Light-weight, thermally-insulative perfluoroalkoxy (PFA) polymer foams, thermally-insulated tubings comprising the same, and processes for making and using them

Abstract

In various aspects, the disclosure provides perfluoroalkoxyalkane polymer foams of especially high void volume, especially low density, and / or especially low thermal conductivity, and processes for making the same. In one aspect, the disclosure provides a PFA polymer foam having a density that is no more than 35% of a density of a base resin. In another aspect, the disclosure provides a PFA polymer foam made by a process including causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam.

Description

LIGHT-WEIGHT, THERMALLY-INSULATIVE PERFLUOROALKOXY (PFA) POLYMER FOAMS, THERMALLY-INSULATED TUBINGS COMPRISING THE SAME, AND PROCESSES FOR MAKING AND USING THEMCross-Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application no. 63 / 687092, filed August 26, 2024, which is hereby incorporated herein by reference in its entirety.Background of the DisclosureField of the Disclosure

[0002] In various aspects, the disclosure provides perfluoroalkoxyalkane polymer foams of especially high void volume, especially low density, and / or especially low thermal conductivity, and processes for making the same. The disclosure also provides thermally- insulated tubings that include a layer of perfluoroalkoxyalkane polymer foam disposed about an inner tubular body. The materials and tubings can be flexible, resistant to a variety of fluids, and stable to both high and low continuous use temperatures, while providing good insulation. Such materials and tubings can be especially desirable in a variety of uses. For example, in various aspects of the disclosure, tubings described herein can be used in thermal management applications. But the materials and tubings described herein can find a variety of uses, especially applications in which a high degree of thermal insulation is advantageous.Technical Background

[0003] The area of thermal management is continuously evolving with the advent of new growth markets. The requirements are becoming more challenging with customers driving new specifications for tubings (including tubes, hoses and related products). For example, in the semiconductor industry, temperature requirements for tubings are shifting from, e.g., -40 °F on the low side to 450 °F on the high side to a range of -60 °F to 500 °F. In the future these temperature requirements are expected to broaden even further, e.g., from -90 °F to 550 °F.

[0004] State-of-the-art technologies for meeting such thermal requirements include materials such as mineral wool, ceramics and aerogels often provided in the form of tape- or blanket-shaped wrappings. These products can often suffer from limitations with respect to cost, manufacturing, tubing design and construction, handling and personnel safety. Moreover, insulation solutions that are suitable for high-temperature applications are often not suitable for low-temperature applications and vice versa. This is generally due toadditional performance requirements, e.g., related to flexibility, abrasion resistance, flex fatigue, and chemical resistance, which can require the use of different materials for different temperatures and applications.

[0005] There remains a need for improved thermally-insulating materials for tubings in a variety of applications.Summary of the Disclosure

[0006] One aspect of the disclosure is a PFA polymer foam made by a process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam.

[0007] Another aspect of the disclosure is a PFA polymer foam having a density that is no more than 35% of a density of a base resin.

[0008] Another aspect of the disclosure is a PFA polymer foam having a density of no more than 0.860 g / cm3.

[0009] Another aspect of the disclosure is a PFA polymer foam having a thermal conductivity that is no more than 25% of a thermal conductivity of the base resin.

[0010] Another aspect of the disclosure is a PFA polymer foam having thermal conductivity of no more than 0.050 W / m / K.

[0011] Another aspect of the disclosure is a PFA polymer foam made by a process of as described herein.

[0012] Another aspect of the disclosure is a layer of PFA polymer foam as described herein.

[0013] Another aspect of the disclosure is a thermally-insulated tubing comprising: an inner tubular structure comprising wall extending between a first end of the thermally-insulated tubing and an opposing second end of the thermally-insulated tubing , the wall defining an inner lumen extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubingalong a longitudinal axis of the thermally-insulated tubing, and the wall comprising one or more material layers; and a layer of PFA polymer foam as described herein surrounding the inner tubular structure.

[0014] Another aspect of the disclosure is a process for making a thermally-insulated tubing, the process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer as a layer on an inner tubular structure comprising wall extending between a first end of the thermally-insulated tubing and an opposing second end of the thermally-insulated tubing , the wall defining an inner lumen extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubing along a longitudinal axis of the thermally-insulated tubing, and the wall comprising one or more material layers, the layer of PFA polymer foam surrounding the inner tubular structure.

[0015] Other aspects of the disclosure will be apparent to the person of ordinary skill in the art based on this disclosure.Brief Description of the Drawings

[0016] FIG. 1 is a schematic cross-sectional view and a schematic perspective view of a tubing of the disclosure.

[0017] FIG. 2 is a graph showing transient extensional velocity for a variety of PFA polymers.Detailed Description

[0018] Polymer foams are widely used as thermal insulators and offer performance benefits over non-polymeric insulations such as mineral wool, ceramics, or aerogels. When considering mechanical properties such as flexibility, impact strength, flex fatigue in combination with chemical properties such as chemical purity, chemical resistance in combination with physical properties such as flame resistance along a wide continuous operating temperature range from -60 °F to 500 °F, the present inventors have noted that fluoropolymers such as poly(tetrafluoroethylene) (PTFE) and perfluoroalkoxyalkane (PFA,also known as “perfluoroalkoxy”) polymer are the materials of choice and provide the best performance.

[0019] While perfluoroalkoxy (PFA) polymer foams have been reported previously in U.S. Patents nos. 5912278 and 5885494, the process employed for manufacturing these PFA foams is a multi-step batch process requiring (a) first, processing the polymer into a part such as a sheet or a film, (b) second, placing the part in a pressurized chamber to dissolve CO2 gas therein, (c) and third, de-pressurizing the chamber to cause foaming by desolubilization of the gas. The present inventors have noted that such a process is not suitable for high-throughput manufacturing or for making parts with continuous long lengths such as wires, cables, tubes or hoses.

[0020] The present inventors note that foam extrusion is more suitable for continuous and high-throughput manufacturing. Foam extrusion can either be carried out using a physical foaming process in which a suitable physical foaming agent such as an inert gas is directly injected into the polymer melt inside the extruder, or a chemical foaming process which relies on a chemical reaction to occur inside the extruder to release gas that foams the polymer. Chemical foaming processes typically rely on the thermal decomposition of a chemical foaming agent added along with the polymer, with the heat of extrusion causing the thermal decomposition of the chemical foaming agent to release the gas.

[0021] PFA polymers are commonly foamed through a physical foaming process such as those described in U.S. Patents nos. 5610203, 6064008, 6139957, 8278366 and 8354461. The present inventors note, however, that the physical foaming process has important limitations in an industrial setting. For example, a physical foaming process requires complex extrusion lines and accurate control of feeding of physical foaming agents. Standard extrusion equipment and machinery cannot be efficiently retrofitted to produce foamed components using physical foaming. Another problem associated with using gas blowing agents is that the small port used to inject the gas blowing agent into the extruder often becomes blocked by the polymer material or by airborne dust and dirt. As a result, the extruder must be taken off-line and the port cleaned thereby preventing continuous operation. Intensive capital expenditure and increased operational costs are thus related to the implementation of physical foaming technologies. An additional problem in using physical blowing agents and in particular, nitrogen, for foaming fluorinated polymers is that the cell size of the resulting polymer insulation is too large for thin insulating layers (e.g., those 750 microns or less in thickness). As a result, there are breaks in the insulation thereby affecting the insulation properties of the fluorinated polymer layer.

[0022] The present inventors note that the cost benefits of chemical foaming vis-a-vis gas foaming of perfluoropolymers enable standard high temperature extruders to run foam perfluoropolymers without the need to port the barrel with a highly sophisticated gas valve.

[0023] However, the present inventors note that while the chemical foam extrusion process is significantly more desirable than the physical foam extrusion process because of reasons described in the above paragraph, one major limitation of the chemical foaming process is the low void fraction that has conventionally been achievable when foaming fluoropolymers, especially PFA polymers. One of the parameters that is used to measure the efficiency of a foaming process is the percent reduction in density of the unfoamed polymer. It is defined as the ratio of difference in density of polymer resin in the unfoamed state and the foamed state divided by the density in unfoamed state. This parameter is also sometimes referred to as the “void fraction” or the “foam rate.” For example, U.S. Patent no. 8278366 mentions a maximum achievable foaming rate of 60% from a chemical foaming process, but exemplifies a maximum foaming rate of only 41 % for fluorinated-ethylene- propylene (FEP) polymer in one of its results. The maximum foaming rate of PFA polymer is not discussed. Additionally, U.S. Patent no. 6139957 reports maximum void fraction from chemical foam process of 55% for FEP polymer but does not discuss the maximum void fraction obtained for PFA polymer.

[0024] The present inventors surmise that of the reasons that manufacturing PFA polymer foams is more challenging that other perfluoropolymers is the higher melting point of PFA polymers and consequently higher temperatures involved in the melt processing of PFA polymer. As such, conventional PFA polymer foams had relatively low void fractions and thus relatively low thermal resistivity. PFA polymer foams have conventionally been used for electrical insulation and good electrical properties, rather than for thermal insulation and resistance to heat transfer.

