TUBULAR ASSEMBLY COMPOSED OF LOW DENSITY POLYARYLENE SULFIDE FOAM, LOW THERMAL CONDUCTIVITY AND LOW THERMAL EFFUSION

Abstract

A polyarylene sulfide (PAS) foam layer that circumscribes a hollow inner tube and may have a density reduction of 50% or more with respect to the density of an unfoamed PAS polymer material and / or a thermal conductivity reduction of 50% or more with respect to the thermal conductivity of an unfoamed PAS polymer material and / or a thermal effusivity reduction of 50% or more with respect to the thermal effusivity of an unfoamed PAS polymer material. The PAS foam layer can have a low density (e.g., less than 0.67 g / cc) and / or low thermal conductivity (e.g., between 0.017 W / (mK) and 0.145 W / (mK)) and / or low thermal effusivity (e.g., less than 316 Ws1 / 2 / m2 / K, optionally between 38 Ws1 / 2 / m2 / K and 316 Ws1 / 2 / m2 / K) even at high temperatures (e.g., above approximately 204 degrees Celsius (°C) (400 degrees Fahrenheit (°F)).Such a PAS foam layer may have characteristics appropriate for use as part of a steam hose.

Description

The present invention relates in general to fluid-carrying tubular assemblies, and more particularly to steam-carrying tubular assemblies. BACKGROUND OF THE INVENTION Multi-layered tube bundles are commonly used to transport steam and other fluids, such as oil and gas. Steam carrier tubes and hoses are used in various industries, including chemical plants, oil refineries, steel mills, foundries, power plants, and shipyards. For example, PARKER TEMPTUBES® are pre-insulated tube bundles installed in steam manifolds to transport steam for applications such as thermal tracing of process piping. The standard construction of a steam hose in the thermal insulation industry involves a central metal tube, one or more layers of fiberglass or woven insulation, a polyimide tape to hold the insulation in place, and an outer polymer jacket. Wrapping the fiberglass or woven insulation and polyimide tape around a metal tube can be time-consuming. Furthermore, the fiberglass fibers in the insulation can pose a safety hazard to operators, so they require specialized protective equipment when working with steam hoses containing fiberglass. Operators must also take extra precautions when working with fiberglass to avoid exposure (for example, by covering the entire taping line with glass covers and using respirators and other specialized personal protective equipment). Furthermore, the manufacture of such fiberglass steam hoses requires a two-step, discontinuous process, which includes tape wrapping followed by polymer extrusion, due to the need to change the fiberglass or polyimide tape reels or to tape tearing. For example, an entire tape line must be stopped for troubleshooting, which can adversely affect the extrusion process or increase the complexity of process control. Therefore, the two steps are not performed simultaneously in the same continuous steam hose. This batch process requires at least two operators, one to wrap the fiberglass and another to extrude the polymer jacket. Furthermore, fiberglass tape cannot retain its thermal properties in the presence of moisture, can release chlorine when exposed to moisture (for example, causing corrosion in adjacent metal piping), can injure field operators, or make handling and installation unpleasant. Additionally, Zn / nLn / Lznz / E / Yii fiberglass tape is often coated with a polymer jacket to protect the fiberglass tape; such polymer jackets can make the pipe heavy and difficult to handle. Outside of steam hoses, some polymer foam materials are known. For example, polymer foam sheets, such as compression-molded sheets of open-pore polyphenylene sulfide (“PPS”) foam with a closed surface, have been described in U.S. Patent Application No. 5,716,999 (Patent '999) issued on February 10, 1998. BRIEF DESCRIPTION OF THE INVENTION The present application provides a polyarylene sulfide (“PAS”) foam layer that circumscribes a hollow inner tube and may have a density reduction of 50% or more with respect to the density of an unfoamed PAS polymer material and / or a thermal conductivity reduction of 50% or more with respect to the thermal conductivity of an unfoamed PAS polymer material and / or a thermal effusivity reduction of 50% or more with respect to the thermal effusivity of an unfoamed PAS polymer material. As an example, the PAS foam layer may have a low density (e.g., less than 0.67 g / cc) and / or a low thermal conductivity (e.g., between 0.017 W / (mK) and 0.145 W / (mK)) and / or a low thermal effusivity (e.g., less than 316 Ws1 / 2 / m2 / K, optionally between 38 Ws1 / 2 / m2 / K and 316 Ws1 / 2 / m2 / K) even at high temperatures (e.g., above approximately 204 degrees Celsius (°C) (400 degrees Fahrenheit (°F)).Such a PAS foam layer may have characteristics appropriate for use as part of a steam hose. With reference again to the PAS foam layer described in this application, said PAS foam layer can perform the function of three or more layers of previously known tube assemblies using fiberglass / fabric insulation, polyimide tape, and an outer polymer sleeve. For example, the thermal conductivity of a PAS foam layer can be approximately -0.020 W / (mK), approximately 50% of the thermal conductivity of fiberglass tape, and the PAS foam layer may be relatively unaffected by temperature increases. Consequently, the PAS foam layer enables more effective and reliable thermal performance at high temperatures compared to fiberglass tape, and therefore fiberglass is not required for tube assemblies that include the PAS foam layer.Since fiberglass tape is not required, the PAS foam layer allows for improved worker safety by eliminating or reducing the presence of fiberglass. Compared to fiberglass tape, the PAS foam layer has a much lower density and thermal conductivity. The lower density allows pipe assemblies made with the PAS foam layer to be lighter, more flexible, and easier to route and handle during installation. Furthermore, the much lower thermal conductivity allows the PAS foam layer to have a thickness that fits a smaller wrap without a reduction in performance compared to fiberglass tape. The PAS foam layer has a much lower thermal inertia compared to the outer jacket of a fiberglass-wrapped tube. This promotes worker safety by raising the surface temperature threshold for burns when human skin inadvertently comes into contact with a hot surface. Therefore, the risk of burns to human skin during a given contact time is considerably reduced with a PAS foam tube compared to a fiberglass-wrapped tube with a non-foamed outer jacket. The PAS foam layer allows for faster and more economical installation and maintenance. For example, pipe assemblies with the PAS foam layer do not require expensive umbilical end termination sleeves, clamps, or moisture sensors. The PAS foam layer can be formed on the hollow inner tube in a single continuous processing step. Continuous formation of the PAS foam layer allows for higher line speeds compared to previously known batch processes, thus increasing productivity. For example, the PAS foam layer can be extruded onto the hollow inner tube, unlike the two or more batch process steps required to produce fiberglass-wrapped tubes with a polymer jacket. The PAS foam layer allows for reduced manufacturing and supply chain costs. For example, the continuous formation of the PAS foam layer eliminates secondary processes such as winding, unwinding, and storing materials (e.g., fiberglass tape) used in the batch production of fiberglass-wrapped tubes. Producing the tube assembly with the PAS foam layer reduces labor costs, as the assembly can be performed by a single operator, unlike the two operators required to produce fiberglass-wrapped tubes (e.g., one for each batch step).Supply chain costs can be reduced, compared to previously known fiberglass-wrapped tube assemblies, since tube assemblies that include the PAS foam layer can have fewer components (e.g., the PAS foam layer instead of the fiberglass and polymer sleeve). PAS foam allows for more robust thermal performance of a steam pipe than fiberglass-wrapped pipes. For example, in one configuration, the cellular structure of the PAS foam layer has thermal performance that is unaffected or minimally affected by twisting, bending, or mechanical routing (e.g., imposed in the field during installation). zn / nLn / Lznz / E / Yii Furthermore, in one configuration, although the foam insulation is low-density, it is more resistant to crushing and / or abrasion than the polymer sleeve of fiberglass-wrapped tubes. Consequently, the tie-down straps that wrap around the PAS foam tube assembly can be tightened more than the tie-down straps for the polymer sleeve of fiberglass-wrapped tubes. For example, if, due to an installer error, the tie-down straps that wrap around the PPS foam tube assembly are too tight, the PAS foam tube assembly may still function effectively, whereas the effectiveness of the polymer sleeve of the fiberglass-wrapped tubes could be significantly reduced if the same amount of tightness is applied. In some applications, multiple insulated bundles are installed close together and routed in flat cable trays. Several cable trays, each containing multiple insulated bundles, are sometimes stacked on top of each other. A minimum spacing of 1.27 cm (0.5 in.) is generally maintained between two bundles or between two cable trays to prevent damage to the outer jacket from temperature rise, thermal degradation, and / or brittleness. In one configuration, the PAS foam layer is more stable at high temperatures than the polymer jacket of fiberglass-wrapped tube assemblies. Therefore, a 1.27 cm (0.5 in.) spacing between each PAS foam tube or cable tray containing the PAS foam tube is not required.Therefore, the PAS foam layer allows for space savings when installed and / or reduces the required amount of expensive construction materials (e.g., cable trays, channel struts) and / or increases the number of PAS foam tubes that can be installed within the same footprint. According to one aspect, a tubular assembly includes a first tubular member having an outer surface and an inner surface, wherein the inner surface defines a more interior surface of the assembly, and a second tubular member surrounding the outer surface of the first member, wherein the second member comprises a foamed polyarylene sulfide polymeric material having a foamed density and a foamed thermal effusivity that is foamed from an unfoamed polyarylene sulfide polymeric material having an unfoamed density and an unfoamed thermal effusivity, the foamed density being less than approximately 50% of the unfoamed density, and the foamed thermal effusivity being less than approximately 50% of the unfoamed thermal effusivity. According to another aspect, a tubular assembly includes a first tubular member having an outer surface and an inner surface, wherein the inner surface defines a more interior surface of the assembly, and a second tubular member surrounding the outer surface of the first member, wherein the second member comprises a foamed polyarylene sulfide polymeric material having a foamed thermal conductivity that is foamed from a non-foamed polyarylene sulfide polymeric material having a non-foamed thermal conductivity, the foamed thermal conductivity being at least approximately 50% lower than the non-foamed thermal conductivity. The above and other features of the invention are described below in more detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an oblique view of an exemplary tube assembly with an inner and outer layer of foamed polyarylene sulfide (PAS) that has been separated into two parts. Figure 2 is an oblique view of the tube assembly in Figure 1 where a portion of the end of the foamed PAS outer layer has been removed from the inner layer. Figure 3 is an oblique view of the tube assembly in Figure 2, which also includes an adapter attached to the inner layer. Figure 4 is a side view of the tube assembly in Figure 3. Figure 5 is a top view of a partial cross-section of the tube assembly in Figure 4 illustrating the inner cells of the foamed PAS outer layer. Figure 6 is a schematic illustration of the PPS polymeric material being extruded onto the inner layer of Figure 1. Figure 7 is an oblique view of another exemplary tube assembly