] 4. Heat treatment: The impregnated wood pulp nonwoven fabric is heat-treated in a 130℃ forced-air drying oven for 15 minutes to complete the cross-linking reaction and obtain the final product.

[0026] Comparative Example 1 The use of CA is omitted; other operations are the same as in the example.

[0027] Comparative Example 2 The use of CNF is omitted; other operations are the same as in the example.

[0028] Comparative Example 3 The use of PVA is omitted; other operations are the same as in the example.

[0029] Comparative Example 4 In step 3, the prepared mixture is evenly coated onto the surface of the pretreated wood pulp nonwoven fabric, with the coating amount being 80% of the mass of the wood pulp nonwoven fabric. Other operations are the same as in the example.

[0030] Comparative Example 5 Equal amounts of glutaraldehyde, borax, adipic acid, and phytic acid were used to replace CA, and other operations were the same as in the example.

[0031] 1. Triadic Synergistic Effect Table 1

[0032] As shown in Table 1, compared with the comparative example, the product prepared in the example achieved amazing tensile strength (25.0 MPa) and water resistance (35% water absorption) while maintaining high toughness (30% elongation at break), which fully demonstrates that PVA, CNF and CA produce a synergistic reinforcing effect.

[0033] 2. Comparison of different crosslinking agents Table 2

[0034] As shown in Table 2, while products prepared using glutaraldehyde exhibit good mechanical and water resistance properties, they are highly toxic and cause the material to become non-degradable. Products prepared using borax crosslinking have extremely poor water resistance (90% water absorption rate) and are unsuitable for humid environments. In contrast, products prepared using citric acid demonstrate better overall performance. Therefore, in balancing the multiple conflicting goals of high strength, high water resistance, high toughness, and complete biodegradability, inexpensive, safe, and environmentally friendly citric acid is key to achieving optimal overall performance.

[0035] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A high-strength and tough plant fiber nonwoven fabric based on a ternary synergistic cross-linking network, characterized in that, Its tensile strength is ≥20 MPa, elongation at break is ≥25%, and water absorption rate is ≤40% after 24 hours.

2. A method for preparing a high-strength, high-toughness plant fiber nonwoven fabric as described in claim 1, characterized in that, Plant fiber nonwoven fabric is impregnated in a mixed aqueous solution containing polyvinyl alcohol, cellulose nanofibers and citric acid, and then taken out and subjected to heat treatment to form a ternary synergistic cross-linked network in the plant fiber nonwoven fabric.

3. The preparation method according to claim 2, characterized in that, The plant fiber nonwoven fabric needs to be soaked and activated in an alkaline solution before use.

4. The preparation method according to claim 3, characterized in that, The alkaline solution is a 2-10 wt% sodium hydroxide solution.

5. The preparation method according to claim 3, characterized in that, The soaking and activation process is carried out at a temperature of 50-80℃ for 0.5-2 hours.

6. The preparation method according to claim 2, characterized in that, The concentration of polyvinyl alcohol in the mixed aqueous solution is 30-80 g / L, the concentration of cellulose nanofibers is 5-30 g / L, and the concentration of citric acid is 10-50 g / L.

7. The preparation method according to claim 2, characterized in that, The degree of impregnation of plant fiber nonwoven fabric in the mixed aqueous solution should be such that the liquid retention rate of the impregnated plant fiber nonwoven fabric is controlled at 60%-120%.

8. The preparation method according to claim 2, characterized in that, The heat treatment is performed at a temperature of 120-150℃ for 5-30 minutes.

9. The application of the high-strength and tough plant fiber nonwoven fabric as described in claim 1 as an environmentally friendly packaging material, medical dressing substrate, biodegradable agricultural covering material, food contact grade packaging liner, or flexible substrate for wearable electronic devices.

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