Optical fiber coating material with electromagnetic shielding performance and preparation method thereof

Abstract

The application discloses a kind of optical fiber coating materials with electromagnetic shielding performance and preparation method thereof, it is related to optical fiber coating protection and electromagnetic compatibility technical field.The application includes providing polyvinylidene fluoride, silver-coated copper flaky powder, multi-walled carbon nanotube, nanometer silicon dioxide, gamma-aminopropyl triethoxysilane, hindered phenol antioxidant, polyethylene wax and thermoplastic polyurethane, the nanometer silicon dioxide is silanized surface treatment and solidification dry, and modified nanometer silicon dioxide is obtained.The application is silanized and modified by nanometer silicon dioxide, and silver-coated copper flaky powder and multi-walled carbon nanotube are premixed and sheared to form conductive premix, melt blend extrusion in polyvinylidene fluoride / thermoplastic polyurethane continuous matrix phase and further coaxial extrusion coating on the outside of optical fiber, so as to obtain coating layer with electromagnetic shielding capacity under the premise of not changing the structure of optical fiber, realize the anti-interference and shielding protection effect of optical fiber in complex electromagnetic environment.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber cladding protection and electromagnetic compatibility technology, and in particular relates to an optical fiber cladding material with electromagnetic shielding properties and its preparation method. Background Technology

[0002] Optical fibers are widely used in communication transmission, distributed sensing, industrial control, and equipment interconnection. The outer cladding of optical fibers serves functions such as buffering, moisture protection, abrasion resistance, and bending resistance, while also being compatible with continuous extrusion and online winding production methods. In scenarios such as airborne systems, rail transit equipment cabins, data center computer rooms, base station cabinets, and the vicinity of high-power electrical devices, electromagnetic radiation sources are concentrated. Engineering designs often incorporate electromagnetic shielding into cable structure requirements, and optical fiber assemblies typically employ composite cladding structures to achieve integrated protection and shielding. Among existing solutions, metal braided layers combined with outer sheaths are commonly used, offering a straightforward structure and mature technology, with shielding layers and sheaths combined in layers. Metal foils and metallized films are also used to form continuous shielding. The coating layer is often used in combination with the polymer layer; the conductive polymer coating route is also common, where carbon-based materials, metal powders or other conductive phases are introduced into the polymer matrix to form a conductive path before the coating layer is made; some schemes form a conductive coating on the surface of the coating layer, and the material system covers solvent-based coatings, hot-melt coatings and reaction-curing coatings; other schemes use deposition, plating and other methods to form a metal layer on the surface, pursuing thinner layers and miniaturization; the preparation process is mostly organized around online extrusion, coating and curing, lamination and compounding, surface treatment and other links, paying attention to formulation rheology, interlayer adhesion, outer diameter control, environmental resistance and batch consistency, and some structures also set transition layers or interface control layers to stabilize the bonding state.

[0003] The core defect of existing technology is the insufficient electromagnetic shielding stability under thin-layer coating conditions. The conductivity continuity of the shielding layer changes under bending, temperature and humidity cycling and surface wear, and the shielding performance decays with service time. It is difficult to meet the system's requirements for both thinness and durability in terms of product consistency and long-term reliability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an optical fiber cladding material with electromagnetic shielding properties and its preparation method. The technical problem this invention aims to solve is: how to address the issues of unstable conductivity and attenuation of shielding performance in thin-layer shielding layers under bending and environmental cycling through a thin-layer cladding process constructed with interface modification and conductive networks.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an optical fiber cladding material with electromagnetic shielding properties, comprising, by weight percentage:

[0006] Polyvinylidene fluoride 40%-52%;

[0007] Silver-coated copper flake powder: 16%-22%;

[0008] Multi-walled carbon nanotubes: 0.25%-0.70%;

[0009] Nano-silica 1.0%-3.0%;

[0010] γ-aminopropyltriethoxysilane 0.20%-0.60%;

[0011] The hindered phenolic antioxidant is 0.10%-0.30%; the hindered phenolic antioxidant is pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid];

[0012] Polyethylene wax 0.20%-0.60%;

[0013] The balance is thermoplastic polyurethane, and the sum of the mass percentages of the polyvinylidene fluoride and the thermoplastic polyurethane is 73%-82%.

[0014] The present invention is further configured such that the median particle size D50 of the silver-coated copper flake powder is 5μm-18μm, and the thickness of the silver-coated copper flake powder is 0.1μm-1.5μm.

[0015] The present invention is further configured such that the outer diameter of the multi-walled carbon nanotube is 10nm-30nm and the length is 5μm-15μm.

