Flame-retardant butterfly-shaped optical cable for high-temperature environments

Abstract

This invention relates to the field of optical communication transmission technology and discloses a flame-retardant butterfly-shaped drop cable for high-temperature environments, comprising: an optical fiber unit consisting of at least one quartz glass optical fiber, the surface of which is coated with a high-temperature resistant acrylic resin coating with a thickness of 30 μm to 50 μm; and a flame-retardant sheath covering the outside of the optical fiber unit. The flame-retardant sheath uses thermoplastic polyurethane elastomer as the matrix material and uniformly disperses a composite flame-retardant filler therein. The composite flame-retardant filler is composed of an inorganic phosphorus-based flame retardant, a nitrogen-based flame retardant, and nano-layered silicate in a mass ratio of 2:1:1. This invention, by uniformly dispersing the composite flame-retardant filler composed of inorganic phosphorus-based flame retardant, nitrogen-based flame retardant, and nano-layered silicate in a thermoplastic polyurethane elastomer matrix, enables the flame-retardant sheath material to have superior flame-retardant efficiency and drip suppression effect compared to a single flame retardant, achieving a V-0 rating for vertical burning and preventing molten droplets from igniting cotton.

Description

Technical Field

[0001] This invention relates to the field of optical communication transmission technology, specifically to a flame-retardant butterfly-shaped optical cable for use in high-temperature environments. Background Technology

[0002] With the widespread application of fiber optic communication networks in industries, energy, and rail transportation, higher requirements are placed on the reliability of optical cables in extreme environments. Especially in high-temperature, open-flame, or strong heat radiation scenarios, optical cables not only need to maintain stable signal transmission performance, but also must have excellent flame retardancy, heat resistance, and structural stability. As the physical carrier of information transmission, the material selection, structural design, and manufacturing process of optical cables directly determine their service life and safety level under harsh working conditions. Among them, fiber optic cables are widely deployed near heat sources or potential fire hazards due to their ease of indoor wiring and terminal access. Therefore, the requirements for flame retardancy and high-temperature adaptability are particularly prominent.

[0003] Among them, butterfly-shaped drop cables have become one of the mainstream forms of fiber-to-the-home and industrial access due to their advantages such as flat structure, good bending resistance and easy fixation. These cables usually use polyolefin or polyvinyl chloride as the outer sheath material and provide mechanical support through built-in reinforcement. However, in high-temperature environments, traditional sheath materials are prone to softening, melting or even burning, which not only leads to the collapse of the cable structure and a sharp increase in fiber micro-bending loss, but may also release toxic fumes and increase the risk of fire. In addition, the reinforcement of existing butterfly-shaped cables is mostly made of metal or glass fiber. The former is prone to heat conduction at high temperatures, causing a sudden rise in internal temperature, while the latter has the problem of high brittleness and easy breakage, making it difficult to balance mechanical strength and thermal stability.

[0004] While existing flame-retardant optical cables improve fire resistance by adding halogen-based or halogen-free flame retardants, they often sacrifice material flexibility and processability, and their flame-retardant performance rapidly diminishes under sustained high temperatures. Some solutions employ ceramicized silicone rubber or mica tape wrapping structures, which can form a heat-insulating carbon layer, but the process is complex and costly, and it is difficult to adapt to the thin and lightweight design requirements of butterfly optical cables. More importantly, existing products lack synergistic optimization of multiple performance aspects such as flame retardancy, heat resistance, low smoke, and structural integrity. Under real fire or high-temperature conditions, chain failures such as sheath cracking, fiber displacement, and transmission interruption often occur. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a flame-retardant butterfly-shaped optical cable for high-temperature environments, solving the problem of "lack of synergistic optimization of multiple properties such as flame retardancy, heat resistance, low smoke, and structural integrity" in the aforementioned background technologies.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: a flame-retardant butterfly-shaped optical cable for high-temperature environments, characterized in that it comprises the following components:

[0009] An optical fiber unit, wherein the optical fiber unit is composed of at least one quartz glass optical fiber, and the surface of the optical fiber is coated with a high-temperature resistant acrylic resin coating with a coating thickness of 30μm to 50μm;

[0010] A flame-retardant sheath is provided, which covers the outside of the optical fiber unit. The flame-retardant sheath uses thermoplastic polyurethane elastomer as the matrix material and disperses composite flame-retardant filler therein. The composite flame-retardant filler is composed of inorganic phosphorus flame retardant, nitrogen flame retardant and nano-layered silicate.

