Cold-resistant and anti-cracking type silicone rubber special cable

Abstract

The application belongs to the technical field of cable materials, and discloses a cold-resistant and anti-cracking type special cable made of silicone rubber, which comprises a conductor cable core, an inner protective sleeve and an outer protective sleeve from inside to outside, wherein the raw materials of the outer protective sleeve comprise end-vinyl diphenyl siloxane, methyl vinyl siloxane, silane modified nano silicon dioxide, polyborosiloxane, an inhibitor, hydroxyl silicone oil, modified anti-ultraviolet polyurethane, a platinum catalyst and tetra(dimethylsiloxane) silane; diphenyl siloxane with a diphenyl side chain is selected as a main chain, and the modified anti-ultraviolet polyurethane is grafted to effectively destroy the structural regularity, inhibit low-temperature crystallization and prevent cable cracking; 4,4'-diamino benzophenone with anti-ultraviolet function is used as a chain extender and benzotriazole is used as an end-capping agent to be grafted into the polyurethane chain, so that the anti-ultraviolet capacity can be improved and migration can be avoided.

Description

Technical Field

[0001] This invention relates to the field of cable material technology, specifically to a cold-resistant and crack-resistant silicone rubber special cable. Background Technology

[0002] In extremely cold fields such as high-latitude power transmission and distribution, polar scientific research equipment, and aerospace, cables, as the core carriers of energy and signal transmission, directly determine the safety of system operation due to their cold resistance. Traditional silicone rubber with polydimethylsiloxane as the main chain has excellent electrical insulation, high temperature resistance, and extremely low glass transition temperature, and is widely used in the preparation of low-temperature cables. However, polydimethylsiloxane has good structural regularity and is prone to crystallization at around -50 ℃. The constraint of the crystalline regions prevents the chain segments from moving, resulting in a sharp increase in elastic modulus and a decrease in ductility. Under mechanical vibration, thermal cycling, or installation stress, the outer sheath and insulation layer are prone to microcracks that can propagate rapidly, causing cable cracking, insulation breakdown, signal interruption, or even equipment failure. Therefore, it is not suitable for extremely cold operating environments below -50 ℃.

[0003] In addition, extremely cold regions are often accompanied by strong ultraviolet radiation, which causes cables to age and expose the conductor core. Researchers often add anti-aging fillers to the raw materials for cable preparation to achieve the effect of UV protection. However, the improvement of aging resistance requires a high filler content. A high filler content will lead to excessive viscosity, resulting in uneven mixing and uneven performance of silicone rubber. At the same time, there is a risk of filler migration, which cannot meet the long-term use requirements of extremely cold environments. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, the present invention provides a cold-resistant and crack-resistant silicone rubber special cable. The cold-resistant and crack-resistant silicone rubber special cable consists of a conductor core, an inner protective sheath, and an outer protective sheath from the inside out. The outer protective sheath is made by mixing, vulcanizing, and cooling and shaping tetra(dimethylsiloxane), methyl vinylsiloxane, silane-modified nano-silica, polyboron siloxane, inhibitor, hydroxyl silicone oil, modified UV-resistant polyurethane, platinum catalyst, and tetra(dimethylsiloxane). In this process, diphenylsiloxane is selected as the main chain. The presence of diphenyl side chains can disrupt the structural regularity, lower the crystallization temperature, and impart low-temperature flexibility. Simultaneously, grafting modified UV-resistant polyurethane onto diphenylsiloxane further reduces chain regularity and inhibits low-temperature crystallization. Furthermore, the introduction of polyurethane segments imparts excellent flexibility to the outer protective sheath of the silicone rubber cable, allowing it to disperse external forces and reduce cracking even at low temperatures through the movement of the flexible long chains of polyurethane. Grafting 4,4'-diaminobenzophenone (with UV resistance) as a chain extender and benzotriazole as a capping agent into the polyurethane chain improves UV resistance and prevents migration. Additionally, polyborosiloxane is used as a blending modifier. The reversible breaking and formation of the BO bonds in polyborosiloxane synergistically works with the polyurethane segments to dissipate external forces and prevent cable cracking.

