Tensile compression-resistant flame-retardant optical cable

Abstract

The invention relates to the technical field of communication optical cable manufacturing, in particular to a tensile compression-resistant flame-retardant optical cable. The problems that a traditional optical cable is poor in tensile and compression resistance and poor in flame retardant property are solved. The PBO fibers and the aramid fibers are subjected to plain mixed weaving by adopting proper weaving parameters, so that the PBO fibers and the aramid fibers are complementary in mechanical property; the stainless steel pipe sleeve is used as the first armor layer to increase the overall strength of the optical cable; melting and blending the polymer, magnesium hydroxide and polycarbosilane to prepare an inner sheath of the optical cable, and performing ceramization at high temperature to form a hard framework; polypropylene is combined with a modified flame-retardant material to prepare a flame-retardant outer sheath which is decomposed and absorbs heat in case of fire, so that the flame temperature is reduced; the mechanical properties of the optical cable are improved through the combined action of multiple components, and the tensile, compression-resistant and flame-retardant properties of the optical cable are cooperatively improved.

Description

Technical Field

[0001] This invention relates to the field of optical cable manufacturing technology, specifically to a tensile, compressive, and flame-retardant optical cable. Background Technology

[0002] Optical fiber cables are widely used in the communications field, especially for long-distance, high-bandwidth data transmission. They are a crucial component of infrastructure such as the internet, telephone communications, and television broadcasting, offering higher data transmission speeds and longer distances than traditional cables, and are less susceptible to electromagnetic interference. For example, in industries such as subways, railways, and energy, optical fiber cables are used to transmit critical data and control signals.

[0003] However, current fiber optic cable products on the market have revealed numerous problems in practical applications. Firstly, the design and manufacturing process of fiber optic cables has failed to adequately consider the importance of flame-retardant properties, resulting in their inability to effectively suppress the spread of fire when exposed to extreme environments such as high temperatures or open flames, thus increasing the risk of fire. Over time and with increased use, this deficiency may gradually become apparent, potentially leading to spontaneous combustion of the fiber optic cable due to excessively high temperatures during operation. In severe cases, this could even cause a fire, posing a significant safety hazard to the communication network on which the cable resides.

[0004] Secondly, the physical structure of optical cables also requires proper design. Due to technological limitations or insufficient quality control during the production process, internal structural damage may occur after a period of use. If these minor damages are not detected and repaired promptly, they will become more severe over time, significantly shortening the cable's lifespan. Furthermore, when used outdoors, optical cables are frequently subjected to harsh weather conditions such as wind, sun, rain, snow, and ice, making them susceptible to mechanical damage, such as being broken by wind or twisted and deformed by being dragged by trees, buildings, or other objects. These external factors directly affect the stability and reliability of the optical cable, thus negatively impacting its lifespan.

[0005] In view of the shortcomings of existing optical cables, such as poor tensile and compressive strength and poor flame retardant performance, there is an urgent need to develop a tensile, compressive and flame retardant optical cable. Summary of the Invention

[0006] The purpose of this invention is to provide a tensile, compressive, and flame-retardant optical cable. This is achieved by plain-weaving PBO fibers and aramid fibers using appropriate weaving parameters, resulting in complementary mechanical properties. A stainless steel tubing is used as the first armor layer to increase the overall strength of the optical cable. An inner sheath is prepared by melt-blending a polymer with magnesium hydroxide and polycarbosilane, which is then ceramicized at high temperatures to form a rigid skeleton. A flame-retardant outer sheath is prepared by combining polypropylene with modified flame-retardant materials, which decomposes and absorbs heat during a fire, reducing the flame temperature. These multiple components work together to improve the mechanical properties of the optical cable while synergistically enhancing its tensile, compressive, and flame-retardant performance.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a tensile and compressive resistant flame-retardant optical cable. The structure of the tensile and compressive resistant flame-retardant optical cable includes, from the inside out, a cable core, a fiber reinforcement layer, a first armor layer, an inner sheath, and a flame-retardant outer sheath. The fiber reinforcement layer of the tensile and compressive resistant flame-retardant optical cable includes poly(p-phenylene benzodioxazole) fiber, aramid fiber, and silicone oil lubricant; The inner sheath of the tensile and compressive resistant flame-retardant optical cable includes polyethylene, ethylene-vinyl acetate copolymer, magnesium hydroxide, and polycarbosilane; The flame-retardant outer sheath of the tensile and compressive flame-retardant optical cable includes modified hydroxide, modified nano boron oxide, and polypropylene; The flame-retardant outer sheath of the flame-retardant optical cable with tensile and compressive strength is modified with hydroxide by stirring and drying a solution of dried magnesium hydroxide, dried aluminum hydroxide and silane coupling agent. The flame-retardant outer sheath of the tensile and compressive flame-retardant optical cable is modified with nano-boron oxide, which is obtained by ultrasonically dispersing modified multi-walled carbon nanotubes and nano-boron oxide in DMF solution, followed by filtration and drying.

