Method for preparing sensing belt and composite pipe

Abstract

The invention provides a method for preparing a sensing belt and a composite pipe. The method for preparing the sensing belt comprises the following steps: 1) mixing the conductive filler with a first thermosetting resin or thermoplastic resin solution to obtain a dispersion liquid; 2) adding a curing agent into the dispersion liquid to obtain a coating material; and 3) coating the surface of the fiber with the coating material to obtain the force-sensitive sensing belt or the temperature-sensitive sensing belt.

Description

Technical Field

[0001] The invention provides a method for preparing a sensor belt, in particular a method for preparing a composite tube coated with a force-sensitive sensor belt and a temperature-sensitive sensor belt. Background Art

[0002] Pipelines play a vital role in the transportation of gases and liquids and are essential for ensuring the growth of productivity. However, most oil and gas pipelines operate in harsh climates. Years of temperature fluctuations can cause irreversible fatigue damage to pipeline materials. Excessive internal pressure can lead to ruptures, resulting in significant resource losses and severe environmental pollution. Routine manual monitoring and maintenance of pipelines is labor-intensive and incapable of timely and accurate detection of pipeline problems. Therefore, intelligent pipeline monitoring is becoming increasingly important.

[0003] Smart pipes are an important branch of a wide variety of pipelines. Their principle is to lay monitoring lines or monitoring networks in the three-layer structure of non-metallic composite pipes, and remotely transmit key parameters such as pressure, stress, and temperature of the pipe body to the server. Through changes in pressure, stress, temperature, etc., they can warn of abnormal operation of non-metallic pipes and sound an alarm to keep the operating environment of non-metallic composite pipes within a certain safe range. Due to the limitations of the development of materials science and electronic science, common smart pipes today include grating sensor smart pipes, electromagnetic sensor smart pipes, and metal material sensor smart pipes. Most of these types of smart pipes are made of metal and semiconductor materials, and have some disadvantages. For example, the preparation process is complicated and costly, making them unsuitable for mass production; the structure is complex and bulky, with a high failure rate; and the detection range, stability, and other performance of the sensor device cannot meet the growing needs of practical applications. Summary of the Invention

[0004] One aspect of the present invention provides a method for preparing a sensor strip, comprising the following steps:

[0005] 1) mixing a conductive filler with a first thermosetting resin or thermoplastic resin solution to obtain a dispersion;

[0006] 3) adding a first curing agent to the dispersion to obtain a coating material;

[0007] 4) applying the coating material to the surface of the fiber to obtain the sensing strip.

[0008] In a specific embodiment, the conductive filler is a force-sensitive conductive filler and / or a temperature-sensitive conductive filler.

[0009] In a specific embodiment, the force-sensitive conductive filler is selected from graphite sheets and / or graphene nanosheets. In this case, the sensing strip is a force-sensitive sensing strip.

[0010] In a specific embodiment, the temperature-sensitive conductive filler is selected from at least one of carbon fibers, carbon nanotubes, carbon black particles, and silver nanowires. In this case, the sensing strip is a temperature-sensitive sensing strip.

[0011] In a specific embodiment, the first thermosetting resin is selected from at least one of epoxy resin, thermosetting phenolic resin, polydimethylsiloxane and polyimide.

[0012] In a specific embodiment, the thermoplastic resin is at least one selected from polyurethane, polyethylene, polycarbonate, polystyrene, polyvinyl alcohol, polyethylene resin, polypropylene resin, polyvinyl chloride resin and polyvinylidene fluoride resin.

[0013] In one embodiment, the solvent for dissolving the thermoplastic resin is selected from at least one of dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diethoxymethane and tetrahydrofuran.

[0014] In one embodiment, based on the mass of the dispersion being 100%, the content of the conductive material is 3% to 14%.

[0015] In a specific embodiment, the fiber is selected from at least one of glass fiber, basalt fiber, aramid fiber and nylon fiber.