[0025] The present inventors have noted that conventional perfluoropolymer foams, being limited to void fractions less than about 60%, exhibit only minimal thermal insulation properties. For example, in situations where a hot process fluid is flowing through tubing at 500 F and the outermost surface temperature of the hose is desired to not exceed 80 F to conform to user safety standards, an insulation thickness of 10 millimeters or higher would be needed for a conventional PFA foam. Similarly, in situations where a cold process fluid is flowing through a hose or tube at -60 F with ambient conditions of 40% humidity at 80 F, and it is desired to prevent water drippage due to surface condensation, an insulation thickness of at least 20 mm is needed for a conventional PFA foam. Such high wall thicknesses severely restrict the envelope size of the tubing, thus making the tubing bulky.

[0026] To address these problems noted in the art, the present inventors provide perfluoroalkoxy (PFA) polymer foams that can be used in applications requiring performance at very high temperatures up to 500 °F or at very low temperature up to -60 °F. The present inventors achieve this providing high-performance PFA foams having higher void fraction (i.e. , higher density reduction) and lower thermal conductivity than conventional PFA polymer foams, so that the thermal resistance of the foam is maximized and the insulation thickness required at operating temperatures from -60 °F to 500 °F is minimized.

[0027] The present inventors provide processes enabling continuous manufacturing of such high performance PFA foams by using a chemical foam extrusion process. Notably, the present inventors have determined that using one or more chemical blowing agents that together release both CO2 and N2 as the foaming gases can generate PFA foams with significantly higher void fraction than conventional PFA foams. For example, the present inventors demonstrate herein that the void fraction generated by a combination of chemical blowing agents that release both CO2 and N2 gases is higher than that generated by utilizing a single chemical blowing agent releasing either only CO2 or only N2 gas. Such foams exhibit much lower thermal conductivities than previously reported and therefore suitable for highly demanding thermal insulation applications.

[0028] As used herein, the term “together release” both CO2 and N2 means that the one or more chemical blowing agents when considered together release both CO2 and N2. This does not require that CO2 and N2 be released concurrently. Rather, the gases can be released concurrently, or sequentially (e.g., with CO2 being released before N2, or vice versa).

[0029] Without being bound by any particular theory, the present inventors hypothesize that the release of one gas inside the polymer followed by a subsequent release of a second, different gas increases the total dissolved gas inside the polymer, and therefore enables a lower density of the polymer foam.

[0030] Thus, the present inventors have determined that foamed perfluoroalkoxyalkane polymer (PFA) can be especially useful as an insulating material, especially for tubings such as tubes, hoses and related products. The foamed PFA can provide good insulation properties over a wide range of operation temperatures. In various embodiments, foamed PFA materials and tubings including them can also meet additional desired performance criteria as well, e.g., one or more of high flexibility, high abrasion resistance, high chemical resistance, low mechanical fatigue and high flame resistance. The foamed PFA layer of the tubings of the disclosure can provide insulation for a hot or cold fluid being conducted through the tubing, e.g., to prevent undesired heat exchange with the atmosphere, and / or toprevent condensation or risk to users due to hot or cold tubing surfaces. The foamed PFA layer can likewise provide a measure of insulation when the tubing is disposed in a hot or cold environment.

[0031] The present inventors provide here perfluoroalkoxyalkane polymer foams of especially high void volume, especially low density, and / or especially low thermal conductivity, as well as thermally-insulated tubings that include a layer of perfluoroalkoxyalkane polymer foam disposed about an inner tubular body.

[0032] The present inventors have noted that PFA foams can be especially tolerant to a wide variety of temperatures, while retaining good mechanical and chemical properties, and thus that they can be especially useful for addressing the challenge of insulating tubings at very high temperatures up to 500 °F as well as very low temperatures down to -95 °F. The present inventors have determined that PFA foams can be provided at very low densities by using chemical foam extrusion techniques. Continuous extrusion of PFA insulation over an inner tubular body can eliminate the wrapping step presently used for insulation tapes. This can provide a number of advantages, including one or more of: (1 ) making the product construction simpler by replacing 3 or more layers with just one layer; (2) simplifying manufacturing and increases manufacturing throughput; (3) enhancing personnel safety during manufacturing; (4) providing ease of handling and installation; and (5) reducing manufacturing costs. Foamed PFA can also exhibit good thermal properties, like low thermal conductivity and low thermal effusivity, which can be important key properties in various thermal insulation applications. PFA foams can often be made with high flexibility, which can be important when routing and connecting tubings.

[0033] Accordingly, one aspect of the disclosure is a PFA polymer foam made by a process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam. The present inventors have found that use of one or more chemical foaming agents that together release both CO2 gas and N2 gas can provide PFA foams with advantageously high void fractions and advantageously low thermal conductivities.

[0034] Another aspect of the disclosure is a PFA polymer foam having a density that is no more than 35% of a density of a base resin. For example, in various embodiments, thePFA polymer foam has a density that is in the range of 10-35% of a density of a base resin, e.g., in the range of 13-35%, or 15-35%, or 18-35%, or 20-35%, or 22-35%, or 25-35%. The “base resin” is sample that is prepared identically to the PFA polymer foam but without the use of a foaming agent. Density can be measured using ASTM D-3574. In various such embodiments, the PFA polymer foam is made by a process as described herein.

[0035] The PFA polymer foams of the disclosure can have a variety of densities. For example, in various embodiments, the density of the PFA polymer foam is no more than 34% of a density of a base resin. In various embodiments, the density of the PFA polymer foam is in the range of 10-34% of a density of a base resin, e.g., in the range of 13-34%, or 15-34%, or 18-34%, or 20-34%, or 22-34%, or 25-34%. In various embodiments, the density of the PFA polymer foam is no more than 32% of a density of a base resin. In various embodiments, the density of the PFA polymer foam is in the range of 10-32% of a density of a base resin, e.g., in the range of 13-32%, or 15-32%, or 18-32%, or 20-32%, or 22-32%, or 25-32%. In various embodiments, the density of the PFA polymer foam is no more than 30% of a density of a base resin. In various embodiments, the density of the PFA polymer foam is in the range of 10-30% of a density of a base resin, e.g., 13-30%, or 15-30%, or 18- 30%, or 20-30%, or 22-30%, or 25-30%. In various embodiments, the density of the PFA polymer foam is no more than 28% of a density of a base resin. In various embodiments, the density of the PFA polymer foam is in the range of 10-28% of a density of a base resin, e.g., in the range of 13-28%, or 15-28%, or 18-28%, or 20-28 or 22-28%, or 25-28%.

[0036] The reductions in density as described herein are analogous to void volume and void fraction measurements, as would be understood by the person of ordinary skill in the art.

[0037] Another aspect of the disclosure is a PFA polymer foam having a density of no more than 0.860 g / cm3. In various such embodiments, the PFA polymer foam is made by a process as described herein.

[0038] For example, in various embodiments, the PFA polymer foam has a density of no more than 0.753 g / cm3, e.g., no more than 0.645 g / cm3. In various embodiments, the PFA polymer foam has a density of at least 0.430 g / cm3, e.g., at least 0.538 g / cm3.

[0039] In various embodiments, the PFA polymer foam has a density of at least 0.645 g / cm3, e.g., at least 0.753 g / cm3.

[0040] In various embodiments, the PFA polymer foam has a density in the range of 0.430-0.860 g / cm3, e.g., 0.430-0.753 g / cm3, or 0.430-0.645 g / cm3, or 0.538-0.860 g / cm3, or 0.538-753 g / cm3, or 0.538-0.645 g / cm3. In various embodiments, the PFA polymer foamhas a density in the range of 0.645-0.860 g / cm3, e.g., 0.645-0.753 g / cm3, or 0.753-0.860 g / cm3.

[0041] The present inventors have determined that chemical foam extrusion techniques can be used to provide foamed PFA with a variety of relatively high pore volumes and / or relatively low densities. The person of ordinary skill in the art, based on the present disclosure, can provide materials with a variety of pore volumes and / or densities to provide relatively higher or relatively lower degrees of thermal insulation, while ensuring other desirable properties are provided for a particular application.

[0042] Another aspect of the disclosure is a PFA polymer foam having a thermal conductivity that is no more than 25% of a thermal conductivity of the base resin, e.g., in the range of 10-25%, or 12-25%, or 15-25%. Thermal conductivity is measured using ASTM C- 518. In various such embodiments, the PFA polymer foam is made by a process as described herein.

[0043] In various embodiments, the thermal conductivity is no more than 22% of the thermal conductivity of the base resin, e.g., in the range of 10-22%, or 12-22%, or 15-22%. In various embodiments, the thermal conductivity is no more than 20% of the thermal conductivity of the base resin, e.g., in the range of 10-20%, or 12-20%, or 15-20%.

[0044] Another aspect of the disclosure is a PFA polymer foam having a thermal conductivity of no more than 0.050 W / m / K, e.g., no more than 0.045 W / m / K, or no more than 0.040 W / m / K. In various such embodiments, the PFA polymer foam is made by a process as described herein.