[0008] Preferably, the cable core contains 24 optical fibers.

[0009] Preferably, the fiber reinforcement layer preparation steps of the tensile, compressive and flame-retardant optical cable are as follows: using a circular loom to plain weave poly(p-phenylene benzodioxazole) fibers and aramid fibers, adding 0.8 parts of silicone oil lubricant during the weaving process, the weaving speed of the circular loom is 30-35 r / min, and the weaving tension is controlled between 17-20 N; the ratio of the number of poly(p-phenylene benzodioxazole) fibers to aramid fibers is 4:12; wherein, the total amount of fibers used in the fiber reinforcement layer is 16 fibers.

[0010] Preferably, the first armor layer of the tensile and compressive flame-retardant optical cable uses a stainless steel sheath as the three-layer coating material to protect the fiber reinforcement layer of the tensile and compressive flame-retardant optical cable.

[0011] Preferably, a layer of low-smoke halogen-free ceramicized polyolefin material is extruded outside the first armor layer of the tensile-resistant, compressive-resistant, and flame-retardant optical cable as the inner sheath of the cable. The preparation steps for the low-smoke halogen-free ceramicized polyolefin material in the inner sheath of the tensile, compressive and flame-retardant optical cable are as follows: polyethylene, ethylene-vinyl acetate copolymer, magnesium hydroxide and 15 parts of polycarbosilane are melt-mixed in a torque rheometer at 130-140℃ for 10 minutes to obtain mixture A. Mixture A is then pressed into low-smoke halogen-free ceramicized polyolefin material using a flat vulcanizing machine.

[0012] Preferably, the preparation steps for the flame-retardant outer sheath of the tensile and compressive flame-retardant optical cable are as follows: modified hydroxide, modified nano boron oxide and polypropylene are placed in a plasticizer in a mass ratio of 2:0.5-0.7:5-6 for melt blending. The melt blending temperature is 170-180℃ and the time is 3h to obtain the flame-retardant outer sheath.

[0013] Preferably, the preparation steps of the modified hydroxide in the flame-retardant outer sheath of the tensile and compressive flame-retardant optical cable are as follows: 20 parts of magnesium hydroxide and 20 parts of aluminum hydroxide are placed in a 120℃ constant temperature drying oven and dried for 3 hours to obtain dried magnesium hydroxide and dried aluminum hydroxide; the dried magnesium hydroxide and dried aluminum hydroxide are placed in a 100℃ water bath, and 0.25-0.28 parts of KH-560 silane coupling agent solution diluted with 8 parts of anhydrous ethanol are slowly added dropwise while stirring slowly; after the addition is completed, the water bath speed is adjusted to 600-650 r / min, stirred for 30 min, and then placed in a 120℃ constant temperature drying oven for 3 hours to obtain the modified hydroxide (MOH).

[0014] Preferably, the preparation steps of modified nano-boron oxide in the flame-retardant outer sheath of the tensile and compressive flame-retardant optical cable are as follows: 20 parts of multi-walled carbon nanotubes are placed in a three-necked round-bottom flask, 10 parts of dilute HNO3 solution and 1.0-1.5 parts of sodium dodecyl sulfate aqueous solution are added, and functionalization treatment is carried out at 100℃ for 30 min. Then, the mixture is filtered, washed, and dried to obtain preliminarily modified multi-walled carbon nanotubes. The preliminarily modified multi-walled carbon nanotubes are placed in a beaker, 5 parts of 1wt% sodium dodecyl sulfate aqueous solution are added, and ultrasonic dispersion is carried out for 1 h to obtain modified multi-walled carbon nanotubes. 15 parts of nano-boron oxide are placed in a beaker, 12 parts of modified multi-walled carbon nanotubes and 20 parts of DMF solution are added, and ultrasonic dispersion is carried out for 1 h. After filtration and drying, modified nano-boron oxide is obtained.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Poly(p-phenylene benzodioxazole) fiber has high tensile strength and safe operating temperature, while aramid fiber has high compressive strength and high temperature resistance. The two fibers are used in a plain weave mixture, which not only complements each other in mechanical properties but also increases the contact area between fibers and improves the bonding force between fibers. This makes the optical cable less prone to deformation and cracking under tension, thereby enhancing the tensile and compressive strength of the optical cable. The mixed weave of the two fibers further improves the stability of the optical cable in high-temperature environments, making the optical cable less flammable in high-temperature environments and improving its flame retardant properties to a certain extent.

