PFAS-FREE THERMOPLASTIC MULTI-LAYER FUEL LINE

Abstract

A multilayer fuel line comprises a liner layer, a barrier layer circumferentially surrounding the liner layer, and a cover layer circumferentially surrounding the barrier layer. The liner layer comprises polyterephthalamide and has an inner circumferential surface that defines a tubular flow channel extending axially through the multilayer fuel line. The inner circumferential surface of the liner layer has a specific surface resistivity of less than or equal to approximately 1 x 10⁶ ohms per square at 20 degrees Celsius. The barrier layer comprises ethylene vinyl alcohol. The cover layer defines an outer circumferential surface of the multilayer fuel line and comprises an aliphatic polyamide.

Description

INITIATIONThe information provided in this section is intended to generally illustrate the context of the disclosure. Work of the present inventors, insofar as described in this section, as well as aspects of the description that may not otherwise belong to the prior art at the time of filing, will not be expressly or silently recognized as prior art over the present disclosure.The present disclosure relates to layered thermoplastic pipes for transporting fuels.Pipes or conduits for the transport of liquid fuels are often made from thermoplastic materials and may have a layered structure that imparts a desirable combination of electrical conductivity, low fuel permeability, high chemical and thermal resistance, wear resistance, light weight, mechanical robustness, and flexibility to the conduits over a desired operating temperature range.SUMMARYA multi-layer fuel line is disclosed. The multilayer fuel rail includes a liner layer, a barrier layer circumferentially surrounding the liner layer, and a capping layer circumferentially surrounding the barrier layer. The liner layer has an inner circumferential surface defining a tubular flow passage extending axially through the multi-layer fuel line. The liner layer comprises poly terephthalamide. The inner circumferential surface of the liner layer has a surface resistivity of less than or equal to about 1 x 10 6 ohms per square at 20 degrees Celsius. The barrier layer comprises ethylene vinyl alcohol. The cap layer defines an outer circumferential surface of the multi-layer fuel rail. The top layer comprises an aliphatic polyamide.In aspects, the liner layer may comprise Poly(nonamethylenterephthalamid).The liner layer may be substantially free of esters and amides having a molecular weight of less than or equal to about 2000.The liner layer may comprise a continuous matrix phase and a dispersed phase dispersed throughout the continuous matrix phase. The continuous matrix phase may comprise the poly terephthalamide and the dispersed phase an electrically conductive agent.In aspects, the electrically conductive agent may comprise carbon.The continuous matrix phase may constitute by weight greater than or equal to about 80% to less than or equal to about 99.8% of the liner layer. The electrically conductive agent may constitute, by weight, greater than or equal to about 0.2% to less than or equal to about 20% of the liner layer.The liner layer may include an electrically conductive inner layer and an electrically insulating outer layer circumferentially surrounding the inner layer. The electrically conductive inner layer may form the inner circumferential surface of the liner layer and may comprise a continuous matrix phase of poly terephthalamide and a dispersed phase with an electrically conductive agent. The electrically insulating outer layer may comprise poly terephthalamide and have a surface resistivity greater than 1 x 10 6 ohms per square at 20 degrees Celsius.The multi-layer fuel rail may further include an intermediate layer circumferentially surrounding the liner layer and disposed between the liner layer and the barrier layer. The intermediate layer may comprise an aliphatic polyamide.In aspects, the intermediate layer may comprise poly(dodecanoyl-12-lactam).The intermediate layer may be physically and chemically directly bonded to the liner layer without the use of an adhesive.The barrier layer may form a seal around the tubular flow passage that prevents fuel vapors from passing through the multi-layer fuel line and escaping to the exterior.In some cases, the capping layer may comprise poly(dodecanoyl-12-lactam), poly(hexamethylene dodecanediamide), or a combination thereof.The multilayer fuel rail may further include a first adhesive layer disposed between the liner layer and the barrier layer and physically connecting the barrier layer to the liner layer, and a second adhesive layer disposed between the barrier layer and the cap layer and physically connecting the cap layer to the barrier layer. The first and second adhesive layers may each comprise a thermoplastic polymer.The multi-layer fuel rail may be substantially free of perfluoroalkyl substances, polyfluoroalkyl substances, and combinations thereof.The multi-layer fuel rail may be configured to withstand temperatures in a range from greater than or equal to about -40 degrees Celsius to less than or equal to about 130 degrees Celsius.A multilayer fuel rail according to one or more embodiments of the present disclosure includes a liner layer, an intermediate layer surrounding the liner layer in a circumferential direction, a barrier layer surrounding