B1-level flame-retardant butterfly-shaped optical cable and preparation process thereof

Abstract

The invention relates to the technical field of flame-retardant optical cable preparation, and discloses a B1-level flame-retardant butterfly-shaped optical cable and a preparation process thereof.The B1-level flame-retardant butterfly-shaped optical cable comprises a flame-retardant sheath, optical fibers and glass yarn, and the flame-retardant sheath is prepared from, by weight, 40-45 parts of modified low-density polyethylene; 25 to 30 parts of nanoscale magnesium hydroxide; 10 to 12 parts of ammonium polyphosphate; 5-7 parts of modified expanded graphite; 3 to 4 parts of organic silicon modified melamine; 2-3 parts of a zinc-boron synergist; 2 to 3 parts of maleic anhydride grafted polyethylene; 1 to 2 parts of an antioxidant; the preparation process comprises the steps of surface modification and microencapsulation treatment, preparation of flame-retardant composite material particles, and optical cable forming, cooling and testing. The surface modification technology of the nanoscale magnesium hydroxide is adopted, the modified magnesium hydroxide improves the flame retardant effect, the fluidity in the processing process is also improved, and the processing problem caused by particle aggregation is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of flame-retardant optical cable preparation, specifically to a B1-class flame-retardant butterfly optical cable and its preparation process. Background Art

[0002] The application of flame-retardant materials is particularly important in modern materials science, especially in fields such as construction, electronics, and transportation, where the demand for flame-retardant properties is increasingly stringent. Magnesium hydroxide, a common inorganic flame retardant, is widely used in various composite materials, including plastics, rubber, and fibers, due to its low cost, non-toxicity, and environmental friendliness. While magnesium hydroxide inhibits flame spread through heat absorption and chemical reactions, its limited flame-retardant effect and poor dispersibility often limit its application in high-performance materials.

[0003] Existing flame-retardant technologies mostly rely on directly adding flame retardants such as magnesium hydroxide and ammonium polyphosphate to the substrate material. These materials are often produced using simple physical mixing or extrusion processes, with magnesium hydroxide as the primary flame-retardant additive. This traditional method often results in aggregation of magnesium hydroxide particles, leading to poor dispersion and impacting overall performance. Ammonium polyphosphate, another commonly used flame retardant, is typically mixed directly into the substrate at high concentrations, enhancing flame retardancy by releasing phosphoric acid at high temperatures.

[0004] However, in the existing B1-class flame-retardant butterfly optical cable preparation process, the magnesium hydroxide used is usually not surface-modified, resulting in poor dispersibility and difficulty in uniform distribution in the composite material, thereby affecting the thermal stability and flame retardant effect of the material. The direct addition of ammonium polyphosphate makes it difficult to effectively control its release rate at high temperatures, which leads to unstable flame retardant effects of the material and makes it difficult to meet the fire protection requirements under long-term high-temperature conditions. In addition, when processing composite materials containing a large amount of flame retardants in the existing extrusion process, uneven flow, bubbles, and blockages often occur, seriously affecting production efficiency and material molding quality. Therefore, the present invention provides a B1-class flame-retardant butterfly optical cable and a preparation process thereof to address the shortcomings of the prior art. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the purpose of this application is to provide a B1-level flame-retardant butterfly optical cable and its preparation process, which solves the problems of poor flame retardant dispersibility, low processing stability and insufficient flame retardant performance sustainability of the B1-level flame-retardant butterfly optical cable prepared by the existing preparation process.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A B1-class flame-retardant butterfly optical cable, comprising a flame-retardant sheath, optical fiber and glass yarn, wherein the flame-retardant sheath is composed of the following components in parts by weight: Modified low-density polyethylene: 40-45 parts; Nano-magnesium hydroxide: 25-30 parts; Ammonium polyphosphate: 10-12 parts; Modified expanded graphite: 5-7 parts; Silicone modified melamine: 3-4 parts; Zinc-boron synergist: 2-3 parts; Maleic anhydride grafted polyethylene: 2-3 parts; Antioxidant: 1-2 parts; Lubricant: 1-2 parts.

[0007] Modified low-density polyethylene (LDPE): 40-45 parts, serving as the matrix material, provides excellent processing properties and mechanical strength. The introduction of polar groups into the modified LDPE enhances its compatibility with inorganic flame retardants, improving the uniformity and stability of the composite while maintaining good flexibility and weather resistance.

[0008] Nano-magnesium hydroxide: 25-30 parts, as the primary flame retardant, decomposes at high temperatures, absorbing heat and releasing water molecules, reducing the surface temperature of the material and diluting the combustible gases in the combustion area. Nano-particle size of 50-100nm provides a larger specific surface area and more uniform dispersion, enhancing flame retardancy while reducing the negative impact on mechanical properties.

[0009] Ammonium polyphosphate: 10-12 parts. This intumescent flame retardant decomposes at high temperatures to produce phosphoric acid and polyphosphoric acid, promoting the formation of a carbonized layer on the surface. The 20-30μm microencapsulation structure improves water resistance and thermal stability, slowing the release rate of the flame retardant and achieving a sustained flame retardant effect.