[0016] 2. A plain weave combination of poly(p-phenylene benzodioxazole) fiber and aramid fiber, along with a stainless steel sheath as the first armor layer, allows the two fibers to form a dense char layer during combustion. This char layer covers the surface of the optical cable, isolating oxygen and preventing heat transfer, thus inhibiting combustion. The plain weave of the two fibers complements each other in mechanical properties, making the cable less prone to deformation and cracking under tension, thereby enhancing its tensile and compressive strength. The stainless steel sheath, as the first armor layer, possesses high rigidity and strength, providing strong support and protection for the optical cable. It evenly distributes external pressure across the entire cable surface, effectively protecting the internal optical fibers. Furthermore, the stainless steel sheath is a non-combustible material, remaining stable even under direct impact from high-temperature flames, providing an effective fire barrier for the optical fibers.

[0017] 3. The inherent thermal stability of polypropylene material, combined with the flame-retardant outer sheath formed by the melt blending of modified hydroxides and modified nano-boron oxide, provides sufficient mechanical support for the optical cable, resulting in concentrated stress distribution and excellent tensile and compressive strength under tension and pressure. In the event of a fire, it can decompose and absorb heat, reducing the flame temperature and isolating oxygen and heat, thereby reducing damage and the degree of burning of the optical cable, improving the pass rate of the optical cable in Class A bundled burning and Class B bundled burning tests, and ensuring that the optical cable has good flame-retardant performance in actual fire scenarios.

[0018] 4. Polyethylene has high crystallinity and rigidity, while ethylene-vinyl acetate copolymer has good flexibility and elasticity. When mixed, the ethylene-vinyl acetate copolymer can fill the spaces between polyethylene molecular chains, absorbing and dispersing energy through elastic deformation, thus reducing stress concentration. Magnesium hydroxide, as an inorganic filler, fills the polymer matrix formed by polyethylene and ethylene-vinyl acetate copolymer, restricting the movement of polymer molecular chains. Under stress, magnesium hydroxide binds tightly to the polymer matrix, dispersing stress over a wider area. The inner sheath material has a uniform internal structure, reducing scattering and refraction during stress transmission. The synergistic addition of polycarbosilane further enhances the inner sheath's... At high temperatures, ceramization forms a rigid skeleton, providing additional support during the stretching and compression of the optical cable, thus improving the overall tensile and compressive strength and the stability of light transmission performance. Simultaneously, the temperature and mixing conditions provided by the torque rheometer ensure the uniform distribution of polyethylene, ethylene-vinyl acetate copolymer, magnesium hydroxide, and polycarbosilane. The uniformly distributed magnesium hydroxide and polycarbosilane work synergistically during combustion; magnesium hydroxide acts first to suppress initial combustion and lower the temperature, buying time for the ceramization reaction of polycarbosilane. The ceramic layer formed by polycarbosilane further prevents the transfer of flame and heat, enhancing the overall flame-retardant effect of the optical cable. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view of the tensile, compressive, and flame-retardant optical cable of the present invention.

[0020] In the diagram: 1. Cable core; 2. Fiber reinforcement layer; 3. First armor layer; 4. Inner sheath; 5. Flame-retardant outer sheath. Detailed Implementation

[0021] 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.

[0022] Please see Figure 1 This invention provides a tensile and compressive resistant flame-retardant optical cable, the technical solution of which is as follows: Figure 1 This is a cross-sectional view of a tensile, compressive, and flame-retardant optical cable. The structure of the tensile, compressive, and flame-retardant optical cable, from the inside out, includes a cable core 1, a fiber reinforcement layer 2, a first armor layer 3, an inner sheath 4, and a flame-retardant outer sheath 5.