[0045] In various embodiments, the PFA polymer foam has a thermal conductivity no more than 0.035 W / m / K, e.g., no more than 0.030 W / m / K, or no more than 0.025 W / m / K.

[0046] In various embodiments, the PFA polymer foam has a thermal conductivity of at least 0.020 W / m / K, e.g., at least 0.025 W / m / K.

[0047] In various embodiments, the PFA polymer foam has a thermal conductivity in the range of 0.020-0.050 W / m / K, e.g., 0.020-0.045 W / m / K, or 0.020-0.040 W / m / K, or 0.025- 0.050 W / m / K, or 0.025-0.045 W / m / K, or 0.025-0.040 W / m / K. In various embodiments, the PFA polymer foam has a thermal conductivity in the range of 0.02-0.035 W / m / K, e.g., 0.020- 0.030 W / m / K, or 0.020-0.025 W / m / K, or 0.025-0.035 W / m / K, or 0.025-0.030 W / m / K.

[0048] The present inventors have also determined that chemical foam extrusion techniques can be used to provide foamed PFA with a variety of relatively low thermal conductivities. Such materials can be especially insulating, while still providing a variety ofdesirable properties with respect to mechanical stability and chemical resistance. The person of ordinary skill in the art, based on the present disclosure, can provide materials with a variety of thermal conductivities to relatively higher or relatively lower degrees of thermal insulation, while ensuring other desirable properties are provided for a particular application.

[0049] In various desirable embodiments as described herein, the PFA polymer foam is a closed-cell foam. As the person of ordinary skill in the art appreciates, closed-cell foams are especially thermally insulating. The present inventors have noted that closed-cell foams can be made by the chemical foaming processes as described herein.

[0050] The person of ordinary skill in the art is familiar with PFA polymers. Especially desirably PFA polymers are the copolymers of trifluoroethylene (TFE) and at least one perfluoro(alkyl vinyl ether) (PAVE) selected from perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether). Other desirable PFA polymers are copolymers of TFE with perfluoro(alkyl vinyl ether) in which the linear or branched alkyl group contains 1 to 5 carbon atoms. Preferred PAVE monomers include perfluoro(methyl vinyl .ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), perfluoro(propyl vinyl ether) (PPVE), and perfluoro(butyl vinyl ether) (PBVE). The copolymer can be made using multiple PAVE monomers, such as a copolymer of TFE and PMVE monomers (referred to as MFA) and TFE / perfluoro(methyl vinyl ether) / perfluoro(propyl vinyl ether) copolymer. TFE / PAVE copolymers desirably have at least about 2 wt % PAVE, including when the PAVE is PPVE or PEVE, and will typically contain about 2-15 wt % PAVE. When PAVE includes PMVE, the composition is typically about 0.5-13 wt % perfluoro(methyl vinyl ether) and about 0.5 to 3 wt % PPVE, the remainder to total 100 wt % being TFE.

[0051] In various embodiments, the PFA polymer is a copolymer of one or more of tetrafluoroethylene and hexafluoropropylene and one or more perfluorinated vinyl ethers (e.g., 1 ,1 ,2-trifluoro-2-(trifluoromethoxy)ethylene; 1 ,1 ,2-trifluoro-2- (pentafluoroethoxy)ethylene). In various embodiments, the PFA polymer is a copolymer of tetrafluoroethylene and one or more perfluorinated vinyl ethers (e.g., 1 , 1 ,2-trifluoro-2- (trifluoromethoxy)ethylene; 1 ,1 ,2-trifluoro-2-(pentafluoroethoxy)ethylene). In various embodiments, the PFA polymer is a copolymer of hexafluoropropylene and one or more perfluorinated vinyl ethers (e.g., 1 ,1 ,2-trifluoro-2-(trifluoromethoxy)ethylene; 1 , 1 , 2-triflu oro-2 - (pentafluoroethoxy)ethylene).

[0052] In various embodiments, the PFA polymer is made up of at least 90 wt% residues of perfluoroalkene and perfluoroalkoxy perfluoroalkene, e.g., at least 95 wt%, or at least 99 wt%.

[0053] It is well-known to those familiar with polymer extrusion that polymer melt viscosity plays an important role in establishing the flow characteristic of a polymer resin. For example, the lower the viscosity, the higher the flow rate in a melt extrusion process. For convenience and ease of comparison, the melt extrudability of PFA polymer material can be described in terms of melt flow rate (MFR) as measured using the Plastometer® according to ASTM D-1238-94a at conditions of 372° C and 5 kg load. The amount of polymer extruded from the Plastometer® in a measured amount of time is reported in units of g / 10 min in accordance with Table 2 of ASTM D 1238-94a.

[0054] As the person of ordinary skill in the art will appreciate, PFA polymer foams of the disclosure include one or more polymer resins (e.g., one or more PFA polymer resins, optionally together with minor quantities of additional polymer resin) that together make up the total resin content of the PFA polymer foam. In various embodiments as otherwise described herein, the MFR of the one or more polymer resins is in the range of 0.5-40 g / 10 min. For example, in various embodiments the MFR of the one or more polymer resins is in the range of 0.5-30 g / 10 min, or 0.5-20 g / 10 min. In various embodiments, the MFR of the one or more polymer resins is in the range of 1-40 g / 10 min, e.g., 1-30 g / 10 min, or 1-20 g / 10 min. In various embodiments, the MFR of the one or more polymer resins is in the range of 2-40 g / 10 min, e.g., 2-30 g / 10 min, or 2-20 g / 10 min. can vary from 2 to 30 g / 10 min. In various embodiments, the MFR of the one or more polymer resins is in the range of5- 40 g / 10 min, e.g., 5-30 g / 10 min, or 5-20 g / 10 min. can vary from 5 to 30 g / 10 min. In cases where a combination of resins is used, the MFR measurement is performed on a melt- blended sample of such resins.

[0055] The person of ordinary skill can select a desirable MFR of the resin(s). For example, an upper limit of desirable MFRs can be restricted by a poor melt stability and melt strength of an extrudate coming out of an extruder. And a lower limit of MFR can be restricted by high barrel pressure or die pressure of an extruder, or slow screw rotational speed resulting in low throughput, or melt instability such as sharkskin or extrudate distortion which can complicate provision of a consistent foamed extrudate with a smooth surface profile.

[0056] Moreover, the person of ordinary skill in the art understands that extensional melt viscosity and melt strength of the polymer play an important role in providing a stable foam structure. Out of the three primary phases involved in polymer foaming, namely cell nucleation, cell growth and cell stabilization, the extensional melt viscosity and melt strength strongly influence cell growth and cell stabilization. In various embodiments, a transient (time-dependent) extensional viscosity of the one or more polymer resins, as a melt, is in therange of 103to 106Pa-s at Hencky strain rates from 0.1 s'1up to 10 s'1and at melt temperatures from 320 °C up to 380 °C (i.e., throughout the space mapped by 0.1-10 s-1 and 320-380 °C), as measured by Sentmanat Extensional rheometer. The person of ordinary skill in the art appreciates how to use the Sentmanat Extensional rheometer in the measurement of such values.

[0057] It is also well known that melt strength of a polymer can be assessed by an increase in the slope of extensional viscosity, referred to as strain hardening, and the peak extensional viscosity before failure, as also seen in the transient extensional viscosity curve shown in the Examples below. It is important to note that while presence of strain hardening and a higher peak extensional viscosity can be an important measure of polymer foamability, the present inventors have found that PFA polymer resins exhibit good foamability and high density reductions even without strain hardening.

[0058] The person of ordinary skill in the art will appreciate that PFA polymers are well- known polymeric materials. The person of ordinary skill in the art, based on the present disclosure, can select an appropriate type of PFA polymer for use in the materials, structures and methods described herein, together with any other desirable resins.

[0059] The PFA polymer foams can include a variety of other components, as the person of ordinary skill in the art will appreciate.

[0060] For example, in various embodiments, the PFA polymer foam further includes a nucleating agent. Nucleating agents can be useful in providing gases evolved by chemical foaming agent(s) a center for nucleation to form bubbles.

[0061] In various embodiments, the nucleating agent is present in an amount in the range of 0.02-2 wt%, e.g., 0.02-1 wt%, or 0.02-0.5 wt%. In various embodiments, the nucleating agent is present in an amount in the range of 0.1-2 wt%, e.g., 0.1-1 wt%, or 0.1- 0.5 wt%.

[0062] The person of ordinary skill in the art will appreciate that a variety of nucleating agents can be suitable for use in the PFA foams as described herein. In various embodiments, the nucleating agent includes one or more of boron nitride; talc; metal oxide such as titanium dioxide, silicon dioxide, aluminum oxide and magnesium oxide; inorganic salts such as sodium carbonate, lithium carbonate, strontium carbonate, calcium carbonate, sodium sulfite, potassium pyrosulfate, barium nitrate, aluminum phosphate, sodium fluorosilicate, potassium sulfate, and the tetraborates of sodium, potassium, strontium and calcium; and free acids and salts of partially or totally fluorinated aliphatic sulfonic and phosphonic acids. However, the person of ordinary skill in the art will appreciate that avariety of other particulate materials can be suitable for use. Various examples of nucleating agents are described in U.S. Patents nos. 4764538, 5023279, 5610203, 5885494, and 8354461 , each of which is hereby incorporated by reference for its teachings related to nucleating agents.

