A color-changing material for detecting leaks in a town gas pipeline

Abstract

The present application belongs to the technical field of urban gas pipeline safety protection and intelligent sensing material, especially a color-changing material for urban gas pipeline leakage detection, belonging to the technical field of gas safety detection. The material takes flexible and weather-resistant polyimide aerogel as a matrix, and is compounded with HKUST-1 metal organic framework material with high methane adsorption capacity, nano copper-prussian blue composite color developing indicator sensitive to methane and tetrahydrothiophene, and modified additives such as nano titanium dioxide and graphene nanosheet. The material is specially designed for urban gas (methane and ≤8% tetrahydrothiophene), and can respond to trace leakage (methane concentration ≥0.3%) within 5 seconds through adsorption enrichment and synergistic color developing mechanism, with the color quickly changing from the original color to high-contrast bright red, which can be clearly identified at a distance of 3 meters. The material has the advantages of passive maintenance-free, rapid response, high sensitivity, strong weather resistance (service life of 8-10 years), low cost and the like.

Description

Technical Field

[0001] This invention relates to the field of safety protection and intelligent sensing materials for urban gas pipelines, specifically to a flexible color-changing material that can respond quickly to both methane and tetrahydrothiophene in urban gas, and is mainly used for passive visual detection of easily leaking parts such as exposed urban gas pipelines, welded joints, and valves. Background Technology

[0002] Town gas primarily consists of methane, with tetrahydrothiophene (≤8% by mass) added as an odor tracer according to national safety standards. During long-term operation, exposed pipe welds, flange joints, and valve connections are prone to minor leaks due to corrosion and vibration. Methane's explosive limits are 5%-15%; if even minor leaks are not detected promptly, they can easily lead to major safety accidents such as explosions and fires.

[0003] Current gas leak detection technologies suffer from the following shortcomings: 1) Manual inspections are inefficient and subjective, making all-weather monitoring impossible; 2) Electrochemical and infrared gas sensors rely on power sources, resulting in high equipment costs, complex maintenance, and difficulties in outdoor deployment; 3) Existing color-changing materials only respond to methane, exhibiting shallow color development, low contrast, and difficulty in identification under natural light, failing to adapt to the actual composition of urban gas; 4) The materials have poor weather resistance and short lifespan, hindering large-scale engineering applications. Therefore, there is an urgent need to develop a passive, low-cost, highly sensitive, and highly weather-resistant color-changing detection material. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a color-changing material for detecting leaks in urban gas pipelines, solving the following problems in current gas leak detection technologies: 1) Manual inspections are inefficient and subjective, making all-weather monitoring impossible; 2) Electrochemical and infrared gas sensors rely on power supplies, resulting in high equipment costs, complex maintenance, and difficulties in outdoor deployment; 3) Existing color-changing materials only respond to methane, exhibiting light color, low contrast, and difficulty in identification under natural light, failing to adapt to the actual composition of urban gas; 4) The materials have poor weather resistance and short lifespan, hindering large-scale engineering applications.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A color-changing material for detecting leaks in urban gas pipelines, comprising the following components by weight:

[0007] Polyimide aerogel matrix: 72-86 parts

[0008] HKUST-1 copper-based metal-organic framework material: 17-23 parts

[0009] Nano-copper-Prussian blue composite colorimetric indicator: 1.0~1.4 parts

[0010] Nano titanium dioxide: 0.3~0.7 parts

[0011] Graphene nanosheets: 0.2~0.4 parts

[0012] HKUST-1 is a copper-based pyromellitic acid metal-organic framework (Cu-BTC) material. Its three-dimensional porous crystal structure has excellent methane adsorption capacity and is the core adsorption carrier for detecting trace methane leaks with a volume fraction of 0.3%.

[0013] Preferably, the optimal mass ratio of each component is:

[0014] Polyimide aerogel matrix: 80 parts

[0015] HKUST-1 copper-based metal-organic framework material: 20 parts

[0016] Nano-copper-Prussian blue composite colorimetric indicator: 1.2 parts

[0017] Nano titanium dioxide: 0.4 parts

[0018] Graphene nanosheets: 0.2 parts

[0019] (III) Detection Mechanism

[0020] The detection mechanism of this invention is a dual mechanism of "adsorption enrichment-synergistic color development":

[0021] The porous structure of HKUST-1 enables rapid capture and enrichment of low concentrations (0.3%) of methane gas in the environment, achieving preliminary identification and concentration of trace leaks.

[0022] The tracer tetrahydrothiophene (mass fraction ≤8%) in urban gas reacts synergistically with methane and undergoes a coordination reaction with the nano-copper-based composite colorimetric indicator in the material, accelerating the valence state transformation of metal ions.

[0023] Under the dual action, the material rapidly changes from its transparent or light white original color to a highly saturated bright red within 4-5 seconds after contact with the leaking gas. The color change is permanent and stable, and can be clearly identified by the naked eye from 3 meters away, thus achieving precise location of the leak point.

[0024] (iv) Preparation method

[0025] The method for preparing the color-changing material of the present invention includes the following steps:

[0026] Matrix preparation: 3,4-Diaminodiphenyl ether and bisphenol A type diether dianhydride were dissolved in N-methylpyrrolidone solvent and stirred in a water bath at 50°C until completely dissolved. Melamine crosslinking agent was added to react and polyimide sol was obtained.

[0027] Functional blending: HKUST-1 copper-based metal-organic framework material, nano-copper-Prussian blue composite colorimetric indicator, nano-titanium dioxide and graphene nanosheets are added to the above sol according to the specified ratio. The mixture is then ultrasonically dispersed to ensure that all components are mixed evenly and without agglomeration.

