Fire-resistant pipe protected by YSZ ceramic substrate

Abstract

A pipe capable of meeting the fire resistance requirements of AS1055 under zero flow conditions is disclosed. The pipe has multiple layers including a flexible ceramic substrate layer of yttria-stabilized zirconia (YSZ) disposed between first and second layers of silicone rubber. Figure for abstract: Fig. 1

Description

Title of the invention: Fire-resistant pipe protected by a ceramic substrate YSZ [0001 ] CROSS REFERENCE TO ASSOCIATED APPLICATIONS

[0002] The present application claims the benefit of priority to the provisional application for serial number IN 202111031822, filed on July 15, 2021, and to the provisional application for serial number IN 202111032960, filed on July 22, 2021.

[0003] BACKGROUND OF THE INVENTION

[0004] Aerospace transportation products (hoses, tubes, etc.) may be used to transport fuel, oil, or hydraulic fluid under pressure in locations that may be exposed to fire. In such applications, a fire protection mechanism may be used to ensure that the product does not experience failure (e.g., leakage) for a specified time (e.g., 5 to 15 minutes) under specified conditions, including specified flow conditions.

[0005] Some aircraft hoses may be certified for use in fire hazard areas as defined by the FAA (Federal Aviation Administration) or applicable certification authorities. For example, aircraft hoses may be configured to withstand direct flame for a certain time, such as five minutes or fifteen minutes, to be certified as fire resistant or flame retardant, respectively. Existing aircraft hoses suitable for use in fire hazard areas may be subject to degradation upon exposure to fire, which may affect the product's ability to meet firefighting needs.

[0006] In aerospace applications, as aircraft systems have evolved, fire resistance testing requirements have become more stringent, posing challenges in demonstrating compliance with existing fireproofing technologies. For example, some current fire-resistant blankets may not consistently meet the AS 1055 and TSO fire performance requirements that allow for slight or no fluid flow through the fluid carrying product during testing, let alone the AS 1055 zero flow requirements of next-generation fluid carrying products.

[0007] US Patent No. 8,409,682 discloses a heat-resistant air hose for diesel engines having an outer layer containing a peroxide-free crosslinkable ethylene acrylic rubber such as an ethylene-methacrylate copolymer and a halogen-free flame retardant such as aluminum hydroxide.

[0008] US Patent No. 10,190,706 discloses a fire resistant pipe assembly having an outer fire resistant layer comprising a polymeric material and expandable graphite.

[0009] Published application US 2019 / 0154174 describes a fire hazard zone hose comprising a thermal protection sleeve and a stainless steel braided outer reinforcement.

[0010] Published application US 2019 / 0247685 describes a fire-resistant blanket for fluid transport products comprising alternating intermediate layers of basalt tape and fiberglass.

[0011] To meet the zero flow requirements of AS 1055 and TSO, many existing pipes must be covered with a fire sleeve designed to AS 1072. Fire sleeves increase the outside diameter (OD) of the pipe, add weight, and may have wrinkled surfaces, which causes difficulty when securing these pipes in aircraft.

[0012] Some existing fire protection technologies include all-silicone blankets or silicone-coated fiberglass sleeves. When silicone is exposed to fire, it can form a non-uniform charred residue, and may tend to fall off the surface. This can expose an inner layer of PTFE to the fire, which can lead to a leak in the hose due to melting of the PTFE layer.

[0013] There is a need for solutions / options that minimize or eliminate one or more challenges or weaknesses in fluid conveyance products, so as to meet more stringent zero flow performance requirements in accordance with AS 1055 and TSO. Summary of the invention

[0014] The invention relates to a fire resistant hose suitable for use in aircraft to meet AS1055 and TSO requirements for 15 minutes under zero flow conditions.

[0015] A fire-resistant hose having a flexible ceramic substrate layer as a fire impact resistant layer is provided. For example, the fire-resistant hose may include one or more, or two or more, yttria-stabilized zirconia (YSZ) ceramic substrate layers. The one or more YSZ ceramic substrate layers may be intermediate layers. For example, a YSZ ceramic substrate layer may be sandwiched between two silicone layers. The fire-resistant hose may further comprise a metal reinforcing layer. The fire-resistant hose may comprise an innermost tube layer comprising a PTFE. The fire-resistant hose may comprise a layer of metal reinforcement on an innermost tube layer comprising a PTFE. In embodiments, the fire-resistant hose may include from outside to inside: an outer silicone rubber layer; a YSZ ceramic substrate layer; an inner silicone rubber layer; a metal reinforcement layer; and an innermost PTFE tube layer.

[0016] The fire-resistant pipe may include from the inside to the outside an inner tube prepared from a composition comprising PTFE, a metal reinforcing layer and an outer thermal insulation layer. The thermal insulation layer may comprise a first inner silicone rubber layer, an intermediate YSZ ceramic substrate layer and a second outer silicone rubber layer.

[0017] The first and second silicone layers may be prepared from a composition comprising a silicone-based rubber.

[0018] A thermal insulation layer silicone rubber composition is provided which, when cured, passes the flame resistance test according to MSHA ASTP5007. The thermal insulation layer comprising a YSZ ceramic substrate layer between two layers of silicone rubber composition, when cured, can pass a flame resistance test according to MSHA ASTP5007 after 5 minutes and / or after 15 minutes.

[0019] A fire-resistant hose is provided, comprising a thermal insulation layer comprising a yttria-stabilized zirconia (YSZ) flexible ceramic substrate layer disposed between a first silicone rubber layer and a second silicone rubber layer. The fire-resistant hose may further comprise an inner tube layer prepared from a composition comprising a polytetrafluoroethylene (PTFE). The fire-resistant hose may further comprise one or more reinforcing layers. The reinforcing layer may be disposed between the inner tube layer and the thermal insulation layer.

[0020] In some embodiments, the YSZ ceramic substrate layer comprises zirconia (ZrO2) and from about 3 mol% to about 8 mol% yttria (Y2O3). The YSZ ceramic substrate layer may have a thickness in a range of from about 20 micrometers to about 100 micrometers; from about 20 micrometers to about 50 micrometers; or about 40 micrometers.

[0021] The fire resistant hose may include a first silicone rubber layer and a second silicone rubber layer prepared from a silicone rubber composition comprising from about 40 to 80% by weight, or from about 50 to 70% by weight of a silicone-based rubber. The silicone rubber composition may comprise one or more, two or more, or three or more additives selected from the group consisting of curing agents, process aids, flame retardants, adhesion promoters, antioxidants, ultraviolet light stabilizers, fillers, thixotropic agents, additional silicones, dyes and colorants.