[0063] In various embodiments, the PFA polymer foam includes one or more chemical foaming agents and / or one or more residues of the one or more chemical foaming agents.

[0064] The person of ordinary skill in the art will appreciate that a high proportion of the one or more chemical foaming agents is reacted in the foaming process. But in many cases, a detectable amount of the one or more foaming agents will remain. Moreover, many foaming agents will leave behind a residue, i.e., of a reaction product of the decomposition of the chemical foaming agent other than the CO2 or N2 gas. Accordingly, PFA polymer foams can have chemical foaming agent(s) or residue(s) thereof present, albeit in small amounts in some cases. Presence of such materials tends to show that the material was foamed chemically.

[0065] In various embodiments, the one or more chemical foaming agents (e.g., remaining in the PFA polymer foam or having a residue thereof remaining in the PFA polymer foam) includes one or more CO2 foaming agents. A wide variety of CO2 foaming agents are familiar to the person of ordinary skill in the art. For example, in various embodiments, the one or more CO2 foaming agents include one or more carbonates, e.g., magnesium carbonate or calcium carbonate.

[0066] In various embodiments, the one or more chemical foaming agents (e.g., remaining in the PFA polymer foam or having a residue thereof remaining in the PFA polymer foam) includes one or more N2 foaming agents. A wide variety of N2 foaming agents are familiar to the person of ordinary skill in the art. For example, in various embodiments, the one or more N2 foaming agents include a 5-phenyltetrazole compound, e.g., in the form of a salt, such as the barium salt of 5-phenyltetrazole. In various embodiments, the one or more N2 foaming agents include an azocarbonamide, e.g., azodicarbonamide (ADC). In various embodiments, the one or more N2 foaming agents include a semicarbazide, e.g., p-toluenesulfonyl semicarbazide. In various embodiments, the one or more N2 foaming agents include a hydrazide, e.g., p,p'- oxybis(benzene)sulfonylhydrazide, or p-toluenesulfonylhydrazide. In various embodiments, the one or more N2 foaming agents include a nitroso compound such as dinitrosopentamethylenetetramine. But a variety of other N2 blowing agents, such as various hydrazine compounds and azo compounds, can also be suitable for use.

[0067] Examples of chemical foaming agents are described in U.S. Patents nos.6064008 and 8278366, each of which is hereby incorporated herein by reference for its teachings related to foaming agents.

[0068] In various embodiments, the one or more chemical foaming agents (e.g., remaining in the PFA polymer foam or having a residue thereof remaining in the PFA polymer foam) are together adapted to release both CO2 gas and N2 gas. As noted above and as described in more detail below, the present inventors have found that providing both CO2 gas and N2 gas via one or more chemical foaming agents can provide lower density and lower thermal conductivity to a chemically-foamed PFA foam. However, even when one or more chemical blowing agents that together release both CO2 gas and N2 gas are used in the formation of a PFA polymer phone, in some cases the decomposition is so complete for a given chemical foaming agent that none remains in the PFA polymer foam and no residue remains in the PFA polymer foam. Accordingly, absence of chemical foaming agents and residues thereof does not necessarily demonstrate that chemical foaming agent(s) were not used in the processing of the material.

[0069] Of course, the person of ordinary skill in the art will appreciate that the PFA polymer foams of the disclosure can include any of a number of other components. For example, in various embodiments, the PFA polymer foam includes one or more of plasticizers, compatibilizers, anti-oxidants, UV stabilizers, radiopaque compounds, colorants (pigments or dyes), flow modifiers, impact modifiers, elastomers (such as in thermoplastic elastomers), cross-linked rubber (such as in thermoplastic vulcanizates), lubricants, releasing agents, coupling agents, cross-linking agents, dispersing agents, flame retardants, reinforcing metals, minerals, 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.).

[0070] But while the PFA polymer foams can include other components, it is desirable in many embodiments that the PFA polymer foam has a high content of PFA polymer. For example, in various embodiments, the PFA polymer foam has a PFA content of at least 80 wt%, e.g., at least 85 wt%. In various embodiments, the PFA polymer foam has a PFA content of at least 90 wt%, e.g., at least 95 wt%.

[0071] Another aspect of the disclosure provides a process for making a PFA polymer foam, for example, a PFA polymer foam as described above. Such a process includes causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the PFA polymer melt;allowing the PFA polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam.

[0072] The PFA polymer melt includes one or more polymer resins, e.g., one or more PFA polymers (i.e., one or more PFA polymer resins) optionally together with minor quantities of additional polymer resin, that together make up the total resin content of the PFA polymer melt. The one or more polymer resins (including one or more PFA polymer resins) can be described as above with respect to the PFA polymer foams of the disclosure.

[0073] As noted above, the process includes causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in the PFA polymer melt. The person of ordinary skill in the art understands how to use chemical foaming agents, and will select one or more foaming agents that together release both CO2 gas and N2 gas that are suitable for a given process. Typically, this will involve selection of one or more foaming agents that release both CO2 gas and one or more foaming agents that release N2 gas.

[0074] Thus, in various embodiments, the one or more chemical foaming agents include one or more CO2 foaming agents. A wide variety of CO2 foaming agents are familiar to the person of ordinary skill in the art. For example, in various embodiments, the one or more CO2 foaming agents include one or more carbonates, e.g., magnesium carbonate, or calcium carbonate.

[0075] In various embodiments, the one or more chemical foaming agents include one or more N2 foaming agents. A wide variety of N2 foaming agents are familiar to the person of ordinary skill in the art. For example, in various embodiments, the one or more N2 foaming agents include a 5-phenyltetrazole compound, e.g., in the form of a salt, such as the barium salt of 5-phenyltetrazole. In various embodiments, the one or more N2 foaming agents include an azocarbonamide, e.g., azodicarbonamide (ADC). In various embodiments, the one or more N2 foaming agents include a semicarbazide, e.g., p- toluenesulfonyl semicarbazide. In various embodiments, the one or more N2 foaming agents include a hydrazide, e.g., p,p'-oxybis(benzene)sulfonylhydrazide, or p- toluenesulfonylhydrazide. In various embodiments, the one or more N2 foaming agents include a nitroso compound such as dinitrosopentamethylenetetramine. But a variety of other N2 blowing agents, such as various hydrazine compounds and azo compounds, can also be suitable for use.

[0076] It in many embodiments, a first chemical foaming agent will release CO2 via an endothermic reaction, while a second chemical foaming agent will release N2 via an exothermic reaction. Of course, other arrangements are possible.

[0077] It can be desirable in some embodiments for each of a plurality of chemical foaming agents to release gas at a different temperature than another of the plurality of chemical foaming agents. In this way, gas can be released into the polymer melt at different temperatures corresponding to different times during processing. For example, as a polymer melt continues to be heated as it flows through an extruder, gas can be released therein at different times during the extrusion.

[0078] For example, in various embodiments, the one or more chemical foaming agents release CO2 at a substantially lower temperature (e.g. at least 10 °C lower, or at least 20 °C lower) than they release N2. In various embodiments, the one or more chemical foaming agents release CO2 substantially before (e.g., at least 2 seconds before, at least 10 seconds before) they release N2.

[0079] But other orders are possible. For example, in various embodiments, the one or more chemical foaming agents release N2 at a substantially lower temperature (e.g. at least 10 °C lower, or at least 20 °C lower) than they release CO2. In various embodiments, the one or more chemical foaming agents release N2 substantially before (e.g., at least 2 seconds before, at least 10 seconds before) they release CO2. in various embodiments, the one or more chemical foaming agents release CO2 at substantially the same temperature (e.g. within less than 10 °C, or within 5 °C) as they release N2. In various embodiments, the one or more chemical foaming agents release CO2 at substantially the same time (e.g., within less than 2 seconds, within 1 second) as they release N2.

[0080] The person of ordinary skill in the art can, based on the present disclosure, select an amount of gas release for a given process and a given desired product. For purposes of quantification in this disclosure, a chemical foaming agent is presumed to release all of the CO2 and / or N2 according to its understood gas release mechanism. For example, MgCC is understood to release one mole of CO2 per mol of MgCOs. In various embodiments, the one or more chemical foaming agents are provided in an amount to release at least 0.5 mL gas per gram of the one or more resins, e.g., 0.5-5 mL / g, or 0.5-3 mL / g, or 0.5-2 mL / g. In various embodiments, the one or more chemical foaming agents are provided in an amount to release at least 0.8 mL gas per gram of the one or more resins, e.g., 0.8-5 mL / g, or 0.8-3 mL / g, or 0.8-2 mL / g. In various embodiments, the one or more chemical foaming agents are provided in an amount to release at least 1 mL gas per gram of the one or more resins, e.g., 1-5 mL / g, or 1-3 mL / g, or 1-2 mL / g. In various embodiments, the one or more chemicalfoaming agents are provided in an amount to release at least 1 .2 mL gas per gram of the one or more resins, e.g., 1.2-5 mL / g, or 1.2-3 mL / g, or 1.2-2 mL / g.