[0016] In one embodiment, the first curing agent is selected from at least one of a curing agent for epoxy resin, a curing agent for thermosetting phenolic resin, a curing agent for polydimethylsiloxane, a curing agent for polyimide, a curing agent for polyurethane, a curing agent for polyethylene, a curing agent for polycarbonate, a curing agent for polystyrene, a curing agent for polyvinyl alcohol, a curing agent for polyethylene resin, a curing agent for polypropylene resin, a curing agent for polyvinyl chloride resin, and a curing agent for polyvinylidene fluoride resin. The curing agent for epoxy resin may be ethylenediamine; the curing agent for thermosetting phenolic resin may be melamine; the curing agent for polydimethylsiloxane may be diphenylbutyl carbamate; and the curing agent for polyimide may be toluene diisocyanate.

[0017] In a specific embodiment, the conductive filler is mixed with the first thermosetting resin or thermoplastic resin solution and then dispersed to obtain the dispersion, for example, by using a disperser or ultrasound.

[0018] The second aspect of the present invention provides a method for preparing a non-metallic intelligent composite pipe, which comprises the following steps:

[0019] A) winding the force-sensitive sensor tape and / or the temperature-sensitive sensor tape prepared by the method according to any one of the present inventions onto the outer wall of a non-metallic tube before it is completely cured (i.e., before it forms a rigid solid object), and performing a first curing (the curing time before the winding of the sensor tape) to form a sensing layer covering the non-metallic tube; preferably, the force-sensitive sensor tape and the temperature-sensitive sensor tape are alternately wound onto the outer wall of the non-metallic tube;

[0020] B) affixing copper foils as electrodes of the force-sensitive sensor strip to both ends of the temperature-sensitive sensor strip, connecting the sensor strip and the electrodes with epoxy conductive silver glue, and performing a second curing process;

[0021] C) coating the sensing layer with a second thermosetting resin added with a second curing agent, and performing a third curing to obtain an outer protective layer covering the sensing layer.

[0022] Alternatively, the second aspect of the present invention provides a method for preparing a non-metallic intelligent composite pipe, which comprises the following steps:

[0023] A-2) affixing first sensing electrodes to both ends of the force-sensitive sensor strip prepared by the method of any one of the present inventions, connecting them with epoxy resin conductive silver glue, and then performing a first curing step (not completely curing, i.e., until the strip is a rigid solid object) to obtain a force-sensitive sensor strip with the first sensing electrode; affixing second sensing electrodes to both ends of the temperature-sensitive sensor strip prepared by the method of any one of the present inventions, connecting them with epoxy resin conductive silver glue, and then performing a second curing step (not completely curing, i.e., until the strip is a rigid solid object) to obtain a temperature-sensitive sensor strip with the second sensing electrode;

[0024] B-2) winding the force-sensitive sensor tape and / or the temperature-sensitive sensor tape around the outer wall of the non-metallic tube before the tape is completely cured (i.e., before it forms a rigid solid object), and performing a third curing step to form a sensing layer covering the non-metallic tube;

[0025] C-2) coating the sensing layer with a second thermosetting resin containing a second curing agent and performing a step IV curing to form an outer protective layer covering the sensing layer. In one embodiment, in step C), the second thermosetting resin material is at least one of an epoxy resin, a thermosetting phenolic resin, polydimethylsiloxane, and a polyimide; and the second curing agent is at least one of a curing agent for epoxy resin, a curing agent for thermosetting phenolic resin, a curing agent for polydimethylsiloxane, and a curing agent for polyimide.

[0026] In a specific embodiment, the curing agent for the epoxy resin is ethylenediamine, the curing agent for the thermosetting phenolic resin is melamine, the curing agent for the polydimethylsiloxane is diphenylbutyl carbamate, and the curing agent for the polyimide is toluene diisocyanate.

[0027] In one embodiment, the thickness of the sensing layer is 0.5 to 1.5 cm.

[0028] In one specific embodiment, the temperatures for the first curing, the second curing, the third curing, the first curing + the third curing, the second curing + the third curing, and the fourth curing are independently 60 to 120° C., and the durations are independently 1 to 3 hours. It should be noted that the total duration of the first curing + the third curing is 12 to 24 hours, and the total duration of the second curing + the third curing is 1 to 3 hours.

