Heat-conducting pert composite material suitable for floor heating pipes and preparation and application thereof

Abstract

The application discloses a heat-conducting PERT composite material suitable for a floor heating pipe, and a preparation method and application thereof. In terms of mass parts, raw material composition of the heat-conducting PERT composite material comprises: PERT resin 78-83 parts, a heat-conducting agent 10-20 parts, a toughening agent 2-5 parts, a compatilizer 2-5 parts, a main antioxidant 0.15-0.5 parts, an auxiliary antioxidant 0.15-0.5 parts, an ultradispersion agent 0.1-0.3 parts and an anti-fouling self-cleaning agent 0.3-0.7 parts; the heat-conducting agent is dendritic graphene and graphene microsheet with a mass ratio of (1.5-2):1, wherein the purity of the dendritic graphene is above 99 wt%, and the particle size is not more than 5 mu m; the average particle size of the graphene microsheet is 150-200 mu m.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a thermally conductive PERT composite material suitable for use in underfloor heating pipes, its preparation method, and its application. Background Technology

[0002] Currently, one of the better strategies to further improve the radiant heat dissipation of PERT underfloor heating pipes is to use PERT plastic with high thermal conductivity after being filled with thermally conductive agents. To achieve good thermal conductivity, a large amount of thermally conductive agent is usually filled into the base material. This leads to a decrease in the mechanical properties of the PERT composite material, making the extruded PERT pipes less resistant to aging and unable to pass prolonged hydrostatic tests. Furthermore, the filling with thermally conductive fillers often makes the inner surface of the extruded PERT pipes rougher; a rough inner surface can lead to scaling, reducing the heat dissipation of the thermally conductive PERT material and severely impacting heating performance. To improve the roughness of the internal surface of the thermally conductive PERT pipe and achieve scale inhibition, a smooth, scale-resistant PERT plastic is often used for the innermost layer through a multi-layer co-extrusion process. While this partially solves the problem, it significantly increases production costs, which is very detrimental to the widespread use of thermally conductive PERT materials.

[0003] The following existing technologies were found through a search: Patent specification CN121246377A discloses a highly dispersed graphene-based thermally conductive, scale-resistant, and oxygen-barrier PE-RT underfloor heating pipe and its preparation method. This thermally conductive PERT underfloor heating pipe is formed by double-layer co-extrusion, including a thermally conductive outer layer and a thermally conductive and scale-resistant inner layer. Although the addition of highly dispersed graphene material significantly improves the thermal conductivity of the pipe material and helps reduce the roughness of the inner surface, the double-layer co-extrusion method increases production costs. Furthermore, this patent only discloses short-term hydrostatic pressure testing results and does not delve into long-term hydrostatic pressure resistance. Similarly, patent specification CN119261303A discloses a high thermal conductivity PERT underfloor heating pipe and its preparation method, but does not delve into long-term hydrostatic pressure resistance.

[0004] Patent specification CN120209435A discloses a PERT underfloor heating pipe material and its preparation method. This thermally conductive PERT underfloor heating pipe is formed by double-layer co-extrusion, including a thermally conductive outer layer and an antibacterial and anti-scaling inner layer. Although the patent specification indicates that it can pass long-term hydrostatic pressure resistance tests, the pressure that the pipe material withstood in the test was relatively low, only 0.79 MPa.

[0005] Patent specification CN115139572A discloses a thermally conductive PERT underfloor heating pipe and its manufacturing method. This thermally conductive PERT underfloor heating pipe is formed by double-layer co-extrusion, including a thermally conductive outer layer and a thermally conductive and scale-resistant inner layer. However, the cost of this thermally conductive PERT underfloor heating pipe is relatively high. Besides the double-layer extrusion process, another reason is that the thermally conductive and scale-resistant inner layer uses expensive quaternary ammonium boron nitride as a raw material. Furthermore, because quaternary ammonium boron nitride has a significant impact on the material's toughness, a double-layer structure is also necessary.

[0006] Patent specification CN117776169A discloses a graphene-based thermally conductive PERT underfloor heating pipe and its preparation method. This thermally conductive PERT underfloor heating pipe is produced by single-layer extrusion, simplifying the process and reducing production costs. However, the extruded pipe requires a wall thickness of ≥3mm to pass the hydrostatic test, suggesting that the mechanical properties and aging resistance of PERT material are relatively average. Furthermore, although the pipe passed the long-term hydrostatic test, the specific pressure under which the test was conducted was not specified. Summary of the Invention

[0007] To address the aforementioned technical problems and shortcomings in the field, this invention provides a thermally conductive PERT composite material suitable for underfloor heating pipes, its preparation method, and its application.

