[0001] The present disclosure generally relates to a polymeric pipe made substantially of polymeric materials. In particular, the present disclosure relates to a multipurpose polymeric pipe that comprises a barrier layer.

BACKGROUND

[0002] Polymeric pipes are widely used for conveying cold and hot water. Such pipes may be used for both heating and tap water applications (within a utility-distribution region and within a structure, such as a building). Traditionally, different types of polymeric pipes are used for different applications. When using polyethylene as the polymeric material, the polyethylene is usually modified in order to meet requirements relating to pressure and temperature resistance. By crosslinking the polyethylene, the pressure and temperature resistance overlong term use may be increased to such a level that the crosslinked polyethylene may be used for both cold water applications (for example potable water transport) and hot water applications (for example radiant heating and/or potable-water transport). In the case of polyethylene pipe, this is generally achieved through crosslinking of the polymer backbone using peroxides, silanes, and/or electron- beam irradiation. [0003] Heating pipe (commonly referred to as radiant floor-heating pipe) is typically used along with a variety of other components in a heating system. Heating pipe requires significant ultraviolet (UV) light stability since it is often exposed to sunlight for extended periods of time during the construction phase of where the heating pipe will be installed. Additionally, heating pipe should have limited oxygen permeability, because oxygen diffusion can lead to oxidation and rusting of metal components within the heating system (such as pumps, valves, couplings and heat exchangers).

[0004] A well-known method for protecting radiant floor-heating pipes against oxygen migration through the pipe involves adding a barrier layer to the surface of the pipe. Although this design may be adequate for some purposes, it has limitations. For example, one common method for joining crosslinked polyethylene pipes, or adding valves to heating pipes, involves a process in which a coupling grips and seals the outside of the pipe. SHARKBITE ^® couplings (SHARKBITE is a registered trademark of RevMedx Inc., Wilsonville, OR, USA), GATORBITE ^® (GATORBITE is a registered trademark of Elkhart Products Corp. , Elkhart, IN, USA), and TECTITE ^® (TECTITE is a registered trademark of Pegler Yorkshire Group Ltd., Yorkshire, UK) are three such examples. Although this process is effective, the thin blocking layer at or near the surface is susceptible to damage. [0005] Pipe designed for potable-water applications is subject to a different set of requirements. In particular, pipe designed for potable-water applications must be resistant to oxidation by chlorine or other oxidants (such as ozone, hypochlorite, or chlorine dioxide) that are common in potable-water supplies. This resistance is often accomplished by incorporating high levels of antioxidant additives into the polymeric material of the potable-water pipe to consume the oxidant before it degrades the polymer's backbone. Degrading of the backbone by oxidants, or otherwise, may be problematic in that it may lead to crazing and cracking of the polymeric pipe.

[0006] Additionally, potable-water pipe materials are subject to significant restrictions relating to toxicity. The materials that are suitable for inclusion in potable-water pipes are restricted to reduce the extent to which organic and inorganic pipe-components leach into the water. In this respect, potable-water pipe materials are selected based (at least in part) on having initiators and additives that are locked into the polymer's matrix or that have been shown through extensive testing to be non-toxic. This restriction limits the choices available.

SUMMARY

[0007] The present disclosure provides a multipurpose polymeric pipe. In particular, the present disclosure provides a polymeric pipe that may be used for both cold and hot water applications. The multipurpose polymeric pipe of the present disclosure may satisfy the disparate requirements of radiant floor-heating applications and potable-water applications. Because a single type of pipe may be used for both applications, the multipurpose polymeric pipe of the present disclosure may reduce inventory requirements and simplify manufacturing processes. [0008] The polymeric pipe of the present disclosure has a multilayer structure comprising an inner polymeric layer, an outer polymeric layer, and a barrier layer interposed between the inner polymeric layer and the outer polymeric layer. The barrier layer is substantially impermeable to components of both the inner polymeric layer and the outer polymeric layer. Because the barrier layer is interposed between the inner polymeric layer and the outer polymer layer - and because it is substantially impermeable to components the inner polymeric layer and the outer polymeric layer - the composition of the inner polymeric layer and the composition of the outer polymeric layer may be selected independently. Accordingly, the composition of the inner polymeric layer may be selected in view of toxicity-related restrictions associated with potable-water transport applications, while the composition of the outer polymeric layer may selected in view of other factors (e.g. durability, cost, and/or ease of manufacturing). In particular, the inner polymer layer may have an anti-oxidant, an initiator, a residual from a crosslinking reaction, or a combination thereof that is known to satisfy toxicity related restrictions associated with potable-water transport applications. In contrast, the outer polymer layer may have a UV-protectant, an anti-oxidant, an initiator, a residual from a crosslinking reaction, or a combination thereof that is selected in view of durability, cost, and/or ease of manufacturing.