[0016] A method for preparing an optical fiber cladding material with electromagnetic shielding properties, comprising:

[0017] S1. Provide polyvinylidene fluoride, silver-coated copper flake powder, multi-walled carbon nanotubes, nano-silica, γ-aminopropyltriethoxysilane, hindered phenolic antioxidant, polyethylene wax and thermoplastic polyurethane, perform silanization surface treatment on the nano-silica and cure and dry it to obtain modified nano-silica.

[0018] S2. The silver-coated copper flake powder and the multi-walled carbon nanotubes are premixed and sheared to obtain a conductive premix; the multi-walled carbon nanotubes are attached to and bridged between the silver-coated copper flake powders through the premixing and shearing dispersion.

[0019] S3. The polyvinylidene fluoride and the thermoplastic polyurethane are melt-plasticized to form a continuous matrix phase; the conductive premix is ​​added to the continuous matrix phase and dispersed, and then the modified nano silica, the hindered phenolic antioxidant and the polyethylene wax are added, melt-blended and extruded to obtain the optical fiber cladding material melt.

[0020] S4. Cool the fiber cladding material melt and cut it into particles to obtain fiber cladding material particles;

[0021] S5. The optical fiber cladding material particles are melted, extruded, and coated onto the outside of the optical fiber body to form a cladding layer; the thickness of the cladding layer is 20μm-80μm.

[0022] The present invention is further configured such that the silanization surface treatment includes dispersing the nano-silica in an ethanol-water mixed medium, adjusting the pH of the dispersion system to 4.0-5.5 with acetic acid; adding the γ-aminopropyltriethoxysilane to the dispersion system after pre-hydrolyzing for 10-30 minutes, and stirring the reaction for 0.5-2 hours; after the reaction is completed, performing solid-liquid separation on the dispersion system to obtain modified nano-silica solid; washing the modified nano-silica solid with ethanol 1-3 times to obtain the modified nano-silica to be dried.

[0023] The present invention is further configured such that the curing and drying is carried out at 80℃-120℃ for 2h-6h, and the moisture content of the modified nano silica after curing and drying is not greater than 0.5wt% by mass percentage.

[0024] The present invention is further configured such that the premixing and shear dispersion are carried out in a closed shear mixing device; the mass ratio of the silver-coated copper flake powder to the multi-walled carbon nanotubes is 30:1-70:1; the rotation speed of the shear dispersion is 2000rpm-8000rpm, and the time is 5min-20min.

[0025] The present invention is further configured such that the melt plasticizing and melt blending are completed using a co-rotating twin-screw extruder; the polyvinylidene fluoride and the thermoplastic polyurethane are added through the main feed port and form the continuous matrix phase in the melting section; the conductive premix is ​​added downstream of the continuous matrix phase through the side feed port, and the conductive premix is ​​added after the continuous matrix phase is formed; the barrel temperature of the twin-screw extruder is 160℃-230℃, and the screw speed is 100rpm-400rpm.

[0026] The present invention is further configured such that the cooling and pelletizing includes cooling and shaping the extruded strip in a water-cooling tank and then pelletizing it; the water temperature of the water-cooling tank is 15℃-30℃; and the length of the optical fiber cladding material particles is 2mm-5mm.

[0027] The present invention is further configured such that the coating is achieved by coaxial extrusion coating using a crosshead die; after coating, the coating layer is cooled online and wound up to form a coating layer with a thickness of 20μm-80μm.

[0028] The beneficial effects of this invention are as follows: This invention modifies nano-silica by silanization, and premixes and shears silver-coated copper flake powder with multi-walled carbon nanotubes to form a conductive premix. This premix is ​​then melt-blended and extruded in a continuous matrix phase of polyvinylidene fluoride / thermoplastic polyurethane and further coaxially extruded to coat the outer side of an optical fiber. This results in a coating layer with electromagnetic shielding capabilities without altering the optical fiber structure, thus achieving anti-interference and shielding protection effects for the optical fiber in complex electromagnetic environments.

[0029] This invention employs a composite conductive construction method that uses silver-coated copper sheet powder and multi-walled carbon nanotubes for bridging. This allows the carbon nanotubes to adhere to and bridging the sheet powder to form a more continuous and stable conductive network. In addition, silanized modified nano-silica is used to improve the dispersion and interfacial compatibility of the inorganic phase in the matrix. At the same time, antioxidants and polyethylene wax are introduced into the polyvinylidene fluoride and thermoplastic polyurethane composite matrix to improve processing stability and long-term service reliability. This allows the coating layer to maintain flexibility and extrusion molding while achieving more stable electromagnetic shielding performance and better aging resistance, wear resistance and structural uniformity. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0031] Figure 1 This is a schematic diagram illustrating the relationship between the material composition and function of the present invention.

