A flame-retardant polyurethane foam firewall integrated with a multi-parameter intelligent detector, and a preparation method and application thereof

Abstract

The present application belongs to the technical field of intelligent fire engineering and polymer composite material, and particularly relates to a fire-retardant polyurethane foam fireproof wall integrated with a multi-parameter intelligent detector and a preparation method thereof. The fireproof wall comprises a fire-retardant polyurethane foam base body and an embedded multi-parameter intelligent detector. The top surface of the detector packaging shell is provided with an array of inverted conical anchor claws, and dovetail grooves are formed in the side wall along the length direction. The foam base body fills and wraps the inverted conical anchor claws and the dovetail grooves through an in-situ foaming process, thereby forming a stable double mechanical interlocking structure in the vertical and horizontal directions. The present application effectively solves the technical problems of poor interface bonding force between rigid electronic devices and flexible foam base body and easy peeling during long-term service. Meanwhile, the embedded sensor array is used to realize extremely early and accurate early warning of the characteristic gas in the initial pyrolysis stage of the material, and the structural function integration of physical fire-retardant plugging and intrinsic safety monitoring is realized.

Description

Technical Field

[0001] This invention belongs to the field of intelligent fire protection engineering and polymer composite materials technology, specifically relating to a flame-retardant polyurethane foam firewall with integrated multi-parameter intelligent detector and its preparation method. Background Technology

[0002] With the acceleration of urbanization and the exponential growth of electricity load, underground utility tunnels and cable tunnels have become the main arteries for urban energy transmission. Due to the high density of cable laying, the relatively enclosed operating environment, and complex ventilation conditions, fires caused by cable overload, insulation aging, or poor joint contact can easily create a "chimney effect," resulting in catastrophic equipment damage and large-scale power outages. In the practice of fire protection engineering in power systems, constructing firewalls for physical partitioning and isolation, along with an automatic fire alarm system for monitoring, are the two core lines of defense for ensuring the safety of cable tunnels. Among these, flame-retardant polyurethane foam, due to its excellent sealing properties, thermal insulation, and ease of construction, is widely used as a filling material for firewalls, sealing holes, and filling gaps.

[0003] However, the current "passive physical isolation + active external monitoring" separation-based prevention and control model has revealed significant lag and limitations in practical applications. From the perspective of fire pyrolysis kinetics, in the initial pyrolysis stage of polyurethane and other high-molecular organic materials, the breakage and oxidation of macromolecular chains preferentially occur, releasing carbon monoxide, hydrogen, and specific volatile organic compounds. This process often lasts from several minutes to tens of minutes, far earlier than the accumulation of visible smoke particles or the generation of open flames. Existing point-type smoke or heat detectors are usually installed on the top or side walls of tunnels. Limited by airflow stratification, obstructions, and the rate of smoke diffusion within the tunnel, alarms are often only triggered when the fire has developed to a certain scale, with large amounts of pyrolysis products overflowing and forming convection. This time lag causes maintenance personnel to miss the optimal window for intervention during the fire's "incubation period," resulting in firewalls passively enduring high-temperature erosion only after the fire is already out of control, failing to perform their intended flame-retardant and heat-insulating functions.

[0004] To address the issue of delayed early warning, academia and engineering have attempted to directly integrate sensing elements into fire-resistant sealing materials to achieve in-situ monitoring of the material's microenvironment. However, in terms of technical implementation, integrating electronic devices with polyurethane foam through simple physical embedding or surface mounting faces severe interfacial mechanics and thermodynamic challenges. First, the polyurethane foaming process is a chemical reaction accompanied by intense volume expansion and strong exothermic reactions. The instantaneous internal pressure and high temperature can easily damage or cause parameter drift in delicate microelectronic sensing elements. Second, and more critically, there is a significant modulus mismatch and difference in thermal expansion coefficients between rigid electronic packaging materials (such as metals or rigid plastics) and flexible or semi-rigid polyurethane foam matrices. Under long-term temperature and humidity cycling and tunnel micro-vibration environments, this heterogeneous material interface is prone to stress concentration, leading to interfacial delamination or microcracks. Interfacial failure not only causes detectors to loosen and detach, resulting in structural instability, but also allows moisture to infiltrate along the gaps, causing circuit corrosion and short circuits, ultimately leading to the paralysis of the monitoring system.

[0005] Therefore, how to develop a material that can withstand the impact of in-situ foaming process and form a stable and durable mechanical interlocking structure with the foam matrix after curing, so as to achieve the very early and accurate capture of the characteristic gases of initial pyrolysis without damaging the integrity of the firewall, has become a key technical problem that urgently needs to be solved in the current cross-field of power fire prevention and intelligent monitoring. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned shortcomings by providing a flame-retardant polyurethane foam firewall with integrated multi-parameter intelligent detectors and its preparation method.

