CN116884690A - Flame-retardant sheath structure of radiation type leaky coaxial cable and manufacturing method - Google Patents
Flame-retardant sheath structure of radiation type leaky coaxial cable and manufacturing method Download PDFInfo
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- CN116884690A CN116884690A CN202311008976.9A CN202311008976A CN116884690A CN 116884690 A CN116884690 A CN 116884690A CN 202311008976 A CN202311008976 A CN 202311008976A CN 116884690 A CN116884690 A CN 116884690A
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- 239000003063 flame retardant Substances 0.000 title claims abstract description 100
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 15
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- 239000000126 substance Substances 0.000 claims abstract description 19
- 229920000098 polyolefin Polymers 0.000 claims abstract description 5
- 238000001125 extrusion Methods 0.000 claims description 50
- 239000012796 inorganic flame retardant Substances 0.000 claims description 22
- 229920005989 resin Polymers 0.000 claims description 20
- 239000011347 resin Substances 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 12
- 239000005038 ethylene vinyl acetate Substances 0.000 claims description 6
- 229920000642 polymer Polymers 0.000 claims description 6
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 5
- 229920000092 linear low density polyethylene Polymers 0.000 claims description 5
- 239000004707 linear low-density polyethylene Substances 0.000 claims description 5
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical group [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 5
- 239000000347 magnesium hydroxide Substances 0.000 claims description 5
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims description 5
- YFYIWIZSIVZILB-UHFFFAOYSA-N N.[P] Chemical group N.[P] YFYIWIZSIVZILB-UHFFFAOYSA-N 0.000 claims description 4
- 239000004743 Polypropylene Substances 0.000 claims description 4
- 239000005042 ethylene-ethyl acrylate Substances 0.000 claims description 4
- 229920001903 high density polyethylene Polymers 0.000 claims description 4
- 239000004700 high-density polyethylene Substances 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 11
- 229910052799 carbon Inorganic materials 0.000 abstract description 11
- 238000002485 combustion reaction Methods 0.000 abstract description 9
- 230000000704 physical effect Effects 0.000 abstract description 7
- 239000000463 material Substances 0.000 description 12
- 239000004020 conductor Substances 0.000 description 11
- 239000004114 Ammonium polyphosphate Substances 0.000 description 8
- 235000019826 ammonium polyphosphate Nutrition 0.000 description 8
- 229920001276 ammonium polyphosphate Polymers 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 7
- 239000001301 oxygen Substances 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 7
- 229920000877 Melamine resin Polymers 0.000 description 6
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 6
- WXZMFSXDPGVJKK-UHFFFAOYSA-N pentaerythritol Chemical compound OCC(CO)(CO)CO WXZMFSXDPGVJKK-UHFFFAOYSA-N 0.000 description 6
- 229920001684 low density polyethylene Polymers 0.000 description 5
- 239000004702 low-density polyethylene Substances 0.000 description 5
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 description 5
- -1 polyethylene Polymers 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 238000010998 test method Methods 0.000 description 5
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- 239000004698 Polyethylene Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000005886 esterification reaction Methods 0.000 description 4
- 229920000573 polyethylene Polymers 0.000 description 4
- QLZJUIZVJLSNDD-UHFFFAOYSA-N 2-(2-methylidenebutanoyloxy)ethyl 2-methylidenebutanoate Chemical compound CCC(=C)C(=O)OCCOC(=O)C(=C)CC QLZJUIZVJLSNDD-UHFFFAOYSA-N 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- QYMGIIIPAFAFRX-UHFFFAOYSA-N butyl prop-2-enoate;ethene Chemical compound C=C.CCCCOC(=O)C=C QYMGIIIPAFAFRX-UHFFFAOYSA-N 0.000 description 3
- 229920006245 ethylene-butyl acrylate Polymers 0.000 description 3
- 229920006244 ethylene-ethyl acrylate Polymers 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 241001391944 Commicarpus scandens Species 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 206010051246 Photodermatosis Diseases 0.000 description 2
- YUWBVKYVJWNVLE-UHFFFAOYSA-N [N].[P] Chemical compound [N].[P] YUWBVKYVJWNVLE-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000032050 esterification Effects 0.000 description 2
- 238000007706 flame test Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
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- 230000004048 modification Effects 0.000 description 2
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- 239000002245 particle Substances 0.000 description 2
- 230000008845 photoaging Effects 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
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- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
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- 238000002844 melting Methods 0.000 description 1
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- 230000003287 optical effect Effects 0.000 description 1