[0032] Figure 2 This is a flowchart of the nano-silica surface treatment process of the present invention.

[0033] Figure 3 This is a flowchart illustrating the preparation process of the conductive premix of the present invention.

[0034] Figure 4 This is a flow chart of the melt blending and extrusion process of the present invention.

[0035] Figure 5 This is a flowchart of the optical fiber cladding layer forming process of the present invention. Detailed Implementation

[0036] The technical solutions of the present invention will be described below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0037] Example 1

[0038] Please see Figures 1-5 This invention relates to an optical fiber cladding material with electromagnetic shielding properties, comprising, by weight percentage:

[0039] Polyvinylidene fluoride 40%.

[0040] The silver-coated copper flake powder comprises 21%. The median particle size (D50) of the silver-coated copper flake powder is 5 μm, and the thickness of the silver-coated copper flake powder is 0.1 μm.

[0041] Multi-walled carbon nanotubes account for 0.7%. The outer diameter of the multi-walled carbon nanotubes is 10 nm, and the length is 5 μm.

[0042] Nano-silica 3.0%.

[0043] γ-aminopropyltriethoxysilane 0.60%.

[0044] The hindered phenolic antioxidant is 0.30%. The hindered phenolic antioxidant is pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

[0045] Polyethylene wax 0.60%.

[0046] The balance is thermoplastic polyurethane, and the sum of the mass percentages of polyvinylidene fluoride and thermoplastic polyurethane is 73.8%.

[0047] A method for preparing an optical fiber cladding material with electromagnetic shielding properties, comprising:

[0048] S1. A modified nano-silica is obtained by providing polyvinylidene fluoride (PVDF), silver-coated copper flake powder, multi-walled carbon nanotubes, nano-silica, γ-aminopropyltriethoxysilane, hindered phenolic antioxidant, polyethylene wax, and thermoplastic polyurethane, followed by silanization surface treatment and curing / drying. The silanization surface treatment involves dispersing the nano-silica in an ethanol-water mixture and adjusting the pH of the dispersion to 4.0 using acetic acid. γ-aminopropyltriethoxysilane is pre-hydrolyzed for 10 min and then added to the dispersion, followed by stirring for 0.5 h. After the reaction, the dispersion is separated into solid and liquid components to obtain the modified nano-silica solid. The modified nano-silica solid is washed once with ethanol to obtain the modified nano-silica to be dried. Curing and drying are carried out at 80℃ for 2 h. After curing and drying, the modified nano-silica has a moisture content of no more than 0.5 wt%.

[0049] S2. Silver-coated copper flake powder and multi-walled carbon nanotubes (MWCNTs) are premixed and shear-dispersed to obtain a conductive premix. Premixing and shear dispersion allow the MCCNTs to attach to and bridge the spaces between the silver-coated copper flake powder particles. The premixing and shear dispersion are performed in a closed shear mixing apparatus. The mass ratio of silver-coated copper flake powder to MCCNTs is 30:1. The shear dispersion speed is 2000 rpm, and the time is 5 min.

[0050] S3. Polyvinylidene fluoride (PVDF) and thermoplastic polyurethane (TPU) are melt-plasticized to form a continuous matrix phase. A conductive premix is ​​added to the continuous matrix phase and dispersed, followed by the addition of modified nano-silica, hindered phenolic antioxidant, and polyethylene wax for melt blending and extrusion to obtain the optical fiber coating material melt. Melt plasticizing and melt blending are performed using a co-rotating twin-screw extruder. PVDF and TPU are added through the main feed port and form a continuous matrix phase in the melting section. The conductive premix is ​​added downstream of the continuous matrix phase through the side feed port, after the formation of the continuous matrix phase. The barrel temperature of the twin-screw extruder is 160°C, and the screw speed is 100 rpm.

[0051] S4. Cool and granulate the fiber cladding material melt to obtain fiber cladding material particles. Cooling and granulation includes granulating the extruded strip after cooling and shaping it in a water-cooling bath. The water temperature in the water-cooling bath is 15℃. The particle length of the fiber cladding material is 2mm.

[0052] S5. The optical fiber cladding material particles are melted, extruded, and coated onto the outside of the optical fiber body to form a cladding layer. The cladding layer thickness is 20 μm. The cladding is achieved using a cross-head coaxial extrusion method. After cladding, the cladding layer is cooled online and wound up to form a cladding layer with a thickness of 20 μm.

