Thermally-conducting, electrically-insulating polyimide-polysiloxane-based polymer composite materials, tubings made therefrom, and systems including such materials and tubings

Abstract

The present disclosure relates to a thermally-conductive, electrically-insulating polymer composite material, comprising: a continuous polymer phase comprising imide residues and siloxane residues; and dispersed within the continuous polymer phase, a thermally-conductive, electrically-insulating filler. The materials of the disclosure can be formed into tubes, and used, for example, in thermal management systems and methods, especially for magnetic resonance instruments.

Description

THERMALLY-CONDUCTING, ELECTRICALLY-INSULATING POLYIMIDE- POLYSILOXANE-BASED POLYMER COMPOSITE MATERIALS, TUBINGS MADE THEREFROM, AND SYSTEMS INCLUDING SUCH MATERIALS AND TUBINGS Cross-Reference to Related Applications

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application no. 63 / 514,959, filed July 21 , 2023, which is hereby incorporated herein by reference in its entirety.Background of the Disclosure1. Field

[0002] The present disclosure relates to thermally-conducting, electrically-insulating polymer composite materials, tubings made therefrom, and systems including such materials and tubings.2. Technical Background

[0003] The present disclosure relates to thermally-conducting, electrically-insulating polymer composite materials, tubings made therefrom, and systems including such materials and tubings.

[0004] Tubings are often used in heat transfer applications, for example, in conducting a thermal transfer fluid like a coolant between a hot zone (e.g., a hot area of an apparatus that is desired to be cooled) and a cool zone (e.g., a heat sink, a heat exchanger, or merely a cooler environment). Such tubings must, of course, be able to resist the hot temperatures in the relevant hot zone, and are desirably thermally-conductive to allow for efficient heat transfer into and out of the thermal transfer fluid. But, depending on the particular application, they may have a variety of other stringent requirements.

[0005] For example, magnetic resonance imaging (MRI) systems produce images using strong magnetic field gradients, which are generated using a series of superconducting magnetic coils. During operation, significant heat is generated by the magnetic coils themselves, as well as by other components of the gradient subsystem. In order to dissipate this heat away from the system, e.g., in order to maintain a desired temperature, coolant tubes made of copper are conventionally positioned near the heat-generating components and configured to carry coolant water to cool the heat-generating components. However, copper tubing presents a serious drawback: it interferes with the magnetic field, which can reduce signal-to-noise ratio and even provide distorted images. To overcome this limitation, a copper tubing needs to be actively shielded. Additionally, copper tubing is stiff and heavy and susceptible to corrosion by deionized water, which are also undesirable characteristics of a coolant tubing.

[0006] Further improvements in tubings for heat transfer are required.Summary of the Disclosure

[0007] In various aspects, the disclosure provides thermally-conducting and electrically- insulating polymer composite materials that can advantageously be formed into tubings.The materials and tubings can be flexible, resistant to a variety of fluids, especially various coolant fluids, and stable to high continuous use temperatures. Accordingly, the tubings can be useful in the transfer of heat at a first location into a working fluid disposed within the tubing, conducting the heated working fluid to a second location, and the transfer of heat at the second location out of the working fluid disposed within the tubing.

[0008] One aspect of the disclosure relates to a thermally-conductive, electrically- insulating polymer composite material, comprising: a continuous polymer phase comprising imide residues and siloxane residues; and dispersed within the continuous polymer phase, a thermally-conductive, electrically-insulating filler.

[0009] Another aspect of the disclosure is a tubing comprising at least one annular layer of a thermally-conductive, electrically-insulating polymer composite material of the disclosure.

[0010] Another aspect of the disclosure is a method for transferring heat from a heat source, the method comprising providing a tubing of the disclosure positioned in substantial thermal communication with the heat source at a first position, the tubing having a working fluid disposed therein; and transferring heat from the heat source through the tubing and into the working fluid.

[0011] Another aspect of the disclosure is a thermal management system for cooling a heat source, the system comprising: a tubing according to any of embodiments 72-80, in substantial thermal communication with the heat source at a first position; and a source of a working fluid configured to conduct the working fluid through the tubing

[0012] Another aspect of the disclosure is a magnetic resonance instrument, e.g., a magnetic resonance imaging instrument, comprising a gradient coil assembly and a tubing of the disclosure in substantial thermal communication with the gradient coil assembly at a first position; and a source of a working fluid configured to conduct the working fluid through the tubing.

[0013] Another aspect of the disclosure is a method of thermal management for a magnetic resonance instrument comprising a gradient coil assembly, the method comprising providing a tubing of the disclosure positioned in substantial thermal communication with the gradient coil assembly at a first position, the tubing having a working fluid disposed therein; andtransferring heat from the gradient coil assembly through the tubing and into the working fluid.

[0014] Other aspects of the disclosure will be evident to the person of ordinary skill in the art from the present specification.Brief Description of the Drawings

[0015] Various aspects of the disclosure are illustrated by the drawings, in which:

[0016] FIG. 1 is a schematic view of a material according to one embodiment of the disclosure.

[0017] FIG. 2 is a schematic cross-sectional view of a tubing according to one embodiment of the disclosure.

[0018] FIG. 3 is a schematic view of a thermal management system according to one embodiment of the disclosure.

[0019] The person of ordinary skill in the art will appreciate that the drawings are schematic in nature, and are not necessarily to scale and may omit particular components that are not germane to the discussion of the figure.Detailed Description

[0020] The present inventors have noted a number of limitations of existing tubing materials, especially of the copper tubings typically used in magnetic resonance imaging apparatuses. The present inventors note that to overcome the above limitations, it is desirable to replace copper tubing with a polymeric tubing. However, that tubing has to that exhibit a proper suite of thermal, mechanical, electrical, physical and magnetic properties.

[0021] The present disclosure provides thermally-conductive, electrically-insulating polymer composite materials suitable for formation into tubing and use in cooling applications, such as cooling of magnet coils in MRI instruments.

[0022] Thus, in various aspects, the disclosure provides thermally-conducting and electrically-insulating polymer composite materials. The materials and can be flexible, resistant to a variety of fluids, especially various coolant fluids, and stable to high continuous use temperatures. In various embodiments, the materials can be formed into tubings, which can have similarly advantageous properties. Accordingly, the tubings can be useful in the transfer of heat at a first location into a working fluid disposed within the tubing, conducting the heated working fluid to a second location, and the transfer of heat at the second location out of the working fluid disposed within the tubing.

[0023] Such materials and tubings can be especially desirable in a variety of uses. For example, in various aspects of the disclosure, tubings formed of the materials described herein can be used as coolant tubes used in medical diagnostic equipment such asmagnetic resonance imaging systems. But the materials and tubings described herein can find a variety of uses, especially in thermal management applications in which a high rate of heat transfer through the tube wall is advantageous but the electrical properties of metallic tubings are undesirable.

[0024] One aspect of the disclosure is a thermally-conductive, electrically-insulating polymer composite material. The polymer composite material includes a continuous polymer phase comprising imide residues and siloxane residues; and dispersed within the continuous polymer phase, a thermally-conductive filler. This is shown in partial cross- sectional schematic view in FIG. 1 , in which polymer composite material 100 includes a continuous polymer phase 102 in which a thermally-conductive, electrically-insulating filler 104 is disposed.

[0025] As used herein, the continuous polymer phase is continuous with respect to the filler. The continuous polymer phase can in some embodiments itself have some separation of polymer phases, e.g., is present in a plurality of polymer phases, as determined by microscopy. However, in various embodiments, the continuous polymer phase is of a single polymer phase. The person of ordinary skill in the art will appreciate that whether the continuous polymer phase is itself a single phase or multiphasic will depend on a number of factors, including the intermiscibility of the polymers when two or more polymers are present, as well as the miscibility of any additives in the overall polymer phase.

[0026] Based on the description herein, the person of ordinary skill in the art can determine a total number of each type of imide and siloxane residue, the identities of such residues, and polymer molecular weights, and, in the case of polyimide / polysiloxane copolymers, the total number of blocks formed of those residues, and average block lengths and block length distributions, to provide a continuous polymer phase that exhibits desirable mechanical and physical properties conducive to producing a flexible tube from the base polymer. Similarly, the person of ordinary skill in the art can select types and amounts of thermally-conductive fillers to provide a desired degree of thermal conductivity as well as other desirable material properties, depending on the desired end use of the material. Further information regarding these considerations is provided below.

[0027] In various embodiments, the continuous polymer phase is substantially formed of a polyimide / polysiloxane copolymer. For example, in various embodiments, the continuous polymer phase is formed of at least 75 wt% polyimide / polysiloxane copolymer (e.g., a poly(imide-co-siloxane), In various embodiments, the continuous polymer phase is formed of at least 90 wt%, or at least 95 wt% polyimide / polysiloxane copolymer. As described in more detail below, the present inventor has noted that desirable suites of material propertiescan be provided when the continuous polymer phase is substantially made up of a polyimide / polysiloxane copolymer.

[0028] The present inventors have also noted that in many cases a blend of a polyimide polymer and a polysiloxane polymer can be used as the continuous polymer phase to provide a desirable suite of material properties. Accordingly, in various embodiments, the continuous polymer phase is substantially formed of a combination of a polyimide polymer and a polysiloxane polymer. For example, in various embodiments, the continuous polymer phase is formed of at least 75 wt% of a combination of a polyimide polymer and a polysiloxane polymer, In various embodiments, the continuous polymer phase is formed of at least 90 wt%, or at least 95 wt% of a combination of a polyimide polymer and a polysiloxane polymer.

[0029] The present inventors have also noted that various combinations of any of polyimide / polysiloxane copolymers, polyimide polymers and polysiloxane polymers can be used. Accordingly, in various embodiments, the continuous polymer phase is substantially formed of two or more of a polyimide / polysiloxane copolymer, a polyimide polymer, and a polysiloxane polymer. For example, in various embodiments, the continuous polymer phase is formed of at least 75 wt% of two or more of a polyimide / polysiloxane copolymer, a polyimide polymer, and a polysiloxane polymer. In various embodiments, the continuous polymer phase is formed of at least 90 wt%, or at least 95 wt% of two or more of a polyimide / polysiloxane copolymer, a polyimide polymer, and a polysiloxane polymer. The present inventor has noted that various combinations of materials may be used, e.g., a substantial combination of a polyimide / polysiloxane copolymer with a polyimide polymer; a substantial combination of a polyimide / polysiloxane copolymer with a polysiloxane polymer; or a substantial combination of a polyimide / polysiloxane copolymer with a polyimide polymer and a polysiloxane copolymer. Based on the disclosure herein the person of ordinary skill in the art can provide a blend of polymers to provide desired material properties.