[0023] The material information involved in this invention is as follows: Polyethylene (PE), model LDPE2426H, CNOOC Shell; Ethylene-vinyl acetate copolymer (EVA), CAS: 24937-78-8; Magnesium hydroxide (MH), model MH5-C, purchased from Dandong Songyuan Chemicals Co., Ltd.; Polycarbosilane (PCS), number average molecular weight 1356; Poly(p-phenylenebenzodioxazole) fiber (PBO), purchased from Chengdu Xinchen New Material Technology Co., Ltd.; Aramid fiber, CAS: 308069-56-9; Circular loom for aramid products (CN219269362U), purchased from Nantong Beijia Machinery Technology Co., Ltd.; Polypropylene (PP), CAS: 9003-07-0; Aluminum hydroxide (ATH), CAS: 21645-51-2; KH-560 (γ-glycidyl etheroxypropyltrimethoxysilane) CAS: 2530-83-8; Multi-walled carbon nanotubes CAS: 308068-56-6, purchased from Merck; Sodium dodecyl sulfate (SDS) CAS: 151-21-3; Nano boron oxide (n-B2O3) purchased from Zhejiang Yamei Nanotechnology Co., Ltd.; Torque rheometer purchased from Harbin Hap Electric Technology Co., Ltd. Example

[0024] The cable core contains 24 optical fibers; The fiber reinforcement layer is prepared by: using a circular loom to plain weave poly(p-phenylene benzodioxazole) fibers and aramid fibers, adding 0.8 parts of silicone oil lubricant during the weaving process, the weaving speed of the circular loom is 31 r / min, and the weaving tension is 20 N; the ratio of the number of poly(p-phenylene benzodioxazole) fibers to aramid fibers is 4:12; and the total amount of fibers used in the fiber reinforcement layer is 16 fibers.

[0025] The first armor layer uses a stainless steel sleeve as the three-layer coating material to protect the fiber reinforcement layer.

[0026] A layer of low-smoke halogen-free ceramicized polyolefin material is extruded outside the first armor layer as the inner sheath of the optical cable. The preparation steps of low-smoke halogen-free ceramicized polyolefin material are as follows: polyethylene, ethylene-vinyl acetate copolymer, magnesium hydroxide and 15 parts of polycarbosilane are melt-mixed in a torque rheometer at 138℃ for 10 min to obtain mixture A. Mixture A is then pressed into low-smoke halogen-free ceramicized polyolefin material using a flat vulcanizing machine.

[0027] The modified hydroxide preparation steps are as follows: 20 parts of magnesium hydroxide and 20 parts of aluminum hydroxide are placed in a 120℃ constant temperature drying oven and dried for 3 hours to obtain dried magnesium hydroxide and dried aluminum hydroxide; the dried magnesium hydroxide and dried aluminum hydroxide are placed in a 100℃ water bath, and 0.25 parts of KH-560 silane coupling agent solution diluted with 8 parts of anhydrous ethanol are slowly added dropwise while stirring slowly; after the addition is completed, the water bath speed is adjusted to 650 r / min, and after stirring for 30 min, it is placed in a 120℃ constant temperature drying oven and dried for 3 hours to obtain the modified hydroxide.

[0028] The modified boron oxide nanoparticles were prepared as follows: 20 parts of multi-walled carbon nanotubes were placed in a three-necked round-bottom flask, 10 parts of dilute HNO3 solution and 1.0 part of 1wt% sodium dodecyl sulfate aqueous solution were added, and the mixture was functionalized at 100℃ for 30 min. Then, the mixture was filtered, washed, and dried to obtain pre-modified multi-walled carbon nanotubes. The pre-modified multi-walled carbon nanotubes were placed in a beaker, 5 parts of 1wt% sodium dodecyl sulfate aqueous solution were added, and the mixture was ultrasonically dispersed for 1 h to obtain modified multi-walled carbon nanotubes. 15 parts of boron oxide nanoparticles were placed in a beaker, 12 parts of modified multi-walled carbon nanotubes and 20 parts of DMF solution were added, and the mixture was ultrasonically dispersed for 1 h. After filtration and drying, the modified boron oxide nanoparticles were obtained.

[0029] The preparation steps of the flame-retardant outer sheath are as follows: Modified hydroxide, modified nano boron oxide and polypropylene are placed in a plasticizer in a mass ratio of 2:0.5:6 and melt-blended at a temperature of 170℃ for 3 hours to obtain the flame-retardant outer sheath.

[0030] Examples 2-7 Compared to Example 1, the parameters have been adjusted, which are summarized in Table 1; in Table 1, the weaving speed and weaving tension are the weaving speed and weaving tension of the circular loom; temperature 1 is the melting temperature of the torque rheometer.