[0005] The purpose of this invention is to provide a cold-resistant and crack-resistant silicone rubber special cable.

[0006] This invention is achieved through the following technical solution:

[0007] A cold-resistant and crack-resistant silicone rubber special cable, comprising, from the inside out, a conductor core, an inner protective sheath, and an outer protective sheath, wherein the outer protective sheath comprises, by weight, the following components: 60 parts of terminal alkenyl diphenylsiloxane, 35-45 parts of methyl vinyl siloxane, 35-60 parts of silane-modified nano-silica, 3-6 parts of polyboron siloxane, 0.02-0.05 parts of inhibitor, 6-20 parts of hydroxyl silicone oil, 10-30 parts of modified UV-resistant polyurethane, 8-11 parts of tetra(dimethylsiloxane)silane, and 0.01-0.06 parts of platinum catalyst;

[0008] The modified UV-resistant polyurethane was prepared by polymerization of diisocyanate with hydroxyl-terminated vinylmethyl-dimethyl copolymer siloxane as polyol, 4,4'-diaminobenzophenone as chain extender, and benzotriazole as end-capping agent.

[0009] Specifically, the inhibitor is ethynylcyclohexanol.

[0010] Specifically, the platinum catalyst is a Karstedt catalyst.

[0011] In one specific embodiment, the preparation of the modified UV-resistant polyurethane includes the following steps:

[0012] S1. Under nitrogen protection, hydroxyl-terminated vinylmethyl-dimethyl copolysiloxane is added to a dry reactor, heated to 70-85 ℃ and stirred for 5-10 minutes; diisocyanate is slowly added dropwise, followed by an organotin catalyst; the temperature is raised to 85-95 ℃ and reacted for 4-6 hours to obtain the prepolymer;

[0013] S2. Cool the prepolymer to 50-60 ℃, add the chain extender and react for 2-3 hours;

[0014] S3. Turn off the heating, add the end-capping agent, and stir for 0.5-1.5 hours to obtain the modified UV-resistant polyurethane.

[0015] In one specific embodiment, in step S1, the diisocyanate is one of methyl hexanoate 2,6-diisocyanate, cyclohexane-1,4-diisocyanate, and isophorone diisocyanate, and the amount used is 2.05-2.1 times the molar amount of hydroxyl-terminated vinylmethyl-dimethyl copolysiloxane; the organotin catalyst is dibutyltin dilaurate, and the amount used is 0.01-0.5 wt% of the mass of hydroxyl-terminated vinylmethyl-dimethyl copolysiloxane.

[0016] In one specific embodiment, in step S2, the chain extender is 4,4'-diaminobenzophenone, and the amount used is 0.1-0.5 times the molar amount of hydroxyl-terminated vinylmethyl-dimethyl copolysiloxane;

[0017] In one specific embodiment, in step S3, the capping agent is benzotriazole, and the amount used is 1.1-2 times the molar amount of hydroxyl-capped vinylmethyl-dimethyl copolysiloxane; the number average molecular weight of the modified UV-resistant polyurethane is 4000-5500.

[0018] In one specific embodiment, the preparation of the terminal alkenyl diphenylsiloxane includes the following steps:

[0019] Dihydroxyl-terminated poly(dimethylsiloxane-co-diphenylsiloxane) and 1-vinyl-1,1,3,3-tetramethyldisiloxane were mixed, and dibutyltin dilaurate was added dropwise. The mixture was heated to 90-120 °C, stirred for 2-6 hours, and then cooled to obtain alkenyl diphenylsiloxane.

[0020] In one specific embodiment, the amount of 1-vinyl-1,1,3,3-tetramethyldisiloxane is 2.05-2.1 times the molar amount of silanol in the dihydroxyl-terminated poly(dimethylsiloxane-co-diphenylsiloxane); and the amount of dibutyltin dilaurate is 0.01-0.5 wt% of the mass of the dihydroxyl-terminated poly(dimethylsiloxane-co-diphenylsiloxane).