[0007] Firstly, a flame-retardant polyurethane foam firewall integrating a multi-parameter intelligent detector adopts the following technical solution: A flame-retardant polyurethane foam firewall integrating a multi-parameter intelligent detector includes a flame-retardant polyurethane foam matrix and at least one multi-parameter intelligent detector embedded in the flame-retardant polyurethane foam matrix. The multi-parameter intelligent detector includes an encapsulation shell and a sensing unit, a control circuit unit, and a power supply unit disposed within the encapsulation shell. The top surface of the encapsulation shell is provided with a plurality of inverted conical anchor claws arranged in an array, and the sidewalls of the encapsulation shell are provided with dovetail grooves along the length direction. The flame-retardant polyurethane foam matrix is ​​foamed in situ to fill and enclose the root undercut area of ​​the inverted conical anchor claws and the inner cavity of the dovetail grooves, thereby forming a double mechanical interlocking structure between the multi-parameter intelligent detector and the flame-retardant polyurethane foam matrix in the vertical and horizontal directions.

[0008] Furthermore, the flame-retardant polyurethane foam matrix is ​​generated by the reaction of a first component and a second component; wherein the first component includes a polyether polyol, a composite flame retardant, a catalyst, a foam stabilizer, and a blowing agent, and the second component includes an isocyanate.

[0009] Further, the composite flame retardant is selected from one or more of expanded graphite, ammonium polyphosphate, melamine, aluminum hydroxide, and dimethyl methyl phosphate; the catalyst is selected from one or more of triethylenediamine, bis(dimethylaminoethyl) ether, dibutyltin dilaurate, and stannous octoate; the foam stabilizer is a polysiloxane-polyoxyolefin block copolymer; the foaming agent is water; the hydroxyl value of the polyether polyol is 350 mgKOH / g~450 mgKOH / g; and the weight ratio of the first component to the second component is (5.2~5.8):1.

[0010] Furthermore, the material of the encapsulation shell is polyphenylene sulfide; the inverted conical anchor claw is made of metal and is implanted into the top surface of the encapsulation shell through an insert injection molding process, and the height of the inverted conical anchor claw protruding from the surface of the encapsulation shell is 3.0 mm to 5.0 mm.

[0011] Furthermore, the interior of the encapsulation shell is provided with three physically isolated independent chambers along the horizontal direction, which are respectively used to accommodate the power supply unit, the control circuit unit, and the sensing unit; the three independent chambers are filled with flame-retardant and thermally conductive epoxy potting compound, and the filling height of the potting compound covers the top of the control circuit unit and the power supply unit.

[0012] Furthermore, the sensing unit includes an alumina ceramic substrate, on which a MEMS gas sensor array and a thin-film thermocouple are integrated; the MEMS gas sensor array includes an electrochemical sensing unit sensitive to carbon monoxide and a metal oxide semiconductor sensing unit sensitive to volatile organic compounds; the top surface of the package housing is provided with an array of vent holes corresponding to the sensing unit, and the vent hole array has a diameter of 2.0 mm to 3.0 mm.

[0013] Secondly, a method for preparing a flame-retardant polyurethane foam firewall integrating a multi-parameter intelligent detector adopts the following technical solution: A method for preparing a flame-retardant polyurethane foam firewall integrating a multi-parameter intelligent detector includes the following steps: Step (1): Prepare a packaged shell with inverted conical anchoring claws by insert injection molding process, assemble electronic components and pot the shell to obtain the multi-parameter intelligent detector; Step (2): Fix the multi-parameter intelligent detector to a predetermined position on the inner wall of the foaming mold through the positioning structure on its surface; Step (3): Prepare the first and second components of the flame-retardant polyurethane composite material respectively. Step (4): After mixing the first component and the second component, the mixture is poured into the foaming mold. During the foaming and expansion process, the mixture flows through the surface of the encapsulation shell and uses its fluidity to penetrate and fill the undercut gap and side wall dovetail groove of the inverted conical anchor claw. Step (5): After the foam system has matured, demold to form an integrated flame-retardant polyurethane foam firewall.

[0014] Further, in step (3), the preparation of the first component includes the following steps: at a temperature of 23 ℃ to 27 ℃, the polyether polyol, composite flame retardant, catalyst, foam stabilizer and foaming agent are stirred at a speed of 400 rpm to 600 rpm for 15 min to 20 min to obtain the first component.

[0015] Further, in step (1), the injection temperature of the encapsulation shell is 300 ℃~320 ℃, and the injection pressure is 12MPa~15 MPa; In step (4), the first component and the second component are mixed in a high-pressure foaming machine at a mixing pressure of 12 MPa to 15 MPa and a mixing time of 3 s to 5 s; the in-situ foaming process is carried out at an ambient temperature of 20 ℃ to 30 ℃.