[0031] Table 1. Adjustment of preparation parameters in Examples 1-7

[0032] Examples 8-14 The process flow and preparation method are the same as in Example 1, but some parameters have been changed, which are summarized in Table 2. In Table 2, temperature 2 is the melting and blending temperature of the plasticizer; and rotation speed is the rotation speed of the water bath.

[0033] Table 2. Adjustment of preparation parameters in Examples 8-14

[0034] To verify the necessity of some technical solutions in achieving the technical effects of this invention, some comparative examples of this invention will be shown and described below.

[0035] Comparative Example 1 Unlike Example 1, all 16 fibers in the fiber reinforcement layer are poly(p-phenylenebenzodioxazole) fiber (PBO), and the weaving speed of the circular loom is 45 r / min, the weaving tension is set to 22 N, and other process parameters are the same.

[0036] Comparative Example 2 Unlike Example 1, all 16 fibers in the fiber reinforcement layer are made of aromatic polyamide nanofibers, while other process parameters are the same.

[0037] Comparative Example 3 Unlike Example 8, the stainless steel sleeve of the first armor layer is replaced with mica tape, while all other process parameters remain the same.

[0038] Comparative Example 4 Unlike Example 10, polypropylene (PP) was replaced with polyvinyl chloride (PVC) in the step of preparing the flame-retardant protective sleeve; and sodium dodecyl sulfate (SDS) aqueous solution was not added when preparing the modified nano boron oxide, while other process parameters remained the same.

[0039] Comparative Example 5 The difference from Example 10 is that the amount of polyethylene (PE) added to the low-smoke halogen-free ceramicized polyolefin material was adjusted to 50 parts, and the torque rheometer was replaced with a two-roll mill, while other process parameters remained the same.

[0040] Experimental Example 1 The tensile strength and tensile load of the optical cable were tested using a universal testing machine with a sensor range of 5 kN. The test length of the optical cable was 500 mm, the outer diameter was (2.4 ± 0.2) mm, the tensile rate was 20 mm / min, and the load time was 1 min. The specific test results are shown in Table 3.

[0041] Table 3 Tensile strength test results of optical cables prepared in Examples 1-7 and Comparative Example 1

[0042] Table 3 shows the tensile properties of the optical cables prepared in Examples 1-7 and Comparative Example 1. The test results show that the tensile strength of the optical cables prepared in Examples 1-7 is all higher than 3230 N, and the tensile load is all higher than 2860 N. In Comparative Example 1, unlike Examples 1-7, all 16 fibers in the fiber reinforcement layer were poly(p-phenylene benzodioxazole) fibers, and the circular loom's weaving speed was 45 r / min with a weaving tension of 22 N. Although poly(p-phenylene benzodioxazole) fibers have high tensile strength and tensile load, using them alone can easily lead to increased strength differences in different directions of the optical cable. Furthermore, excessive weaving speed increases the tension on the poly(p-phenylene benzodioxazole) fibers during weaving, resulting in a relatively dispersed arrangement and interlacing structure within the fibers, making the overall structure of the optical cable less compact. Under high weaving tension, the poly(p-phenylene benzodioxazole) fibers are overstretched, weakening the inter-fiber forces and causing microcracks during testing. These microcracks reduce the tensile strength and tensile load of the optical cable. Moreover, aramid fibers themselves have good flame-retardant properties; the synergistic weaving of these two fibers improves the overall flame-retardant performance of the optical cable. In summary, poly(p-phenylene benzodioxazole) fiber has high tensile strength and safe operating temperature, while aramid fiber has high compressive strength and high temperature resistance. The two fibers are used in plain weave, which not only complements each other in terms of mechanical properties, but also increases the contact area between fibers and improves the bonding force between fibers. This makes the optical cable less prone to deformation and cracking when subjected to tension, thereby enhancing the tensile and compressive strength of the optical cable.

[0043] Experiment Example 2 The compressive strength and compressive load of the optical cable were tested using a universal testing machine with a sensor range of 5 kN. The test length of the optical cable was 500 mm, the outer diameter was (2.4 ± 0.2) mm, and the load time was 3 min. The specific test results are shown in Table 4.