[0022] The silicone rubber composition may comprise a ground silica filler in an amount of between about 0 and 30% by weight, 1 and 20% by weight, 5 and 15% by weight, or about 10 and 12% by weight. The silicone rubber composition may comprise a zinc borate flame retardant. The reinforcing layer may comprise a metal braid. The reinforcing layer may comprise a stainless steel metal braid.

[0023] A fire resistant hose is provided comprising a multiplicity of layers, including from an inner direction to an outer radial direction comprising: i) an inner tube layer prepared from a composition comprising a PTFE; ii) a first reinforcing layer comprising a metal braid; iii) a first layer of silicone rubber; iv) a YSZ ceramic substrate layer; and v) a second layer of silicone rubber. The first and second layers of silicone rubber may have: i) a hardness of 65 to 75 Shore A according to ASTM 2240; ii) a tensile strength of at least 750 psi according to ASTM D412; iii) a percentage elongation of at least 150% according to ASTM D412; iv) a tear strength of at least 50 Die C according to ASTM D624; (v) a 50% modulus of 250 to 350 psi according to ASTM D412; and (vi) a 100% modulus of 300 to 450 psi according to ASTM D412.

[0024] The fire-resistant hose may include a thermal insulation layer comprising a cured silicone rubber composition layer and a YSZ ceramic substrate layer that passes a flame resistance test according to MSHA ASTP5007; and exhibits significant external visible char formation when tested according to MSHA ASTP5007. The fire-resistant hose preferably meets or exceeds AS1055 and TSO performance requirements at 15 minutes under zero flow conditions.

[0025] A fire resistant hose is provided, wherein the hose meets or exceeds the performance requirements of AS 1055 and TSO at 5 minutes and / or 15 minutes under zero flow conditions.

[0026] A fire resistant hose is provided, wherein the hose is rated for a continuous operating temperature range of -65°F to 450°F (-54°C to 232°C).

[0027] A fire resistant hose is provided, wherein the hose is rated for an operating pressure of between about 1,000 and about 1,500 psig.

[0028] A method of manufacturing a fire-resistant pipe is provided, comprising forming an inner tube layer prepared from a composition comprising a PTFE; braiding a first reinforcing layer comprising a metal braid over the inner tube layer; extruding a first silicone rubber composition over the reinforcing layer to form a first silicone layer, wrapping or laminating a YSZ ceramic substrate material over the first silicone layer to form a YSZ ceramic substrate layer; extruding or injection molding a second silicone layer over the YSZ ceramic substrate layer to form a second silicone layer and form a green pipe; and curing the green pipe to form the fire-resistant pipe. Optionally, any suitable adhesive may be employed, for example, between a silicone rubber layer and a YSZ ceramic substrate layer. Brief description of the drawings

[0029] [Fig. 1] shows an example of a fire-resistant pipe construction comprising 5 layers.

[0030] [Fig.2] shows an example of fire-resistant pipe construction comprising 3 layers

[0031] [Fig.3] shows an example of fire-resistant pipe construction comprising 7 layers.

[0032] [Fig.4] shows an example of a method for a pipe construction comprising 5 layers.

[0033] [Fig.5] shows an illustration of the minimum bending radius test. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention relates to a fire-resistant pipe comprising multiple layers of thermal insulation coating over a standard metal pipe. These insulation layers include a YSZ ceramic substrate layer which has a significant improvement in fire protection properties over existing technologies. The pipe is designed for use in aircraft or aerospace vehicle fluid systems. For example, the fire-resistant pipe can be used for fuel, oil and hydraulic lines.

[0035] A "fire-resistant" hose line as defined by the FAA must withstand a direct flame for 15 minutes under specified flow conditions without failure. Fire-resistant lines must withstand a 5-minute exposure under these conditions.

[0036] A zero-flow fire-resistant pipe is provided, comprising a fire-resistant thermal insulation layer comprising a YSZ ceramic substrate layer. The YSZ ceramic substrate has been found to be an excellent thermal shock resistance material. The YSZ ceramic substrate exhibits no loss of integrity. structural and thermal at temperatures of 2,200 °F (1,204 °C), which is higher than the AS 1055 requirement (2,000 °F; 1,093 °C). The high temperature stability makes the YSZ ceramic substrate the best-in-class material for use in these applications.

[0037] Yttria-stabilized zirconia (YSZ) is a ceramic in which the cubic crystal structure of zirconium dioxide is made more stable at room temperature by the addition of yttrium oxide. Zirconium dioxide is commonly referred to as "zirconia" (ZrO2). Yttrium oxide is commonly referred to as "yttria" (Y2O3). YSZ may include a molecular formula ZrO2 + Y2O3.

[0038] Stabilization of the cubic zirconia polymorph over a wide temperature range can be achieved by substituting a portion of the Zr4+ ions (ionic radius of 0.82 angstrom, Â) in the crystal lattice with slightly larger ions, for example those of Y (ionic radius of yttria 0.96 angstrom, Å). The doped zirconia materials thus obtained are called stabilized zirconias. The YSZ ceramic substrate can be partially stabilized or fully stabilized. Abbreviations and acronyms commonly used in conjunction with partially stabilized YSZ may include “PSZ” partially stabilized zirconia, “YSZ3” 3 mol% yttria stabilized zirconia, “YSZ4” 4 mol% yttria stabilized zirconia, and “TZP” polycrystal tetragonal zirconia.Commonly used abbreviations and acronyms used in conjunction with fully stabilized YSZ may include “FSZ” fully stabilized zirconia, “CSZ” cubic stabilized zirconia, and “YSZ8” 8 mol% Y2O3, fully stabilized zirconia ZrO2. Partially stabilized YSZ may be YSZ3. Yttria stabilized zirconia (3 mol%), YSZ3, may comprise about 94.5 wt% ZrO2, and 5.2+ / -0.2 wt% Y2O3. The specific gravity of YSZ3 may be >5.95 g / cm3; the hardness (HV) may be >12 GPa; the elastic modulus about 205 GPa. The YSZ ceramic substrate may be any suitable commercially available YSZ ceramic substrate such as ENrG™ Inc. Thin E-Strate® ultrathin ceramic membranes.

[0039] The flexible ceramic substrates may include YSZ. The YSZ flexible ceramic substrate layer may have a thickness in a range of about 20 micrometers to about 100 micrometers; about 20 micrometers to about 50 micrometers; or about 40 micrometers, or any thickness in between. In embodiments, the YSZ ceramic substrate layer is about 20 micrometers; about 40 micrometers; about 50 micrometers; or about 100 micrometers thick. The YSZ ceramic layer may be sandwiched between 2 layers of silicone rubber. This arrangement has been found to prevent the first silicone layer from falling off during AS 1055 fire resistance tests. The presence of the flexible ceramic layer between the silicone layers led to enhanced and localized carbon residue formation.