that includes an intermediate layer between an inner and outer layer of foamed PAS. Figure 8 is an oblique view of another exemplary tube assembly that includes a layer of foamed PAS as an intermediate layer along with other intermediate layers. Figure 9 is an oblique view of another exemplary tube assembly that includes multiple inner layers and an intermediate layer between the inner layers and an outer layer of foamed PAS. Figure 10 is an oblique view of another exemplary tube assembly that includes multiple inner tubes circumscribing multiple inner layers and an intermediate layer between the inner layers and an outer layer of foamed PAS. Figure 11 is an oblique view of another exemplary tube assembly that includes a heating element, an intermediate layer surrounding the heating element and an inner layer, and an outer layer of foamed PAS. DETAILED DESCRIPTION OF THE INVENTION The principles of this present application have particular application to tube assemblies configured to convey high-temperature fluids, such as steam, and will therefore be described below primarily in this context. It is understood that the principles of this invention may be applicable to other tube assemblies where it is desirable to convey fluids, such as high-temperature liquids. zn / nLn / Lznz / E / Yii Some terminology may be used in the following description for convenience rather than for any restrictive purpose. For example, “thermal conductivity” may be understood to mean the effective thermal conductivity of a polymer foam that governs the overall heat transfer from one end of the foam to the other. Effective thermal conductivity is the combined result of heat conduction through the solid phases, heat conduction through the fluid phases, convective heat transfer between the fluid and solid phases caused by fluid motion, and radiative heat transfer. Thermal effusivity can be understood as the ability of a material to exchange thermal energy with its surroundings. It is a measure of a body's thermal inertia and is given by the square root of the product of a material's density, thermal conductivity, and heat capacity. “Density reduction” or “density reduction” can be understood as a percentage reduction in the density of a foamed material, based on the density of the non-foamed starting material measured under the same environmental conditions. “Reduction of thermal conductivity” and “reduction of thermal conductivity” can be understood as the percentage reduction of the thermal conductivity of a foamed material, based on the thermal conductivity of the non-foamed starting material measured under the same environmental conditions. “Reduction of thermal effusivity” and “reduction of thermal effusivity” can be understood as the percentage reduction of the thermal effusivity of a foamed material, based on the thermal effusivity of the non-foamed starting material measured under the same environmental conditions. “Fiberglass tape” may include, among others, insulating tapes made of fiberglass or woven fiberglass. It can be understood that “fiberglass wrapped tube” means any tube or tubular assembly that contains a fiberglass tape wrapped as one of the construction layers. The “moisture sealant” may include one- or multi-part sealants, epoxies, and resins that are typically used to hermetically seal an umbilical end to prevent moisture from entering. “Umbilical” may refer to the final composite product supplied for steam and / or heat tracing applications. Such a final composite product may contain single or multiple process tubes / hoses that may or may not be individually insulated or heat traced. zn / nLn / Lznz / E / Yi “Termination sleeves” may include thermoplastic and / or thermosetting methods of beam end terminations to provide a watertight seal of an umbilical end. "Cable trays" can refer to the installation / routing of umbilicals in an application. Cable trays provide a way to support and secure umbilicals in an installation. The “enclosure” may include, among other things, thermoplastic / metallic junction boxes where two or more umbilicals can be joined or divided into additional sections of a process flow. “Resin” may include, but is not limited to, a polymeric material (e.g., a PAS or PPS polymeric material) and an additive (e.g., a plasticizer, compatibilizer and / or antioxidant). Furthermore, it should be noted that terminology of similar importance other than the words specifically mentioned above is used for convenience purposes and not in a limiting sense. With reference now to the drawings and initially to Figure 1, a steam tube assembly (an example of a tubular assembly) is generally designated by the reference number 20. The steam tube assembly 20 includes an inner tube 22 (an example of a first tubular member) and an outer tube 24 (an example of a second tubular member). In one embodiment, the tubular assembly is part of a multi-tube bundle, hose, fiber optic cable, or electrical cable. In another embodiment, the tubular assembly is part of a connector or umbilical conduit. The inner tube 22 and the outer tube 24 are not joined. For example, in some embodiments, the outer tube 24 can be separated (for example, by cutting the outer tube 24 at an axial location) into a main part 24a and an end part 24b. As exemplified in Figure 2, the end part 24b is not attached to the radially outward-facing surface of the inner tube 22 and can be removed from the inner tube 22 by sliding it out of the inner tube 22. The opposite axial end of the steam tube assembly 20 may be identical. For example, each end of the inner tube 22 is uncovered. In another embodiment, only one end of the outward-facing radial surface of the inner tube is uncovered by the outer tube. In yet another embodiment, both ends of the outward-facing radial surface of the inner tube are covered by the outer tube. In one embodiment, the radially outward-facing surface of the inner tube and the outer tube are continuously bonded together. A bonding agent may or may not be incorporated as an additional layer. For example, in one embodiment, the bonding agent is an adhesive, surface modifier, resin, fixative, solvent, thermoplastic (e.g., a thermoplastic elastomer or thermoplastic vulcanized material), thermoset, a Zn / nLn / Lznz / E / Yi rubber material, and / or a mechanical encapsulation structure. In another embodiment, the inner and outer tubes are bonded together randomly or sequentially. After cutting the outer tube 24 and removing the end portion 24b, it is not necessary to seal the exposed end of the main portion 24a during storage or installation without risk of exposing the installer to fiberglass, or without risk of moisture damaging the main portion 24a. For example, fiberglass is not part of the steam pipe assembly 20. In another configuration, fiberglass is incorporated into the steam tube assembly. For example, as an intermediate layer between the inner and outer tubes. In another example, the fiberglass is a layer that surrounds the outer tube. Returning briefly to Figure 3 and Figure 4, and then again to Figure 2, the steam tube assembly 20 may include an adapter 30. For example, after the end portion 24b (shown in Figure 1 and Figure 2) of the outer tube 24 is removed from the inner tube 22, the adapter 30 is attached to the inner tube 22. The opposite axial end of the steam tube assembly 20 may be identical. For example, each end includes an adapter 30 attached to a respective end of the inner tube 22. In the example shown, adapter 30 includes a threaded end and a wrench-receiving portion. In one embodiment, the adapter is another adapter suitable for connecting the ends of steam tube assemblies together, such as a quick-coupling adapter. In another embodiment, only one end of the steam tube assembly includes the adapter. In yet another embodiment, the steam tube assembly does not include an adapter. Referring again to Figure 2, the inner tube 22 has an outer surface and an inner surface that defines a fluid path. For example, the inner tube 22 is made entirely of a homogeneous metal, such as stainless steel or copper, and is configured to carry steam. In one embodiment, the inner tube is configured to carry high-temperature liquids. In another embodiment, the inner tube includes a metal alloy, a metal mixture, a metal composite, a polymer, a polymer composite, a polymer alloy, a polymer mixture, and / or a polymer-metal composite. In yet another embodiment, the inner surface of the inner tube is solid, foamed, porous, corrugated, coiled, and / or molded. In another configuration, the inner tube is a coiled metal wire, an electrical cable, and / or a fiber optic cable. For example, in some of these configurations, a non-hollow component, such as copper wire or fiber optic fibers, takes the place of the inner tube. In some other configurations, the inner tube is absent, and only the outer tube is present. zn / nLn / Lznz / E / Yii The outer tube 24 surrounds the outer surface of the inner tube 22 and is made of a foamed polyarylene sulfide (PAS) polymer material. Figure 1 illustrates the outer tube 24 in a cut state, in which the end portion 24b can be removed. In an uncut state, the main portion 24a and the end portion 24b form a continuous piece, creating a single, radially outward-facing continuous surface. In one embodiment, this single, radially outward-facing continuous surface extends axially along the entire length of the steam tube assembly. The outer tube 24 can define a further outer surface of the steam tube assembly 20. In another embodiment, the outer tube is enclosed by one or more outer layers. For example, an outer cover layer can enclose multiple tube assemblies, each of which includes a respective inner and outer tube, as exemplified in Figure 10 and explained later. The outer cover layer can be made of foamed polyarylene sulfide polymer material. The outer tube 24 is formed from a single layer of foamed polyarylene sulfide polymer material. As discussed previously, the outer tube 24 is in contact with, but not chemically bonded to, at least a portion of the radially outward surface of the inner tube 22, thereby allowing the end portion 24b to slide relative to the inner tube 22 after the end portion 24b is cut from the main portion 24a. In another embodiment, the steam tube assembly includes an intermediate layer, as exemplified in Figure 7 and explained below, with which the outer tube is in contact but not chemically bonded. In one embodiment, the outer tube comprises two or more layers of foamed polyarylene sulfide polymer material. Each layer of the outer tube may have a similar or different reduction in density, a similar or different reduction in thermal conductivity, a similar or different reduction in thermal effusivity, and / or a similar or different cell morphology. In some embodiments, the outer and inner tubes are absent, and instead, the PAS polymer material is formed into a different shape. For example, in some such embodiments, the PAS polymer material is formed into a sheet. In other embodiments, the PAS polymer material is formed in a tube that is not combined with another component. In further embodiments, the PAS polymer material is formed in a tube that is not combined with an inner tube (for example, the PAS material can form the innermost radial surface for conveying steam without a separate metal tube radially extending into the PAS material). The foamed PAS polymer material forming the outer tube 24 has a density reduction of 86% to 90%, a thermal conductivity reduction of 90% to 94%, and a thermal effusivity reduction of 88% to 94% with respect to the corresponding zn / nLn / Lznz / E / Yii values ​​of a non-foamed PAS polymer material. For example, foamed PAS polymer material is classified as a low-density, low thermal conductivity, and low thermal efusivity foam with a density of less than 0.188 grams per cubic centimeter (g / cc), a thermal conductivity of less than 0.029 watts per meter-kelvin W / (mK), and a thermal efusivity of less than 76 Ws1 / 2 / m2 / K, while PAS polymer material before foaming has a density of 1.340 g / cc, a thermal conductivity of 0.290 W / (mK), and a thermal efusivity of 632 Ws1 / 2 / m2 / K.As discussed below, the reduction of density and / or the reduction of thermal conductivity and / or the reduction of thermal effusivity can be controlled and