[0028] Molding and curing: The uniformly mixed slurry is coated into a film of a predetermined thickness, allowed to stand at room temperature to gel, and then subjected to vacuum freeze drying to obtain a flexible porous material matrix.

[0029] Post-processing: Spray an ultra-thin hydrophobic coating onto the cured material to improve its weather resistance, and finally cut it into sheet or strip products suitable for pipe wrapping or attachment.

[0030] Compared with existing technologies, the present invention provides a color-changing material for detecting leaks in urban gas pipelines, which has the following beneficial effects:

[0031] Dual-component synergistic response, highly targeted: Designed specifically for urban gas (methane + tetrahydrothiophene), the dual response mechanism significantly improves color contrast, solving the problem of difficult identification of traditional single-response materials under outdoor light.

[0032] Ultra-high sensitivity and rapid response: It can detect trace methane leaks as low as 0.3% by volume, with a response time of ≤5 seconds. The sensitivity is about 40% higher than that of existing technologies, enabling earlier safety warnings.

[0033] Passive and maintenance-free with extremely low cost: No power supply or calibration required, easy installation (wrap-around or patch), and virtually no maintenance throughout its lifespan. The material cost per unit is no more than 0.8 yuan, about 1 / 200th of that of traditional electronic sensors, which is conducive to large-scale promotion.

[0034] Excellent weather resistance and long lifespan: The material can work stably in a temperature range of -30℃ to 180℃ and in a humidity environment of up to 95%. It has excellent resistance to ultraviolet aging and an outdoor service life of 8-10 years, far exceeding that of existing materials (1-2 years).

[0035] The process is green and can be mass-produced: the preparation process is carried out at normal temperature and pressure, with no high-risk reactions or pollutant emissions, the process flow is mature, the finished product qualification rate is high (≥98%), and it is suitable for pilot-scale and large-scale mass production. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example

[0038] Example 1: Preparation and Testing of Optimal Sample Ratio

[0039] Samples were prepared according to the optimal mass ratio (80 parts of polyimide aerogel matrix, 20 parts of HKUST-1 material, 1.2 parts of nano-copper-Prussian blue composite colorimetric indicator, 0.4 parts of nano-titanium dioxide, and 0.2 parts of graphene nanosheets).

[0040] Test conditions: The test was conducted under normal temperature and humidity conditions using a mixture of methane and 5% tetrahydrothiophene that meets national standards.

[0041] Test results: After the material came into contact with the leaked gas, it changed from its original color to bright red uniformly within 4.5 seconds. It can clearly identify trace amounts of methane leaks, up to 0.3%, and the color development effect is stable.

[0042] Example 2: On-site simulation verification of outdoor pipelines

[0043] A wrapping tape made from the material of this invention was fixed to a simulated weld joint of an exposed gas pipeline in a high-rise building. A simulated leak test was conducted under natural ventilation and lighting conditions.

[0044] Test results: The material develops color rapidly, allowing inspectors to instantly detect and locate leaks from 3 meters away. After 30 days of continuous operation, the material showed no performance degradation.

[0045] Example 3: Comparative Verification of Synergistic Color Development Effect

[0046] Tests were conducted in a pure methane environment and in a methane environment containing 8% tetrahydrothiophene.

[0047] Test results: In a pure methane environment, the material's color saturation is approximately 60%, with an effective detection distance of about 1.5 meters; in an environment where methane and tetrahydrothiophene coexist, the color saturation reaches 100%, and the effective detection distance increases to 3 meters. These results fully verify the synergistic enhancing effect of tetrahydrothiophene on methane color development, demonstrating the core innovative advantages of this invention.

[0048] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A color-changing material for detecting leaks in urban gas pipelines, characterized in that: By mass fraction, it consists of the following components: 72-86 parts of polyimide aerogel matrix, 17-23 parts of HKUST-1 copper-based metal-organic framework material, 1.0-1.4 parts of nano-copper-Prussian blue composite colorimetric indicator, 0.3-0.7 parts of nano-titanium dioxide, and 0.2-0.4 parts of graphene nanosheets.

2. The color-changing material according to claim 1, characterized in that, The mass ratio of each component is as follows: 80 parts of polyimide aerogel matrix, 20 parts of HKUST-1 copper-based metal-organic framework material, 1.2 parts of nano copper-Prussian blue composite colorimetric indicator, 0.4 parts of nano titanium dioxide, and 0.2 parts of graphene nanosheets.

3. The color-changing material according to claim 1 or 2, characterized in that, The material can undergo a synergistic chemical reaction with methane in town gas and tetrahydrothiophene with a mass fraction of ≤8%, causing the material's color to change from its original color to bright red.

4. The color-changing material according to claim 1 or 2, characterized in that, The material's response time to urban gas leaks is no more than 5 seconds, and it can detect methane leaks with a volume fraction of not less than 0.3%. The material's service life is 8 to 10 years.

5. The color-changing material according to claim 1 or 2, characterized in that, The material is a flexible film or strip structure that can be fixed to the weld joints, flanges, or valves of exposed urban gas pipelines by wrapping or patching.

6. A method for preparing the color-changing material as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Preparation of polyimide sol matrix; S2: Functional components are added to the matrix for ultrasonic blending modification; S3: After the mixed slurry is molded, it is then vacuum freeze-dried and cured. S4: Perform hydrophobic post-treatment on the cured material.