- 229920013716 polyethylene resin Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
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- 230000008569 process Effects 0.000 description 1
- 238000007665 sagging Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/29—Protection against damage caused by extremes of temperature or by flame
- H01B7/295—Protection against damage caused by extremes of temperature or by flame using material resistant to flame
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B11/00—Communication cables or conductors
- H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/06—Insulating conductors or cables
- H01B13/14—Insulating conductors or cables by extrusion
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/22—Sheathing; Armouring; Screening; Applying other protective layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/22—Sheathing; Armouring; Screening; Applying other protective layers
- H01B13/24—Sheathing; Armouring; Screening; Applying other protective layers by extrusion
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/29—Protection against damage caused by extremes of temperature or by flame
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Insulated Conductors (AREA)
Abstract
The invention discloses a radiation type leaky coaxial cable flame-retardant sheath structure and a manufacturing method, wherein the radiation type leaky coaxial cable flame-retardant sheath structure comprises: the inner sheath and the outer sheath are sleeved on the inner sheath and are abutted against the inner sheath; wherein: the inner sheath is an inorganic filling type flame-retardant polyolefin sheath, and the outer sheath is a chemical expansion type flame-retardant sheath. The invention greatly improves the shell forming property of the combustion matter of the inner sheath, and the inner sheath forms a carbon shell after combustion when the leaky coaxial cable burns, so that flame can be isolated from entering the interior of the leaky coaxial cable, the flame retardant efficiency of the outer sheath is high, and meanwhile, the invention can keep better mechanical and physical properties and can improve the flame retardant property of the flame retardant sheath.
Description
Technical Field
The invention relates to the technical field of cable equipment, in particular to a radiation type leaky coaxial cable flame-retardant sheath structure and a manufacturing method.
Background
The leaky coaxial cable is composed of an inner conductor (copper or aluminum), a polyethylene insulating layer, an outer conductor and a flame-retardant sheath from inside to outside, wherein gaps or slotted holes are formed in the outer conductor, a small part of electromagnetic energy between the inner conductor and the outer conductor is leaked out of the slotted holes, electromagnetic waves in surrounding space enter the interior of the leaky coaxial cable, the leaky coaxial cable is widely used in closed or semi-closed long and narrow spaces such as subway tunnels, high-speed railways, highway tunnels, mines, high-rise elevators, underground markets and the like, public safety problems are related to the use occasions, and the flame-retardant performance requirement on the leaky coaxial cable is high. Flame-retardant polyethylene is mostly adopted for the flame-retardant sheath in the prior art to achieve the flame-retardant purpose, namely, inorganic flame retardant is added into polyethylene resin. However, when a fire disaster occurs, flame generated during combustion of the leaky coaxial cable can ignite the inner polyethylene insulating layer through the slotted hole formed in the outer conductor, so that the fire disaster spreads, and the current leaky coaxial cable flame-retardant sheath structure cannot achieve the purpose of effective flame retardance.
Disclosure of Invention
The invention aims to solve the technical problems that: in order to solve the technical problem of lower flame retardant property of the existing flame retardant sheath, the invention provides the flame retardant sheath structure of the radiation leaky coaxial cable and the manufacturing method, and the flame retardant property of the flame retardant sheath can be improved by improving the flame retardant sheath.
The technical scheme adopted for solving the technical problems is as follows: a radiation type leaky coaxial cable flame retardant sheath structure, comprising: the outer sheath is sleeved on the inner sheath and is abutted against the inner sheath; wherein: the inner sheath is an inorganic filling type flame-retardant polyolefin sheath, and the outer sheath is a chemical expansion type flame-retardant sheath.
Therefore, the shell forming property of the combustion matters of the inner sheath is greatly improved, the inner sheath forms a carbon shell after being combusted when the leaky coaxial cable is combusted, flame can be isolated from entering the interior of the leaky coaxial cable, the flame retardant efficiency of the outer sheath is high, meanwhile, the better mechanical and physical properties can be kept, and the flame retardant property of the flame retardant sheath can be improved.