the intermediate layer in a circumferential direction, and a capping layer surrounding the barrier layer in a circumferential direction. The liner layer has an inner circumferential surface defining a tubular flow passage extending axially through the multi-layer fuel line. The intermediate layer comprises an aliphatic polyamide. The barrier layer comprises ethylene vinyl alcohol. The cap layer defines an outer circumferential surface of the multilayer fuel rail and includes an aliphatic polyamide. The liner layer has a composite structure comprising a continuous matrix phase and a dispersed phase dispersed in the continuous matrix phase. The continuous matrix phase comprises Poly(nonamethylenterephthalamid ) and the dispersed phase comprises an electrically conductive agent. The electrically conductive agent imparts a surface resistivity to the inner circumferential surface of the liner layer of less than or equal to about 1 x 10 6 ohms per square at 20 degrees Celsius.Poly(nonamethylenterephthalamid) of the liner layer may provide chemical resistance and low oligomer extraction to volatile liquid fuels to the inner circumferential surface of the liner layer.The barrier layer may form a seal surrounding the tubular flow passage circumferentially and preventing fuel vapors from passing through the multi-layer fuel line and escaping to the exterior.The intermediate layer, barrier layer and cap layer may be electrically insulating and have a surface resistivity of greater than 1 x 10 6 ohms per square at 20 degrees Celsius.The multi-layer fuel rail may be substantially free of perfluoroalkyl substances, polyfluoroalkyl substances, and combinations thereof.The multi-layer fuel rail may be configured to withstand temperatures in a range from greater than or equal to about -40 degrees Celsius to less than or equal to about 130 degrees Celsius.Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGSThe present disclosure will become more fully understood from the detailed description and the accompanying drawings, in which: FIG. 1 is a schematic cross-sectional view of a multi-layer fuel line according to one or more embodiments of the present disclosure. FIG. 2 is a schematic cross-sectional view of a multi-layer fuel line according to another embodiment of the present disclosure.In the drawings, reference numerals may be used repeatedly to identify similar and / or identical elements.DETAILED DESCRIPTIONA multilayer fuel line according to the present disclosure comprises a laminate of thermoplastic polymer layers including an electrically conductive poly terephthalamide liner layer. The poly terephthalamide liner layer provides the multilayer fuel line with low fuel permeability, high chemical and thermal resistance over a wide operating temperature range, high strength, dimensional stability, low oligomer extraction to the fuel, and electrical conductivity without the use of per- or polyfluoroalkyl substances (PFAS), e.g., perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS), polytetrafluoroethylene (PTFE), and combinations thereof. The poly terephthalamide liner layer can be used in combination with an ethylene vinyl alcohol barrier layer and an aliphatic polyamide topcoat to provide a lightweight multilayer fuel line that has exceptional chemical, thermal, and mechanical properties at relatively low cost compared to multilayer fuel lines based on PFAS for sufficient chemical and thermal resistance.Referring now to FIG. 1, a multi-layer fuel rail 10 has an outer circumferential surface 12 and an inner circumferential surface 14 defining a tubular flow passage 16 extending axially therethrough. The multilayer fuel rail 10 includes a liner layer 18, an optional interlayer 20, a barrier layer 22, a cap layer 24, and optional first and second adhesive layers 26, 28. The multi-layer fuel line 10 may be used for transporting or guiding liquid fuel, vapor fuel, or a combination thereof. The multi-layer fuel line 10 may be used, for example, for the transport or routing of volatile and / or heavy liquid fuels (e.g., diesel fuel). Examples of volatile liquid fuels include gasoline and aliphatic alcohols, e.g., methanol, ethanol, propanol, and / or butanol. The multi-layer fuel rail 10 may be used in motor vehicles and have an operating temperature range of about -40 degrees Celsius (° C.) to about 130° C. The multi-layer fuel rail 10 may have a thickness defined between the outer circumferential surface 12 and the inner circumferential surface 14 of greater than or equal to about 1 millimeter (mm) to less than or equal to about 5 mm.The liner layer 18 is the innermost layer of the multilayer fuel rail 10 and is configured to be electrically conductive and form a physical barrier that prevents the fuel flowing in the tubular flow passage 16 from entering, permeating, or degrading the multilayer fuel rail 10. The liner layer 18 has an inner surface 30 and an opposing outer surface 32, the inner surface 30 defining the inner circumferential surface 14 of the multi-layer fuel rail 10. The liner layer 18 has a composite structure comprising a continuous matrix phase and a dispersed phase dispersed throughout the continuous matrix phase. The continuous matrix phase may constitute, by weight, greater than or equal to about 80%, optionally about 90%, or optionally about 95% to less than or equal to about 99.8%, optionally about 99%, or