[0044] Table 4. Compression resistance test results of optical cables prepared in Examples 8-14 and Comparative Examples 2-3

[0045] Table 4 shows the data for testing the compressive strength of the optical cables prepared in Examples 8-14 and Comparative Example 2. The test results show that the compressive strength of the optical cables prepared in Examples 8-14 is higher than 5335 N, and the compressive load is higher than 4310 N. However, Comparative Example 2 differs from Examples 8-14 in that all 16 fibers in the fiber reinforcement layer are made of aromatic polyamide nanofibers. Although aromatic polyamide nanofibers have good environmental stability and certain mechanical properties, their crush resistance is three to five times that of aramid fibers. This means that when using aromatic polyamide nanofibers as the fiber reinforcement layer material for optical cables, internal structural damage can occur under relatively low external pressure, leading to performance degradation or even failure of the optical cable after only a few cycles of compressive load. Meanwhile, aromatic polyamide nanofibers, due to their poor molecular chain regularity and low crystallinity, exhibit relatively poor thermal stability and a low thermal decomposition temperature. When aromatic polyamide nanofiber optical cables encounter high-temperature environments, they begin to decompose more quickly, their structure is damaged, and they cannot effectively prevent heat transfer and flame spread, making the optical cables more susceptible to flame penetration and burning. Comparative Example 3 differs from Examples 8-14 in that the stainless steel sheath of the first armor layer is replaced with mica tape. The rigidity and hardness of the optical cable prepared from mica tape are inferior to those from the stainless steel sheath. When the mica tape optical cable is subjected to compression and impact, the supporting force and elastic modulus provided by the mica tape optical cable are insufficient, making it more prone to creep. This causes the impact force to be directly transmitted to the interior of the mica tape optical cable, causing it to lose its ability to resist pressure and significantly reducing its compressive load capacity. Meanwhile, when a mica-ribbon optical cable encounters a fire, after the outer flame-retardant outer sheath is completely burned away, its inner first armor layer is mainly composed of mica tape. Under high temperature, the mica tape will form a fish-scale structure and become completely carbonized. The collapse of the optical cable skeleton causes stress to act directly on the internal optical fiber, eventually leading to optical fiber breakage and signal interruption. In summary, the use of a plain weave hybrid of poly(p-phenylene benzodioxazole) fiber and aramid fiber, along with a stainless steel sheath as the first armor layer, allows the two fibers to form a dense char layer during combustion. This char layer covers the surface of the optical cable, isolating oxygen and preventing heat transfer, thus inhibiting combustion. The plain weave of the two fibers complements each other in mechanical properties, making the cable less prone to deformation and cracking under tension, thereby enhancing its tensile and compressive strength. The stainless steel sheath, as the first armor layer, possesses high rigidity and strength, providing strong support and protection for the optical cable, evenly distributing external pressure across the entire cable surface, effectively protecting the internal optical fibers. Furthermore, the stainless steel sheath is a non-combustible material, remaining stable even under direct impact from high-temperature flames, providing an effective fire barrier for the optical fibers.

[0046] Experimental Example 3 Example 10 and Comparative Example 4 were selected for fire resistance performance testing of optical cables. To reduce the influence of the environment on the test error, the experimental environment temperature was 22-24℃ and the humidity was 40%-50%. The specific test results are shown in Table 5.

[0047] Table 5 Fire resistance test results of optical cables prepared in Example 10 and Comparative Example 4 Table 5 shows the fire resistance of the optical cables prepared in Example 10 and Comparative Example 4. The test results show that the optical cable prepared in Example 10 passed both the Class A and Class B bundled burning tests. However, Comparative Example 4 differs from Example 10 in that polypropylene was replaced with polyvinyl chloride in the preparation of the flame-retardant protective sleeve; and sodium dodecyl sulfate aqueous solution was not added during the preparation of the modified nano-boron oxide. Consequently, the fire resistance and mechanical properties of the resulting optical cable decreased significantly. First, replacing polypropylene with polyvinyl chloride (PVC) is problematic because PVC has lower thermal stability than polypropylene and decomposes more easily at high temperatures. In the event of a fire, PVC will decompose prematurely, damaging the flame-retardant outer sheath structure and failing to provide effective protection for the internal fiber optic cable. Second, the decomposition of PVC at high temperatures produces burning droplets and releases harmful gases such as hydrogen chloride. These droplets increase the risk of igniting surrounding objects, and the large amount of gas produced will form a gas layer around the fiber optic cable, hindering heat dissipation and causing the internal temperature to rise more rapidly. Third, because the modified nano-boron oxide process in the flame-retardant protective sheath does not include the surfactant sodium dodecyl sulfate aqueous solution, the multi-walled carbon nanotubes and nano-boron oxide are prone to agglomeration. After the formation of modified nano-boron oxide, this uneven structure leads to further agglomeration when mixed with modified hydroxide, failing to fully utilize the advantages of the flame-retardant protective sheath and thus reducing the overall thermal stability and high-temperature resistance of the fiber optic cable. Replacing polypropylene with polyvinyl chloride (PVC) in the flame-retardant protective sleeve preparation process, and omitting sodium dodecyl sulfate aqueous solution during the preparation of modified nano-boron oxide, will negatively impact the tensile and compressive strength of the optical cable. Firstly, PVC has weaker flexibility and impact resistance compared to polypropylene. Secondly, the absence of sodium dodecyl sulfate aqueous solution during the modified nano-boron oxide preparation process makes it easier for multi-walled carbon nanotubes and nano-boron oxide to aggregate. When the optical cable is subjected to tension and pressure, these stress areas will become weak points, and stress will preferentially concentrate in these areas, thus reducing the tensile and compressive strength of the optical cable. In summary, the inherent thermal stability of polypropylene, combined with the flame-retardant outer sheath formed by the melt blending of modified hydroxides and modified nano-boron oxide, provides sufficient mechanical support for the optical cable, resulting in concentrated stress distribution and excellent tensile and compressive strength under tension and pressure. In the event of a fire, it can decompose and absorb heat, reducing the flame temperature and isolating oxygen and heat, thereby reducing damage and the extent of burning of the optical cable. This improves the pass rate of the optical cable in Class A and Class B bundled burning tests, ensuring that the optical cable has good flame-retardant performance in actual fire scenarios.