[0010] Modified expanded graphite: 5-7 parts. Modified expanded graphite rapidly expands dozens of times its volume at high temperatures, forming a worm-like porous insulation layer that blocks oxygen and heat transfer. It works synergistically with nano-magnesium hydroxide to strengthen the carbonized barrier structure on the material surface.

[0011] Silicone-modified melamine: 3-4 parts. Silicone-modified melamine releases non-flammable nitrogen to dilute combustible gases, while promoting the formation of more stable phosphorus-nitrogen compounds from phosphorus-based flame retardants. Silicone modification improves its compatibility with the polymer matrix, reducing migration and precipitation.

[0012] Zinc-boron synergist: 2-3 parts, through the synergistic effect of zinc oxide and borate in a ratio of 1.0-1.2:1.5-2.0, it promotes the densification and stabilization of the carbonized layer, improves the strength and thermal insulation performance of the carbon layer, and inhibits the release of smoke.

[0013] Maleic anhydride grafted polyethylene: 2-3 parts, as a compatibilizer, it improves the interfacial compatibility between the organic matrix and the inorganic flame retardant through polar groups, improves dispersibility, reduces stress concentration, and improves the overall mechanical properties of the material.

[0014] Antioxidant: 1-2 parts, inhibits the oxidative degradation of polymers during processing and use, improves the thermal stability and aging resistance of materials, and extends the service life of products.

[0015] Lubricant: 1-2 parts, improves material fluidity and demoulding performance, reduces friction and shear heat during processing, avoids premature decomposition of flame retardants, and ensures product surface quality.

[0016] Preferably, the particle size of the nano-magnesium hydroxide is 50-100 nm, and KH-550 silane coupling agent is grafted on the surface. The addition amount of the KH-550 silane coupling agent is 2.5-4.0% of the weight of the nano-magnesium hydroxide.

[0017] Preferably, the ammonium polyphosphate is a microencapsulated structure, the microcapsule wall material is a polyurethane-siloxane copolymer, the microcapsule wall material accounts for 10-15% of the total weight of the microcapsule, and the average particle size of the microcapsule is 20-30 μm.

[0018] Preferably, the weight ratio of the organosilicon-modified melamine to the zinc-boron synergist is 1.0-1.5:0.6-0.8, the zinc-boron synergist consists of zinc oxide and borate, and the weight ratio of the zinc oxide to borate is 1.0-1.2:1.5-2.0.

[0019] Preferably, the outer layer thickness of the flame retardant sheath is 0.4-0.6 mm, and the overall diameter is 3.0±0.1 mm.

[0020] A preparation process for a B1-class flame-retardant butterfly optical cable is also provided, comprising the following steps: S1. Surface-modifying nano-magnesium hydroxide and microencapsulating ammonium polyphosphate, and ultrasonically dispersing the modified nano-magnesium hydroxide to form a uniform dispersion; S2. Mixing the formed uniform dispersion with modified low-density polyethylene, and then sequentially adding organosilicon-modified melamine and zinc-boron synergist, and forming the mixture by multi-zone temperature-controlled extrusion to obtain flame-retardant composite material particles; S3, placing the optical fiber in a loose tube and filling it with fluorosilicone gel, arranging a glass fiber yarn reinforcement, and extruding the prepared flame retardant composite material particles through a butterfly die; S4. Use gradient cooling to shape and make B1-level flame-retardant butterfly-shaped optical cables, and perform flame-retardant and mechanical property tests on the prepared B1-level flame-retardant butterfly-shaped optical cables.

[0021] Specifically, for step S1, 0.8-1.2 parts by weight of KH-550 silane coupling agent is used to modify the surface of nano-magnesium hydroxide, and the reaction is stirred at 60-70°C for 2-3 hours. The silane coupling agent forms a chemical bonding layer on the surface of nano-magnesium hydroxide, one end of which is bonded to the inorganic particles and the other end is compatible with the organic matrix, significantly improving the dispersibility of the nanoparticles and the interfacial bonding strength with the polymer matrix. At the same time, through interfacial polymerization, polyurethane-siloxane copolymer is used as the wall material, and the reaction is carried out at 40-50°C for 4-6 hours to achieve microencapsulation of ammonium polyphosphate. The microcapsule structure effectively prevents the performance degradation of ammonium polyphosphate caused by contact with moisture, improves its water resistance and thermal stability, and delays the release rate of the flame retardant. Ultrasonic dispersion at 20-25kHz for 15-20 minutes breaks up the particle agglomeration through the cavitation effect, ensuring the uniform distribution of the nanoparticles in the system.

[0022] For step S2, gradient temperature control multi-zone mixing technology is adopted, and 6 temperature intervals of 160-185°C are set to achieve orderly addition and thorough mixing of the components. Silicone-modified melamine and zinc-boron synergist are added in the third temperature zone to fully mix with the components added earlier while avoiding premature decomposition. The shear force fluctuations generated by the pulse extrusion technology of 0.7-0.9Hz enhance the mixing effect while avoiding material degradation caused by continuous high shear. Controlling the screw speed of 40-50rpm and the material residence time of 2-3 minutes balances the mixing uniformity and the risk of thermal degradation. Vacuum drying for 4-6 hours after underwater pelletizing ensures that the moisture content of the pellets is less than 0.05%.