adjusted by varying (1) the nature, type and / or formulation of a foaming agent used to foam the unfoamed PAS polymeric material; (2) the nature, type and / or formulation of the PAS polymeric material, with or without additives; and / or (3) the processing equipment, processing conditions and / or related tools. In another embodiment, the foamed PAS polymer material that forms the outer tube has a density reduction of 68% to 86%, a thermal conductivity reduction of 71% to 94%, and a thermal effusivity reduction of 68% to 94% with respect to the corresponding values ​​of a non-foamed PAS polymer material. For example, foamed PAS polymer material has a density of 0.429 g / cc to 0.188 g / cc, a thermal conductivity of 0.084 W / (mK) to 0.017 W / (mK) and a thermal efusivity of 202 Ws1 / 2 / m2 / K to 38 Ws1 / 2 / m2 / K, while PAS polymer material before foaming has a density of 1.340 g / cc, a thermal conductivity of 0.290 W / (mK) and a thermal efusivity of 632 Ws1 / 2 / m2 / K. In another embodiment, the foamed PAS polymeric material that forms the outer tube has a density reduction of 63% to 68%, a thermal conductivity reduction of 63% to 90%, and a thermal effusivity reduction of 63% to 88% with respect to the corresponding values ​​of a non-foamed PAS polymeric material. For example, foamed PAS polymer material has a density of 0.496 g / cc to 0.429 g / cc, a thermal conductivity of 0.107 W / (mK) to 0.029 W / (mK) and a thermal efusivity of 234 Ws1 / 2 / m2 / K to 76 Ws1 / 2 / m2 / K, while PAS polymer material before foaming has a density of 1.340 g / cc, a thermal conductivity of 0.290 W / (mK) and a thermal efusivity of 632 Ws1 / 2 / m2 / K. In another configuration, the foamed PAS polymer material that forms the outer tube has between 50% and 63% density reduction, between 50% and 90% reduction in thermal conductivity with respect to the non-foamed density of the PAS polymer material, and between 50% and 88% reduction in thermal effusivity with respect to the corresponding values ​​of a non-foamed PAS polymer material. For example, foamed PPS polymer material has a density of 0.670 g / cc to 0.496 g / cc and a thermal conductivity of 0.145 W / (mK) to 0.029 W / (mK), while pre-foamed PPS polymer material has a density of 1.340 g / cc, a thermal conductivity of 0.290 W / (mK) and a thermal effusivity of 632 Ws1 / 2 / m2 / K. In one embodiment, the foamed PAS polymer material forming the outer tube has a density reduction of 50% or more compared to the density of non-foamed PAS polymer material. In another embodiment, the foamed PAS polymer material forming the outer tube has a density reduction of 63% or more. In another embodiment, the foamed PAS polymer material forming the outer tube has a density reduction of 68% or more. In another embodiment, the foamed PAS polymer material forming the outer tube has a density reduction of 86% or more. In another embodiment, the foamed PAS polymer material has a density reduction of 50% to 63%. In another embodiment, the foamed PAS polymer material has a density reduction of 63% to 68%. In yet another embodiment, the foamed PAS polymer material has a density reduction of 68% to 86%. In another modality, the foamed PAS polymeric material has a density reduction of 68% to 90%.In an additional modality, the foamed PAS polymeric material that forms the outer tube has a density reduction of 86% to 90%. In one embodiment, the foamed outer layer has a thermal conductivity reduction of 50% or more compared to the thermal conductivity of a non-foamed PAS polymer material. In one embodiment, the foamed outer layer has a thermal conductivity reduction of 63% or more compared to the thermal conductivity of a non-foamed PAS polymer material. In one embodiment, the foamed outer layer has a thermal conductivity reduction of 71% or more. In one embodiment, the foamed outer layer has a thermal conductivity reduction of 90% or more. In another embodiment, the foamed outer layer has a thermal conductivity reduction of 50% to 71%. In yet another embodiment, the foamed outer layer has a thermal conductivity reduction of 63% to 94%. In yet another embodiment, the foamed outer layer has a thermal conductivity reduction of 71% to 94%.In another version, the foamed outer layer has a reduction in thermal conductivity from 90% to 94%. In one embodiment, the foamed outer layer has a thermal effusivity reduction of 50% or more compared to the thermal effusivity of a non-foamed PAS polymer material. In one embodiment, the foamed outer layer has a thermal effusivity reduction of 63% or more compared to the thermal effusivity of a non-foamed PAS polymer material. In one embodiment, the foamed outer layer has a thermal effusivity reduction of 68% or more. In one embodiment, the foamed outer layer has a thermal effusivity reduction of 88% or more. In another embodiment, the foamed outer layer has a thermal effusivity reduction of 50% to 68%. In another embodiment, the foamed outer layer has a thermal effusivity reduction of 63% to 94%. In yet another embodiment, the foamed outer layer has a thermal effusivity reduction of 68% to 94%.In another zn / nLn / Lznz / E / Yii modality, the foamed outer layer has a reduction in thermal effusivity from 88% to 94%. Returning now to Figure 5, the foamed PAS polymer material forms the outer tube 24, a closed-cell foam with numerous closed cells 40, and a thin outer coating 42. The thin outer coating 42 defines a smooth, continuous outer surface of the main part 24a of the outer tube 24. In one embodiment, the foamed PAS polymer material does not have a thin outer coating. In another embodiment, the cell morphology of the foamed PAS polymer material is semi-closed, along with a thin outer coating. For example, the percentage of closed cells can be controlled by the type and concentration of the foaming agent. The closed-cell structure of the foamed PAS polymer material prevents water ingress, even if a shallow crack or fracture forms on the outer surface of the outer tube 24. Hundreds or thousands of closed-cell walls form between the outermost surface of the outer tube 24 and the inner tube 22 (shown in Figure 1 and Figure 2), thus preventing moisture from passing radially inward through the foamed PAS polymer material into the inner tube 22. Alternatively, fewer or more cell walls are formed based on the desired size of the outer tube 24 and / or the actual application. Preventing moisture from passing through the outer tube 24 can improve the service life of the inner tube22 compared to fiberglass-wrapped tube assemblies, where the inner metal tubes may be exposed to additional moisture, especially in the event of damage or improper handling / installation. In one embodiment, the cell morphology of foamed PAS polymer material is classified as macrocellular, characterized by an average cell diameter of 100 micrometers (µm) or greater. As discussed later, cell morphology can be controlled and adjusted by varying (1) the nature, type, and / or formulation of a foaming agent used to foam the unfoamed PAS polymer material; (2) the nature, type, and / or formulation of the PAS polymer material, with or without additives; and / or (3) the processing equipment, processing conditions, and / or related tooling. The cellular structure of foamed insulation can create and maintain maximum thermal performance that is unaffected or minimally affected by twisting, folding, and / or mechanical routing imposed during installation. In another modality, the cellular morphology of foamed PAS polymer material is classified as microcellular, characterized by an average cell diameter between 1 µm and 100 µm. In yet another modality, the cellular morphology of foamed PAS polymer material is classified as ultramicrocellular, characterized by an average cell diameter of 0.1 µm to 1 µm. zn / nLn / Lznz / E / Yii With regard to Figure 6, which schematically illustrates an extruder 50 configured to extrude PAS polymer material to form the outer tube 24 within the inner tube 22, the extruder 50 includes a central passage 52 and a radially external passage 54. The central passage is configured to allow the inner tube 22 to move axially through it. The radially external passage 54 is configured to direct PAS polymer material from a PAS polymer material reservoir (not shown) to the inner tube 22 to form the outer tube 24 within the inner tube 22. The 50 extruder can be a standalone single-screw extruder (SSE). In another configuration, at least two extruders are used. For example, the extruders can be connected in series, with the first extruder being an SSE and the second also an SSE. In another example, one extruder is a twin-screw extruder (TSE) and the second extruder is an SSE. Other suitable methods of extrusion and foaming of polymeric materials are described in Foam Extrusion: Principles and Practice, 2nd edition. Ed. ST Lee, CB Park. CRC Press, 2014. In addition, suitable extruder designs, extrusion configurations, and screw designs are described in Polymer Extrusion, 5th edition. C. Rauwendaal. Hanser Publications, 2014. In one embodiment, the PAS polymer material is foamed into the inner tube. In another embodiment, the PAS polymer material is foamed and then applied to the inner tube. In yet another embodiment, the outer tube is formed by coextrusion, tandem extrusion, injection molding, compression molding, calendering, rotational molding, and / or blow molding, and / or a combination of any of the aforementioned processes. For example, in a continuous process or in a batch process. A foaming agent is mixed with unfoamed PAS polymer material to foam the PAS polymer material. For example, unfoamed PAS polymer material is mixed with a chemical foaming agent present in an amount ranging from 1.0 percent by weight (wt.%) to 3 wt. In another embodiment, the foaming agent is present in an amount ranging from 0.1 wt. to 5 wt. In another embodiment, the foaming agent is present in an amount ranging from 2 wt. to 4 wt. In yet another embodiment, the foaming agent is mixed with unfoamed PAS polymer material and other additives, and the foaming agent is present in an amount ranging from 0.1 wt. to 5 wt. Experts in polymer foaming techniques will know and understand that adding more chemical foaming agent beyond a certain prescribed limit may not necessarily provide greater improvements in density reductions, thermal conductivity, or thermal effusivity, but could be detrimental with respect to the structure and mechanical properties of the foam. In another embodiment, foamed PAS polymer material is formed by mixing PAS polymer material with only a physical foaming agent. The mixing of the PAS polymer material and the physical foaming agent can occur inside the extruder barrel or outside the downstream extruder barrel, so that the physical foaming agent is injected into the polymer melt at high pressures, such as 35.15 kg / cm² (500 pounds per square inch, or psi). In one example, unfoamed PAS polymer material is mixed with a physical foaming agent present in an amount ranging from 0.1% to 0.5% by weight of the mixture. In another example, the physical foaming agent is present in an amount ranging from 0.01% to 1.5% by weight of the mixture. In another example, the physical foaming agent is present in an amount that varies between 0.05% by weight and 1.1% by weight of the mixture.In yet another example, the physical foaming agent is mixed with non-foamed PAS polymeric material and other additives, and the physical foaming agent is present in an amount ranging from 0.01% by weight to 1.5% by weight of the mixture. Experts in polymer foaming techniques will understand that adding more physical foaming agent beyond a certain prescribed limit may not provide further improvement in density reductions, thermal conductivity, or thermal effusivity, but could be detrimental with respect to the cellular structure and mechanical properties of the foam. In another embodiment, the foamed PAS polymer material is formed by mixing the PAS polymer material with a chemical foaming agent and a physical foaming agent using the methods described above. In other examples, a combination of a chemical foaming agent and a physical foaming agent is present in any of the quantities mentioned above. Polyarylene sulfide (PAS) refers to a general class of high-temperature resistant polymeric materials. Polyarylene