PVC threading pipe and preparation method and application thereof

Abstract

The application belongs to the technical field of threading pipe, and discloses a PVC threading pipe, a preparation method and application thereof, the PVC threading pipe comprises the following raw materials by weight: 100 parts of PVC resin, 8-14 parts of flame retardant, 12-18 parts of reinforcing filler, 0.6-1.5 parts of lubricant and 0.8-1.2 parts of antioxidant; wherein the flame retardant comprises modified chitin and aluminum hydroxide uniformly dispersed in a carrier; and the reinforcing filler is obtained by mixing modified basalt fiber, vinyl silicone oil and silicone rubber; the PVC threading pipe is provided with a specific flame retardant system and a reinforcing filler system, efficient cooperation of the flame retardation performance and the mechanical performance is realized, the flame retardant efficiently plays a flame retardation role, the reinforcing filler fully improves the mechanical performance, and both do not damage the processing performance and the structural stability of the PVC matrix, so that the PVC threading pipe simultaneously has excellent flame retardation, compression resistance and impact resistance and processing applicability.

Description

Technical Field

[0001] This invention belongs to the field of conduit technology, and specifically relates to a PVC conduit, its preparation method, and its application. Background Technology

[0002] PVC conduit, as a core material for the protection of power and signal lines, is widely used in various fields, including civil buildings, public gathering places, industrial plants, energy storage power stations, and rail transit tunnels. Different scenarios place increasingly stringent requirements on the safety performance, structural reliability, and environmental adaptability of conduit. In terms of fire safety, the flame-retardant ability of traditional PVC conduit is significantly limited. When encountering localized high temperatures caused by short circuits due to aging wiring or external fires, the conduit is prone to rapid combustion and loses its protective function for internal wiring. Furthermore, the molten drippings produced during combustion may even exacerbate the fire, posing a direct threat to personnel evacuation and property safety. In addition, existing inorganic flame retardants used to improve flame-retardant performance often suffer from poor compatibility with the PVC resin matrix, resulting in uneven dispersion. This not only fails to fully exert its flame-retardant effect but may also reduce the overall toughness of the conduit, making it difficult to adapt to bending operations during construction. In terms of structural strength, traditional PVC conduits rely on a single inorganic filler to improve compressive strength. These fillers have weak interfacial bonding with PVC resin and are prone to agglomeration in the matrix, resulting in uneven distribution of the mechanical properties of the pipe. When pre-embedded in walls, laid in ground bedding, or installed around equipment, they are easily deformed or even damaged by external pressure, vibration, or heavy objects, which in turn leads to obstruction of subsequent wiring and increases the cost of rework and construction difficulty. Summary of the Invention

[0003] The present invention aims to improve at least one technical problem in the prior art.

[0004] The first aspect of this invention provides a PVC conduit, comprising the following raw materials in parts by weight:

[0005] 100 parts PVC resin, 8-14 parts flame retardant, 12-18 parts reinforcing filler, 0.6-1.5 parts lubricant, and 0.8-1.2 parts antioxidant;

[0006] The flame retardant includes a carrier and aluminum hydroxide uniformly dispersed on the carrier. The carrier is modified chitosan, which is obtained by sequentially deacetylifying chitosan and modifying it with a first silane coupling agent. The mass ratio of modified chitosan to aluminum hydroxide is 1:(0.5-0.85), the degree of deacetylation of modified chitosan is 25%-35%, and the mass ratio between chitosan and the first silane coupling agent is 1:(0.15-0.3).

[0007] The reinforcing filler is obtained by mixing modified basalt fiber, vinyl silicone oil and silicone rubber. The modified basalt fiber is obtained by modifying the surface of basalt fiber with a second silane coupling agent and butyl acrylate. The mass ratio of modified basalt fiber, vinyl silicone oil and silicone rubber is 1:(4-6):(5-7), and the mass ratio of basalt fiber to the second silane coupling agent is 1:(0.01-0.02).