[0081] It is desirable for the one or more chemical foaming agents to release substantial amounts of both CO2 and N2. In various embodiments, a ratio of CO2 released to N2 released is in the range of 5:1 to 1 :5. For example, in various embodiments, the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 1 :1 to 1 :5, e.g., 1 :1 to 1 :4, or 1 :1 to 1 :3, or 1 :1 to 1 :2. In various embodiments, the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 1 :1 .5 to 1 :5, e.g., 1 :1 .5 to 1 :4, or 1 :1 .5 to 1 :3, or 1 :1 .5 to 1 :2. In various embodiments, the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 1 :2 to 1 :5, e.g., 1 :2 to 1 :4, or 1 :2 to 1 :3. In various embodiments, the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 5:1 to 1 :1 , e.g., 4:1 to 1 :1 , or 3:1 to 1 :1 , or 2:1 to 1 :1 . In various embodiments, the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 the range of 5:1 to 1.5:1 , e.g., 4:1 to 1.5:1 , or 3:1 to 1.5:1 , or 2:1 to 1.5:1. In various embodiments, the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 the range of 5:1 to 2:1 , e.g., 4:1 to 2:1 , or 3:1 to 2:1 .

[0082] The present inventors note that a variety of melt-processing techniques are known for use chemical blowing agents. In various desirable embodiments, the process is a chemical foam extrusion of a mixture of the PFA polymer and the one or more chemical foaming agents.

[0083] As one example of such a process, PFA polymer resin (e.g., in powder, pellet or cube form) and desired additives (e.g., nucleating agent) can dry blended in desired proportions and melt extruded to obtain a compounded composition, then that compounded composition can be dry blended with one or more chemical foaming agents and formed as a PFA polymer foam via chemical foam extrusion.

[0084] A specific embodiment provides a first composition comprising a blend of PFA polymer resin, magnesium carbonate, calcium carbonate and wax as a powder blend mixed homogeneously; a second composition that is the blowing or foaming agent comprised of the first composition and additional PFA polymer resin which is heated to a selected melting point, blended and extruded to provide a pelletized master batch; a third composition including PFA polymer resin and talc as a nucleating agent which is compounded together via heating to a selected melting point and extruded into a pelletized form; and a fourth composition comprising the second composition and the third composition tumble blended inpelletized form for subsequent extrusion such that the pellets are placed in an extruder, heated to a selected melting point allowing for manufacture of blown or foamed insulative components. The third composition may be used exclusively as a nucleating and foam agent in a tumbled blend of third composition and PFA polymer resin. The person of ordinary skill in the art is familiar with the provision of masterbatches and can select parameters to avoid the premature activation of the chemical foaming agent(s).

[0085] The person of ordinary skill in the art is familiar with a variety of chemical foam extrusion processes, including those in U.S. Patents Nos. 5610203, 6064008 and 8278366, each of which is hereby incorporated herein by reference in its entirety for such teachings.

[0086] In another aspect, the disclosure provides a layer of PFA polymer foam, the PFA polymer foam of the layer being as described herein. As described herein, the present inventors have determined that a low density foam can be provided through a chemical foam extrusion process. Layers of PFA polymer foams as described herein can be used to provide thermal insulation to a variety of systems.

[0087] In another aspect, the disclosure provides a thermally-insulated tubing comprising: an inner tubular structure comprising wall extending between a first end of the thermally-insulated tubing and an opposing second end of the thermally-insulated tubing , the wall defining an inner lumen extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubing along a longitudinal axis of the thermally-insulated tubing, and the wall comprising one or more material layers; and a layer of PFA polymer foam as described herein surrounding the inner tubular structure.

[0088] Such tubings can be made, for example, by extruding a layer of PFA polymer foam onto an inner tubular structure, either by extrusion onto a pre-existing inner tubular structure, or by co-extrusion of the PFA polymer foam together with the inner tubular structure.

[0089] In this disclosure, the term “tubing” relates to any flexible hollow annular structure suitable for conveying a fluid. Accordingly, it encompasses not only structures that may be referred to in the art as tubings, but also structures that may be referred to in the art as hoses. Both reinforced and unreinforced structures are contemplated.

[0090] Various foam-clad tubing structures are described, for example, in U.S. Patent Application Publication no. 20220090726, which is hereby incorporated herein by referencein its entirety for such teachings. The person of ordinary skill will adapt the structures using the PFA polymer foams and processes described herein; such thermally-insulated tubings are specifically contemplated within the scope of the present disclosure.

[0091] In another aspect, the disclosure provides a process for making a thermally- insulated tubing, the process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam as a layer on an inner tubular structure comprising wall extending between a first end of the thermally-insulated tubing and an opposing second end of the thermally- insulated tubing , the wall defining an inner lumen extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubing along a longitudinal axis of the thermally-insulated tubing, and the wall comprising one or more material layers, the layer of PFA polymer foam surrounding the inner tubular structure.

[0092] Such processes cay can be made, for example, by extruding a layer of PFA polymer foam onto an inner tubular structure, either by extrusion onto a pre-existing inner tubular structure, or by co-extrusion of the PFA polymer foam together with the inner tubular structure. The present inventors have determined that, with appropriate selection of polymer chemical structure and chemical foaming agent composition along with tuning of processing conditions, the chemical foam extrusion process can result in a low-density PFA foam. The layer can be extruded as an annulus onto an inner tubular structure, or co-extruded with an inner tubular structure, to form thermally-insulated tubings of the disclosure.

[0093] An example of such a tubing is shown in both cross-sectional and perspective view in FIG. 1. Here, thermally-insulated tubing 100 includes an inner tubular structure 110 having a wall 112 extending between a first end 102 of the thermally-insulated tubing and an opposing second end 104 of the thermally-insulated tubing. The wall defines an inner lumen 106 extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubing along a longitudinal axis 108 of the thermally-insulated tubing. The wall includes one or more (here, one) material layers 113. The tubing also includes a layer of PFA polymer foam 120 surrounding the inner tubular structure 110.

[0094] Another aspect of the disclosure provides a method for conducting a fluid (e.g., a liquid), the method comprising providing the fluid to the first end of the thermally-insulated tubing as described herein; and conducting the liquid to the second end of the thermally- insulated tubing. The thermally-insulated tubings find especial use in conducting liquids in hot or cold environments, or, alternatively, conducting hot or cold liquids. Accordingly, in various such embodiments, the thermally-insulated tubing is disposed in an environment having a temperature in the range of 200-550 °F (93.3-287.8 °C), or -90-0 °F (-67.8-0 °C). In various such embodiments, the fluid has a temperature in the range of 200-550 °F (93.3- 287.8 °C), or -90-0 °F (-67.8-0 °C).

[0095] Various aspects and embodiments of the disclosure are illustrated by the following Examples.

[0096] Five examples of PFA polymers were used in a variety of chemical foam extrusion experiments. Particular extrusion conditions are provided in the Tables below, in which Table 1 illustrates extrusions performed using only single carbonate chemical foaming agent, and Table 2 illustrates extrusions performed using a combination of carbonate and tetrazole chemical foaming agents that together release both CO2 and N2. Various PFA polymer foam properties are reported.TABLE 1x indicates presence of chemical blowing agent in an unreported amount. y indicates data not available.Gas release data provided in relative amounts, with “2n” being twice as much as “1n” and “3n” being three times as much, etc.TABLE 2Relative AmountSize (microns)Gas release data provided in relative amounts, with “2n” being twice as much as n” and“3n” being three times as much, etc.

[0097] It is shown in Table 1 that increases in the amount gas that is released by chemical foaming agent do not necessarily correlate with a decrease in density or an increase in density reduction. But Table 2 shows that using combinations of chemical foaming agents that release both CO2 and N2 can provide very low density foam.

[0098] Exemplary extensional viscosity curves are shown for PFA polymers PFA1-5 in FIG. 2 at a melt temperature of 320 °C and at a Hencky strain rate of 10 s'1. For example, in FIG. 2, PFA2, PFA3 and PFA6 polymers exhibit strain hardening at 320 °C but PFA4 and PFA5 polymers do not. Of course, it is possible that PFA4 and PFA5 polymers exhibit strain hardening at temperatures higher than 320°C. Similarly, it is possible that PFA2, PFA3 and PFA6 polymers do not exhibit strain hardening at temperatures higher than 320°C or exhibit strain hardening to a lesser or higher degree. Regardless of the strain hardening, it is believed that the extensional viscosity range described herein provides a sufficient condition for PFA polymers to be foamed under the present invention.