[0011] A reinforcing member is arranged parallel to both sides of the optical fiber unit and embedded inside the flame-retardant sheath. The reinforcing member is a hybrid structure of aramid fiber and ceramic fiber.

[0012] A heat insulation buffer layer is disposed between the optical fiber unit and the flame-retardant sheath. The heat insulation buffer layer is a porous ceramic structure formed by foaming and curing an intumescent flame-retardant coating.

[0013] Preferably, the composite flame retardant filler is composed of inorganic phosphorus flame retardant, nitrogen flame retardant and nano-layered silicate in a mass ratio of 2:1:1, and the total amount of the composite flame retardant filler added is 25% to 35% of the mass of the thermoplastic polyurethane elastomer matrix.

[0014] Preferably, the inorganic phosphorus-based flame retardant is ammonium polyphosphate with a degree of polymerization n ≥ 1000, the nitrogen-based flame retardant is melamine cyanurate with a particle size D50 ≤ 5 μm, and the nano-layered silicate is organo-modified montmorillonite with an interlayer spacing increased to 2.5 nm to 3.5 nm.

[0015] Preferably, in the reinforcing member, the ratio of aramid fiber to ceramic fiber is 3:1, and the ceramic fiber is high-purity alumina fiber with an alumina content greater than 95%.

[0016] Preferably, the porosity of the heat insulation buffer layer is 60% to 80%;

[0017] The intumescent flame retardant coating comprises a char-forming agent, a foaming agent, a catalyst, and silicone rubber as a binder.

[0018] Preferably, the optical fiber unit, the reinforcing member, and the flame-retardant sheath are an integrated structure formed by synchronous co-extrusion, the quartz glass optical fiber in the optical fiber unit has a plasma-activated surface, and the high-temperature resistant acrylic resin coating is an ultraviolet-cured coating.

[0019] Preferably, the composite flame-retardant filler in the flame-retardant sheath is a homogeneous mixture of inorganic phosphorus-based flame retardant, nitrogen-based flame retardant, and nano-layered silicate formed by pre-ball milling.

[0020] Preferably, the surface of the reinforcing member is coated with a silane coupling agent treatment layer.

[0021] Preferably, the intumescent flame retardant coating further comprises fumed silica reinforcing filler, and the porous ceramic structure is a structure formed by foaming and ceramicizing the intumescent flame retardant coating at a temperature of 120°C to 150°C.

[0022] Preferably, the glass transition temperature (Tg) of the high-temperature resistant acrylic resin coating is not lower than 125°C.

[0023] (III) Beneficial Effects

[0024] This invention provides a flame-retardant butterfly-shaped optical cable for use in high-temperature environments. It has the following beneficial effects:

[0025] (1) The present invention achieves a flame retardant sheath material with superior flame retardant efficiency and anti-dripping effect compared to a single flame retardant by uniformly dispersing a composite flame retardant filler composed of inorganic phosphorus flame retardant, nitrogen flame retardant and nano-layered silicate in a thermoplastic polyurethane elastomer matrix, and achieves V-0 level vertical combustion, thus avoiding the ignition of cotton by molten droplets.

[0026] (2) By setting a porous ceramic heat insulation buffer layer between the optical fiber unit and the flame-retardant sheath, the present invention can effectively block heat at a high temperature of 800°C, so that the surface temperature rise of the optical fiber unit is low, avoiding optical signal interruption caused by optical fiber melting, and the high temperature additional attenuation at 150°C is extremely low, thus protecting the stability of the optical fiber at high temperature.

