High-toughness and high-ductility degradable insulating paper and preparation method thereof

Abstract

The application discloses a kind of high toughness high ductility degradable insulating paper and preparation method thereof, belong to electrical insulation material technical field.The insulating paper is composed of 35-65wt% plant fiber, 15-45wt% polylactic acid, 3-15wt% biobased toughening agent and 0.5-5wt% nanocellulose, by wet forming and hot-pressing process composite formation three-dimensional network structure, so that its breaking elongation is greater than or equal to 15%, tensile index is greater than or equal to 100N·m / g.The preparation method includes: fiber defibration pulping, mixed with PLA emulsion and other components, is formed by copying and is cured by hot-pressing.The application solves the problems of traditional insulating paper, such as brittleness, poor ductility and insufficient toughness of pure PLA, through multi-component synergy and process innovation.The product has excellent mechanical properties, insulation and degradability, and is suitable for flexible electronics and green power equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical insulation materials, in particular to a high-toughness and high-ductility degradable insulation paper and a preparation method thereof. BACKGROUND

[0002] Insulation paper, as a key insulation material for power equipment and electronic components, is widely used in devices such as transformers, cables, capacitors, etc. Currently, commercial insulation paper is mainly made of wood pulp fibers, which has good insulation performance, but its elongation at break is usually less than 5%, showing obvious brittleness. This inherent brittleness makes the material prone to micro-cracks under bending, vibration or thermal stress, ultimately leading to a decline in insulation performance and even failure.

[0003] In recent years, with the development of emerging technologies such as flexible electronics and wearable devices, higher requirements have been placed on the mechanical properties of insulation materials, especially in terms of toughness and ductility. At the same time, under the background of global promotion of sustainable development, the development of environmentally friendly degradable insulation materials to replace traditional petroleum-based plastics (such as PET, PP, etc.) has become an important development direction for the industry.

[0004] Polylactic acid (PLA) is a biobased degradable material that is considered a potential alternative to traditional insulation materials. However, pure PLA material has inherent brittleness, poor impact resistance, and is difficult to meet the application requirements of high toughness and high ductility. Although the flexibility can be improved by adding plasticizers, this method often significantly reduces the tensile strength, insulation performance and thermal stability of the material, and also poses a risk of plasticizer migration. In addition, simple physical blending processes are difficult to form a strong interfacial bond between plant fibers and the PLA matrix, resulting in poor overall performance of the composite material.

[0005] Therefore, developing an insulation paper product that can simultaneously achieve high toughness, high ductility, excellent insulation performance and complete degradability, and establishing an efficient and reliable preparation method, has become a technical problem that needs to be solved in the field. SUMMARY

[0006] In view of the brittleness, low elongation at break of existing insulation paper, and the difficulty of degradable insulation materials to balance high toughness, high ductility and good insulation performance, the present application provides a high-toughness and high-ductility degradable insulation paper and a preparation method thereof. The insulation paper realizes the effective unification of mechanical properties, insulation performance and degradability through specific component ratio and process design.

[0007] The detection standards used in the embodiments of the present application are as follows:

[0008] Tensile index, tested according to GB / T 12914 standard;

[0009] elongation at break, tested according to GB / T 12914 standard;

[0010] insulation strength, tested according to GB / T 1408.1 standard;

[0011] biodegradation rate, tested according to ISO 14855 standard, weight loss rate under 58℃ composting condition for 90 days.

[0012] To solve the above technical problems, the present application adopts the following technical solutions:

[0013] In a first aspect, the present application provides a high-toughness and high-ductility degradable insulation paper, which is composed of 35-65wt% plant fibers, 15-45wt% polylactic acid, 3-15wt% bio-based toughening agent, and 0.5-5wt% nanocellulose; wherein the plant fibers, polylactic acid, bio-based toughening agent, and nanocellulose are compounded by wet forming and hot pressing process to form a three-dimensional network structure; the elongation at break of the insulation paper is greater than or equal to 15%, and the tensile index is greater than or equal to 100N·m / g.

[0014] Further, the plant fibers are selected from at least one of hemp pulp fibers, wood pulp fibers, or regenerated cellulose fibers, and the average fiber length is 0.5-3.0mm.