[0023] In step S3, fluorosilicone gel filling provides buffering and waterproofing for the optical fiber. The symmetrical arrangement of glass fiber reinforcements enhances the cable's tensile strength and bending resistance. The flame-retardant composite material is melt-extruded at 175-185°C, and the butterfly-shaped die design ensures uniform coverage of the material over the cable core structure.

[0024] In step S4, a three-stage cooling system (45-50°C → 30-35°C → 15-20°C) achieves a gradient cooling of the material, effectively reducing internal stress, preventing cable deformation and warping, and improving product dimensional stability and surface quality. Comprehensive product performance is evaluated through oxygen index testing, smoke density testing, tensile strength testing, and bending performance testing to ensure that the product meets the B1 flame retardant standard and optical cable requirements. Strictly controlled testing conditions of 23±2°C and 50±5% relative humidity ensure the accuracy and repeatability of test results.

[0025] Preferably, in step S1, the surface modification of nano-magnesium hydroxide and microencapsulation of ammonium polyphosphate include the following steps: Disperse nano-magnesium hydroxide in ethanol, add 0.8-1.2 parts by weight of KH-550 silane coupling agent, stir and react at 60-70°C for 2-3 hours, filter, wash and dry to obtain surface-modified nano-magnesium hydroxide; Adopting interfacial polymerization method, using polyurethane-siloxane copolymer as wall material, controlling reaction temperature at 40-50°C, reaction time at 4-6 hours, to obtain microencapsulated ammonium polyphosphate, wherein the microcapsule wall material accounts for 10-15% of the total weight; The surface-modified nano-magnesium hydroxide and the modified expanded graphite are mixed in a weight ratio of 3:1-5:1, and dispersed for 15-20 minutes at an ultrasonic frequency of 20-25 kHz to form a uniform dispersion.

[0026] Preferably, in step S2, the preparation of flame-retardant composite material particles comprises the following steps: Adopt gradient temperature control multi-zone mixing technology, set 6 temperature intervals, the temperatures are 160-165℃, 165-170℃, 170-175℃, 175-180℃, 170-175℃, 165-170℃; Adding organosilicon-modified melamine and zinc-boron synergist in the third temperature zone, with the weight ratio of organosilicon-modified melamine to zinc-boron synergist being 1.0-1.5:0.6-0.8, adding maleic anhydride-grafted polyethylene in the fourth temperature zone, and adding antioxidant and lubricant in the fifth temperature zone; Pulse extrusion technology is used, the pulse frequency is set to 0.7-0.9Hz, the screw speed is controlled to 40-50rpm, the material residence time is controlled to 2-3 minutes, and the flame retardant composite material particles are obtained after underwater pelletizing and vacuum drying for 4-6 hours.

[0027] Preferably, in step S3, the extrusion molding of the prepared flame-retardant composite material particles through a butterfly die comprises the following steps: Place the single-mode optical fiber in a loose tube, inject fluorosilicone gel filler, seal it, and arrange the glass fiber yarns parallel and symmetrically on both sides of the loose tube. Use a positioning device to ensure the accurate position of the glass fiber yarns. Add the flame retardant composite material particles into the extruder, control the extrusion temperature at 175-185℃, use a specially designed butterfly die for extrusion, and control the extrusion speed at 5-8m / min.

[0028] Preferably, in step S4, the flame retardant and mechanical property tests of the prepared B1-grade flame retardant butterfly optical cable include the following steps: Flame retardant performance test: Cut B1 flame-retardant butterfly optical cable samples into specimens with a length of 100-120mm and a width of 6.5±0.5mm. Test them in an oxygen index meter at a controlled temperature of 23±2°C, a relative humidity of 50±5%, and an ignition time of 30-180 seconds to determine the minimum oxygen concentration at which the sample can sustain combustion in an oxygen / nitrogen mixture. Mechanical properties test: The optical cable samples were pre-treated in a constant temperature and humidity environment for 24 hours, and the tensile strength test was performed on a universal material testing machine with a loading rate of 50-100 mm / min and a test sample length of 500±10 mm.

[0029] In summary, this application includes at least one of the following beneficial technical effects: 1. This invention utilizes surface modification technology for nano-magnesium hydroxide, significantly improving its dispersibility in composite materials and its compatibility with other ingredients. This improvement enables the material to absorb heat and release moisture more evenly under high-temperature conditions, thereby enhancing its flame retardant properties. Compared to conventional magnesium hydroxide that has not undergone surface modification, the modified magnesium hydroxide not only exhibits enhanced flame retardancy but also improves its fluidity and stability during processing, effectively avoiding processing problems caused by particle aggregation.

[0030] 2. This invention utilizes ammonium polyphosphate microencapsulation technology. By encapsulating ammonium polyphosphate in microcapsules, its slow release at high temperatures is effectively controlled. This technology enables ammonium polyphosphate to maintain its flame retardant effect during fires and significantly improves the thermal stability of the material. Compared to traditional methods that directly use ammonium polyphosphate, microencapsulation not only improves the heat resistance of the flame retardant, but also avoids negative effects on the mechanical properties of the composite material, ensuring the material's long-lasting flame retardancy.