[0030] The person of ordinary skill in the art can, based on the present disclosure, select suitable polyimide / polysiloxane copolymers for use in various embodiments of the disclosure. As the person of ordinary skill in the art will appreciate, a polyimide / polysiloxane copolymer will include imide residues and siloxane residues. The person of ordinary skill in the art will be familiar with a variety of polyimide materials, and can adapt residues from such materials for use in the polyimide / polysiloxane polymers of the disclosure. In various desirable embodiments, the imide residues of the polyimide / polysiloxane copolymers have relatively low amounts of aliphatic hydrogen atoms. For example, in various embodiments, the imide residues of the polyimide / polysiloxane copolymer have no more than one aliphatic Hydrogen atom per imide nitrogen. In various embodiments, the imide residues of thepolyimide / polysiloxane copolymer have no more than 0.5 aliphatic hydrogen atoms per imide nitrogen. In various embodiments, the imide residues of the polyimide / polysiloxane copolymer have no more than 0.1 aliphatic hydrogen atoms per imide nitrogen. In various embodiments, the imide residues of the polyimide / polysiloxane copolymer have substantially no aliphatic hydrogen atoms.

[0031] A variety of imide residues can be used. In various advantageous embodiments, the imide residues are polyetherimide residues, i.e., in which individual arylimides are linked by ether groups (e.g., one or more oxygen atoms linking aromatic portions of each arylimide).

[0032] One general formula for the imide residues of the polyimide / polysiloxane copolymer are represented by Formula (I), below:in which the ring system denoted by each “A” independently forms, together with the maleimide carbons, formsT is independently a bond, or a divalent organic radical (e.g., oxo, propan-2, 2-diyl, 1 , 1 ,1 , 3,3,3- hexafluoropropan-2,2-diyl), -O-, or -O-Z-O-, in which Z is a divalent organic radical, or an aromatic ring system (optionally including heteroatoms) having in the range of 6-40 carbon atoms;x has a weight-average value of zero or more; and each Ar1is independently a hydrocarbylene group (e.g., arylene or alkarylene) having in the range of 6- 40 carbons, orent organic radical.

[0033] In various embodiments, in the imide residues of formula (I) the ring system denoted by each “A” independently forms, together with the maleimide carbons, forms the

[0034] In various such embodiments, each T is -O- or -O-Z-O- (i.e. the residues are etherimide residues). In various embodiments, T is -O-. In various embodiments, T is -O-Z- O-, for example, a bisphenol A residue. The T residue desirably is at a position on each phenyl ring that is beta from its nearest carbonyl. The Z moiety can be, for example, (a) an aromatic hydrocarbon radical having 6 to 36 carbon atoms or a halogenated derivatives thereof including perfluoroalkylene groups; (b) a straight or branched chain alkylene radicals having 2 to 24 carbon atoms (c) a cycloalkylene radicals having 3 to 20 carbon atoms, or (d), wherein Q is a divalent moiety, for example, selected from the group consisting of -O-, -S-, -C(O)-, -SO2-, -SO-, -CyH2y- (y being an integer from 1 to 8), and fluorinated derivatives thereof, including perfluoroalkylene groups.

[0035] Examples of anhydrides suitable for use in synthesizing such materials include: 3,3-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride; 4,4'-bis(3,4- dicarboxyphenoxy)diphenyl ether dianhydride; 4,4'-bis(3,4-dicarboxyphenoxy)diphenylsulfide dianhydride; 4,4'-bis(3,4-dicarboxyphenoxy)benzophenone dianhydride; 4,4'-bis(3,4- dicarboxyphenoxy)diphenyl sulfone dianhydride; 2,2-bis[4-(2,3- dicarboxyphenoxy)phenyl]propane dianhydride; 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl ether dianhydride; 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl sulfide dianhydride; 4,4'-bis(2,3- dicarboxyphenoxy)benzophenone dianhydride; 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl sulfone dianhydride; 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy)diphenyl-2,2- propane dianhydride; 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy)diphenyl ether dianhydride; 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride; 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy)benzophenone dianhydride and 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride, pyromellitic dianhydride, biphenyl dianhydride, oxy diphthalic anhydride, sulfone diphthalic anhydride, hydroquinone diphthalic anhydride, and resorcinol diphthalic anhydride. U.S. Patents nos. 3,972,902 and 4,455,410, each of which is hereby incorporated here by reference in its entirety, provide additional information regarding suitable anhydrides and synthesis of polyimides therefrom.

[0036] In various embodiments, in the imide residues of formula (I) the ring system denoted by each “A” independently forms an aromatic ring system (optionally including heteroatoms) having in the range of 6-40 carbon atoms.

[0037] In various embodiments, in the imide residues of formula (I), each Ar1is independently arylene or alkarylene having in the range of 6-40 carbons, e.g., in the range of 6-20 carbons, or 6-15 carbons, or 6-10 carbons. In various embodiments, the Ar1groups substantially lack aliphatic hydrogen atoms, which can provide the low aliphatic hydrogen content described above. Examples of suitable diamine compounds from which the >N- Ar1-N< groups can be derived include, without limitation, m-phenylenediamine, p- phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, m-xylylenediamine, p- xylylenediamine, 2-methyl-4,6-diethyl-1 ,3-phenylene-diamine, 2,4,6-trimethylphenylene-1 ,3- diamine, 5-methyl-4,6-diethyl-1 ,3-phenylene-diamine, benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 1 ,5-diaminonaphthalene, bis(4-aminophenyl)methane, bis(2- chloro-4-amino-3,5-diethylphenyl) methane, bis(4-aminophenyl)propane, 2,4-bis(p-amino-t- butyl)toluene, bis(p-amino-t-butylphenyl)ether, bis(p-methyl-o-aminophenyl)benzene, bis(p- methyl-o-aminopentyl)benzene, 1 ,3-diamino-4-isopropylbenzene, bis(4-aminophenyl)sulfide, bis(4-aminophenyl)sulfone, bis(4-aminophenyl)ether and 1 ,3-bis(3-aminopropyl)benzene.

[0038] In various embodiments, in the imide residues of formula (I), x has a weightaverage value of 0, i.e., the imide residues can include only a single diimide moiety between siloxane residues. However, in many systems, multiple diimide moieties can be provided together in a polyimide block residue, and as such x can have a weight-average value ofgreater than zero, e.g., up to 10, or up to 8, or up to 5. In various embodiments, x has a weight-average value in the range of 0.5-10, e.g., 0.5-8, or 0.5-5. In various embodiments, x has a weight-average value in the range of 1 -10, e.g., 1 -8, or 1-5.

[0039] Similarly, the person of ordinary skill in the art will be familiar with a variety of polysiloxane materials, and can adapt residues from such materials for use in the polyimide / polysiloxane polymers of the disclosure.

[0040] The present inventors have determined that it can be desirable for the siloxane residues to have a substantial aliphatic hydrogen content. In various embodiments, the siloxane residues include at least three aliphatic hydrogens for every silicon atom, e.g., at least four or at least five aliphatic hydrogens for every silicon atom.

[0041] In various embodiments, the siloxane residues have the structural formula (II): -R1-Si(Rs)2-[O-Si(Rs)2]y-O-SI(Rs)2-R1- (II) wherein each R1is independently an arylene, alkylene or arylalkylene group having 1 or more carbon atoms; each Rsis independently hydrogen or C-i-Ce alkyl; and y has a weight-average value of at least 1 .

[0042] In various embodiments, in the siloxane residues of structural formula (II) each R1is an arylene, alkylene or arylalkylene group having a weight average of 1 -20 carbon atoms, e.g., 2-10 carbon atoms. In various embodiments, each R1is an alkylene, e.g., -CH2-CH2- or -CH2-CH2-CH2-

[0043] In various embodiments, in the siloxane residues of structural formula (II) at least 50 mol% of the Rsgroups are C-i-Ce alkyl, e.g., at least 75 mol%, or at least 90 mol%. In various embodiments, in the siloxane residues of structural formula (II) at least 10 mol% of the Rsgroups are C2-Ce alkyl, e.g., at least 15 mol% or at least 25 mol%. In various embodiments, at least 10 mol% of the Rsgroups are C3-C6 alkyl, e.g., at least 15 mol% or at least 25 mol%.

[0044] In various embodiments, in the siloxane residues of structural formula (II) at least 50 mol% of the Rsgroups are methyl, e.g., at least 60 wt% or at least 75 wt%. In various embodiments, in the siloxane residues of structural formula (II) at least 90 mol% of the Rsgroups are methyl, e.g., at least 95 wt% or substantially all.

[0045] In various embodiments, in the siloxane residues of structural formula (II) as a weight-average value of at least 2, e.g., at least 5 or at least 10. In various embodiments, in the siloxane residues of structural formula (II) y has a weight-average value in the range of1-100, e.g., 1-80, or 1-60, or 1-40. In various embodiments, in the siloxane residues of structural formula (II) y has a weight-average value in the range of 2-100, e.g., 2-80, or 2-60, or 2-40. In various embodiments, in the siloxane residues of structural formula (II) y has a weight-average value in the range of 5-100, e.g., 5-80, or 5-60, or 5-40.

[0046] In various embodiments, the polyimide / polysiloxane copolymer is formed substantially of imide residues and siloxane residues, e.g., at least 75 wt%, at least 90 wt%, or at least 95 wt%. For example, in various embodiments, the polyimide / polysiloxane copolymer is formed substantially of imide residues of formula (I) and siloxane residues of formula (II), e.g., at least 75 wt%, at least 90 wt%, or at least 95 wt%.

[0047] In various embodiments, the polyimide / polysiloxane copolymer includes in the range of 5-70 wt% siloxane residues (e.g., in the range of 10-50 wt%). In various embodiments, the polyimide / polysiloxane copolymer includes in the range of 30-95 wt% polyimide ratios (e.g., in the range of 50-90 wt%).