[0040] The YSZ ceramic substrate layer can be sandwiched between two silicone layers. Due to its extremely high thermal shock resistance over a prolonged period of time, the YSZ ceramic substrate prevents the inner silicone layer from producing a non-uniform carbon residue, and thus from falling off.

[0041] The terminology used herein is only to describe particular embodiments and is not intended to limit the disclosure.

[0042] The singular forms “un / une” and “le / la” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0043] The term "and / or" designates and encompasses any possible combination of one or more of the listed elements associated.

[0044] As used herein, the term "about" means ten percent (10%) of the given value, either ten percent more than the given amount, ten percent less than the given value, or both.

[0045] As used herein, the term "composition" means one or more of a compound, a mixture, an alloy, a polymer and / or a copolymer.

[0046] As provided herein, the ranges are intended to include at least the numbers defining the boundaries of the range.

[0047] Unless otherwise indicated, values ​​in % denote % by weight.

[0048] The terms "includes" and / or "comprising", when used in this specification, specify the presence of the features, integers, steps, operations, elements, and / or components mentioned, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0049] Unless otherwise indicated, all terms, including technical and scientific terms used in the specification, have the same meaning as commonly understood by those skilled in the art to which this disclosure pertains. In the event of conflicting terminology, this specification shall take precedence.

[0050] Thermal conductivity W / m*K measures the diffusion of heat through a material itself. Where W is the thermal energy, K is the temperature difference AT = Ti - T2 (K) between each side of the material, m is the material thickness. In other words, thermal conductivity is the rate at which heat penetrates through a given material. The thermal conductivity (at 25 °C) for the YSZ ceramic substrate can be about 6.7 x 103 cal / cms °C.

[0051] The coefficient of thermal expansion (1 x 106 °C) defines how a material expands or contracts depending on external temperatures. Ceramics can have a low coefficient due to their strong interatomic bonds, making them more stable over wide temperature ranges. The coefficient of thermal expansion (25 to 800 °C) for YSZ ceramic substrate material can be about 9.5 x 10 6 / °C.

[0052] Specific heat (J / kg*K) measures how easy or difficult it is to increase the temperature of a material. In high-temperature applications, where temperature control is critical, this measurement can help determine which materials will perform best.

[0053] Thermal shock resistance (°C) measures the ability to withstand significant and sudden temperature changes. Ceramic formulations that exhibit high thermal shock resistance expand or contract very little during extreme temperature changes.

[0054] Material properties may be tested according to the following standards. Flame testing was conducted in accordance with MSHA ASTP5007 per 30 CFR §18.65; and char formation is a visible test per MSHA ASTP5007. Material properties may be tested according to ASTM D412 (tensile, elongation, modulus); ASTM D2240 (hardness). A Shore A hardness test may be conducted in accordance with ASTM D 2240-95, for example, using an Instron calibrated automatic durometer.

[0055] Radius of curvature means the radius of a bent section of pipe measured at the innermost surface of the curved portion. Minimum radius of curvature as shown in [Fig.5] means the smallest radius at which a pipe can be used. When bent at too sharp an angle, a pipe may collapse or flatten in the cross-section.

[0056] Aerospace Standard SAE 1055 D (AS) establishes uniform requirements for fire resistance testing of flexible hose assemblies for use in aircraft or aerospace fluid systems. FAA Technical Standard Orders (TSOs) are the performance qualifications for aircraft parts, materials, etc. TSO-C53a covers fuel and engine oil system assemblies. TSO-C75 covers hydraulic hose assemblies. Fire protection, fire resistance (5 minutes), or flame retardancy (15 minutes) may be designated as "Class A" or "Class B," respectively. A low specific flow rate can be achieved (e.g. fuel and lube oil can be tested at 5 x ID2 = x GPM or fluid at 1 x ID2 = x GPM) or zero flow testing can be performed for selected sets of hose types, sizes and configurations.The flow rate, duration of the fire resistance test, performance requirements can be specified. AS 1055 also defines types of pipes. by material (Type I is rubber; Type II is PTFE; Type III is rigid (metallic) tubing); by function (e.g., (a) fuel and lubricant (similar to TSO-C53a) or (b) hydraulic (similar to TSO-C75), in which fluid flow is specified; and by compatibility, where S is a synthetic fluid and P is a petroleum-based fluid).

[0057] A pipe is provided comprising multiple layers of insulation which can consistently meet an AS 1055 and TSO zero flow fire resistance condition without the addition of an external fire sleeve according to AS 1072. The pipe can meet the AS 1055 fire resistance requirements under zero flow conditions for 5 minutes and / or 15 minutes.

[0058] The fire resistant pipe of the disclosure may provide additional benefits of at least about 10% weight reduction, and / or at least about 2-5%, or up to about 15% envelope reduction compared to existing solutions for a zero flow condition. The pipe may be a kinked-free pipe including a smooth outer diameter OD for ease of attachment.

[0059] The proposed hose is suitable for transporting various fluids in aerospace conditions including fuel, oil or hydraulic fluids including synthetic fluids such as phosphate ester hydraulic fluids (e.g., SKYDROL™ aviation hydraulic fluid, Eastman Aviation).

[0060] A fire-resistant hose is provided having a multiplicity of layers. The fire-resistant hose may include an outer layer prepared from a composition that includes a silicone-based rubber.

[0061] The fire resistant pipe of [Fig.l] can be prepared in the pipe dimensions shown in Table 1.