[0031] 3. This invention improves the processing performance of the material through an optimized extrusion process and composite material formulation. The precise temperature-controlled extrusion process ensures uniform material flow during extrusion, avoiding surface unevenness or uneven flow. This optimized technology not only enhances the flame retardancy of the final product but also makes the processing more efficient, avoiding the production instability and waste caused by uneven material dispersion in traditional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of the preparation process of this application. DETAILED DESCRIPTION

[0033] The following is combined with Figure 1 , further details of this application are given.

[0034] Please see the attached Figure 1 : Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0035] Example 1: Raw material components (by weight): Modified low-density polyethylene: 42.5 parts; Nano-magnesium hydroxide: 27.5 parts; Ammonium polyphosphate: 11 parts; Modified expanded graphite: 6 parts; Silicone modified melamine: 3.5 parts; Zinc-boron synergist: 2.5 parts; Maleic anhydride grafted polyethylene: 2.5 parts; Antioxidant: 1.5 parts; Lubricant: 1.5 parts.

[0036] Preparation steps: S1. Surface modification and microencapsulation treatment: Nano-magnesium hydroxide particles with a diameter of 50-100 nm are dispersed in ethanol, 1.0 parts by weight of KH-550 silane coupling agent is added, and the mixture is stirred and reacted at 60-70° C. for 2 hours, filtered, washed, and dried to obtain surface-modified nano-magnesium hydroxide.

[0037] The interfacial polymerization method is used to take ammonium polyphosphate and polyurethane-siloxane copolymer as wall materials. The reaction temperature is controlled at 40°C and the reaction time is 5 hours to obtain microencapsulated ammonium polyphosphate with a microcapsule particle size of 20-30 μm.

[0038] S2. Preparation of flame retardant composite material particles: Surface-modified nano-magnesium hydroxide and modified expanded graphite (mixed in a weight ratio of 3:1) were dispersed at an ultrasonic frequency of 20-25 kHz for 15 minutes to form a uniform dispersion; The dispersion was molded together with modified low-density polyethylene, ammonium polyphosphate microcapsules, silicone-modified melamine and zinc-boron synergist through a multi-zone temperature-controlled extrusion process. The extrusion temperature was set at 165°C-175°C, the pulse extrusion frequency was 0.8Hz, and the screw speed was 45rpm, finally obtaining uniform flame-retardant composite material particles.

[0039] S3, Optical cable molding: The single-mode optical fiber is placed in a loose tube and filled with fluorosilicone gel to ensure good waterproof and buffer protection; The optical fiber and glass fiber yarn are arranged in parallel, and the glass fiber yarns on both sides of the optical fiber are positioned to ensure a symmetrical layout; Use a butterfly die for extrusion, control the temperature at 175-185℃, and the extrusion speed at 6m / min to ensure that the flame retardant composite material evenly covers the optical cable structure.

[0040] S4. Cooling and testing: A three-stage cooling system is adopted, with water temperatures of 50℃, 35℃ and 20℃ respectively. The cooling time is controlled within 30 seconds to ensure that the surface of the optical cable is smooth and the size is stable.

[0041] Oxygen index test and tensile strength performance test are carried out to ensure that the flame retardancy and mechanical properties of the optical cable meet the standards.

[0042] Example 2: Raw material components (by weight): Modified low-density polyethylene: 40 parts; Nano-magnesium hydroxide: 25 parts; Ammonium polyphosphate: 10 parts; Modified expanded graphite: 5 parts; Silicone modified melamine: 3 parts; Zinc-boron synergist: 2 parts; Maleic anhydride grafted polyethylene: 2 parts; Antioxidant: 1 part; Lubricant: 1 part.

[0043] Preparation steps: S1. Surface modification and microencapsulation treatment: Nano-magnesium hydroxide particles with a diameter of 50-100 nm are dispersed in ethanol, 0.8 parts by weight of KH-550 silane coupling agent are added, and the mixture is stirred and reacted at 60-70° C. for 2 hours, filtered, washed, and dried to obtain surface-modified nano-magnesium hydroxide.

[0044] The interfacial polymerization method is used to take ammonium polyphosphate and polyurethane-siloxane copolymer as wall materials. The reaction temperature is controlled at 40°C and the reaction time is 4 hours to obtain microencapsulated ammonium polyphosphate with a microcapsule particle size of 20-30 μm.

[0045] S2. Preparation of flame retardant composite material particles: The surface-modified nano-magnesium hydroxide and the modified expanded graphite are mixed in a weight ratio of 4:1 and dispersed at an ultrasonic frequency of 20-25 kHz for 15 minutes to form a uniform dispersion.

[0046] The dispersion was formed together with modified low-density polyethylene, ammonium polyphosphate microcapsules, silicone-modified melamine and zinc-boron synergist through a multi-zone temperature-controlled extrusion process. The extrusion temperature was set at 160°C, the pulse extrusion frequency was 0.7Hz, and the screw speed was 40rpm, finally obtaining uniform flame-retardant composite material particles.

