Polyolefin composite floor heating pipe with high impact resistance and high thermal conductivity and preparation method thereof

Abstract

The invention provides a high-impact-resistance and high-thermal-conductivity polyolefin composite floor heating pipe and a preparation method thereof. The floor heating pipe is prepared from the following raw materials: 100 parts of polyolefin, 5 to 15 parts of thermal conductive filler, 10 to 40 parts of elastomer, 1 to 1.5 parts of dispersing agent and 0.5 to 1.5 parts of lubricating agent. The heat-conducting filler is adopted for surface modification, meanwhile, an elastomer phase with good compatibility with polyolefin is introduced, it is guaranteed that the heat-conducting filler is selectively and evenly dispersed on a two-phase interface, and the percolation threshold value is effectively reduced. The heat conduction filler constructs a three-dimensional, efficient and stable heat conduction network, and rapid transportation of heat is achieved. And the copolymer elastomer is used as a stress concentration point to initiate crazing and a shear band, so that a large amount of impact energy is absorbed, and the impact resistance of the polyolefin composite pipe is improved.

Description

Technical Field

[0001] This invention belongs to the field of underfloor heating pipe technology. Background Technology

[0002] Underfloor heating is commonly used for home heating. It involves burying hot water pipes under the floor to heat the entire floor and distribute the heat evenly throughout the room via radiation. As the most critical circulating heat dissipation terminal in an underfloor heating system, the pipes need to possess excellent mechanical properties and rapid heat dissipation. Sufficient mechanical properties ensure the safe and stable operation of the underfloor heating system throughout the building's lifespan, minimizing maintenance and repair costs. Rapid heat dissipation reduces pipe density, lowering initial investment costs and reducing long-term energy consumption. Currently, most underfloor heating pipes on the market are made of heat-resistant polyethylene (PERT), cross-linked polyethylene (XLPE), and random copolymer polypropylene (PPR). Due to the inherent characteristics of polymers, polymer pipes have poor thermal conductivity (only 0.1-0.3 W / m·K), insufficient mechanical strength, and poor toughness, which to some extent limits their practical application in heat exchange / dissipation.

[0003] Currently, adding thermally conductive fillers such as graphite, boron nitride, graphene, carbon black, silicon carbide, and carbon nanotubes to polymers is a development trend in the engineering of plastic pipes. Some fillers (such as carbon nanotubes and graphene) can significantly improve the strength, modulus, and hardness of composite materials while enhancing thermal conductivity. They can act as a reinforcing "skeleton," reducing thermal expansion and deformation of the material under heat, suppressing creep at long-term high temperatures, and enabling parts to maintain a more stable shape and size under temperature changes. However, it is important to note that excessive addition of fillers can lead to increased brittleness. Therefore, there is an urgent need to develop a method that not only improves the thermal conductivity, mechanical strength, and hardness of polyolefin composites by filling them with thermally conductive fillers, but also toughens the polyolefin, thereby producing plastic underfloor heating pipes with excellent heat exchange / dissipation and good mechanical properties. Summary of the Invention

[0004] This invention provides a high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe, achieving the following objective: to prepare an underfloor heating pipe with polyolefin composite as the main material, which has both high thermal conductivity and high impact strength.

[0005] The technical solution adopted in this invention is as follows:

[0006] A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe is prepared from the following components in parts by weight: 100 parts polyolefin, 5-15 parts thermally conductive filler, 10-40 parts elastomer, 1-1.5 parts dispersant, and 0.5-1.5 parts lubricant.

[0007] The polyolefin is one of high-density polyethylene and atactic polypropylene.

[0008] The thermally conductive filler is one of multi-walled carbon nanotubes, graphene, and silicon carbide.

[0009] The elastomer is one of propylene-ethylene copolymer and ethylene-octene copolymer.

[0010] The dispersant is at least one of 3-aminopropyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, methyltrimethoxysilane, and octyltriethoxysilane.

[0011] The lubricant is at least one of stearic acid, zinc stearate, calcium stearate, polyethylene wax, oxidized polyethylene wax, and polypropylene wax.

[0012] A method for preparing high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipes includes the following steps:

[0013] Thermally conductive fillers and dispersants are added to polyolefin resin and mixed and dispersed in an internal mixer at a temperature of 180-220℃ for 30 minutes to obtain a high thermal conductivity polyolefin composite material. The high thermal conductivity polyolefin composite material and elastomer are fed into a twin-screw extruder at a rate of 8 kg / h. The twin-screw extruder has six temperature control sections: section 1 (80-150℃), section 2 (140-170℃), section 3 (150-210℃), section 4 (160-221℃), and section 5 (170-220℃). The die temperature is 180-220℃, and the screw speed is 120-145 rpm. After extruding the pipe through the die, it is air-cooled to room temperature to obtain the high impact resistance and high thermal conductivity polyolefin composite underfloor heating pipe.

