Anti-scratching and Anti-cracking thermo-sensitive line and preparation method therefor

Abstract

An anti-scratching and anti-cracking thermo-sensitive line and a preparation method therefor. The exterior of a thermo-sensitive line core is coated with a layer of modified line sheath, and then is wrapped with a layer of wrapping film, such that the thermo-sensitive line sheath is of a double-layer structure. The outermost wrapping film can be resistant to scratching, and prevent the problem of the thermo-sensitive line core being affected with damp and failing due to the breakage of the line sheath caused by scratching. Moreover, a toughening agent and an auxiliary material are added to the inner modified line sheath during preparation, so that the toughness of the line sheath is improved while ensuring thermal conductivity and not affecting a starting temperature interval of the thermo-sensitive line, preventing the problem of line sheath cracking due to excessive bending during mounting of the thermo-sensitive line, and thus improving the use practicability of the thermo-sensitive line in a use scene and prolonging the service life.

Description

A scratch-resistant and crack-resistant thermal wire and its preparation method Technical Field

[0001] The invention belongs to the technical field of fire fighting and extinguishing, and particularly relates to a scratch-proof and crack-proof thermal wire and a preparation method thereof. Background Art

[0002] A thermistor wire is a linear structure connected to a fire extinguishing device and serves as an initiator for automatic fire extinguishing devices. It consists of a multi-wire or single-wire core covered with a heat-sensitive material. When the ambient temperature reaches the thermistor wire's activation temperature, the wire spontaneously ignites, triggering the connected fire extinguishing device to activate. This enables non-electrical fire extinguishing and thus fire control. Its advantages include no ignition, no deflagration, and a stable burning rate, making it a key initiating element in automatic firefighting devices. Thermistor wire operates on the principle that its inherent ignition temperature is relatively low, within 170°C ± 20°C. When a fire occurs in the application area and the ambient temperature rises to the thermistor wire's sensing temperature, the wire begins to burn, thereby activating the firefighting device.

[0003] The thermal wires currently used in the market are mainly composed of two parts: the core and the sheath. The core is used for induction activation, while the sheath is used for moisture-proofing. However, there are two main problems with existing thermal wires in actual applications. On the one hand, the sheath of the thermal wire used is very thin, with a thickness of only 0.2-0.5mm, and no protective treatment is done. On the other hand, the sheath of the thermal wire is made of polyethylene material. Polyethylene will age, discolor, crack, become brittle or powder under the influence of the atmosphere, sunlight and oxygen, and lose its mechanical properties. At the molding processing temperature, the melt viscosity will also decrease due to oxidation, causing discoloration and stripes. No toughening treatment is done during the preparation process, resulting in a brittle sheath after molding. In actual application, due to the complexity of the installation environment, it is easy to be scratched and damaged, which will cause the sheath to break and the core to be exposed. When the thermal wire is in a warm and humid environment for a long time, the core is easily affected by moisture and fails, making it impossible for the fire-fighting equipment to start normally after a fire, causing huge losses and disasters. Therefore, there is an urgent need for a thermal wire that is moisture-proof and can prevent scratches during installation that may cause the wire sheath to break.

[0004] Chinese patent CN113912465A discloses a moisture-proof and waterproof thermal wire and its preparation method, in which a sleeve is wrapped around the outside of the thermal core to make the thermal wire moisture-proof and waterproof. Chinese patent CN111689824A discloses a thermal wire and its preparation method, in which a temperature-sensitive combustible agent, a stabilizer, an anti-inflammatory agent, a performance regulator and a solvent are mixed and plasticized and then pressed into a medicine strip. The medicine strip is dried, sliced ​​and dried to obtain a thermal wire. The thermal wire prepared by this method has good moisture resistance, small flame and low false start rate.

[0005] The thermal wire prepared by the above method selectively coats the wire core, and the purpose of the coating is to improve the moisture-proof and waterproof performance of the thermal wire, but the problem of preventing the thermal wire from being scratched and cracked due to excessive bending is not taken seriously and solved.

[0006] Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a scratch-proof and crack-proof thermal wire and a preparation method thereof.

[0008] In order to achieve the above-mentioned object, the present invention provides a scratch-resistant and crack-resistant thermal wire, wherein the thermal wire sheath comprises a thermal wire core, a modified wire sheath and a wrapping film.