[0048] Experiment Example 4 Example 10 and Comparative Example 5 were selected for fire resistance performance testing of optical cables. Optical fiber is more sensitive to optical performance at a wavelength of 1550nm than at 1310nm, so 1550nm was selected as the detection wavelength for light transmission performance in the experiment. Test items: tensile load condition: load of 3000N, load time of 1min; compressive load condition: 4330N / 100mm, load time of 3min; impact condition: 30 impacts, drop weight of 3kg, drop height of 150mm; specific test results are shown in Table 6.

[0049] Table 6. Tensile and compressive strength and fire resistance tests of the optical cables prepared in Example 10 and Comparative Example 5.

[0050] Table 6 shows the comprehensive testing of the tensile, compressive, and fire-resistant properties of the optical cables prepared in Example 10 and Comparative Example 5. The test results show that the flame-retardant outer sheath of the optical cable prepared in Example 10 did not crack under experimental tensile load, compressive load, and impact, and the change in light transmission performance was less than 0.2 dB. However, Comparative Example 5 differs from Example 10 in that the amount of polyethylene added to the low-smoke halogen-free ceramicized polyolefin material was adjusted to 50 parts during the preparation of the inner sheath, and the torque rheometer was replaced with a two-roll mill. This significantly reduced the fire resistance and mechanical properties of the resulting optical cable. First, increasing the amount of polyethylene added leads to phase separation and uneven crystallization within the material, creating optical scattering centers that scatter and refract light during propagation, thus reducing the optical cable's light transmission performance. Second, the operation of the open mill is relatively crude, relying solely on the relative rotation of two rollers to shear and mix the modified material. Its mixing precision and controllability are far lower than those of a torque rheometer. Inaccurate temperature and speed control can cause localized overheating during processing, and uneven mixing directly reduces the overall flexibility and strength of the optical cable, lowering its tensile and compressive strength. Simultaneously, magnesium hydroxide, affected by the single shearing force of the open mill, cannot fully utilize its flame-retardant properties.

[0051] In summary, polyethylene has high crystallinity and rigidity, while ethylene-vinyl acetate copolymer (EVA) has good flexibility and elasticity. When mixed, the EVA can fill the spaces between polyethylene molecular chains, absorbing and dispersing energy through elastic deformation, thus reducing stress concentration. Magnesium hydroxide, as an inorganic filler, fills the polymer matrix formed by polyethylene and EVA, restricting the movement of polymer molecular chains. Under stress, magnesium hydroxide binds tightly to the polymer matrix, dispersing stress over a wider area. The inner sheath material has a uniform internal structure, reducing scattering and refraction of light. The synergistic addition of polycarbosilane further enhances the inner sheath material's uniformity. The sheath forms a rigid skeleton at high temperatures, providing additional support during the stretching and compression of the optical cable, thus improving the overall tensile and compressive strength and light transmission stability of the cable. Simultaneously, the temperature and mixing conditions provided by the torque rheometer ensure the uniform distribution of polyethylene, ethylene-vinyl acetate copolymer, magnesium hydroxide, and polycarbosilane. The uniformly distributed magnesium hydroxide and polycarbosilane work synergistically during combustion; magnesium hydroxide acts first to suppress initial combustion and lower the temperature, allowing time for the ceramization reaction of polycarbosilane. The ceramic layer formed by polycarbosilane further prevents the transfer of flame and heat, enhancing the overall flame-retardant effect of the optical cable.