[0021] In one specific embodiment, the silane-modified nano-silica is obtained by treating nano-silica with a particle size of 20-100 nm with silane coupling agent KH570.

[0022] In one specific embodiment, the preparation of the polyborosiloxane includes the following steps:

[0023] Boric acid and hydroxyl-terminated polydimethylsiloxane were mixed and stirred for 1-1.5 hours; the mixture was heated to 110-120 °C and stirred for 36-48 hours to obtain a crude product; the crude product was dissolved in n-hexane, purified and concentrated by column chromatography, and dried to obtain a transparent polyborosiloxane.

[0024] In one specific embodiment, the boric acid and hydroxyl-terminated polydimethylsiloxane are fed in an equimolar ratio of -OH (stoichiometric coefficient r = 1:1).

[0025] This invention also discloses a method for preparing a cold-resistant and crack-resistant silicone rubber special cable outer protective sleeve, comprising the following steps:

[0026] S1. Under vacuum conditions, pour terminal alkenyl diphenylsiloxane, methyl vinylsiloxane, and modified UV-resistant polyurethane into a mixer and mix at 100-130 ℃ for 15-30 minutes; add silane-modified nano silica in batches and mix at low speed of 200-500 rpm for 7-11 minutes; add polyboron siloxane and stir for 4-16 minutes; add inhibitor and hydroxyl silicone oil and stir for 3-5 minutes.

[0027] S2. Cool to 70-90 ℃, add tetra(dimethylsiloxane)silane, stir for 5-10 minutes; add platinum catalyst, stir rapidly for 0.5-1.5 minutes, and discharge to obtain the compound;

[0028] S3. The compound obtained in S2 is fed into a twin-screw granulator for extrusion molding, and uniformly coated on the surface of the inner protective sleeve with a thickness of 4.5-5 mm; vulcanized in a pipeline vulcanizing machine at 140-150 ℃ and 10-12 MPa for 12-16 minutes; then vulcanized at 180-220 ℃ and 0.1-0.2 MPa for 3-5 hours; and finally cooled and shaped to obtain the outer protective sleeve.

[0029] Beneficial effects

[0030] This invention provides a cold-resistant and crack-resistant silicone rubber special cable. The cold-resistant and crack-resistant silicone rubber special cable consists of a conductor core, an inner protective sheath, and an outer protective sheath from the inside out. The outer protective sheath is made by mixing, vulcanizing, and cooling and shaping alkenyl diphenylsiloxane, methyl vinyl siloxane, silane-modified nano silica, polyboron siloxane, inhibitor, hydroxyl silicone oil, modified UV-resistant polyurethane, tetra(dimethylsiloxane)silane, and platinum catalyst. Diphenylsiloxane is selected as the main chain. The presence of diphenyl side chains can disrupt the structural regularity, lower the crystallization temperature, and impart low-temperature flexibility. Simultaneously, grafting modified UV-resistant polyurethane onto the diphenylsiloxane further reduces chain regularity and inhibits low-temperature crystallization. Furthermore, the introduction of polyurethane segments imparts excellent flexibility to the outer protective sheath of the silicone rubber cable, and at low temperatures, the movement of the flexible long polyurethane chains disperses external forces, reducing crack formation. Grafting 4,4'-diaminobenzophenone (with UV resistance) as a chain extender and benzotriazole as a capping agent into the polyurethane chain improves UV resistance and prevents migration. Additionally, polyborosiloxane is used as a filler. The reversible breaking and formation of the BO bonds in polyborosiloxane, in synergy with the polyurethane segments, effectively dissipates external forces and prevents cable cracking. Attached Figure Description

[0031] Figure 1 The synthetic route for terminal alkenyl diphenylsiloxane;

[0032] Figure 2The infrared spectrum is shown for the outer protective sheath of the special cable made of modified UV-resistant polyurethane and cross-linked cold-resistant and crack-resistant silicone rubber in Example 1. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0035] The raw materials used in the examples and comparative examples are described below:

[0036] Diphenylsiloxane: Dihydroxyl-terminated poly(dimethylsiloxane-co-diphenylsiloxane), product number: 1765183, MW1000, purchased from Tianjin Xiens Biochemical Technology Co., Ltd.