[0048] The molar ratio of -Ar1- to polysiloxane (e.g., Formula (II)) inter-imide structural units can vary, e.g., from 1 :9 to 9:1 , for example, from 1 :9 to 4:1 , or 1 :9 to 2:1 , or 1 :4 to 9:1 , or 1 :4 to 4:1 , or 1 :4 to 2:1 , or 1 :9 to 2:1 , or 1 :4 to 2:1 , or 1 :2 to 2:1.

[0049] The person of ordinary skill in the art will select polyimide / polysiloxane copolymers, especially those based on etherimides, based on the present disclosure. Examples of suitable copolymers can be found, for example, in U.S. Patent Application Publications nos. 2012 / 0021153 and 2008 / 0223602, each of which is hereby incorporated by reference herein in its entirety. Other suitable copolymers are described in U.S. Pat. Nos. 5,028,681 , 4,808,686, 4,690,997, 4,404,350, 4,051 ,163, 4,011 ,279, 3,847,867, 3,833,546 and 3,325,450, each of which is hereby incorporated herein by reference in its entirety.

[0050] Such copolymers can be made using conventional polyimide synthesis techniques, for example, by reaction of diamine-terminated polysiloxanes and optionally other diamine compounds with dianhydride compounds. When multiple diamino components are used, they may be physically mixed prior to reaction with the bisanhydride^), thus forming a substantially random copolymer. Alternatively block or alternating copolymers may be formed by selective reaction the non-polysiloxane diamine with dianhydrides to make polyimide blocks that are subsequently reacted together.

[0051] In some embodiments, the imide residues can etherimide residues, which contain aryl ether linkages that can be derived by polymerization of dianhydrides and / or diamines wherein at least a portion of the dianhydride and / or the diamine contains an aryl ether linkage. In some instances both the diamine and dianhydride will contain an aryl etherlinkage, for example as described above. In various embodiments the aryl ether linkage can be derived from dianhydrides such as bisphenol A diphthalic anhydride, biphenol diphthalic anhydride, oxy diphthalic anhydride or mixtures thereof. In various embodiments the aryl ether linkages can be derived from at least one diamine containing an aryl ether linkage, for example, diamino diphenyl ethers, bis amino phenoxy benzenes, bis-amino phenoxy phenyl sulfones or mixtures thereof. Either the diamine or dianhydride may have aryl ether linkages or in some instances both monomers may contain aryl ether linkages.

[0052] In some other embodiments the polyimide / polysiloxane copolymer can include etherimide sulfone residues, which contain aryl sulfone linkages and aryl ether linkages. Sulfone linkages may be introduced into the polymer by polymerization of dianhydrides and / or diamines wherein at least a portion of the dianhydride or the diamine contains an aryl sulfone linkage. In various embodiments the aryl sulfone linkage can be derived from dianhydrides such as sulfone diphthalic anhydride, diphenyl sulfone diphthalic anhydride or mixtures thereof. In still other the aryl sulfone linkages can be derived from at least one diamine containing an aryl sulfone linkages, for example, diamino diphenyl sulfones (DDS), his amino phenoxy phenyl sulfones (BAPS) or mixtures thereof. Either the diamine or dianhydride may have an aryl sulfone linkage or in some instances both monomers may also contain aryl sulfone linkages.

[0053] In various embodiments, the polyimide / polysiloxane copolymer comprises structural units derived from bisphenol A diphthalic anhydride, phenylenediamine (e.g., m- phenylenediamine), and an amine-terminated polydimethylsiloxane (e.g., bis(3-aminopropyl) polydimethylsiloxane). Such polymers are available commercially under the tradename SILTEM. In various such embodiments, the polyimide / polysiloxane copolymer comprises in the range of 10-45 wt% polysiloxane. In various embodiments, the polyimide / polysiloxane copolymer includes in the range of 10-30 wt% polysiloxane, e.g., 10-25 wt%, or 10-20 wt%, or 15-30 wt%, or 15-25 wt%, or 20-30 wt%. In various embodiments, the polyimide / polysiloxane copolymer includes in the range of 25-45 wt% polysiloxane, e.g., 25- 40 wt%, or 25-35 wt%, or 30-45 wt%, or 30-40 wt%, or 35-45 wt%. In various embodiments, the polyimide / polysiloxane copolymer is made up of at least 75 wt% structural units derived from bisphenol A diphthalic anhydride, phenylenediamine (e.g., m-phenylenediamine), and an amine-terminated polydimethylsiloxane (e.g., bis(3-aminopropyl) polydimethylsiloxane), e.g., at least 90 wt%, or at least 95 wt%.

[0054] The person of ordinary skill in the art will appreciate, as described below, that the polymers described herein can be crosslinked, and thus that a polymer chain of the generalized structure described above can be crosslinked at various points with anothersuch polymer chain, or with different polymer (e.g., a different polyimide / polysiloxane copolymer, a polyimide polymer and / or a polysiloxane polymer).

[0055] As noted above, polyimide polymers and / or polysiloxane polymers can be used in addition to the polyimide / polysiloxane copolymer, or, when both are present, instead of the polyimide / polysiloxane copolymer. Polyimide polymers can, for example, be described generally as described above for the imide residues of the copolymer. A wide variety of polysiloxane polymers can be used, such as poly(dimethylsiloxane), poly(methylhydrosiloxane), poly(dimethylsiloxane-co-propylmethylsiloxane). In various embodiments, the polysiloxane polymer has the structural formula Rs-Si(Rs)2-[O-Si(Rs)2]z-O- Si(Rs)2-Rs, in which Rsis as described above and z is a number sufficient to provide a weight-average molecular weight (GPC, PDMS standards) of at least 20 kDa. The person of ordinary skill in the art is aware of a wide variety of polyimide polymers and polysiloxane polymers and can select suitable polymers and amounts thereof for use in the materials of the disclosure. The amounts of polysiloxane polymer and / or polyimide polymer can be selected, together with an amount of any polyimide / polysiloxane copolymer, to provide a continuous polymer phase that includes in the range of 5-70 wt% siloxane residues (e.g., in the range of 10-50 wt%), and / or in the range of 30-95 wt% polyimide ratios (e.g., in the range of 50-90 wt%).

[0056] Of course, the materials of the disclosure can include other components. For example, it can be desirable to include other polymers in the material to tune its properties. As an example, in various embodiments, the material can further include a polyester / polyether block copolymer, as described in U.S. Patent Application Publication no. 2008 / 0223602. It is desirable for the total amount of imide residues and siloxane residues, whether from a copolymer or individual polymers, to make up at least 75 wt% of the continuous phase, e.g., at least 90 wt% or at least 95 wt%.

[0057] In various desirable embodiments, the continuous polymer material is crosslinked. Crosslinking can be performed to improve resistance to deformation during continuous operation at very high temperatures as well as to improve flexibility at such temperatures. The cross-linking can be carried out at any convenient time, e.g., before, after, or while the thermally-conductive filler is dispersed in the continuous polymer phase.

[0058] Notably, the present inventors have determined that the materials of the disclosure can be crosslinked via exposure to an electron beam. The present inventors have determined that electron beam irradiation can provide particularly favorable bulk properties for the continuous polymer phase and thus for the material of the disclosure. Without intending to be bound by theory, the electron beam radiation can be used toselectively crosslink the siloxane residues of the continuous polymer phase. In various embodiments, the material is crosslinked using an electron beam dose in the range of IQ- 200 kGy, e.g., 30-200 kGy, or 45-200 kGy, or 10-150 kGy, or 30-150 kGy, or 45-150 kGy, or 15-100 kGy, or 30-100 kGy, or 45-100 kGy, at an energy level in the range of 1 to 50 MeV. The present inventors have noted that such dosages can selectively crosslink siloxane residues, especially when they have significant aliphatic hydrogen content as described above. Imide residues, especially when they have low or no aliphatic hydrogen content as described above, are far less susceptible to crosslinking by electron beam at such dosages.

[0059] Electron beam crosslinking of polysiloxane polymers is described, for example, in K. Dawes et aL, “The Effects of Electron Beam and Gamma-Irradiation on Polymeric Materials,” Chapter 52 in J.E. Mark, ed., Physical Properties of Polymers Handbook, 2ndEd. (2007), which is hereby incorporated herein by reference in its entirety.

[0060] Of course, in other embodiments, other methods can be used to crosslink the continuous polymer phase, either selectively between particular residues, or randomly. The person of ordinary skill in the art can use a variety of techniques to crosslink the continuous polymer phase, including oxidative and photochemical methods. Polyimides can be crosslinked with UV radiation, for example, benzophenone moieties (e.g., when Q is C(O)) can absorb UV radiation and form free radicals, which can abstract benzylic hydrogens (e.g., when there are aromatic methyl groups in the imide residues, such as from the use of a methyl-substituted phenylenediamine like 2,4,6-trimethylphenylene-1 ,3-diamine, or from a methyl-substitute aromatic ring as part of the “A” system. The radical species so formed can combine intermolecularly to form crosslinks between imide residues. As an alternative, a separate initiator, photolytic or thermolytic can be used to generate radicals for hydrogen atom abstraction to provide polyimide crosslinking. Siloxanes bearing hydride groups can be crosslinked with diolefins, and materials bearing olefin groups can be crosslinked with hydride-functional silicones. Accordingly, crosslinking can be between imide residues, between siloxane residues, or between an imide residue and a siloxane residue.

[0061] The present inventors note that the residues of the continuous polymer phase can be selected to provide a degree of flame retardance to the continuous polymer phase, and thus to the overall material. The person of ordinary skill in the art is familiar with various polyimide and polysiloxane polymer composite materials that have a degree of flame retardance, and can use such residues in the continuous polymer phases described herein.

[0062] As noted above, the thermally-conductive, electrically insulating polymer composite material also includes, dispersed within the continuous polymer phase, a thermally-conductive, electrically-insulating filler. The person of ordinary skill can providethermally-conductive fillers that provide a desired degree of thermal conductivity while maintaining electrical resistivity and maintaining good material properties for the overall polymer composite material.