[0015] Further, the bio-based toughening agent is selected from at least one of epoxy soybean oil, acrylated castor oil, or polycaprolactone diol.

[0016] Further, the nanocellulose is cellulose nanofiber or cellulose nanocrystal, with a diameter of 10-100nm and an aspect ratio greater than 50.

[0017] Further, the insulation paper has an insulation strength greater than or equal to 10kV / mm.

[0018] Further, the insulation paper has a biodegradation weight loss rate greater than or equal to 30% under standard composting conditions within 90 days.

[0019] In a second aspect, the present application provides a method for preparing a high-toughness and high-ductility degradable insulation paper, which is characterized by comprising the following steps:

[0020] S1. Fiber pretreatment: disperse the plant fibers in water to form a fiber suspension with a mass concentration of 0.5-2.0%;

[0021] S2. Mixing modification: add polylactic acid emulsion, bio-based toughening agent, and nanocellulose to the fiber suspension obtained in step S1, and stir at a speed of 300-800rpm for 20-60 minutes to obtain a mixed slurry;

[0022] S3. Sheet forming: the mixed slurry is vacuum filtered to remove water, with a vacuum degree of -0.06 to -0.09 MPa, to form a wet paper web;

[0023] S4. Hot-pressing and curing: the wet paper web is hot-pressed at a temperature of 80-150 DEG C and a pressure of 1-5 MPa for 5-30 minutes to obtain the degradable insulation paper.

[0024] Further, the preparation method of the polylactic acid emulsion in step S2 is as follows: polylactic acid particles are dissolved in dichloromethane or chloroform, an emulsifier is added, and an oil-in-water emulsion with a solid content of 10-30% is formed by high-speed shearing emulsification.

[0025] Further, the hot-pressing and curing in step S4 adopts a programmed temperature and pressure, specifically including: pre-pressing at 80-100 DEG C and 1-2 MPa for 2-10 minutes, and main pressing at 120-150 DEG C and 3-5 MPa for 3-20 minutes.

[0026] Further, after step S4, there is a curing treatment step S5: the hot-pressed insulation paper is cured at 50-80 DEG C for 2-12 hours. Further improve the stability of product performance.

[0027] Compared with the prior art, the technical scheme of the present application has the following beneficial technical effects:

[0028] The present application breaks through the technical bottleneck that the strength and toughness of traditional insulation materials are difficult to be considered together, and makes the product have high strength characteristics of tensile index ≥ 100 N·m / g while realizing excellent ductility of elongation at break ≥ 15%; through component design and process optimization, it has an insulation strength of ≥ 10 kV / mm, fully meets the requirements of electrical insulation applications, and all components are derived from biodegradable materials, with a degradation rate of more than 30% within 90 days under standard composting conditions, realizing the perfect unity of high performance and environmental protection characteristics; the integrated process of wet forming and hot-pressing curing combines the technical advantages of traditional papermaking process and polymer material composite processing, and the components in the system play a synergistic effect, the plant fiber provides skeleton support, the polylactic acid forms a continuous matrix, the biobased toughening agent improves the toughness of the material, and the nanocellulose enhances the interface bonding, which produces a significant synergistic effect, which is the core innovation of the present application. In summary, through the innovative design of the material system and the systematic optimization of the preparation process, the present application provides a solution to the technical problems existing in traditional insulation materials, and has a wide application prospect in the fields of flexible electronics and green power equipment. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 This is a flowchart of the insulating paper preparation process of the present invention; Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0031] This embodiment provides a high-toughness, high-ductility biodegradable insulating paper, specifically composed of 50wt% hemp pulp fiber, 30wt% polylactic acid, 15wt% epoxidized soybean oil, and 5wt% cellulose nanofibers. The hemp pulp fiber is high-quality hemp pulp conforming to GB / T 26710 standards, with an average fiber length of 2.1±0.3mm and an α-cellulose content ≥85%. The polylactic acid has an optical purity ≥98% and a melt index of 8g / 10min. The epoxidized soybean oil has an epoxy value ≥6.2% and an acid value ≤0.5mg KOH / g. The cellulose nanofibers have a diameter of 20-50nm, a length of 1-3μm, an aspect ratio >100, and a crystallinity ≥75%.