[0027] (3) The present invention uses a hybrid structure of aramid fiber bundles and ceramic fibers as a reinforcing component, which solves the problem that aramid will decompose and fail after exceeding 500°C, and makes the strength retention rate of the optical cable greater than 80% after high temperature treatment at 800°C. This is necessary for the optical cable to maintain structural integrity after high temperature and fire. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the optical cable structure frame of the present invention;

[0029] Figure 2 This is a schematic diagram of the optical cable manufacturing method 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.

[0031] Please see Figure 1 - Figure 2 This invention provides a flame-retardant butterfly-shaped optical cable for high-temperature environments, comprising:

[0032] An optical fiber unit, which consists of at least one quartz glass optical fiber, the surface of which is coated with a high-temperature resistant acrylic resin coating with a coating thickness of 30μm to 50μm;

[0033] The flame-retardant sheath covers the outside of the optical fiber unit. The flame-retardant sheath uses thermoplastic polyurethane elastomer as the matrix material and uniformly disperses composite flame-retardant filler in it. The composite flame-retardant filler is composed of inorganic phosphorus flame retardant, nitrogen flame retardant and nano-layered silicate in a mass ratio of 2:1:1.

[0034] The reinforcing member is arranged in parallel on both sides of the optical fiber unit. The reinforcing member is a hybrid structure of aramid fiber bundle and ceramic fiber with a hybrid ratio of aramid fiber to ceramic fiber of 3:1. The reinforcing member is completely embedded inside the flame-retardant sheath.

[0035] A heat insulation buffer layer is placed between the optical fiber unit and the flame-retardant sheath. The heat insulation buffer layer is a porous ceramic structure formed by foaming and curing of an intumescent flame-retardant coating. Its porosity is 60% to 80% and the pore size distribution ranges from 5μm to 50μm.

[0036] Based on the above, the present invention also provides a method for preparing a flame-retardant butterfly-shaped optical cable for high-temperature environments, specifically including the following steps:

[0037] S1: Single-mode silica glass optical fiber conforming to ITU-T G.657.A1 standard was selected as the base material. The mode field diameter was 8.6μm to 9.5μm at a wavelength of 1310nm, and the cladding diameter was 125.0μm±0.7μm. The optical fiber underwent surface cleaning and plasma activation treatment. The cleaning process adopted a two-stage solvent cleaning. First, isopropanol was used for ultrasonic cleaning for 5 minutes to remove organic contaminants. Then, deionized water was used to rinse away ion residues. Subsequently, it was placed in a low-pressure radio frequency plasma treatment device and treated with 100W power for 120 seconds under an argon atmosphere to increase the surface energy of the optical fiber to above 70mN / m, thereby enhancing the coating adhesion. The coating process adopted a precision ultraviolet curing system. The viscosity of the high-temperature resistant acrylic resin coating was 1200cP to 1500cP. The coating was carried out through a precision metering pump and a coating mold, and the coating speed was controlled at 2m / s to 3m / s.

[0038] The UV curing employs a two-stage curing strategy. The first stage of curing uses a UV-LED light source with a wavelength of 365nm, and the curing energy is strictly controlled within the range of 300mJ / cm² to 400mJ / cm² to induce initial gelation of the coating. The second stage of curing uses a UV-LED light source with a wavelength of 395nm, and the curing energy is increased to 500mJ / cm² to 600mJ / cm² to achieve complete cross-linking and curing of the coating.

[0039] The final coating thickness was monitored online using a laser thickness gauge to ensure that it was uniformly distributed between 30μm and 50μm. The glass transition temperature (Tg) of the coating of the fiber unit treated in this way was determined by differential scanning calorimetry to be no less than 125℃, and the additional loss in the 1550nm communication window was less than 0.03dB / km as measured by an optical time domain reflectometer, which met the optical performance requirements for long-term operation in high-temperature environments.