[0063] For example, in various such embodiments, the thermally-conductive, electrically- insulating filler includes (or is) boron nitride. In various embodiments, the boron nitride is hexagonal boron nitride. The boron nitride can be provided in a variety of forms, e.g., amorphous boron nitride, boron nitride of the hexagonal system, having a laminated structure of hexagonal-shaped meshed layers); or a turbotrain boron nitride, having randomly oriented layers; platelet boron nitride; boron nitride fibers; boron nitride agglomerates; boron nitride nanotubes. In various embodiments, the boron nitride is in a hexagonal form, a platelet form, or a turbostratic form. In various embodiments, the boron nitride is in a hexagonal form.

[0064] The person of ordinary skill in the art can select a particle size of the boron nitride to provide good dispersion within the continuous polymer phase and good physical properties of the overall material. In various embodiments, a d50 particle size of the boron nitride is in the range of 0.05 microns to 500 microns; or from 0.5 microns to 250 microns; from 1 microns to 150 microns; from 5 microns to 100 microns or from 10 microns to 50 microns. In various embodiments, the boron nitride has a d50 particle size of at least 50 microns (e.g., 50-600 microns, or 50-400 microns, or 50-250 microns, or 50-150 microns, or 100-600 microns, or 100-400 microns, or 100-250 microns).

[0065] In various embodiments, the boron nitride comprises irregularly shaped agglomerates of hexagonal boron nitride platelets, having a d50 particle size of at least 50 pm (e.g., 50-600 microns, or 50-400 microns, or 50-250 microns, or 50-150 microns, or 100- 600 microns, or 100-400 microns, or 100-250 microns).

[0066] The boron nitride component can, for example, comprise crystalline or partially crystalline boron nitride particles made by processes known in the art. These include spherical boron nitride particles in the micron size range produced in a process utilizing a plasma gas as disclosed in U.S. Pat. No. 6,652,822; hexagonal boron nitride comprising spherical boron nitride agglomerates is formed from irregular non-spherical boron nitride particles bound together by a binder and subsequently spray-dried, as disclosed in U.S. Patent Publication No. 2001 / 0021740; boron nitride powder produced from a pressing process as disclosed in U.S. Pat. Nos. 5,898,009 and 6,048,511 ; boron nitride agglomerated powder as disclosed in U.S. Patent Publication No. 2005 / 0041373; boron nitride powder having high thermal diffusivity as disclosed in U.S. Patent Publication No. 2004 / 0208812A1 ;and highly delaminated boron nitride powder as disclosed in U.S. Pat. No. 6,951 ,583. These also include boron nitride particles of the platelet morphology.

[0067] In various embodiments, the boron nitride is in the form of spherical agglomerates of hexagonal boron nitride platelets. In one embodiment of spherical boron nitride powder, the agglomerates have a d50 particle size in the range of 10-500 microns.

[0068] In various embodiments, the boron nitride is in the form of platelets having an average length along the b-axis of at least about 1 micron, and typically 1-20 microns, and a thickness of no more than about 5 microns. In various embodiments, the boron nitride is in the form of platelets having an average aspect ratio of from about 50 to about 300.

[0069] In various embodiments, the boron nitride particles comprise hexagonal boron nitride platelets having an aspect ratio of from about 10 to about 300. In another embodiment, the boron nitride particles have an oxygen content from 0.2 to 2.5 wt. %. In another embodiment, the hexagonal boron nitride particles have a graphitization index of less than 7.

[0070] In various embodiment, the boron nitride is coated (i.e., surface-treated) to improve compatibility with and dispersion in the continuous polymer phase. Examples of surface coating materials for the boron nitride powder include, but are not limited to, reactive silane, isohexadecane, liquid paraffin, non-ionic surfactants, dimethylpolysiloxane (or dimethicone), a mixture of completely methylated, linear siloxane polymers which have been terminally blocked with trimethylsiloxy units, a silazane compound possessing perfluoroalkyl groups, a titanate coupling agent, a zirconate coupling agent, a zirconium aluminate coupling agent, an aluminate coupling agent, and mixtures thereof. In one embodiment, the boron nitride is coated in a reactive silane which may covalently bond to the boron nitride particles and to the surrounding continuous polymer phase, e.g., the siloxane residues.

[0071] Boron nitride is available from a variety of commercial sources, including Saint Gobain Ceramics, 3M, Sintec Keramic, Kawasaki Chemicals, and Momentive Performance Materials.

[0072] A variety of other thermally-conductive, electrically-insulating fillers are known in the art and can be used in addition to or instead of boron nitride. For example, in various embodiments, the thermally-conductive, electrically-insulating filler includes (or is) one or more of aluminum nitride and alumina. But the person of ordinary skill in the art is familiar with a variety of other thermally-conductive, electrically-insulating fillers that could be used, such as silicon nitride, silicon carbide or beryllium oxide.

[0073] The person of ordinary skill in the art can determine a loading of thermally- conductive, electrically-insulating filler that provides a desired degree of thermal performance together with necessary material properties. In various embodiments, the continuous polymer phase is present in an amount of 10-90 wt% of the material, and the thermally-conductive, electrically-insulating filler is present in an amount of 10-90 wt% of the material. In various embodiments, the continuous polymer phase is present in an amount in the range of 10-80 wt% (e.g., 10-70 wt%, or 10-60 wt%, or 10-50 wt%, or 10-40 wt%, or IQ- 30 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 20-90 wt% (e.g., 30-90 wt%, or 40-90 wt%, or 50-90 wt%, or 60-90 wt% or 70-90 wt%) of the material. In various embodiments, the continuous polymer phase is present in an amount in the range of 20-90 wt% (e.g., 20-80 wt%, or 20-70 wt%, or 20-60 wt%, or 20-50 wt%, or 20-40 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 10-80 wt% (e.g., 20-80 wt%, or 30-80 wt%, or 40-80 wt%, or 50-80 wt%, or 60-80 wt%) of the material. In various embodiments, the continuous polymer phase is present in an amount in the range of 30-90 wt% (e.g., 30-80 wt%, or 30-70 wt%, or 30-60 wt%, or 30-50 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of IQ- 70 wt% (e.g., 20-70 wt%, or 30-70 wt%, or 40-70 wt%, or 50-70 wt%) of the material. In various embodiments, the continuous polymer phase is present in an amount in the range of 40-90 wt% (e.g., 40-80 wt%, or 40-70 wt%, or 40-60 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of IQ- 60 wt% (e.g., 20-60 wt%, or 30-60 wt%, or 40-60 wt%) of the material. In various embodiments, the continuous polymer phase is present in an amount in the range of 50-90 wt% (e.g., 50-80 wt%, or 50-70 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 10-50 wt% (e.g., 20-50 wt%, or 30-50 wt%) of the material. In various embodiments, the continuous polymer phase is present in an amount in the range of 60-90 wt% (e.g., 60-80 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 10-40 wt% (e.g., 20-40 wt%) of the material. In various embodiments, the continuous polymer phase is present in an amount in the range of 70-90 wt% and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of IQ- 30 wt% of the material.

[0074] The present inventors have noted that beneficial material properties can be provided especially when the amount of thermally-conductive filler is no more than 40 wt% of the material. For example, in various embodiments, the continuous polymer phase ispresent in an amount of 60-80 wt% of the material, and the thermally-conductive filler is present in an amount of 20-40 wt% of the material.

[0075] The present inventors have found that well-performing thermally-conductive, electrically-insulating polymer composite materials can be provided using the continuous polymer phase and the thermally-conductive, electrically-insulating filler as the substantial components. For example, in various embodiments, the continuous polymer phase and the thermally-conductive filler make up at least 75 wt% of the thermally-conductive, electrically- insulating polymer composite material, e.g., at least 90 wt%, or at least 95 wt%.

[0076] Moreover, the person of ordinary skill in the art will appreciate that a variety of other components can be present in the material. These can include, without limitation, one or more of metal oxides, smoke suppressants, flame retardants, boron containing compounds, anti-drip agents such as fluoropolymers, fillers / reinforcements, minerals, other inorganic fillers such as C-nanotubes, flow aids / plasticizers, mold release compounds, antioxidants, impact modifiers, fibers / fibrous fillers, thermal stabilizers, nucleating agents, clarifying agents, crystallization suppressants / accelerators, colors / dyes / pigments, UV absorbers, light stabilizers, lubricants, anti-static agents, foaming agents, and anti-foaming agents. These can be selected by the person of ordinary skill in the art to provide desirable properties to the material, especially with the goal of maintaining thermal conductivity and electrical resistivity.

[0077] In many cases, it is important that the thermally-conductive, electrically-insulating material has relatively high thermal conductivity. The person of ordinary skill in the art can provide highly-conductive materials based on the present disclosure. For example, in various embodiments, the thermally-conductive, electrically-insulating material has a thermal conductivity of at least 0.3 W / m-K, e.g., in the range of 0.3-10 W / m-K, or 0.3-5 W / m-K, or 0.3-3 W / m-K, or 0.3-2 W / m-K. In various embodiments, the thermally-conductive, electrically-insulating material has a thermal conductivity of at least 0.5 W / m-K, e.g., in the range of 0.5-10 W / m-K, or 0.5-5 W / m-K, or 0.5-3 W / m-K, or 0.5-2 W / m-K. In various embodiments, the thermally-conductive, electrically-insulating material has a thermal conductivity of at least 0.7 W / m-K, e.g., in the range of 0.7-10 W / m-K, or 0.7-5 W / m-K, or 0.7-3 W / m-K, or 0.7-2 W / m-K. In various embodiments, the thermally-conductive, electrically-insulating material has a thermal conductivity of at least 1 W / m-K, e.g., in the range of 1-10 W / m-K, or 1-5 W / m-K, or 1-3 W / m-K, or 1-2 W / m-K. In various embodiments, thermal conductivities are quantified using the procedure of ASTM C177-19. In various embodiments, thermal conductivities are quantified using the procedure of ASTM D5470-12. In various embodiments, thermal conductivities are quantified using the procedure of ASTM C518-17.

[0078] In many cases, it is important that the thermally-conductive, electrically-insulating material has relatively high electrical resistivity. The person of ordinary skill in the art can provide highly-resistive materials based on the present disclosure. For example, in various embodiments, the thermally-conductive, electrically-insulating material has an electrical resistivity of at least 108ohms-cm, e.g., at least 101° ohms-cm, or at least 1012ohms-cm. Electrical resistivities are measured as described in ASTM D257-14(2021)e1.