[0008] The specific technical solution is as follows: In a first aspect, the present invention provides a thermally conductive PERT composite material suitable for use in underfloor heating pipes, comprising, by weight: 78-83 parts (e.g., 80 parts, etc.) of PERT resin, 10-20 parts (e.g., 14 parts, etc.) of thermally conductive agent, 2-5 parts (e.g., 3 parts, etc.) of toughening agent, 2-5 parts (e.g., 3 parts, etc.) of compatibilizer, 0.15-0.5 parts (e.g., 0.2 parts, 0.4 parts, etc.) of primary antioxidant, 0.15-0.5 parts (e.g., 0.2 parts, 0.4 parts, etc.) of secondary antioxidant, 0.1-0.3 parts (e.g., 0.2 parts, etc.) of superdispersant, and 0.3-0.7 parts (e.g., 0.5 parts, etc.) of anti-scaling and self-cleaning agent. The thermal conductive agent is dendritic graphene and graphene microflakes in a mass ratio of (1.5~2):1 (e.g., 1.8:1, etc.), wherein: the purity of the dendritic graphene is above 99wt% and the particle size does not exceed 5μm; the average particle size of the graphene microflakes is 150~200μm (e.g., 170μm, etc.).

[0009] The inventors discovered that combining two types of graphene with specific morphologies and particle sizes at the aforementioned specific mass ratio can balance the thermal conductivity and mechanical properties of thermally conductive PERT composites. Graphene microflakes with an average particle size of 150-200 μm significantly improve the thermal conductivity of thermally conductive PERT composites, but substantially weaken their mechanical properties. Dendritic graphene with a particle size not exceeding 5 μm and a purity of over 99 wt% provides a weaker boost to the thermal conductivity of thermally conductive PERT composites than graphene microflakes with an average particle size of 150-200 μm, but it can better maintain the mechanical properties of thermally conductive PERT composites. This invention combines these two types of graphene at a specific mass ratio, enabling thermally conductive PERT composites to possess both excellent thermal conductivity and mechanical properties.

[0010] Further research by the inventors revealed that the purity of dendritic graphene with a particle size not exceeding 5 μm significantly affects the resistance to damp heat aging and long-term hydrostatic pressure resistance of thermally conductive PERT composite materials and their molded tubes. Increasing the purity of dendritic graphene with a particle size not exceeding 5 μm to over 99 wt% can significantly improve the resistance to damp heat aging and long-term hydrostatic pressure resistance of thermally conductive PERT composite materials and their molded tubes.

[0011] The inventors also discovered that the inner surface roughness of pipes extruded from thermally conductive PERT composite materials using graphene with different morphologies, particle sizes, and purities varies: dendritic graphene with a particle size not exceeding 5 μm and a purity of over 99 wt% can further reduce the inner surface roughness of the formed pipe compared to graphene microflakes with an average particle size of 150~200 μm; the higher the purity of dendritic graphene with a particle size not exceeding 5 μm, the lower the inner surface roughness of the formed pipe.

[0012] Furthermore, the specific model of the dendritic graphene with a particle size not exceeding 5μm and a purity of 99wt% or higher can be TT-99, which can be purchased from Hunan Runxi Technology Co., Ltd.

[0013] Furthermore, the specific model of the graphene microplate with an average particle size of 150~200μm can be DRM-P003C (average particle size 170μm), which can be purchased from Xiamen Kaina Graphene Technology Co., Ltd.

[0014] In some preferred embodiments, the melt index of the PERT resin at 190°C and 5kg is (1.5~1.7) g / 10min, for example 1.6 g / 10min, and the specific model can be DQDN3711 (melt index of 1.6 g / 10min at 190°C and 5kg).

[0015] In some preferred embodiments, the toughening agent is a polyolefin elastomer (POE). The compatibilizer is maleic anhydride-grafted polyolefin elastomer.

[0016] Experiments have shown that when using polyolefin elastomers as toughening agents, the combined use of maleic anhydride-grafted polyolefin elastomers as compatibilizers can not only further improve the mechanical properties and short-term hydrostatic resistance of thermally conductive PERT composite materials, but also enhance their thermal conductivity. Furthermore, it can reduce the surface roughness of the inner surface of the extruded pipes made from thermally conductive PERT composite materials, thus alleviating scaling on the inner wall of the pipes.

[0017] Furthermore, the specific type of the toughening agent polyolefin elastomer can be POE 8150.