[0014] Beneficial effects of the present invention

[0015] (1) Thermally conductive fillers, at relatively low addition levels (1-15 wt%), can increase the thermal conductivity of composite materials several times. Multi-walled carbon nanotubes themselves have extremely high axial thermal conductivity (theoretical value exceeding 3000 W / (m·K)). In composite materials, uniformly dispersed multi-walled carbon nanotubes can act like "thermal conductors" or "highways," providing ultra-high-speed longitudinal conduction paths for phonons (the main heat carriers). Graphene is the material with the best thermal conductivity (theoretical value up to 5000 W / (m·K) at room temperature). Its two-dimensional sheet structure provides enormous planar thermal conductivity. Graphene sheets can overlap in the matrix to form a denser and more efficient two-dimensional / three-dimensional thermally conductive network, allowing heat to be rapidly transferred in the plane and then conducted from one sheet to another. Silicon carbide is an excellent thermal conductor (thermal conductivity of about 100-300 W / (m·K)). Its thermal conduction mechanism is achieved by filling a large number of silicon carbide particles, reducing the volume fraction of the polymer matrix, and allowing heat to be transferred between silicon carbide particles through point-to-point contact.

[0016] (2) The addition and uniform dispersion of thermally conductive fillers not only improve the thermal conductivity of polyolefin composite pipes but also enhance their mechanical properties. Multi-walled carbon nanotubes possess a one-dimensional fiber reinforcement effect, exhibiting extremely high axial tensile strength and modulus, functioning similarly to microscopic "steel bars." When there is a good interfacial bond with the matrix, stress can be effectively transferred from the polymer matrix to the high-strength multi-walled carbon nanotubes. This effectively improves the elastic modulus (stiffness) and tensile strength of the composite material. Graphene possesses a two-dimensional ultra-strong interfacial reinforcement effect. Graphene's ultra-high specific surface area results in a large contact area with the polymer, leading to extremely high interfacial stress transfer efficiency. Its two-dimensional structure can more effectively hinder the movement of polymer molecular chains and prevent the propagation of microcracks, significantly improving the modulus and strength of polyolefin composites. Silicon carbide has a rigid particle reinforcement mechanism; it consists of hard and brittle ceramic particles that primarily act as rigid support points, maximally restricting the movement of polymer molecular chains. This can significantly improve the stiffness and hardness of the composite material.

[0017] (3) Polyolefins and elastomers form a sea-island structure. Due to thermodynamic driving forces such as surface energy and interfacial tension, conductive fillers preferentially distribute at the interface between the two phases, reducing the percolation threshold of the conductive fillers. The thermally conductive fillers selectively dispersed at the interface between the two phases act as "pinning" agents, enhancing the interfacial adhesion between the two phases. This effectively promotes stress transfer, prevents the generation and propagation of microcracks, and thus simultaneously improves the strength and toughness of the material. Elastomers are the "soft phase" and toughening phase in composite materials. After being reinforced by fillers, the modulus of the elastomer phase itself increases, enabling the blend to more effectively transfer and disperse stress when subjected to force. When subjected to impact, elastomer particles can induce crazes and shear bands, yet they are not easily destroyed, thus absorbing more energy. This can significantly improve the modulus and strength of the material while enhancing toughness, achieving a balance between rigidity and toughness. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of Example 3. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments, but these embodiments are not to be construed as limiting the scope of protection of the present invention in any sense.

[0020] Example 1

[0021] A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe and its preparation method are disclosed. The pipe is prepared from the following raw materials in parts by weight: 100 parts polyolefin, 15 parts thermally conductive filler, 40 parts elastomer, 1.5 parts dispersant, and 0.5 parts lubricant.

[0022] In this embodiment, the polyolefin is random polypropylene; the thermally conductive filler is multi-walled carbon nanotubes; the copolymer elastomer is propylene-ethylene copolymer; the dispersant is aminosilane (KH-550); and the lubricant in this embodiment is a mixture of zinc stearate and polyethylene wax in a mass ratio of 1:1.