[0016] Thirdly, an application of a flame-retardant polyurethane foam firewall integrating an embedded multi-parameter intelligent detector adopts the following technical solution: Application of a flame-retardant polyurethane foam firewall with integrated embedded multi-parameter intelligent detector in fire protection isolation and safety monitoring of power cable tunnels, underground pipe corridors or substation cable trenches.

[0017] The beneficial effects of this invention are: This invention provides a flame-retardant polyurethane foam firewall integrating an embedded multi-parameter intelligent detector. By constructing an arrayed inverted conical anchoring claw and dovetail groove composite microstructure on the detector's encapsulation shell surface, combined with an in-situ foaming process for the flame-retardant polyurethane matrix, it significantly solves the technical challenges of weak interfacial bonding between rigid electronic devices and flexible foam matrices, and easy peeling during long-term service. During the polymerization and cross-linking process, the foaming system rheologically fills the aforementioned inverted structure, forming a dual high-strength mechanical interlock in both vertical and horizontal dimensions after curing. This significantly enhances the detector's pull-out resistance, effectively resisting interface failure caused by tunnel environment vibrations and differences in thermal expansion and contraction of heterogeneous materials, fundamentally eliminating the risk of circuit corrosion caused by moisture intrusion along the joint gaps. Simultaneously, this deeply embedded integrated architecture allows the MEMS sensing array to be directly located within the firewall's internal microenvironment. Utilizing the natural permeability of the open-cell foam, it can sensitively detect sudden changes in the concentration of carbon monoxide and volatile organic compounds in the early stages of material pyrolysis. Compared to traditional external smoke detectors, it achieves a "minute-level" advance warning time, successfully upgrading passive physical barrier to active state perception. In addition, the high-temperature resistant polyphenylene sulfide shell and the three-cavity physical isolation potting design, combined with the optimized water-foaming flame-retardant formula, not only ensure the structural integrity of precision electronic components when subjected to high pressure and high exothermic foaming impact, but also guarantee the long-term service stability of the system in underground high humidity and strong electromagnetic interference environments, achieving a perfect combination of fireproof sealing performance and intrinsic safety monitoring. Attached Figure Description

[0018] Figure 1 A cross-sectional structural schematic diagram of the flame-retardant polyurethane foam firewall provided by the present invention. Figure 2 A three-dimensional structural schematic diagram of the multi-parameter intelligent detector provided by the present invention; Figure 3 This is a schematic diagram of the structure of the multi-parameter intelligent detector provided by the present invention from the main viewpoint. Figure 4 This is a top-view structural diagram of the multi-parameter intelligent detector provided by the present invention. Figure 5 This is a cross-sectional structural diagram of the multi-parameter intelligent detector provided by the present invention.

[0019] Reference numerals: 100, Flame-retardant polyurethane foam firewall; 110, Flame-retardant polyurethane foam matrix; 120, Multi-parameter intelligent detector; 121, Encapsulation shell; 122, Sensing unit; 123, Control circuit unit; 124, Power supply unit; 125, Inverted conical anchor; 126, Dovetail groove; 127, Potting compound; 128, Vent array. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the specific embodiments described in this specification are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] See Figures 1 to 5 This invention provides a flame-retardant polyurethane foam firewall that integrates embedded multi-parameter intelligent detectors. This firewall system achieves a deep integration of early warning and physical isolation functions for fire hazards in enclosed spaces such as underground pipe corridors and cable tunnels.

[0022] like Figure 1 As shown, the main structure of the flame-retardant polyurethane foam firewall 100 consists of a flame-retardant polyurethane foam matrix 110 and a multi-parameter intelligent detector 120 embedded within the matrix. This structure achieves integration of the two at both the microscopic and macroscopic levels through specific interface design and in-situ foaming technology. The flame-retardant polyurethane foam matrix 110 not only undertakes the basic functions of fireproof sealing and heat insulation and flame retardancy, but also serves as the protective medium and fixed carrier for the multi-parameter intelligent detector 120. The multi-parameter intelligent detector 120 is completely or partially embedded inside the flame-retardant polyurethane foam matrix 110 in a preset array. Its spatial layout is optimized according to the fire risk level of the cable tunnel and the geometric dimensions of the monitoring area to ensure full coverage sensing of pyrolysis gases and temperature fields within the monitoring area.

[0023] like Figure 2 , Figure 3 and Figure 4As shown, the core external feature of the multi-parameter intelligent detector 120 lies in the unique shape of its encapsulation shell 121. The encapsulation shell 121 is made of polyphenylene sulfide (PPS) engineering plastic, which possesses excellent high-temperature resistance, chemical corrosion resistance, and high mechanical strength. This material was chosen based on its long-term operating temperature exceeding 200°C and its chemical inertness to reactive substances such as isocyanates generated during polyurethane foaming. To address the insufficient interfacial bonding force between the rigid shell and the flexible foam matrix due to modulus mismatch and differences in thermal expansion coefficients, the top surface of the encapsulation shell 121 is designed with multiple inverted conical anchors 125 arranged in an array. These inverted conical anchors 125 are made of metal, such as 304 stainless steel or nickel-plated carbon steel, and are integrally molded with the PPS shell using a high-precision insert injection molding process, ensuring a tight and airtight bond between the metal anchors and the plastic matrix. When the flame-retardant polyurethane foam matrix 110 is poured in liquid and foams and expands, the flowing foam slurry will rise upwards along the contour of the inverted conical anchor 125 and fill the area at its root. As the foam solidifies and sets, the solid polyurethane foam will firmly "lock" each inverted conical anchor 125, thereby providing strong pull-out resistance in the direction perpendicular to the surface of the shell.