optionally about 97% of the liner layer 18. The dispersed phase may comprise by weight greater than or equal to about 0.2%, optionally about 1%, or optionally about 3% to less than or equal to about 20%, optionally about 10%, or optionally about 5%, of the liner layer 18.The continuous matrix phase comprises poly terephthalamide. In some cases, the continuous matrix phase may consist essentially of or consist of poly terephthalamide. The poly terephthalamide is a partially aromatic and partially crystalline polyamide. The poly terephthalamide imparts exceptional thermal and chemical resistance, strength, wear and abrasion resistance to the liner layer 18 as well as good processability for extrusion and injection molding applications. In particular, the poly terephthalamide imparts high chemical resistance to fuels to the liner layer 18 and has low oligomer extraction or leaching of oligomers from the layer upon contact with fuel, particularly at high operating temperatures. Extraction or leaching of oligomers from components of the fuel system, e.g., fuel lines, may result in contamination of the fuel and / or plugging of the components of the fuel system. In aspects, the liner layer 18 may comprise Poly(nonamethylenterephthalamid), also known as PA9T. The poly terephthalamide may constitute by weight greater than or equal to about 80%, optionally about 90%, or optionally about 95% to less than or equal to about 99.8%, optionally about 99%, or optionally about 97% of the liner layer 18.The dispersed phase comprises an electrically conductive agent. The electrically conductive agent is distributed throughout at least a portion of the liner layer 18 and provides the desired electrical conductivity to the liner layer 18. For example, the electrically conductive agent may impart a surface resistivity to the liner layer 18 of less than or equal to about 1 x 10 6 ohms per square (ohm / sq), or optionally less than or equal to about 1 x 10 5 ohms / sq at 20 degrees Celsius (° C.). The electrically conductive agent may be substantially uniformly distributed throughout the continuous matrix phase or the concentration of the electrically conductive agent may vary within the composite structure of the liner layer 18. For example, the concentration of the electrically conductive agent may be relatively high in regions of the liner layer 18 disposed along the inner circumferential surface 14 of the multilayer hose 10 and relatively low in regions of the liner layer 18 disposed along the outer surface 32 of the liner layer 18. The electrically conductive agent may comprise particles of a carbon-based material, an electrically conductive polymer, or a combination thereof. Examples of carbon-based electrically conductive materials include carbon black (e.g., acetylene black), graphite, graphene (e.g., graphene nanoplatelets), carbon nanotubes (e.g., single and / or multi-wall carbon nanotubes), carbon fibers (e.g., carbon nanofibers), and / or Ketjenblack® among others. Examples of electrically conductive polymers include polyaniline, polythiophene, polyacetylene and / or polypyrrole. The electrically conductive agent may constitute, by weight, greater than or equal to about 0.2%, optionally about 1%, or optionally about 3% to less than or equal to about 20%, optionally about 10%, or optionally about 5%, of the liner layer 18.The liner layer 18 may be substantially free of additives and residual monomers and / or oligomers having a molecular weight of less than or equal to about 2000, optionally about 1000, or optionally about 100. Low molecular weight additives are often used in polymers (e.g., polyamides) to impart the materials with the desired processing properties and / or low temperature performance (e.g., impact strength). Examples of such additives include antioxidants (e.g., tris(2,4-di-tert-butylphenyl) phosphite), surfactants, lubricants, plasticizers (e.g., esters and / or amides), acid scavengers, crosslinking agents, and lubricants. For example, the liner layer 18 may be substantially free of ester plasticizers and amide plasticizers having a molecular weight of less than or equal to about 2000, optionally about 1000, or optionally about 100. Specific examples of ester plasticizers include phthalic acid esters (phthalates, e.g., dibutyl phthalate and / or dioctyl phthalate), fatty acid esters, polyhydric alcohol esters, phosphoric acid esters, trimellitic acid esters (trimellitic acid esters), and hydroxybenzoic acid esters. Specific examples of amide plasticizers are sulfonamides, e.g., benzene sulfonamide (e.g., N-butyl benzene sulfonamide) and / or toluene sulfonamide. In aspects, the liner layer 18 may be substantially free of amide monomers and / or oligomers having a molecular weight of less than or equal to about 2000, optionally about 1000, or optionally about 100.The liner layer 18 may be substantially free of perfluoroalkyl substances, polyfluoroalkyl substances, and combinations thereof. The liner layer 18 may be substantially free of PTFE, for example. The liner layer 18 may have a thickness between the inner surface 30 and the outer surface 32 of greater than or equal to about 0.1 mm to less than or equal to about 1 mm.The optional intermediate layer 20 surrounds the liner layer 18 in the circumferential direction and is disposed between the liner layer 18 and the barrier layer 22. The intermediate layer 20 