[0053] By increasing the content of silver-coated copper flake powder and multi-walled carbon nanotubes and adopting a flake-to-tube ratio of 30:1, it is easier to form a flake-to-tube bridging conductive path in the continuous matrix of silver-coated copper flake powder and multi-walled carbon nanotubes. At the same time, the combination of a higher proportion of silanized modified nano-silica and additive system is beneficial to improving filler dispersion and interface stability. This shows that the present invention can still obtain an extrudable and layerable electromagnetic shielding optical fiber cladding material under the conditions of lower barrel temperature and lower screw speed, and can achieve the formation of a thinner cladding layer.

[0054] Example 2

[0055] Please see Figures 1-5 Based on Example 1, an optical fiber cladding material with electromagnetic shielding properties comprises, by weight percentage:

[0056] Polyvinylidene fluoride 46%.

[0057] The silver-coated copper flake powder accounts for 19.12%. The median particle size (D50) of the silver-coated copper flake powder is 11.5 μm, and the thickness of the silver-coated copper flake powder is 0.8 μm.

[0058] Multi-walled carbon nanotubes account for 0.38%. The outer diameter of the multi-walled carbon nanotubes is 20 nm, and the length is 10 μm.

[0059] Nano-silica 2.0%.

[0060] γ-aminopropyltriethoxysilane 0.40%.

[0061] 0.20% hindered phenolic antioxidant. The hindered phenolic antioxidant is pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

[0062] Polyethylene wax 0.40%.

[0063] The balance is thermoplastic polyurethane, and the sum of the mass percentages of polyvinylidene fluoride and thermoplastic polyurethane is 77.5%.

[0064] A method for preparing an optical fiber cladding material with electromagnetic shielding properties, comprising:

[0065] S1. A modified nano-silica is obtained by providing polyvinylidene fluoride (PVDF), silver-coated copper flake powder, multi-walled carbon nanotubes, nano-silica, γ-aminopropyltriethoxysilane, hindered phenolic antioxidant, polyethylene wax, and thermoplastic polyurethane, followed by silanization surface treatment and curing / drying. The silanization surface treatment involves dispersing the nano-silica in an ethanol-water mixture and adjusting the pH of the dispersion to 4.3 using acetic acid. γ-aminopropyltriethoxysilane is pre-hydrolyzed for 20 min and then added to the dispersion, followed by stirring and reaction for 1.25 h. After the reaction, the dispersion is separated into solid and liquid components to obtain the modified nano-silica solid. The modified nano-silica solid is washed twice with ethanol to obtain the modified nano-silica to be dried. Curing and drying are carried out at 100℃ for 4 h. After curing and drying, the modified nano-silica has a moisture content of no more than 0.5 wt%.

[0066] S2. Silver-coated copper flake powder and multi-walled carbon nanotubes were premixed and shear-dispersed to obtain a conductive premix. Premixing and shear dispersion allowed the multi-walled carbon nanotubes to attach to and bridge the spaces between the silver-coated copper flake powder particles. The premixing and shear dispersion were carried out in a closed shear mixing apparatus. The mass ratio of silver-coated copper flake powder to multi-walled carbon nanotubes was 50:1. The shear dispersion speed was 5000 rpm, and the time was 12.5 min.

[0067] S3. Polyvinylidene fluoride (PVDF) and thermoplastic polyurethane (TPU) are melt-plasticized to form a continuous matrix phase. A conductive premix is ​​added to the continuous matrix phase and dispersed, followed by the addition of modified nano-silica, hindered phenolic antioxidant, and polyethylene wax for melt blending and extrusion to obtain the optical fiber coating material melt. Melt plasticizing and melt blending are performed using a co-rotating twin-screw extruder. PVDF and TPU are added through the main feed port and form a continuous matrix phase in the melting section. The conductive premix is ​​added downstream of the continuous matrix phase through the side feed port, after the formation of the continuous matrix phase. The barrel temperature of the twin-screw extruder is 195°C, and the screw speed is 250 rpm.

[0068] S4. Cool and slit the fiber optic cladding material melt to obtain fiber optic cladding material particles. Cooling and slitting includes slitting the extruded strip after cooling and shaping it in a water-cooling bath. The water temperature in the water-cooling bath is 22.5℃. The particle length of the fiber optic cladding material is 3.5mm.

[0069] S5. The optical fiber cladding material particles are melted, extruded, and coated onto the outside of the optical fiber body to form a cladding layer. The cladding layer thickness is 50 μm. The cladding is achieved using a cross-head coaxial extrusion method. After cladding, the cladding layer is cooled online and wound up to form a cladding layer with a thickness of 50 μm.