Further, the radial sections of the inner sheath and the outer sheath are circular, the inner diameter of the inner sheath is d1, the outer diameter of the inner sheath is d2, and the inner diameter of the outer sheath is d2, and the outer diameter of the outer sheath is d3.
Further, the thickness of the inner sheath is H1, the radial sectional area is S1, the thickness of the outer sheath is H2, the radial sectional area is S2, H1/H2 is more than 1.5 and less than 2.5, S1/S2 is less than H1/H2, wherein: h1 =d2-d 1, h2=d3-d 2, s1=pi ((d 2) 2 －(d1) 2 )，S2＝π((d3) 2 －(d2) 2 ). Therefore, the cost of the outer sheath flame retardant is higher than that of the inner sheath flame retardant, the material cost of the flame retardant sheath can be reduced due to the thicker inner sheath and the thinner outer sheath, the flame retardant performance of the flame retardant sheath can be improved, and meanwhile, the extrusion molding load of the inner sheath can be reduced.
The invention also provides a manufacturing method of the flame-retardant sheath structure of the radiation leaky coaxial cable, wherein the base resin used by the inner sheath and the outer sheath is the same polymer, and the base resin is one or two of LDPE, LLDPE, HDPE, PP, EVA, EEA and EBA.
Further, the inner sheath is formed by adding 50-60% of inorganic flame retardant into the base resin by mass percent, and the inorganic flame retardant is magnesium hydroxide or aluminum hydroxide. Thus, the Limiting Oxygen Index (LOI) of the inner sheath reaches 35% -45%, the vertical burning grade of the inner sheath reaches V-0, and no photo-aging agent resistant to sunlight aging is needed to be added.
Further, the outer sheath is formed by adding 20-30% of chemical expansion type flame retardant in percentage by mass into the base resin and extruding the chemical expansion type flame retardant which is phosphorus-ammonia expansion type flame retardant. Therefore, the limiting oxygen index of the outer sheath is 30-35%, the vertical burning grade of the outer sheath is not lower than V-1, the breaking elongation is not lower than 250%, and the tensile breaking strength is not lower than 17MPa.
Further, the inner sheath and the outer sheath are both extruded vertically in close series. From this, can avoid melting and hanging down to guarantee that fire-retardant sheath remains concentric with the cable core all the time, avoided appearing great clearance between fire-retardant sheath and the outer conductor.
Further, the inner sheath and the outer sheath adopt two sets of different extrusion molding dies.
Further, the inner sheath and the outer sheath share one extrusion molding machine head, and the two extrusion molding dies are respectively positioned at two sides of the extrusion molding machine head and connected with the extrusion molding machine head.
Further, the cable core after the extrusion of the inner sheath is immediately extruded through the extrusion die of the outer sheath. Therefore, under the protection of the outer sheath with good mechanical properties, the inner sheath with poor mechanical properties is not easy to break, crack and other degradation conditions under the action of external forces such as bending, stretching and the like of the leaky coaxial cable, the extrusion molding efficiency of the inner sheath and the outer sheath can be improved, the inner sheath and the outer sheath can be ensured to be bonded together, and meanwhile, the extruder and the extrusion molding die with different characteristics can be selected according to different processing requirements and processing properties of the inner sheath and the outer sheath.
Compared with the prior art, the invention has the beneficial effects that:
the invention greatly improves the shell forming property of the combustion matter of the inner sheath, and the inner sheath forms a carbon shell after combustion when the leaky coaxial cable burns, so that flame can be isolated from entering the interior of the leaky coaxial cable, the flame retardant efficiency of the outer sheath is high, and meanwhile, the invention can keep better mechanical and physical properties and can improve the flame retardant property of the flame retardant sheath.
Drawings
The invention will be further described with reference to the drawings and examples.
Fig. 1 is a schematic cross-sectional view of a flame retardant jacket structure for a leaky coaxial cable of the invention.
In the figure: 1. an inner sheath; 2. an outer sheath.