sulfide may include repeating units of formula (I): —[(Ar1)n—X]m—[(Ar2) / —Y] / —[(Ar3)*—Z] / —[(AHjo—W]p(I) wherein Ar1, Ar2, Ar3, and Ar4 are the same or different and are arylene units of 6 to 18 carbon atoms; W, X, Y, and Z are the same or different and are divalent bonding groups selected from -SO2-, -S-, -SO-, -CO-, -O-, -COO-, or alkylene or alkylidene groups of 1 to 6 carbon atoms, and wherein at least one of the bonding groups is -S-, such that the bonding concentration —[Ar—S]— in structure (I) is equal to or greater than 50 mol%. The arylene units Ar1, Ar2, Ar3, and Ar4 may be selectively and independently substituted or unsubstituted. Advantageous arylene systems are phenylene, biphenylene, naphthylene, anthracene, and phenanthrene, to name a few. zn / nLn / Lznz / B / Yi Within the PAS family of polymeric materials, poly(phenylene sulfide) (PPS) polymer is the most preferable. The PAS polymeric material of any of the above forms may include, or may be, any of the PPS polymeric materials described below. The polymeric material PPS can have the following general structure (II), zn / nLn / Lznz / E / Yii where R1 and R2 are substituents on the phenyl group, such that R1 and R2 can independently be hydrogen, halogen, alkyl group, alkoxy group, haloalkyl group, cycloalkyl group, heterocycloalkyl group, cycloalkyloxy group, aryl group, aralkyl group, aryloxy group, aralkyloxy group, heteroaryl group, heteroaralkyl group, alkenyl group, alkynyl group, amino group, amide group, alkylenamine group, arylenamine group or alkenyleneamine group, nitro, cyano, carboxylic acid or a salt thereof, phosphonic acid or a salt thereof, or sulfonic acid or a salt thereof. The values ​​of b and c can be 0 (meaning no substitution) or more. Furthermore, each repeating unit in formula (II) can have a different or the same bonding position of the sulfur atom to the phenyl ring. Additionally, each unit can have a different substitution pattern on the phenyl groups, for example, a combination of unsubstituted units (b = 0) and substituted units (b > 0). In a further preferred embodiment, the PPS polymeric material has the constitutional repeating unit (III) shown below, so that R1 and R2 are both hydrogen according to the general structure (II). The non-foamed PPS polymer material according to structure (II) or (III) is included as part of a PPS resin, and 90 mol% or more of the PPS resin is the above constitutional repeating unit. For example, approximately 10 mol% or less of the above constitutional repeating unit in the PPS resin is replaced by an additional constitutional repeating unit having any of the following structures (IV) or a combination thereof. m-phenylene sulfide o-phenylene sulfide phenylene sulfide sulfone αν zn / nLn / Lznz / E / Yii phenylene sulfide ketone phenylene sulfide ether diphenylene sulfide Although not indicated in the chemical structures above, each phenyl group in the units above may have R1 and R2 substitutions according to structure (II). The R1 and R2 substituents of the phenyl groups in the structures above are hydrogen. In one embodiment, 70 mol% or more of the PPS resin comprises repeating units with structure (II) or (III). For example, approximately 30 mol% or less of the constitutional repeating unit in the PPS resin is replaced by an additional constitutional repeating unit having any of the structures represented by (IV) or a combination thereof. In another embodiment, 50 mol% or more of the PPS resin comprises repeating units with structure (II) or (III). For example, approximately 50 mol% or less of the constitutional repeating unit in the PPS resin is replaced by an additional constitutional repeating unit having any of the structures represented by (IV) or a combination thereof. In another embodiment, 30 mol% or more of the PPS resin comprises repeating units with structure (II) or (III). For example, approximately 70 mol% or less of the constitutional repeating unit in the PPS resin is replaced by an additional constitutional repeating unit having any of the structures represented by (IV) or a combination thereof. PPS polymer material can be synthesized using different methods so that the polymer chains are linear, semilinear, branched, crosslinked, or a combination thereof. In one embodiment of the foamed PPS tubular assembly, the PPS polymer chains are linear. In another embodiment, the polymer chains are semilinear. In yet another embodiment, the polymer chains are branched. In another embodiment, the polymer chains are crosslinked. In yet another embodiment, the PPS resin comprises a combination of linear, semilinear, branched, and / or crosslinked polymer chains. For example, the combination can be produced during monomer synthesis reactions, polymerization reactions, or post-polymerization operations, including, but not limited to, melt blending and solution blending. PPS polymer material can exhibit certain general physical and chemical characteristics, which are described below. Some examples of commercially available PPS resins that can be used in one modality include: PPS RYTON® from SOLVAY®, PPS FORTRON® from CELANESE®, TORELINA® from TORAY®, and DIC.PPS® from DIC®. PPS polymer is a high-performance, semi-crystalline polymer that offers an excellent combination of thermal, mechanical, and chemical resistance properties. Therefore, applications requiring high-temperature stability, toughness, and chemical resistance at elevated temperatures are good candidates for PPS polymer. PPS polymer material performs well in challenging environments. It provides high hardness, stiffness, and dimensional stability, excellent thermal resistance, inherent flame retardancy, and low creep and moisture absorption, among many other benefits. In one modality, the PPS polymeric material has excellent resistance to the media. The polymeric material PPS can be used in high-temperature environments due to its exceptional thermal properties. For example, as shown in Table 1 below, PPS has a maximum continuous service temperature of approximately 220 to 230°C, which is higher than the commonly used foamed polymeric materials also listed in the table. In one configuration, the service temperature of PPS is up to 240°C. ζη / ηίη / ίζηζ / Β / γι Table 1. Polymeric materials with their maximum continuous service temperatures. zn / nLn / Lznz / E / Yi Materiales poliméricos con sus temperaturas máximas de servicio continuo Polímero T£C1 PPS Poli(sulfuro de fenileno) 220-230 Materiales poliméricos comúnmente espumados Silicona 200-210 PPSU Poli(fenilen sulfona) 190 PESU / PSU Pol ¡(su lfona) / pol ¡(éter sulfona) 150 - 180 PEI Poli(éter imida) 170 Nylon 4,6 150-160 Nylon 6,6 / 6,10 140-150 PET Tereftalato de polietileno 130-140 PVDF Poli(fluoruro de vinilideno) 140 PC Policarbonato 125-135 PP Polipropileno 110 - 120 PLA ​​Acido polylático 110 PPO / PPE Oxido / éterde poliphenyleno 100 - 110 HDPE Polyethylene of high densidas 90-100 ABS Acrylonitrilo butadiene estireno 90 PS Poliestireno 80-90 TPU Poliuretano termoplástico 70-90 LDPE Polyethylene of low densidas 75-85 EVA Poli(etil vinyl acetot) 70 PVC Polyvinyl Chloride 60-70 PPS polymer material has excellent dimensional stability and very low, predictable shrinkage at high soldering temperatures. Warping or deformation is minimized in an optimally molded part. Withstanding these higher temperatures makes lead-free soldering possible. PPS polymer material has high purity with very low levels of ionic impurities. In one form, PPS polymer material has good electrical insulation properties and a low dissipation factor. PPS polymer is an excellent dielectric material with a low dielectric constant. In one configuration, PPS polymer has high breakdown voltage resistance and also exhibits superior capacitance stability with temperature. The polymeric material PPS has excellent resistance to thermal oxidation, allowing parts made from it to withstand high thermal stress. In one application, PPS polymeric material can withstand service temperatures of up to 240°C for several years. PPS polymer material is non-hygroscopic. In one instance, PPS polymer material absorbs only 0.02% of water after immersion in water at 23°C for 24 hours (ASTM D-570 method). This is significantly less than what occurs with many other polymer materials. Furthermore, unlike other polymer materials (e.g., polyamides), PPS polymer material does not expand when exposed to water and releases absorbed moisture when stored in dry air. Additionally, the absorbed atmospheric moisture does not cause molecular degradation. The PPS polymer material has excellent resistance to hydrolysis. In one instance, the PPS polymer material undergoes little or no change in tensile strength and elongation when exposed to water at 95°C for more than 1,000 hours at 1.05 kg / cm² (15 psi). PPS polymer material has excellent chemical resistance. In one form, PPS polymer material does not dissolve in any known organic solvent below 200°C and is virtually unaffected by acids, bases, alcohols, oxidizing bleaches, and many other chemicals at elevated temperatures for extended periods. The PPS polymer material has excellent resistance to all liquid and gaseous fuels, including methanol and ethanol, and withstands hot engine oils, greases, antifreeze, and other automotive fluids. In one instance, the PPS polymer material is useful in fuel applications due to its stability during prolonged contact with gasoline formulations that have varying levels of octane, sulfur, oxygen, and contaminants. zn / nLn / Lznz / E / Yii The polymeric material PPS has good resistance to ultraviolet radiation. In one modality, the PPS polymer shows little change in tensile strength, notch impact strength, and other mechanical properties after 2,000 hours of exposure to ultraviolet radiation. Polypropylene (PPS) is relatively impermeable to gases, fuels, and other liquids compared to other materials. Permeability is lower with unfilled grades of PPS. The combination of low permeability and high chemical resistance makes PPS excellent for automotive, industrial, chemical, petroleum, and aerospace applications, as well as medical and packaging uses where a high gas barrier is required. The PPS polymer material that forms the outer tube 24 is flame-resistant. In one configuration, the PPS resin has a flammability rating of V0, V1, or V2 according to Underwriters Laboratories UL94 and UL94HB standards. Therefore, no additional flame retardants are required to pass UL-type flammability tests. In another embodiment, PPS resin is not flame retardant. PPS resin foamed with chemical or physical foaming agents may or may not retain flame retardancy, or its flame retardancy potential may increase or decrease. In one embodiment, foamed PPS resin has a flammability rating of V0, V1, or V2. In another embodiment, foamed PPS resin is not flame retardant. In one embodiment, the PAS resin of formula (I) is composed of a homopolymer. In another embodiment, the PAS resin is composed of a copolymer such that the arylene sulfide constitutional units of formula (II) in the PAS resin of formula (I) are equal to or greater than 90 mol%. In another embodiment, the PAS resin is composed of a copolymer such that the arylene sulfide constitutional units of formula (II) in the PAS resin of formula (I) are equal to or greater than 70 mol%. In yet another embodiment, the PAS resin is composed of a copolymer such that the arylene sulfide constitutional units of formula (II) in the PAS resin of formula (I) are equal to or greater than 50 mol%. In another embodiment, the PAS resin is composed of a copolymer such that the constitutional units of arylene sulfide of formula (II) in the PAS resin of formula (I) are equal to or greater than 30% by moles. In one form, PAS resin is composed of a mixture, an alloy, a composite material, or a combination thereof. For example, one embodiment of PAS resin comprises an additive that includes, but is not limited to, plasticizers, compatibilizers, antioxidants, UV stabilizers, radiopaque compounds, colorants (pigments or dyes), flow modifiers, impact modifiers, elastomers (such as in thermoplastic elastomers), crosslinked rubber (such as in thermoplastic vulcanizes), lubricants, Zn / nLn / Lznz / E / Yii release agents, coupling agents, crosslinking agents, dispersing agents, foaming agents, foam nucleating agents, flame retardants, reinforcing