[0009] Select embodiments of the present disclosure relates to a polymeric pipe, comprising: an inner polymeric layer that has a thickness (A) and that comprises a first anti-oxidant; an outer polymeric layer that has a thickness (C) and that comprises a UV-protectant; and a barrier layer that has a thickness (B), that is interposed between the inner polymeric layer and the outer polymeric layer. The barrier layer is substantially impermeable to an oxidant, the first anti-oxidant, and the UV-protectant. The polymeric pipe has a wall thickness (D) that comprises the thickness (A) of the inner polymeric layer, the thickness (B) of the barrier layer, and the thickness (C) of the outer polymeric layer. The polymeric pipe is co- extruded such that the thickness (A) of the inner polymeric layer accounts for between about 1 % and about 40 % of the wall thickness (D) of the polymeric pipe.

[0010] Select embodiments of the present disclosure relate to a radiant heating system comprising a polymeric pipe as defined herein. [0011] Select embodiments of the present disclosure relate to a potable water transport system comprising a polymeric pipe as defined herein.

[0012] Select embodiments of the present disclosure relate to use of a polymeric pipe as defined herein in a radiant heating application.

[0013] Select embodiments of the present disclosure relate to use of a polymeric pipe as defined herein to transport potable water.

[0014] Select embodiments of the present disclosure relate to a method of manufacturing a polymeric pipe, the method comprising: co-extruding: (i) an inner polymeric layer that comprises a first crosslinkable polymer and a first crosslinking-reaction initiator, (ii) a barrier layer, and (iii) an outer polymeric layer that comprises a second crosslinkable polymer and a second crosslinking-reaction initiator, to form the polymeric pipe; and irradiating the polymeric pipe with infrared radiation to crosslink the first crosslinkable polymer in the inner polymeric layer and to crosslink the second crosslinkable polymer in the outer polymeric layer.

BRIEF DESCRIPTION OF THE DRAWINGS [0015] These and other features of the present disclosure will become more apparent in the following detailed description in which reference is made to the appended drawings. The appended drawings illustrate one or more embodiments of the present disclosure by way of example only and are not to be construed as limiting the scope of the present disclosure. [0016] FIG. 1 shows a cross-section of a polymeric pipe according to one select embodiment of the present disclosure. DETAILED DESCRIPTION

[0017] In the present disclosure, all terms referred to in singular form are meant to encompass plural forms of the same. Likewise, all terms referred to in plural form are meant to encompass singular forms of the same. [0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0019] As used herein, the term "about" refers to an approximately +/-10% variation from a given value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to.

[0020] As used herein, the term "crosslinking" means a process for linking polymer chains thus causing a spatial network to form. The related terms "crosslink", "crosslinked", and "crosslinkable" will be readily understood by those skilled in the art in view of the present meaning of the term "crosslinking". In the synthetic polymer science field, crosslinking usually refers to the use of crosslinks to promote a difference in a polymers' physical properties. By way of non-limiting example, crosslinked polyethylene (PEX) is a form of polyethylene with crosslinks. PEX contains crosslinked bonds that form part of the polymer's three dimensional structure, which change the thermoplastic polymer to a thermoset polymer. There are three main manufacturing processes for preparing crosslinked polymeric pipes: the peroxide method, the silane method, and the electronic-irradiation method.