[0040] S2: Thermoplastic polyurethane elastomer particles with a Shore hardness of 80A to 85A are selected as the matrix material and placed in a circulating air drying oven at 90℃±5℃ for 2 hours to reduce the moisture content to below 0.02% to prevent air bubbles from forming during subsequent processing. The pretreatment of the composite flame-retardant filler is a key step, specifically:

[0041] The inorganic phosphorus-based flame retardant selected is ammonium polyphosphate with a degree of polymerization n ≥ 1000 and a phosphorus content greater than 30 wt%.

[0042] The nitrogen-based flame retardant selected is melamine cyanurate with a particle size D50 ≤ 5 μm;

[0043] The nanolayered silicate was made from organo-modified montmorillonite treated with dioctadecyldimethylammonium chloride, and the interlayer spacing was increased to 2.8 nm to 3.2 nm by X-ray diffraction.

[0044] The three components were added to a planetary ball mill at a precise mass ratio of 2:1:1, using zirconia balls as the grinding medium, and ball-milled at 350 rpm for 2 hours to ensure that the filler achieved nanoscale dispersion and full activation. Subsequently, the dried thermoplastic polyurethane elastomer particles and the prepared composite flame-retardant filler were added to a high-speed mixer and mixed at 1000 rpm ± 200 rpm for 12 minutes ± 3 minutes. The total amount of composite flame-retardant filler added was strictly controlled to be 30% ± 5% of the mass of the thermoplastic polyurethane elastomer matrix. This ratio was optimized through orthogonal experiments, which can maintain the melt flow rate of the material within the range of 8 g / 10 min to 12 g / 10 min while ensuring flame retardant efficiency, in order to meet the requirements of subsequent extrusion processing.

[0045] S3: The reinforcing component adopts a hybrid structure of aramid fiber and ceramic fiber. The aramid fiber is para-aramid 1414 with a single filament fineness of 1250D and a breaking strength of not less than 23g / D. The ceramic fiber is high-purity alumina fiber with an alumina content greater than 95%, a diameter of 12μm±2μm, and a melting point higher than 1800℃. The aramid fiber and ceramic fiber are twisted in an exact mass ratio of 3:1 using a precision twisting machine in the S-direction, with the twist set to 80 twists / meter to 100 twists / meter, forming a tightly structured and uniformly sized reinforcing fiber bundle. The reinforcing fiber bundle is then surface-treated to enhance its interfacial adhesion with the sheath material. Specifically:

[0046] An ethanol solution of γ-aminopropyltriethoxysilane at a concentration of 1.0 wt% was used as the treatment agent. The fiber was treated by an impregnation-drying process, with an impregnation time of 30 seconds followed by drying at 110°C for 5 minutes. This process allowed the silane coupling agent to form a chemical bond layer on the fiber surface. The reinforced fiber bundle treated in this way showed an increase of more than 45% in the interfacial shear strength with thermoplastic polyurethane, as tested by a universal testing machine. The tensile strength was tested to be no less than 2500 MPa, and the strength retention rate was greater than 80% when tested by a thermogravimetric analyzer at a high temperature of 800°C.

[0047] S4: Employs a co-rotating twin-screw extruder with a length-to-diameter ratio of 38:1 and a screw speed set at 220 rpm ± 30 rpm. The flame-retardant sheath material undergoes precise temperature-controlled melting in six temperature zones within the extruder.

[0048] The temperature is set at 185℃ for each of the six zones: Zone 1: 165℃, Zone 2: 175℃, Zone 3: 180℃, Zone 4: 185℃, Zone 5: 185℃, and Zone 6: 180℃. The head temperature is set at 185℃. The cross-shaped head is optimized through computational fluid dynamics. The flow channel structure ensures that the molten sheath material can uniformly and symmetrically cover the fiber optic unit located in the center and the reinforcing members arranged in parallel and symmetrically on both sides. The speed of the traction device is set at 25m / min ± 5m / min. The outer diameter of the optical cable is monitored in real time by a laser diameter gauge to ensure that the coating thickness deviation is controlled within ±0.05mm. This forms a primary optical cable product with a standard butterfly cross-section and precise dimensions. The minor axis width of the butterfly cross-section is 2.0mm ± 0.1mm, and the major axis height is 3.0mm ± 0.1mm.