[0070] This embodiment achieves a relatively balanced combination in terms of conductive filler content, the ratio of silver-coated copper flake powder to multi-walled carbon nanotube matrix, and the amount of nano-silica and additives. It also employs a 50:1 flake-to-tube ratio and moderate-intensity premixed shear dispersion, allowing the conductive premix to be added after the formation of the continuous matrix phase and then melt-blended and extruded. This demonstrates a balance between conductive network construction and matrix toughness / extrusion stability. Therefore, it can be concluded that this invention can stably produce granulatable and coaxially extruded coating materials under moderate process conditions, which are suitable for forming medium-thickness optical fiber cladding layers.

[0071] Example 3

[0072] Please see Figures 1-5 Based on Examples 1 and 2, an optical fiber cladding material with electromagnetic shielding properties comprises, by weight percentage:

[0073] Polyvinylidene fluoride 52%.

[0074] The silver-coated copper flake powder accounts for 17.5%. The median particle size (D50) of the silver-coated copper flake powder is 18 μm, and the thickness of the silver-coated copper flake powder is 1.5 μm.

[0075] Multi-walled carbon nanotubes account for 0.25%. The outer diameter of the multi-walled carbon nanotubes is 30 nm, and the length is 15 μm.

[0076] Nano-silica 1.0%.

[0077] 0.20% γ-aminopropyltriethoxysilane.

[0078] 0.10% hindered phenolic antioxidant. The hindered phenolic antioxidant is pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

[0079] Polyethylene wax 0.20%.

[0080] The balance is thermoplastic polyurethane, and the sum of the mass percentages of polyvinylidene fluoride and thermoplastic polyurethane is 80.75%.

[0081] A method for preparing an optical fiber cladding material with electromagnetic shielding properties, comprising:

[0082] S1. A modified nano-silica is obtained by providing polyvinylidene fluoride (PVDF), silver-coated copper flake powder, multi-walled carbon nanotubes, nano-silica, γ-aminopropyltriethoxysilane, hindered phenolic antioxidant, polyethylene wax, and thermoplastic polyurethane, followed by silanization surface treatment and curing / drying. The silanization surface treatment involves dispersing the nano-silica in an ethanol-water mixture and adjusting the pH of the dispersion to 5.5 using acetic acid. γ-aminopropyltriethoxysilane is pre-hydrolyzed for 30 min and then added to the dispersion, followed by stirring and reaction for 2 h. After the reaction, the dispersion is separated into solid and liquid components to obtain the modified nano-silica solid. The modified nano-silica solid is washed three times with ethanol to obtain the modified nano-silica to be dried. Curing and drying are carried out at 120℃ for 6 h. After curing and drying, the modified nano-silica has a moisture content of no more than 0.5 wt%.

[0083] S2. Silver-coated copper flake powder and multi-walled carbon nanotubes were premixed and shear-dispersed to obtain a conductive premix. The multi-walled carbon nanotubes were attached to and bridged between the silver-coated copper flake powder particles through premixing and shear dispersion. Premixing and shear dispersion were carried out in a closed shear mixing apparatus. The mass ratio of silver-coated copper flake powder to multi-walled carbon nanotubes was 70:1. The shear dispersion speed was 8000 rpm, and the time was 20 min.

[0084] S3. Polyvinylidene fluoride (PVDF) and thermoplastic polyurethane (TPU) are melt-plasticized to form a continuous matrix phase. A conductive premix is ​​added to the continuous matrix phase and dispersed, followed by the addition of modified nano-silica, hindered phenolic antioxidant, and polyethylene wax for melt blending and extrusion to obtain the optical fiber coating material melt. Melt plasticizing and melt blending are performed using a co-rotating twin-screw extruder. PVDF and TPU are added through the main feed port and form a continuous matrix phase in the melting section. The conductive premix is ​​added downstream of the continuous matrix phase through the side feed port, after the formation of the continuous matrix phase. The barrel temperature of the twin-screw extruder is 230°C, and the screw speed is 400 rpm.

[0085] S4. Cool and granulate the fiber cladding material melt to obtain fiber cladding material particles. Cooling and granulation includes granulating the extruded strip after cooling and shaping it in a water-cooling bath. The water temperature in the water-cooling bath is 30℃. The particle length of the fiber cladding material is 5mm.