Detailed Description
The invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic representations which merely illustrate the basic structure of the invention and therefore show only the structures which are relevant to the invention.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, features defining "first", "second" may include one or more such features, either explicitly or implicitly. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
As shown in fig. 1, a radiation type leaky coaxial cable flame retardant sheath structure includes: the inner sheath 1 and the outer sheath 2 are sleeved on the inner sheath 1, and are abutted against the inner sheath 1; wherein: the inner sheath 1 is an inorganic filling type flame-retardant polyolefin sheath, and the outer sheath 2 is a chemical expansion type flame-retardant sheath. Therefore, the shell forming property of the combustion matter of the inner sheath 1 is greatly improved, the inner sheath 1 forms a carbon shell after being combusted when the leaky coaxial cable is combusted, flame can be isolated from entering the interior of the leaky coaxial cable, the flame retardant efficiency of the outer sheath 2 is high, meanwhile, the better mechanical and physical properties can be kept, and the flame retardant property of the flame retardant sheath can be improved.
In this embodiment, the radial sections of the inner sheath 1 and the outer sheath 2 are both circular, the inner diameter of the inner sheath 1 is d1, the outer diameter of the inner sheath 2 is d2, the inner diameter of the outer sheath 2 is d2, the outer diameter of the outer sheath is d3, the thickness of the inner sheath 1 is H1, the radial sectional area is S1, the thickness of the outer sheath 2 is H2, the radial sectional area is S2,1.5 < H1/H2 < 2.5, and S1/S2 < H1/H2, wherein: h1 =d2-d 1, h2=d3-d 2, s1=pi ((d 2) 2 －(d1) 2 )，S2＝π((d3) 2 －(d2) 2 ). Therefore, the cost of the flame retardant of the outer sheath 2 is higher than that of the flame retardant of the inner sheath 1, the inner sheath 1 is thicker, and the outer sheath 2 is thinner, so that the material cost of the flame retardant sheath can be reduced, the flame retardant performance of the flame retardant sheath can be improved, and meanwhile, the extrusion molding load of the inner sheath 1 can be reduced.
The invention also provides a manufacturing method of the radiation type leaky coaxial cable flame retardant sheath structure, wherein the base resin used by the inner sheath 1 and the outer sheath 2 is one or two of LDPE (low density polyethylene), LLDPE (linear low density polyethylene), HDPE (high density polyethylene), PP (polypropylene), EVA (ethylene-vinyl acetate copolymer), EEA (ethylene-ethyl acrylate) or EBA (ethylene-butyl acrylate). For example, the base resins of the inner sheath 1 and the outer sheath 2 are all LDPE, or the material base resin of the inner sheath 1 is EVA, the material base resin of the outer sheath 2 is LDPE, or the material base resins of the inner sheath 1 and the outer sheath 2 are all blends of EVA and LLDPE.
In this embodiment, the inner sheath 1 is extruded with 50% -60% by mass of inorganic flame retardant, the inorganic flame retardant is magnesium hydroxide or aluminum hydroxide, and the outer sheath 2 is extruded with 20% -30% by mass of chemical intumescent flame retardant, the chemical intumescent flame retardant is phosphorus-ammonia intumescent flame retardant. Therefore, the Limiting Oxygen Index (LOI) of the inner sheath 11 reaches 35-45%, the vertical burning grade of the inner sheath 11 reaches V-0, no photo-aging agent resistant to sunlight aging is needed to be added, the limiting oxygen index of the outer sheath 2 is 30-35%, the vertical burning grade of the outer sheath 2 is not lower than V-1, the breaking elongation is not lower than 250%, and the tensile breaking strength is not lower than 17MPa.
Specifically, the phosphorus-ammonia intumescent flame retardant comprises APP (ammonium polyphosphate), PER (pentaerythritol) and MEL (melamine).
Specifically, the inner sheath 1 is prepared into particles after mixing the base resin and the inorganic flame retardant, and then extruded, and the outer sheath 2 is prepared into particles after mixing the base resin and the chemical intumescent flame retardant, and then extruded.