[0047] S3, Optical cable molding: The single-mode optical fiber is placed in a loose tube and filled with fluorosilicone gel to ensure good waterproof and buffer protection; The optical fiber and glass fiber yarn are arranged in parallel, and the glass fiber yarns on both sides of the optical fiber are positioned to ensure a symmetrical layout; A butterfly die is used for extrusion, the temperature is controlled at 175°C, and the extrusion speed is controlled at 5m / min to ensure that the flame retardant composite material evenly covers the optical cable structure.

[0048] S4. Cooling and testing: A three-stage cooling system is used, with water temperatures at 45°C, 30°C, and 15°C, and the cooling time is controlled within 35 seconds to ensure a smooth surface and stable dimensions of the cable. Carry out performance tests such as oxygen index test and tensile strength test to ensure that the flame retardancy and mechanical properties of the optical cable meet the standards.

[0049] Example 3: Raw material components (by weight): Modified low-density polyethylene: 45 parts; Nano-magnesium hydroxide: 30 parts; Ammonium polyphosphate: 12 parts; Modified expanded graphite: 7 parts; Silicone modified melamine: 4 parts; Zinc-boron synergist: 3 parts; Maleic anhydride grafted polyethylene: 3 parts; Antioxidant: 2 parts; Lubricant: 2 parts.

[0050] Preparation steps: S1. Surface modification and microencapsulation treatment: Disperse nano-magnesium hydroxide particles with a diameter of 50-100 nm in ethanol, add 1.2 parts by weight of KH-550 silane coupling agent, stir and react at 60-70° C. for 3 hours, filter, wash and dry to obtain surface-modified nano-magnesium hydroxide; The interfacial polymerization method was used to prepare microencapsulated ammonium polyphosphate with ammonium polyphosphate and polyurethane-siloxane copolymer as wall materials. The reaction temperature was controlled at 50°C and the reaction time was 6 hours. The microencapsulated ammonium polyphosphate had a particle size of 20-30 μm.

[0051] S2. Preparation of flame retardant composite material particles: The surface-modified nano-magnesium hydroxide and the modified expanded graphite were mixed in a weight ratio of 3:1 and dispersed at an ultrasonic frequency of 20-25 kHz for 20 minutes to form a uniform dispersion; The dispersion was formed together with modified low-density polyethylene, ammonium polyphosphate microcapsules, silicone-modified melamine and zinc-boron synergist through a multi-zone temperature-controlled extrusion process. The extrusion temperature was set at 185°C, the pulse extrusion frequency was 0.9Hz, and the screw speed was 50rpm, finally obtaining uniform flame-retardant composite material particles.

[0052] S3, Optical cable molding: The single-mode optical fiber is placed in a loose tube and filled with fluorosilicone gel to ensure good waterproof and buffer protection; The optical fiber and glass fiber yarn are arranged in parallel, and the glass fiber yarns on both sides of the optical fiber are positioned to ensure a symmetrical layout; A butterfly die is used for extrusion, the temperature is controlled at 185°C, and the extrusion speed is controlled at 8m / min to ensure that the flame retardant composite material evenly covers the optical cable structure.

[0053] S4. Cooling and testing: A three-stage cooling system is used, with water temperatures at 50°C, 35°C, and 20°C, and the cooling time is controlled within 30 seconds to ensure a smooth surface and stable dimensions of the optical cable. Carry out performance tests such as oxygen index test and tensile strength test to ensure that the flame retardancy and mechanical properties of the optical cable meet the standards.

[0054] Comparative Example 1: Compared with Example 1, the difference is that the amount of modified low-density polyethylene used is reduced to 30 parts, and the rest are the same.

[0055] Comparative Example 2: Compared with Example 1, the difference is that the ammonium polyphosphate microencapsulation technology is not used, and the rest are the same.

[0056] Comparative Example 3: Compared with Example 1, the difference is that the surface modification treatment of magnesium hydroxide is not performed, and the rest are the same.

[0057] Comparative Example 4: Compared with Example 1, the difference is that the amount of zinc-boron synergist is reduced to 1 part, and the rest are the same.

[0058] Comparative Example 5: Compared with Example 1, the difference is that the amount of modified expanded graphite is reduced to 3 parts, and the rest are the same.

[0059] Comparative Example 6: Compared with Example 1, the difference is that the ultrasonic dispersion step is not used in the extrusion process, and the rest are the same.

[0060] Experiment 1: Experimental purpose: To compare the differences in flame retardancy between Example 1 and Comparative Examples 1 and 2, and to evaluate the flame retardancy of each formulation mainly through oxygen index test and thermogravimetric analysis.

[0061] Experimental steps: Oxygen index test: Prepare composite material test pieces with dimensions of 100 mm × 10 mm × 2 mm for each formulation. Prepare at least three test pieces for each formulation.

[0062] Place each sample in the oxygen index tester and test according to the instrument's standard operating procedures. During the test, gradually adjust the oxygen and nitrogen mixture ratio until the sample self-extinguishes or maintains combustion, and record the minimum oxygen concentration required.

[0063] Record the oxygen index of each formulation and ensure that each formulation is tested at least three times to obtain stable data.

[0064] Thermogravimetric analysis: Take a composite material sample of each formulation, about 10 mg, and place it evenly on the sample tray of the thermogravimetric analyzer.

[0065] The heating rate of the instrument was set to 10°C / min, and the temperature was raised from room temperature to 800°C. During the heating process, the mass change of the sample was recorded.