metals, minerals, nucleating agents, and / or fillers (such as talc, clay, mica, graphite, carbon black, carbon nanotubes, graphene, silica, POSS, powdered metals, powdered ceramics, metal- or ceramic-based nanowires, glass fibers, etc.).Another form of PAS resin includes a combination of any of the above additives. In another configuration, a polyarylene sulfide (PAS) composition and / or formulation forms the inner tube. For example, any of the PAS polymeric materials discussed above can form the inner tube. In one embodiment, the foaming agent used to foam the PAS polymeric material is a chemical foaming agent. Examples of chemical foaming agents include, but are not limited to, citric acid / sodium bicarbonate, ADCA (azodicarbonate), OBSH (p,p'-Oxybis(benzene)sulfonyl), TSH (p-toluenesulfonyl hydrazide), TSS (p-toluenesulfonyl semicarbazide), DNPT (dinitrosopentamethylenetetramine), 5PT (5-phenyltetrazol), SBH (sodium borohydride), magnesium carbonate (MgCO3), calcium carbonate (CaCO3), zinc carbonate (ZnCO3), and a combination of CaMCO3 and ZnCO3, tartaric acid, azodicarbonamide, a hydrazine derivative, a semicarbazide derivative, a tetrazole derivative, a benzoxazine derivative, a metal oxide derivative, or a metal carbonate derivative. Alternatively, the foaming agent may include a combination of any of the above chemical foaming agents. In one embodiment, the foaming agent used to foam the PPS polymeric material is a physical foaming agent. Examples of physical foaming agents include, but are not limited to, Propane (C3Hs), n-Butane (C4H10), i-Butane (CH3(CH3)CHCH3), n-Pentane (C5H12), i-Pentane (CH3(CH3)CHCH2CH3), HCFC-22 (CHF2CI), HCFC-142b (CHF2CICH3), HFC-152a (CHF2CH3), HCFC-123 (CHCI2CF3), HCFC-123a (CHFCICF2CI), HCFC-124 (CHFCICF3), HFC-134a (CH2FCF3), HFC-143a (CH3CF3), CFC-11 (CFCI3), CFC-12 (CF2CI2), CFC-113 (CFCI2CF2CI), CFC-114 (CF2CLCF2CI), MeCI (CH3CI), MeCl2(CH2Cl2), carbon dioxide (CO2), nitrogen (N2), oxygen (O2), supercritical CO2, air, helium, argon, aliphatic hydrocarbons (e.g., butanes, pentanes, hexanes, and heptanes), chlorinated hydrocarbons (e.g., dichloromethane and trichloroethylene), and hydrochlorofluorocarbons (e.g., dichlorotrifluoroethane). In another embodiment, the foaming agent includes a combination of any of the above physical foaming agents.In yet another form, the foaming agent includes a combination of any of the above chemical foaming agents and any of the above physical foaming agents. Table 2 below provides examples of different polymeric materials and processing conditions that can be used to manufacture PAS foams (e.g., zn / nLn / Lznz / E / Yii to result in a foamed PPS polymeric material), as well as some final physical properties of those foams. Table 2. Examples showing polymeric materials, processing conditions and physical properties of different PAS foams. Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Polymer Type PPS 1 PPS 1 PPS 1 PPS 1 PPS 2 PPS 2 Foaming Agent Type CFA CFA PFA CFA CFA PFA Foaming Agent Class Tetrazoles Metal Oxides / Metal Carbonates Nitrogen Metal Oxides / Metal Carbonates Tetrazoles Tetrazoles Extrusion Conditions SP Zone 1 (°C) 240 200 271 282 280 282 SP Zone 2 (°C) 300 250 293 304 300 293 SP Zone 3 (°C) 300 300 304 316 300 304 SP Zone 4 (°C) 280 280 316 327 280 327 SP Zone 5 (°C) - - 316 327 - 316 SP Zone 6 (°C) - - 316 327 - 316 SP Zone 7 (°C) - - 163 327 - 316 SP Zone 8 (°C) - - 281 327 - 316 SP Zone 9 (°C) - - 264 327 - 316 Properties Cell Morphology Closed Closed Closed Closed Closed Closed Average Cell Size (mm) 80 220 50 170 175 200 Density (g / cc) 0.35 0.18 0.37 0.25 0.43 0.48 Density Reduction (%) 74 87 72 81 68 64 Thermal Conductivity (W / m / K) 0.030 0.024 0.030 0.029 0.055 0.066 Reduction of thermal conductivity (%) 90 92 90 90 81 77 Effusivity (Ws1 / 2 / m2 / K) 103.8 66.6 106.8 86.3 155.8 180.4 Reduction of effusivity (%) 84 89 83 86 75 71 Flame retardation (UL94 Vertical Classification) V-0 V-0 V-0 V-0 V-0 V-0. Figure 7 shows an exemplary embodiment of the steam tube assembly 120. The steam tube assembly 120 is substantially the same as the steam tube assembly 20 mentioned above, and consequently, the same reference numbers, indexed by 100, are used to indicate corresponding structures to similar structures in the steam tube assemblies. Furthermore, the description above of the steam tube assembly 20 is equally applicable to the steam tube assembly 120, except as noted below. It is also understood that aspects of the steam tube assemblies may be interchangeable or used in conjunction with others where applicable. The steam tube assembly 120 includes an inner tube 122, an outer tube 124, and an intermediate layer 160 that separates the inner tube 122 from the outer tube 124. For example, the intermediate layer 160 surrounds the inner tube 122. In one embodiment, the intermediate layer is a braid or spiral winding comprising metallic wire and / or polymer fiber. In another embodiment, the intermediate layer is a tape, film, filament, or wrapped strip comprising fiberglass and / or woven glass. In another embodiment, the intermediate layer is a combination of some or all of the above. In yet another embodiment, the intermediate layer is multi-layered. Figure 8 shows an exemplary embodiment of steam tube assembly 182. Steam tube assembly 182 is substantially the same as steam tube assembly 120 mentioned above, and consequently, the same reference numbers are used to indicate corresponding structures for similar structures in steam tube assemblies. Furthermore, the description above of steam tube assembly 120 is equally applicable to steam tube assembly 182, except as noted below. It is also understood that aspects of steam tube assemblies may be interchangeable or used in conjunction with others where applicable. Steam tube assembly 182 includes an inner tube 122, an outer tube 124, and an intermediate layer 160 that separates the inner tube 122 from the outer tube 124. Steam tube assembly 182 also includes an outer intermediate layer 184 and an outer layer 186. The outer intermediate layer 184 may enclose the outer tube 124 and separate the outer layer 186 from the outer tube 124. The outer intermediate layer 184 may comprise the same material as the inner tube 122, the intermediate layer 160, or the outer tube 124. In one embodiment, the outer intermediate layer comprises a different material than the inner tube, the intermediate layer, and / or the outer tube. The outer layer 186 may enclose the outer intermediate layer 184. The outer layer 186 may comprise the same material as the inner tube 122, the intermediate layer 160, the outer tube 124, or the outer intermediate layer 184. In one embodiment, the outer layer comprises a different material than the inner tube, the intermediate layer, the outer tube, and / or the outer intermediate layer. Figure 9 shows an exemplary embodiment of steam tube assembly 220. Steam tube assembly 220 is substantially the same as the previously mentioned zn / nLn / Lznz / E / Yi steam tube assemblies 20 and 120, and consequently, the same reference numbers, indexed by 200, are used to indicate corresponding structures to similar structures in the steam tube assemblies. Furthermore, the above description of steam tube assemblies 20 and 120 is equally applicable to steam tube assembly 220, except as noted below. It is also understood that aspects of the steam tube assemblies may be substituted for one another or used in conjunction with others where applicable. The steam tube assembly 220 includes four inner tubes 222, one outer tube 224, and an intermediate layer 260 that separates the inner tubes 222 from the outer tube 224. For example, the inner tubes 222 are grouped together, and the intermediate layer 260 surrounds all the inner tubes 222, and the outer tube 224 surrounds the intermediate layer 260 along with the inner tubes 222. In one embodiment, the outer tube is a single, continuous body of PAS polymer material, such that the PAS polymer material insulates the inner tubes. In another embodiment, the steam tube assembly includes more than four inner tubes. In yet another embodiment, the steam tube assembly includes two or three inner tubes. Figure 10 shows an exemplary embodiment of the 320 steam tube assembly. The 320 steam tube assembly is substantially the same as the 20, 120, and 220 steam tube assemblies mentioned above, and consequently, the same reference numbers, indexed by 300, are used to indicate corresponding structures to similar structures in the steam tube assemblies. Furthermore, the above description of the 20, 120, and 220 steam tube assemblies is equally applicable to the 320 steam tube assembly, except as noted below. It is also understood that aspects of the steam tube assemblies may be substituted for one another or used in conjunction with others where applicable. The steam tube assembly 320 includes four inner tubes 322, one outer tube 324, one intermediate layer 360, and four intermediate outer tubes 370 that encircle each corresponding inner tube 322. For example, the intermediate outer tubes 370 are grouped together, and the intermediate layer 360 encircles all the intermediate outer tubes 370, and the outer tube 324 encircles the intermediate layer 360 along with the intermediate outer tubes 370 and the inner tubes 322. The first intermediate outer tubes 370 may each be made of the same PAS polymeric material as the outer tube 324 and in the same manner. In one embodiment, the first intermediate outer tubes are made of any other PAS polymeric material used to manufacture any of the outer layers described above. In another embodiment, the intermediate outer tube is a single continuous body of PAS polymeric material such that the PAS polymeric material insulates the inner tubes. In yet another embodiment, the zn / nLn / Lznz / E / Yii steam tube assembly includes more than four intermediate outer tubes and corresponding inner tubes. In another embodiment, the steam tube assembly includes two or three intermediate outer tubes and corresponding inner tubes. In one embodiment, the intermediate outer tubes are not connected to the inner tubes. In another embodiment, each intermediate outer tube is continuously connected to its corresponding inner tube. In yet another embodiment, each intermediate outer tube is connected randomly or sequentially to its corresponding inner tube. In another embodiment, the steam tube assembly does not include the intermediate layer. Figure 11 shows an exemplary embodiment of steam tube assembly 420. Steam tube assembly 420 is substantially the same as steam tube assemblies 20, 120, 220, and 320 mentioned above, and consequently, the same reference numbers, indexed by 400, are used to indicate corresponding structures to similar structures in steam tube assemblies. Furthermore, the above description of steam tube assemblies 20, 120, 220, and 320 is equally applicable to steam tube assembly 420, except as noted below. It is also understood that aspects of steam tube assemblies may be substituted for one another or used in conjunction with others where applicable. The steam tube assembly 420 includes an inner tube 422, an outer tube 424, an intermediate layer 460, and a heating element 480. For example, the heating element extends the length of the inner tube 422 and is positioned between the inner tube 422 and the intermediate layer 460. In one embodiment, the heating element consists of two metal wires coated with a polymer. In another embodiment, the heating element comprises multiple heating elements covering the inner tube (for example, in a coiled or braided configuration, or extending parallel to the length of the inner tube). Each tube discussed above with reference to Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, and Figure 11 is illustrated with a circular cross-section. In other embodiments, some of the tubes or each tube has a different cross-sectional shape. For example, in some embodiments, the cross-sectional shape of the inner and outer tubes, along with any intermediate layers, is rectangular (e.g., square). In other embodiments, the cross-sectional shape of the inner and outer tubes, along with any intermediate layers, is another shape (e.g., a non-standard shape that may be dictated by the tooling used to make different layers of the tube assembly, the cross-section of the previous