[0009] Preferably, the modified cord sheath is composed of 90-97% high-density polyethylene, 1-5% auxiliary materials and 2-5% toughening agent.

[0010] Further preferably, the auxiliary material is one or more of hexagonal boron nitride, aluminum nitride, spherical alumina, graphene, nano-silicon dioxide, nano-calcium carbonate, and carbon nanotubes.

[0011] Preferably, the toughening agent is one or more of EPDM rubber, EPDM rubber, butadiene rubber, natural rubber, isobutylene rubber, and nitrile butadiene rubber.

[0012] Preferably, the wrapping film is any one of a graphene film, a carbon nanotube film, a carbon composite thermally conductive film, and a cellulose-based thermally conductive film.

[0013] Further preferably, the thickness of the wrapping film is 0.3 mm.

[0014] Preferably, the heat-sensitive wire core is a cotton thread, a dacron thread, or a polyester thread. Preferably, a heat-sensitive material, such as nitrocellulose, is attached to the heat-sensitive wire core.

[0015] The present invention also provides a method for preparing the scratch-resistant and crack-resistant thermal wire, comprising the following steps:

[0016] (1) adding polyethylene, auxiliary materials and toughening agent into a melt mixer in sequence, and melt-stirring to obtain a mixture; wherein the melt-stirring conditions are 130° C., 20-60 rpm, and the stirring time is 0.5-1 h;

[0017] (2) coating the mixture on the surface of the thermal wire core and cooling it to obtain a wrapped thermal wire; wherein the coating thickness of the mixture is 0.3 mm;

[0018] (3) preparing an adhesive and applying it to the wrapping film;

[0019] (4) The wrapping film coated with adhesive is placed in a wrapping machine, and the once wrapped thermal wire is wrapped a second time to obtain a formed thermal wire.

[0020] The beneficial effects of the present invention are as follows: by adding a toughening agent and auxiliary materials to the sheath of a conventional plastic thermal wire, a toughened modified sheath is prepared, and the modified sheath is coated on the surface of the thermal wire core, so that the thermal wire can be strengthened and protected while maintaining the original starting temperature range of the thermal wire, thereby preventing the thermal wire from breaking when the sheath is bent, thereby preventing the exposed wire core from failing due to moisture in the application environment, and ensuring that the fire extinguishing device is normally started after a fire occurs.

[0021] By wrapping a layer of wrapping film on the surface of the thermal wire after the modified wire skin is plastic-coated, the original starting temperature range of the thermal wire is maintained while preventing the thermal wire skin from breaking due to scratching. At the same time, one side of the wrapping film has a 0.05-0.1mm adhesive. The adhesive can tightly bond the wire skin and the wrapping film, enhance the protective effect of the wrapping, and further improve the anti-scratch effect of the thermal wire. DETAILED DESCRIPTION

[0022] The technical solutions of the present invention are further explained below with reference to specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention shall be determined by the claims. Any modifications or substitutions made to the technical solutions of the present invention by those skilled in the art without creative effort shall fall within the scope of protection of the present invention.

[0023] In the following examples, the chemical formula of the high-density polyethylene is (C2H4)n, where n is 7000-15000, the molecular weight is 200,000-400,000, and the density at 25°C is 0.940-0.976 g / cm 3 .

[0024] Example 1

[0025] (1) mixing hexagonal boron nitride and nano-calcium carbonate in a mass ratio of 3:1 to obtain an auxiliary material;

[0026] (2) turning on the melt mixer, heating to 130° C., adding 92% of high-density polyethylene masterbatch and 3% of the auxiliary material prepared in step (1) while stirring, and then adding 5% of butadiene rubber, and continuing to stir and mix for 30 minutes to obtain a mixture; wherein the stirring speed is 30 rpm;

[0027] (3) transferring the mixture obtained in step (2) into the hopper of a screw extruder, then opening the feed port, extruding the mixture under the rotation of the screw, coating the mixture on the surface of the wire core, and cooling the mixture at room temperature to obtain a single-wrapped thermal wire, wherein the coating thickness is 0.3 mm;

[0028] (4) Gelatin and water are prepared into an adhesive in a weight ratio of 1:1 and placed in a coating machine. A carbon composite thermal conductive film with a thickness of 0.3 mm is coated through the coating machine. The coated carbon composite thermal conductive film is passed through a wrapping machine to wrap the once-wrapped thermal wire obtained in step (3) to obtain a formed thermal wire.