[0029] In a specific embodiment, based on the total mass of the sensing layer as 100%, the content of the conductive filler is 1% to 2%, the content of the first thermosetting resin and / or the first thermoplastic resin is 18% to 27%, the content of the first thermosetting resin curing agent and / or the first thermoplastic resin curing agent is 4% to 6.2%; and the content of the fiber is 60% to 80%.

[0030] In a specific embodiment, the content of the force-sensitive conductive filler is 0.28% to 0.41%; the content of the temperature-sensitive conductive filler is 0.68% to 1.42%; the content of the first thermosetting resin and / or the first thermoplastic resin used to disperse the force-sensitive conductive filler is 9% to 14%; the content of the first thermosetting resin and / or the first thermoplastic resin used to disperse the temperature-sensitive conductive filler is 9% to 14%; the content of the first thermosetting resin curing agent and / or the first thermoplastic resin curing agent added to the dispersion containing the force-sensitive conductive filler is 3% to 5%; the content of the first thermosetting resin curing agent and / or the first thermoplastic resin curing agent added to the dispersion containing the temperature-sensitive conductive filler is 0.3% to 1.4%; the content of the fiber is 65% to 76%.

[0031] Beneficial effects of the present invention:

[0032] (1) The non-metallic intelligent composite pipe of the present invention has two sensor belts for strain monitoring (force sensitivity) and temperature (temperature sensitivity). Compared with ordinary non-intelligent pipes, it can remotely monitor the actual pressure and temperature of the pipe, realize unmanned control, avoid the failure of non-metallic pipes due to abnormalities such as pressure and stress, play an early warning role, greatly reduce labor costs, reduce the labor intensity of operators, and avoid the risk of waste of resources and environmental pollution caused by pipeline fatigue rupture.

[0033] (2) The non-metallic intelligent composite pipe in the present invention is a non-metallic composite material as a whole. Compared with traditional metal pipes, it has lower costs and a more convenient preparation process. Therefore, non-metallic composite pipes are more suitable for mass production than traditional metal pipes. The mechanical properties and fatigue resistance of non-metallic composite pipes are also far superior to those of metal pipes. For example, its strength is five times that of steel (for example, the tensile strength of carbon fiber material is 3000mpa and the tensile modulus is 230GPA, which is 5 times that of steel). In addition, non-metallic composite pipes are lighter, with a density of one-fifth that of steel, which facilitates the assembly and installation of pipes.

[0034] (3) The sensor strip in the non-metallic intelligent composite pipe of the present invention is a fiber-based composite material, which has a consolidating and strengthening effect on the mechanical strength of the pipe when wrapped around the pipe. Therefore, the non-metallic composite pipe can better ensure that the pressure inside the pipe or the impact of external forces on the pipe will not cause damage to the pipe during service.

[0035] (4) The fiber-based composite material in the non-metallic intelligent composite pipe of the present invention combines the softness and processability of fibers, making its molding and preparation process more convenient and energy-efficient than that of metal materials. Non-metallic composite materials also offer highly flexible design capabilities, allowing specific properties of the non-metallic composite material to be enhanced based on the pipe's service environment, such as corrosion resistance and resistance to hot or cold climates. Therefore, the non-metallic composite pipe of the present invention is more capable of withstanding harsh service environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A preparation flow chart of Example 1 is shown.

[0037] Figure 2 A schematic diagram of the sensing process of the non-metallic smart composite pipe stress sensing belt is shown. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to examples. However, the examples are merely illustrative and do not limit the present invention in any way.

[0039] Example 1

[0040] Preparation flow chart Figure 1shown.

[0041] Step S1: Add 150 g of multi-walled carbon nanotubes (MWCNTs) as a conductive filler to 5 kg of epoxy resin precursor solution, and add 700 g of graphite flakes to 5 kg of polydimethylsiloxane (PDMS) precursor solution. Disperse them separately using a rapid disperser with a dispersion power of 200 W for at least 1 hour until they are completely dispersed, to obtain MWCNTs dispersion and graphite flake dispersion, respectively.