[0008] In the PVC conduit provided by this invention, the flame retardant system uses aluminum hydroxide as the flame retardant core and modified chitin as the carrier. After deacetylation treatment, a large number of polar groups such as amino and hydroxyl groups are introduced into the molecular chain of chitin. These groups can form a tight bond with the hydroxyl groups on the surface of aluminum hydroxide through hydrogen bonding and coordination, stably encapsulating the aluminum hydroxide particles and dispersing them evenly in the carrier. This avoids the aggregation of traditional inorganic flame retardants due to high surface energy and ensures that the flame retardant components are evenly distributed in the PVC matrix. Then, the deacetylated chitin is further modified by a first silane coupling agent to construct an "interfacial bridge" between the flame retardant and the PVC resin. The polar group (such as amino) at one end of the first silane coupling agent can react and combine with the hydroxyl and amino groups of the deacetylated chitin, while the non-polar group (such as alkoxy) at the other end can have a compatibility effect with the molecular chain of the PVC resin. This allows the flame retardant to be firmly anchored in the PVC matrix without causing interfacial repulsion with PVC due to excessive polarity differences.

[0009] In the PVC conduit provided by this invention, basalt fiber is used as the reinforcing core for the filler. The surface of the basalt fiber is modified by a second silane coupling agent. One end of the second silane coupling agent reacts with the hydroxyl groups on the surface of the basalt fiber to form covalent bonds, while the other end introduces unsaturated double bonds or polar groups, providing active sites for the bonding of the fiber and organic components. Modification of the basalt fiber surface with butyl acrylate utilizes the compatibility of the ester groups of butyl acrylate with PVC resin, and the double bonds in butyl acrylate can undergo grafting reactions with free radicals generated during PVC processing, forming a "PVC affinity layer" on the surface of the basalt fiber, thus improving the interfacial bonding strength between the reinforcing fiber and the PVC matrix. This invention mixes the modified basalt fiber with vinyl silicone oil and silicone rubber. The flexibility of the vinyl silicone oil and the elasticity of the silicone rubber can be used to adjust the overall toughness of the reinforcing filler, avoiding the increased brittleness of the PVC conduit caused by simple fiber reinforcement.

[0010] In general, PVC resin serves as the matrix, providing a support framework for flame retardants and reinforcing fillers. The flame retardant forms an interfacial bond with PVC through a first silane coupling agent. The polar groups of its carrier (modified chitosan) can form weak interactions with the chlorine atoms of PVC, allowing the flame retardant to be uniformly dispersed in the interstices of the PVC molecular chains. This not only avoids interfering with the processing flowability of PVC but also blocks the combustion chain of PVC during combustion through the decomposition of aluminum hydroxide. The reinforcing filler, modified with a second silane coupling agent and butyl acrylate, forms a stronger interfacial bond with PVC. Basalt fibers form a "three-dimensional skeleton" within the PVC matrix, improving the overall mechanical properties of the PVC conduit. Meanwhile, the silicone rubber component in the reinforcing filler forms hydrogen bonds with the hydroxyl groups of the flame retardant carrier, creating a "mutual anchoring" between the flame retardant and the reinforcing filler, preventing them from agglomerating in the PVC matrix and further ensuring the uniformity of the overall material. The lubricant improves the flowability of each raw material component during mixing and processing, reduces frictional resistance between materials, and enhances the surface smoothness and molding stability of the PVC conduit. The antioxidant can inhibit or delay the oxidative aging of PVC resin and other organic components during processing and use, reduce material performance degradation caused by factors such as high temperature and light, extend the service life of the PVC conduit, and ensure its performance stability during long-term use.

[0011] Preferably, the average particle size of aluminum hydroxide is 3μm-10μm.

[0012] Preferably, the average length of the basalt fiber is 2.5 mm to 4.0 mm.

[0013] Preferably, the first silane coupling agent includes at least one selected from γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane.

[0014] Preferably, the second silane coupling agent includes at least one of γ-(methacryloyloxy)propyltriethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, and methacryloyloxymethyltrimethoxysilane.

[0015] The preparation of the flame retardant in this invention includes the following steps:

[0016] Chitin was added to NaOH solution, and then NaBH4 was added to carry out a deacetylation reaction. After freeze-drying, deacetylated chitin was obtained.