layer, and / or the processing / manufacturing conditions). According to one aspect, a tubular assembly includes a first tubular member having an outer surface and an inner surface, wherein the inner surface defines a zn / nLn / Lznz / E / Yii innermost surface of the assembly, and a second tubular member surrounding the outer surface of the first member, wherein the second member comprises a foamed polyarylene sulfide polymeric material having a foamed density and a foamed thermal effusivity that is foamed from an unfoamed polyarylene sulfide polymeric material having an unfoamed density and an unfoamed thermal effusivity, the foamed density being less than approximately 50% of the unfoamed density, and the foamed thermal effusivity being less than approximately 50% of the unfoamed thermal effusivity. Polyarylene sulfide polymeric material can be selected from the group consisting of polyarylene sulfide homopolymers, copolymers, mixtures, alloys, and combinations thereof. Polyarylene sulfide polymeric material can be selected from the group consisting of homopolymers, copolymers, mixtures, alloys and combinations thereof of polyphenylene sulfide. Foamed polyarylene sulfide polymer material can be formed by a process comprising the following steps: forming a mixture of the non-foamed polyarylene sulfide polymeric material and a foaming agent, wherein the foaming agent is between approximately 0.1 and 5% by total weight of the foaming agent and the polyarylene sulfide polymeric material. The foaming agent may comprise approximately 1-3% by total weight of the foaming agent and the polyarylene sulfide polymeric material. The foaming agent may comprise approximately 2-4% by total weight of the foaming agent and the polyarylene sulfide polymeric material. Foamed polyarylene sulfide polymer material can be formed by a process comprising the following steps: introducing a foaming agent directly into an extruder and dispersing the foaming agent into the unfoamed polyarylene sulfide polymer material, wherein the foaming agent is between approximately 0.01 and 1.5% by total weight of the foaming agent and the polyarylene sulfide polymer material. The foaming agent may comprise approximately 0.05-1.1% by total weight of the foaming agent and the polyarylene sulfide polymeric material. The foaming agent may comprise approximately 0.1-0.5% by total weight of the foaming agent and the polyarylene sulfide polymeric material. Foamed density can be approximately 60-90% lower than non-foamed density. Foamed density can be approximately 68-90% lower than non-foamed density. zn / nLn / Lznz / E / Yii Foamed density can be approximately 86-90% lower than non-foamed density. Foamed polyarylene sulfide polymer material can have a foamed thermal conductivity and unfoamed polyarylene sulfide polymer material has an unfoamed thermal conductivity, the foamed thermal conductivity being at least approximately 50% lower than the unfoamed thermal conductivity. Foamed thermal conductivity can be approximately 50-94% lower than non-foamed thermal conductivity. Foamed thermal conductivity can be approximately 71-94% lower than non-foamed thermal conductivity. Foamed thermal conductivity can be approximately 90-94% lower than non-foamed thermal conductivity. Foamed polyarylene sulfide polymer material can have a foamed thermal conductivity of approximately 0.017-0.145 W / (mK). Foamed polyarylene sulfide polymer material can have a foamed thermal conductivity of approximately 0.017-0.084 W / (mK). Foamed polyarylene sulfide polymer material can have a foamed thermal conductivity of approximately 0.017-0.029 W / (mK). The foam density may be less than approximately 0.67 g / cc. The foam density can be between approximately 0.134-0.429 g / cc. The thermal effusiveness of foamed material can be less than approximately 316 Ws1 / 2 / m2 / K. Foamed polyarylene sulfide polymer material can be a closed-cell foam. Foamed polyarylene sulfide polymer material can be a semi-closed cell foam. Foamed polyarylene sulfide polymeric material can have an average cell diameter of at least approximately 0.1 pm. Foamed polyarylene sulfide polymeric material can have an average cell diameter of at least approximately 100 pm. At least approximately 70 mol% of the polyarylene sulfide polymeric material may have a repeating unit of the following structural formula: zn / nLn / Lznz / E / Yii At least approximately 70 mol% of the polyarylene sulfide polymeric material may have a repeating unit of one of the following structural formulas: where R1 and R2 are substituents on a phenyl group, and the values ​​of b and c can be 0 (meaning no substitution) or more. 30 mol% or less of the polyarylene sulfide polymeric material may have a repeating unit selected from the group consisting of one or more of the following: m-phenylene sulfide o-phenylene sulfide phenylene sulfide sulfone phenylene sulfide ketone phenylene sulfide ether diphenylene sulfide Foamed polyarylene sulfide polymer material may have a flammability index of V0, V1 or V2. Foamed polyarylene sulfide polymer material may not be flame retardant. The first member may comprise a first layer of the set and the second member may comprise a second layer of the set adjacent to the first layer. The first member may comprise a metallic material. One or both of the first member or the second member can be movable in a sliding manner with respect to the other of the first member or the second member. The second member can define a more outer surface of the tubular assembly. The tubular assembly may further comprise one or more intermediate tubular members arranged between the first member and the second member. The tubular assembly may further comprise one or more third tubular members, each of the third members being the same as or different from the first member and being the same as or different from each of the other third members, the second member may surround the first member and each of the third tubular members. The tubular assembly may further comprise a first intermediate layer that surrounds the first member and each of one or more third members, and is arranged between the second member and the first member and each of the third members. The tubular assembly may further comprise a fourth individual member surrounding a corresponding member of the first member and each of the third members; the fourth member may comprise a foamed polyarylene sulfide polymer material having a foamed density that is foamed from an unfoamed polyarylene sulfide polymer material having an unfoamed density; the foamed density of the foamed polyarylene sulfide polymer material of the fourth member may be less than approximately 50% of the unfoamed density of the unfoamed polyarylene sulfide polymer material of the fourth member; and the foamed polyarylene polymer material of the fourth member may be the same as or different from the foamed polyarylene polymer material of the second member. The tubular assembly may further comprise one or more third tubular members, each of the third members being the same as or different from the first member and the same as or different from each of the other third members, and at least two fourth tubular members, each fourth member being able to surround a corresponding member of the first and third members, each fifth member being able to comprise a foamed polyarylene sulfide polymer material having a foamed density that is foamed from an unfoamed polyarylene sulfide polymer material having an unfoamed density, the foamed density of the foamed polyarylene sulfide polymer material of the fourth member being less than approximately 50% of the unfoamed density of the unfoamed polyarylene sulfide polymer material of the fourth member,The foamed polyarylene polymer material of the fourth member may be the same as or different from the foamed polyarylene polymer material of the second member. Each fourth member can extend continuously axially along and continuously circumferentially around the corresponding first member and third member, so that the fourth members radially isolate the first and third members from an environment and from each other. The tubular assembly may further comprise a heating element arranged between the first member and the second member, and extending along a length of the first member. The tubular assembly may also include a fifth tubular member that surrounds the second member. A method for manufacturing the tubular assembly may comprise the following step: (a) foaming the unfoamed polyarylene polymeric material around the outer surface of the first member to form the second member. The non-foamed polyarylene sulfide polymer material can be foamed in step (a) onto the outer surface of the first member. The manufacturing method may further comprise the additional step prior to step (a) of extruding the non-foamed polyarylene sulfide polymeric material onto the outer surface of the first member. One method of using the tubular assembly may comprise the passage of fluid flowing within the first member, axially along the inner surface of the first member. Steam can flow inside the first member, axially along the inner surface of the first member. According to another aspect, a tubular assembly includes a first tubular member having an outer surface and an inner surface, wherein the inner surface defines a more interior surface of the assembly, and a second tubular member surrounding the outer surface of the first member, wherein the second member comprises a foamed polyarylene sulfide polymeric material having a foamed thermal conductivity that is foamed from a non-foamed polyarylene sulfide polymeric material having a non-foamed thermal conductivity, the foamed thermal conductivity being at least approximately 50% lower than the non-foamed thermal conductivity. Foamed polyarylene sulfide polymer material can have a foamed thermal conductivity of approximately 0.017-0.145 W / (mK). Polyarylene sulfide polymeric material can be selected from the group consisting of homopolymers, copolymers, mixtures, alloys and combinations thereof of polyphenylene sulfide. Any of the above characteristics can be combined with any of the above aspects. For example, any of the above aspects can include density reductions, thermal effusiveness reductions, and / or thermal conductivity reductions in combination with or without one or two of the other density reductions, thermal effusiveness reductions, and thermal conductivity reductions. Furthermore, any of the above aspects can include the above densities, thermal conductivities, and / or thermal effusivenesses, with or without the above density reductions, thermal conductivity reductions, and / or thermal effusiveness reductions, in combination with any or two of the other densities, thermal conductivities, and thermal effusivenesses, with or without the above density reductions, thermal conductivity reductions, and / or thermal effusiveness reductions.Furthermore, any of the above aspects may include any of the above polyphenylene sulfide polymeric materials, and such polyphenylene sulfide polymeric materials may be foamed with any of the above foaming agents or combinations of foaming agents. Although the invention has been shown and described with respect to a particular embodiment or embodiments, it is obvious that other people skilled in the art will come up with equivalent alterations and modifications after reading and understanding this specification and the accompanying drawings. In particular, with respect to the various functions performed by the elements described above (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe these elements are intended to correspond, unless otherwise indicated, to any element that performs the specified function of the described element (i.e., is functionally equivalent), even if it is not structurally equivalent to the described structure that performs the function in the exemplary embodiment or embodiments of the invention illustrated herein.Furthermore, although a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more features of the other embodiments, as desired and advantageous for any given or particular application. zn / nLn / Lznz / E / Yii NOVELTY OF THE INVENTION Having described the present invention as above, the following is considered novel and, therefore, is claimed as property:

Claims

1. A tubular assembly, characterized in that it comprises: a first tubular member having an outer surface and an inner surface, wherein the inner surface defines a more interior surface of the assembly; and a second tubular member surrounding the outer surface of the first member, wherein the second member comprises a foamed polyphenylene sulfide polymeric material having a foamed density and a foamed thermal effusivity that is foamed from a mixture of a non-foamed polyphenylene sulfide polymeric material having polymer chains that are branched or crosslinked and a foaming agent, the polyphenylene sulfide having a non-foamed density and a non-foamed thermal effusivity, wherein the foamed polyphenylene sulfide polymeric material has an average cell diameter of at least 100 pm, wherein the foamed density is less than approximately 50% of the non-foamed density;and where the foamed thermal effusivity is less than approximately 50% of the non-foamed thermal effusivity.

2. The tubular assembly according to claim 1, characterized in that the polyphenylene sulfide polymeric material is selected from the group consisting of polyphenylene sulfide homopolymers, copolymers, mixtures, alloys and combinations thereof.

3. The tubular assembly according to any of the preceding claims, characterized in that the foamed polyphenylene sulfide polymer material is formed by a process comprising the step of: forming a mixture of the non-foamed polyphenylene sulfide polymer material and the foaming agent, wherein the foaming agent is between approximately 0.1 and 5% by total weight of the foaming agent and the polyphenylene sulfide polymer material.

4. The tubular assembly according to claim 3, characterized in that the foaming agent comprises approximately 1-3% by total weight of the foaming agent and the polyphenylene sulfide polymeric material.

5. The tubular assembly according to any of the preceding claims, characterized in that the foaming agent is a chemical foaming agent comprising tetrazole, metal carbonate, or metal oxide. zn / nLn / Lznz / E / Yii 6. The tubular assembly according to any of claim 1 or 2, characterized in that the foamed polyphenylene sulfide polymer material is formed by a process comprising the step of: introducing the foaming agent directly into an extruder and dispersing or dissolving the foaming agent in the unfoamed polyphenylene sulfide polymer material, wherein the foaming agent is between approximately 0.01 and 1.5% by total weight of the foaming agent and the polyphenylene sulfide polymer material.

7. The tubular assembly according to claim 6, characterized in that the foaming agent comprises approximately 0.05-1.1% by total weight of the foaming agent and the polyphenylene sulfide polymeric material.

8. The tubular assembly according to claim 7, characterized in that the foaming agent comprises approximately 0.1-0.5% by total weight of the foaming agent and the polyarylene sulfide polymeric material.