[0049] S5: In the primary optical cable product after co-extrusion molding, an annular gap is reserved between the optical fiber unit and the flame-retardant sheath. A pre-prepared intumescent flame-retardant coating is precisely injected into this gap using a micro-injection molding system. The coating formulation, by weight percentage, is as follows:

[0050] The carbonizing agent pentaerythritol accounts for 18%, the foaming agent melamine accounts for 12%, the catalyst ammonium polyphosphate accounts for 23%, the binder methyl vinyl silicone rubber accounts for 35%, and the reinforcing filler fumed silica accounts for 7%.

[0051] After injection, the optical cable immediately passes through a 10-meter-long infrared drying tunnel with zoned temperature control: 120℃ in the entrance zone, 140℃ in the center zone, and 130℃ in the exit zone. The optical cable is processed in the drying tunnel for 6 minutes ± 2 minutes. During this process, the coating undergoes a series of chemical reactions: the foaming agent decomposes to produce inert gas, the catalyst promotes the dehydration and carbonization of the charring agent, and the binder ensures structural integrity. Ultimately, a porous ceramic thermal insulation buffer layer with a porosity of 70% ± 10% and a pore size distribution range of 5μm to 50μm is formed. This structure expands to 3 to 5 times its original volume at high temperatures, effectively blocking the transfer of heat to the internal optical fiber units.

[0052] S6: The formed optical cable is cooled and shaped in a water-cooling tank, with the cooling water temperature controlled between 15℃ and 25℃; specifications, model, and meter marking information are printed on the sheath surface using a laser marking machine; the optical cable is then cut into standard coil lengths using a fixed-length cutting machine; performance testing is performed in accordance with national and international standards.

[0053] The flame retardant performance is tested according to GB / T18380.12-2008. The sample is tilted horizontally at 45 degrees, a flame is applied for 30 seconds, and after the flame is removed, the flame burning time of the sample does not exceed 10 seconds and the flameless burning time does not exceed 30 seconds. The dripping material does not ignite the degreased cotton below, achieving the highest flame retardant rating of FV-0.

[0054] The optical transmission performance was tested according to IEC60793-2-50 at wavelengths of 1310nm and 1550nm, with attenuation coefficients ensuring no greater than 0.36dB / km and 0.22dB / km, respectively.

[0055] Mechanical and physical properties are tested according to GB / T2951.32-2008, including tensile, flattening, and repeated bending tests. When the optical cable is subjected to a tensile force of 600N, the fiber strain is no greater than 0.15%, and when it is subjected to a pressure of 1000N / 10cm, the additional attenuation of the optical fiber is no greater than 0.05dB.

[0056] Example 1:

[0057] The preparation method provided in this embodiment is the same as the above scheme except for the following limitations:

[0058] 1. Step S120 (Flame-retardant sheath material): The total amount of composite flame-retardant filler added is 30% of the mass of thermoplastic polyurethane elastomer matrix. In the composite flame-retardant filler, the mass ratio of inorganic phosphorus flame retardant (ammonium polyphosphate, n≥1000), nitrogen flame retardant (melamine cyanurate, D50≤5μm) and nano-layered silicate (organic montmorillonite, interlayer spacing 2.8nm) is 2:1:1.

[0059] 2. Step S130 (Reinforcing Components): The blending ratio of aramid fiber (1250D) to ceramic fiber (alumina content >95%, diameter 12μm) is 3:1.