[0017] Deacetylated chitin was dispersed in water, a first silane coupling agent was added, and the mixture was stirred. Then aluminum hydroxide was added and stirred again to obtain a flame retardant.

[0018] The mass ratio of chitin to NaBH4 is 1:(0.016-0.02); the deacetylation reaction temperature is 90℃-96℃, and the deacetylation reaction time is 2h-4h.

[0019] The preparation of the reinforcing filler in this invention includes the following steps:

[0020] Basalt fiber, second silane coupling agent and butyl acrylate are added to vinyl silicone oil, mixed well and sand-milled to obtain a mixed slurry.

[0021] The mixed slurry is kneaded with silicone rubber to obtain the reinforcing filler.

[0022] The grinding speed is 200r / min-250r / min, and the grinding time is 18h-24h; the kneading is carried out at 130℃-150℃, and the kneading time is 8h-12h.

[0023] Preferably, the lubricant includes at least one of calcium stearate, glyceryl stearate, paraffin wax, and polyethylene wax.

[0024] Preferably, the antioxidant includes at least one of antioxidant CA, antioxidant 1010, antioxidant 168, antioxidant 245 and antioxidant 1076.

[0025] A second aspect of the present invention provides a method for preparing the above-mentioned PVC conduit, comprising the following steps:

[0026] The PVC resin, flame retardant, reinforcing filler, lubricant, and antioxidant are mixed to obtain a mixture;

[0027] The mixture is plasticized and molded to obtain PVC conduit.

[0028] Furthermore, the PVC resin, flame retardant, and reinforcing filler are premixed before mixing.

[0029] The third aspect of this invention provides the application of the above-mentioned PVC conduit in industrial plant wiring.

[0030] The beneficial effects of the present invention are as follows: The PVC conduit of the present invention achieves efficient synergy between flame retardant performance and mechanical properties through a specific flame retardant system and a reinforcing filler system. The flame retardant effectively exerts its flame retardant effect, and the reinforcing filler fully enhances the mechanical properties. Neither of these measures damages the processing performance and structural stability of the PVC matrix, so that the PVC conduit simultaneously possesses excellent flame retardancy, pressure and impact resistance, and processing applicability. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] Example 1

[0033] A PVC conduit comprises the following raw materials in parts by weight: 100 parts PVC resin, 10 parts flame retardant, 13 parts reinforcing filler, 0.8 parts calcium stearate (lubricant), and 1 part antioxidant CA (antioxidant).

[0034] The flame retardant includes modified chitin (carrier) and aluminum hydroxide uniformly dispersed in the modified chitin. The modified chitin is obtained by sequentially deacetylifying chitin and modifying it with γ-aminopropyltriethoxysilane. The mass ratio of modified chitin to aluminum hydroxide is 1:0.6, the degree of deacetylation of the modified chitin is 30%, and the average particle size of the aluminum hydroxide is 5 μm.

[0035] The preparation of flame retardants includes the following steps:

[0036] Chitosan was added to NaOH solution (35 wt%), and then NaBH4 was added (the mass ratio of chitosan to NaBH4 was 1:0.018). After ultrasonic dispersion for 1 h, deacetylation reaction was carried out at 90 °C for 3 h. The mixture was washed with deionized water until neutral and then freeze-dried to obtain deacetylated chitosan.

[0037] Deacetylated chitin was dispersed in water, and γ-aminopropyltriethoxysilane (the mass ratio of chitin to γ-aminopropyltriethoxysilane was 1:0.2) was added. The mixture was stirred for 2 hours to mix thoroughly, and then aluminum hydroxide was added. The mixture was stirred for 4 hours to mix thoroughly to obtain the flame retardant.

[0038] The reinforcing filler is obtained by mixing modified basalt fiber, vinyl silicone oil and silicone rubber in a mass ratio of 1:5.5:6. The modified basalt fiber is obtained by modifying the surface of basalt fiber with γ-(methacryloyloxy)propyltrimethoxysilane and butyl acrylate. The average length of the basalt fiber is 4 mm.