[0042] Step S2: add 1.6 kg of epoxy resin curing agent ethylenediamine (Chengdu Kelon Chemical Co., Ltd.) to the prepared MWCNTs dispersion and mix evenly to obtain a MWCNTs coating; add 500 g of PDMS curing agent diphenylcarbamate (Chengdu Kelon Chemical Co., Ltd.) to the prepared graphite flake dispersion to obtain a graphite flake coating; then take two 20 kg portions of glass fiber with an average diameter of 10 μm, apply the MWCNTs coating to one portion of the glass fiber using a fully automatic roller coater, and semi-cure to obtain a force-sensitive sensor tape with an average coating thickness of 1 mm; apply the graphite flake coating to another portion of the glass fiber using a fully automatic roller coater, and semi-cure to obtain a temperature-sensitive sensor tape with an average coating thickness of 1 mm (observe the cross section of the temperature-sensitive sensor tape with an optical microscope to obtain the coating thickness). The semi-cured force-sensitive sensor tape and the semi-cured temperature-sensitive sensor tape were wound in parallel on the outer wall of a 0.5m diameter PVC non-metallic pipe (250mm long, 15mm diameter, 5mm thick), so that the force-sensitive sensor tape and the temperature-sensitive sensor tape alternately covered the outer wall of the pipe in the axial direction of the pipe. After winding, the pipe was placed in an 80℃ oven for at least 1 hour to form a sensing layer with an average thickness of 0.5cm. The sensing layer included 0.15kg of multi-walled carbon nanotubes, 5kg of epoxy resin, and 1. 6kg, 0.7kg of graphite sheet, 5kg of polydimethylsiloxane, 0.5kg of polydimethylsiloxane curing agent and 40kg of glass fiber. Taking the total mass of the sensing layer as 100%, the content of multi-walled carbon nanotubes is 0.283%, the content of epoxy resin is 9.443%, the content of epoxy resin curing agent is 3.022%, the content of graphite sheet is 1.322%, the content of polydimethylsiloxane is 9.443%, the content of polydimethylsiloxane curing agent is 0.944%, and the content of glass fiber is 75.543%.

[0043] Step S3: Copper foils are attached to both ends of the force-sensitive sensor belt and the temperature-sensitive sensor belt as electrodes of the sensor belt, and the sensor belt and the electrodes are connected with epoxy resin conductive silver glue and cured in an 80° C. oven for 1 hour.

[0044] Step S4: coating the sensing layer with epoxy resin containing epoxy resin curing agent ethylenediamine using a fully automatic roller coater, and curing the epoxy resin in an oven at 80° C. for 1 hour to obtain an outer protective layer of the non-metallic intelligent composite tube.

[0045] Based on the microscopic composition data and material conductivity data tested by scanning electron microscope and resistance tester, a schematic diagram of the sensing process of the non-metallic intelligent composite pipe stress sensing belt is drawn as follows: Figure 2 As shown. Among them, Figure 2 The a in the figure represents the initial distribution of the conductive filler in the stress sensing belt of the non-metallic intelligent composite tube. The conductive filler is dispersed in the resin polymer matrix to form a conductive path. Figure 2 Figure b shows the schematic diagram of the strain ε2 of the non-metallic intelligent composite tube temperature-sensitive sensor belt. At this time, the conductive filler moves with the deformation of the polymer matrix, and the original conductive network is damaged to a certain extent. At this time, the resistance of the composite material sensor belt increases. Figure 2 Figure c represents a schematic diagram of a non-metallic smart composite pipe's force-sensitive sensor strip undergoing strain ε3. At this point, the sensor strip experiences significant strain or even fracture, severely damaging the conductive network constructed by the conductive filler within the stress-sensitive strip. The total resistance of the sensor strip becomes infinite. Therefore, changes in the resistance of the stress-sensitive strip can reflect the stress and, ultimately, the safety status of the non-metallic smart pipe. Similarly, the resistance of conductive composite materials is affected by temperature. As temperature rises, the efficiency of electron conduction between the graphite sheets in the temperature-sensitive sensor strip increases, increasing the current flowing through the strip. Therefore, the temperature of the fluid within the pipe can be reflected in real time through this current.