[0086] S5. The optical fiber cladding material particles are melted, extruded, and coated onto the outside of the optical fiber body to form a cladding layer. The cladding layer thickness is 80 μm. The cladding is achieved using a cross-head coaxial extrusion method. After cladding, the cladding layer is cooled online and wound up to form a cladding layer with a thickness of 80 μm.

[0087] This embodiment increases the proportion of silver-coated copper flake powder while reducing the amounts of conductive filler, nano-silica, and additives. Simultaneously, it employs a 70:1 flake-to-tube ratio. Through higher shear dispersion and a wider extrusion temperature / speed window, it still achieves dispersion and melt extrusion coating of the conductive premix of carbon nanotubes bridging silver-coated copper flake powder in the matrix phase, and forms a thicker coating layer. Therefore, it can be concluded that the premix bridging + side-feed post-addition + melt blending extrusion + coaxial coating route of this invention has process adaptability to different formulation values ​​and can support stable layering and large-scale processing under conditions of higher matrix proportions.

[0088] Example 4

[0089] While maintaining a consistent process route, the feasibility of preparing electromagnetic shielding optical fiber cladding materials and their process adaptability to changes in the ratio were compared and verified by setting three sets of formula values ​​(A, B, and C) and corresponding process windows.

[0090] 1. Three formulations and conductive phase morphology settings

[0091] Experiment A: Polyvinylidene fluoride 40%, silver-coated copper flake powder 21%, D50=5μm, thickness 0.1μm, multi-walled carbon nanotubes 0.7%, outer diameter 10nm, length 5μm, nano-silica 3.0%, γ-aminopropyltriethoxysilane 0.60%, hindered phenolic antioxidant 0.30%, polyethylene wax 0.60%, thermoplastic polyurethane as the balance, and polyvinylidene fluoride + thermoplastic polyurethane = 73.8%.

[0092] Experiment B: Polyvinylidene fluoride 46%, silver-coated copper flake powder 19.12%, D50=11.5μm, thickness 0.8μm, multi-walled carbon nanotubes 0.38%, outer diameter 20nm, length 10μm, nano-silica 2.0%, γ-aminopropyltriethoxysilane 0.40%, hindered phenolic antioxidant 0.20%, polyethylene wax 0.40%, thermoplastic polyurethane as the balance, and polyvinylidene fluoride + thermoplastic polyurethane = 77.5%.

[0093] Experiment C: Polyvinylidene fluoride 52%, silver-coated copper flake powder 17.5%, D50=18μm, thickness 1.5μm, multi-walled carbon nanotubes 0.25%, outer diameter 30nm, length 15μm, nano-silica 1.0%, γ-aminopropyltriethoxysilane 0.20%, hindered phenolic antioxidant 0.10%, polyethylene wax 0.20%, thermoplastic polyurethane as the balance, and polyvinylidene fluoride + thermoplastic polyurethane = 80.75%.

[0094] 2. Preparation of modified nano-silica

[0095] Experiment A: Rapid, strong modification side.

[0096] Nano-silica was dispersed in an ethanol-water system, and the pH was adjusted to 4.0 with acetic acid. γ-aminopropyltriethoxysilane was pre-hydrolyzed for 10 min before being added, and the mixture was stirred for 0.5 h. After the reaction, the solid and liquid phases were separated, the mixture was washed once with ethanol, and then cured and dried at 80 °C for 2 h. The water content after drying was ≤0.5 wt%.

[0097] Experiment B: The pH of the dispersion system was controlled at 4.3, the pre-hydrolysis of γ-aminopropyltriethoxysilane was extended to 20 min, the reaction was stirred for 1.25 h, the solid-liquid separation was followed by washing twice with ethanol, and the solidification and drying were carried out at 100℃ for 4 h. The water content was also controlled to be ≤0.5 wt%.

[0098] Experiment C: Full reaction and high-temperature curing side.

[0099] The pH was adjusted to 5.5 to change the hydrolysis / condensation rhythm. γ-aminopropyltriethoxysilane was pre-hydrolyzed for 30 min and then added and reacted for 2 h. After separation, the mixture was washed 3 times with ethanol and cured and dried at 120℃ for 6 h. The final water content was ≤0.5wt%.

[0100] All three groups used silanization + curing and drying with a moisture content of ≤0.5wt% as a consistent boundary to ensure that subsequent melt blending is not affected by moisture. Group A focuses on stronger surface treatment intensity, more acid, higher silane dosage, and shorter process. Group B is a compromise, while Group C completes the surface reaction fully through longer pre-hydrolysis / reaction and higher curing temperature.

[0101] 3. Construction of conductive premix

[0102] Experiment A: High carbon nanotube content, mild shear.