[0018] Furthermore, the compatibilizer, maleic anhydride-grafted polyolefin elastomer, can be specifically designated as W1C-D and is available from KOAS Chemical Co., Ltd.

[0019] In some preferred embodiments, the primary antioxidant is DEOX S80; The co-antioxidant is 608T.

[0020] Experiments have shown that, compared to other combinations of primary and secondary antioxidants, such as primary antioxidant 1010 and secondary antioxidant 168, the combination of primary antioxidant DEOX S80 and secondary antioxidant 608T used in this invention can further improve the resistance to damp heat aging and long-term hydrostatic pressure resistance of thermally conductive PERT composite materials and their molded pipes.

[0021] In some preferred embodiments, the raw material composition further includes a lubricant. Further, the lubricant in the raw material composition may be 0.1 to 0.3 parts by weight (e.g., 0.15 parts by weight).

[0022] In some preferred embodiments, the lubricant includes ethylene bis-stearamide.

[0023] In some preferred embodiments, the superdispersant includes XS-HD-602, which is available from Zhejiang Xusen Non-halogenated Smoke Retardant Flame Retardant Co., Ltd.

[0024] In some preferred embodiments, anti-scaling self-cleaning agents include Miclean. ® KC3210 is available from Changzhou Tongzhou New Material Technology Co., Ltd.

[0025] In a second aspect, the present invention provides a method for preparing the thermally conductive PERT composite material described in the first aspect, comprising: mixing the raw materials and then melt-extruding them to obtain the thermally conductive PERT composite material.

[0026] In some preferred embodiments, the extrusion temperature is 200~230°C and the extrusion screw speed is 300~400 rpm (e.g., 350 rpm).

[0027] Thirdly, the present invention provides the application of the thermally conductive PERT composite material described in the first aspect in the manufacture of underfloor heating pipes.

[0028] In this invention, the addition of a specific thermally conductive agent enables the PERT composite material to possess both excellent heat dissipation and mechanical properties. By introducing maleic anhydride-grafted polyolefin elastomer to compound POE, the strength and thermal conductivity of the PERT composite material are improved, and it also exhibits good toughness and scale inhibition capabilities. More importantly, through the synergistic effect of specific graphene with superdispersants and anti-scale self-cleaning agents, the pipes formed by extrusion of the thermally conductive PERT material have a smaller inner wall surface roughness, thereby exhibiting better scale inhibition. Furthermore, by selecting suitable high-temperature resistant compound antioxidants that are more suitable for humid heat conditions, the PERT composite material has passed long-term hydrostatic pressure resistance tests.

[0029] Compared with the prior art, the beneficial effects of this invention are as follows: 1. By using a combination of toughening agent POE and maleic anhydride-grafted polyolefin elastomer, the mechanical properties of PERT pipe material, such as toughness, short-term hydrostatic resistance, thermal conductivity, and scale inhibition, are greatly improved, while the inner surface roughness is significantly reduced.

[0030] 2. By using a combination of high-melting-point, high-temperature resistant antioxidants DEOX S80 and 608T, the aging resistance of PERT pipe material is greatly improved, thus enabling the extruded PERT pipe to pass long-term hydrostatic pressure tests.

[0031] 3. Through the synergistic effect of suitable graphene materials, super-dispersants, and anti-scaling self-cleaning agents, the roughness of the inner surface of the extruded PERT pipe is reduced, thereby achieving better anti-scaling performance. Attached Figure Description

[0032] Figure 1 The figures show the damp heat test results of the tensile specimens of the composite materials injection molded in Examples 7 and 8. The damp heat aging test conditions were a temperature of 85°C and a relative humidity of 85%. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and 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. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0034] Examples 1 to 8: According to Table 1 (parts by mass), each raw material was taken and mixed evenly in a high-speed mixer. The mixture was then melt-extruded through an extruder at a temperature of 200-230℃ and a screw speed of 350 rpm. After cooling, drying, and pelletizing, the composite material products of each embodiment were obtained. The graphene material TT-90 in Table 1 was also purchased from Hunan Runxi Technology Co., Ltd. The only difference between TT-90 and TT-99 was their purity; both were dendritic graphene with a particle size not exceeding 5 μm. The purity of TT-90 was 90 wt%, while the purity of TT-99 was above 99 wt%.

[0035] Table 1 Table 2 shows the properties of the composite materials in each embodiment.

