high-tenacity electrically conductive composite material for aircraft fuel systems

Abstract

The invention relates to composite polymer compositions comprising a base polyaryletherketone polymer, a conductive filler, a dispersion and processing additive, and optionally a dielectric filler. The composite polymers exhibit maintained or improved strength, increased toughness, and significantly increased elongation at break compared to the base polymer. The composite polymer can be used in lightweight, non-metallic fuel transport circuits in aircraft. [Figure 1]

Description

Title of the invention: High-toughness electrically conductive PEEK for aircraft fuel circuits

[0001] BACKGROUND OF THE INVENTION

[0002] The demand for increased fuel efficiency in the aerospace industry has led to significant development in the field of polymer composites to reduce weight while maintaining the structural integrity of aircraft and aircraft parts used in the fuselage, wings, and cabin applications. To further reduce aircraft weight and simplify its architecture, it is essential to also introduce composites into the fuel transport system, for example, fuel lines, reducers, flanges, brackets, etc. For successful use of polymer composites in an aircraft fuel system, the material must have suitable electrical conductivity to meet the electrostatic discharge (ESD) specification and lightning protection in accordance with the Radio Technical Commission for Aeronautics (RTCA) DO-160 (environmental) standard.In addition, high strength, ductility and toughness are required for the material to meet structural load requirements and withstand the rigors of post-processing steps such as thermal bending and handling during manufacturing, assembly and use.

[0003] Historically, to develop an electrically conductive polymer with ESD properties, fillers such as carbon black, graphite, and carbon fiber have been used. This range of electrical resistance, from 10⁵ to 10⁸ ohms, typically requires more than 10% by weight of fillers. At this high filler loading, the polymers become brittle and rigid, making them unsuitable for applications such as fuel tubes because they require post-processing such as bending and thermoforming.

[0004] High-temperature polymers such as PEEK exhibit good tensile properties, chemical resistance, thermal stability, and relatively high ductility with an elongation at break typically between 25% and 45%, making them theoretically suitable for replacing metallic aluminum fuel tubes.

[0005] Commercially available carbon nanotube (CNT)-PEEK composite polymers have suitable electrical resistance for ESD discharges, unfortunately the elongation at break may only be between 2% and 5% and these materials may therefore not be suitable for the fuel tube application.

[0006] US patent 10,435,539, Mapkar et al., describes a solid polymer composite material, for example comprising a polyamide or a polyetheretherketone, a carbon nanotube, and a spherical nanodiamond additive.

[0007] US patent 20130206273, Guest et al., describes a downhole composite component comprising a polymer matrix including a thermoset or thermoplastic polymer, a nanoparticle filler and reinforcing fibers.

[0008] US patent 20140091253, Myllymaki et al., describes a thermoplastic thermal composite material containing nanodiamond, comprising nanodiamonds, a thermoplastic polymer and a filler such as a boron nitride filler.

[0009] An improved and economical conductive composite material exhibiting improved strength and toughness, including electrical conductivity suitable for ESD and lightning protection, required for a non-metallic fuel transport circuit, is desirable.

[0010] SUMMARY

[0011] The present description relates to an economical conductive composite material prepared from a composition comprising a high-temperature PEEK polymer, exhibiting improved strength and toughness as well as electrical conductivity suitable for ESD and lightning protection, to meet or exceed the specification for electrostatic discharge (ESD) and lightning protection in accordance with the (environmental) DO-160 standards of the Radio Technical Commission for Aeronautics (RTCA) when compared to the basic PEEK polymer.

[0012] A solid polymer conductive composite material is proposed, comprising a polyaryletherketone polymer (PAEK), a conductive filler, a dispersion and processing additive, and a dielectric filler. The PAEK polymer may be selected from the group consisting of a polyetheretherketone (PEEK) and a polyetherketoneketone (PEKK).

[0013] The base PEEK polymer can be a medium- to high-viscosity PEEK polymer. The base PEEK polymer can be unreinforced.

[0014] The conductive charge can be chosen from the group consisting of carbon nanotubes, graphene, graphene oxide, carbon nanofibers, and carbon nanostructures.

[0015] The dispersion and processing additive can be selected from polyhedral oligomeric silsesquioxanes (POSS), silanes, and silanol-POSS. The dielectric filler can be selected from the group consisting of nano-alumina, nano-silica, sublimed alumina, sublimed silica, ZnO, and TiO2. In some embodiments, the conductive composite material does not include a nanodiamond filler.

[0016] The solid polymer composite material may comprise from about 90% by weight to about 99% by weight of a basic polyetheretherketone (PEEK) polymer.

[0017] The solid polymer composite material may comprise from about 0.25% by weight to about 5% by weight of the electrically conductive filler.

[0018] The solid polymer composite material may comprise from about 0.25% by weight to about 5% by weight of dispersion and processing additives.

[0019] The solid polymer composite material may comprise from about 0.05% by weight to about 3% by weight of the dielectric filler.