[0103] In a closed shear mixing device, silver-coated copper flake powder and multi-walled carbon nanotubes are premixed at a ratio of 30:1 and sheared and dispersed at a speed of 2000 rpm for 5 minutes, so that the multi-walled carbon nanotubes are attached and bridged between the flake powders.

[0104] Experiment B: Medium ratio, medium shear.

[0105] The mass ratio of silver-coated copper flake powder to multi-walled carbon nanotubes was 50:1, and the shear dispersion was increased to 5000 rpm and extended to 12.5 min to enhance bridging and uniform adhesion.

[0106] Experiment C: Carbon nanotubes had the lowest values, compensated by high shear.

[0107] The ratio was increased to 70:1, and the shearing conditions were increased to 8000 rpm for 20 min to ensure that an effective cross-connection network could still be formed with a lower amount of carbon nanotubes.

[0108] The designs from A to C demonstrate how increasing shear strength and time compensate for the difficulty of bridging as the multi-walled carbon nanotubes gradually decrease in size, thus forming a comparable three-level conductive network construction strategy.

[0109] 4. Twin-screw melt blending extrusion

[0110] All three groups use co-rotating twin-screw extruders: polyvinylidene fluoride and thermoplastic polyurethane are plasticized through the main feed port and form a continuous matrix phase in the melting section.

[0111] The conductive premix is ​​added from the side feed port to the downstream position after the continuous matrix phase is formed, and then modified silica, antioxidant and PE wax are added to complete the co-extrusion.

[0112] The three running windows are as follows:

[0113] Experiment A: barrel temperature 160℃, screw speed 100rpm; Experiment B: barrel temperature 195℃, screw speed 250rpm; Experiment C: barrel temperature 230℃, screw speed 400rpm.

[0114] The three groups jointly verified the constraining effect of the feeding sequence of the conductive premix after the formation of the continuous matrix phase on the dispersion and extrusion stability. Under this common strategy, A can operate at low temperature and low speed to adapt to higher filler systems, B is in a medium window, and C matches stronger dispersion requirements with high temperature and high speed while ensuring that the melt can be extruded.

[0115] 5. Cool and pelletize

[0116] Experiment A: The extruder was shaped in a 15℃ water-cooling bath and then cut into pellets with a length of 2mm. Experiment B: The water temperature was adjusted to 22.5℃ and the pellet length was set to 3.5mm. Experiment C: The water temperature was 30℃ and the pellet length was 5mm.

[0117] The particle length increases from 2mm to 5mm, corresponding to the subsequent coating layer thickness gradient: thin coating relies more on rapid plasticization and uniform discharge, while thick coating emphasizes feeding continuity and stable supply.

[0118] 6. Crosshead coaxial extrusion coating

[0119] Experiment A: After melt extrusion, the particles were coaxially coated onto the outside of the optical fiber, with a coating thickness of 20 μm, and then cooled and wound up online.

[0120] Experiment B: The coating thickness was increased to 50μm, and the same method of coaxial coating with a crosshead and online cooling and winding was used.

[0121] Experiment C: The coating thickness was further increased to 80 μm, and online cooling and winding were completed.

[0122] All three groups were able to achieve coaxial coating at thicknesses of 20 / 50 / 80μm, indicating that the process route is scalable for thin-medium-thick coating requirements. Among them, A tends to achieve thinner thickness with a stronger conductive phase / thinner layer, C obtains lamination margin with a higher substrate ratio and thicker layer, and B represents a compromise window.

[0123] While maintaining the common route of modified silica water control ≤0.5wt% - sheet / tube conductive premix bridging - continuous matrix phase formation followed by side feeding of conductive premix - twin-screw melt blending extrusion - coaxial coating layering, by increasing the ratio of silver-coated copper to multi-walled carbon nanotubes from 30:1 to 70:1, and simultaneously adjusting the shear dispersion strength, extrusion window and layering thickness, all three groups of samples achieved extrudable granules and stable coating layering, indicating that the technical solution of this invention is feasible and process-adaptable when the requirements for conductive network strength and coating thickness change.

[0124] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. An optical fiber cladding material with electromagnetic shielding properties, characterized in that, By weight percentage, including: Polyvinylidene fluoride 40%-52%; Silver-coated copper flake powder: 16%-22%; Multi-walled carbon nanotubes: 0.25%-0.70%; Nano-silica 1.0%-3.0%; γ-aminopropyltriethoxysilane 0.20%-0.60%; The hindered phenolic antioxidant is 0.10%-0.30%; the hindered phenolic antioxidant is pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]; Polyethylene wax 0.20%-0.60%; The balance is thermoplastic polyurethane, and the sum of the mass percentages of the polyvinylidene fluoride and the thermoplastic polyurethane is 73%-82%.