[0099] Various aspects of the disclosure are illustrated by the following enumerated embodiments are described below, which can be combined in any number and in any combination that is not technically or logically inconsistent.Embodiment 1 . A PFA polymer foam made by a process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam.Embodiment 2. A PFA polymer foam having a density that is no more than 35% of a density of a base resin.Embodiment 3. The PFA polymer foam of Embodiment 2, made by the process ofEmbodiment 1 .Embodiment 4. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is in the range of 10-35% of a base resin, e.g., in the range of 13-35%, or 15-35%, or 18-35%, or 20-35%, or 22-35%.Embodiment 5. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is no more than 34% of a density of a base resin.Embodiment 6. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is in the range of 10-34% of a density of a base resin, e.g., in the range of 13-34%, or 15-34%, or 18-34%, or 20-34%, or 22-34%, or 25-34%.Embodiment 7. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is no more than 32% of a density of a base resin.Embodiment 8. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is in the range of 10-32% of a density of a base resin, e.g., in the range of 13-32%, or 15-32%, or 18-32%, or 20-32%, or 22-32%, or 25-32%.Embodiment 9. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is no more than 30% of a density of a base resin.Embodiment 10. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is in the range of 10-30% of a density of a base resin, e.g., 13-30%, or 15-30%, or 18-30%, or 20-30%, or 22-30%, or 25-30%.Embodiment 11. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is no more than 28% of a density of a base resin.Embodiment 12. The PFA polymer foam of Embodiment 2 or Embodiment 3, wherein the density of the PFA polymer foam is in the range of 10-28% of a density of a base resin, e.g., in the range of 13-28%, or 15-28%, or 18-28%, or 20-28 or 22-28%, or 25-28%.Embodiment 13. The PFA polymer foam of any of Embodiments 1-12, wherein the PFA polymer foam has a density of no more than 0.860 g / cm3.Embodiment 14. A PFA polymer foam having a density of no more than 0.860 g / cm3.Embodiment 15. The PFA polymer foam of Embodiment 14, made by the process ofEmbodiment 1 .Embodiment 16. The PFA polymer foam of Embodiment 14 or Embodiment 15, having a density of no more than 0.753 g / cm3, e.g., no more than 0.645 g / cm3.Embodiment 17. The PFA polymer foam of Embodiment 14 or Embodiment 15, having a density of at least 0.430 g / cm3, e.g., at least 0.538 g / cm3.Embodiment 18. The PFA polymer foam of Embodiment 14 or Embodiment 15, having a density of at least 0.645 g / cm3, e.g., at least 0.753 g / cm3.Embodiment 19. The PFA polymer foam of Embodiment 14 or Embodiment 15, having a density in the range of 0.430-0.860 g / cm3, e.g., 0.430-0.753 g / cm3, or 0.430-0.645 g / cm3, or 0.538-0.860 g / cm3, or 0.538-753 g / cm3, or 0.538-0.645 g / cm3.Embodiment 20. The PFA polymer foam of Embodiment 14 or Embodiment 15, having a density in the range of 0.645-0.860 g / cm3, e.g., 0.645-0.753 g / cm3, or 0.753-0.860 g / cm3.Embodiment 21. The PFA polymer foam of any of Embodiments 1-20, wherein the PFA polymer foam has a thermal conductivity that is no more than 25% of a thermal conductivity of the base resin, e.g., in the range of 10-25%, or 12-25%, or 15-25%.Embodiment 22. A PFA polymer foam having a thermal conductivity that is no more than 25% of a thermal conductivity of the base resin, e.g., in the range of 10-25%, or 12- 25%, or 15-25%.Embodiment 23. The PFA polymer foam of Embodiment 22, made by the process ofEmbodiment 1 .Embodiment 24. The PFA polymer foam of any of Embodiments 21-23, wherein the thermal conductivity is no more than 22% of the thermal conductivity of the base resin, e.g., in the range of 10-22%, or 12-22%, or 15-22%.Embodiment 25. The PFA polymer foam of any of Embodiments 21-23, wherein the thermal conductivity is no more than 20% of the thermal conductivity of the base resin, e.g., in the range of 10-20%, or 12-20%, or 15-20%.Embodiment 26. The PFA polymer foam of any of Embodiments 1-25, wherein the PFA foam has a thermal conductivity of no more than 0.050 W / m / K, e.g., no more than 0.045 W / m / K, or no more than 0.040 W / m / K.Embodiment 27. A PFA polymer foam having thermal conductivity of no more than 0.050 W / m / K, e.g., no more than 0.045 W / m / K, or no more than 0.040 W / m / K.Embodiment 28. The PFA polymer foam of Embodiment 27, made by the process of Embodiment 1 .Embodiment 29. The PFA polymer foam of any of Embodiments 1 -28, having a thermal conductivity of no more than 0.035 W / m / K.Embodiment 30. The PFA polymer foam of any of Embodiments 1-28, having a thermal conductivity of no more than 0.030 W / m / K.Embodiment 31. The PFA polymer foam of any of Embodiments 1-28, having a thermal conductivity of no more than 0.025 W / m / K.Embodiment 32. The PFA polymer foam of any of Embodiments 1-29, having a thermal conductivity of at least 0.020 W / m / K.Embodiment 33. The PFA polymer foam of any of Embodiments 1-29, having a thermal conductivity of at least 0.025 W / m / K.Embodiment 34. The PFA polymer foam of any of Embodiments 1-28, having a thermal conductivity in the range of 0.020-0.050 W / m / K, e.g., 0.020-0.045 W / m / K, or 0.020-0.040 W / m / K, or 0.025-0.050 W / m / K, or 0.025-0.045 W / m / K, or 0.025-0.040 W / m / K.Embodiment 35. The PFA polymer foam of any of Embodiments 1-28, having a thermal conductivity in the range of 0.02-0.035 W / m / K, e.g., 0.020-0.030 W / m / K, or 0.020-0.025 W / m / K, or 0.025-0.035 W / m / K, or 0.025-0.030 W / m / K.Embodiment 36. The PFA polymer foam of any of Embodiments 1 -35, wherein the PFA polymer foam is a closed-cell foam.Embodiment 37. The PFA polymer foam of any of Embodiments 1 -36, wherein one or more PFA polymers of the PFA polymer foam is a copolymer of one or more of tetrafluoroethylene and hexafluoropropylene and one or more perfluorinated vinyl ethers (e.g., 1 ,1 ,2-trifluoro-2-(trifluoromethoxy)ethylene; 1 ,1 ,2-trifluoro-2- (pentafluoroethoxy)ethylene).Embodiment 38. The PFA polymer foam of any of Embodiments 1 -36, wherein one or more PFA polymers of the PFA polymer foam is a copolymer of tetrafluoroethylene and one or more perfluorinated vinyl ethers (e.g., 1 ,1 ,2-trifluoro-2-(trifluoromethoxy)ethylene; 1 ,1 ,2- trifluoro-2-(pentafluoroethoxy)ethylene).Embodiment 39. The PFA polymer foam of any of Embodiments 1 -36, wherein one or more PFA polymers of the PFA polymer foam is a copolymer of hexafluoropropylene and one or more perfluorinated vinyl ethers (e.g., 1 ,1 ,2-trifluoro-2-(trifluoromethoxy)ethylene; 1 ,1 ,2-trifluoro-2-(pentafluoroethoxy)ethylene).Embodiment 40. The PFA polymer foam of any of Embodiments 1 -36, wherein one or more PFA polymers of the PFA polymer foam is made up of at least 90 wt% residues of perfluoroalkene and perfluoroalkoxy perfluoroalkene, e.g., at least 95 wt%, or at least 99 wt%.Embodiment 41. The PFA polymer foam of any of Embodiments 1-40, wherein the PFA polymer foam comprises one or more polymer resins that provide a total resin content of the PFA polymer foam, the one or more polymer resins having an MFR in the range of 0.5-40 g / 10 min.Embodiment 42. The PFA polymer foam of Embodiment 41 , wherein the one or more polymer resins have an MFR in the range of 0.5-30 g / 10 min, e.g., 0.5-20 g / 10 min.Embodiment 43. The PFA polymer foam of Embodiment 41 , wherein the one or more polymer resins have an MFR in the range of 1-40 g / 10 min, e.g., 1-30 g / 10 min, or 1-20 g / 10 min.Embodiment 44. The PFA polymer foam of Embodiment 41 , wherein the one or more polymer resins have an MFR in the range of 2-40 g / 10 min, e.g., 2-30 g / 10 min, or 2-20 g / 10 min. can vary from 2 to 30 g / 10 min.Embodiment 45. The PFA polymer foam of Embodiment 41 , wherein the one or more polymer resins have an MFR in the range of 5-40 g / 10 min, e.g., 5-30 g / 10 min, or 5-20 g / 10 min. can vary from 5 to 30 g / 10 min.Embodiment 46. The PFA polymer foam of Embodiment 41 , wherein the one or more polymer resins have, as a melt, a transient (time-dependent) extensional viscosity in the range of 103to 106Pa-s at Hencky strain rates from 0.1 s'1up to 10 s'1and at melt temperatures from 320°C up to 380°C, as measured by Sentmanat Extensional rheometer.Embodiment 47. The PFA polymer foam of any of Embodiments 1 -46, further comprising a nucleating agent.Embodiment 48. The PFA polymer foam of Embodiment 47, wherein the nucleating agent is present in an amount in the range of 0.02-2 wt%, e.g., 0.02-1 wt%, or 0.02-0.5 wt%.Embodiment 49. The PFA polymer foam of Embodiment 47, wherein the nucleating agent is present in an amount in the range of 0.1-2 wt%, e.g., 0.1-1 wt%, or 0.1-0.5 wt%.Embodiment 50. The PFA polymer foam of any of Embodiments 47-49, wherein the nucleating agent includes one or more of boron nitride; talc; metal oxide such as titanium dioxide, silicon dioxide, aluminum oxide and magnesium oxide; inorganic salts such as sodium carbonate, lithium carbonate, strontium carbonate, calcium carbonate, sodium sulfite, potassium pyrosulfate, barium nitrate, aluminum phosphate, sodium fluorosilicate, potassium sulfate, and the tetraborates of sodium, potassium, strontium and calcium; and free acids and salts of partially or totally fluorinated aliphatic sulfonic and phosphonic acids.Embodiment 51. The PFA polymer foam of any of Embodiments 1 -50, further comprising one or more chemical foaming agents and / or one or more residues of the one or more chemical foaming agents.Embodiment 52. The PFA polymer foam of Embodiment 51 , wherein the one or more chemical foaming agents includes one or more CO2 foaming agents.Embodiment 53. The PFA polymer foam of Embodiment 51 , wherein the one or more CO2 foaming agents include one or more carbonates.Embodiment 54. The PFA polymer foam of Embodiment 51 , wherein the one or more CO2 foaming agents include magnesium carbonate, or calcium carbonate.Embodiment 55. The PFA polymer foam of any of Embodiments 51-54, wherein the one or more chemical foaming agents includes one or more N2 foaming agents.Embodiment 56. The PFA polymer foam of Embodiment 55, wherein the one or more N2 foaming agents comprise a 5-phenyltetrazole compound, e.g., in the form of a salt, such as the barium salt of 5-phenyltetrazole.Embodiment 57. The PFA polymer foam of Embodiment 55 or Embodiment 56, wherein the one or more N2 foaming agents comprise an azocarbonamide, e.g., azodicarbonamide (ADC).Embodiment 58. The PFA polymer foam of any of Embodiments 55-57, wherein the one or more N2 foaming agents comprise a