[0032] The preparation process is as follows:

[0033] (1) In the fiber pretreatment stage, 50g of hemp pulp fiber was placed in a standard de-fiber machine, 5L of deionized water (conductivity ≤5μS / cm) was added, and the fiber was de-fibered at 3000rpm for 15 minutes at 25℃ until the fiber was completely dispersed without clumping, forming a uniform fiber suspension with a mass concentration of 1wt%.

[0034] (2) Preparation of polylactic acid emulsion: 30g of polylactic acid particles and 200mL of dichloromethane were stirred and dissolved in a 50℃ water bath for 30 minutes. 3g of Span-80 emulsifier was added and the mixture was transferred to a high-speed shear emulsifier and emulsified at 10000rpm for 15 minutes. At the same time, 500mL of deionized water was slowly added dropwise to form a stable oil-in-water emulsion with a solid content of 20% and a particle size distribution of 0.5-2μm.

[0035] (3) Mixing modification process: The above polylactic acid emulsion, 15g of epoxidized soybean oil and 5g of cellulose nanofibers are added to the fiber suspension in sequence. Under constant temperature of 25℃, the mixture is stirred at 500rpm for 40 minutes with a mechanical stirrer to ensure that each component is fully mixed and the interface modification is completed, so as to obtain a uniform and stable mixed slurry.

[0036] (4) In the papermaking process, the mixed pulp is quantitatively poured into a standard papermaking machine (forming area 0.02m²), and filtered and dehydrated for 5 minutes under a constant vacuum of -0.08MPa to form a wet paper web with a basis weight of 80g / m² and a moisture content of 75%.

[0037] (5) Hot pressing and curing process: Transfer the wet paper web to a flatbed hot press and perform hot pressing and curing according to the following procedure:

[0038] Pre-compression stage: Maintain at 90℃ and 1.5MPa pressure for 5 minutes to complete preliminary molding and moisture evaporation;

[0039] Main pressure stage: Heat to 130℃ and maintain pressure at 4MPa for 10 minutes to achieve complete curing;

[0040] Cooling phase: Cool down to 50°C at a rate of 5°C / min and then depressurize.

[0041] The curing process involves placing the hot-pressed insulating paper in a forced-air oven at 65±2℃ for 6 hours, followed by equilibration under standard temperature and humidity conditions (23℃, 50%RH) for 24 hours to obtain the final product.

[0042] The product has a typical three-dimensional interpenetrating network structure, in which hemp pulp fiber forms the main skeleton, polylactic acid-epoxy soybean oil composite phase forms a continuous matrix, and cellulose nanofibers build a reinforcing network in the interface region, forming strong chemical bonds and physical entanglements between the components.

[0043] The final product will undergo sample testing and mechanical property testing (tensile index and elongation at break).

[0044] Insulating paper samples were cut to standard sizes and equilibrated under constant temperature and humidity conditions for 24 hours. They were then mounted on a materials testing machine (Instron 3365) and stretched at a constant rate until fracture. The maximum tensile strength and elongation were automatically recorded, and the tensile index and elongation at break were calculated. For insulation strength testing, a high-voltage breakdown tester (LDJ-50kV) was used. The electrode system consisted of 25mm diameter ball electrodes, with a voltage ramp rate of 1kV / s. The sample was placed between the electrodes and immersed in transformer oil. The voltage was ramped at a constant rate until the sample broke down, and the breakdown voltage was recorded to calculate the insulation strength. For biodegradability testing, precisely weighed samples were mixed with compost inoculum. The composting temperature was 58±2℃, and the relative humidity was 50-55%. The samples were cultured in a controlled composting device for 90 days, with regular monitoring of carbon dioxide release. After the test, the remaining samples were removed, cleaned, dried, and weighed to calculate the mass loss rate. The original test data were statistically analyzed, outliers were removed, and the arithmetic mean was taken. The calculation results were retained to three significant figures, and the uncertainty was controlled within ±5%. The test results show that the tensile index of the product in Example 1 reached 125 N·m / g, the elongation at break reached 19.5%, the insulation strength was 13.2 kV / mm, and the 90-day biodegradation rate reached 48%. Example 2