[0046] Comparative Example 1

[0047] Step S1: Take 40 kg of glass fiber with an average diameter of 10 μm, and wind the glass fiber around the outer wall of a PVC non-metallic pipe with a diameter of 0.5 m, so that the glass fiber covers the outer wall of the pipe in the axial direction of the pipe, thereby forming a glass fiber layer with an average thickness of 0.5 cm.

[0048] Step S2: coating the glass fiber layer with epoxy resin containing epoxy resin curing agent ethylenediamine using a fully automatic roller coater, and curing the epoxy resin in an oven at 80° C. for 1 hour to obtain an outer protective layer of the non-metallic composite pipe.

[0049] Example 2

[0050] Step S1: Add 150 g of multi-walled carbon nanotubes (MWCNTs) as a conductive filler to 5 kg of epoxy resin precursor solution, and add 250 g of graphite flakes to 5 kg of polydimethylsiloxane (PDMS) precursor solution. Disperse them separately using a rapid disperser with a dispersion power of 200 W for at least 1 hour until they are completely dispersed, to obtain MWCNTs dispersion and graphite flake dispersion, respectively.

[0051] Step S2: add 1.6 kg of epoxy resin curing agent ethylenediamine (Chengdu Kelon Chemical Co., Ltd.) to the prepared MWCNTs dispersion and mix evenly to obtain a MWCNTs coating; add 500 g of PDMS curing agent diphenylcarbamate (Chengdu Kelon Chemical Co., Ltd.) to the prepared graphite flake dispersion to obtain a graphite flake coating; then take two aramid fibers with an average diameter of 20 μm and a mass of 12 kg, apply the MWCNTs coating to one aramid fiber using a fully automatic roller coater, and semi-cure to obtain a force-sensitive sensor tape with an average coating thickness of 2 mm; apply the graphite flake coating to another aramid fiber using a fully automatic roller coater and semi-cure to obtain a temperature-sensitive sensor tape with an average coating thickness of 2 mm. The semi-cured force-sensitive sensing tape and the semi-cured temperature-sensitive sensing tape were wound in parallel on the outer wall of a PVC non-metallic pipe with a diameter of 0.35 m (length 250 mm, diameter 15 mm, thickness 5 mm), so that the force-sensitive sensing tape and the temperature-sensitive sensing tape were alternately covered on the outer wall of the pipe in the axial direction of the pipe. After the winding was completed, the pipe was placed in an 80°C oven for at least 1 hour to form a sensing layer with an average thickness of 1.0 cm. The sensing layer included 0.15 kg of multi-walled carbon nanotubes, 5 kg of epoxy resin, and 1.6 kg of epoxy resin curing agent. kg, 0.25 kg of graphite sheets, 5 kg of polydimethylsiloxane, 0.5 kg of polydimethylsiloxane curing agent and 24 kg of aramid fiber. Taking the total mass of the sensing layer as 100%, the content of multi-walled carbon nanotubes is 0.411%, the content of epoxy resin is 13.699%, the content of epoxy resin curing agent is 4.834%, the content of graphite sheets is 0.685%, the content of polydimethylsiloxane is 13.699%, the content of polydimethylsiloxane curing agent is 1.370%, and the content of aramid fiber is 65.753%.

[0052] Step S3: Copper foils are attached to both ends of the force-sensitive sensor belt and the temperature-sensitive sensor belt as electrodes of the sensor belt, and the sensor belt and the electrodes are connected with epoxy resin conductive silver glue and cured in an 80° C. oven for 1 hour.

[0053] Step S4: coating the sensing layer with epoxy resin containing epoxy resin curing agent ethylenediamine using a fully automatic roller coater, and curing the epoxy resin in an oven at 80° C. for 1 hour to obtain an outer protective layer of the non-metallic intelligent composite tube.

[0054] Comparative Example 2

[0055] Step S1: Take 24 kg of aramid fiber with an average diameter of 20 μm, and wind the aramid fiber around the outer wall of a PVC non-metallic pipe with a diameter of 0.5 m, so that the aramid fiber covers the outer wall of the pipe in the axial direction of the pipe, thereby forming an aramid fiber layer with an average thickness of 2.0 cm.