In this embodiment, the inner sheath 1 and the outer sheath 2 are all extruded vertically in tight series, the inner sheath 1 and the outer sheath 2 are two sets of different extrusion molding dies, the inner sheath 1 and the outer sheath 2 share one extrusion molding machine head, the two sets of extrusion molding dies are respectively located at two sides of the extrusion molding machine head and connected with the extrusion molding machine head, and the cable core after the extrusion molding of the inner sheath 1 is immediately extruded through the extrusion molding dies of the outer sheath 2. Therefore, sagging can be avoided, so that the flame-retardant sheath is ensured to be concentric with the cable core all the time, and a larger gap between the flame-retardant sheath and the outer conductor is avoided; because the base resins used by the sheath materials of the inner sheath 1 and the outer sheath 2 are the same or similar, and the inner sheath 1 and the outer sheath 2 are bonded together under the condition of not being cooled, the two can keep bonding to form a whole, so that under the protection of the outer sheath 2 with good mechanical properties, the inner sheath 1 with poor mechanical properties is not easy to break and crack under the action of external forces such as bending and stretching of a leaky coaxial cable, the extrusion molding efficiency of the inner sheath 1 and the outer sheath 2 can be improved, the inner sheath 1 and the outer sheath 2 can be ensured to be bonded together, and meanwhile, an extruder and an extrusion molding die with different characteristics can be selected according to different processing requirements and processing performances of the inner sheath 1 and the outer sheath 2.
Specifically, two extrusion molding machines used for the inner sheath 1 and the outer sheath 2 are arranged on a platform 5-10 m away from the ground, the central axis of a cable core passing through the central line of the extrusion molding machine head is vertical to the ground before and after entering and exiting the extrusion molding machine head, the cable core is wrapped, and the melted sheath material is vertical to the ground after exiting the extrusion molding machine head and is consistent with the gravity action direction of the sheath material; the melted sheath materials of the inner sheath 1 and the outer sheath 2 respectively enter different extrusion molding dies after coming out of the machine chamber.
For example, the inner sheath 1 is extruded so that the inner sheath 1 is tightly attached to the outer conductor and fills the slotted hole of the outer conductor, the flame retardant performance of the leaky coaxial cable is improved, the outer sheath 2 is extruded in a tube extrusion mode, extrusion eccentricity is greatly reduced, partial stripping of the outer sheath 2 can be avoided, the outer sheath 2 is ensured to keep complete and minimum point thickness under the condition of reduced average thickness, the surface of the outer sheath 2 obtained by tube extrusion is smoother, if the co-extrusion technology is adopted, namely, the extrusion of the inner sheath 1 and the outer sheath 2 is completed by one extrusion die, the advantages of extrusion and tube extrusion are not considered, namely, the extrusion mode can enable the inner sheath 1 and the outer conductor to be more compact, the leaky coaxial cable structure is more compact, the flame retardant performance of the leaky coaxial cable is improved, and the eccentricity of the sheath is easier to be reduced by tube extrusion; during processing, the melt viscosity of the outer sheath 2 is lower than that of the inner sheath 1 material containing a large amount of inorganic filler, so that the characteristics of the extruder adopted by the outer sheath 2 and the inner sheath 1 are different, the compression ratio of an extrusion screw of the inner sheath 1 is lower than that of the extruder and is 1-1.2, the surface of a machine chamber is provided with shallow thread grooves, the extrusion corresponds to the extrusion of the sheath material from the machine chamber, and the outer sheath 2 can adopt an extruder for extruding common polyvinyl chloride or polyethylene, and the screw compression ratio of the extruder is 2.5-3.
For example, the extrusion die of the inner sheath 1 covers the die orifice from 2cm to 10cm from the die core back seat of the extrusion die of the outer sheath 2.
Example 1:
adding 50% of inorganic flame retardant into the base resin, and preparing an inner sheath 1 by adopting a tight series vertical extrusion molding method from the 50% of inorganic flame retardant and the base resin;
the intumescent flame retardant with the mass fraction of 20% is added into the base resin, and the chemical intumescent flame retardant with the mass fraction of 20% and the base resin are manufactured into the outer sheath 2 by adopting a tight series vertical extrusion molding method.
Example 2:
the difference from example 1 is that the mass fraction of the inorganic flame retardant is 55% and the mass fraction of the chemical intumescent flame retardant is 25%.
Example 3:
the difference from example 1 is that the mass fraction of the inorganic flame retardant is 60% and the mass fraction of the chemical intumescent flame retardant is 30%.
Comparative example 1:
the difference from example 1 is that the mass fraction of the inorganic flame retardant is 40% and the mass fraction of the chemical intumescent flame retardant is 10%.