[0039] The preparation of reinforcing fillers includes the following steps:

[0040] Basalt fiber, second silane coupling agent and butyl acrylate were added to vinyl silicone oil and stirred for 2 hours to mix. The mixture was then sand-milled (the sand mill speed was 250 r / min and the sand milling time was 24 hours) to obtain a mixed slurry.

[0041] The mixed slurry and silicone rubber were kneaded at 140°C for 10 hours (kneading was done by stirring at a speed of 100 r / min) to obtain the reinforcing filler.

[0042] The preparation method of the PVC conduit in Example 1 includes the following steps:

[0043] PVC resin, flame retardant and reinforcing filler are premixed (premixed for 10 min at 600 rpm in a high-speed mixer), and then calcium stearate and antioxidant are added and mixed further (premixed for 20 min at 1000 rpm in a high-speed mixer) to obtain a mixture;

[0044] The mixture is fed into an extruder for plasticization (the temperatures of zones 1-4 of the extruder barrel are 178℃, 185℃, 182℃, and 158℃ respectively, the screw speed is 25r / min, and continuous extrusion is carried out). The mixture is then extruded into a mold for molding, and after cooling, PVC conduit is obtained.

[0045] Example 2

[0046] A PVC conduit comprises the following raw materials in parts by weight: 100 parts PVC resin, 8 parts flame retardant, 12 parts reinforcing filler, 0.6 parts glyceryl stearate (lubricant), and 0.8 parts antioxidant 1010 (antioxidant).

[0047] The flame retardant includes modified chitin (carrier) and aluminum hydroxide uniformly dispersed in the modified chitin. The modified chitin is obtained by sequentially deacetylifying chitin and modifying it with γ-aminopropyltrimethoxysilane (first silane coupling agent). The mass ratio of modified chitin to aluminum hydroxide is 1:0.5, the degree of deacetylation of the modified chitin is 25%, and the average particle size of aluminum hydroxide is 3μm.

[0048] The preparation of flame retardants includes the following steps:

[0049] Chitosan was added to NaOH solution (35 wt%), and then NaBH4 was added (the mass ratio of chitosan to NaBH4 was 1:0.016). After ultrasonic dispersion for 1 h, deacetylation reaction was carried out at 90 °C for 2 h. The mixture was washed with deionized water until neutral and then freeze-dried to obtain deacetylated chitosan.

[0050] Deacetylated chitin was dispersed in water, and γ-aminopropyltrimethoxysilane (the mass ratio of chitin to γ-aminopropyltrimethoxysilane was 1:0.15) was added. The mixture was stirred for 2 hours to mix thoroughly, and then aluminum hydroxide was added. The mixture was stirred for 4 hours to mix thoroughly to obtain the flame retardant.

[0051] The reinforcing filler is obtained by mixing modified basalt fiber, vinyl silicone oil and silicone rubber in a mass ratio of 1:4:5. The modified basalt fiber is obtained by modifying the surface of basalt fiber with γ-(methacryloyloxy)propyltriethoxysilane (second silane coupling agent) and butyl acrylate. The average length of the basalt fiber is 2.5 mm.

[0052] The preparation of reinforcing fillers includes the following steps:

[0053] Basalt fiber, γ-(methacryloyloxy)propyltriethoxysilane (mass ratio of basalt fiber to the second silane coupling agent is 1:0.01) and butyl acrylate are added to vinyl silicone oil, stirred for 2 hours to mix, and then sand-milled (sand milling speed is 200 r / min, sand milling time is 18 hours) to obtain a mixed slurry.

[0054] The mixed slurry and silicone rubber were kneaded at 130°C for 8 hours (kneading was done by stirring at a speed of 100 r / min) to obtain the reinforcing filler.

[0055] The preparation method of the PVC conduit in Example 2 includes the following steps:

[0056] The PVC resin, flame retardant, and reinforcing filler were premixed (premixed for 10 min at 600 rpm in a high-speed mixer), and then glyceryl stearate and antioxidant 1010 were added and further mixed (premixed for 20 min at 1000 rpm in a high-speed mixer) to obtain the mixture.