[0037] 1-Vinyl-1,1,3,3-Tetramethyldisiloxane: 97%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0038] Organotin catalyst: Dibutyltin dilaurate (DBTDL), 95%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0039] Diisocyanate: Methyl 2,6-diisocyanate hexanoate, 97%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0040] Hydroxyl-terminated vinylmethyl-dimethyl copolysiloxane: viscosity 30-40 cst, vinyl content 10.2-13.2%, purchased from Beijing Huawirui Chemical Technology Co., Ltd.

[0041] Chain extender: 4,4'-diaminobenzophenone, 98%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0042] End-capping agent: benzotriazole, 99.5%, purchased from Nanjing Huayan Chemical Co., Ltd.;

[0043] Tetra(dimethylsiloxane)silane: 96%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0044] Alkali catalyst: Triethylamine (TEA), 99.5%, product number T818774, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0045] Platinum catalyst: Karstedt catalyst, Pt content 2%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0046] Inhibitor: Ethynylcyclohexanol, product code E809391, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0047] Dimethylsiloxane: Dihydroxy-terminated polydimethylsiloxane (PDMS), 65 cst, purchased from Sigma-Aldrich, USA;

[0048] Boric acid (BA): 99.5%, product number B802844, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0049] Silane coupling agent: KH570, 99%, purchased from Shandong Yifei Science and Trade Co., Ltd.;

[0050] Silane-modified nano silica: Nano silica, particle size 20 nm, purity 99 wt%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; Silane coupling agent: KH570, 99%, purchased from Shandong Yifei Science and Trade Co., Ltd.; The weight ratio of nano silica to silane coupling agent is 100:1.5.

[0051] Methylvinylsiloxane 1: MVQ110-0, with a vinyl content of 0.03~0.06%, was purchased from Hoshine Silicon Industry Co., Ltd.

[0052] Methylvinylsiloxane 2: MVQ110-3, with a vinyl content of 0.19~0.24%, was purchased from Hoshine Silicon Industry Co., Ltd.

[0053] Hydroxy silicone oil: hydroxyl content 8 wt.%, purchased from Wuhan Jiyesheng Chemical Co., Ltd.;

[0054] Terminally alkenyl diphenylsiloxane: Prepared in-house, the preparation method is as follows:

[0055] Dihydroxyl-terminated poly(dimethylsiloxane-co-diphenylsiloxane) and 1-vinyl-1,1,3,3-tetramethyldisiloxane were stirred and mixed at room temperature for 10-15 minutes, with a silane-to-silanol molar ratio in the range of 2.05-2.2:1. Dibutyltin dilaurate (0.01-0.5 wt%) was slowly added dropwise, and stirring was continued for 15-20 minutes. The temperature was slowly increased to 90-120 °C, and the reaction was stirred for 2-6 hours until no bubbles were generated, at which point the reaction was terminated. After cooling, alkenyl diphenylsiloxane was obtained.

[0056] Terminal alkenyl dimethylsiloxane: self-made. The preparation method is different from that of terminal alkenyl diphenylsiloxane in that the dihydroxyl-terminated poly(dimethylsiloxane-co-diphenylsiloxane) is replaced with dihydroxyl-terminated poly(dimethylsiloxane).