may be electrically insulating and is configured to provide rigidity to the multi-layer fuel rail 10 and / or provide a good bond between the liner layer 18 and the barrier layer 22. The intermediate layer 20 comprises an aliphatic polyamide. The intermediate layer 20 may comprise, for example, poly(dodecanoyl-12-lactam), also known as PA12. The intermediate layer 20 may be physically and chemically directly bonded to the liner layer 18 without the use of an adhesive.The barrier layer 22 surrounds the liner layer 18 in the circumferential direction and is arranged between the liner layer 18 and the cover layer 24. In aspects where the multilayer fuel rail 10 includes the intermediate layer 20, the barrier layer 22 is disposed between the intermediate layer 20 and the capping layer 24. The barrier layer 22 may be electrically insulating and is configured to form a seal around the tubular flow passage 16 that prevents gases and / or vapors from permeating the multi-layer fuel line 10 and escaping into the exterior environment. The barrier layer 22 may comprise ethylene vinyl alcohol (EVOH).The cap layer 24 is the outermost layer of the multilayer fuel rail 10 and surrounds the barrier layer 22 in the circumferential direction. The cap layer 24 may be electrically insulating and is configured to provide flexibility, durability, and resistance to abrasion, wear, impact, and weather conditions (e.g., resistance to ozone, ultraviolet light, and hydrolysis) to the multilayer fuel rail 10. The cover layer 24 comprises an aliphatic polyamide. The cover layer 24 may comprise, for example, poly(dodecanoyl-12-lactam) (also known as PA12), poly(hexamethylene dodecanediamide) (also known as nylon 6,12 or PA612), or a combination thereof.The optional first adhesive layer 26 is disposed between the liner layer 18 and the barrier layer 22 and provides a strong physical bond therebetween. In cases where the multilayer fuel rail 10 includes the intermediate layer 20, the first adhesive layer 26 is disposed between and provides a strong physical bond between the intermediate layer 20 and the barrier layer 22. The first adhesive layer 26 comprises a polyolefin resin. The specific composition of the polyolefin resin may be selected based on the composition of the liner layer 18 and the barrier layer 22, and / or the intermediate layer 20 and the barrier layer 22.Optional second adhesive layer 28 is disposed between barrier layer 22 and cover layer 24 and provides a strong physical bond therebetween. The second adhesive layer 28 may comprise a thermoplastic polymer, e.g., a polyolefin resin. The specific composition of the thermoplastic polymer may be selected based on the composition of the barrier layer 22 and the cover layer 24.In aspects, the multilayer fuel rail 10 may include the liner layer 18, the barrier layer 22, and the cap layer 24, and be free of additional layers underlying the liner layer 18, overlying the cap layer 24, disposed between the liner layer 18 and the barrier layer 22, or disposed between the barrier layer 22 and the cap layer 24. In other aspects, the multilayer fuel rail 10 may include the liner layer 18, the intermediate layer 20, the barrier layer 22, the cap layer 24, and the first and second adhesive layers 26, 28, and be free of additional layers underlying the liner layer 18, overlying the cap layer 24, or disposed between the liner layer 18 and the cap layer 24.FIG. 2 illustrates another embodiment of a multi-layer fuel line 110. The multi-layer fuel rail 110 is similar in many respects to the multi-layer fuel rail 10, and like reference numerals within the various embodiments generally designate like or corresponding elements in the drawings. Accordingly, the description of the multilayer fuel pipe 10 is integrated with that of the multilayer fuel pipe 110, and the description of the issues common to the multilayer fuel pipe 10 and the multilayer fuel pipe 110 need not be repeated here.The multilayer fuel line 110 includes a liner layer 118, an optional interlayer 20, a vapor barrier layer 22, a capping layer 24, and optional first and second adhesive layers 26, 28. The liner layer 118 is the innermost layer of the multi-layer fuel rail 110 and has an inner surface 130 and an opposing outer surface 132, the inner surface 130 defining the inner circumferential surface 14 of the multi-layer fuel rail 110. The liner layer 118 has a two-layer structure including an inner layer 134 and an outer layer 136 circumferentially surrounding the inner layer 134. The inner layer 134 of the liner layer 118 defines the inner surface 130 of the liner layer 118 and the inner circumferential surface 14 of the multi-layer fuel line 110. The outer layer 136 defines the outer surface 132 of the liner layer 118. The inner layer 134 is electrically conductive and may have substantially the same chemical composition as well as the same physical properties as the liner layer 18. On the other hand, the outer layer 136 is electrically insulating and may have substantially the same composition as the continuous matrix phase of the liner layer 18. The outer layer 136 may include, consist essentially of, or consist of, for example, poly terephthalamide (e.g., Poly(nonamethylenterephthalamid)). The outer layer 136 may be substantially free of the electrically conductive agent. The outer layer 136 may have a surface resistivity of greater