[0057] The mixture is fed into an extruder for plasticization (the temperatures of zones 1-4 of the extruder barrel are 178℃, 185℃, 182℃, and 158℃ respectively, the screw speed is 25r / min, and continuous extrusion is carried out). The mixture is then extruded into a mold for molding, and after cooling, PVC conduit is obtained.

[0058] Example 3

[0059] A PVC conduit comprises the following raw materials in parts by weight: 100 parts PVC resin, 12 parts flame retardant, 15 parts reinforcing filler, 1.2 parts paraffin (lubricant), and 1.0 part antioxidant 168 (antioxidant).

[0060] The flame retardant includes modified chitin (carrier) and aluminum hydroxide uniformly dispersed in the modified chitin. The modified chitin is obtained by sequentially deacetylifying chitin and modifying it with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (first silane coupling agent). The mass ratio of modified chitin to aluminum hydroxide is 1:0.7, the degree of deacetylation of modified chitin is 32%, and the average particle size of aluminum hydroxide is 7μm.

[0061] The preparation of flame retardants includes the following steps:

[0062] Chitosan was added to NaOH solution (35 wt%), and then NaBH4 was added (the mass ratio of chitosan to NaBH4 was 1:0.018). After ultrasonic dispersion for 1 h, deacetylation reaction was carried out at 93 °C for 3 h. The mixture was washed with deionized water until neutral and then freeze-dried to obtain deacetylated chitosan.

[0063] Deacetylated chitin was dispersed in water, and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (the mass ratio between chitin and the first silane coupling agent was 1:0.22) was added. The mixture was stirred for 2 hours to mix thoroughly, and then aluminum hydroxide was added. The mixture was stirred for 4 hours to mix thoroughly to obtain the flame retardant.

[0064] The reinforcing filler is obtained by mixing modified basalt fiber, vinyl silicone oil and silicone rubber in a mass ratio of 1:5:6. The modified basalt fiber is obtained by modifying the surface of basalt fiber with 3-methacryloyloxypropyltrimethoxysilane (second silane coupling agent) and butyl acrylate. The average length of the basalt fiber is 3.2 mm.

[0065] The preparation of reinforcing fillers includes the following steps:

[0066] Basalt fiber, 3-methacryloyloxypropyltrimethoxysilane (mass ratio of basalt fiber to the second silane coupling agent is 1:0.015) and butyl acrylate are added to vinyl silicone oil, stirred for 2 hours to mix, and then sand-milled (sand milling speed is 220 r / min, sand milling time is 21 hours) to obtain a mixed slurry.

[0067] The mixed slurry and silicone rubber were kneaded at 140°C for 10 hours (kneading was done by stirring at a speed of 100 r / min) to obtain the reinforcing filler.

[0068] The preparation method of the PVC conduit in Example 3 includes the following steps:

[0069] PVC resin, flame retardant and reinforcing filler are premixed (premixed for 10 min at 600 rpm in a high-speed mixer), and then paraffin wax and antioxidant 168 are added and mixed further (premixed for 20 min at 1000 rpm in a high-speed mixer) to obtain a mixture;

[0070] The mixture is fed into an extruder for plasticization (the temperatures of zones 1-4 of the extruder barrel are 178℃, 185℃, 182℃, and 158℃ respectively, the screw speed is 25r / min, and continuous extrusion is carried out). The mixture is then extruded into a mold for molding, and after cooling, PVC conduit is obtained.

[0071] Example 4

[0072] A PVC conduit comprises the following raw materials in parts by weight: 100 parts PVC resin, 14 parts flame retardant, 18 parts reinforcing filler, 1.5 parts polyethylene wax (lubricant), and 1.2 parts antioxidant 1076 (antioxidant).