[0024] Meanwhile, to enhance horizontal shear resistance and structural stability, the sidewalls of the encapsulation shell 121 are provided with multiple parallel dovetail grooves 126 along their length. The dovetail grooves 126 have a trapezoidal cross-section, wider at the inside and narrower at the outside. This classic mechanical interlocking design allows the foam to be squeezed into the grooves under pressure during the foaming process, and after curing, forms foam tenons that perfectly match the shape of the dovetail grooves 126. This structure enables the multi-parameter intelligent detector 120 to effectively disperse stress into the surrounding matrix through the mechanical interlocking between the foam and the groove walls when subjected to lateral vibration or impact, avoiding interface delamination caused by stress concentration. The inverted conical anchor 125 and the dovetail groove 126 together form a three-dimensional mechanical interlocking system, which ensures that the multi-parameter intelligent detector 120 can maintain a stable connection with the flame-retardant polyurethane foam matrix 110 during the decades-long service life of the underground utility tunnel, even in the face of frequent temperature and humidity changes and micro-vibration environments, thus eliminating the risk of moisture intrusion and corrosion of the internal circuit due to micro-cracks at the interface.

[0025] Combination Figure 5The cross-sectional structural diagram shows that the internal layout of the multi-parameter intelligent detector 120 follows the design principles of physical isolation and electromagnetic shielding. The internal space of the encapsulation shell 121 is divided into three physically isolated independent chambers along the horizontal direction, which are used to house the power supply unit 124, the control circuit unit 123, and the sensing unit 122, respectively. This three-chamber design not only helps to optimize the heat dissipation path, but also effectively prevents electromagnetic interference and thermal crosstalk between different functional modules. Among them, the power supply unit 124 is located in one of the chambers and is mainly composed of a high-energy-density lithium battery pack, which can provide the detector with maintenance-free power for 5 to 10 years. The middle chamber houses the control circuit unit 123, which integrates an ultra-low-power microprocessor, signal conditioning circuit, and wireless communication module (such as LoRa or NB-IoT chip), responsible for acquiring sensor signals, processing algorithms, and uploading data. To further improve the reliability of electronic components in harsh environments, the chambers containing the power supply unit 124 and the control circuit unit 123 are filled with flame-retardant and thermally conductive epoxy potting compound 127. The filling height of the potting compound 127 is strictly calculated to completely cover the top of the circuit board and components. It not only serves to insulate, prevent moisture and corrosion, but also creates an efficient heat conduction channel to quickly conduct the heat generated by the circuit operation to the encapsulation shell 121, and then dissipate it through heat exchange between the shell and the external foam substrate.

[0026] The sensing unit 122, located in the other chamber, is the core of the entire system. This sensing unit 122 is constructed on an alumina ceramic substrate, on which a microelectromechanical system (MEMS) gas sensor array and a thin-film thermocouple are integrated. The MEMS gas sensor array includes at least one electrochemical sensing unit with extremely high sensitivity to carbon monoxide, and at least one metal oxide semiconductor sensing unit sensitive to characteristic volatile organic compounds (such as alkanes and olefins) generated by cable pyrolysis. To ensure that gases from the external environment can reach the sensor surface without obstruction, a perforation array 128 is provided on the top surface of the encapsulation housing 121 corresponding to the sensing unit 122. The aperture of the perforation array 128 is precisely controlled between 2.0 mm and 3.0 mm. This size ensures rapid diffusion of gas molecules while utilizing the surface tension effect of water to prevent large condensed droplets from dripping directly onto the sensor surface. In addition, a hydrophobic and breathable ePTFE membrane (not shown in the figure) is attached below the vent, which further improves the sensor's waterproof and dustproof rating, making it reach the protection standard of IP65 or above, ensuring that it can still accurately capture early gaseous signs of fire in humid underground environments.