[0057] Modified UV-resistant polyurethane: self-made, preparation method as follows:

[0058] S1. Dehydrated hydroxyl-terminated vinylmethyl-dimethyl copolysiloxane (1 molar equivalent) was added to a dry reactor under nitrogen protection and heated to 80 °C with stirring for 10 minutes; methyl hexanoate 2,6-diisocyanate (2.05 molar equivalent) was slowly added dropwise, and after half an hour, dibutyltin dilaurate (0.03 wt%) was added to accelerate the reaction; the temperature was raised to 90 °C and reacted for 5 hours to obtain a methyl hexanoate-terminated prepolymer.

[0059] S2. Cool the prepolymer to 60 °C, add 4,4'-diaminobenzophenone (0.3 molar equivalent) for chain extension, and stir rapidly for 3 hours.

[0060] S3. Turn off the heating, add benzotriazole (1.1 molar equivalent), stir for 1 hour, and obtain benzotriazole-terminated modified UV-resistant polyurethane with a number average molecular weight of 4500.

[0061] Polyurethane: In-house prepared. The preparation method differs from that of modified UV-resistant polyurethane in that 4,4'-diaminobenzophenone is replaced with ethylene glycol and benzotriazole is replaced with methanol.

[0062] Polyborosiloxane (PBS): Prepared in-house, as follows:

[0063] Boric acid was ground and filtered through a 100-mesh aluminum sieve, then dried in a vacuum drying oven at 120 °C for 24 hours. Boric acid and hydroxyl-terminated polydimethylsiloxane (PDMS) were added at an equimolar ratio of -OH (stoichiometric coefficient r = 1:1), and stirred at room temperature for 1 hour. The mixture was then heated to 120 °C and stirred for 48 hours to obtain a crude product, denoted as PBS. The crude product was dissolved in n-hexane and purified by column chromatography to obtain a clear solution. The n-hexane was removed by rotary evaporation, and the solution was dried under vacuum at 60 °C for 24 hours to finally obtain transparent PBS.

[0064] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0065] Examples and Comparative Examples

[0066] A cold-resistant and crack-resistant silicone rubber special cable comprises, from the inside out, a conductor core, an inner protective sheath, and an outer protective sheath. The weight composition of the outer protective sheath is shown in Table 1, and the preparation method is as follows:

[0067] S1. Under vacuum conditions, terminal alkenyl diphenylsiloxane, methyl vinyl siloxane and modified UV-resistant polyurethane are poured into a mixer and mixed at 120 °C for 15 minutes; silane-modified nano silica is added in batches and mixed at low speed for 7 minutes; polyboron siloxane is added and stirred for 10 minutes; inhibitor and hydroxyl silicone oil are added and stirred for 5 minutes.

[0068] S2. Cool to 80 ℃, add tetra(dimethylsiloxane)silane, stir for 10 minutes; add platinum catalyst, stir rapidly for 1 minute, and discharge to obtain the compound;

[0069] S3. The compound obtained in S2 is fed into a twin-screw granulator for extrusion molding, and uniformly coated on the surface of the inner protective sleeve with a thickness of 5 mm; it is then vulcanized in a pipeline vulcanizing machine at 145 ℃ and 12 MPa for 16 minutes; then the temperature is slowly increased to 200 ℃ and the pressure is reduced to 0.1 MPa for 4 hours; the outer protective sleeve is obtained by cooling and shaping.

[0070] Table 1. Cold-resistant and crack-resistant silicone rubber special cable outer protective sleeve (parts by weight)

[0071]

[0072] The cold-resistant and crack-resistant silicone rubber special cable outer protective sleeve prepared in the examples and comparative examples was subjected to the following performance tests, and the results are attached. Figure 2 As shown in Table 2.

[0073] 1. Infrared Spectroscopy: The modified UV-resistant polyurethane and cross-linked cold-resistant and crack-resistant silicone rubber special cable outer protective sheath from Example 1 were mixed with potassium bromide at a ratio of 1:50 to prepare a pellet. An Avatar 380 spectrometer was used for this test. Before testing, a blank background was scanned, and then the pellet sample was placed in the sample for testing. The scanning range was 500-4000 cm⁻¹. -1 The result is as follows Figure 1 As shown.