[0023] Thermally conductive fillers and dispersants were added to a polyolefin resin and mixed and dispersed in an internal mixer at 190°C for 30 minutes to obtain a high thermal conductivity polyolefin composite material. The high thermal conductivity polyolefin composite material and elastomer were fed into a twin-screw extruder at a rate of 8 kg / h. The twin-screw extruder had six temperature-controlled sections: 100°C for the first section, 140°C for the second, 170°C for the third, 190°C for the fourth, and 200°C for the fifth. The die temperature was 200°C, and the screw speed was 120–145 rpm. After extruding the pipe through the die, it was air-cooled to room temperature to obtain the high impact resistance and high thermal conductivity polyolefin composite underfloor heating pipe. The pipe diameter was 12 mm and the wall thickness was 1.5 mm.

[0024] Example 2

[0025] A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe and its preparation method are disclosed, which are prepared from the following raw materials in parts by weight: 100 parts polyolefin, 5 parts thermally conductive filler, 10 parts elastomer, 1 part dispersant, and 1.5 parts lubricant.

[0026] In this embodiment, the polyolefin is random polypropylene; the thermally conductive filler is multi-walled carbon nanotubes; the copolymer elastomer is propylene-ethylene copolymer; the dispersant is aminosilane (KH-550); and the lubricant in this embodiment is a mixture of zinc stearate and polyethylene wax in a mass ratio of 1:1.

[0027] Thermally conductive fillers and dispersants were added to a polyolefin resin and mixed and dispersed in an internal mixer at 190°C for 30 minutes to obtain a high thermal conductivity polyolefin composite material. The high thermal conductivity polyolefin composite material and elastomer were fed into a twin-screw extruder at a rate of 8 kg / h. The twin-screw extruder had six temperature-controlled sections: 100°C for the first section, 140°C for the second, 170°C for the third, 190°C for the fourth, and 200°C for the fifth. The die temperature was 200°C, and the screw speed was 120–145 rpm. After extruding the pipe through the die, it was air-cooled to room temperature to obtain the high impact resistance and high thermal conductivity polyolefin composite underfloor heating pipe. The pipe diameter was 12 mm and the wall thickness was 1.5 mm.

[0028] Example 3

[0029] A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe and its preparation method are disclosed, which are prepared from the following raw materials in parts by weight: 100 parts polyolefin, 10 parts thermally conductive filler, 20 parts elastomer, 1.2 parts dispersant, and 1 part lubricant.

[0030] In this embodiment, the polyolefin is random polypropylene; the thermally conductive filler is multi-walled carbon nanotubes; the copolymer elastomer is propylene-ethylene copolymer; the dispersant is aminosilane (KH-550); and the lubricant in this embodiment is a mixture of zinc stearate and polyethylene wax in a mass ratio of 1:1.

[0031] Thermally conductive fillers and dispersants were added to a polyolefin resin and mixed and dispersed in an internal mixer at 190°C for 30 minutes to obtain a high thermal conductivity polyolefin composite material. The high thermal conductivity polyolefin composite material and elastomer were fed into a twin-screw extruder at a rate of 8 kg / h. The twin-screw extruder had six temperature-controlled sections: 100°C for the first section, 140°C for the second, 170°C for the third, 190°C for the fourth, and 200°C for the fifth. The die temperature was 200°C, and the screw speed was 120–145 rpm. After extruding the pipe through the die, it was air-cooled to room temperature to obtain the high impact resistance and high thermal conductivity polyolefin composite underfloor heating pipe. The pipe diameter was 12 mm and the wall thickness was 1.5 mm.

[0032] Example 4

[0033] A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe and its preparation method are disclosed. The pipe is prepared from the following raw materials in parts by weight: 100 parts polyolefin, 5 parts thermally conductive filler, 40 parts elastomer, 1.5 parts dispersant, and 1 part lubricant.

[0034] In this embodiment, the polyolefin is random polypropylene; the thermally conductive filler is multi-walled carbon nanotubes; the copolymer elastomer is propylene-ethylene copolymer; the dispersant is aminosilane (KH-550); and the lubricant in this embodiment is a mixture of zinc stearate and polyethylene wax in a mass ratio of 1:1.

[0035] Thermally conductive fillers and dispersants were added to a polyolefin resin and mixed and dispersed in an internal mixer at 190°C for 30 minutes to obtain a high thermal conductivity polyolefin composite material. The high thermal conductivity polyolefin composite material and elastomer were fed into a twin-screw extruder at a rate of 8 kg / h. The twin-screw extruder had six temperature control sections: 100°C for the first section, 140°C for the second, 170°C for the third, 190°C for the fourth, and 200°C for the fifth. The die temperature was 200°C, and the screw speed was 120–145 rpm. After extruding the pipe through the die, it was air-cooled to room temperature to obtain the high impact resistance and high thermal conductivity polyolefin composite underfloor heating pipe. The pipe diameter was 20 mm and the wall thickness was 1.5 mm.