[0021] As used herein, the term "infrared radiation" means a wavelength of light from within the infrared region of the radiation spectrum. Infrared radiation may be provided, by way of non-limiting example, from an infrared lamp that emits strongly within an emission band of about 1 micron to about 1 .7 microns. A person skilled in the art will realize that the maximum of the emission band, and consequently the intensity of the emission of an infrared lamp, depends on the power applied to the infrared lamp. [0022] As used herein, the term "pipe" describes a hollow elongated tube or cylinder for conducting, by way of non-limiting example, a liquid, a gas, a finely divided solid, or a combination thereof.

[0023] As used herein, the phases "substantially infrared radiation transparent" and "substantially transparent to infrared radiation" describe a material property that is characterized by weak absorptions in the infrared regions of the radiation spectrum so that some, most or substantially all of the infrared radiation penetrates deep into the material. Such weak absorptions may provide thermal energy. [0024] Traditionally, radiant heating applications and potable water transport applications have required different polymeric pipes. Select embodiments of the polymeric pipe described herein may serve as a multipurpose pipe that is suitable for use in both radiant heating applications and potable water transport applications. The multipurpose polymeric pipe may be used, by way of non-limiting example, for applications such as within a utility-distribution region and within a structure such as a building.

[0025] The polymeric pipe of the present disclosure has a multilayer structure comprising an inner polymeric layer, an outer polymeric layer, and a barrier layer interposed between the inner polymeric layer and the outer polymeric layer. The barrier layer is substantially impermeable to components of both the inner polymeric layer and the outer polymeric layer. Because the barrier layer is interposed between the inner polymeric layer and the outer polymer layer - and because it is substantially impermeable to components the inner polymeric layer and the outer polymeric layer - a number of features of the inner polymeric layer and the outer polymeric layer can be independently optimized.

[0026] First, the composition of the inner polymeric layer and the composition of the outer polymeric layer may be selected independently. Accordingly, the composition of the inner polymeric layer may be selected in view of toxicity-related restrictions associated with potable-water transport applications, while the composition of the outer polymeric layer may selected in view of other factors (e.g. durability, cost, and/or ease of manufacturing). In particular, the inner polymer layer may have an anti-oxidant, an initiator, a residual from a crosslinking reaction, or a combination thereof that is known to satisfy toxicity related restrictions associated with potable-water transport applications. In contrast, the outer polymer layer may have a an anti-oxidant, an initiator, a residual from a crosslinking reaction, or a combination thereof that is selected in view of durability, cost, and/or ease of manufacturing.

[0027] Second, the thickness of the inner polymeric layer and the thickness of the outer polymeric layer may be selected independently. In particular, the thickness of the inner polymeric layer may be relatively low, such that the inner polymeric layer accounts for a minor percentage of the wall thickness of the polymeric pipe. Because the thickness of the inner polymeric layer may be relatively low, it may be unlikely to bubble during crosslinking (a common limitation that prevents the use of some initiators in high-thickness layers). In contrast, the thickness of the outer polymeric layer may be relatively high, such that the inner polymeric layer accounts for a major percentage of the wall thickness of the polymeric pipe. Because the thickness of the outer polymeric layer may be relatively high, it may be configured to provide a majority of the structural integrity of the pipe.

[0028] Third, the outer polymeric layer may comprise a UV- (ultra violet) protectant to provide enhanced UV protection to the polymeric pipe. The inclusion of a UV-protectant in the outer polymeric layer may improve the durability of the polymeric pipe. The inclusion of the UV-protectant in the outer polymeric layer may obviate the need for a UV-protectant in the inner layer. As such, the inner polymeric layer may have additional capacity to accommodate, by way of non- limiting example, a higher loading of an anti-oxidant.

[0029] Fourth, the outer polymeric layer and the inner polymeric layer may be independently configured to be substantially transparent to IR (infrared) radiation. An outer polymeric layer that is substantially transparent to IR radiation may allow for an additional suite of crosslinking reactions to be used during manufacture of the polymeric pipe. [0030] Embodiments of the present disclosure will now be described by reference to FIG. 1 , which shows a select embodiment of a polymeric pipe.