2. The optical fiber cladding material with electromagnetic shielding properties according to claim 1, characterized in that: The median particle size D50 of the silver-coated copper flake powder is 5μm-18μm, and the thickness of the silver-coated copper flake powder is 0.1μm-1.5μm.

3. The optical fiber cladding material with electromagnetic shielding properties according to claim 1, characterized in that: The multi-walled carbon nanotubes have an outer diameter of 10nm-30nm and a length of 5μm-15μm.

4. A method for preparing an optical fiber cladding material with electromagnetic shielding properties, used to prepare an optical fiber cladding material with electromagnetic shielding properties as described in any one of claims 1-3, characterized in that, include: S1. Provide polyvinylidene fluoride, silver-coated copper flake powder, multi-walled carbon nanotubes, nano-silica, γ-aminopropyltriethoxysilane, hindered phenolic antioxidant, polyethylene wax and thermoplastic polyurethane, perform silanization surface treatment on the nano-silica and cure and dry it to obtain modified nano-silica. S2. The silver-coated copper flake powder and the multi-walled carbon nanotubes are premixed and sheared to obtain a conductive premix; the multi-walled carbon nanotubes are attached to and bridged between the silver-coated copper flake powders through the premixing and shearing dispersion. S3. The polyvinylidene fluoride and the thermoplastic polyurethane are melt-plasticized to form a continuous matrix phase; the conductive premix is ​​added to the continuous matrix phase and dispersed, and then the modified nano silica, the hindered phenolic antioxidant and the polyethylene wax are added, melt-blended and extruded to obtain the optical fiber cladding material melt. S4. Cool the fiber cladding material melt and cut it into particles to obtain fiber cladding material particles; S5. The optical fiber cladding material particles are melted, extruded, and coated onto the outside of the optical fiber body to form a cladding layer; the thickness of the cladding layer is 20μm-80μm.

5. The method for preparing an optical fiber cladding material with electromagnetic shielding properties according to claim 4, characterized in that: The silanization surface treatment includes dispersing the nano-silica in an ethanol-water mixed medium, adjusting the pH of the dispersion system to 4.0-5.5 with acetic acid; adding the γ-aminopropyltriethoxysilane to the dispersion system after pre-hydrolyzing for 10-30 minutes, and stirring the reaction for 0.5-2 hours; after the reaction, performing solid-liquid separation on the dispersion system to obtain modified nano-silica solid; washing the modified nano-silica solid with ethanol 1-3 times to obtain the modified nano-silica to be dried.

6. The method for preparing an optical fiber cladding material with electromagnetic shielding properties according to claim 4, characterized in that: The curing and drying process is carried out at 80℃-120℃ for 2h-6h, and the moisture content of the modified nano silica after curing and drying is no more than 0.5wt% by mass percentage.

7. The method for preparing an optical fiber cladding material with electromagnetic shielding properties according to claim 4, characterized in that: The premixing and shear dispersion are carried out in a closed shear mixing device; the mass ratio of the silver-coated copper flake powder to the multi-walled carbon nanotubes is 30:1-70:1; the shear dispersion speed is 2000rpm-8000rpm and the time is 5min-20min.

8. The method for preparing an optical fiber cladding material with electromagnetic shielding properties according to claim 4, characterized in that: The melt plasticizing and melt blending are completed using a co-rotating twin-screw extruder; the polyvinylidene fluoride and the thermoplastic polyurethane are added through the main feed port and form the continuous matrix phase in the melting section; the conductive premix is ​​added downstream of the continuous matrix phase through the side feed port, and the conductive premix is ​​added after the continuous matrix phase is formed; the barrel temperature of the twin-screw extruder is 160℃-230℃, and the screw speed is 100rpm-400rpm.

9. A method for preparing an optical fiber cladding material with electromagnetic shielding properties according to claim 4, characterized in that: The cooling and pelletizing process includes cooling and shaping the extruded strip in a water-cooling tank and then pelletizing it; the water temperature in the water-cooling tank is 15℃-30℃; and the length of the optical fiber cladding material particles is 2mm-5mm.

10. A method for preparing an optical fiber cladding material with electromagnetic shielding properties according to claim 4, characterized in that: The coating is achieved by coaxial extrusion coating using a crosshead die; after coating, the coating layer is cooled online and wound up to form a coating layer with a thickness of 20μm-80μm.

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