[0066] The mass changes at different temperatures were recorded, with particular attention paid to the mass losses at 400°C and 600°C, and their thermal stability and pyrolysis behavior were calculated.

[0067] The experimental results are shown in Table 1.

[0068] Table 1: Oxygen index and thermal gravimetric loss test data As can be seen from Table 1, the composite material of Example 1 shows excellent flame retardant properties, which is mainly due to its innovative formula design and preparation process. First, the surface modification of nano-magnesium hydroxide significantly improves its compatibility with other components, improves the overall dispersibility of the material, and thus improves the flame retardant performance of the material at high temperatures. Magnesium hydroxide, as an inorganic flame retardant, can release moisture and absorb heat in a fire, forming a protective layer to inhibit the spread of flames. Through surface modification, nano-magnesium hydroxide not only maintains its excellent heat absorption, but also effectively synergizes with other components such as ammonium polyphosphate microcapsules, expanded graphite, etc., further enhancing the flame retardant properties of the composite material.

[0069] The technology of microencapsulating ammonium polyphosphate is also a key innovation of this invention. Through microencapsulation, the release rate of ammonium polyphosphate is effectively controlled, allowing it to slowly release phosphoric acid in a fire, thereby forming phosphate compounds. These substances not only prevent heat transfer but also form a carbonized protective layer on the surface, further improving the material's fire resistance and self-extinguishing properties. The design of the microcapsules avoids the premature release of ammonium polyphosphate under normal conditions, allowing the material to maintain good flame retardancy even when exposed to a fire source for a long time. This innovative treatment method significantly improves the material's stability at high temperatures and enhances its long-lasting flame retardancy.

[0070] Compared with the samples in the comparative example, the composite material in Example 1 was able to achieve a higher value in the oxygen index test, indicating that it can still maintain good combustion suppression ability at lower oxygen concentrations. This phenomenon is closely related to the synergistic effect of magnesium hydroxide and ammonium polyphosphate microcapsules. During the fire process, magnesium hydroxide and ammonium polyphosphate microcapsules cooperate with each other, with magnesium hydroxide providing the necessary heat absorption and shielding effects, while ammonium polyphosphate plays a flame retardant and carbonization role under high temperature conditions through its slowly released phosphate. This synergistic effect not only effectively improves the flame retardancy of the composite material, but also delays the spread of flames, thereby significantly improving the safety of the material in practical applications.

[0071] Experiment 2: Experimental purpose: To compare the mechanical properties of Example 1 with Comparative Examples 3 and 4, and to evaluate the mechanical properties of the composite materials.

[0072] Experimental steps: Tensile strength test: Prepare tensile specimens of 150mm×25mm×2mm for each formulation according to the specified ratio. Prepare at least two specimens for each formulation. Place the prepared sample in a constant temperature and humidity chamber for 24 hours of environmental stability treatment to ensure the humidity and temperature consistency of the sample before testing; Clamp the sample in a tensile testing machine and apply tensile force until the sample breaks. Measure and record the maximum tensile force when the sample breaks, and calculate the tensile strength (unit: MPa); At least two specimens of each formulation were tested, the maximum tensile force of each specimen was recorded, and the average tensile strength was finally calculated.

[0073] Bending strength test: Prepare bending specimens of each formulation with a size of 120 mm × 20 mm × 3 mm, and prepare at least two specimens; Place the specimen on the support frame of the three-point bending tester and apply bending force until the specimen breaks or is significantly deformed; Record the bending stress and bending displacement of the sample before fracture and calculate its bending strength (unit: MPa); Carry out at least 2 tests, record the maximum flexural strength of each test, and finally calculate the average flexural strength of each formulation.

[0074] The experimental results are shown in Table 2.

[0075] Table 2: Tensile strength and flexural strength test data As shown in Table 2, the composite material of Example 1 shows excellent tensile strength and flexural strength, which can be attributed to the synergistic effect of the surface modification of magnesium hydroxide and ammonium polyphosphate microencapsulation technology. Surface-modified magnesium hydroxide improves its dispersibility in the composite material, allowing magnesium hydroxide particles to be more evenly distributed in the matrix, optimizing the interaction force between the components, thereby enhancing the mechanical strength of the material. Magnesium hydroxide can not only absorb heat at high temperatures, but also release moisture when burning to form a protective layer. This thermal barrier effect helps to improve the structural stability of the material and further enhances the tensile and flexural properties. By modification, its surface is more suitable for interaction with ammonium polyphosphate and other components, forming a stronger interface connection, thereby improving the overall toughness and crack resistance of the material.

[0076] Microencapsulation of ammonium polyphosphate is also a key factor in improving mechanical properties. Microencapsulation technology enables ammonium polyphosphate to slowly release its flame-retardant components during a fire, extending the material's flame-retardant duration. Under normal conditions, the presence of ammonium polyphosphate strengthens the material's structure by enhancing its carbonization. During this process, the stability of the microcapsules not only enhances the high-temperature release of ammonium polyphosphate but also reduces its interaction with the matrix material, thereby preventing increased brittleness. This technology enables composite materials to maintain good ductility and deformation resistance under mechanical load, which is crucial for improving the material's mechanical properties in practical applications.