[0031] FIG. 1 shows a cross section of a polymeric pipe 100 that comprises an outer wall 101 and an inner wall 102. The outer wall 101 of the polymeric pipe 100 forms an elongate exterior surface of the polymeric pipe 100. The outer wall 101 may define a cross-sectional shape of a circle. The inner wall 102 of the polymeric pipe 100 may form an elongate interior surface of the polymeric pipe 100. The inner wall 102 may define shape of a circular cylinder. In select embodiments of the present disclosure, the outer wall 101 and the inner wall 102 may be concentric. However, as will be appreciated by those skilled in the art, the present disclosure also contemplates other cross-sectional shapes of the outer wall 101 and the inner wall 102 that may be made during an extrusion process, a co-extrusion process or other applicable processes. The cross-sectional shape of the outer wall 101 and the inner wall 102 may be the same, or not. [0032] The polymeric pipe 100 comprises an outer polymeric layer 104, an inner polymeric layer 105 and a barrier layer 103 that is interposed between the outer polymeric layer 104 and the inner polymeric layer 105. In select embodiments of the present disclosure, all of the layers 103, 104 and 105 the polymeric pipe 100 may be formed at the same time by co-extrusion. [0033] The inner polymeric layer 105 has a thickness (A). The barrier layer 103 has a thickness (B). The outer polymeric layer 104 has a thickness (C). The polymeric pipe 100 has a wall thickness (D) that comprises the thickness (A) of the inner polymeric layer 105, the thickness (B) of the barrier layer 103, and the thickness (C) of the outer polymeric layer 104. [0034] In select embodiments of the present disclosure, the outer diameter of the polymeric pipe may be between about 12 mm to about 100 mm, and the wall thickness (D) of the polymeric pipe 100 may be between about 2 mm to about 10 mm.

[0035] In select embodiments of the present disclosure, the polymeric pipe 100 is co-extruded such that the thickness of the inner polymeric layer 105 accounts for between about 1 % and about 40 % of the wall thickness (D) of the polymeric pipe 100. In select embodiments of the present disclosure, the thickness of the inner polymeric layer 105 may account for between about 2 % and about 20 % of the wall thickness (D) of the polymeric pipe 100. In select embodiments of the present disclosure, the thickness of the inner polymeric layer 105 may be between about 0.075 mm to about 2.5 mm.

[0036] Unlike the thickness (A) of the inner polymeric layer 105 and the thickness (C) of the outer polymeric layer 104, the thickness (B) of the barrier layer 103 may not scale with the wall thickness (D) of the polymeric pipe 100. Instead, the thickness (B) of the barrier layer 103 may be independent (and optionally relatively constant) between pipes with walls of varying wall thicknesses (D). In other words, a smaller, thin-walled pipe and a larger thick-walled pipe may have barrier layers 103 that are similar with respect to the thickness (B). In select embodiments of the present disclosure, the thickness (B) of the barrier layer 103 may account for between about 0.03 mm and about 0.2 mm of the wall thickness (D) of the polymeric pipe 100. In particular, the thickness (B) of the barrier layer 103 may account for between about 0.06 mm and about 0.1 mm of the wall thickness (D) of the polymeric pipe 100.

[0037] In select embodiments of the present disclosure, the thickness (C) of the outer polymeric layer 104 may account for between about 60 % and about 98.7 % of the wall thickness (D) of the polymeric pipe 100. In particular, the thickness (C) of the outer polymeric layer 104 may account for between about 80 % and about 98.7 % of the wall thickness (D) of the polymeric pipe 100. In select embodiments of the present disclosure, the thickness (C) of the outer polymeric layer 104 may be between about 1 .2 mm and about 9.87 mm. [0038] In select embodiments of the present disclosure, the outer polymeric layer 104 may be comprised of at least one synthetic polymer. The at least one synthetic polymer may be, by way of non-limiting example, polyethylene, crosslinked polyethylene, polybutene, polyethylene of raised temperature resistance (PE-RT), or a combination thereof. [0039] The outer polymeric layer 104 comprises a UV (ultraviolet)- protectant. In select embodiments of the present disclosure, the UV-protectant may have a loading between about 0.05 % and about 0.3 % on a mass basis relative to the total mass of the constituents of the outer polymeric layer 104. In particular, the UV-protectant may have a loading between about 0.15 % and about 0.3 % on a mass basis relative to the total mass of the constituents of the outer polymeric layer 104.