[0060] 3. Step S150 (heat insulation buffer layer): After the intumescent flame retardant coating is injected, it foams and cures to form a porous ceramic structure with a porosity of 70%.

[0061] Example 2:

[0062] This embodiment is basically the same as Embodiment 1, the main difference being the adjustment of the total amount of composite flame-retardant filler and the porosity of the heat insulation buffer layer, in order to verify the effectiveness of the scope of the present invention. The specific details are as follows:

[0063] 1. Step S120 (Flame-retardant sheath material): The total amount of composite flame-retardant filler added is adjusted to 25% of the mass of thermoplastic polyurethane elastomer matrix, and the mass ratio of composite flame-retardant filler remains 2:1:1.

[0064] 2. Step S150 (heat insulation buffer layer): By adjusting the temperature and time of the drying tunnel, a porous ceramic structure with a porosity of 60% is formed.

[0065] 3. All other steps and parameters are the same as in Example 1.

[0066] Example 3:

[0067] This embodiment is basically the same as Embodiment 1, the main difference being the further adjustment of the total amount of composite flame-retardant filler and the porosity of the heat insulation buffer layer:

[0068] 1. Step S120 (Flame-retardant sheath material): The total amount of composite flame-retardant filler added is adjusted to 35% of the mass of thermoplastic polyurethane elastomer matrix, and the mass ratio of composite flame-retardant filler remains 2:1:1.

[0069] 2. Step S150 (heat insulation buffer layer): By adjusting the temperature and time of the drying tunnel, a porous ceramic structure with a porosity of 80% is formed.

[0070] 3. All other steps and parameters are the same as in Example 1.

[0071] Comparative Example 1: Sheath using a single flame retardant. Specifically, the difference between this comparative example and Example 1 lies in step S120 (flame retardant sheath material): the flame retardant sheath material does not use the composite flame retardant filler of the present invention. Instead, it uses a conventional single flame retardant solution in the art, adding 30% by mass of ammonium polyphosphate (APP) to the thermoplastic polyurethane elastomer matrix. The other steps (including reinforcing member S130, heat insulation buffer layer S150, etc.) are exactly the same as in Example 1.

[0072] Comparative Example 2: No heat insulation buffer layer is set. Specifically:

[0073] The difference between this comparative example and Example 1 lies in step S150 (heat insulation buffer layer): step S150 is omitted, that is, the intumescent flame retardant coating is not injected through microporous injection molding process, and a porous ceramic heat insulation buffer layer is not formed. The optical cable structure is that the optical fiber unit is directly covered by the flame retardant sheath (composition is the same as in Example 1) and the reinforcing member (composition is the same as in Example 1), and there is no special heat insulation structure between the optical fiber unit and the sheath.

[0074] Comparative Example 3: Using a single aramid fiber reinforcing component, specifically:

[0075] The difference between this comparative example and Example 1 lies in step S130 (reinforcing member): the reinforcing member does not adopt a mixed structure of aramid fiber and ceramic fiber. Instead, it adopts 100% aramid fiber bundles (with the same specifications as the aramid fiber in Example 1) as the reinforcing member, and its total fineness is comparable to that of the mixed structure in Example 1. Other steps (including flame-retardant sheath S120, heat insulation buffer layer S150, etc.) are exactly the same as in Example 1.

[0076] To verify the superiority of the embodiments of the present invention compared with the comparative examples, the optical cable samples prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. The specific tests are as follows:

[0077] Experiment 1: Performance Testing of Sheath Material

[0078] The flame retardant and mechanical properties of the sheath materials used in Examples 1-3 and Comparative Example 1 were tested respectively, and the results are shown in Table 1:

[0079] Limiting Oxygen Index (LOI) / % 34.5 32.8 35.2 28.5 GB / T2406.2 Vertical burning (UL-94) V-0 V-0 V-0 V-2 (Molten Droplet Ignition) GB / T2408 Tensile strength / MPa 18.5 19.2 17.8 18.1 GB / T1040.2 Elongation at break / % 420 450 405 415 GB / T1040.2

[0080] Table 1

[0081] Data Analysis:

[0082] 1. Flame retardancy: The LOI of Examples 1-3 (using composite flame retardants) is much higher than that of Comparative Example 1, and all reach the V-0 level; while the LOI of Comparative Example 1 is lower, and it generates molten droplets that ignite cotton when burning vertically, and is only at the V-2 level. This proves that the phosphorus-nitrogen-silicon synergistic composite flame retardant system (APP+MCA+MMT) of the present invention has better flame retardant efficiency and drip suppression effect than APP alone.