[0079] The materials of the disclosure can be compounded and processed using techniques familiar to the person of ordinary skill in the art. For example, materials can be compounded by melt blending, although solution blending is also possible. Melt processing methods can be performed in a variety of types of equipment, such as twin-screw extruders (e.g., co-rotating and counter-rotating extruders), single screw extruders, co-kneaders, discpack processors and various other types of extrusion equipment. The person of ordinary skill in the art can select processing conditions, for example, by working at desirably low temperatures and / or shear rates and / or head pressure and / or residence time to avoid excessive degradation of the material. The blended material can be formed into pellets or granules for later processing into desired articles, or, in some cases, can be directly extruded into a desired shape (e.g., a tubing). Reactive extrusion techniques can be performed in some cases, e.g., to form a polyimide / polysilicone copolymer in the extruder itself.

[0080] In particular embodiments, the polymer composite materials according to the present invention, can also be shaped or fabricated into films, coatings, sheets, strips, tapes, ribbons and the like. The film, coating and sheet may be fabricated by any method known in the art, including blown bubble processes (e.g., simple bubble as well as biaxial orientation techniques such trapped bubble, double bubble and tenter framing), cast extrusion, injection molding processes, thermoforming processes, extrusion coating processes, profile extrusion, and sheet extrusion processes. As noted above, the extrusion used to blend the material can in some cases also be used to form a desired shape of the material, e.g., a tubing.

[0081] In some embodiments as described above, the polymer composite material is crosslinked, e.g., by treatment with an e-beam. The person of ordinary skill in the art will select an appropriate time for such crosslinking, recognizing that it is often desirable to perform such crosslinking after the material is formed into a desired shape (e.g., after it is formed into a tubing), as crosslinked materials will often be difficult to further shape.

[0082] While extrusion can be used to form articles from the materials of the disclosure as noted above and as described below with respect to tubings, the person of ordinary skillin the art will appreciate that a variety of other techniques can be used, for example, compression molding, injection molding, stamp molding, embossing, and blow molding.

[0083] As noted above, the materials of the disclosure can be especially useful in the formation of tubings for thermal transfer applications. Accordingly, another aspect of the disclosure is tubing comprising at least one annular layer of a thermally-conductive, electrically-insulating polymer composite material as described herein. FIG. 2 provides a schematic cross-sectional view of such a tubing 220, which includes a single annular layer of a thermally-conductive, electrically-insulating polymer composite material 200.

[0084] The thickness of the annular layer of the thermally-conductive, electrically- insulating polymer composite material can vary. For example, in various embodiments, the layer thickness is in the range of 0.1-5 mm, e.g., 0.1-3 mm, or 0.1-2 mm, or 0.1-1 .5 mm, or 0.1-1 mm. In various embodiments, the layer thickness is in the range of 0.25-5 mm, e.g., 0.25-3 mm, or 0.25-2 mm, or 0.25-1 .5 mm, or 0.25-1 mm. In various embodiments, the layer thickness is in the range of 0.5-5 mm, or 0.5-3 mm, or 0.5-2 mm, or 0.5-1.5 mm, or 0.5-1 mm. In various embodiments, the layer thickness is in the range of 1 -5 mm, e.g., 1 -3 mm, or 1-2 mm.

[0085] The tubing can be provided with a variety of inner diameters. For example, in various embodiments, the tubing has an inner diameter in the range of 1-50 mm, e.g., in the range of 2-30 mm, or 2-20 mm, or 2-10 mm. In various embodiments, the tubing has an inner diameter in the range of 5-50 mm, e.g., in the range of 5-30 mm, or 5-20 mm, or 5-10 mm. In various embodiments, the tubing has an inner diameter in the range of 10-50 mm, e.g., in the range of 10-30 mm, or 10-20 mm.

[0086] The person of ordinary skill in the art can select a thickness of the annular layer as well as overall tubing to provide a tubing with a desired thermal conductivity and desired physical properties (e.g., wall strength, flexibility, pressure drop, minimum bend radius, burst pressure, flex fatigue life, compression set, axial elongation, radial expansion, radial compression) for a desired application.

[0087] In various embodiments, the tubing is formed substantially of the material of the disclosure. For example, in various embodiments, a cross-section of the tubing is formed of at least 75 wt% of the material of the disclosure, e.g., at least 90 wt%, or at least 95 wt%. Of course, the person of ordinary skill in the art can include other layers in the tubing, such as an internal fluid contact layer or an exterior ink layer, but desirably such layers do not substantially affect the thermal conductivity of the tubing. And in sections of the tubing where heat transfer is not desired, the tubing can be further jacketed.

[0088] The tubings of the disclosure can be prepared to exhibit not only high thermal conductivity and high electrical resistivity, but also a one or more of a variety of other properties, such as a high temperature rating for continuous operation, high flexibility, high flame retardance, high burst pressure, high dielectric strength, chemical inertness, especially to cooling fluids, and strong bondability to outer encapsulating materials such as another concentric polymer layer, braided polymer fibers, metal braids and wires, and with potting resins. The outer surface of the tubing can be modified using chemical and physical methods such as a chemical etch treatment, corona treatment or plasma treatment.

[0089] The person of ordinary skill in the art can use conventional methods to make the tubing, e.g., by extrusion. In various embodiments, the melt blending of the polymers and blends and any other additives, necessary or desirable to improve the properties of the tubing, may be compounded in an extruder by adding the components simultaneously at the throat or sequentially through different feeders located at different positions along the barrel of the extruder. The extrudate emanating from the extruder may be either fed directly to a separate extruder, or cooled and converted into pellets or granules for use in a future operation to make the tubing. Alternatively, the tubing may be directly extruded by feeding the components, and additives, directly into an extruder configured with a tubing extrusion die, where the components may be mixed immediately prior to extrusion.

[0090] The present inventors have determined that the tubings of the disclosure can be used in thermal management applications, for example, to cool a heat source. The tubings of the disclosure can have a high rate of thermal transfer through the thermally-conductive, electrically-insulating polymer composite material, while remaining electrically insulating, flexible and chemically inert. For example, another aspect of the disclosure is a method for transferring heat from a heat source. The method comprises providing a tubing of the disclosure positioned in substantial thermal communication with the heat source at a first position, the tubing having a working fluid (e.g., water) disposed therein and transferring heat from the heat source through the tubing and into the working fluid. The method can, in various embodiments, further include conducting the working fluid away from the first position. The working fluid can, in various embodiments, be conducted via the tubing to a second position, where heat can be conducted from the working fluid through the tubing to the surrounding atmosphere or to a cooler object, such as a heat exchanger, a radiator or a heat sink.

[0091] Similarly, another aspect of the disclosure is thermal management system for cooling a heat source. The thermal management system can include a tubing of the disclosure in substantial thermal communication with the heat source at a first position; and a source of a working fluid (e.g., water) configured to conduct the working fluid through thetubing. The source of the working fluid can be, for example, a water line provided with sufficient pressure to conduct water through the tubing; or can be a tank of working fluid (e.g., a coolant) with a pump configured to pump the working fluid through the tubing. In various embodiments the system can further include a heat exchanger, a radiator or a heat sink operatively coupled to the tubing and configured to remove heat from the working fluid at a second position different from the first position. The heat exchanger, radiator or heat sink can, for example, be provided in a substantially closed circuit with the tubing and the source of the working fluid.

[0092] The thermal management systems and methods of the disclosure can be applicable to a wide variety of heat sources. In various embodiments, the heat source is operating at a temperature, or has an operating temperature, in the range of 50-250 °C, e.g., in the range of 50-200 °C, or 50-150 °C, or 50-100 °C, or 75-250 °C, or 75-200 °C, or 75-150 °C, or 75-125 °C. or 100-250 °C, or 100-200 °C, or 100-150 °C, or 150-250 °C, or 150-200 °C. As the tubings of the disclosure can be made to be substantially electrically-insulating, they are especially useful with heat sources that are electrical or magnetic in nature. For example, in various embodiments, the heat source comprises one or more magnets, e.g., one or more electromagnets, such as magnetic coils. In various embodiments, the heat source comprises one or more electrical devices, such as a battery (or an anode or cathode thereof); an electric motor; a computing system or subsystem such as a computer circuit (integrated or otherwise); a lamp; and a laser. Of course, the person of ordinary skill in the art will identify other heat sources that can be suitably cooled by the methods and systems of the disclosure.

[0093] An example of such a system is shown in schematic view in FIG. 3. Here, system 330 includes a heat source 340, and a tubing 320 of the disclosure in substantial thermal contact with the heat source at a first position 345, here, by being wound around the heat source. A source of working fluid 350 is configured to conduct the working fluid through the tubing. In the example of FIG. 3, the system 330 further includes a heat exchanger 360 operatively coupled to the tubing and configured to remove heat from the working fluid at a second position 365 different from the first position 345. Here, the heat exchanger is provided in a substantially closed circuit with the tubing and the source of the working fluid.

[0094] The tubings of the disclosure can be made to be resistant to a variety of common fluids. Accordingly, a variety of different fluids can be used as the working fluid. The person of ordinary skill in the art, can, for example, select from a variety of coolants for use as the working fluid. In various embodiments, the working fluid comprises (or is) water. In various embodiments, the working fluid comprises (or is) a glycol, such as ethylene glycol or propylene glycol, which in some embodiments can be provided in combination with water.

[0095] The present inventors have determined that the tubings, methods and systems of the disclosure can be especially useful in heat management in magnetic resonance systems like magnetic resonance imaging systems. For example, during a patient scan, the gradient coil(s) of the gradient coil assembly that produce the magnetic field gradients dissipate large amounts of heat. The heat produced by the gradient coils can cause an increase in the temperature of the MRI system's patient bore and the magnet warm bore. Heating of the patient bore may reduce the amount of RF power that can be transmitted during imaging which in turn can affect the efficiency of the MRI system. In addition, an increase in temperature of the patient bore can be uncomfortable for a patient and may even become dangerous unless safety interlocks are designed to prevent overheating. Minimizing any increase in temperature of the patient bore is important to MRI scanner efficiency and safety. Similar issues apply to other types of magnetic resonance instruments. The heat produced by the gradient coil assembly of an magnetic resonance system (e.g., by the gradient coils themselves and / or by other components in the gradient coil assembly) may be removed using the methods and systems of the disclosure. Accordingly, in various embodiments of the methods and systems described herein, the heat source is a gradient coil assembly of a magnetic resonance instrument, e.g., a magnetic resonance imaging instrument.