[0040] In select embodiments of the present disclosure, the UV protectant may be an inorganic pigment, an organic pigment, a dye, a fluorescent compound, a free-radical scavenging compound, a hindered-amine light stabilizer, a phosphite, a hindered phenol, or a combination thereof. The inorganic pigment may be, by way of non-limiting example, titanium dioxide, zinc oxide, cerium oxide, tin oxide, indium tin oxide, or a combination thereof. The organic pigment may be, by way of non-limiting example, carbon black. The free-radical scavenging compound may be, by way of non-limiting example, benzophenone, a benzotriazole phenol, bisoctatriazole, or a combination thereof. [0041] In select embodiments of the present disclosure, the outer polymeric layer 104 may further comprise an anti-oxidant. The anti-oxidant may be present in an amount between about 0.2 % and about 0.7 % on a mass basis relative to the total mass of the constituents of the outer polymeric layer 104. In particular, the anti-oxidant may be present in an amount between about 0.4 % and about 0.7 % on a mass basis relative to the total mass of the constituents of the outer polymeric layer 104.

[0042] In select embodiments of the present disclosure, the outer polymeric layer 104 may further comprise a residual of a crosslinking reaction. The residual of the crosslinking reaction may be, by way of non-limiting example, an unreacted peroxide, a degradation product of a peroxide, a silane, or a combination thereof.

[0043] In select embodiments of the present disclosure, the inner polymeric layer 105 may be comprised of at least one synthetic polymer. The at least one synthetic polymer may be, by way of non-limiting example, polyethylene, crosslinked polyethylene, polybutene, PE-RT or a combination thereof. [0044] In select embodiments of the present disclosure, the inner polymeric layer 105 comprises an anti-oxidant. In select embodiments of the present disclosure, the anti-oxidant may be present in an amount between about 0.3 % and about 1.5 % on a mass basis relative to the total mass of the constituents of the inner polymeric layer 105. In particular, the anti-oxidant may be present in an amount between about 0.5 % and about 1 .1 % on a mass basis relative to the total mass of the constituents of the inner polymeric layer 105.

[0045] In select embodiments of the present disclosure, the anti-oxidant in the inner polymeric layer 105 may be, by way of non-limiting example, a compound identified by CAS # 65447-77-0, CAS # 154862-43-8, CAS # 6683-19-8, or a combination thereof. [0046] In select embodiments of the present disclosure, the inner polymeric layer 105 may further comprise a residual of a crosslinking reaction. The residual of the crosslinking reaction may be, by way of non-limiting example, an unreacted peroxide, a degradation product of a peroxide, a silane, or a combination thereof.

[0047] The barrier layer 103 is substantially impermeable to an oxidant such that the barrier layer 103 prevents or substantially reduces oxidant migration between the inner polymeric layer 105 and the outer polymeric layer 104. In select embodiments of the present disclosure, the oxidant may be oxygen, chlorine, ozone, hypochlorite, chlorine dioxide, or a combination thereof.

[0048] The barrier layer 103 is substantially impermeable to the UV protectant, the antioxidant in the inner layer 105, and the antioxidant in the outer layer 105.

[0049] In select embodiments of the present disclosure, the barrier layer 103 may be substantially impermeable to a residual of a crosslinking reaction. The residual of the crosslinking reaction may be, by way of non-limiting example, an unreacted peroxide, a degradation product of a peroxide a silane, or a combination thereof.

[0050] In select embodiments of the present disclosure, the barrier layer 103 may be comprised of a polymer. In particular, the barrier layer 103 may comprise ethylene vinyl alcohol (EVOH), polyethylene terephthalate-silicon dioxide nanoparticle mixtures, polyvinylbutyral-tripentaerythritol mixtures, or combinations thereof.