[0073] The flame retardant includes modified chitin (carrier) and aluminum hydroxide uniformly dispersed in the modified chitin. The modified chitin is obtained by sequentially deacetylifying chitin and modifying it with N-phenyl-γ-aminopropyltrimethoxysilane (first silane coupling agent). The mass ratio of modified chitin to aluminum hydroxide is 1:0.85, the degree of deacetylation of the modified chitin is 35%, and the average particle size of aluminum hydroxide is 10 μm.

[0074] The preparation of flame retardants includes the following steps:

[0075] Chitosan was added to NaOH solution (35 wt%), and then NaBH4 was added (the mass ratio of chitosan to NaBH4 was 1:0.02). After ultrasonic dispersion for 1 h, deacetylation reaction was carried out at 96 °C (reaction for 4 h). The mixture was washed with deionized water until neutral and then freeze-dried to obtain deacetylated chitosan.

[0076] Deacetylated chitin was dispersed in water, and N-phenyl-γ-aminopropyltrimethoxysilane (the mass ratio of chitin to the first silane coupling agent was 1:0.3) was added. The mixture was stirred for 2 hours to mix evenly, and then aluminum hydroxide was added. The mixture was stirred for 4 hours to mix evenly to obtain the flame retardant.

[0077] The reinforcing filler is obtained by mixing modified basalt fiber, vinyl silicone oil and silicone rubber in a mass ratio of 1:6:7. The modified basalt fiber is obtained by modifying the surface of basalt fiber with methacryloyloxymethyltrimethoxysilane (second silane coupling agent) and butyl acrylate. The average length of the basalt fiber is 4.0 mm.

[0078] The preparation of reinforcing fillers includes the following steps:

[0079] Basalt fiber, methacryloyloxymethyltrimethoxysilane (mass ratio of basalt fiber to the second silane coupling agent is 1:0.02) and butyl acrylate are added to vinyl silicone oil, stirred for 2 hours to mix evenly, and then sand-milled (sand milling speed is 250 r / min, sand milling time is 24 hours) to obtain a mixed slurry.

[0080] The mixed slurry and silicone rubber were kneaded at 150°C for 12 hours (kneading was done by stirring at a speed of 100 r / min) to obtain the reinforcing filler.

[0081] The preparation method of the PVC conduit in Example 4 includes the following steps:

[0082] PVC resin, flame retardant and reinforcing filler are premixed (premixed for 10 min at 600 r / min in a high-speed mixer), and then polyethylene wax and antioxidant 1076 are added and mixed further (premixed for 20 min at 1000 r / min in a high-speed mixer) to obtain a mixture;

[0083] The mixture is fed into an extruder for plasticization (the temperatures of zones 1-4 of the extruder barrel are 178℃, 185℃, 182℃, and 158℃ respectively, the screw speed is 25r / min, and continuous extrusion is carried out). The mixture is then extruded into a mold for molding, and after cooling, PVC conduit is obtained.

[0084] Comparative Example 1

[0085] A PVC conduit, differing from Example 1 in that the flame retardant comprises 21 parts by weight. The rest is the same as in Example 1.

[0086] Comparative Example 2

[0087] A PVC conduit, differing from Example 1 in that the flame retardant comprises 3 parts by weight. The rest is the same as Example 1.

[0088] Comparative Example 3

[0089] A PVC conduit, differing from Example 1 in that the reinforcing filler comprises 25 parts by weight. The rest is the same as Example 1.

[0090] Comparative Example 4

[0091] A PVC conduit, differing from Example 1 in that the reinforcing filler comprises 4 parts by weight. The rest is the same as Example 1.

[0092] Comparative Example 5

[0093] A PVC conduit, differing from Example 1 in that the degree of deacetylation of the modified chitosan is 45%. Otherwise, it is the same as Example 1.

[0094] Comparative Example 6

[0095] A PVC conduit, differing from Example 1 in that the degree of deacetylation of the modified chitosan is 10%. The rest is the same as Example 1.

[0096] Comparative Example 7

[0097] A PVC conduit, differing from Example 1 in that the mass ratio of modified chitosan to aluminum hydroxide in the flame retardant is 1:1.2. Everything else is the same as in Example 1.