[0077] In contrast, removing the surface modification of magnesium hydroxide or reducing the use of zinc-boron synergists resulted in a significant decrease in the mechanical properties of the material. In the absence of surface-modified magnesium hydroxide, the dispersibility of nano-magnesium hydroxide is reduced, and the aggregation phenomenon between particles makes the overall structure of the composite material unstable, resulting in a decrease in tensile strength and flexural strength. The role of zinc-boron synergists in composite materials is not only to provide synergy in the flame retardant process, but also to play a key role in the thermal stability and mechanical properties of the material. After reducing or removing these components, the tensile strength and flexural strength of the material are reduced, indicating that zinc-boron plays an indispensable role in optimizing mechanical properties.

[0078] Experiment 3: Purpose of the experiment: This experiment aims to compare the differences in processing performance and stability between Example 1 and Comparative Examples 5 and 6.

[0079] Experimental steps: Extrusion stability test: Prepare the raw materials of the composite materials according to the proportions of each formula, and ensure that the raw materials of all samples are properly mixed to achieve a uniform state before use; Set the temperature parameters of the extruder: set appropriate temperatures in different areas to ensure that the sample can be plasticized evenly during the extrusion process; Determine the extrusion frequency and screw speed: to ensure the fluidity and processing stability of the material; Start the extruder and observe whether the material has uneven flow, blockage or other abnormal phenomena during the entire extrusion process. Record the pressure and flow rate data to ensure that each sample is compared under the same conditions. Record the extrusion pressure and flow rate of different samples, as well as any abnormal conditions that occur during the extrusion process.

[0080] Molding accuracy test: After extrusion is completed, the material is passed through a special mold to form the optical cable; Using a standard butterfly die, the molten composite material is extruded and processed through a cooling system; The appropriate cooling rate and cooling temperature are set to ensure that the material will not be deformed due to excessive cooling during the molding process. The molded optical cable is dimensional tested using precision dimensional measuring instruments to check its outer diameter, thickness, and surface quality. Two tests are conducted to record the size and appearance of each sample after molding, with special attention paid to its surface smoothness and dimensional consistency.

[0081] The experimental results are shown in Table 3.

[0082] Table 3: Extrusion stability and molding accuracy test data As shown in Table 3, Example 1 shows excellent processing performance and stability, mainly through the innovative combination of surface modification of magnesium hydroxide and microencapsulation technology. Surface-modified magnesium hydroxide effectively improves its interfacial compatibility with other components, making the composite material more fluid during extrusion, stabilizing the extrusion pressure, and reducing the processing difficulties caused by uneven dispersion. The good dispersibility of magnesium hydroxide also ensures that it can release water evenly during extrusion and molding, plays a role in slow heat absorption and fire prevention, not only improving the thermal stability of the material, but also improving its fluidity and molding accuracy during processing.

[0083] Ammonium polyphosphate (AMP) microencapsulation technology plays a key role in this process, ensuring uniform release of the flame retardant at high temperatures, preventing premature release and thus optimizing the flame retardant effect over time. Microencapsulation effectively controls the interaction of AMP with the matrix material during the melting process, preventing negative impacts on the material's fluidity and stability. Furthermore, microencapsulation enables AMP to stably release its flame retardant at high temperatures during the molding process without causing adhesion or uneven flow, further improving post-molding precision and surface quality.

[0084] In contrast, removing or reducing the modified expanded graphite and ultrasonic dispersion step can cause the processing properties of composite material to decline. Especially after removing ultrasonic dispersion, nano-scale magnesium hydroxide and graphite fail to fully disperse, causing the material to flow unevenly during extrusion. Removing modified expanded graphite reduces the expansion layer in the composite material, affects the internal dispersibility and structural stability of the material, thereby causing larger external diameter and thickness deviation to occur in the molding process, and surface smoothness reduces. These factors act together, causing the processing stability of the material to decline, and it is impossible to reach the excellent performance of Example 1.

[0085] The examples of this specific embodiment are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, any equivalent changes made based on the structure, shape, and principle of this application should be included in the scope of protection of this application.

Claims

1. A B1 flame-retardant butterfly optical cable, comprising a flame-retardant sheath, optical fiber and glass yarn, characterized in that: The flame retardant sheath is composed of the following components in parts by weight: Modified low-density polyethylene: 40-45 parts; Nano-magnesium hydroxide: 25-30 parts; Ammonium polyphosphate: 10-12 parts; Modified expanded graphite: 5-7 parts; Silicone modified melamine: 3-4 parts; Zinc-boron synergist: 2-3 parts; Maleic anhydride grafted polyethylene: 2-3 parts; Antioxidant: 1-2 parts; Lubricant: 1-2 parts.

2. A B1 flame-retardant butterfly optical cable according to claim 1, characterized in that: The particle size of the nano-magnesium hydroxide is 50-100 nm, and a KH-550 silane coupling agent is grafted on the surface. The addition amount of the KH-550 silane coupling agent is 2.5-4.0% of the weight of the nano-magnesium hydroxide.