[0051] In select embodiments of the present disclosure, the outer polymeric layer 104 may be substantially infrared radiation transparent. In select embodiments of the present disclosure, the inner polymeric layer 105, the barrier layer 103, and the outer polymeric layer 104 may each be substantially infrared radiation transparent.

[0052] Without being bound to any particular theory, embodiments of the present disclosure in which at least the outer polymeric layer 104 is substantially infrared radiation transparent, may be suitable for a broad range of crosslinking synthetic methods. By way of a non-limiting example, a crosslinking synthetic method may be induced by infrared radiation of a polymer that is substantially infrared radiation transparent, wherein weak absorptions of the infrared radiation provide an amount of thermal energy that is sufficient to activate cross-linking reaction initiators. Such methods will be readily ascertained by a person skilled in the art having regard to the present disclosure and will therefore not be set out in detail herein.

[0053] In select embodiments of the present disclosure, the barrier layer 103 may be fastened via an adhesive to the outer polymeric layer 104, the inner polymeric layer 105, or a combination thereof. By way of non-limiting example, the adhesive may be a polymer adhesive such as ADMER 426 ^® (ADMER is a registered trademark of Mitsui Chemicals Incorporated, Tokyo, Japan), NUCREL ^® acid copolymers (NUCREL is a registered trademark of Du Pont de Nemours and Company Corporation, Wilmington, DW, USA), BYNEL ^® adhesive (BYNEL is a registered trademark of Du Pont de Nemours and Company Corporation, Wilmington, DW, USA), or a combination thereof.

[0054] In select embodiments of the present disclosure, the barrier layer 103 may be chemically bonded to the outer polymeric layer 104, the inner polymeric layer 105, or a combination thereof via an adhesive. By way of non- limiting example, The chemical bonding may be achieved by crosslinking via heat treatment. During the heat treatment, chemical bonds between the outer polymeric layer 104 and the barrier layer 103 may be formed due to radical recombination of radicals formed in the outer polymeric layer 104 and in the barrier layer 103. Likewise, during the heat treatment, chemical bonds between the inner polymeric layer 105 and the barrier layer 103 may be formed due to radical recombination of radicals formed in the inner polymeric layer 105 and in the barrier layer 103. In select embodiments, a radical initiator may be added to the inner polymeric layer 105, the barrier layer 103, the outer polymeric layer 104, or a combination thereof to promote radical formation and crosslinking during a heat treatment for creating chemical bonds between two or more of the layers 103, 104 and 105. [0055] In select embodiments of the present disclosure, the polymeric pipe 100 may be employed in a radiant heating system. In select embodiments of the present disclosure relating to radiant heating, water may be circulated in a closed system of polymeric pipes 100. In select embodiments of the present disclosure, the radiant heating system may further comprise a metal component. The metal component may be, by way of non-limiting example, a pump, a valve, a coupling, a heat exchanger or a combination thereof.

[0056] In select embodiments of the present disclosure, the polymeric pipe 100 may be employed in a potable water transport system. Many traditional potable water transport systems employ pipes that comprise polymer materials. In such systems, chemicals contained by or found within the polymeric materials may slowly diffuse into the water. These chemicals may appear as a result of a crosslinking reaction during the preparation of the polymeric materials or from additives, such as anti-oxidants, which may be added to the polymeric material in order to improve the resistance properties of the pipe for long term use. This may cause problems relating to the smell and/or taste of the water. Moreover, the diffusion of chemicals contained by, or found within, the polymeric materials into the water may cause health problems for consumers of the water from the potable water system. These chemicals must also be excluded from the water supply. Moreover, potable water is often highly chlorinated. During long term use of a traditional potable water transportation system, there is a risk of chlorine diffusion from the water through a pipe wall, which may weaken the properties of the pipe. Traditionally, this risk is mitigated by adding stabilizers that prevent this effect, but this is undesirable due to the high price of such stabilizers and because high stabilizer loads may mechanically weaken the pipe. Because the barrier layer 103 of the present disclosure is substantially impermeable to oxidants such as chlorine, the polymeric pipe 100 of the present disclosure may be suitable for long term use in a potable water transport system. [0057] Select embodiments of the present disclosure relate to a method of manufacturing a polymeric pipe 100, the method comprising: co-extruding: (i) the inner polymeric layer 105 that comprises a first crosslinkable polymer and a first crosslinking-reaction initiator, (ii) the barrier layer 103, and (iii) the outer polymeric layer 104 that comprises a second crosslinkable polymer and a second crosslinking-reaction initiator to form the polymeric pipe 100; and irradiating the polymeric pipe 100 with infrared radiation to crosslink the first crosslinkable polymer in the inner polymeric layer 105 and to crosslink the second crosslinkable polymer in the outer polymeric layer 104.