[0062] Table 1. Fire-resistant pipe sizes, pressure specifications and minimum bend radius Pipe Size Working Pressure psig Test Pressure psig Minimum Ambient Temp Burst Pressure psig High Temp Burst Pressure min psig Radius of curvature inside the bend inches 03 1,500 3,000 12,000 7,000 2.00 04 1,500 3,000 12,000 7,000 2.00 05 1,500 3,000 10,000 6,500 2.00 06 1,500 3,000 9,000 6,500 4.00 08 1,500 3,000 8,000 6,000 4.63 10 1,500 3,000 7,000 5,500 5.50 12 1,000 2,000 5,000 3 500 6.50 16 1,250 2,500 5,000 3,500 7.38 20 1,000 2,000 4,000 3,000 11.00 24 1,000 2,000 4,000 3,000 14.00

[0063] A fire resistant pipe according to the disclosure may be prepared in any suitable pipe size, for example, the pipe sizes shown in Table 1, including -03, -04, -05, -06, -08, -10, -12, -16, -20 or -24. The fire resistant pipe of the disclosure may be qualified as a medium pressure pipe or a high pressure pipe. For example, the fire-resistant pipe of the disclosure may have an operating pressure of between 1,000 and 1,500 psig, or 1,000, 1,250, or 1,500 psig depending on the size or size and configuration of the pipe, for example, according to Table 1. The test pressure may be 2,000 to 3,000 psig, or 2,000, 2,500, or 2,000 psig depending on the size or size and configuration of the pipe.The burst pressure at room temperature may be 4,000 to 12,000 psig, or 4,000, 5,000, 7,000, 8,000, 9,000, 10,000, or 12,000 psig depending on the size or size and configuration of the pipe. The minimum burst pressure at high temperature may be 3,000 to 7,000 psig, or 3,000, 3,500, 5,500, 6,000, 6,500, or 7,000 psig depending on the size or size and configuration of the pipe. The fire-resistant pipe of the invention may have a minimum bend radius according to AS1946E specifications. The minimum bend radius inside the elbow may be 2.00, 4.00, 4.63, 5.50, 6.50, 7.38, 11.00 or 14.00 inches depending on the pipe size or size and configuration according to Table 1.

[0064] The fire resistant hose may be qualified for a continuous operating temperature range of -65°F to 450°F (-54°C to 232°C).

[0065] The fire-resistant hose may include a multiplicity of layers. The fire-resistant hose may include an inner tube prepared from a composition that includes a PTFE; an intermediate metal reinforcing layer; an intermediate layer prepared from a composition comprising a silicone-based rubber; a YSZ ceramic substrate layer; and an outer layer prepared from a composition that includes a silicone-based rubber.

[0066] The fire-resistant hose may include an inner tube prepared from a composition that includes a PTFE; a second layer that is a metal reinforcing layer; a third layer prepared from a composition that includes a silicone-based rubber; a fourth layer comprising a YSZ ceramic substrate; and a fifth layer prepared from a composition that includes a silicone-based rubber. The fifth layer may be the outer layer. The metal reinforcing layers may comprise a metal braid, for example, a stainless steel braid.

[0067] [Fig.l] shows an exemplary construction of a fire-resistant hose 100 comprising 5 layers. The hose 100 may include an inner tube 110, a first reinforcing layer 120, a first silicone rubber layer 130, a flexible ceramic substrate layer 140, and an outer silicone rubber layer 150. The inner tube 110 may comprise a PTFE. The reinforcing layer 120 may comprise a metal braid. The silicone rubber layers 150 and 130 may be prepared from a composition that includes a silicone-based rubber. The flexible ceramic substrate layer 140 may comprise a YSZ ceramic substrate.

[0068] [Fig. 2] shows an exemplary fire-resistant pipe construction 200 comprising 3 layers. The pipe 200 may include an inner tube 210, a first reinforcing layer 220, and an outer thermal insulation layer 230. The inner tube layer 210 may comprise PTFE. The reinforcing layer may comprise a metal braid, for example, corrosion-resistant stainless steel. The outer thermal insulation layer 230 may comprise a first inner silicone rubber layer, an intermediate YSZ ceramic substrate layer, and a second outer silicone rubber layer. The YSZ ceramic substrate layer may be a partially stabilized YSZ ceramic substrate.

[0069] [Fig. 3] shows an example of a fire-resistant pipe construction 300 comprising 7 layers. The pipe 300 may include an inner tube 310, a first reinforcing layer 320, a first silicone rubber layer 330, a first YSZ ceramic substrate layer 340, a second silicone rubber layer 350, a second YSZ ceramic substrate 360, and a third outer silicone rubber layer 370. The inner tube 310 may comprise a PTFE. The reinforcement layer 320 may comprise a stainless steel braid. The first silicone rubber layer 330, the second silicone rubber layer 350, and the outer silicone layer 370 may be prepared from a composition that includes a silicone-based rubber. The first and second YSZ ceramic substrate layers may comprise a partially stabilized ceramic substrate material. An optional fire sleeve layer may be employed. For example, a silicone-coated fiberglass sleeve such as an AE102 fire sleeve may optionally be included.

[0070] The fire-resistant hose of the disclosure includes an inner tube layer that forms a flow path for conveying the fluid. For example, the fire-resistant hose of [Fig. 1] includes an inner tube layer 110 that may be prepared from any suitable material to substantially contain the fluid throughout a range of aircraft operating temperatures. For example, an aircraft operating temperature range may be from about -65° Fahrenheit (°F) (about -54° Celsius (°C) to about +450°F (about +232°C). The fire-resistant hose may include an inner tube layer prepared from a composition comprising polytetrafluoroethylene (PTFE). Among fluoropolymers, PTFE has one of the highest operating temperatures, the lowest coefficient of friction, and good abrasion and chemical resistance.ASTM D4895 refers to a PTFE resin prepared from a dispersion. PTFE resins are tetrafluoroethylene homopolymers or modified homopolymers, for example, containing not more than 1% by weight of other fluoromonomers. The PTFE may be, for example, Chemours PTFE 62X or T62X. The PTFE may have a melting point above 600°F per DTA E-168, a maximum continuous use temperature of at least about 500°F (260°C) per DI894, and / or a maximum intermittent use temperature of at least about 550°F. The PTFE may be any suitable PTFE, for example, Type 1 Class B Grade 4 per ASTM D4895.

[0071] The inner tube composition may further include a treatment and / or lubricant that aid in processing, preforming, and extruding. The processing aid may be a liquid processing aid hydrocarbon, such as naphtha or other petroleum distillates. The lubricant may be, for example, a synthetic isoparaffinic fluid, for example, an Isopar™ fluid, for example, Isopar™ R, Brenntag UK Ltd. The PTFE inner tube may be formed by a process including batch sintering of a tube PTFE is 740°F and time varies due to reduction ratio and line speed.

[0072] The fire-resistant hose may include one or more reinforcing layers. The reinforcing layer(s) may strengthen the inner tube, e.g., improve kink resistance, increase the amount of pressure that can be applied to the inner tube, and / or improve the robustness of the fire-resistant zone hose during exposure to a fire. The reinforcing layer(s) may, for example, include a metal braid. The metal braid may be, for example, a stainless steel wire braid (e.g., a corrosion-resistant stainless steel, such as a 300 series stainless steel).