than 1 x 10 6 ohms / sq, or optionally greater than or equal to about 1×10] 14 ohms / sq at 20° C.In aspects, the multilayer fuel rail 110 may include the liner layer 118, the barrier layer 22, and the capping layer 24, and be free of additional layers underlying the liner layer 118, overlying the capping layer 24, disposed between the liner layer 118 and the barrier layer 22, or disposed between the barrier layer 22 and the capping layer 24. In other aspects, the multilayer fuel rail 110 may include the liner layer 118, the intermediate layer 20, the barrier layer 22, the cap layer 24, and the first and second adhesive layers 26, 28, and be free of additional layers underlying the liner layer 118, overlying the cap layer 24, or disposed between the liner layer 118 and the cap layer 24.The multi-layer fuel line 10, 110 may be manufactured by an extrusion process, e.g., a coextrusion process. In an extrusion process, a material having the same composition as one of the layers (e.g., 18, 20, 22, 24) is melted, fed to an extruder, and pressed through a die at high temperature and high pressure to form one of the layers. In a coextrusion process, multiple molten materials having different compositions corresponding to the various layers (e.g., 18, 22, and 24) may be fed into separate extruders and then forced through a single die where the molten materials are combined and concentrically and simultaneously applied around each other and over each other such that the layers adhere to each other to form the multilayer fuel line 10, 110. Alternatively, one or more of the inner layers (e.g., 18 and / or 22) of the multilayer fuel rail 10, 110 may be preformed (e.g., by extrusion) and then one or more of the surrounding layers (e.g., 22 and / or 24) may be formed over and concentrically around the one or more preformed inner layers. In some cases, the multi-layer fuel line 10, 110 may be manufactured through multiple extrusion and / or coextrusion processes. Before extrusion (or coextrusion), the starting materials can be dried in order to remove the residual water content from them.During the extrusion process, the thickness of the layers (e.g., 18, 20, 22, 24) may be measured (e.g., with a laser) and controlled or adjusted by controlling or adjusting extruder settings as the layers are extruded. The multi-layer fuel line 10, 110 may be cooled as it exits the extruder and either wound into rolls or cut to a desired length. Each cut length of the multi-layer fuel line 10, 110 may be placed in a mold to assume a preconfigured shape and heated (e.g., on a belt passing through an oven) to soften the multi-layer fuel line 10, 110 and produce the shape dictated by the mold. After the molded multi-layer fuel conduit 10, 110 is cooled, a fitting may be pressed into an open end of the conduit to form a finished fuel conduit assembly.The foregoing description is for illustrative purposes only and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure may be practiced in a variety of forms. Therefore, while this disclosure includes specific examples, the true scope of the disclosure should not be so limited as other modifications will become apparent upon examination of the drawings, the specification, and the following claims. It should be appreciated that one or more steps within a method may be performed in different order (or simultaneously) without altering the principles of the present disclosure. Although each of the above-described embodiments has particular features, one or more of these features described with respect to any embodiment of the disclosure may be implemented in and / or combined with features of any other embodiments, even if this combination is not expressly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.The terminology used herein is for the purpose of describing example embodiments only and is not to be taken as limiting. As used herein, the singular forms "a," "an," and "the" may also include the plural forms unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, elements, compositions, steps, integers, operations, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Although the open terms "comprises," "comprising," "including," and "having" are to be understood as non-limiting terms that serve to describe and claim various embodiments set forth herein, in certain aspects, the terms may alternatively be understood as more limiting and restrictive terms, such as "consisting of" or "consisting essentially of.". Therefore, for any given embodiment that specifies compositions, materials, components, elements, ingredients, features, integers, operations, and / or process steps, the present disclosure expressly also includes embodiments that consist of or consist essentially of such specified compositions, materials, components, elements, ingredients, features, integers, operations, and / or process steps. In the case of "consisting of", the alternative embodiment excludes any additional compositions, materials, components, elements, ingredients, features, integers, operations, and / or process steps, while in the case of "consisting essentially of", any additional compositions, materials, components, elements, ingredients, features, integers, operations, and / or process steps that significantly impact the basic and novel characteristics are excluded from such an embodiment, but any