[0058] In select embodiments of the present disclosure, the first crosslinkable polymer may be polyethylene, polybutene, or a combination thereof.

[0059] In select embodiments of the present disclosure, the first crosslinking-reaction initiator may be identified by CAS # 215877-64-8, CAS # 154862-43-8, CAS # 1068-27-5, or a combination thereof.

[0060] In select embodiments of the present disclosure, the first crosslinking reaction initiator may be present in an amount between about 0.1 % and about 0.8 % on a mass basis relative to the total mass of the constituents of the inner polymeric layer 105. In select embodiments of the present disclosure, the first crosslinking reaction initiator may be present in an amount between about 0.4 % and about 0.6 % on a mass basis relative to the total mass of the constituents of the inner polymeric layer 105.

[0061] In select embodiments of the present disclosure, the second crosslinkable polymer may be polyethylene, polybutene, or a combination thereof.

[0062] In select embodiments where the inner polymeric layer 105 is comprised of (silane- or peroxide-) crosslinked polyethylene, the method of manufacturing the polymeric pipe 100 may further comprise treating the inner polymeric layer 105 with steam or hot water in order to get rid of the harmful chemicals or chemicals whose toxicology has not been fully investigated before the end use.

[0063] In select embodiments of the present disclosure, the second crosslinking-reaction initiator may be identified by CAS # 215877-64-8, CAS # 154862-43-8, CAS # 1068-27-5, or a combination thereof.

[0064] In select embodiments of the present disclosure, the second crosslinking reaction initiator may be present in an amount between about 0.1 % and about 0.8 % on a mass basis the total mass of the constituents of the outer polymeric layer 104. In particular, the second crosslinking reaction initiator is present in an amount between about 0.4 % and about 0.6 % on a mass basis relative to the total mass of the constituents of the outer polymeric layer 104.

[0065] In select embodiments of the present disclosure, the barrier layer 103 may further comprise a third crosslinkable polymer which is a copolymer of ethylene and vinyl alcohol.

[0066] In select embodiments of the present disclosure, the barrier layer 103 may further comprise a third crosslinking-reaction initiator which is a peroxide. The peroxide may be, by way of non-limiting example, identified by CAS # 215877- 64-8, CAS # 154862-43-8, CAS # 1068-27-5, or a combination thereof. [0067] In select embodiments of the present disclosure, the third crosslinking reaction initiator may be present in an amount between about 0.1 % and about 0.8 % on a mass basis relative to the total mass of the constituents of the barrier layer 103. In select embodiments of the present disclosure, the third crosslinking reaction initiator may be present in an amount between about 0.4 % and about 0.6 % on a mass basis relative to the total mass of the constituents of the barrier layer 103.

[0068] In select embodiments of the present disclosure, the outer polymeric layer 104 may comprise a polyethylene that is optimized for pressure/temperature resistance through crosslinking and that is substantially transparent to infrared radiation. Example 1

[0069] In this example, a polymeric pipe 100 is co-extruded using three batches of materials: batch A, batch B, and batch C.

[0070] Batch A, which is co-extruded as an inner polymeric layer, comprises a polyethylene such as BOREALIS ^® polyethylene HE-1878-E (BOREALIS is a registered trademark of BOREALIS A/S, Lyngby, Denmark), 0.5 % by weight of a peroxide such as T301 (CAS# 24748-23-0), 0.4 % by weight of an anti-oxidant identified by CAS # 65447-77-0, 0.15 % by weight of an antioxidant identified by CAS # 154862-43-8), and 0.4 % by weight of an anti-oxidant identified by CAS # 6683-19-8.