[0045] This embodiment provides a high-toughness, high-ductility biodegradable insulating paper, specifically composed of 60wt% softwood pulp fiber, 25wt% polylactic acid, 12wt% acrylated castor oil, and 3wt% cellulose nanocrystals. The softwood pulp fiber has an average fiber length of 2.8±0.4mm. The polylactic acid has an optical purity ≥96% and a melt index of 12g / 10min. The acrylated castor oil has a viscosity of 3500mPa·s and an acid value ≤1mg KOH / g. The cellulose nanocrystals have a diameter of 10-30nm, a length of 100-300nm, and an aspect ratio of 15-25.

[0046] The preparation process is as follows:

[0047] (1) Fiber pretreatment stage: 60g of softwood pulp fiber is placed in a standard desolvation machine, 6L of deionized water (conductivity ≤5μS / cm) is added, and desolvation is carried out at 2800rpm for 12 minutes at 25℃ to form a uniform fiber suspension with a mass concentration of 1wt%. The pH value of the suspension is controlled at 6.5-7.0.

[0048] (2) Preparation of polylactic acid emulsion: 25g of polylactic acid particles and 180mL of chloroform (analytical grade) were stirred and dissolved in a water bath at 45℃ for 25 minutes. 2.5g of Tween-80 emulsifier was added and the mixture was transferred to a high-speed shear emulsifier and emulsified at 8000rpm for 12 minutes. At the same time, 400mL of deionized water was slowly added dropwise to form an oil-in-water emulsion with a solid content of 25% and a particle size distribution of 0.8-3μm.

[0049] (3) Mixing modification process: The above polylactic acid emulsion, 12g acrylate castor oil and 3g cellulose nanocrystals are added to the fiber suspension in sequence. Under constant temperature of 25℃, the mixture is stirred at 400rpm for 50 minutes with a mechanical stirrer to ensure that each component is fully mixed and uniform.

[0050] (4) In the paper forming process, the mixed pulp is quantitatively poured into a standard paper forming machine (forming area 0.02m²), and filtered and dehydrated for 6 minutes under a constant vacuum of -0.07MPa to form a wet paper web with a basis weight of 85g / m² and a moisture content of 78%.

[0051] (5) Hot pressing curing process: transfer the wet paper web to the flatbed hot press, adopt the single-stage hot pressing process, hot pressing temperature 120℃, hot pressing pressure 3MPa, hot pressing time 15 minutes, and release pressure after natural cooling to 60℃.

[0052] The main difference between this embodiment and Embodiment 1 is that softwood pulp fiber is used instead of hemp pulp fiber, acrylic castor oil is used as a toughening agent, cellulose nanocrystals are selected instead of nanofibers, a single-stage hot pressing process is adopted, and the curing treatment is omitted, resulting in relatively low production costs.

[0053] The product exhibits typical composite material characteristics: the microstructure consists of interwoven coniferous pulp fibers forming a main skeletal network with a certain directionality in fiber arrangement, but the network structure is relatively loose. The composite phase formed by polylactic acid and acrylated castor oil exhibits a discontinuous coating state on the fiber surface, with localized polymer enrichment. Cellulose nanocrystals are dispersed in the matrix in the form of dots or short rods, mainly distributed on the fiber surface and pore regions, with good dispersion uniformity, but the reinforcing effect is limited by their morphology. The interfacial bonding between the fibers and the polymer matrix is ​​moderate, with slight debonding observed at some interfaces. The internal pore size distribution of the material is relatively wide, and the pore shape is mostly irregular elliptical, forming a well-connected pore structure. This microstructure corresponds to the simplified process used in Example 2. Although the structural density is not as high as in Example 1, it still ensures good overall performance of the material, while having significant advantages in terms of production cost and process efficiency.

[0054] Similarly, the final product was sampled and tested. The tensile index of the product in Example 2 was 108 N·m / g, the elongation at break was 16.5%, the insulation strength was 12.0 kV / mm, and the biodegradability rate reached 42% after 90 days.