[0098] Comparative Example 8

[0099] A PVC conduit, differing from Example 1 in that the mass ratio of modified basalt fiber, vinyl silicone oil, and silicone rubber in the reinforcing filler is 1:2:5. The rest is the same as Example 1.

[0100] Comparative Example 9

[0101] A PVC conduit, differing from Example 1 in that the mass ratio of modified basalt fiber, vinyl silicone oil, and silicone rubber in the reinforcing filler is 1:7:8. The rest is the same as Example 1.

[0102] Comparative Example 10

[0103] A PVC conduit, differing from Example 1 in that the mass ratio of chitosan to γ-aminopropyltriethoxysilane is 1:0.05. The rest is the same as Example 1.

[0104] Comparative Example 11

[0105] A PVC conduit, differing from Example 1 in that the mass ratio of basalt fiber to γ-(methacryloyloxy)propyltrimethoxysilane is 1:0.03. The rest is the same as Example 1.

[0106] Effect test experiment

[0107] The products obtained in Example 1 and Comparative Examples 1-11 were subjected to performance tests, and the relevant test methods are as follows:

[0108] Tensile strength test: performed in accordance with ISO 527-1 and ISO 527-2;

[0109] Flame retardancy performance - Limiting oxygen index (LOI) test: conducted in accordance with ISO 4589-2;

[0110] The test results are shown in Table 1.

[0111] Table 1 Test Results

[0112]

[0113] Referring to the test results in Table 1, compared to Example 1, in Comparative Example 1, the excessive flame retardant exceeded the dispersion and carrying capacity of the PVC resin. The modified chitosan-aluminum hydroxide particles could not be uniformly dispersed and agglomerated, disrupting the continuity of the PVC molecular chains and resulting in a significant decrease in mechanical properties. Furthermore, the undispersed flame retardant could not further enhance the flame retardant effect. In Comparative Example 2, compared to Example 1, the total amount of flame retardant components was insufficient, failing to form a continuous flame retardant barrier in the PVC matrix, affecting flame retardant performance. Moreover, the reduced amount of the flame retardant carrier (modified chitosan) led to a decrease in its interfacial bonding points with the PVC resin, slightly affecting the overall mechanical stability. In Comparative Example 3, compared to Example 1, the excessive reinforcing filler could not be uniformly dispersed and agglomerated, forming "stress concentration points" in the PVC matrix, weakening the overall tensile strength. In Comparative Example 4, compared to Example 1, the total amount of reinforcing filler was insufficient, failing to construct an effective "mechanical support skeleton" in the PVC resin. Under stress, the lack of fiber stress transmission resulted in a sharp drop in tensile properties. Compared to Example 1, Comparative Example 5 showed an excessively high degree of deacetylation, resulting in an excess of amino groups on the surface of the modified chitosan. These amino groups exhibit polar repulsion with the chlorine atoms in the PVC molecular chain, disrupting the compatibility between the carrier and the PVC resin. This leads to uneven dispersion of the flame retardant, affecting its flame-retardant effect, and also reduces the interfacial bonding between the flame retardant carrier and the PVC resin, impacting mechanical properties. Compared to Example 1, Comparative Example 6 exhibited a low degree of deacetylation, resulting in excessively high crystallinity of the modified chitosan. The insufficient number of exposed hydroxyl groups in the molecular chain prevented the formation of a stable load bond with aluminum hydroxide, leading to uneven dispersion of aluminum hydroxide and a significant decrease in flame-retardant performance. Furthermore, the highly crystalline modified chitosan exhibited weaker interfacial bonding with the PVC resin, making it prone to peeling from the matrix under stress, further impacting mechanical properties. Compared to Example 1, in Comparative Example 7, aluminum hydroxide exceeded the loading capacity of the modified chitosan: the aluminum hydroxide particles not loaded on the carrier were directly exposed to the PVC resin, and agglomerated due to their high surface energy. This not only disrupted the continuity of the PVC molecular chains, leading to a decrease in mechanical properties, but also prevented the aluminum hydroxide from exerting its flame-retardant effect evenly, thus reducing the flame-retardant effect. In Comparative Example 8, compared to Example 1, the dispersion effect of vinyl silicone oil was insufficient. The basalt fibers agglomerated due to their high surface energy, forming "weak areas" in the PVC resin, which were prone to breakage under stress. In Comparative Example 9, compared to Example 1, the amount of vinyl silicone oil and silicone rubber in the reinforcing filler was excessive. These organic components themselves have low mechanical strength, reducing the overall material's support capacity. In Comparative Example 10, compared to Example 1, the amount of the first silane coupling agent (γ-aminopropyltriethoxysilane) was insufficient, resulting in insufficient "interfacial bridging" effect: it could not effectively connect the modified chitosan and the PVC resin, leading to uneven dispersion of the flame retardant in the PVC resin, a decrease in the flame-retardant effect, and weakening the interfacial bonding force between the flame retardant carrier and the PVC resin.Compared to Example 1, Comparative Example 11 is different because an excessive amount of the second silane coupling agent (γ-(methacryloyloxy)propyltrimethoxysilane) forms a "soft coating layer" on the surface of the basalt fiber, which makes the fiber unable to effectively bear stress when subjected to force, ultimately reducing the overall tensile properties.