[0074] 2. Tensile strength and elongation at break: According to ASTM D412 standard, a universal testing machine was used to test the tensile strength and tensile properties at break of the outer protective sleeve specimen before cryogenic treatment. The dumbbell-shaped protective sleeve specimen was neatly clamped at both ends on a tensile testing machine, the tensile speed was set to 500±50 mm / min, and the stress-strain curves were recorded in real time until the outer protective sleeve specimen broke.

[0075] 3. Anti-aging properties: Take a 1×1×0.5 cm outer protective sleeve sample and place it in a UV aging test chamber. Set the temperature to room temperature and humidity to 55%. After aging for one week, measure the percentage decrease in its tensile properties.

[0076] 4. Low temperature resistance: According to GB / T 2951.14-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers", a 40×1×0.5 cm outer protective sheath sample is uniformly wrapped around a 4 cm diameter test rod 4 times at a speed of 5 seconds per turn, and then frozen at -70 ℃ and -50 ℃ for 4 hours. The surface of the sample is then observed for any cracks.

[0077] 5. Cold-resistant compression coefficient: Performed according to GB / T3866-2008 standard. Using a special mold, the compound is vulcanized into cylinders with a diameter of 1 cm and a height of 1 cm. These cylinders are placed at -70 ℃ for 3 minutes, and the original height h0 is measured. They are then removed and quickly compressed to 80% of their original height, and the compression height h1 is recorded. The cylinders are then placed back at -70 ℃ for 3 minutes to recover, and the final height h2 is measured. The cold-resistant compression coefficient Kc is calculated using the following formula:

[0078] .

[0079] Table 2 Performance test results of cable outer sheath

[0080]

[0081] From the appendix Figure 2 As can be seen from the spectrum of the modified UV-resistant polyurethane, the absorption signals of several raw materials used in the synthesis of the modified UV-resistant polyurethane were observed, with peak values ​​appearing in the 3000-2850 cm⁻¹ range. -1 The stretching vibrations attributed to CH2 peak at 1200-1000 cm⁻¹. -1 The COC in hydroxyl-terminated vinylmethyl-dimethyl cosiloxane and urethane, along with the stretching vibration of Si-O-Si, peaks at 1640 cm⁻¹. -1 Characteristic absorptions attributable to double bonds, with peak values ​​appearing at 1380-1250 cm⁻¹. -1 Attributable to the stretching vibrations of -Si-C; peak occurs at 1660 cm⁻¹ -1 The characteristic absorption peak at -C=O in the chain extender 4,4'-diaminobenzophenone appears at 830 cm⁻¹. -1 Characteristic signal attributed to para-benzene; peak appears at 1660 cm⁻¹ -1 Belongs to 1550 cm -1 and 1475 cm -1 The double peaks represent the fingerprint signal of benzotriazole, 1270 cm⁻¹.-1 The location is the characteristic signal of CN within the ring; and at 3500 cm -1 No absorption peaks belonging to Si-OH were observed nearby, nor was a peak observed at 2270 cm⁻¹. -1 The presence of an infrared signal unique to -NCO indicates the successful synthesis of modified UV-resistant polyurethane.

[0082] In the spectrum of the outer protective sheath of the cold-resistant and crack-resistant silicone rubber special cable, the peak value is at 1340 cm⁻¹. -1 The characteristic absorption signal of -BO in the filler PBS was observed to have disappeared, and the characteristic absorption of -Si-H in tetra(dimethylsiloxane)silane was not observed near 2300-2100. This indicates that the terminal alkenyl diphenylsiloxane, methyl vinylsiloxane, modified UV-resistant polyurethane and tetra(dimethylsiloxane)silane are completely cross-linked, and the cold-resistant and crack-resistant silicone rubber special cable outer protective sleeve was successfully prepared.