[0096] Another aspect of the disclosure is a magnetic resonance instrument, e.g., a magnetic resonance imaging instrument, comprising a gradient coil assembly and a tubing of the disclosure in substantial thermal communication with the gradient coil assembly at a first position, and a source of a working fluid configured to conduct the working fluid through the tubing. The magnetic resonance instrument can be further configured as described above with respect to systems of the disclosure, and methods analogous to the methods of the disclosure can be used to cool the gradient coil assembly.

[0097] Various methods of cooling, cooling systems and MRI instruments are described, for example, in U.S. Patents nos. 7015692, 7250766, 7301343, 7495444 and 8362774, each of which is hereby incorporated herein by reference in its entirety. Various embodiments of the disclosure as described herein can be configured as described in any of these references, using the tubings of the disclosure as a replacement for the coolant tubings described therein.

[0098] Various aspects of the disclosure are provided by the following non-limiting examples.

[0099] Five formulations were compounded by twin screw extrusion:

[0100] Copolymer 1 was a copolymer of bisphenol A diphthalic anhydride, m- phenylenediamine, and bis(3-aminopropyl)polydimethylsiloxane, with 30-38 wt% polydimethylsiloxane content.

[0101] Volume percentages are based on the feed materials; Copolymer 1 was in the form of pellets. The boron nitride was in the form of agglomerates of platelets.

[0102] Formulations 1-4 and Copolymer 1 had a V-0 rating in a 50 W vertical burning test pursuant to UL 94.

[0103] Tubings were extruded from Copolymer 1 , Formulation 1 and Formulation 2, and minimum bend radiuses were determined.

[0104] The person of ordinary skill in the art would understand that these materials could be made to be more flexible in a variety of manners, for example, by including more polysiloxane in the material, e.g., in the form of a polyimide / polysiloxane copolymer having a higher polysiloxane content, or in the form of a separate polysiloxane polymer. Of course, other polymer additives could be used to provide additional flexibility.

[0105] Materials were formed into [SHAPE? HOW? were these tubings of the nominal sizes above?], with some being treated with e-beam dosages as shown in the table below. Tensile strength at break, tensile strain at break and elastic moduli were determined using an Instron system [RIGHT?]