[0055] Comparative Example 1

[0056] This comparative example uses a traditional plant fiber insulating paper preparation method, specifically consisting of 100 wt% softwood pulp fiber, without the addition of any polymers, toughening agents, or nanocellulose reinforcing materials. The average fiber length of the softwood pulp fiber is 2.8 ± 0.4 mm.

[0057] The preparation process is as follows:

[0058] (1) In the fiber pretreatment stage, 100g of softwood pulp fiber was placed in a standard desolvation machine, 10L of deionized water (conductivity ≤5μS / cm) was added, and the fiber was desolvated at 3000rpm for 15 minutes at 25℃ to form a uniform fiber suspension with a mass concentration of 1wt%. The pH value of the suspension naturally stabilized at 6.8-7.2.

[0059] (2) In the paper forming process, the fiber suspension is quantitatively poured into a standard paper forming machine (forming area 0.02m²), and filtered and dehydrated for 8 minutes under a constant vacuum of -0.06MPa to form a wet paper web with a basis weight of 80g / m² and a moisture content of 80%.

[0060] (3) Drying process: The wet paper web is transferred to an electric heating drying oven and dried at 105±2℃ for 2 hours. Then it is equilibrated at standard temperature and humidity conditions (23℃, 50%RH) for 24 hours to obtain a traditional plant fiber insulating paper sample.

[0061] Traditional plant fiber insulating paper exhibits a typical microstructure of cellulose materials. Pure wood pulp fibers intertwine to form a relatively dense but simple network structure. The fibers are mainly bonded by hydrogen bonds, lacking a polymer interface phase. The surface is rough, with obvious fiber fuzzing. The pore structure is simple, the bonding force between fibers is weak, and interface separation occurs.

[0062] The final product was sampled and tested. Comparative Example 1: Traditional plant fiber insulating paper has a tensile index of 85 N·m / g, an elongation at break of only 4.5%, an insulation strength of 8.0 kV / mm, and a biodegradability rate of 80% after 90 days.

[0063] Comparative Example 2

[0064] This comparative example uses pure polylactic acid (PLA) material to prepare an insulating film. Specifically, the raw material composition is 100 wt% PLA, without the addition of any plant fibers, toughening agents, or nanocellulose reinforcing materials. The PLA (same specifications as in Example 1) has an optical purity of ≥98% and a melt flow index of 8 g / 10 min.

[0065] The preparation process is as follows:

[0066] (1) Raw material pretreatment: Dry polylactic acid particles in a vacuum oven at 80°C for 4 hours to ensure that the moisture content is less than 0.05% and prevent hydrolysis and degradation during processing.

[0067] (2) The melt plasticizing process is carried out using a twin-screw extruder.

[0068] (3) Casting film formation process, which prepares thin films by using a precision casting machine.

[0069] (4) Post-processing step: The obtained film is heat-treated at 50°C for 30 minutes to eliminate internal stress, and then equilibrated at standard temperature and humidity conditions (23°C, 50%RH) for 24 hours.

[0070] The pure PLA film exhibits a typical homogeneous polymer structure with a smooth and flat surface, no fiber reinforcement, and a typical brittle fracture characteristic. It has no multiphase interface structure and is a single homogeneous system. Stress whitening areas and radial cracks are visible on the fracture surface.

[0071] Similarly, the final product was sampled and tested. The tensile index of the pure PLA film in Comparative Example 2 was 45 N·m / g, the elongation at break was 6.0%, the insulation strength was 15.0 kV / mm, and the biodegradation rate after 90 days was only 10%.

[0072] Comparative Example 3

[0073] This comparative example aims to verify the key role of nanocellulose in composite materials. The specific raw material composition ratio is 55wt% hemp pulp fiber, 32wt% polylactic acid, 13wt% epoxidized soybean oil, and 0wt% nanocellulose. The raw material specifications are the same as in Example 1.

[0074] This comparative example uses the exact same preparation process parameters as Example 1 to ensure the comparability of the experiments:

[0075] (1) Fiber pretreatment: 55g of hemp pulp fiber was placed in a standard de-fiber machine, 5.5L of deionized water was added, and the fiber was de-fibered at 3000rpm for 15 minutes at 25℃ to form a fiber suspension with a mass concentration of 1wt%.