[0056] Step S2: coating the aramid fiber layer with epoxy resin containing epoxy resin curing agent ethylenediamine using a fully automatic roller coater, and curing the mixture in an oven at 80° C. for 1 hour to obtain an outer protective layer of the non-metallic composite pipe.

[0057] Example 3

[0058] Step S1: adding 150 g of silver nanowires as a conductive filler to 5 kg of an epoxy resin precursor (Chengdu Kelong Chemical Reagent Factory, CAS NO: 38891-59-7), and adding 700 g of graphite flakes to 5 kg of a phenolic resin precursor (Chengdu Kelong Chemical Reagent Factory, CAS NO: 9003-35-4), and dispersing them separately for at least 1 hour using a rapid disperser with a dispersing power of 200 W until completely dispersed, to obtain a silver nanowire dispersion and a graphite flake dispersion, respectively.

[0059] Step S2: Add 2.5 kg of curing agent ethylenediamine (Chengdu Kelon Chemical Co., Ltd.) to the prepared silver nanowire dispersion and mix evenly to obtain a silver nanowire coating; add 150 g of curing agent melamine (Chengdu Kelon Chemical Co., Ltd.) to the prepared graphite flake dispersion to obtain a graphite flake coating; then take two basalt fibers with a mass of 18 kg and an average diameter of 15 μm, apply the silver nanowire coating to one basalt fiber using a fully automatic roller coater, and semi-cure to obtain a force-sensitive sensor tape with an average coating thickness of 1.5 mm; apply the graphite flake coating to another basalt fiber using a fully automatic roller coater, and semi-cure to obtain a temperature-sensitive sensor tape with an average coating thickness of 1.5 mm. The semi-cured force-sensitive sensing tape and the semi-cured temperature-sensitive sensing tape were wound in parallel on the outer wall of a PVC non-metallic pipe with a diameter of 0.5 m (length 250 mm, diameter 15 mm, thickness 5 mm), so that the force-sensitive sensing tape and the temperature-sensitive sensing tape were alternately covered on the outer wall of the pipe in the axial direction of the pipe. After the winding was completed, the tape was placed in an 80°C oven for at least 1 hour to form a sensing layer with an average thickness of 1.5 cm. The sensing layer included 0.15 kg of silver nanowires, 5 kg of epoxy resin, and epoxy resin curing agent. The sensing layer comprises 2.5 kg of epoxy resin, 0.7 kg of graphite sheet, 5 kg of phenolic resin, 0.15 kg of phenolic resin curing agent and 36 kg of basalt fiber. Taking the total mass of the sensing layer as 100%, the content of silver nanowires is 0.303%, the content of epoxy resin is 10.101%, the content of epoxy resin curing agent is 5.051%, the content of graphite sheet is 1.414%, the content of phenolic resin is 10.101%, the content of phenolic resin curing agent is 0.303%, and the content of basalt fiber is 72.727%.

[0060] Step S3: Copper foils are attached to both ends of the force-sensitive sensor belt and the temperature-sensitive sensor belt as electrodes of the sensor belt, and the sensor belt and the electrodes are connected with epoxy resin conductive silver glue and cured in an 80° C. oven for 1 hour.

[0061] Step S4: coating the sensing layer with epoxy resin containing epoxy resin curing agent ethylenediamine using a fully automatic roller coater, and curing the epoxy resin in an oven at 80° C. for 1 hour to obtain an outer protective layer of the non-metallic intelligent composite tube.

[0062] Comparative Example 3

[0063] Step S1: Take 36 kg of basalt fiber with an average diameter of 20 μm, and wind the basalt fiber around the outer wall of a PVC non-metallic pipe with a diameter of 0.5 m, so that the basalt fiber covers the outer wall of the pipe in the axial direction of the pipe, thereby forming a basalt fiber layer with an average thickness of 2.0 cm.

[0064] Step S2: coating the basalt fiber layer with epoxy resin containing ethylenediamine as a curing agent using a fully automatic roller coater, and curing the mixture in an oven at 80° C. for 1 hour to obtain an outer protective layer of the non-metallic composite pipe.

[0065] Comparative Example 4

[0066] PVC long strip specimen without any outer layer: 250mm long, 15mm wide, 5mm thick.