[0036] Table 2 The test results of Examples 1, 2, and 3 show that graphene materials from different manufacturers have varying effects on the material's performance. Graphene microflakes DRM-003C significantly degrade the material's performance; only the addition of an appropriate amount of graphene material TT-99 can improve the overall mechanical properties of the PERT composite material. The test results of Examples 3 and 4 show that maleic anhydride-grafted polyolefin elastomers improve the compatibility between the resin and the graphene filler, thereby enhancing the material's mechanical and thermal conductivity. A comparison of Examples 4 and 5 shows that the addition of a superdispersant further facilitates the dispersion of graphene fillers in the PERT matrix, thus improving the overall mechanical properties of the PERT composite material.

[0037] Table 3 shows the test results of the pipes produced by extrusion molding of composite materials in each embodiment. The extruded parts are single-layer thermally conductive PERT underfloor heating pipes with a thickness of 2 mm.

[0038] Table 3 The test results of Examples 1, 2, and 3 show that graphene materials from different manufacturers have varying effects on the inner surface roughness of the corresponding extruded pipes, with TT-99 material being more effective in reducing the inner surface roughness. Furthermore, Examples 7 and 8 demonstrate that, for the same type of material, increasing the purity of the graphene material also helps reduce the inner surface roughness of the pipe. The test results of Examples 3-6 show that the addition of maleic anhydride-grafted polyolefin elastomer, superdispersant, and anti-scaling self-cleaning agent helps improve the inner surface roughness of the extruded pipe, ultimately contributing to improved internal wall fouling.

[0039] As can be seen from the test results of Examples 1-4, the overall mechanical properties of the material are improved, which helps the extruded pipes pass the short-term hydrostatic test.

[0040] Based on the test results of Examples 6 and 7, the combined use of high-temperature resistant primary antioxidant and secondary antioxidant helps 2mm thick extruded pipes pass long-term hydrostatic resistance tests.

[0041] Furthermore, by comparing Examples 7 and 8, it is evident that the use of high-purity graphene materials is necessary for extruded pipes to pass long-term hydrostatic tests.

[0042] Figure 1 The damp heat test results of the tensile specimens injection-molded from the composite materials of Examples 7 and 8 are presented. The elongation at break - fading rate (%) = (initial elongation at break - elongation at break after corresponding damp heat aging time) / initial elongation at break × 100%. It can be seen that although the mechanical properties of the two formulations are not significantly different, the tensile specimens of the two materials exhibit different resistance to damp heat aging due to the use of dendritic graphene of different purities. This is the main reason why the pipe molded from the composite material of Example 8 failed the long-term hydrostatic test.

[0043] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A thermally conductive PERT composite material suitable for use in underfloor heating pipes, characterized in that, By weight, the raw material composition includes: 78-83 parts PERT resin, 10-20 parts thermal conductive agent, 2-5 parts toughening agent, 2-5 parts compatibilizer, 0.15-0.5 parts main antioxidant, 0.15-0.5 parts auxiliary antioxidant, 0.1-0.3 parts superdispersant, and 0.3-0.7 parts anti-scaling and self-cleaning agent; The thermal conductive agent is dendritic graphene and graphene microflakes in a mass ratio of (1.5~2):1, wherein: the purity of the dendritic graphene is above 99wt% and the particle size does not exceed 5μm; the average particle size of the graphene microflakes is 150~200μm.

2. The thermally conductive PERT composite material according to claim 1, characterized in that, The melt index of PERT resin at 190℃ and 5kg is (1.5~1.7)g / 10min.

3. The thermally conductive PERT composite material according to claim 1, characterized in that, The toughening agent is a polyolefin elastomer; The compatibilizer is maleic anhydride-grafted polyolefin elastomer.

4. The thermally conductive PERT composite material according to claim 1, characterized in that, The main antioxidant is DEOX S80; The co-antioxidant is 608T.

5. The thermally conductive PERT composite material according to claim 1, characterized in that, The raw material composition also includes a lubricant; In the raw material composition, the lubricant is 0.1~0.3 parts by weight; Lubricants include ethylene bis-stearamide.

6. The thermally conductive PERT composite material according to claim 1, characterized in that, Superdispersants include XS-HD-602.

7. The thermally conductive PERT composite material according to claim 1, characterized in that, Anti-scaling self-cleaning agents include Miclean ® KC3210.

8. The method for preparing the thermally conductive PERT composite material according to any one of claims 1 to 7, characterized in that, include: The thermally conductive PERT composite material is obtained by melting and extruding the raw materials after mixing.

9. The preparation method according to claim 8, characterized in that, The extrusion temperature is 200~230℃, and the extrusion screw speed is 300~400 rpm.

10. The application of the thermally conductive PERT composite material according to any one of claims 1 to 7 in the manufacture of underfloor heating pipes.

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