[0076] (2) Preparation of polylactic acid emulsion: 32g of polylactic acid particles were dissolved in 210mL of dichloromethane, and 3.2g of Span-80 emulsifier was added. The mixture was emulsified at 10000rpm for 15 minutes to form an oil-in-water emulsion with a solid content of 20%.

[0077] (3) Mixed modification: Polylactic acid emulsion and 13g of epoxidized soybean oil were added to the fiber suspension and stirred at 500rpm for 40 minutes (since there is no nanocellulose, the stirring time is kept consistent).

[0078] (4) Forming: filter and dehydrate under a vacuum of -0.08MPa for 5 minutes to form a wet paper web with a basis weight of 80g / m².

[0079] (5) Hot pressing and curing: use the same temperature and pressure program: 90℃, 1.5MPa pre-press for 5 minutes, 130℃, 4MPa main pressure for 10 minutes.

[0080] (6) Curing treatment: Curing in a 65°C forced-air oven for 6 hours to obtain the final sample.

[0081] The comparative sample 3, lacking nanocellulose, showed a complete basal structure of hemp pulp fibers, but the interfiber bonding was loose. There was a significant gap between the polylactic acid-epoxy soybean oil composite phase and the fiber interface, and the interfacial bonding between the fiber and the polymer matrix was weak, with multiple instances of debonding observed. The cross-section of the material showed fiber pull-out, indicating insufficient interfacial bonding, lack of nanoscale reinforcing network, and poor structural integrity.

[0082] Similarly, the final product was tested. Due to the lack of nanocellulose, the interface bonding of Comparative Example 3 was poor, the tensile index dropped to 92 N·m / g, the elongation at break dropped to 11.2%, the insulation strength was 10.5 kV / mm, and the biodegradation rate after 90 days was only 45%.

[0083] Comparative Example 4

[0084] This comparative example uses the exact same raw material composition as Example 1 to verify the importance of the wet molding process. The specific composition ratio is 50 wt% hemp pulp fiber, 30 wt% polylactic acid, 15 wt% epoxidized soybean oil, and 5 wt% cellulose nanofibers. The raw material specifications are the same as in Example 1.

[0085] This comparative example uses a physical melt blending and hot pressing process, and the specific steps are as follows:

[0086] (1) Raw material pretreatment: The hemp pulp fiber was dried at 105℃ for 4 hours until the moisture content was <2%.

[0087] Polylactic acid particles were dried in a vacuum oven at 80°C for 4 hours, and cellulose nanofibers were dried at 60°C for 2 hours.

[0088] (2) Melt blending process: a twin-screw extruder (SHJ-20 type) is used for melt blending. Polylactic acid and epoxidized soybean oil are added first, and then dried hemp pulp fiber and nanocellulose are added after melting. The temperature is set to 165℃ for the feeding section, 175℃ for the plasticizing section, 180℃ for the mixing section, and 185℃ for the die head. The screw speed is 80 rpm and the mixing time is 5 minutes.

[0089] (3) Hot pressing molding: The blend is preheated at 180°C for 5 minutes in a flat vulcanizing machine, then hot pressed at 180°C and 10MPa for 8 minutes, and then pressure is maintained and cooled to 60°C before pressure is released.

[0090] (4) Post-treatment: The prepared sample is equilibrated for 24 hours under standard temperature and humidity conditions (23℃, 50%RH).

[0091] The samples prepared by physical blending and hot pressing process have obvious defects. The hemp pulp fiber undergoes thermal degradation during high-temperature melting, and the average fiber length decreases from 2.1 mm to 0.8 mm. The cellulose nanofiber exhibits agglomeration due to insufficient shear force during melt blending. The interface between plant fiber and polymer matrix is ​​clearly visible, with obvious phase separation and a lack of three-dimensional network structure, exhibiting typical characteristics of a filled composite system. The material is too dense and lacks the necessary pore structure.