[0067] Performance Testing

[0068] According to the national standard GBT1040.4-2006 for mechanical properties of materials, five defect-free specimens were tested using a universal testing machine, and the average value was calculated. The results are shown in Table 1.

[0069] Example Ability to detect force / temperature Breaking strength (MPa) Example 1 have 94±3 Comparative Example 1 none 75±5 Example 2 have 84±4 Comparative Example 2 none 96±7 Example 3 have 92±5 Comparative Example 3 none 79±3 Comparative Example 4 none 45±5

[0070] According to the results in Table 1, the use of the sensing layer of the present invention not only provides the ability to monitor pipeline operation performance, but also significantly increases the fracture strength.

[0071] In summary, the present invention provides a method for preparing a non-metallic intelligent composite pipe, firstly, two conductive fillers are dispersed in two resin precursors; then the mixed solution is coated on two fiber materials and wrapped around the inner pipe, heated and cured to obtain a force-sensitive (stress) sensing tape and a temperature-sensitive (temperature) sensing tape, and electrodes are added; finally, a layer of resin is coated on the outside of the sensing tape and cured to obtain a protective layer. Compared with traditional metal-based non-intelligent pipes, non-metallic intelligent composite pipes prepared based on fiber-based and conductive composite materials as raw materials realize unmanned control, greatly reduce the labor intensity of operators, avoid the failure of non-metallic pipes due to abnormalities such as pressure and stress, and play an early warning role. At the same time, the fiber-based composite material also strengthens the pipeline. The present invention has the potential to replace traditional metal-based non-intelligent pipes.

[0072] Although the present invention has been described with reference to specific embodiments, those skilled in the art will appreciate that various modifications may be made without departing from the true spirit and scope of the invention. Furthermore, the subject matter, spirit, and scope of the invention may be modified in various ways to adapt to specific circumstances, materials, combinations of materials, and methods. All such modifications are intended to be within the scope of the claims.

Claims

1. A method for preparing a sensor strip, comprising the following steps: 1) mixing a conductive filler with a first thermosetting resin or thermoplastic resin solution to obtain a dispersion; 2) adding a first curing agent to the dispersion to obtain a coating material; 3) applying the coating material to the surface of the fiber to obtain the sensing strip.

2. The method according to claim 1, characterized in that The conductive filler is a force-sensitive conductive filler and / or a temperature-sensitive conductive filler; Preferably, the force-sensitive conductive filler is selected from graphite sheets and / or graphene nanosheets. In this case, the sensing strip is a force-sensitive sensing strip. Preferably, the temperature-sensitive conductive filler is selected from at least one of carbon fibers, carbon nanotubes, carbon black particles, and silver nanowires. In this case, the sensing strip is a temperature-sensitive sensing strip.

3. The method according to claim 1 or 2, characterized in that The first thermosetting resin is selected from at least one of epoxy resin, thermosetting phenolic resin, polydimethylsiloxane and polyimide; and / or The thermoplastic resin is selected from at least one of polyurethane, polyethylene, polycarbonate, polystyrene, polyvinyl alcohol, polyethylene resin, polypropylene resin, polyvinyl chloride resin and polyvinylidene fluoride resin; The solvent for dissolving the thermoplastic resin is at least one selected from dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diethoxymethane and tetrahydrofuran.

4. The method according to any one of claims 1 to 3, characterized in that Based on the mass of the dispersion as 100%, the content of the conductive material is 3% to 14%.

5. The method according to any one of claims 1 to 4, characterized in that The fiber is selected from at least one of glass fiber, basalt fiber, aramid fiber and nylon fiber.

6. The method according to any one of claims 1 to 5, characterized in that The first curing agent is selected from at least one of a curing agent for epoxy resin, a curing agent for thermosetting phenolic resin, a curing agent for polydimethylsiloxane, a curing agent for polyimide, a curing agent for polyurethane, a curing agent for polyethylene, a curing agent for polycarbonate, a curing agent for polystyrene, a curing agent for polyvinyl alcohol, a curing agent for polyethylene resin, a curing agent for polypropylene resin, a curing agent for polyvinyl chloride resin, and a curing agent for polyvinylidene fluoride resin; Preferably, the curing agent for epoxy resin is ethylenediamine, the curing agent for thermosetting phenolic resin is melamine, the curing agent for polydimethylsiloxane is diphenylbutyl carbamate, and the curing agent for polyimide is toluene diisocyanate.