[0083] Mechanical properties: Examples 1-3 maintained excellent tensile strength and elongation at break within the range of 25% to 35% flame retardant filler content, meeting the mechanical requirements of optical cable sheaths.

[0084] Experiment 2: High-Temperature Performance Test of the Entire Optical Cable

[0085] Key performance tests were conducted on the optical cable samples under high-temperature conditions, including thermal insulation, high-temperature additional attenuation, and mechanical strength retention rate after high temperature, as shown in Table 2:

[0086] Thermal insulation performance (temperature rise on the surface of the fiber optic unit) 165°C 180°C 155°C >650°C (fiber optic cable melted) 168°C 800°C / 10min Additional degradation at high temperatures (1550nm) ≤0.03dB / km ≤0.04dB / km ≤0.02dB / km Unable to measure (fiber optic cable damaged) ≤0.03dB / km 150°C / 2h Strength retention rate after high temperature 83.5% 81.2% 85.1% 82.9% 18.4% 800°C / 30min

[0087] Table 2

[0088] Data Analysis:

[0089] 1. Thermal insulation and high-temperature attenuation: At 800°C, Examples 1-3 effectively blocked heat, and the surface temperature rise of the optical fiber unit was controlled below 200°C; while the optical fiber unit of Comparative Example 2 (without this buffer layer) rapidly heated up to the point of melting, resulting in optical signal interruption. Similarly, at 150°C, the additional attenuation of Examples 1-3 was extremely low, indicating that the structure of the present invention can effectively protect the stability of optical fiber at high temperatures (Tg>125°C), which proves the key thermal insulation role of the porous ceramic thermal insulation buffer layer.

[0090] 2. Strength Retention Rate After High Temperature Treatment: After treatment at 800°C, the strength retention rates of Examples 1-3 and Comparative Example 2 were all greater than 80%; however, the strength retention rate of Comparative Example 3 dropped sharply to less than 20%. This is because aramid fibers decompose and fail at temperatures exceeding 500°C, while ceramic fibers retain their strength. This demonstrates the necessity of aramid-ceramic hybrid reinforcing components for maintaining the structural integrity of optical cables after high temperatures and fires.

[0091] Experiment 3: Summary of Overall Optical Cable Performance

[0092] The comprehensive performance evaluation of finished optical cables was conducted according to standards such as GB / T18380.12. Details are shown in the table below:

[0093] Vertical combustion (GB / T18380.12) Passed (FV-0 level) Passed (FV-0 level) Passed (FV-0 level) It does not pass through (molten droplets). Passed (FV-0 level) Passed (FV-0 level) Thermal insulation performance (800°C) pass pass pass pass Failed (melted) pass Strength after high temperature (800°C) Pass (>80%) Pass (>80%) Pass (>80%) Pass (>80%) Pass (>80%) Failed (<20%)

[0094] Table 3

[0095] Overall conclusion:

[0096] 1. Embodiments 1-3 of the present invention combine three major technical features: phosphorus-nitrogen-silicon composite flame-retardant sheath, aramid-ceramic hybrid reinforcing component, and porous ceramic thermal insulation buffer layer.

[0097] 2. The test results show that Examples 1-3 performed excellently in all key performance aspects and met the requirements for use in harsh high-temperature environments.

[0098] 3. Comparative Example 1 failed the flame retardant test; Comparative Example 2 failed the thermal insulation performance test; and Comparative Example 3 failed the high-temperature strength test.