[0027] The chemical composition and microstructure of the flame-retardant polyurethane foam matrix 110 directly determine the overall performance of the firewall. This matrix is ​​foamed from a specific polyurethane blend through a chemical reaction. The blend consists of a first component and a second component. The first component, a mixture of polyols, is crucial for achieving high flame retardancy, low smoke density, and good dimensional stability through its formulation design. The first component contains polyether polyols with hydroxyl values ​​strictly controlled between 350 mgKOH / g and 450 mgKOH / g. This hydroxyl value range ensures that the polyurethane network generated by the reaction has a suitable crosslinking density, giving the foam sufficient mechanical strength and rigidity while avoiding brittleness caused by excessive crosslinking. The composite flame retardant is another core component of the first component, selected from one or more combinations of expanded graphite, ammonium polyphosphate, melamine, aluminum hydroxide, and dimethyl methyl phosphate. Under the high temperature of a fire, expanded graphite rapidly expands to form a worm-like carbon layer. Ammonium polyphosphate and melamine work together to produce non-flammable gases and promote char formation. Aluminum hydroxide decomposes, absorbs heat, and releases water of crystallization to cool the body. Multiple flame-retardant mechanisms work synergistically to enable the foam to quickly form a dense and hard expanded carbon layer when exposed to fire, effectively blocking heat transfer and oxygen penetration, thereby achieving the V-0 vertical burning standard and an extremely high oxygen index.

[0028] In addition, the first component also includes a catalyst, a foam stabilizer, and a blowing agent. The catalyst system is a combination of amine catalysts such as triethylenediamine and bis(dimethylaminoethyl) ether, and organotin catalysts such as dibutyltin dilaurate and stannous octoate. The amine catalysts mainly promote the foaming reaction of isocyanate and water, controlling the foam's rising speed; the organotin catalysts mainly catalyze the gelation reaction of isocyanate and hydroxyl groups, controlling the foam's skeletal strength. The precise ratio of the two catalysts adjusts the milky whitening time and the non-sticky time, perfectly matching the foaming process with the wetting and wrapping process on the surface of the multi-parameter detector 120. This ensures that the foam has sufficient fluidity to fill the gap between the dovetail groove 126 and the anchoring gripper 125, while preventing cell collapse due to slow curing. The foam stabilizer is a polysiloxane-polyoxyolefin block copolymer, which effectively reduces the surface tension of the system, emulsifies the components, and stabilizes bubble growth, resulting in a uniform and delicate closed-cell or semi-open-cell structure in the final foam. The foaming agent is deionized water. The reaction between water and isocyanate generates carbon dioxide gas, which serves as the foaming source. This all-water foaming system is not only environmentally friendly and pollution-free, but the resulting polyurea hard segments also help improve the foam's temperature resistance and dimensional stability. The second component mainly consists of polymethylene polyphenyl isocyanate (PAPI), whose NCO content and functionality have been screened to match the reactivity of the first component. During preparation, the weight ratio of the first to second components is controlled between 5.2:1 and 5.8:1. This high isocyanate index design is beneficial for generating isocyanurate ring structures with better heat resistance, further improving the fire resistance limit of the firewall.

[0029] Preparation Example 1 This embodiment describes in detail the specific preparation process of a flame-retardant polyurethane foam firewall with an integrated embedded multi-parameter intelligent detector.

[0030] First, the multi-parameter intelligent detector was prefabricated. Polyphenylene sulfide (PPS) granules were selected as the injection molding material. A 304 stainless steel inverted conical anchor, after sandblasting and cleaning, was pre-placed on the fixed mold side of the injection mold. After mold closing, insert injection molding was performed at an injection temperature of 310℃ and an injection pressure of 13.5MPa. After cooling and demolding, a packaged shell with metal anchors and side dovetail grooves was obtained. Subsequently, in a cleanroom, an alumina ceramic substrate with pre-welded MEMS gas sensors and thin-film thermocouples was installed into the sensing unit chamber of the shell. A PCB board integrating an MCU and LoRa module was installed into the control circuit chamber, and a lithium thionyl chloride battery pack was installed into the power supply chamber. Wiring connections and functional tests between the modules were completed. After passing the tests, a prepared flame-retardant and thermally conductive epoxy potting compound was injected into the power supply chamber and the control circuit chamber. After the compound leveled and completely covered the components, it was placed in a constant temperature oven and cured at 60℃ for 4 hours to obtain the finished detector.

[0031] Next, the firewall is formed as a whole. Prepare an aluminum alloy foam mold with internal dimensions matching the cross-section of the cable tunnel, and install positioning clamps at preset positions on the inner wall of the mold. Insert the three prepared multi-parameter intelligent detectors into the positioning clamps at the upper, middle, and lower heights of the mold, respectively, ensuring that the detector's vent array faces the inside of the mold cavity, and lead the antenna leads out along the mold's grooves.

[0032] The first component of the flame-retardant polyurethane mixture was prepared as follows: In a 25°C constant-temperature stirred tank, 100 parts by weight of sucrose-based polyether polyol with a hydroxyl value of 400 mgKOH / g was added. Subsequently, 30 parts of expanded graphite, 20 parts of ammonium polyphosphate, 10 parts of melamine, and 5 parts of aluminum hydroxide were added sequentially as a composite flame retardant; 1.5 parts of triethylenediamine and 0.5 parts of dibutyltin dilaurate were added as a composite catalyst; 2 parts of polysiloxane-polyoxyolefin block copolymer were added as a foam stabilizer; and 3 parts of deionized water were added as a foaming agent. A high-speed mixer was turned on and stirred at 500 rpm for 18 minutes until all components were uniformly dispersed, yielding the first component slurry.