3. The B1 flame-retardant butterfly optical cable according to claim 1, characterized in that: The ammonium polyphosphate is a microcapsule structure, the microcapsule wall material is a polyurethane-siloxane copolymer, the microcapsule wall material accounts for 10-15% of the total weight of the microcapsule, and the average particle size of the microcapsule is 20-30 μm.

4. The B1 flame-retardant butterfly optical cable according to claim 1, characterized in that: The weight ratio of the organosilicon-modified melamine to the zinc-boron synergist is 1.0-1.5:0.6-0.

8. The zinc-boron synergist consists of zinc oxide and borate. The weight ratio of the zinc oxide to the borate is 1.0-1.2:1.5-2.

0.

5. The B1 flame-retardant butterfly optical cable according to claim 1, characterized in that: The outer layer thickness of the flame retardant sheath is 0.4-0.6 mm, and the overall diameter is 3.0±0.1 mm.

6. A process for preparing a B1-class flame-retardant butterfly optical cable, for preparing a B1-class flame-retardant butterfly optical cable according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Surface-modifying nano-magnesium hydroxide and microencapsulating ammonium polyphosphate, and ultrasonically dispersing the modified nano-magnesium hydroxide to form a uniform dispersion; S2. Mixing the formed uniform dispersion with modified low-density polyethylene, and then sequentially adding organosilicon-modified melamine and zinc-boron synergist, and forming the mixture by multi-zone temperature-controlled extrusion to obtain flame-retardant composite material particles; S3, placing the optical fiber in a loose tube and filling it with fluorosilicone gel, arranging a glass fiber yarn reinforcement, and extruding the prepared flame retardant composite material particles through a butterfly die; S4. Use gradient cooling to shape and make B1-level flame-retardant butterfly-shaped optical cables, and perform flame-retardant and mechanical property tests on the prepared B1-level flame-retardant butterfly-shaped optical cables.

7. The process for preparing a B1-class flame-retardant butterfly optical cable according to claim 6, characterized in that: In step S1, the surface modification of nano-magnesium hydroxide and microencapsulation of ammonium polyphosphate include the following steps: Disperse nano-magnesium hydroxide in ethanol, add 0.8-1.2 parts by weight of KH-550 silane coupling agent, stir and react at 60-70°C for 2-3 hours, filter, wash and dry to obtain surface-modified nano-magnesium hydroxide; Adopt interfacial polymerization method, use polyurethane-siloxane copolymer as wall material, control reaction temperature at 40-50℃, reaction time 4-6 hours, obtain microencapsulated ammonium polyphosphate, microcapsule wall material accounts for 10-15% of the total weight; The surface-modified nano-magnesium hydroxide and the modified expanded graphite are mixed in a weight ratio of 3:1-5:1, and dispersed for 15-20 minutes at an ultrasonic frequency of 20-25 kHz to form a uniform dispersion.

8. The process for preparing a B1-class flame-retardant butterfly optical cable according to claim 6, characterized in that: In step S2, the preparation of flame-retardant composite material particles comprises the following steps: Adopt gradient temperature control multi-zone mixing technology, set 6 temperature intervals, the temperatures are 160-165℃, 165-170℃, 170-175℃, 175-180℃, 170-175℃, 165-170℃; Adding organosilicon-modified melamine and zinc-boron synergist in the third temperature zone, with the weight ratio of organosilicon-modified melamine to zinc-boron synergist being 1.0-1.5:0.6-0.8, adding maleic anhydride-grafted polyethylene in the fourth temperature zone, and adding antioxidant and lubricant in the fifth temperature zone; Pulse extrusion technology is used, the pulse frequency is set to 0.7-0.9Hz, the screw speed is controlled to 40-50rpm, the material residence time is controlled to 2-3 minutes, and the flame retardant composite material particles are obtained after underwater pelletizing and vacuum drying for 4-6 hours.

9. The process for preparing a B1-class flame-retardant butterfly optical cable according to claim 6, characterized in that: In step S3, the extrusion molding of the prepared flame-retardant composite material particles through a butterfly die comprises the following steps: Place the single-mode optical fiber in a loose tube, inject fluorosilicone gel filler, seal it, and arrange the glass fiber yarns parallel and symmetrically on both sides of the loose tube. Use a positioning device to ensure the accurate position of the glass fiber yarns. Add the flame retardant composite material particles into the extruder, control the extrusion temperature at 175-185℃, use a specially designed butterfly die for extrusion, and control the extrusion speed at 5-8m / min.

10. The process for preparing a B1-class flame-retardant butterfly optical cable according to claim 6, characterized in that: In step S4, the flame retardant performance and mechanical property testing of the prepared B1-level flame retardant butterfly optical cable includes the following steps: Flame retardant performance test: Cut B1 flame-retardant butterfly optical cable samples into specimens with a length of 100-120mm and a width of 6.5±0.5mm. Test them in an oxygen index meter at a controlled temperature of 23±2°C, a relative humidity of 50±5%, and an ignition time of 30-180 seconds to determine the minimum oxygen concentration at which the sample can sustain combustion in an oxygen / nitrogen mixture. Mechanical properties test: The optical cable samples were pre-treated in a constant temperature and humidity environment for 24 hours, and the tensile strength test was performed on a universal material testing machine with a loading rate of 50-100 mm / min and a test sample length of 500±10 mm.

Images