compositions, materials, components, elements, ingredients, features, integers, operations, and / or process steps that do not significantly impact the basic and novel characteristics may be included in the embodiment.All method steps, processes, and operations described herein are not to be construed as necessarily requiring execution in the order discussed or illustrated, unless expressly characterized as the order of execution. It will also be appreciated that additional or alternative steps may be employed, unless otherwise indicated.When a component, element, or layer is referred to as being "on" or "engaged to" another element or layer, or as being "connected" or "coupled" to it, it may be directly on or engaged to the other component, element, or layer, or be connected or coupled to it, or intervening elements or layers may be present. On the other hand, when an element is referred to as being "directly on" or "directly engaged to" another element or layer, or as being "directly connected" or "directly coupled" to it, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent," or "adjacent" versus "directly adjacent" or "directly adjacent," etc.). As used herein, the term "and / or" includes combinations of one or more of the associated listed items.Although the terms "first," "second," "third," etc. may be used herein to describe various steps, elements, components, regions, layers, and / or sections, these steps, elements, components, regions, layers, and / or sections should not be limited by these terms unless otherwise specified. These terms may be used only to distinguish one step, element, component, region, layer, or portion from another step, element, component, region, layer, or portion. Terms such as "first / r", "second / r", and other numerical terms, when used herein, do not imply a sequence or order unless the context clearly indicates. Thus, a first step, element, component, region, layer, or portion discussed below could be referred to as a second step, element, component, region, layer, or portion without departing from the teachings of the embodiments.Spatially or temporally relative terms such as "before," "after," "inner," "outer," "below," "under," "lower," "over," "upper," and the like may be used herein for convenience to describe the relationship of an element or feature to one or more other elements or features as illustrated in the figures. Spatially or temporally relative terms may be intended to include different orientations of the device or system in use or operation in addition to the orientation depicted in the figures.Throughout this disclosure, the numerical values represent approximate dimensions or limits for ranges and include minor deviations from the stated values and embodiments, such as those having the stated value, as well as those having exactly the stated value. Unlike the working examples at the end of the detailed description, all numerical values of parameters (e.g., amounts or conditions) in this specification are to be understood as being modified by the term "about" in all cases, regardless of whether or not "about" actually appears before the numerical value. Numerical values of parameters in the appended claims are to be understood as modified by the term "about" only if this term appears before the numerical value. "about" means that the numerical value indicated permits slight imprecision (with some approximation to the accuracy of the value, approximately or rather close to the value, fast). Where the imprecision given by "about" is not otherwise understood by this common meaning in the art, then "about" as used herein means at least modifications that may result from common methods of measuring and using such parameters. For example, "about" may comprise a deviation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in certain aspects, optionally less than or equal to 0.1%. Moreover, the disclosure of ranges includes the disclosure of all values and further divided ranges within the entire range, including the endpoints and the sub-ranges indicated for the ranges.As used herein, the terms "composition" and "material" are used interchangeably to refer generally to a substance that contains at least the preferred chemical components, elements or compounds, but which may also contain additional elements, compounds or substances, including traces of impurities, unless otherwise specified. An "X-based" composition or material generally refers to compositions or materials wherein "X" is the largest single component of the composition or material in weight percent (%). This may include both compositions or materials having a weight fraction of greater than 50% X and compositions or materials having a weight fraction of less than 50% X, as long as X is the largest single component of the composition or material based on its total weight. When a composition or material is referred to as being "substantially free" of a substance, the composition or material may contain less than 5%, optionally less than 3%, optionally less than 1%, or optionally less than 0.1% of the substance.As used herein, the term "metal" may refer to a pure elemental metal or an alloy of an elemental metal and one or more other metal or non-metal elements (referred to as "alloying elements"). The alloying elements can be selected to impart certain desirable properties to the alloy that the parent metal element does not have.