[0092] Similarly, the final product was sampled and tested. Comparative Example 4 used a physical blending process, which could not form an ideal three-dimensional network structure. The tensile index was only 88 N·m / g, the elongation at break was 9.8%, the insulation strength was 9.8 kV / mm, and the 90-day biodegradation rate was 43%.

[0093] These experimental results fully verify the unique advantages of this invention through multi-component synergistic design and wet molding-hot pressing curing process. The addition of nanocellulose significantly enhances the material interface bonding, and the wet molding process is conducive to forming an ideal three-dimensional network structure, enabling the insulating paper material to simultaneously possess high strength, high ductility, excellent insulation performance and biodegradability, thus solving the technical problems existing in traditional insulating materials.

[0094] Table 1 shows a comparison of the performance test results between the examples and the comparative examples (see table below).

[0095]

[0096] This invention is not limited to the above embodiments. Any modifications, alterations, simplifications, combinations, or substitutions that do not depart from the essence and principle of this invention are within the protection scope of this patent.

Claims

1. A highly tough and highly ductile biodegradable insulating paper, characterized in that, It is composed of the following components: 35-65 wt% plant fiber, 15-45 wt% polylactic acid, 3-15 wt% bio-based toughening agent, and 0.5-5 wt% nanocellulose. The bio-based toughening agent is at least one of epoxidized soybean oil, acrylated castor oil, or polycaprolactone diol. The plant fiber, polylactic acid, bio-based toughening agent, and nanocellulose are compounded by wet molding and hot pressing to form a three-dimensional network structure. The insulating paper has an elongation at break of ≥15% and a tensile index of ≥100 N·m / g.

2. The biodegradable insulating paper according to claim 1, characterized in that, The plant fiber is at least one of hemp pulp fiber, wood pulp fiber, or regenerated cellulose fiber, and its average fiber length is 0.5 mm to 3.0 mm.

3. The biodegradable insulating paper according to claim 1, characterized in that, The nanocellulose is cellulose nanofiber or cellulose nanocrystal, with a diameter of 10 nm to 100 nm and an aspect ratio greater than 50.

4. The biodegradable insulating paper according to claim 1, characterized in that, The insulating paper has an insulation strength greater than or equal to 10kV / mm.

5. The biodegradable insulating paper according to claim 1, characterized in that, The insulating paper exhibits a biodegradation weight loss rate of ≥30% within 90 days under standard composting conditions.

6. A method for preparing a high-toughness, high-elongation biodegradable insulating paper as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Fiber pretreatment: Plant fibers are decomposed and dispersed in water in a decomposition machine to form a fiber suspension with a concentration of 0.5-2.0 wt%; S2. Mixed modification: Add polylactic acid emulsion, bio-based toughening agent and nanocellulose to the fiber suspension obtained in step S1, and stir at a speed of 300 rpm to 800 rpm for 20 minutes to 60 minutes to obtain a mixed slurry; S3. Forming: The mixed slurry is poured into a forming machine and dewatered under a vacuum of -0.06 MPa to -0.09 MPa to form a wet paper web; S4. Hot pressing and curing: The wet paper web is placed in a hot press and hot-pressed for 5 to 30 minutes at a temperature of 80°C to 150°C and a pressure of 1 MPa to 5 MPa to obtain the biodegradable insulating paper.

7. The method according to claim 6, characterized in that, In step S2, the polylactic acid emulsion is prepared by dissolving polylactic acid particles in dichloromethane or chloroform, adding an emulsifier, and emulsifying it in an aqueous phase by high-speed shearing to form an oil-in-water emulsion with a solid content of 10% to 30%.

8. The method according to claim 6, characterized in that, In step S4, the hot-press curing process is a programmed temperature and pressure increase, specifically including: first, pre-pressing at a temperature of 80°C to 100°C and a pressure of 1MPa to 2MPa for 2 to 10 minutes; then, main pressing at a temperature of 120°C to 150°C and a pressure of 3MPa to 5MPa for 3 to 20 minutes.

9. The method according to claim 6, characterized in that, Following step S4, the following is also included: S5. Curing treatment: Place the hot-pressed insulating paper in an oven at 50℃ to 80℃ and cure for 2 to 12 hours.

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