9. The tubular assembly according to any of the preceding claims, characterized in that the foamed density is approximately 60-90% less than the non-foamed density.

10. The tubular assembly according to claim 9, characterized in that the foamed density is approximately 68-90% less than the non-foamed density.

11. The tubular assembly according to claim 10, characterized in that the foamed density is approximately 86-90% less than the non-foamed density.

12. The tubular assembly according to any of the preceding claims, characterized in that the foamed polyphenylene sulfide polymer material has a foamed thermal conductivity and the non-foamed polyphenylene sulfide polymer material has a non-foamed thermal conductivity, the foamed thermal conductivity being at least approximately 50% lower than the non-foamed thermal conductivity.

13. The tubular assembly according to claim 12, characterized in that the foamed thermal conductivity is approximately 50-94% lower than the non-foamed thermal conductivity.

14. The tubular assembly according to claim 13, characterized in that the foamed thermal conductivity is approximately 71-94% lower than the non-foamed thermal conductivity.

15. The tubular assembly according to claim 14, characterized in that the foamed thermal conductivity is approximately 90-94% lower than the non-foamed thermal conductivity. zn / nLn / Lznz / E / Yi 16. The tubular assembly according to any of the preceding claims, characterized in that the foamed polyphenylene sulfide polymeric material has a foamed thermal conductivity of approximately 0.017-0.145 W / (mK).

17. The tubular assembly according to any of the preceding claims, characterized in that the foamed polyphenylene sulfide polymeric material has a foamed thermal conductivity of approximately 0.017-0.084 W / (mK).

18. The tubular assembly according to any of the preceding claims, characterized in that the foamed polyphenylene sulfide polymeric material has a foamed thermal conductivity of approximately 0.017-0.029 W / (mK).

19. The tubular assembly in accordance with any of the preceding claims, characterized in that the foamed density is less than approximately 0.67 g / cc.

20. The tubular assembly according to claim 19, characterized in that the foamed density is between approximately 0.134-0.429 g / cc.

21. The tubular assembly in accordance with any of the preceding claims, characterized in that the foamed thermal effusivity is less than approximately 316 Ws1 / 2 / m2 / K.

22. The tubular assembly in accordance with any of the preceding claims, characterized in that the foamed thermal effusivity is between approximately 38202 Ws1 / 2 / m2 / K.

23. The tubular assembly according to any of the preceding claims, characterized in that the foamed polyphenylene sulfide polymeric material is a closed-cell foam.

24. The tubular assembly according to claims 1-22 above, characterized in that the foamed polyphenylene sulfide polymeric material is a semi-closed cell foam.

25. The tubular assembly according to any of the preceding claims, characterized in that at least approximately 70 mol% of the polyphenylene sulfide polymeric material has a repeating unit of the following structural formula: zn / nLn / Lznz / E / Yii 26. The tubular assembly according to any of the preceding claims, characterized in that at least approximately 70 mol% of the polyphenylene sulfide polymeric material has a repeating unit of one of the following structural formulas: wherein R1 and R2 are independently hydrogen, halogen, alkyl group, alkoxy group, haloalkyl group, cycloalkyl group, heterocycloalkyl group, cycloalkyloxy group, aryl group, aralkyl group, aryloxy group, aralkyloxy group, heteroaryl group, heteroaralkyl group, alkenyl group, alkynyl group, amino group, amide group, alkylenamine group, arylenamine group or alkenyleneamine group, nitro, cyano, carboxylic acid or a salt thereof, phosphonic acid or a salt thereof, or sulfonic acid or a salt thereof, and wherein the values ​​of b and c may be 0 (i.e., no substitution) or more.

27. The tubular assembly according to any of the preceding claims, characterized in that 30 mol% or less of the polyphenylene sulfide polymeric material has a repeating unit selected from the group consisting of one or more of the following: m-phenylene sulfide, o-phenylene sulfide, phenylene sulfide sulfone, phenylene sulfide ketone, phenylene sulfide ether, diphenylene sulfide.

28. The tubular assembly according to any of the preceding claims, characterized in that the foamed polyphenylene sulfide polymeric material has a flammability index of V1 or V2 according to the UL94 test standard of Underwriters Laboratories.

29. The tubular assembly according to any of the preceding claims 1 to 30, characterized in that the foamed polyphenylene sulfide polymeric material has a flammability index of V0 according to the UL94 test standard of Underwriters Laboratories.

30. The tubular assembly according to any of the preceding claims, characterized in that the first member comprises a first layer of the assembly and the second member comprises a second layer of the assembly adjacent to the first layer.

31. The tubular assembly according to any of the preceding claims, characterized in that the first member comprises a metallic material.

32. The tubular assembly according to any of the preceding claims, characterized in that one or both of the first member or the second member can be slidably moved with respect to the other of the first member or the second member.

33. The tubular assembly according to any of the preceding claims, characterized in that the first member and the second member are not joined together.

34. The tubular assembly according to any of the preceding claims, characterized in that the first member and the second member are continuously joined together along the length of the assembly.

35. The tubular assembly according to any of the preceding claims, characterized in that the first member and the second member are joined together randomly or sequentially along the length of the assembly.

36. The tubular assembly according to any of the preceding claims, characterized in that the second member defines a more outer surface of the tubular assembly.

37. The tubular assembly according to any of the preceding claims, characterized in that it further comprises one or more intermediate tubular members arranged between the first member and the second member.

38. The tubular assembly according to any of the preceding claims, characterized in that it further comprises one or more third tubular members, wherein each of the third members is the same as or different from the first member and is the same as or different from each of the other third members, wherein the second member surrounds the first member and each of the third tubular members.

39. The tubular assembly according to claim 38, characterized in that it further comprises a first intermediate layer surrounding the first member and each of one or more third members, and is disposed between the second member and the first member and each of the third members.

40. The tubular assembly according to claim 38 or claim 39, characterized in that it further comprises an individual fourth member surrounding the corresponding member of the first member and each of the third members, the fourth member comprising a foamed polyphenylene sulfide polymeric material having a foamed density that is foamed from an unfoamed polyphenylene sulfide polymeric material having an unfoamed density, wherein the foamed density of the foamed polyphenylene sulfide polymeric material of the fourth member is less than approximately 50% of the unfoamed density of the unfoamed polyphenylene sulfide polymeric material of the fourth member, and wherein the foamed polyphenylene polymeric material of the fourth member is the same as or different from the foamed polyphenylene polymeric material of the second member.

41. The tubular assembly according to any of claims 1 to 39 above, characterized in that it further comprises: one or more third tubular members, wherein each of the third members is the same as or different from the first member and the same as or different from each of the other third members; and at least two fourth tubular members, wherein each fourth member surrounds a corresponding member of the first and third members, each fifth member comprising a foamed polyphenylene sulfide polymeric material having a foamed density that is foamed from an unfoamed polyphenylene sulfide polymeric material having an unfoamed density, wherein the foamed density of the foamed polyphenylene sulfide polymeric material of the fourth member is less than approximately 50% of the unfoamed density of the unfoamed polyphenylene sulfide polymeric material of the fourth member;wherein the foamed polyphenylene polymeric material of the fourth member is the same as or different from the foamed polyphenylene polymeric material of the second member.; 42. The tubular assembly according to claim 41, characterized in that each fourth member extends continuously axially along and continuously circumferentially around the corresponding first and third member, whereby the fourth members radially isolate the first and third member from an environment and from each other.

43. The tubular assembly according to any of the preceding claims, characterized in that it further comprises a heating element disposed between the first member and the second member, and extending along the length of the first member.

44. The tubular assembly according to any of the preceding claims 1-37 and 41-43, characterized in that it further comprises a fifth tubular member surrounding the second member.

45. A method for performing tubular assembly according to any of the preceding claims, characterized in that it comprises the step of: (a) foaming the unfoamed polyphenylene polymeric material around the outer surface of the first member to form the second member.

46. ​​The method according to claim 45, characterized in that the non-foamed polyphenylene sulfide polymeric material is foamed in step (a) onto the outer surface of the first member. zn / nLn / Lznz / E / Yii 47. The method according to claim 45 or claim 46, characterized in that it further comprises the additional step prior to step (a) of extruding the non-foamed polyphenylene sulfide polymeric material onto the outer surface of the first member.

48. A method for using the tubular assembly according to any of the preceding claims, characterized in that it comprises the passage of fluid flowing within the first member, axially along the inner surface of the first member.

49. The method according to claim 48, characterized in that the steam flows within the first member, axially along the inner surface of the first member.

50. A tubular assembly, characterized in that it comprises: a first tubular member having an outer surface and an inner surface, wherein the inner surface defines a more interior surface of the assembly; and a second tubular member surrounding the outer surface of the first member, wherein the second member comprises a foamed polyphenylene sulfide polymeric material having a foamed thermal conductivity that is foamed from a mixture of a foaming agent and a non-foamed polyphenylene sulfide polymeric material having polymer chains that are branched or crosslinked, the polyphenylene sulfide having a non-foamed thermal conductivity, wherein the foamed polyphenylene sulfide polymeric material has an average cell diameter of at least 100 pm, and wherein the foamed thermal conductivity is at least approximately 50% lower than the non-foamed thermal conductivity.

51. The tubular assembly according to claim 50, characterized in that the foamed polyphenylene sulfide polymeric material has a foamed thermal conductivity of approximately 0.017-0.145 W / (mK).

52. The tubular assembly according to any of claims 50 to 51, characterized in that the polyphenylene sulfide polymeric material is selected from the group consisting of polyphenylene sulfide homopolymers, copolymers, mixtures, alloys and combinations thereof.