[0083] As can be seen from the tensile strength and elongation at break data in Table 2, compared with Comparative Example 4, the outer protective sleeves prepared in Examples 1-3, which graft modified UV-resistant polyurethane long-chain segments onto terminal alkenyl diphenylsiloxane, exhibit better flexibility and excellent cold-resistant compression coefficients, all above 0.7. Furthermore, no cracks appeared after being subjected to circular freezing at -70 ℃ for 4 hours. This is because the graft modification of UV-resistant polyurethane not only reduces the Tg of the terminal alkenyl diphenylsiloxane but also disrupts its chain segment regularity, lowering the crystallization temperature. This allows the molecular chains to maintain motion at -70 ℃, and the reversible breakage and formation of BO bonds in the polyborosiloxane synergistically dissipates external forces, preventing crack formation.

[0084] Furthermore, Comparative Example 1, using terminal alkenyl dimethylsiloxane as the main chain to modify UV-resistant polyurethane, improved its low-temperature crystallization performance to some extent, preventing catalytic cracking at -50 ℃. However, due to the relatively symmetrical structure of its main polydimethylsiloxane chain, the molecular chain movement slowed down at -70 ℃, easily leading to inter-chain interactions and crystallization. The chains were bound by the crystalline regions and could not move, resulting in cracks. Correspondingly, after low-temperature compression and removal of external force, the frozen chain segments could not move and recover, exhibiting a low cold resistance coefficient. Comparative Example 3, lacking polyborosiloxane, could not dissipate external force through reversible breaking and formation of BO bonds, but the molecular chains could still move to disperse some of the external force, resulting in slight cracks.

[0085] As can be seen from Comparative Examples 2 and 4 in Table 2, the modified UV-resistant polyurethanes without grafting UV-resistant function all have poor anti-aging properties.

[0086] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A cold-resistant and anti-cracking type of silicone rubber special cable, characterized in that the cold-resistant and anti-cracking type of silicone rubber special cable sequentially comprises a conductor core, an inner protective sleeve and an outer protective sleeve from inside to outside, wherein the outer protective sleeve comprises the following components in parts by weight: end-vinyl phenyl siloxane 60 parts, methyl-vinyl siloxane 35-45 parts, silane-modified nano-silica 35-60 parts, polyborosiloxane 3-6 parts, inhibitor 0.02-0.05 parts, hydroxyl silicone oil 6-20 parts, modified anti-ultraviolet polyurethane 10-30 parts, tetra(dimethylsiloxane) silane 8-11 parts, platinum catalyst 0.01-0.06 parts; the methyl-vinyl siloxane is MVQ110-0 or MVQ110-3; the modified anti-ultraviolet polyurethane is prepared by polymerization of hydroxyl-terminated vinyl-methyl-dimethyl copolymerized siloxane as a polyol, 4,4'-diamino benzophenone as a chain extender, benzotriazole as an end-capping agent and diisocyanate; the preparation of the end-vinyl phenyl siloxane comprises the following steps: mixing hydroxyl-terminated poly(dimethyl siloxane-co-diphenyl siloxane) and 1-vinyl-1,1,3,3-tetramethyldisiloxane, adding dibutyl tin dilaurate dropwise, heating to 90-120 ℃, stirring for 2-6 hours, cooling to obtain end-vinyl phenyl siloxane.

2. The cold-resistant, crack-resistant silicone special electrical cable of claim 1, wherein, the inhibitor is ethynyl cyclohexanol; the platinum catalyst is Karstedt catalyst; the modified nano-silica is obtained by treating nano-silica with a particle size of 20-100 nm by silane coupling agent KH570.