[0036] Comparative Example 1

[0037] A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe and its preparation method are disclosed. The specific raw materials and addition amounts are the same as in Example 1, except that no copolymer elastomer is added.

[0038] Comparative Example 2

[0039] A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe and its preparation method are disclosed. The specific raw materials and addition amounts are the same as in Example 1, except that no thermally conductive filler is added.

[0040] Comparative Example 3

[0041] A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe and its preparation method are disclosed. The specific raw materials and addition amounts are the same as in Example 1, except that no dispersant is added.

[0042] Performance testing

[0043] The pipes obtained in Examples 1, 2, 3, and 4 and Comparative Examples 1, 2, and 3 were tested for the following performance indicators:

[0044] 1. Melt flow rate of pipe-specific materials: Tested according to GB / T 3682.1-2018 standard. Examples and comparative examples.

[0045] 2. Static hydraulic resistance: Test examples and comparative examples are provided in accordance with GB / T 6111-2018 "Determination of internal pressure resistance of thermoplastic piping systems for fluid transport".

[0046] 3. Thermal conductivity: Sample sheets of 100cm×100cm×10mm were prepared and tested according to GB / T 10297-2015 standard for both examples and comparative examples.

[0047] 4. Impact strength: The impact strength of the notched cantilever beams in the examples and comparative examples was tested according to GB / T 1843-2008 standard.

[0048] The test results are shown in Table 1.

[0049]

[0050] As shown in Table 1, the melt flow rate, thermal conductivity, and impact strength of Example 1 are all greater than those of Comparative Example 1. In this example, the elastomer phase and the polyolefin phase form a uniform dispersed phase structure. The elastomer plays a toughening role. After being reinforced by the filler, the modulus of the elastomer phase itself increases, allowing the blend to more effectively transfer and disperse stress under load. When subjected to impact, the elastomer particles can induce crazes and shear bands, yet they are not easily destroyed, thus absorbing more energy. Simultaneously, the conductive filler preferentially distributes at the interface between the two phases, reducing the percolation threshold of the conductive filler and increasing the thermal conductivity. The melt flow rate, thermal conductivity, and impact strength of Example 1 are higher than those of Comparative Example 2 because the conductive filler in this example not only improves the thermal conductivity of the composite pipe but also strengthens the melt. The melt flow rate, thermal conductivity, and impact strength of Example 1 are higher than those of Comparative Example 3 because the dispersant in this example allows the conductive filler in the composite pipe to be more uniformly dispersed, forming a more effective thermally conductive network structure. The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art can make various corresponding changes according to the present invention, but these corresponding changes should all fall within the scope of protection of the present invention.

Claims

1. A high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe, characterized in that: 100 parts polyolefin, 5-15 parts thermally conductive filler, 10-40 parts elastomer, 1-1.5 parts dispersant, and 0.5-1.5 parts lubricant.

2. The high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe according to claim 1, characterized in that... The preparation method is as follows: Thermally conductive filler is added to polyolefin resin, and a dispersant is added for mixing and dispersion in a mixer at a temperature of 180-220℃ for 30 minutes to obtain a high thermal conductivity polyolefin composite material. The high thermal conductivity polyolefin composite material and elastomer are fed into a twin-screw extruder at a rate of 8 kg / h. The twin-screw extruder has six temperature control sections: the first section is 80-150℃, the second section is 140-170℃, the third section is 150-210℃, the fourth section is 160-221℃, and the fifth section is 170-220℃. The die temperature is 180-220℃, and the screw speed is 120-145 rpm. After extruding the pipe through the die, it is air-cooled to room temperature to obtain the high impact resistance and high thermal conductivity polyolefin composite underfloor heating pipe.

3. The high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe according to claim 1, wherein, Polyolefins are one of high-density polyethylene and atactic polypropylene.

4. The high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe according to claim 1, wherein, The thermally conductive filler is one of multi-walled carbon nanotubes, graphene, or silicon carbide.

5. The high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe according to claim 1, wherein, The copolymer elastomer is one of propylene-ethylene copolymer and ethylene-octene copolymer.

6. The high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe according to claim 1, wherein, The dispersant is one or more of the following: 3-aminopropyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, methyltrimethoxysilane, and octyltriethoxysilane.

7. The high-impact, high-thermal-conductivity polyolefin composite underfloor heating pipe according to claim 1, wherein, The lubricant is one or more of the following: stearic acid, zinc stearate, calcium stearate, polyethylene wax, oxidized polyethylene wax, and polypropylene wax.

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