[0029] Example 2

[0030] (1) mixing aluminum nitride and nano-silicon dioxide in a mass ratio of 2:1 to obtain an auxiliary material;

[0031] (2) turning on the melt mixer, heating to 130° C., adding 95% of the high-density polyethylene masterbatch and 2% of the auxiliary material prepared in step (1) while stirring, and then adding 3% of EPDM rubber, and continuing to stir and mix for 30 minutes to obtain a mixture; wherein the stirring speed is 30 rpm;

[0032] (3) transferring the mixture obtained in step (2) into the hopper of a screw extruder, then opening the feed port, extruding the mixture under the rotation of the screw, coating the mixture on the surface of the wire core, and cooling the mixture at room temperature to obtain a single-wrapped thermal wire, wherein the coating thickness is 0.3 mm;

[0033] (4) Polyvinyl alcohol and water are prepared into an adhesive in a weight ratio of 1:2 and placed in a coating machine. A graphene thermal conductive film with a thickness of 0.3 mm is coated through the coating machine. The coated graphene thermal conductive film is passed through a wrapping machine to wrap the once-wrapped thermal wire obtained in step (3) to obtain a formed thermal wire.

[0034] Example 3

[0035] (1) mixing graphene and carbon nanotubes in a mass ratio of 1:1 to obtain an auxiliary material;

[0036] (2) turning on the melt mixer, heating to 130° C., adding 91% of the high-density polyethylene masterbatch and 2% of the auxiliary material prepared in step (1) while stirring, and then adding 7% of the isobutylene rubber, and continuing to stir and mix for 30 minutes to obtain a mixture; wherein the stirring speed is 30 rpm;

[0037] (3) transferring the mixture obtained in step (2) into the hopper of a screw extruder, then opening the feed port, extruding the mixture under the rotation of the screw, coating the mixture on the surface of the wire core, and cooling the mixture at room temperature to obtain a single-wrapped thermal wire, wherein the coating thickness is 0.3 mm;

[0038] (4) Polyacrylamide and water are mixed into an adhesive in a weight ratio of 1:1 and placed in a coating machine. A cellulose-based thermal conductive film with a thickness of 0.3 mm is coated through the coating machine. The coated cellulose-based thermal conductive film is passed through a wrapping machine to wrap the once-wrapped thermal wire obtained in step (3) to obtain a formed thermal wire.

[0039] Comparative Example 4

[0040] (1) Turn on the melt mixer, heat it to 130° C., add 91% polyethylene masterbatch and 2% spherical alumina while stirring, then add 7% EPDM rubber, and continue stirring and mixing for 30 minutes to obtain a mixture; wherein the stirring speed is 30 rpm;

[0041] (2) transferring the mixture obtained in step (1) into the hopper of a screw extruder, then opening the feed port, extruding the mixture under the rotation of the screw, coating the mixture on the surface of the wire core, and cooling at room temperature to obtain a once-wrapped thermal wire, wherein the coating thickness is 0.3 mm;

[0042] (3) Ethyl cellulose and water are mixed in a weight ratio of 2:1 to prepare an adhesive, which is placed in a coating machine. Carbon nanotubes with a thickness of 0.3 mm are coated through the coating machine. The coated carbon nanotubes are passed through a wrapping machine to wrap the once-wrapped thermal wire obtained in step (2) to obtain a formed thermal wire.

[0043] Comparative Example 1

[0044] The thermal wire with a wire sheath of 0.3 mm is obtained by directly using polyethylene melt coating.

[0045] Comparative Example 2

[0046] The thermosensitive wire with a wire skin of 0.3 mm obtained by directly melt-coating high-density polyethylene is passed through a wrapping machine, and a graphene film with a thickness of 0.3 mm is wrapped on the surface of the thermosensitive wire to prepare a formed thermosensitive wire.

[0047] Comparative Example 3

[0048] The thickness of the commercially available thermal wire sheath is 0.6 mm.