Claims

A multi-layer fuel rail comprising: a liner layer having an inner circumferential surface defining a tubular flow passage extending in an axial direction through the multi-layer fuel rail, the liner layer comprising poly terephthalamide, the inner circumferential surface of the liner layer having a surface resistivity of less than or equal to about 1 x 10 6 ohms per square at 20 degrees Celsius; a barrier layer surrounding the liner layer in a circumferential direction, the barrier layer comprising ethylene vinyl alcohol and forming a seal around the tubular flow passage that prevents fuel vapors from permeating the multi-layer fuel rail and escaping into the external environment; and a capping layer surrounding the barrier layer in a circumferential direction and defining an outer circumferential surface of the multi-layer fuel rail, the capping layer comprising an aliphatic polyamide.The multi-layer fuel line of claim 1, wherein the liner layer comprises Poly(nonamethylenterephthalamid).The multilayer fuel line of claim 1, wherein the liner layer is substantially free of esters and amides having molecular weights less than or equal to about 2000.The multilayer fuel line of claim 1, wherein the liner layer comprises: a continuous matrix phase; and a dispersed phase dispersed throughout the continuous matrix phase, wherein the continuous matrix phase comprises the poly terephthalamide and the dispersed phase comprises an electrically conductive carbon comprising agent.The multilayer fuel line of claim 1, wherein the liner layer comprises: an electrically conductive inner layer defining the inner circumferential surface of the liner layer and comprising a continuous matrix phase containing poly terephthalamide and a dispersed phase containing an electrically conductive agent; and an electrically insulating outer layer circumferentially surrounding the inner layer, wherein the electrically insulating outer layer comprises poly terephthalamide and has a surface resistivity greater than 1 x 10 6 ohms per square at 20 degrees Celsius.The multilayer fuel line of claim 1, further comprising: an intermediate layer circumferentially surrounding the liner layer and disposed between the liner layer and the barrier layer, wherein the intermediate layer comprises an aliphatic polyamide.The multilayer fuel line of claim 6, wherein the intermediate layer comprises poly(dodecanoyl-12-lactam) and wherein the intermediate layer is directly physically and chemically bonded to the liner layer without the use of an adhesive.The multi-layer fuel line of claim 1, wherein the cap layer comprises poly(dodecanoyl-12-lactam), poly(hexamethylene dodecanediamide), or a combination thereof.The multilayer fuel line of claim 1, further comprising: a first adhesive layer disposed between the liner layer and the barrier layer that physically bonds the barrier layer to the liner layer; and a second adhesive layer disposed between the barrier layer and the cap layer and physically bonds the cap layer to the barrier layer, wherein the first and second adhesive layers each comprise a thermoplastic polymer.The multi-layer fuel rail of claim 1, wherein the multi-layer fuel rail is substantially free of perfluoroalkyl substances, polyfluoroalkyl substances, and combinations thereof, and wherein the multi-layer fuel rail is configured to withstand temperatures in a range from greater than or equal to about -40 degrees Celsius to less than or equal to about 130 degrees Celsius.

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