Limiting Oxygen Index (LOI) test method: determination of the second part of the combustion behaviour according to GB/T2406-2009 oxygen index method for plastics: the room temperature test was carried out as specified in the following test, method for measuring vertical burning grade: according to GB/T18380.12-2022 section twelfth section of flame test of electric and optical cables: the single insulated wire and cable flame vertical propagation test 1KW premixed flame test method is specified to test, and the test method comprises the following steps of: according to the third part of the test method of the indoor communication cable with the copper core polyolefin insulation aluminum plastic comprehensive sheath of YD/T837.3-1996: the test was carried out as specified in the test methods for mechanical physical properties.
Examples 1-3 and comparative example 1 the data tested using the test methods described above are shown in Table I.
List one
According to table one, it is possible to:
the LOIs of the inner sheath 1 and the LOIs of the outer sheath 2 are higher in examples 1-3, and the breaking elongation of the outer sheath 2 and the tensile breaking strength of the outer sheath 2 are reduced compared with comparative example 1; compared with comparative example 1, example 1 prepared inner sheath 1 with 50% by mass of inorganic flame retardant and outer sheath 2 with 20% by mass of chemical intumescent flame retardant, the LOI of inner sheath 1 can be increased by 10%, the LOI of outer sheath 2 can be increased by 10%, the elongation at break of outer sheath 2 can still be kept at 129%, and the tensile breaking strength of outer sheath 2 can still be kept at 20MPa; compared with the embodiment 1, the amounts of the inorganic flame retardant and the intumescent flame retardant in the embodiments 2 and 3 are improved, the LOI of the inner sheath 1 can be improved by 5-10%, the LOI of the outer sheath 2 can be improved by 2.5-5%, the breaking elongation of the outer sheath 2 can still be kept between 117 and 129%, and the tensile breaking strength of the outer sheath 2 can still be kept between 14MPa and 20MPa.
The supplementary ones are: 1. the addition of the inorganic flame retardant to the jacket material requires a very large proportion of the inorganic flame retardant to be added, and in some special cases, even exceeds the amount of the polymer itself, and therefore, the physical and mechanical properties of the polymer are extremely affected, which requires the treatment of the inorganic flame retardant, for example: micronizing and surface activating.
2. The expansion type flame retardant has poor compatibility with the high polymer, so that the physical and mechanical properties, the electrical properties and the insulation properties of the high polymer are reduced, especially the tensile strength and the impact strength are greatly reduced, and the engineering application difficulty is increased after the expansion type flame retardant is excessive, so that the modification treatment is needed.
3. The magnesium hydroxide or the aluminum hydroxide is adopted as the inorganic flame retardant, the flame retardant mechanism is that magnesium hydroxide or aluminum hydroxide is used for explaining the water vapor when heated to reduce the surface temperature of the cable, meanwhile, the water vapor can dilute the oxygen on the surface of the sheath, and the decomposed oxide adheres to the surface of the sheath to play a role of blocking, so that the flame retardant performance is realized, the flame retardant effect is highly related to the proportion of the inorganic flame retardant, the V-0 grade of high flame retardance is realized, the adding proportion of the inorganic flame retardant is required to be more than 50%, but the inorganic flame retardant is excessively added, and the mechanical and physical properties of the sheath, such as the breaking elongation and the tensile breaking strength index of the sheath, are seriously deteriorated.
4. The chemical expansion type flame retardant adopts phosphorus-nitrogen, and comprises main components of APP (ammonium polyphosphate), PER (pentaerythritol) and MEL (melamine), wherein APP can be used as an acid source and an air source, PER is used as a carbon source, MEL is used as an air source, but when the sheath burns at a lower temperature, an acidic substance is released by APP, then the APP and PER are subjected to esterification reaction at a temperature slightly higher than the temperature at which the acid is released, and in the esterification process, an esterification product is dehydrated to form carbon to form a carbon layer, and the sheath layer begins to melt; meanwhile, gases such as water vapor, ammonia gas and the like generated by the esterification reaction and nonflammable gases generated by APP and MEL gas sources are filled into the carbon layer, so that the jacket layer is expanded and foamed, and when the reaction is nearly completed, the generated carbon layer is solidified, and finally, the porous foam carbon layer is formed, thereby achieving the purpose of flame retardance. As the chemical expansion type flame retardant of phosphorus-nitrogen has high flame retardant efficiency, the flame retardant V-1 grade can be realized as long as the adding proportion reaches 20% -30%, and the flame retardant has higher price, thus the overall production cost can be increased, and the consumption of the flame retardant needs to be comprehensively considered in combination with the actual demand.