[0049] Comparative Example 4

[0050] (1) mixing hexagonal boron nitride and nano-calcium carbonate in a mass ratio of 3:1 to obtain an auxiliary material;

[0051] (2) turning on the melt mixer, heating to 130° C., adding 92% of high-density polyethylene masterbatch and 3% of the auxiliary material prepared in step (1) while stirring, and then adding 5% of butadiene rubber, and continuing to stir and mix for 30 minutes to obtain a mixture; wherein the stirring speed is 30 rpm;

[0052] (3) The mixture obtained in step (2) is transferred to the hopper of a screw extruder, and then the feed port is opened. The mixture is extruded under the rotation of the screw, coated on the surface of the wire core, and cooled at room temperature to obtain a thermal wire, wherein the coating thickness is 0.3 mm;

[0053] Results test:

[0054] The formed thermal wires prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to a scratch test and a 180° bending test on a flat plate with a surface roughness of Ra50. The morphological changes of the thermal wires were observed. The results are shown in Table 1.

[0055] The formed thermal wires prepared in Examples 1-3 and Comparative Examples 1-3 were placed in an oven to conduct an ignition temperature test. The results are shown in Table 1:

[0056] Table 1 Characterization data and effect data of thermosensitive wires prepared with different formulas

[0057] The results show that compared with the thermal wire wrapped with a conventional 0.3mm wire sheath in Comparative Example 1 and the thermal wire wrapped with a 0.6mm wire sheath in Comparative Example 3, the thermal wire with a double-layer structure prepared in Examples 1-4 has scratches on the wrapping film after the scratch and bending tests, but the internal wire sheath is intact and has no cracks, and after a layer of film is wrapped around the outer surface of the wire sheath, it has little effect on the ignition temperature of the thermal wire core, and can still ensure that the thermal wire can be started normally; when a thicker wire sheath is used in Comparative Example 3, the ignition temperature of the thermal wire increases significantly, reaching 194°C, which has a great impact on the startup of the automatic fire-fighting device.

Claims

1. A scratch and crack resistant thermal wire, characterized in that: The heat-sensitive wire sheath consists of a heat-sensitive wire core, a modified wire sheath and a wrapping film.

2. The anti-scratch and anti-cracking thermal wire according to claim 1, characterized in that: The modified wire sheath consists of 90-97% high-density polyethylene, 1-5% auxiliary materials and 2-5% toughening agent.

3. The anti-scratch and anti-cracking thermal wire according to claim 2, characterized in that: The auxiliary material is one or more of hexagonal boron nitride, aluminum nitride, spherical aluminum oxide, graphene, nano silicon dioxide, nano calcium carbonate, and carbon nanotubes.

4. The anti-scratch and anti-cracking thermal wire according to claim 2, characterized in that: The toughening agent is any one of EPDM rubber, EPDM rubber, butadiene rubber, natural rubber, isobutylene rubber and nitrile butadiene rubber.

5. The anti-scratch and anti-cracking thermal wire according to claim 1, characterized in that: The wrapping film is any one of a graphene film, a carbon nanotube film, a carbon composite thermally conductive film, and a cellulose-based thermally conductive film.

6. The scratch and crack resistant thermal wire according to claim 5, characterized in that: The thickness of the wrapping film is 0.3 mm.

7. The scratch and crack resistant thermal wire according to claim 1, characterized in that: The heat-sensitive wire core is cotton wire, polyester wire or dacron wire.

8. The anti-scratch and anti-cracking thermal wire according to claim 1, characterized in that: The heat-sensitive wire sheath and the wrapping film are bonded by adhesive.

9. The anti-scratch and anti-cracking thermal wire according to claim 8, wherein the adhesive is prepared by dissolving any one of alginate, gelatin, gum arabic, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose, LA132, polyvinyl alcohol, polyethylene oxide, polyethylene glycol and polyacrylamide in water, and the ratio of the adhesive to water is 1:2-3:

1.

10. A method for preparing the anti-scratch and anti-cracking thermal wire according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) adding polyethylene, auxiliary materials and toughening agent in a melt mixer in sequence, and melting and stirring to obtain a mixture; wherein the melting and stirring conditions are 130° C., 20-60 rpm, and the stirring time is 0.5-1 h; (2) coating the mixture on the surface of the thermal wire core and cooling to obtain a thermal wire wrapped once; wherein the coating thickness of the mixture is 0.3 mm; (3) preparing an adhesive and applying it onto the wrapping film; (4) placing the wrapping film coated with adhesive in a wrapping machine, and performing a second wrapping on the thermal wire wrapped once, thereby obtaining a formed thermal wire.

Images