[0114] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A PVC conduit, characterized in that, Including the following parts by weight of raw materials: 100 parts PVC resin, 8-14 parts flame retardant, 12-18 parts reinforcing filler, 0.6-1.5 parts lubricant, and 0.8-1.2 parts antioxidant; The flame retardant comprises a carrier and aluminum hydroxide uniformly dispersed in the carrier. The carrier is modified chitosan, which is obtained by sequentially deacetylifying chitosan and modifying it with a first silane coupling agent. The mass ratio of the modified chitosan to the aluminum hydroxide is 1:(0.5-0.85), the degree of deacetylation of the modified chitosan is 25%-35%, and the mass ratio of the chitosan to the first silane coupling agent is 1:(0.15-0.3). The reinforcing filler is obtained by mixing modified basalt fiber, vinyl silicone oil and silicone rubber. The modified basalt fiber is obtained by modifying the surface of basalt fiber with a second silane coupling agent and butyl acrylate. The mass ratio of the modified basalt fiber, the vinyl silicone oil and the silicone rubber is 1:(4-6):(5-7), and the mass ratio of the basalt fiber to the second silane coupling agent is 1:(0.01-0.02). The second silane coupling agent includes at least one of γ-(methacryloyloxy)propyltriethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, and methacryloyloxymethyltrimethoxysilane; The preparation of the reinforcing filler includes the following steps: The basalt fiber, the second silane coupling agent, and the butyl acrylate are added to the vinyl silicone oil, mixed well, and milled to obtain a mixed slurry. The mixed slurry is kneaded with the silicone rubber to obtain the reinforcing filler; The kneading is carried out at 130℃-150℃ for 8-12 hours.

2. The PVC conduit according to claim 1, characterized in that, The average particle size of the aluminum hydroxide is 3μm-10μm.

3. The PVC conduit according to claim 1, characterized in that, The average length of the basalt fibers is 2.5 mm to 4.0 mm.

4. The PVC conduit according to claim 1, characterized in that, The first silane coupling agent includes at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane.

5. The PVC conduit according to claim 1, characterized in that, The lubricant includes at least one of calcium stearate, glyceryl stearate, paraffin wax, and polyethylene wax.

6. The PVC conduit according to claim 1, characterized in that, The antioxidant includes at least one of antioxidant CA, antioxidant 1010, antioxidant 168, antioxidant 245, and antioxidant 1076.

7. A method for preparing a PVC conduit as described in any one of claims 1-6, characterized in that, Includes the following steps: The PVC resin, the flame retardant, the reinforcing filler, the lubricant, and the antioxidant are mixed to obtain a mixture; The mixture is plasticized and molded to obtain the PVC conduit.

8. The method for preparing PVC conduit according to claim 7, characterized in that, Before the mixing process, the PVC resin, the flame retardant, and the reinforcing filler are premixed.

9. The application of a PVC conduit as described in any one of claims 1-6 in industrial plant wiring.

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