[0106] Various aspects and embodiments of the disclosure are further described by the following enumerated embodiments, which may be combined in any number and in any combination that is not logically or technically inconsistent.Embodiment 1 . A thermally-conductive, electrically-insulating polymer composite material, comprising: a continuous polymer phase comprising imide residues and siloxane residues; and dispersed within the continuous polymer phase, a thermally-conductive, electrically-insulating filler.Embodiment 2. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 1 , wherein the continuous polymer phase is present in a plurality of phases.Embodiment 3. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 1 , wherein the continuous polymer phase is present in a single phase.Embodiment 4. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-3, wherein the continuous polymer phase is substantially formed of a polyimide / polysiloxane copolymer.Embodiment 5. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-3, wherein the continuous polymer phase is formed of at least 75 wt% polyimide / polysiloxane copolymer (e.g., at least 90 wt%, or at least 95 wt%).Embodiment 6. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-3, wherein the continuous polymer phase is substantially formed of a combination of a polyimide polymer and a polysiloxane polymer.Embodiment 7, A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-3, wherein the continuous polymer phase is formed of at least 75 wt% of a combination of a polyimide polymer and a polysiloxane polymer, (e.g., at least 90 wt%, or at least 95 wt%).Embodiment 8. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-3, wherein the continuous polymer phase is substantially formed of two or more of a polyimide / polysiloxane copolymer, a polyimide polymer, and a polysiloxane polymer.Embodiment 9. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-3, wherein the continuous polymer phase is formed of at least 75 wt% of two or more of a polyimide / polysiloxane copolymer, a polyimide polymer, and a polysiloxane polymer (e.g., at least 90 wt%, or at least 95 wt%).Embodiment 10. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5, 8 and 9, wherein the imide residues of the polyimide / polysiloxane copolymer have no more than one aliphatic hydrogen atom per imide nitrogen.Embodiment 11. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5, 8 and 9, wherein the imide residues of the polyimide / polysiloxane copolymer have no more than 0.5 aliphatic hydrogen atoms per imide nitrogen.Embodiment 12. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5, 8 and 9, wherein the imide residues of the polyimide / polysiloxane copolymer have no more than 0.1 aliphatic hydrogen atoms per imide nitrogen.Embodiment 13. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5, 8 and 9, wherein the imide residues of the polyimide / polysiloxane copolymer have substantially no aliphatic hydrogen atoms.Embodiment 14. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5, and 8-13, wherein the imide residues are polyetherimide residues (e.g., having one or more oxygen atoms linking aromatic portions of each arylimide).Embodiment 15. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5, and 8-14, wherein the imide residues of the polyimide / polysiloxane copolymer are represented by Formula (I)in whichthe ring system denoted by each “A” independently forms, together with the maleimide carbons, formsa divalent organic radical (e.g., oxo, propan-2, 2-diyl, 1 , 1 ,1 , 3,3,3- hexafluoropropan-2,2-diyl), -O-, or -O-Z-O-, in which Z is a divalent organic radical, or an aromatic ring system (optionally including heteroatoms) having in the range of 6-40 carbon atoms; x has a weight-average value of zero or more; and each Ar1is independently a hydrocarbylene group (e.g., arylene or alkarylene) having in the range of 6-40 carbons, orradical.Embodiment 16. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 15, wherein the imide residues of formula (I) the ring system denoted by each “A” independently forms, together with the maleimide carbons,Embodiment 17. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 15, wherein each T is -O-.Embodiment 18. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 15-17, wherein each Ar1is independently arylene or alkarylene having in the range of 6-40 carbons, e.g., in the range of 6-20 carbons, or 6-15 carbons, or 6-10 carbons.Embodiment 19. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 15-17, wherein the Ar1groups substantially lack aliphatic hydrogen atoms.Embodiment 20. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 15, wherein the imide residues of formula (I) the ring system denoted by each “A” independently forms an aromatic ring system (optionally including heteroatoms) having in the range of 6-40 carbon atoms.Embodiment 21 . A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 15-20, wherein x has a weight-average value of 0.Embodiment 22. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 15-20, wherein x has a weight-average value of greater than zero, e.g., up to 10, or up to 8, or up to 5.Embodiment 23. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 15-20, wherein x has a weight-average value in the range of 0.5-10, e.g., 0.5-8, or 0.5-5.Embodiment 24. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 15-20, wherein x has a weight-average value in the range 1-10, e.g., 1-8, or 1-5.Embodiment 25. A thermally-conductive, electrically-insulating polymer material according to any of claims 1 -5 and 8-24, wherein the siloxane residues include at least three aliphatic hydrogens for every silicon atom, e.g., at least four or at least five aliphatic hydrogens for every silicon atom.Embodiment 26. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-25, wherein the siloxane residues have the structural formula (II):-R1-Si(Rs)2-[O-Si(Rs)2]y-O-SI(Rs)2-R1- (II) wherein each R1is independently an arylene, alkylene or arylalkylene group having 1 or more carbon atoms; each Rsis independently hydrogen or C-i-Ce alkyl; and y has a weight-average value of at least 1 .Embodiment 27. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 26, wherein each R1is an arylene, alkylene or arylalkylene group having a weight average of 1-20 carbon atoms, e.g., 2-10 carbon atoms.Embodiment 28. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 26 or embodiment 27, wherein at least 50 mol% of the Rsgroups are C-i-Ce alkyl, e.g., at least 75 mol%, or at least 90 mol%.Embodiment 29. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 26-28, wherein at least 10 mol% of the Rsgroups are C2-Ce alkyl, e.g., at least 15 mol% or at least 25 mol%.Embodiment 30. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 26-28, wherein at least 10 mol% of the Rsgroups are C3-C6 alkyl, e.g., at least 15 mol% or at least 25 mol%.Embodiment 31. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 26-30, wherein at least 50 mol% of the Rs groups are methyl, e.g., at least 60 wt% or at least 75 wt%.Embodiment 32. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 26 or embodiment 27, wherein at least 90 mol% of the Rs groups are methyl, e.g., at least 95 wt% or substantially all.Embodiment 33. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 26-32, wherein y has a weight-average value of at least 2, e.g., at least 5 or at least 10.Embodiment 34. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 26-32, wherein y has a weight-average value in the range of 1-100, e.g., 1-80, or 1-60, or 1-40.Embodiment 35. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 26-32, wherein y has a weight-average value in the range of 2-100, e.g., 2-80, or 2-60, or 2-40.Embodiment 36. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 26-32, wherein y has a weight-average value in the range of 5-100, e.g., 5-80, or 5-60, or 5-40.Embodiment 37. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 26-32, wherein y has a weight-average value in the range of 5-100, e.g., 5-80, or 5-60, or 5-40.Embodiment 38. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-37, wherein the polyimide / polysiloxane copolymer is formed substantially of imide residues and siloxane residues, e.g., at least 75 wt%, at least 90 wt%, or at least 95 wt%.Embodiment 39. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-38, wherein the polyimide / polysiloxane copolymer is formed substantially of imide residues of formula (I) and siloxane residues of formula (II), e.g., at least 75 wt%, at least 90 wt%, or at least 95 wt%.Embodiment 40. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-39, wherein the polyimide / polysiloxane copolymer includes in the range of 5-70 wt% siloxane residues (e.g., in the range of 10-50 wt%).Embodiment 41. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-40, wherein the polyimide / polysiloxane copolymer includes in the range of 30-95 wt% polyimide ratios (e.g., in the range of 50-90 wt%).Embodiment 42. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-41 , wherein the imide residues are of formula (I) and wherein the molar ratio of -Ar1- to polysiloxane (e.g., Formula (II)) inter-imide structural units is in the range of from 1 :9 to 9:1 , for example, from 1 :9 to 4:1 , or 1 :9 to 2:1 , or 1 :4 to 9:1 , or 1 :4 to 4:1 , or 1 :4 to 2:1 , or 1 :9 to 2:1 , or 1 :4 to 2:1 , or 1 :2 to 2:1.Embodiment 43. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-42, wherein the polyimide / polysiloxane copolymer comprises structural units derived from bisphenol A diphthalic anhydride, phenylenediamine (e.g., m-phenylenediamine), and an amine-terminated polydimethylsiloxane (e.g., bis(3-aminopropyl) polydimethylsiloxane).Embodiment 44. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 43, wherein the polyimide / polysiloxane copolymer includes in the range of 10-30 wt% polysiloxane, e.g., 10-25 wt%, or 10-20 wt%, or 15-30 wt%, or 15-25 wt%, or 20-30 wt%.Embodiment 45. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 43, wherein the polyimide / polysiloxane copolymer includes in the range of 25-45 wt% polysiloxane, e.g., 25-40 wt%, or 25-35 wt%, or 30-45 wt%, or 30-40 wt%, or 35-45 wt%.Embodiment 46 A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 43-45, the polyimide / polysiloxane copolymer is made up of at least 75 wt% structural units derived from bisphenol A diphthalic anhydride, phenylenediamine (e.g., m-phenylenediamine), and an amine-terminated polydimethylsiloxane (e.g., bis(3-aminopropyl) polydimethylsiloxane), e.g., at least 90 wt%, or at least 95 wt%.Embodiment 47. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-46, wherein the polymer composite material further comprises a polyimide polymer.Embodiment 48. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 47, wherein the polyimide polymer is formed of residues as described in any of embodiments 10-24.Embodiment 49. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-5 and 8-48, wherein the polymer composite material further comprises a polysiloxane polymer.Embodiment 50. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 49, wherein the polysiloxane polymer has the structural formula Rs-Si(Rs)2-[O-Si(Rs)2]z-O-SI(Rs)2-Rs, in which Rsis as described above and z is a number sufficient to provide a weight-average molecular weight (GPC, PDMS standards) of at least 20 kDa.Embodiment 51. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-50, wherein the continuous polymer phase comprises in the range of 5-70 wt% siloxane residues (e.g., in the range of 10-50 wt%), and / or in the range of 30-95 wt% polyimide ratios (e.g., in the range of 50-90 wt%).Embodiment 52. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-51 , wherein the continuous polymer phase is crosslinked.Embodiment 53. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 52, wherein the continuous polymer phase is crosslinked by exposure to an electron beam.Embodiment 54. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 53, wherein the continuous polymer phase is selectively crosslinked via crosslinking of siloxane residues.Embodiment 55. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 52-54, wherein the material is crosslinked using an electron beam dose in the range of 10-200 kGy, e.g., 30-200 kGy, or 45-200 kGy, or 10- 150 kGy, or 30-150 kGy, or 45-150 kGy, or 15-100 kGy, or 30-100 kGy, or 45-100 kGy, at an energy level in the range of 1 to 50 MeV.Embodiment 56. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-55, wherein the thermally-conductive, electrically-insulating filler includes (or is) boron nitride, e.g., hexagonal boron nitride.Embodiment 57. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 56, wherein the boron nitride has a d50 particle size in the range of 0.05 microns to 500 microns; or from 0.5 microns to 250 microns; from 1 microns to 150 microns; from 5 microns to 100 microns or from 10 microns to 50 microns.Embodiment 58. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 56, wherein the boron nitride has a d50 particle size of at least 50 microns (e.g., 50-600 microns, or 50-250 microns, or 50-150 microns).Embodiment 59. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-58, wherein the thermally-conductive, electrically-insulating filler includes (or is) one or more of aluminum nitride and alumina.Embodiment 60. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-59, wherein the continuous polymer phase is present in an amount of 10-90 wt% of the material, and the thermally-conductive, electrically-insulating filler is present in an amount of 10-90 wt% of the material.Embodiment 61. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-59, wherein the continuous polymer phase is present in an amount in the range of 10-80 wt% (e.g., 10-70 wt%, or 10-60 wt%, or 10-50 wt%, or 10-40 wt%, or 10-30 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 20-90 wt% (e.g., 30-90 wt%, or 40-90 wt%, or 50-90 wt%, or 60-90 wt% or 70-90 wt%) of the material.Embodiment 62. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-59, wherein the continuous polymer phase is present in an amount in the range of 20-90 wt% (e.g., 20-80 wt%, or 20-70 wt%, or 20-60 wt%, or 20-50 wt%, or 20-40 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 10-80 wt% (e.g., 20-80 wt%, or 30-80 wt%, or 40-80 wt%, or 50-80 wt%, or 60-80 wt%) of the material.Embodiment 63. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-59, wherein the continuous polymer phase is present in an amount in the range of 30-90 wt% (e.g., 30-80 wt%, or 30-70 wt%, or 30-60 wt%, or 30-50 wt%) and the material and the thermally-conductive, electrically-insulatingfiller is present in an amount in the range of 10-70 wt% (e.g., 20-70 wt%, or 30-70 wt%, or 40-70 wt%, or 50-70 wt%) of the material.Embodiment 64. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-59, wherein the continuous polymer phase is present in an amount in the range of 40-90 wt% (e.g., 40-80 wt%, or 40-70 wt%, or 40-60 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 10-60 wt% (e.g., 20-60 wt%, or 30-60 wt%, or 40-60 wt%) of the material.Embodiment 65. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-59, wherein the continuous polymer phase is present in an amount in the range of 50-90 wt% (e.g., 50-80 wt%, or 50-70 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 10-50 wt% (e.g., 20-50 wt%, or 30-50 wt%) of the material.Embodiment 66. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-59, wherein the continuous polymer phase is present in an amount in the range of 60-90 wt% (e.g., 60-80 wt%) and the material and the thermally-conductive, electrically-insulating filler is present in an amount in the range of IQ- 40 wt% (e.g., 20-40 wt%) of the material.Embodiment 67. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-59, wherein the continuous polymer phase is present in an amount in the range of 70-90 wt% and the material and the thermally- conductive, electrically-insulating filler is present in an amount in the range of 10-30 wt% of the material.Embodiment 68. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1 -67, wherein the amount of thermally-conductive filler is no more than 40 wt% of the material.Embodiment 69. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-68, the continuous polymer phase and the thermally-conductive filler make up at least 75 wt% of the thermally-conductive, electrically- insulating polymer composite material, e.g., at least 90 wt%, or at least 95 wt%.Embodiment 70. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-69, having a thermal conductivity of at least 0.3 W / m-K, e.g., in the range of 0.3-10 W / m-K, or 0.3-5 W / m-K, or 0.3-3 W / m-K, or 0.3-2 W / m-K.Embodiment 71 . A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-69, having a thermal conductivity of at least 0.5 W / m-K, e.g., in the range of 0.5-10 W / m-K, or 0.5-5 W / m-K, or 0.5-3 W / m-K, or 0.5-2 W / m-K.Embodiment 72. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-69, having a thermal conductivity of at least 0.7 W / m-K, e.g., in the range of 0.7-10 W / m-K, or 0.7-5 W / m-K, or 0.7-3 W / m-K, or 0.7-2 W / m-K.Embodiment 73. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1-69, having a thermal conductivity of at least 1 W / m-K, e.g., in the range of 1-10 W / m-K, or 1-5 W / m-K, or 1-3 W / m-K, or 1-2 W / m-K.Embodiment 74. A thermally-conductive, electrically-insulating polymer composite material according to any of embodiments 1 -73, having an electrical resistivity of at least 108ohms-cm, e.g., at least 101° ohms-cm, or at least 1012ohms-cm.Embodiment 75. A tubing comprising at least one annular layer of a thermally- conductive, electrically-insulating polymer composite material according to any of embodiments 1-74.Embodiment 76. A tubing according to embodiment 75, wherein the at least one annular layer has a thickness in the range of 0.1 -5 mm, e.g., 0.1 -3 mm, or 0.1-2 mm, or 0.1 - 1.5 mm, or 0.1-1 mm.Embodiment 76. A tubing according to embodiment 75, wherein the at least one annular layer has a thickness in the range of 0.25-5 mm, e.g., 025-03 mm, or 0.25-2 mm, or 0.25-1 .5 mm, or 0.25-1 mm.Embodiment 78. A tubing according to embodiment 75, wherein the at least one annular layer has a thickness in the range of 0.5-5 mm, or 0.5-2 mm, or, 0.5-1 .5 mm, or 0.5- 1 mm.Embodiment 79. A tubing according to embodiment 75, wherein the at least one annular layer has a thickness in the range of 1-5 mm, e.g., 1-3 mm, or 1-2 mm.Embodiment 80. A tubing according to any of embodiments 75-79, having an inner diameter in the range of 2-50 mm, e.g., in the range of 2-30 mm, or 2-20 mm, or 2-10 mm.Embodiment 81. A tubing according to any of embodiments 75-79, having an inner diameter in the range of 5-50 mm, e.g., in the range of 5-30 mm, or 5-20 mm, or 5-10 mm.Embodiment 82. A tubing according to any of embodiments 75-79, having an inner diameter in the range of 10-50 mm, e.g., in the range of 10-30 mm, or 10-20 mm.Embodiment 83. A tubing according to any of embodiments 75-79, wherein a crosssection of the tubing is formed of at least 75 wt% of the material of the disclosure, e.g., at least 90 wt%, or at least 95 wt%.Embodiment 84. A method for transferring heat from a heat source, the method comprising providing a tubing according to any of embodiments 75-83 positioned in substantial thermal communication with the heat source at a first position, the tubing having a working fluid disposed therein; and transferring heat from the heat source through the tubing and into the working fluid.Embodiment 85. The method of embodiment 84, further comprising conducting the conducting the working fluid away from the first position.Embodiment 86. The method of embodiment 84, further comprising conducting the working fluid via the tubing to a second position.Embodiment 87. The method of embodiment 86, wherein at the second position heat is conducted from the working fluid through the tubing to the surrounding atmosphere or to a cooler object, such as a heat exchanger, a radiator or a heat sink.Embodiment 88. A thermal management system for cooling a heat source, the system comprising: a tubing according to any of embodiments 75-83, in substantial thermal communication with the heat source at a first position; anda source of a working fluid configured to conduct the working fluid through the tubing.Embodiment 89. The thermal management system of embodiment 88, wherein the source of the working fluid is a water line provided with sufficient pressure to conduct water through the tubing; or is a tank of working fluid (e.g., a coolant) with a pump configured to pump the working fluid through the tubing.Embodiment 90. The thermal management system of embodiment 88 or embodiment 89, further including a heat exchanger, a radiator or a heat sink operatively coupled to the tubing and configured to remove heat from the working fluid at a second position different from the first position.Embodiment 91 . The thermal management system according to embodiment 90, wherein the heat exchanger, radiator or heat sink is provided in a substantially closed circuit with the tubing and the source of the working fluid.Embodiment 92. The method or thermal management system according to any of embodiments 84-91 , wherein the heat source is operating at a temperature, or has an operating temperature, in the range of 50-250 °C, e.g., in the range of 50-200 °C, or 50-150 °C, or 50-100 °C, or 75-250 °C, or 75-200 °C, or 75-150 °C, or 75-125 °C. or 100-250 °C, or 100-200 °C, or 100-150 °C, or 150-250 °C, or 150-200 °C.Embodiment 93. The method or thermal management system according to any of embodiments 84-92, wherein the heat sources is electrical or magnetic in nature.Embodiment 94. The method or thermal management system according to any of embodiments 84-92, wherein the heat source comprises one or more magnets, e.g., one or more electromagnets, such as magnetic coils.Embodiment 95. The method or thermal management system according to any of embodiments 84-92, wherein the heat source comprises one or more electrical devices, such as a battery (or an anode or cathode thereof); an electric motor; a computing system or subsystem such as a computer circuit (integrated or otherwise); a lamp; and a laser.Embodiment 96. The method or thermal management system according to any of embodiments 84-95, wherein the working fluid is a coolant.Embodiment 97. The method or thermal management system according to any of embodiments 84-95, wherein the working fluid comprises (or is) water.Embodiment 98. The method or thermal management system according to any of embodiments 84-95, the working fluid comprises (or is) a glycol, such as ethylene glycol or propylene glycol, e.g., provided in combination with water.Embodiment 99. The method or thermal management system according to any of embodiments 84-98, wherein the heat source is a gradient coil assembly of a magnetic resonance instrument, e.g., a magnetic resonance imaging instrument.Embodiment 100. A magnetic resonance instrument, e.g., a magnetic resonance imaging instrument, comprising a gradient coil assembly and a tubing according to any of embodiments 75-83 in substantial thermal communication with the gradient coil assembly at a first position; and a source of a working fluid configured to conduct the working fluid through the tubing.Embodiment 101. A method of thermal management for a magnetic resonance instrument comprising a gradient coil assembly, the method comprising providing a tubing according to any of embodiments 75-83 positioned in substantial thermal communication with the gradient coil assembly at a first position, the tubing having a working fluid disposed therein; and transferring heat from the gradient coil assembly through the tubing and into the working fluid.Embodiment 102. The magnetic resonance instrument or method of embodiment 100 or embodiment 101 , as further described by any of embodiments 84-92 and 96-99.