[0073] The fire-resistant hose may include an outer silicone rubber layer. The fire-resistant hose may include one or more layers of silicone rubber. In some configurations, the fire-resistant hose may include an outer silicone rubber layer 150 and an intermediate silicone rubber layer 130. The fire-resistant hose may include a thermal insulation layer. The thermal insulation layer may include one or more layers of silicone rubber and one or more layers of flexible ceramic substrate. The thermal insulation layer may include a layer of flexible ceramic substrate disposed between two layers of silicone rubber.

[0074] The silicone rubber layers may be prepared from a silicone rubber composition. The silicone rubber composition may include a silicone-based rubber. The silicone rubber composition may be prepared from a silicone-based rubber and optionally one or more additives. Additives may include curing agents, processing aids, ultraviolet light stabilizers, fillers, thixotropic agents, additional silicones, dyes, and colorants. The first and / or second silicone rubber layers may be prepared from a composition comprising a silicone rubber base and a fire-resistant additive. The silicone rubber may be a solid or liquid silicone rubber. The silicone rubber may be a solid silicone rubber.Uncured silicone rubber contains polymers of varying chain lengths including a silicon-oxygen main chain (the siloxane backbone) and an organic moiety bonded to the silicon. A silicon atom has four valence electrons, which is why silicone rubber can be abbreviated as Q for "quaternary." Silicone rubbers, or polysiloxanes, are the only type of rubbers that have an inorganic main chain, e.g., (-O-SiR2-O-SiR2-O-SiR2-O-), with organic R side chains attached to the Si atoms. For example, silicone rubber can . have a general main chain chemical formula -[R2SiO]n-, where R = alkyl groups (methyl -CH3, ethyl -CH2CH3), vinyl (-CH=CH2), or phenyl (-C6H5). The organic groups on the polysiloxane backbone may be methyl, vinyl, and / or phenyl groups. Thus, the silicone rubber may include polydiorganosiloxanes. Other rubbers may have an organic carbon-hydrogen backbone, e.g., (-CH2-CH2-CH2-CH2-CH2-), for example, optionally further comprising an organic side group. The silicone rubber may include MQ, VMQ, FVMQ, and / or PVMQ silicone rubber. MQ silicone rubbers include polydimethylsiloxanes (R = methyl). VMQ silicone rubbers are similar to polydimethylsiloxanes (MQ), but some of the methyl groups have been replaced with vinyl groups (R = methyl, vinyl). The double bond of the vinyl group is a reactive group that can be used for crosslinking. PVMQ silicone rubbers have a small portion of the methyl groups of a VMQ replaced by phenyl groups (R = methyl, vinyl, phenyl).FVMQ is a VMQ in which a small number of methyl groups have been replaced by trifluoropropyl substituents. Silicone rubbers may have predominantly methyl side groups (-CH3), or optionally some vinyl side groups to aid crosslinking, (e.g., -CH=CH2). Many commercial grades are of the VMQ type. Phenyl groups (e.g., C6H5) may be added to improve low-temperature properties. These are called PVMQ types. The optional addition of fluorinated groups may improve oil and fuel resistance. These are called FVMQ types. The outer thermal insulation layer may be prepared from a composition comprising a silicone-based rubber selected from one or more of VMQ, PVMQ, and / or FVMQ. The silicone rubber may include a VMQ silicone. The silicone rubber may be a halogen-free silicone rubber.Properties of VMQ silicone rubbers include softness, low viscosity, good low temperature flexibility, excellent heat resistance, good electrical properties, and medium oil resistance. Vulcanizing agents for silicone rubbers may include peroxides or addition (platinum) curing systems. Processing additives such as platinum-based flame retardants can be employed, such as the patented XIAMETER RMBM 9001, 9004, 9003, 9010, which can be added to improve extrusion. The properties of silicone rubber include good thermal properties and resistance to high and low temperatures, for example, a service temperature ranging from about -110 to 250 °C. Silicone rubber has the widest service temperature of all rubbers and retains physical properties even at high temperatures. Electrical properties may include very good insulation and dielectric properties, high dielectric strength, excellent arc resistance and tracking resistance. Physical properties may include medium to low tensile and tear strength properties, very good compressive strength. Environmental properties may include very good oxidation, ozone and weather resistance, high radiation resistance, moderate to good chemical and oil resistance. Other expected properties may include water repellency, good flame resistance with non-toxic combustion properties.

[0075] The silicone rubber may be any silicone rubber suitable for molded articles and extrusions. For example, the silicone rubber may include ELASTOSIL® silicone rubber. The silicone rubber may be ELASTOSIL® R 401 / 60 silicone rubber (Wacker Chemie AG, Munich, Germany). The thermal insulation composition may include from about 40 to 80% by weight or from about 50 to 70% by weight of a silicone rubber.

[0076] The silicone rubber composition may also include one or more additives. Suitable additives may include, but are not limited to, curing agents, processing aids, adhesion promoters, antioxidants, ultraviolet light stabilizers, fillers, thixotropic agents, additional silicones, dyes / colorants, and combinations thereof.

[0077] The silicone rubber composition may also include various curing agents, including but not limited to, for example, a peroxide. For example, the peroxide curing agent may be a 50% paste of bis-(2,4-dichlorobenzoyl)peroxide in silicone fluid, dicumyl peroxide, or a 45% paste of 2,5-bis-(t-butylperoxy)-2,5-dimethylhexane in silicone rubber. The curing agent may be present in an amount of about 0.1 to 3% by weight, 0.3 to 1% by weight of the silicone rubber composition. An additional organic peroxide may be employed in the composition. The additional organic peroxide may be, for example, a monofunctional organic peroxide. The organic peroxide may be, for example, di(2,4-dichlorobenzoyl)peroxide. The organic peroxide may be present, for example, from 0 to 5% by weight, from 0.1 to 3% by weight or from 0.5 to 2% by weight of the thermal insulation composition.

[0078] The silicone rubber composition may also include various fillers, such as a ground silica filler SiO2. The fillers may be employed at a concentration of between about 0 and about 30% by weight, about 1 and about 20% by weight, about 5 and about 15% by weight, or about 10 and about 12% by weight of the silicone rubber composition.

[0079] The silicone rubber composition may also include various flame retardants. Any suitable flame retardant known in the art may be employed. For example, the flame retardant may be a zinc borate. The zinc borate may be a zinc borate hydrate. The zinc borate may be a dodecaboron tetrazinc docosaoxide heptahydrate. The zinc borate may release its water of hydration at temperatures exceeding about 290°C (554°F). The zinc borate may have a chemical formula 2 ZnO3B2O3 3.5 H2O. Zinc borate can have an average particle size by laser diffraction of 9 micrometers (e.g., FIREBRAKE® ZB, US Borax, Inc.), 2.1 micrometers (e.g., FIREBRAKE® ZB-Fine), or 1.8 micrometers (e.g., FIREBRAKE® ZB-XF).The flame retardant may be present in an amount of about 1 wt% to about 5 wt%, about 2 wt% to about 4 wt%, or about 3 wt% to about 4 wt% in the silicone rubber composition.