[0071] Batch B, which is co-extruded as a barrier layer, comprises a polymer such as a co-polymer of ethylene and vinyl alcohol and 0.5 % by weight of a peroxide such as T301 (CAS# 24748-23-0).

[0072] Batch C, which is co-extruded as an outer polymeric layer, comprises a polyethylene such as BOREALIS ^® polyethylene HE-1878-E, 0.4 % by weight of a peroxide such as DYBP (CAS # 1068-27-5), 0.24 % by weight of an anti-oxidant identified by CAS # 65447-77-0, 0.12 % by weight of an antioxidant identified by CAS # 154862-43-8), 0.24 % by weight of an anti-oxidant identified by CAS # 6683-19-8, and 0.2 % of UV-protectant such as titanium dioxide.

[0073] The inner polymeric layer, the barrier layer and the outer polymeric layer are co-extruded to produce a polymeric pipe with an outer diameter of about 15.90 mm and about 15.98 mm and a wall thickness of about 2 mm. The thickness of the inner polymeric layer is about 0.3 mm. The thickness of the barrier layer is about 0.075 mm, and the thickness of the outer polymeric layer is about 1 .625 mm.

Example 2

[0074] In this example, a polymeric pipe is co-extruded using five batches of materials: batch A, batch B, batch C, batch AH1 , and batch AH2. [0075] Batch A, which is co-extruded as an inner polymeric layer, comprises a polyethylene such as BOREALIS ^® polyethylene HE-1878-E, 0.5 % by weight of a peroxide such as T301 (CAS# 24748-23-0), 0.4 % by weight of an anti-oxidant identified by CAS # 65447-77-0, 0.15 % by weight of an anti-oxidant identified by CAS # 154862-43-8, and 0.4 % by weight of an anti-oxidant identified by CAS # 6683-19-8.

[0076] Batch B, which is co-extruded as a barrier layer, comprises a polymer such as a co-polymer of ethylene and polyvinyl alcohol and 0.5 % by weight of a peroxide such as T301 (CAS# 24748-23-0). [0077] Batch C, which is co-extruded as an outer polymeric layer, comprises a polyethylene such as BOREALIS ^® polyethylene HE-1878-E, 0.4 % by weight of a peroxide such as DYBP (CAS#1068-27-5), 0.24 % by weight of an anti-oxidant identified by CAS # 65447-77-0, 0.12 % of an anti-oxidant identified by CAS # 154862-43-8), 0.24 % by weight of an anti-oxidant identified by CAS # 6683-19-8, and 0.2 % of a UV-protectant such as titanium dioxide.

[0078] Batch AH1 , which is co-extruded as a first adhesive layer comprising ADMER 426 ^® between the inner polymeric layer and the barrier layer.

[0079] Batch AH2, which is co-extruded as a second adhesive layer comprising ADMER 426 ^® between the barrier layer and the outer polymeric layer. [0080] The layers are co-extruded to produce a polymeric pipe with an outer diameter of about 15.90 mm to 15.98 mm and a wall thickness of about 2 mm. The thickness of the inner polymeric layer is about 0.3 mm. The thickness of the barrier layer 103 is about 0.075 mm, the thickness of each of the first adhesive layer and the second adhesive layer is about 0.075 mm, and the thickness (C) of the outer polymeric layer (about 1 .475 mm) accounts for the remainder of the wall thickness of the polymeric pipe.

Example 3

[0081] The pipes extruded in Examples 1 and 2 are crosslinked using an apparatus and a process described in US patent No. 9,067,367 (the disclosure of which is incorporated herein in its entirety). The cooling gas and lamp intensity are adjusted to maintain a surface and middle wall temperature of about 200 °C and about 210 °C, respectively. The throughput speed is about 65 kg per hour, and the lamps are operated at about 65 % of the maximum rating.

[0082] Many obvious variations of the embodiments set out herein will suggest themselves to those skilled in the art in light of the present disclosure. Such obvious variations are within the full intended scope of the appended claims.