semicarbazide, e.g., p-toluenesulfonyl semicarbazide.Embodiment 59.' The PFA polymer foam of any of Embodiments 55-58, wherein the one or more N2 foaming agents comprise a hydrazide, e.g., p,p’- oxybis(benzene)sulfonylhydrazide, or p-toluenesulfonylhydrazide.Embodiment 60. The PFA polymer foam of any of Embodiments 55-59, wherein the one or more N2 foaming agents comprise a nitroso compound such as dinitrosopentamethylenetetramine.Embodiment 61. The PFA polymer foam of any of Embodiments 55-60, wherein the one or more N2 foaming agents comprise a hydrazine compound or an azo compound.Embodiment 62. The PFA polymer foam of any of Embodiments 45-61 , wherein the one or more chemical foaming agents are together adapted to release both CO2 gas and N2 gas.Embodiment 63. The PFA polymer foam of any of Embodiments 1-62, wherein the PFA polymer foam further comprises one or more of plasticizers, compatibilizers, anti-oxidants, UV stabilizers, radiopaque compounds, colorants (pigments or dyes), flow modifiers, impact modifiers, elastomers (such as in thermoplastic elastomers), cross-linked rubber (such as in thermoplastic vulcanizates), lubricants, releasing agents, coupling agents, cross-linking agents, dispersing agents, flame retardants, reinforcing metals, minerals, 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.).Embodiment 64. The PFA polymer foam of any of Embodiments 1-63, wherein the PFA polymer foam has a PFA content of at least 80 wt%, e.g., at least 85 wt%. IEmbodiment 65. The PFA polymer foam of any of Embodiments 1-63, wherein the PFA polymer foam has a PFA content of at least 90 wt%, e.g., at least 95 wt%.Embodiment 66. A process for making a PFA polymer foam (e.g., a PFA polymer foam according to any of Embodiments 1-67), the process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam.Embodiment 67. The process of Embodiment 66, wherein the PFA polymer melt includes one or more polymer resins (e.g., one or more PFA polymers, optionally together with minor quantities of additional polymer resin) that together make up the total resin content of the PFA polymer melt, and wherein the one or more polymer resins, and wherein the one or more polymer resins are as described in any of Embodiments 37-46.Embodiment 68. The process of Embodiment 66 or Embodiment 67, wherein the one or more chemical foaming agents includes one or more CO2 foaming agents.Embodiment 69. The process of Embodiment 68, wherein the one or more CO2 foaming agents include one or more carbonatesEmbodiment 70. The process of Embodiment 68, wherein the one or more CO2 foaming agents include magnesium carbonate or calcium carbonateEmbodiment 71 . The process of any of Embodiments 66-70, wherein the one or more chemical foaming agents includes one or more N2 foaming agents.Embodiment 72. The process of Embodiment 71 , wherein the one or more N2 foaming agents comprise a 5-phenyltetrazole compound, e.g., in the form of a salt, such as the barium salt of 5-phenyltetrazole.Embodiment 73. The process of Embodiment 71 or Embodiment 72, wherein the one or more N2 foaming agents comprise an azocarbonamide, e.g., azodicarbonamide (ADC).Embodiment 74. The process of any of Embodiments 71-73, wherein the one or more N2 foaming agents comprise a semicarbazide, e.g., p-toluenesulfonyl semicarbazide.Embodiment 75.' The process of any of Embodiments 71-74, wherein the one or more N2 foaming agents comprise a hydrazide, e.g., p,p’-oxybis(benzene)sulfonylhydrazide, or p- toluenesulfonylhydrazide.Embodiment 76. The process of any of Embodiments 71-75, wherein the one or more N2 foaming agents comprise a nitroso compound such as dinitrosopentamethylenetetramine.Embodiment 77. The process of any of Embodiments 71-76, wherein the one or more N2 foaming agents comprise a hydrazine compound or an azo compound.Embodiment 78. The process of any of Embodiments 66-77, wherein a first chemical foaming agent releases CO2 via an endothermic reaction, while a second chemical foaming agent releases N2 via an exothermic reaction.Embodiment 79. The process of any of Embodiments 66-78, wherein each of a plurality of chemical foaming agents release gas at a different temperature than another of the plurality of chemical foaming agents.Embodiment 80. The process of any of Embodiments 66-78, wherein the one or more chemical foaming agents release CO2 at a substantially lower temperature (e.g. at least 10 °C lower, or at least 20 °C lower) than they release N2.Embodiment 81 . The process of any of Embodiments 66-78 and 80, wherein the one or more chemical foaming agents release CO2 substantially before (e.g., at least 2 seconds before, at least 10 seconds before) they release N2.Embodiment 82. The process of any of Embodiments 66-78, wherein the one or more chemical foaming agents release N2 at a substantially lower temperature (e.g. at least 10 °C lower, or at least 20 °C lower) than they release CO2.Embodiment 83. The process of any of Embodiments 66-78 and 82, wherein the one or more chemical foaming agents release N2 substantially before (e.g., at least 2 seconds before, at least 10 seconds before) they release CO2.Embodiment 84. The process of any of Embodiments 66-78, wherein the one or more chemical foaming agents release CO2 at substantially the same temperature (e.g. within less than 10 °C, or within 5 °C) as they release N2.Embodiment 85. The process of any of Embodiments 66-78 and 84, wherein the one or more chemical foaming agents release CO2 at substantially the same time (e.g., within less than 2 seconds, within 1 second) as they release N2.Embodiment 86. The process of any of Embodiments 66-85, wherein the one or more chemical foaming agents are provided in an amount to release at least 0.5 mL gas per gram of the one or more resins, e.g., 0.5-5 mL / g, or 0.5-3 mL / g, or 0.5-2 mL / g.Embodiment 87. The process of any of Embodiments 66-85, wherein the one or more chemical foaming agents are provided in an amount to release at least 0.8 mL gas per gram of the one or more resins, e.g., 0.8-5 mL / g, or 0.8-3 mL / g, or 0.8-2 mL / g.Embodiment 88. The process of any of Embodiments 66-85, wherein the one or more chemical foaming agents are provided in an amount to release at least 1 mL gas per gram of the one or more resins, e.g., 1-5 mL / g, or 1-3 mL / g, or 1-2 mL / g.Embodiment 89. The process of any of Embodiments 66-85, wherein the one or more chemical foaming agents are provided in an amount to release at least 1.2 mL gas per gram of the one or more resins, e.g., 1 .2-5 mL / g, or 1 .2-3 mL / g, or 1 .2-2 mL / g.Embodiment 90. The process of any of Embodiments 66-89, wherein the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 5:1 to 1 :5.Embodiment 91. The process of any of Embodiments 66-89, wherein the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 1 :1 to 1 :5, e.g., 1 :1 to 1 :4, or 1 :1 to 1 :3, or 1 :1 to 1 :2.Embodiment 92. The process of any of Embodiments 66-89, wherein the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 1 :1 .5 to 1 :5, e.g., 1 :1.5 to 1 :4, or 1 :1 .5 to 1 :3, or 1 :1 .5 to 1 :2.Embodiment 93. The process of any of Embodiments 66-89, wherein the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 1 :2 to 1 :5, e.g., 1 :2 to 1 :4, or 1 :2 to 1 :3.Embodiment 94. The process of any of Embodiments 66-89, wherein the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 5:1 to 1 :1 , e.g., 4:1 to 1 :1 , or 3:1 to 1 :1 , or 2:1 to 1 :1.Embodiment 95. The process of any of Embodiments 66-89, wherein the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 5:1 to 1.5:1 , e.g., 4:1 to 1.5:1 , or 3:1 to 1.5:1 , or 2:1 to 1.5:1.Embodiment 96. The process of any of Embodiments 66-89, wherein the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 5:1 to 2:1 , e.g., 4:1 to 2:1 , or 3:1 to 2:1 .Embodiment 97. The process of any of Embodiments 66-96, wherein the process comprises performing chemical foam extrusion on a mixture of the PFA and the one or more chemical foaming agents.Embodiment 98. The process of any of Embodiments 66-97, wherein the PFA polymer foam is a PFA polymer foam according to any of 1-65.Embodiment 99. A PFA polymer foam made by a process of any of Embodiments 66-97.Embodiment 99. A layer of a PFA polymer foam according to any of Embodiments 1-65.Embodiment 100. A thermally-insulated tubing comprising: an inner tubular structure comprising wall extending between a first end of the thermally-insulated tubing and an opposing second end of the thermally-insulated tubing , the wall defining an inner lumen extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubing along a longitudinal axis of the thermally-insulated tubing, and the wall comprising one or more material layers; and a layer of PFA polymer foam according to any of Embodiments 1-65 and 99 surrounding the inner tubular structure.Embodiment 101. A process for making a thermally-insulated tubing, the process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer as a layer on an inner tubular structure comprising wall extending between a first end of the thermally-insulated tubing and an opposing second end of the thermally-insulated tubing , the wall defining an inner lumen extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubing along a longitudinal axis of the thermally-insulated tubing, and the wall comprising one or more material layers, the layer of PFA polymer foam surrounding the inner tubular structure.Embodiment 102. The process of Embodiment 101 , wherein the PFA polymer foam is according to any of Embodiments 1-65.Embodiment 103. The process of Embodiment 101 or Embodiment 102, wherein the thermally insulated tubing is according to Embodiment 100.Embodiment 104. The process of any of Embodiments 101-103, wherein the layer ofPFA polymer foam is extruded as an annular layer.Embodiment 105. The process of claim 104, wherein the layer of PFA polymer foam is extruded onto an inner tubular structure (e.g., to form a thermally-insulated tubing of Embodiment 100)Embodiment 106. The process of claim 104, wherein the layer of PFA polymer foam is co-extruded with and onto an inner tubular structure (e.g., to form a thermally-insulated tubing of Embodiment 100).Embodiment 107. A method for conducting a fluid, the method comprising providing a fluid (e.g., a liquid) to the first end of the thermally-insulated tubing of Embodiment 100; and conducting the fluid to the second end of the thermally-insulated tubing.Embodiment 108. The method according to Embodiment 107, wherein the thermally- insulated tubing is disposed in an environment having a temperature in the range of 200- 550 °F, or -90-0 °F.Embodiment 109. The method according to Embodiment 107, wherein the fluid has a temperature in the range of 200-550 °F, or -90-0 °F.