[0080] The silicone rubber composition may also include various pigments or colorants, for example from 0.1 to 5% by weight, from 0.2 to 3% by weight of the composition.

[0081] Various additional additives such as antioxidants, or process aids, may be employed in the thermal insulation composition, for example from about 0 to 3% by weight, or from 0.1 to 2% by weight.

[0082] Optionally, any suitable adhesive may be employed between the layers. For example, an adhesive may be employed between a silicone rubber layer and a YSZ ceramic substrate layer. The adhesive may be a cyanoacrylate adhesive. For example, the adhesive may be an ethyl cyanoacrylate adhesive such as, for example, a LOCTITE® cyanoacrylate adhesive, e.g., LOCTITE® 406 (Henkel). A primer coat may be employed for surface preparation in conjunction with the adhesive. Any suitable primer coat may be employed. For example, if the adhesive is a cyanoacrylate adhesive, the primer coat may be an aliphatic amine in isopropyl acetate for surface preparation such as, for example, LOCTITE® SF770 primer coat (Henkel).

[0083] Any suitable mixer may be employed to prepare the silicone rubber compositions, which may be prepared by mixing two parts A and B. For example, a rolling mill or a Banbury™ mixer (Farrel Corporation) may be used to mix the various formulations according to the disclosure, for example, according to ASTM D 3182-07. For example, a silicone rubber composition may be prepared and mixed with additives or fillers. The composition may be extruded or molded and cured. The cured composition may be tested for physical properties, flame resistance, and char formation.

[0084] The silicone rubber composition may be extruded over the inner tube or reinforcing layers and may be cured at a temperature between 300°F and 375°F, 300°F and 325°F, or 340°F and 375°F in a molten salt bath. The composition may include a dual catalyst compound and the high temperature catalyst does not cure in an oxygen environment. Silicone temps are 9 to 15 feet per minute in 55 feet of a salt tank.

[0085] [Fig. 4] shows an exemplary 5-layer fire-resistant hose construction process 400 for preparing a fire-resistant hose. A PTFE inner tube 410 may be formed from a composition comprising PTFE. A first reinforcing layer 420 is formed over the PTFE tube 410 using a wire braiding process with a predefined tension, e.g., having an outer diameter OD of 0.55" to 0.59" (inches). A first silicone rubber layer 430 is formed over the first reinforcing layer 420, e.g., by extrusion from a silicone composition comprising a silicone-based rubber. The first silicone layer may have a thickness in a range, for example, from 0.2" to 0.3" or equal to 0.25". The 40 micrometer (0.00157") thick YSZ 440 ceramic substrate layer is wound / wrapped over the silicone thermal insulation layer.The YSZ ceramic substrate layer may be a single layer with or without an overlay. With an overlay, the YSZ ceramic substrate layer forms two layers at the overlays. For example, the extent of the overlay may be from about 20% to about 50% of the overlay area. A second silicone rubber layer 450 is formed over the first reinforcing layer 440, for example, by extrusion from a silicone composition to form an outer layer. The second silicone rubber layer may have a thickness in a range of, for example, 0.1" to 0.2" or equal to 0.125". The fire-resistant pipe 400 may have an outer diameter of 1.32" to 1.35". Larger outer diameters are contemplated.

[0086] To manufacture the fire-resistant hose 100, the inner tube 110 is initially extruded onto a mandrel. If the inner tube 110 includes two or more layers, they may be co-extruded. Next, the hose reinforcement layer 120 is braided onto the inner tube 110 on the mandrel. Subsequently, the first silicone rubber layer 130 is extruded over the hose reinforcement layer 120 and the inner tube 110 on the mandrel. Next, the YSZ ceramic substrate 140 may be laminated or wrapped over the first silicone rubber layer 130. Subsequently, the second silicone rubber layer 150 is extruded over the pipe reinforcing layer 140 onto the mandrel. The assembly may be passed through a water cooling tank to help it set slightly. If a soft mandrel is used, the pipe may then be coiled. The pipe is then placed in an autoclave to be cured. Then the mandrel is ejected from the pipe by means of pressure. It will be borne in mind that the fire-resistant pipe of [Fig. 2] or [Fig. 3] may be manufactured in a similar manner. EXAMPLES

[0087] Example 1. Silicone composition

[0088] A representative silicone rubber composition is shown in Table 2.

[0089] Table 2. Silicone composition Description Quantity (lbs) % pcc Elastosil® Silicone Rubber ELR401 / 60 109.0 68.1 95-105 FR3 Fire Resistant Fluid (Xia meter®RBM-9003 modifier) ​​20.7 12.9 15-25 Minusil 5 micron - ground silica SiO2 18.5 11.6 15-25 Di-Cup 40KE - dicumyl peroxide catalyst 0.8 0.5 0.5-2 Soligum Red Rubber 058 1.2 0.8 0.5-2 CM 126 Black Silicone 0.4 0.2 0.5-2 Silogum Blue 211 2.2 1.4 1-3 Firebrake ZB - zinc borate flame retardant 5.5 3.4 3-8 Perkadox PD-50S-PS-A - organic peroxide 1.7 1.1 1-3 Totals 160.0 100

[0090] More particularly, a silicone rubber was prepared from the composition of Table 2 by mill mixing. The samples were cured for 10 min at 300°F (149°C). A pipe may be cured, for example, at a temperature between about 300°F and 375°F, about 300°F and about 325°F, or about 340°F and about 375°F in a molten salt bath.

[0091] Physical properties were tested in accordance with ASTM D412 (tensile, elongation-modulus); ASTM D2240 (hardness); ASTM D624 (tear strength, Die C); flame testing was conducted in accordance with MSHA ASTP5007 per 30 CFR §18.65; and char formation is a visible test per MSHA ASTP5007; Shore hardness testing A was made in accordance with ASTM D 2240-95, for example using an Instron calibrated automatic durometer. Durometer hardness, Shore A 70+ / -5; tensile > 750 psi; percent elongation > 150%; tear strength, Die C > 50; specific gravity 1.42+ / -0.03.