Claims

What is claimed is:

1. A thermally-conductive, electrically-insulating polymer composite material, comprising: a continuous polymer phase comprising imide residues and siloxane residues; and dispersed within the continuous polymer phase, a thermally-conductive, electrically- insulating filler.

2. A thermally-conductive, electrically-insulating polymer composite material according to claim 1 , wherein the continuous polymer phase is formed of at least 75 wt% polyimide / polysiloxane copolymer.3, A thermally-conductive, electrically-insulating polymer composite material according to claim 1 , wherein the continuous polymer phase is formed of at least 75 wt% of a combination of a polyimide polymer and a polysiloxane polymer.

4. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 2, wherein the imide residues of the polyimide / polysiloxane copolymer have no more than 0.1 aliphatic hydrogen atoms per imide nitrogen.

5. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 2, wherein the imide residues of the polyimide / polysiloxane copolymer are represented by Formula (I)in which the ring system denoted by each “A” independently forms, together with the maleimide carbons, formsT is independently a bond, a divalent organic radical (e.g., oxo, propan-2, 2-diyl, 1 , 1 ,1 , 3,3,3- hexafluoropropan-2,2-diyl), -O-, or -O-Z-O-, in which Z is a divalent organic radical, or an aromatic ring system (optionally including heteroatoms) having in the range of 6-40 carbon atoms; x has a weight-average value of zero or more; and each Ar1is independently a hydrocarbylene group (e.g., arylene or alkarylene) having in the range of 6-40 carbons, ordivalent organic radical.

6. A thermally-conductive, electrically-insulating polymer composite material according to claim 5, wherein the imide residues of formula (I) the ring system denoted by each “A” independently forms, together with the maleimide carbons, forms the structure7. A thermally-conductive, electrically-insulating polymer composite material according to claim 5, wherein the Ar1groups substantially lack aliphatic hydrogen atoms.

8. A thermally-conductive, electrically-insulating polymer composite material according to claim 5, wherein x has a weight-average value in the range of 0.5-10.

9. A thermally-conductive, electrically-insulating polymer material according to claim 2, wherein the siloxane residues include at least three aliphatic hydrogens for every silicon atom.

10. A thermally-conductive, electrically-insulating polymer composite material according to claim 2, wherein the siloxane residues have the structural formula (II):-R1-Si(Rs)2-[O-Si(Rs)2]y-O-SI(Rs)2-R1- (II) wherein each R1is independently an arylene, alkylene or arylalkylene group having 1 or more carbon atoms; each Rsis independently hydrogen or C-i-Ce alkyl; and y has a weight-average value of at least 1 .

11. A thermally-conductive, electrically-insulating polymer composite material according to claim 10, wherein at least 50 mol% of the Rsgroups are C-i-Ce alkyl.

12. A thermally-conductive, electrically-insulating polymer composite material according to claim 10, wherein at least 10 mol% of the Rsgroups are C3-C6 alkyl.

13. A thermally-conductive, electrically-insulating polymer composite material according to claim 2, wherein the polyimide / polysiloxane copolymer is formed of at least 90 wt% imide residues and siloxane residues.

14. A thermally-conductive, electrically-insulating polymer composite material according to embodiment 2, wherein the polyimide / polysiloxane copolymer includes in the range of 10-50 wt% siloxane residues.

15. A thermally-conductive, electrically-insulating polymer composite material according to claim 2, wherein the imide residues are of formula (I) and wherein the molar ratio of -Ar1- to polysiloxane (e.g., Formula (II)) inter-imide structural units is in the range of from 1 :9 to 9:1.

16. A thermally-conductive, electrically-insulating polymer composite material according to claim 2, wherein the polyimide / polysiloxane copolymer comprises structural units derived from bisphenol A diphthalic anhydride, phenylenediamine (e.g., m- phenylenediamine), and an amine-terminated polydimethylsiloxane (e.g., bis(3-aminopropyl) polydimethylsiloxane).

17. A thermally-conductive, electrically-insulating polymer composite material according to claim 2, wherein the polymer composite material further comprises a polyimide polymer and / or a polysiloxane polymer.

18. A thermally-conductive, electrically-insulating polymer composite material according to claim 1 , wherein the continuous polymer phase is crosslinked.

19. A thermally-conductive, electrically-insulating polymer composite material according to claim 18, wherein the continuous polymer phase is crosslinked by exposure to an electron beam.

20. A thermally-conductive, electrically-insulating polymer composite material according to claim 19, wherein the continuous polymer phase is selectively crosslinked via crosslinking of siloxane residues.

21. A thermally-conductive, electrically-insulating polymer composite material according to claim 19, wherein the material is crosslinked using an electron beam dose in the range of 10-200 kGy at an energy level of 1-75 MeV.

22. A thermally-conductive, electrically-insulating polymer composite material according to claim 1 , wherein the thermally-conductive, electrically-insulating filler includes (or is) boron nitride, e.g., hexagonal boron nitride.

23. A thermally-conductive, electrically-insulating polymer composite material according to claim 1 , wherein the continuous polymer phase is present in an amount in the range of 50-90 wt% and the thermally-conductive, electrically-insulating filler is present in an amount in the range of 10-50 wt% of the material.

24. A thermally-conductive, electrically-insulating polymer composite material according to claim 1 , wherein the amount of thermally-conductive filler is no more than 40 wt% of the material.

25. A thermally-conductive, electrically-insulating polymer composite material according to claim 1, the continuous polymer phase and the thermally-conductive filler make up at least 90 wt% of the thermally-conductive, electrically-insulating polymer composite material.

26. A thermally-conductive, electrically-insulating polymer composite material according to claim 1 , having a thermal conductivity of at least 0.5 W / m-K.

27. A tubing comprising at least one annular layer of a thermally-conductive, electrically- insulating polymer composite material according to claim 1.

28. A method for transferring heat from a heat source, the method comprising providing a tubing according to claim 27 positioned in substantial thermal communication with the heat source at a first position, the tubing having a working fluid disposed therein; and transferring heat from the heat source through the tubing and into the working fluid.

29. A thermal management system for cooling a heat source, the system comprising: a tubing according to claim 27, in substantial thermal communication with the heat source at a first position; and a source of a working fluid configured to conduct the working fluid through the tubing.

30. The method or thermal management system according to claim 28 or claim 29, wherein the heat source is operating at a temperature, or has an operating temperature, in the range of 50-250 °C.

31. A magnetic resonance instrument, e.g., a magnetic resonance imaging instrument, comprising a gradient coil assembly and a tubing according to claim 27 in substantial thermal communication with the gradient coil assembly at a first position; and a source of a working fluid configured to conduct the working fluid through the tubing.

32. A method of thermal management for a magnetic resonance instrument comprising a gradient coil assembly, the method comprising providing a tubing according to claim 27 positioned in substantial thermal communication with the gradient coil assembly at a first position, the tubing having a working fluid disposed therein; andtransferring heat from the gradient coil assembly through the tubing and into the working fluid.

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