[0033] The second component is PM-200 polymethylene polyphenyl isocyanate produced by Wanhua Chemical.

[0034] Start the high-pressure foaming machine, heat the first and second component tanks separately to 25°C, and set the mixing ratio to first component: second component = 5.5:1 (by weight). Align the mixing head with the mold inlet, and under a mixing pressure of 13MPa, the two components collide and mix at high speed in the mixing chamber for 3 seconds before being instantly injected into the bottom of the mold. The mixture rapidly undergoes a milky white reaction within the mold and begins to expand and rise. During its ascent, the foam fluid encapsulates the detector and, driven by the foaming pressure, completely fills the dovetail groove on the side of the encapsulation shell and the undercut gap of the inverted conical anchoring claw on the top surface.

[0035] After the foam system has fully reacted and matured for 15 minutes, the mold is opened, and the one-piece flame-retardant polyurethane foam fire barrier is removed. Inspection reveals that the detector is tightly bonded to the foam matrix, without gaps or defects, and the foam density is 280 kg / m³. 3 .

[0036] Preparation Example 2 This embodiment provides a preparation process under another formulation system.

[0037] The prefabrication process of the multi-parameter intelligent detector is the same as that of Example 1. The difference is that the encapsulation shell material is made of glass fiber reinforced polyphenylene sulfide, and the inverted conical anchor is made of nickel-plated carbon steel to reduce costs and improve mechanical strength.

[0038] During the firewall molding process, the mold is preheated to 40℃.

[0039] Preparation of the first component: Add 100 parts by weight of glycerol-based polyether polyol with a hydroxyl value of 350 mgKOH / g to a stirred tank. Add 25 parts expanded graphite, 25 parts ammonium polyphosphate, 5 parts melamine, and 10 parts dimethyl methyl phosphate as a composite flame retardant. Adjust the catalyst to 1.2 parts bis(dimethylaminoethyl) ether and 0.8 parts stannous octoate to accommodate the lower hydroxyl value and delay gel time, facilitating foam flow in large molds. Add 2.5 parts foam stabilizer and 3.5 parts water as a blowing agent. Mix the above components thoroughly at 600 rpm for 20 minutes.

[0040] The second component is BASF's M20S polymeric MDI.

[0041] The mixing ratio of the high-pressure foaming machine was set to 5.2:1 for the first component and 15 MPa for the second component. The mixing pressure was set to 15 MPa and the mixing time to 4 seconds. The mixture was then injected into a mold pre-installed with five detectors. Due to the catalyst adjustment, the foam rose more slowly but had better fluidity, fully filling the complex corners of the mold and the microstructure of the detectors.

[0042] The ambient temperature was controlled at 30℃, and the curing time was extended to 20 minutes before demolding. The resulting fireproof foam had finer pores, and the oxygen index reached 48.5% as tested.

[0043] Preparation Example 3 This embodiment provides a preparation process that meets the requirements for high flame retardancy.

[0044] In the prefabrication of the multi-parameter intelligent detector, the aperture of the air vent array was adjusted to 2.0 mm to meet the protection requirements of higher dust environments.

[0045] The first component formulation consists of 100 parts by weight of sorbitol-based polyether polyol with a hydroxyl value of 450 mgKOH / g, providing higher crosslinking density and heat resistance. The flame retardant system is reinforced with 40 parts expanded graphite, 15 parts ammonium polyphosphate, and 15 parts aluminum hydroxide. The catalyst uses 1.8 parts triethylenediamine and 0.3 parts dibutyltin dilaurate, along with 1.8 parts stabilizer and 2.8 parts water. Stir at 400 rpm for 15 min.

[0046] The second component is the same as in Example 1.

[0047] Foaming process: The mixing ratio was adjusted to component 1: component 2 = 5.8:1 to increase the isocyanate index and generate more heat-resistant isocyanurate structures. Mixing pressure: 12 MPa; mixing time: 5 s.

[0048] During the mold fixing process, the detector is fixed at a 45° angle to better vent air by utilizing the shear force when the foam rises, thus preventing air pockets from forming at the anchoring base.

[0049] The foam was foamed at 20℃ and cured for 12 minutes before demolding. The resulting firewall exhibited high hardness, a dense surface crust, and a crisp sound when tapped, demonstrating excellent physical and mechanical properties.