[0092] Example 2. Flame test

[0093] A flame test was conducted according to a flame test procedure of MSHA ASTP 5007 per 30 CFR Part 18, § 18.65. Prepared samples included a silicone composition similar to Table 2 and cured. Test specimens of cured silicone rubber test samples were subjected to the flame test. Test specimens were mounted to support the holder with ring clamping and wire gauze inside the test cabinet. A variable speed electric fan and an ASME flow nozzle to achieve constant air velocities between 50 and 500 feet per minute were used. A Pittsburgh-Universal Bunsen-type burner is mounted in the test cabinet and is set to give a 3-inch high blue flame with natural gas. The specimen was held 4" from the flame in a vertical position. The burner flame was applied to the free end of the specimen.After 1 minute, the burner flame is removed, the fan is turned on to give an airflow of 300 feet per minute and the flame duration is measured using a stopwatch. The samples were placed between an industrial blow torch and a thermocouple, having a sensing range temperature of 2,000 °F and a heat input of: 4,500 Btu / h. The samples were tested with an industrial burner torch at a temperature > 2,000 °F. The test duration for all samples was 5 minutes.

[0094] Several iterations of possible fire-resistant pipe formats were tested.

[0095] The layer format and results for the flame test are shown in Table 3. Layer 1 is closest to the blow torch flame.

[0096] Table 3. Pipe construction for flame test Iteration Layer 1 Layer 2 Layer 3 Layer 4 Visual Appearance 1 0.125" Silicone Rubber 0.25" Silicone Rubber N / A The sample burned completely. Silicone char formation and shedding were noticeable on the first and second layers. 2 0.125" Silicone Rubber YSZ 40 micron Ceramic Substrate 0.25" Silicone Rubber N / A Slight char formation was observed on the front of the second silicone. However, no swelling or burning of silicone on the back side of the second silicone layer was observed. 3 YSZ ceramic substrate 40 micron very Silicone rubber 0.12 5" YSZ ceramic substrate 40 micron very Silicone rubber cone 0.25" The burn of the first silicone layer was localized and did not extend to the ends as in iteration 2. The front of the second silicone layer was pristine as well as the back side. 4 Silicone Rubber 0.123" S / OS / OS / O Only one layer of silicone was tested. The sample burned completely. Cracks were noted on the back side of the layer. 5 Ceramic Substrate YSZ 40 micron Silicone Rubber 0.123" S / OS / O The front layer showed no char formation. The burn was localized and the char / cracks did not extend to the ends. The back side of the silicone was pristine with no char formation or visible cracks.

[0097] Based on the flame test results, a heat-resistant layer format comprising a YSZ ceramic substrate layer sandwiched between two silicone rubber layers (iteration 2) was selected for fire-resistant pipe construction.

[0098] Example 3. Fire resistant pipe comprising an inner PTFE core tube and an outer thermal insulation layer comprising a YSZ ceramic substrate

[0099] A prototype pipe is prepared according to the invention, comprising an inner tube 110 PTFE (PTFE 62X from Chemours). A braided reinforcement layer of 304 stainless steel is applied using a braiding process with a predefined tension to prepare a reinforced tube having an outside diameter (OD) of 0.55" to 0.59". A first layer of silicone rubber 130 is extruded over the reinforcement layer to a thickness of 0.25", a layer of YSZ ceramic substrate 140 is wound over the 130 layer, and a second outer layer of silicone rubber 150 according to Table 2 is extruded over the YSZ 140 ceramic substrate layer to a thickness of 0.125". The cured pipe has an outside diameter OD of 1.32" to 1.35". After curing, the pipe meets the fire performance requirements of AS 1055 and TSO under no-flow conditions, passes the flame test per MSHA ASTP5007, and exhibits good external char formation.

[0100] Aspects

[0101] In a first aspect, a fire resistant pipe is provided, comprising a thermal insulation layer comprising a yttria stabilized zirconia (YSZ) ceramic substrate layer disposed between a first silicone rubber layer and a second silicone rubber layer.

[0102] In a second aspect, the fire resistant pipe further comprises an inner tube layer prepared from a composition comprising polytetrafluoroethylene (PTFE).

[0103] In a third aspect, the fire resistant pipe further comprises a reinforcing layer.

[0104] In a fourth aspect, the reinforcing layer is disposed between the inner tube layer and the thermal insulation layer.

[0105] In a fifth aspect, the fire resistant pipe of any one of the preceding aspects comprises a YSZ ceramic substrate layer comprising zirconia (ZrO2), and from about 3 mol% to about 8 mol% yttrium oxide (Y2O3).

[0106] In a sixth aspect, the fire resistant pipe of any one of the preceding aspects comprises a YSZ ceramic substrate layer having a thickness of about 20 micrometers to about 100 micrometers.

[0107] In a seventh aspect, the fire resistant hose of any one of the preceding aspects comprises the first and second silicone rubber layers prepared from a silicone rubber composition comprising from about 40 to 80% by weight, or from about 50 to 70% by weight of a silicone-based rubber.

[0108] In an eighth aspect, the silicone rubber composition of the seventh aspect comprises an additive selected from the group consisting of curing agents, process aids, flame retardants, adhesion promoters, antioxidants, ultraviolet light stabilizers, fillers, thixotropic agents, additional silicones, dyes and colorants.

[0109] In a ninth aspect, the silicone rubber composition according to the eighth aspect comprises a ground silica filler in an amount of between about 0 and 30% by weight, 1 and 20% by weight, 5 and 15% by weight or about 10 and 12% by weight.

[0110] In a tenth aspect, the silicone rubber composition comprises a flame retardant comprising a zinc borate.

[0111] In an eleventh aspect, the reinforcing layer of the fire resistant hose comprises a metal braid, optionally a stainless steel metal braid.

[0112] In a twelfth aspect, the fire resistant hose comprising a multiplicity of layers from an inner radial direction to an outer radial direction comprising: i) an inner tube layer prepared from a composition comprising a PTFE; ii) a first reinforcing layer comprising a metal braid; iii) a first layer of silicone rubber; iv) a YSZ ceramic substrate layer; and v) a second layer of silicone rubber.

[0113] In a thirteenth aspect, the fire resistant hose of any one of the preceding aspects comprises first and second layers of silicone rubber having one or more of:

[0114] i) a hardness of 65 to 75 Shore A according to ASTM 2240;

[0115] ii) a tensile strength of at least 750 psi according to ASTM D412;

[0116] iii) a percentage elongation of at least 150% according to ASTM D412;

[0117] iv) a tear strength of at least 50 Die C according to ASTM D624;

[0118] v) a 50% modulus of 250 to 350 psi according to ASTM D412; and

[0119] vi) a 100% modulus of 300 to 450 psi according to ASTM D412.