7. A method for preparing a non-metallic intelligent composite pipe, comprising the following steps: A) winding the force-sensitive sensing tape and / or the temperature-sensitive sensing tape prepared by the method according to any one of claims 1 to 6 around the outer wall of a non-metallic tube before complete curing, and performing a first curing to form a sensing layer coated on the non-metallic tube; preferably, the force-sensitive sensing tape and the temperature-sensitive sensing tape are alternately wound around the outer wall of the non-metallic tube; B) affixing copper foils as electrodes of the force-sensitive sensor strip to both ends of the temperature-sensitive sensor strip, connecting the sensor strip and the electrodes with epoxy conductive silver glue, and performing a second curing process; C) coating the sensing layer with a second thermosetting resin added with a second curing agent, and performing a third curing to obtain an outer protective layer covering the sensing layer; or A-2) affixing first sensing electrodes to both ends of the force-sensitive sensor strip prepared by the method of any one of claims 1 to 7, connecting the strips with epoxy resin conductive silver glue, and then performing a first curing step to obtain a force-sensitive sensor strip with first sensing electrodes; A second sensing electrode is attached to each end of the temperature-sensitive sensor strip prepared by the method according to any one of claims 1 to 7, and connected with epoxy resin conductive silver glue, and then subjected to a second curing step to obtain a temperature-sensitive sensor strip with a second sensing electrode; B-2) winding the force-sensitive sensor tape and / or the temperature-sensitive sensor tape around the outer wall of the non-metallic tube before the tape is completely cured, and performing a third curing step to form a sensing layer covering the non-metallic tube; C-2) coating the sensing layer with a second thermosetting resin added with a second curing agent, and performing a stage IV curing to obtain an outer protective layer covering the sensing layer.

8. The method according to claim 7, characterized in that In the step C), the second thermosetting resin is at least one of epoxy resin, thermosetting phenolic resin, polydimethylsiloxane and polyimide; The second curing agent is selected from at least one of a curing agent for epoxy resin, a curing agent for thermosetting phenolic resin, a curing agent for polydimethylsiloxane, and a curing agent for polyimide; Preferably, the curing agent for the epoxy resin is ethylenediamine, the curing agent for the thermosetting phenolic resin is melamine, the curing agent for the polydimethylsiloxane is diphenylbutyl carbamate, and the curing agent for the polyimide is toluene diisocyanate; Preferably, the thickness of the sensing layer is 0.5 to 1.5 cm.

9. The method according to claim 7, characterized in that The temperatures of the first curing, the second curing, the third curing, the I curing + the III curing, the II curing + the III curing, and the IV curing are independently 60 to 120° C., and the times are independently 1 to 3 hours.

10. The method according to claim 7, characterized in that Based on the total mass of the sensing layer as 100%, the content of the conductive filler is 1% to 2%, the content of the first thermosetting resin and / or the first thermoplastic resin is 18% to 27%, the content of the first thermosetting resin curing agent and / or the first thermoplastic resin curing agent is 4% to 6.2%, and the content of the fiber is 60% to 80%. Preferably, the content of the force-sensitive conductive filler is 0.28% to 0.41%; the content of the temperature-sensitive conductive filler is 0.68% to 1.42%; the content of the first thermosetting resin and / or the first thermoplastic resin used to disperse the force-sensitive conductive filler is 9% to 14%; the content of the first thermosetting resin and / or the first thermoplastic resin used to disperse the temperature-sensitive conductive filler is 9% to 14%; the content of the first thermosetting resin curing agent and / or the first thermoplastic resin curing agent added to the dispersion containing the force-sensitive conductive filler is 3% to 5%; the content of the first thermosetting resin curing agent and / or the first thermoplastic resin curing agent added to the dispersion containing the temperature-sensitive conductive filler is 0.3% to 1.4%; the content of the fiber is 65% to 76%.

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