[0050] Application Example 1 The flame-retardant polyurethane foam firewall, which integrates embedded multi-parameter intelligent detectors as described in Example 1, was installed in the high-voltage cable joint section of a 110kV underground cable tunnel in a city. During installation, the firewall module was tightly filled into the tunnel cross-section, and polyurethane foam was used to seal the surrounding gaps. Subsequently, the detector power was turned on, and the detector automatically networked and connected to the host computer system of the tunnel monitoring center.

[0051] During the three-month trial operation, the tunnel section experienced a cable overload and overheating event. When the surface temperature of the cable joint abnormally increased due to increased contact resistance, causing slight pyrolysis of the insulation layer, the multi-parameter intelligent detector integrated inside the firewall sensitively detected the slow rise in the carbon monoxide concentration in the air from a baseline of 0 ppm to 15 ppm, while simultaneously monitoring abnormal fluctuations in the concentration of volatile organic compounds. At this time, no visible smoke had yet formed in the tunnel, and traditional smoke detectors were inactive. The detector of this invention, combined with a temperature change rate algorithm, determined that this was an early fire hazard and sent a level-two warning signal to the monitoring center via the wireless network. Upon receiving the alarm, maintenance personnel quickly rushed to the scene, confirmed the overheated area using an infrared thermal imager, and performed an emergency power outage, successfully preventing a potential cable fire.

[0052] Application results show that the firewall system provided by this invention can detect fire hazards approximately 15 minutes earlier than traditional external detectors, achieving true prevention before fires start. Furthermore, during subsequent tunnel flushing and maintenance operations, the detector withstood the scouring of high-pressure water jets without exhibiting water ingress failure or detachment, demonstrating the reliability of its encapsulation structure and mechanical interlocking design.

[0053] Application Example 2 The firewall prepared in Example 2 was applied to the low-voltage electrical compartment of an underground utility tunnel in a coastal area. This tunnel experiences humidity levels above 90% year-round and faces the risk of seawater intrusion, making it a highly corrosive environment.

[0054] After installation, a simulated fire resistance test was conducted on the firewall. A standard woodpile was ignited in a controlled area of ​​the utility tunnel to simulate cable burning. As the fire spread, flames directly licked the surface of the firewall. Thanks to the efficient action of expanded graphite and the compounded flame retardant, a dense expanded char layer over 3 cm thick quickly formed on the fire-exposed surface of the firewall, effectively blocking the penetration of the flames and the backward transfer of heat. After 60 minutes of continuous burning, the temperature of the unexposed surface of the firewall remained below 80°C, without any collapse or fire penetration, meeting the fire resistance integrity and insulation requirements stipulated by national standards.

[0055] In the early stages of the fire, despite significant water vapor interference, the embedded detector accurately distinguished between the fire's characteristic gases and ambient humidity interference, issuing an alarm signal within 45 seconds of ignition. After the fire was extinguished, inspection revealed that although the surface foam of the firewall had carbonized, the detectors embedded deep within remained firmly attached to the uncarbonized substrate layer thanks to deep anchoring, without detaching. Furthermore, after cleaning the surface carbon deposits, testing showed that its core circuitry functioned normally, verifying the system's survivability and structural stability under extreme fire conditions.

[0056] Application Example 3 The high-hardness firewall prepared in Example 3 was applied to the cable interlayer of a substation located beneath a subway line. This area is subject to low-frequency vibrations from subway train operation over a long period.

[0057] To verify the system's seismic performance and long-term stability, continuous monitoring of the application scenario was conducted for one year. During this year, the firewall underwent tens of thousands of vibration cycles and temperature variations exceeding 30°C between winter and summer. At the end of the monitoring period, a pull-out test was performed on the embedded detector using a tensile tester. The test results showed that no visible cracks or loosening appeared at the interface between the detector and the foam matrix. Even after applying a tensile force of 500N, the detector remained stable until the surrounding foam material was damaged by increased tension, and the interface did not separate. This fully demonstrates that the double mechanical interlocking structure composed of the inverted conical anchor and the dovetail groove can effectively resist long-term mechanical vibration fatigue and thermal expansion and contraction stress.

[0058] Furthermore, during this year, the system recorded and uploaded thousands of sets of environmental data. The data was continuous and without packet loss, and the sensor baseline drift was less than 2%, demonstrating that the three-cavity physical isolation and potting process provided perfect protection for electronic components, shielding them from electromagnetic interference and moisture corrosion in the underground environment. This application example confirms the feasibility of the invention for long-term maintenance-free operation in complex mechanical and electromagnetic environments, significantly reducing the operation and maintenance costs for the power sector.

[0059] For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, but obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this invention.