In summary, the shell forming property of the combustion matter of the inner sheath 1 is greatly improved, the inner sheath 1 forms a carbon shell after being combusted when the leaky coaxial cable is combusted, flame can be isolated from entering the interior of the leaky coaxial cable, the flame retardant efficiency of the outer sheath 2 is high, meanwhile, the better mechanical and physical properties can be kept, and the flame retardant performance of the flame retardant sheath can be improved.
The above-described preferred embodiments according to the present invention are intended to suggest that, from the above description, various changes and modifications can be made by the worker in question without departing from the technical spirit of the present invention. The technical scope of the present invention is not limited to the description, but must be determined as the scope of the claims.
Claims (10)
1. A radiation type leaky coaxial cable flame retardant sheath structure, comprising:
an inner sheath (1), and
the outer sheath (2) is sleeved on the inner sheath (1) and is abutted against the inner sheath (1);
wherein: the inner sheath (1) is an inorganic filling type flame-retardant polyolefin sheath, and the outer sheath (2) is a chemical expansion type flame-retardant sheath.
2. The flame-retardant sheath structure of the radiation type leaky coaxial cable according to claim 1, wherein the radial sections of the inner sheath (1) and the outer sheath (2) are circular, the inner diameter of the inner sheath (1) is d1, the outer diameter of the inner sheath is d2, and the inner diameter of the outer sheath (2) is d2 and the outer diameter of the outer sheath is d3.
3. The flame retardant jacket structure of a leaky coaxial cable according to claim 2, wherein the inner jacket (1) has a thickness H1 and a radial cross-sectional area S1, the outer jacket (2) has a thickness H2 and a radial cross-sectional area S2,1.5 < H1/H2 < 2.5, S1/S2 < H1/H2, wherein: h1 =d2-d 1, h2=d3-d 2, s1=pi ((d 2) 2 －(d1) 2 )，S2＝π((d3) 2 －(d2) 2 )。
4. A method for manufacturing a flame retardant jacket structure for a leaky coaxial cable as claimed in any of claims 1-3, wherein the base resin used for the inner jacket (1) and the outer jacket (2) is the same polymer, and the base resin is one or two of LEPE, LLDPE, HDPE, PP, EVA, EEA, EBA.
5. The method for manufacturing the flame-retardant sheath structure of the leaky coaxial cable according to claim 4, wherein the inner sheath (1) is formed by adding 50% -60% of inorganic flame retardant in mass percent into base resin for extrusion molding, and the inorganic flame retardant is magnesium hydroxide or aluminum hydroxide.
6. The method for manufacturing a flame-retardant sheath structure of a leaky coaxial cable according to claim 4, wherein the outer sheath (2) is formed by adding 20% -30% of chemical expansion type flame retardant in mass percentage into base resin, and the chemical expansion type flame retardant is phosphorus-ammonia expansion type flame retardant.
7. The method for manufacturing a flame retardant jacket structure for leaky coaxial cable according to claim 4, wherein said inner jacket (1) and said outer jacket (2) are extruded vertically in close series.
8. The method for manufacturing the flame-retardant sheath structure of the leaky coaxial cable according to claim 4, wherein the inner sheath (1) and the outer sheath (2) adopt two different extrusion molding dies.
9. The method for manufacturing the flame-retardant sheath structure of the leaky coaxial cable according to claim 8, wherein the inner sheath (1) and the outer sheath (2) share one extrusion molding machine head, and two sets of extrusion molding dies are respectively positioned at two sides of the extrusion molding machine head and connected with the extrusion molding machine head.
10. The method of manufacturing a flame retardant jacket structure for leaky coaxial cable according to claim 9, wherein the cable core after the extrusion of the inner jacket (1) is immediately extruded through the extrusion die of the outer jacket (2).
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