3. The cold-resistant and anti-cracking type silicone rubber special cable according to claim 1, characterized in that, the preparation of the modified anti-ultraviolet polyurethane comprises the following steps: S1. under nitrogen protection, hydroxyl-terminated vinyl-methyl-dimethyl copolymerized siloxane is added into a dry reactor, heated to 70-85 ℃ and stirred for 5-10 minutes; diisocyanate is slowly added dropwise, and then organic tin catalyst is added; heated to 85-95 ℃ and reacted for 4-6 hours to obtain a prepolymer; S2. the prepolymer is cooled to 50-60 ℃, a chain extender is added and reacted for 2-3 hours; S3. turn off the heating, add an end-capping agent, stir for 0.5-1.5 hours to obtain the modified anti-ultraviolet polyurethane.

4. The cold-resistant, crack-resistant silicone special electrical cable of claim 3, wherein, in the step S1, the diisocyanate is one of 2,6-diisocyanate methyl hexanoate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, and the amount is 2.05-2.1 times of the molar amount of the hydroxyl-terminated vinyl-methyl-dimethyl copolymerized siloxane; the organic tin catalyst is dibutyl tin dilaurate, and the amount is 0.01-0.5 wt% of the mass of the hydroxyl-terminated vinyl-methyl-dimethyl copolymerized siloxane; in the step S2, the chain extender is 4,4'-diamino benzophenone, and the amount is 0.1-0.5 times of the molar amount of the hydroxyl-terminated vinyl-methyl-dimethyl copolymerized siloxane.

5. The cold-resistant and anti-cracking type silicone rubber special cable according to claim 3, characterized in that, in the step S3, the end-capping agent is benzotriazole, and the amount is 1.1-2 times of the molar amount of the hydroxyl-terminated vinyl-methyl-dimethyl copolymerized siloxane; the number average molecular weight of the modified anti-ultraviolet polyurethane is 4000-5500.

6. The cold-resistant, crack-resistant silicone special electrical cable of claim 1, wherein, The amount of 1-vinyl-1,1,3,3-tetramethyldisiloxane is 2.05-2.1 times the molar amount of silanol in the dihydroxyl-terminated poly(dimethylsiloxane-co-diphenylsiloxane); the amount of dibutyltin dilaurate is 0.01-0.5 wt% of the mass of the dihydroxyl-terminated poly(dimethylsiloxane-co-diphenylsiloxane).

7. The cold-resistant, crack-resistant silicone special electrical cable of claim 1, wherein, The preparation of the polyborosiloxane comprises the following steps: The boric acid and the hydroxyl-terminated polydimethylsiloxane are mixed and stirred at an -OH equivalent molar ratio for 1-1.5 hours, heated to 110-120 ℃ and stirred for 36-48 hours to obtain a crude product; the crude product is dissolved in n-hexane, purified by a chromatographic column, concentrated, dried and obtained as a transparent polyborosiloxane.

8. The cold-resistant, crack-resistant silicone special electrical cable according to any one of claims 1 to 7, characterized in that The preparation method of the cable outer protective sleeve comprises the following steps: S1. Under vacuum conditions, end-vinyl diphenylsiloxane, methyl vinyl siloxane and modified anti-UV polyurethane are poured into an internal mixer, mixed at 100-130 ℃ for 15-30 minutes; batched silane-modified nano-silicon dioxide is added, low-speed mixed at 200-500 rpm for 7-11 minutes; polyborosiloxane is added and stirred for 4-16 minutes; inhibitors and hydroxyl silicone oil are added and stirred for 3-5 minutes; S2. The temperature is lowered to 70-90 ℃, tetra(dimethylsiloxane) silane is added and stirred for 5-10 minutes; platinum catalyst is added and quickly stirred for 0.5-1.5 minutes, and the material is discharged to obtain a mixed rubber; S3. The mixed rubber obtained in S2 is sent into a double-screw granulator for extrusion molding, uniformly coated on the surface of the inner protective sleeve with a thickness of 4.5-5 mm; vulcanization is carried out in a pipe vulcanizer at 140-150 ℃, 10-12 MPa for 12-16 minutes; the temperature is raised to 180-220 ℃, the pressure is reduced to 0.1-0.2 MPa for vulcanization for 3-5 hours; cooling and shaping to obtain the outer protective sleeve.

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