Claims

What is claimed is1. A PFA polymer foam having a closed-cell structure; a density that is no more than 35% of a density of a base resin; a thermal conductivity that is no more than 25% of a thermal conductivity of the base resin.

2. A PFA polymer foam according to claim 1 made by a process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam.

3. The PFA polymer foam of claim 1 or claim 2, wherein the density of the PFA polymer foam is in the range of 10-30% of a density of a base resin.

4. The PFA polymer foam of claim 1 or claim 2, wherein the PFA polymer foam has a density of no more than 0.860 g / cm3.

5. The PFA polymer foam of claim 1 or claim 2, wherein the PFA foam has a thermal conductivity of no more than 0.050 W / m / K.

6. The PFA polymer foam of claim 1 or claim 2, wherein one or more PFA polymers of the PFA polymer foam is a copolymer of one or more of tetrafluoroethylene and hexafluoropropylene and one or more perfluorinated vinyl ethers (e.g., 1 , 1 ,2-triflu oro-2 - (trifluoromethoxy)ethylene; 1 ,1 ,2-trifluoro-2-(pentafluoroethoxy)ethylene).

7. The PFA polymer foam of claim 1 or claim 2, wherein one or more PFA polymers of the PFA polymer foam is made up of at least 90 wt% residues of perfluoroalkene and perfluoroalkoxy perfluoroalkene.

8. The PFA polymer foam of claim 1 or claim 2, wherein the PFA polymer foam comprises one or more polymer resins that provide a total resin content of the PFA polymer foam, the one or more polymer resins having an MFR in the range of 0.5-40 g / 10 min.

9. The PFA polymer foam of claim 1 or claim 2, wherein the one or more polymer resins have, as a melt, a transient (time-dependent) extensional viscosity in the range of 103to 106Pa-s at Hencky strain rates from 0.1 s'1up to 10 s'1and at melt temperatures from 320°C up to 380°C, as measured by Sentmanat Extensional rheometer.

10. The PFA polymer foam of claim 1 or claim 2, further comprising a nucleating agent.11 . The PFA polymer foam of claim 1 or claim 2, further comprising one or more chemical foaming agents and / or one or more residues of the one or more chemical foaming agents.

12. The PFA polymer foam of claim 11 , wherein the one or more chemical foaming agents includes one or more CO2 foaming agents selected from carbonates, and one or more N2 foaming agents selected from 5-phenyltetrazole compounds, azocarbonamides, semicarbazides, and hydrazides and nitroso compounds.

13. The PFA polymer foam of claim 1 or claim 2, wherein the PFA polymer foam has a PFA content of at least 80 wt%.

14. A process for making a PFA polymer foam, the process comprising: causing one or more chemical foaming agents to together release both CO2 gas and N2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer foam.

15. The PFA polymer foam of Embodiment 16, wherein the one or more chemical foaming agents includes one or more CO2 foaming agents selected from carbonates, and one or more N2 foaming agents selected from 5-phenyltetrazole compounds, azocarbonamides, semicarbazides, and hydrazides and nitroso compounds.

16. The process of any of claim 14 or claim 15, wherein the one or more chemical foaming agents are provided in an amount to release at least 0.5 mL gas per gram of the one or more resins.

17. The process of claim 14 or claim 15, wherein the one or more chemical foaming agents are provided in an amount to release at least 0.8 mL gas per gram of the one or more resins.

18. The process of claim 14 or claim 15, wherein the one or more chemical foaming agents are provided in an amount to release a molar ratio of CO2 to N2 in the range of 5:1 to 1 :5.

19. The process of claim 14 or claim 15, wherein the process comprises performing chemical foam extrusion on a mixture of the PFA and the one or more chemical foaming agents.

20. The process of claim 16 or claim 17, wherein the PFA polymer foam is a PFA polymer foam according to claim 1 or claim 2.21 . A PFA polymer foam made by a process of claim 16 or claim 17.

22. A layer of a PFA polymer foam according to claim 1 or claim 2.

23. A thermally-insulated tubing comprising: an inner tubular structure comprising wall extending between a first end of the thermally-insulated tubing and an opposing second end of the thermally-insulated tubing , the wall defining an inner lumen extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubing along a longitudinal axis of the thermally-insulated tubing, and the wall comprising one or more material layers; and a layer of PFA polymer foam according to claim 1 surrounding the inner tubular structure.

24. A process for making a thermally-insulated tubing, the process comprising: causing one or more chemical foaming agents to together release both CO2 gas andN2 gas in a PFA polymer melt; mixing the CO2 gas and the N2 gas in the polymer melt; allowing the polymer melt to foam, thereby providing a foamed PFA polymer melt; and allowing the foamed PFA polymer melt to cool to provide the PFA polymer as a layer on an inner tubular structure comprising wall extending between a first end of thethermally-insulated tubing and an opposing second end of the thermally-insulated tubing , the wall defining an inner lumen extending between the first end of the thermally-insulated tubing and the second end of the thermally-insulated tubing along a longitudinal axis of the thermally-insulated tubing, and the wall comprising one or more material layers, the layer of PFA polymer foam surrounding the inner tubular structure.

25. A thermally-insulated tubing made by the process of claim 24.

26. A method for conducting a fluid, the method comprising providing a fluid (e.g., a liquid) to the first end of the thermally-insulated tubing of claim 23 or claim 25; and conducting the fluid to the second end of the thermally-insulated tubing.

27. The method according to claim 26, wherein the thermally-insulated tubing is disposed in an environment having a temperature in the range of 200-550 °F, or -90-0 °F.

28. The method according to claim 26, wherein the fluid has a temperature in the range of 200-550 °F, or -90-0 °F.

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