[0120] In a fourteenth aspect, the fire resistant pipe comprises a composition of cured silicone rubber with a thermal insulation layer that passes a flame test when tested according to MSHA ASTP5007; and exhibits significant external visible char formation when tested according to MSHA ASTP5007.

[0121] In a fifteenth aspect, the fire resistant pipe meets or exceeds the performance requirements of AS 1055 and TSO at 15 minutes under zero flow conditions.

[0122] In a sixteenth aspect, the fire resistant pipe is qualified for a continuous operating temperature range of -65°F to 450°F (-54°C to 232°C).

[0123] In a seventeenth aspect, there is provided a method of manufacturing a fire resistant pipe comprising:

[0124] forming an inner tube layer prepared from a composition comprising a PTFE;

[0125] braiding a first reinforcing layer comprising a metal braid over the inner tube layer;

[0126] extruding a first silicone rubber composition over the reinforcing layer;

[0127] laminating a layer of YSZ ceramic substrate onto the first layer of silicone rubber;

[0128] extruding a second silicone rubber composition over the YSZ ceramic layer to form a green pipe; and curing the green pipe to form the fire-resistant pipe.

[0129] In an eighteenth aspect, the method of manufacturing a fire resistant pipe comprises the YSZ ceramic substrate layer comprising zirconia (ZrO2) and from about 3 mol% to about 8 mol% yttria (Y2O3).

[0130] In a nineteenth aspect, the method of manufacturing a fire-resistant pipe comprises the YSZ ceramic substrate layer having a thickness ranging from about 20 micrometers to about 100 micrometers.

[0131] In a twentieth aspect, the method of manufacturing a fire resistant hose comprises the first and second silicone rubber layers prepared from a silicone rubber composition comprising from about 40 to 80% by weight, or from about 50 to 70% by weight of a silicone-based rubber.

[0132] In a twenty-first aspect, the method of manufacturing a fire-resistant hose comprises the silicone rubber composition comprising an additive selected from the group consisting of curing agents, process aids, flame retardants, adhesion promoters, antioxidants, ultraviolet light stabilizers, fillers, thixotropic agents, additional silicones, dyes and colorants.

[0133] In a twenty-second aspect, the method of manufacturing a fire resistant hose comprises the silicone rubber composition comprising a ground silica filler in an amount of between about 0 and 30 wt%, 1 and 20 wt%, 5 and 15 wt%, or about 10 and 12 wt%.

[0134] In a twenty-third aspect, the method of manufacturing a fire-resistant hose comprises the silicone rubber composition comprising a flame retardant comprising a zinc borate.

[0135] In a twenty-fourth aspect, the method of manufacturing a fire-resistant hose comprises a reinforcing layer comprising a metal braid, optionally a stainless steel metal braid.

Claims

Claims

1. A fire-resistant pipe comprising a thermal insulation layer comprising a yttria-stabilized zirconia (YSZ) ceramic substrate layer disposed between a first silicone rubber layer and a second silicone rubber layer, wherein the YSZ ceramic substrate layer comprises zirconia (ZrO2) and from about 3 mol% to about 8 mol% yttria (Y2O3)

2. The fire resistant pipe of claim 1, further comprising an inner tube layer prepared from a composition comprising polytetrafluoroethylene (PTFE).

3. The fire resistant pipe of claim 2, further comprising a reinforcing layer, optionally wherein the reinforcing layer is disposed between the inner tube layer and the thermal insulation layer, optionally wherein the reinforcing layer comprises a metal braid, optionally a stainless steel metal braid.

4. A fire-resistant pipe according to any one of claims 1 to 3, wherein the YSZ ceramic substrate layer has a thickness ranging from about 20 micrometers to about 100 micrometers.

5. The fire-resistant hose of any one of claims 1 to 4, wherein the first and second silicone rubber layers are prepared from a silicone rubber composition comprising from about 40 to 80% by weight, or from about 50 to 70% by weight of a silicone-based rubber, optionally wherein the silicone rubber composition comprises an additive selected from the group consisting of curing agents, process aids, flame retardants, adhesion promoters, antioxidants, ultraviolet light stabilizers, fillers, thixotropic agents, additional silicones, dyes, and a colorant, further optionally wherein the silicone rubber composition comprises a ground silica filler in an amount of from about 0 to 30% by weight, 1 to 20% by weight, 5 to 15% by weight, or about 10 to 12% by weight. weight.

6. A fire resistant hose according to claim 5, wherein the silicone rubber composition of the first and / or second silicone rubber layers include a flame retardant comprising zinc borate.

7. A fire resistant hose according to any one of claims 1 to 6, comprising a multiplicity of layers from an inner radial direction to an outer radial direction comprising: i) an inner tube layer prepared from a composition comprising a PTFE; ii) a first reinforcing layer comprising a metal braid; iii) a first layer of silicone rubber; iv) a layer of YSZ ceramic substrate; and v) a second layer of silicone rubber.

8. The fire-resistant hose of any one of claims 1 to 7, wherein the first and second silicone rubber layers have i) a hardness of 65 to 75 Shore A according to ASTM 2240-95; ii) a tensile strength of at least 750 psi according to ASTM D412; iii) a percentage elongation of at least 150% according to ASTM D412; iv) a tear strength of at least 50 Die C according to ASTM D624 Type C; v) a 50% modulus of 250 to 350 psi according to ASTM D412; and vi) a 100% modulus of 300 to 450 psi according to ASTM D412.

9. The fire-resistant hose of any one of claims 1 to 8, wherein the cured silicone rubber composition with a thermal insulation layer passes a flame test when tested in accordance with MSHA ASTP5007 per 30 CFR §18.65; and exhibits significant external visible char formation when tested in accordance with MSHA ASTP5007.

10. A fire resistant hose according to any one of claims 1 to 9, wherein i) the hose meets or exceeds the performance requirements of SAE AS 1055 and TSO C53a of 15 minutes under zero flow conditions; and ii) the pipe is sized for a continuous operating temperature range of -65°F to +450°F (-54°C to +232°C).

11. A method of manufacturing the fire-resistant pipe according to any one of claims 1 to 10 comprising: forming an inner tube layer prepared from a composition comprising a PTFE; braiding a first reinforcing layer comprising a metal braid over the inner tube layer; extruding a first silicone rubber composition over the reinforcing layer; rolling a yttria-stabilized zirconia (YSZ) ceramic substrate layer over the first silicone rubber layer; extruding a second silicone rubber composition over the YSZ ceramic layer to form a green pipe; and curing the green pipe to form the fire-resistant pipe.

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