[0099] 4. This fully demonstrates that each component of the technical solution of this invention is indispensable. It is precisely because of the synergistic effect of these key technical features that the optical cable product of this invention has significant performance advantages and practical value compared with the prior art.

[0100] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A flame-retardant butterfly-shaped drop optical cable for use in high-temperature environments, characterized in that, It includes the following components: An optical fiber unit, wherein the optical fiber unit is composed of at least one quartz glass optical fiber, and the surface of the optical fiber is coated with a high-temperature resistant acrylic resin coating with a coating thickness of 30 μm to 50 μm; A flame-retardant sheath is provided, which covers the outside of the optical fiber unit. The flame-retardant sheath uses thermoplastic polyurethane elastomer as the matrix material and disperses composite flame-retardant filler therein. The composite flame-retardant filler is composed of inorganic phosphorus flame retardant, nitrogen flame retardant and nano-layered silicate. A reinforcing member is arranged parallel to both sides of the optical fiber unit and embedded inside the flame-retardant sheath. The reinforcing member is a hybrid structure of aramid fiber and ceramic fiber. A heat-insulating buffer layer is disposed between the optical fiber unit and the flame-retardant sheath. The heat-insulating buffer layer is a porous ceramic structure formed by foaming and curing an intumescent flame-retardant coating. In the reinforcing component, the ratio of aramid fiber to ceramic fiber is 3:1, and the ceramic fiber is high-purity alumina fiber with an alumina content greater than 95%. The porosity of the heat insulation buffer layer is 60% to 80%; The intumescent flame-retardant coating comprises a char-forming agent, a foaming agent, a catalyst, and silicone rubber as a binder; The optical fiber unit, the reinforcing member, and the flame-retardant sheath are an integrated structure formed by synchronous co-extrusion. The quartz glass optical fiber in the optical fiber unit has a plasma-activated surface, and the high-temperature resistant acrylic resin coating is a UV-cured coating.

2. The flame-retardant butterfly-shaped drop optical cable for high-temperature environments according to claim 1, characterized in that: The composite flame retardant filler is composed of inorganic phosphorus flame retardant, nitrogen flame retardant and nano-layered silicate in a mass ratio of 2:1:1, and the total amount of the composite flame retardant filler added is 25% to 35% of the mass of the thermoplastic polyurethane elastomer matrix.

3. The flame-retardant butterfly-shaped drop cable for high-temperature environments according to claim 2, characterized in that: The inorganic phosphorus-based flame retardant is ammonium polyphosphate with a degree of polymerization n≥1000, the nitrogen-based flame retardant is melamine cyanurate with a particle size D50≤5 μm, and the nano-layered silicate is organic montmorillonite with an interlayer spacing increased to 2.5nm to 3.5nm.

4. The flame-retardant butterfly-shaped drop optical cable for high-temperature environments according to any one of claims 1-2, characterized in that: The composite flame-retardant filler in the flame-retardant sheath is a homogeneous mixture of inorganic phosphorus-based flame retardants, nitrogen-based flame retardants, and nano-layered silicates formed by pre-ball milling.

5. The flame-retardant butterfly-shaped drop optical cable for high-temperature environments according to any one of claims 1-2, characterized in that: The surface of the reinforcing member is coated with a silane coupling agent treatment layer.

6. The flame-retardant butterfly-shaped drop optical cable for high-temperature environments according to any one of claims 1-2, characterized in that: The intumescent flame retardant coating also includes fumed silica reinforcing filler, and the porous ceramic structure is a structure formed by foaming and ceramicizing the intumescent flame retardant coating at a temperature of 120°C to 150°C.

7. The flame-retardant butterfly-shaped drop cable for high-temperature environments according to any one of claims 1-2, characterized in that: The glass transition temperature (Tg) of the high-temperature resistant acrylic resin coating is not lower than 125°C.

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