Claims

1. A flame-retardant polyurethane foam firewall integrating a multi-parameter intelligent detector, characterized in that, The device includes a flame-retardant polyurethane foam matrix and at least one multi-parameter intelligent detector embedded within the flame-retardant polyurethane foam matrix. The multi-parameter intelligent detector includes an encapsulation shell and a sensing unit, a control circuit unit, and a power supply unit disposed within the encapsulation shell. The top surface of the encapsulation shell is provided with a plurality of inverted conical anchor claws arranged in an array, and the sidewalls of the encapsulation shell are provided with dovetail grooves along the length direction. The flame-retardant polyurethane foam matrix is ​​foamed in situ to fill and enclose the root undercut area of ​​the inverted conical anchor claws and the inner cavity of the dovetail grooves, thereby forming a double mechanical interlocking structure between the multi-parameter intelligent detector and the flame-retardant polyurethane foam matrix in the vertical and horizontal directions.

2. The flame-retardant polyurethane foam firewall with integrated multi-parameter intelligent detector according to claim 1, characterized in that, The flame-retardant polyurethane foam matrix is ​​generated by the reaction of a first component and a second component; wherein the first component includes polyether polyol, composite flame retardant, catalyst, foam stabilizer and blowing agent, and the second component includes isocyanate.

3. The flame-retardant polyurethane foam firewall with integrated multi-parameter intelligent detector according to claim 2, characterized in that, The composite flame retardant is selected from one or more of expanded graphite, ammonium polyphosphate, melamine, aluminum hydroxide, and dimethyl methyl phosphate; the catalyst is selected from one or more of triethylenediamine, bis(dimethylaminoethyl) ether, dibutyltin dilaurate, and stannous octoate; the foam stabilizer is a polysiloxane-polyoxyolefin block copolymer; the foaming agent is water; the hydroxyl value of the polyether polyol is 350 mgKOH / g~450 mgKOH / g; the weight ratio of the first component to the second component is (5.2~5.8):

1.

4. The flame-retardant polyurethane foam firewall with integrated multi-parameter intelligent detector according to claim 1, characterized in that, The packaging shell is made of polyphenylene sulfide; the inverted conical anchor claw is made of metal and is implanted into the top surface of the packaging shell through an insert injection molding process, and the height of the inverted conical anchor claw protruding from the surface of the packaging shell is 3.0 mm to 5.0 mm.

5. The flame-retardant polyurethane foam firewall with integrated multi-parameter intelligent detector according to claim 4, characterized in that, The encapsulation shell has three physically isolated independent chambers along the horizontal direction, which are used to house the power supply unit, the control circuit unit, and the sensing unit, respectively. The three independent chambers are filled with flame-retardant and thermally conductive epoxy potting compound, and the filling height of the potting compound covers the top of the control circuit unit and the power supply unit.

6. The flame-retardant polyurethane foam firewall with integrated multi-parameter intelligent detector according to claim 5, characterized in that, The sensing unit includes an alumina ceramic substrate, on which a MEMS gas sensor array and a thin-film thermocouple are integrated; the MEMS gas sensor array includes an electrochemical sensing unit sensitive to carbon monoxide and a metal oxide semiconductor sensing unit sensitive to volatile organic compounds; the top surface of the package housing is provided with an array of vent holes corresponding to the sensing unit, and the vent hole array has a diameter of 2.0 mm to 3.0 mm.

7. A method for preparing a flame-retardant polyurethane foam firewall with an integrated multi-parameter intelligent detector as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step (1): Prepare a packaged shell with inverted conical anchoring claws by insert injection molding process, assemble electronic components and pot the shell to obtain the multi-parameter intelligent detector; Step (2): Fix the multi-parameter intelligent detector to a predetermined position on the inner wall of the foaming mold through the positioning structure on its surface; Step (3): Prepare the first and second components of the flame-retardant polyurethane composite material respectively. Step (4): After mixing the first component and the second component, the mixture is poured into the foaming mold. During the foaming and expansion process, the mixture flows through the surface of the encapsulation shell and uses its fluidity to penetrate and fill the undercut gap and side wall dovetail groove of the inverted conical anchor claw. Step (5): After the foam system has matured, demold to form an integrated flame-retardant polyurethane foam firewall.

8. The preparation method according to claim 7, characterized in that, In step (3), the preparation of the first component includes the following steps: The first component is obtained by stirring polyether polyol, composite flame retardant, catalyst, foam stabilizer and foaming agent at a speed of 400 rpm to 600 rpm for 15 min to 20 min at a temperature of 23 ℃ to 27 ℃.

9. The preparation method according to claim 7, characterized in that, In step (1), the injection temperature of the encapsulation shell is 300 ℃~320 ℃, and the injection pressure is 12 MPa~15 MPa; In step (4), the first component and the second component are mixed in a high-pressure foaming machine at a mixing pressure of 12 MPa to 15 MPa and a mixing time of 3 s to 5 s; the in-situ foaming process is carried out at an ambient temperature of 20 ℃ to 30 ℃.

10. The application of a flame-retardant polyurethane foam firewall with an integrated embedded multi-parameter intelligent detector as described in any one of claims 1 to 6 in fire protection isolation and safety monitoring of power cable tunnels, underground pipe corridors or substation cable trenches.

Images