[0052] 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 tensile, compression, and flame resistant optical cable, characterized by, The structure of the tensile and compressive resistance flame-retardant optical cable comprises, from inside to outside, a cable core (1), a fiber reinforced layer (2), a first armored layer (3), an inner sheath (4), and a flame-retardant outer sheath (5); the fiber reinforced layer (2) comprises poly-p-phenylene benzobisoxazole fiber, aramid fiber, and silicone oil lubricant; the inner sheath (4) comprises polyethylene, ethylene-vinyl acetate copolymer, magnesium hydroxide, and polycarbosilane; the flame-retardant outer sheath (5) comprises modified hydroxide, modified nano boron oxide, and polypropylene; the modified hydroxide is obtained by stirring and drying treatment of dry magnesium hydroxide, dry aluminum hydroxide, and silane coupling agent solution; The modified nano boron oxide is obtained by ultrasonic dispersion of modified multi-walled carbon nanotubes and nano boron oxide in DMF solution, filtration, and drying. The modified multi-walled carbon nanotubes are obtained by functionalization treatment of multi-walled carbon nanotubes with nitric acid solution and sodium dodecyl sulfate.

2. A tensile and compressive flame resistant optical cable according to claim 1, wherein, The cable core (1) of the tensile and compressive resistance flame-retardant optical cable contains 24 optical fibers.

3. A tensile and compressive flame resistant optical fiber cable according to claim 1, wherein: The preparation steps of the fiber reinforced layer (2) are as follows: using a circular weaving machine to mix and weave the poly-p-phenylene benzobisoxazole fiber and the aramid fiber in plain weave, adding the silicone oil lubricant, and controlling the weaving speed of the circular weaving machine at 30-35 r / min and the weaving tension at 17-20 N.

4. A tensile and compressive flame resistant optical fiber cable according to claim 1, wherein, The first armored layer (3) of the tensile and compressive resistance flame-retardant optical cable uses a stainless steel sleeve as a three-layer coating material to protect the fiber reinforced layer (2).

5. A tensile and compressive flame resistant optical fiber cable according to claim 1, wherein, The inner sheath (4) is extruded from a low-smoke halogen-free ceramic polyolefin material outside the first armored layer (3); the preparation steps of the low-smoke halogen-free ceramic polyolefin material in the inner sheath (4) of the tensile and compressive resistance flame-retardant optical cable are as follows: mixing the polyethylene, the ethylene-vinyl acetate copolymer, the magnesium hydroxide, and the polycarbosilane in a mass fraction ratio of 37-40:28-30:33-35 to obtain a mixed material A, and pressing to obtain the low-smoke halogen-free ceramic polyolefin material.

6. A tensile and compressive flame resistant optical fiber cable according to claim 1, wherein: The preparation steps of the flame-retardant outer sheath of the tensile and compressive resistance flame-retardant optical cable are as follows: putting the modified hydroxide, the modified nano boron oxide, and the polypropylene into a plastic mixing machine in a mass fraction ratio of 2:0.5-0.7:5-6 to obtain the flame-retardant outer sheath (5) by melt blending.

7. A tensile and compressive flame resistant optical cable according to claim 6, wherein, The preparation steps of the modified hydroxide are as follows: drying magnesium hydroxide and aluminum hydroxide; adding a water bath kettle, and dropping a solution of KH-560 silane coupling agent diluted with anhydrous ethanol; after the dropping is completed, stirring at a speed of 600-650 rpm, and constant temperature drying to obtain the modified hydroxide.

8. A tensile and compressive flame resistant optical cable according to claim 6, characterized in that: The preparation steps of the modified nano boron oxide are as follows: putting multi-walled carbon nanotubes into a three-necked round-bottom flask, adding a nitric acid solution and a sodium dodecyl sulfate aqueous solution for functionalization treatment, filtering and drying; then placing in a beaker, adding a sodium dodecyl sulfate aqueous solution for ultrasonic dispersion to obtain modified multi-walled carbon nanotubes; Placing nano boron oxide in a beaker, adding the modified multi-walled carbon nanotubes and a DMF solution, ultrasonic dispersion, filtration, and drying to obtain the modified nano boron oxide.

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