[0020] The solid polymer composite material according to the invention may have one or more of the following characteristics: tensile strength at room temperature (73 °F) of at least 80 MPa; elongation at break of at least 20%; electrical resistance between 105 Q and 108 Q; maximum tensile strength of at least 95 MPa or more; strain energy at break of at least 15 MPa or more; and Izod impact resistance on notched bar of at least 60 KJ / m2 or more.

[0021] A non-metallic fuel transport circuit component for an aircraft can be prepared from the conductive composite material according to the invention. The aircraft component can be a fuel tube, a flexible hose, a coupling, a clamp, a conduit, a reducer, a flange, a ferrule, a bracket, and a housing.

[0022] A non-metallic fuel tube is described, comprising at least one layer prepared from the conductive composite composition according to the invention. The fuel tube may have an electrical resistance between 100 kQ and 100 MQ / 15"; a maximum operating pressure of at least 120 psi; a continuous operating temperature of -65°F or less than at least 275°F; an outlet operating temperature of at least 325°F; and comply with RTCA DO-160 environmental standards.

[0023] A solid polymer conductive composite material is described which is prepared from a composition comprising 90 to 99% by weight of a PEEK polymer; 0.25 to 5.0% by weight of a conductive filler; 0 to 3% by weight of a dielectric filler; and 0.25 to 5.0% by weight of a dispersion and processing additive. The solid polymer conductive composite material may be prepared from a composition comprising 95 to 98.5% by weight of a PEEK polymer; 0.5 to 3.0% by weight of a conductive filler; 0.5 to 2% by weight of a dielectric filler; and 0.5 to 3.0% by weight of a dispersion and processing additive. The solid polymer conductive composite material may be prepared from a composition comprising 95 to 98.5% by weight of a PEEK polymer; 0.5 to 3.0 wt% of carbon nanotubes; 0.5 to 2 wt% of sublimed silica; and 0.5 to 3.0 wt% of POSS. A solid polymer conductive composite material is described that is prepared from a composition comprising 96 to 98.5% by weight of a PEEK polymer; 0.5 to 2.0% by weight of a conductive filler; 0.5 to 1.5% by weight of a dielectric filler; and 0.5 to 2.0% by weight of a dispersion and processing additive. In some embodiments, the solid polymer conductive composite material comprises a total amount of combined fillers not exceeding 5% by weight.

[0024] The conductive composite material may exhibit a tensile strength of 100 MPa or more at room temperature according to ASTM D 638. The elongation at break may be 20% or more, 30% or more, 60% or more, 70% or more, 80% or more, or 90% or more when measured at room temperature according to ASTM D638. The strain energy at break, as measured by the area under the tensile stress strain curve, may be 18 MPa or more. The maximum tensile strength may be 100 MPa or more. The tensile strength at -65°F may be 140 MPa or more. The tensile strength at 73°F may be 90 MPa or more. The tensile strength at 275°F may be 50 MPa or more. The tensile modulus of elasticity at -65°F can be 4.5 GPa or more. The tensile modulus of elasticity at 73°F can be 4.0 GPa or more. The tensile modulus of elasticity at 275°F can be 3.5 GPa or more.Impact resistance (Izod on notched bar) at -65°F can be 15 kJ / m² or more. Impact resistance (Izod on notched bar) at 73°F can be 16 kJ / m² or more. Impact resistance (Izod on notched bar) at 275°F can be 100 kJ / m² or more.

[0025] The composite polymer may be a conductive composite polymer. The conductive composite polymer may be prepared from a conductive composite composition.

[0026] In some embodiments, the conductive composite composition may include a PEEK base polymer in an amount of between 90 and 99% by weight, between 95 and 99% by weight, or between 96 and 98.5% by weight. In some embodiments, the conductive composite composition may include a conductive filler in an amount of between 0.5 and 5.0% by weight, between 0.5 and 3% by weight, or between 0.5 and 2% by weight. In some embodiments, the conductive composite composition may include a dielectric filler in an amount of between 0 and 3% by weight, between 0 and 2% by weight, between 0.5 and 2% by weight, or between 0.5 and 1.5% by weight. In some embodiments, the conductive composite composition may include a dispersion and treatment additive in an amount of between 0.3 and 5.0% by weight, between 0.5 and 3% by weight, or between 0.5 and 2.0% by weight.

[0027] In certain embodiments, the conductive composite composition may include a PEEK base polymer at 90 to 99% by weight, a conductive filler at 0.5 at 5.0% by weight, a dielectric filler at 0 to 3% by weight, and a dispersion and treatment additive at 0.3 to 5.0% by weight.

[0028] In some embodiments, the conductive composite composition may include a PEEK base polymer of 95 to 99% by weight, a conductive filler of 0.5 to 3% by weight, a dielectric filler of 0.5 to 2% by weight, and a dispersion and treatment additive of 0.5 to 3% by weight.

[0029] In some embodiments, the conductive composite composition may include a PEEK base polymer of 96 to 98.5% by weight, a conductive filler of 0.5 to 2% by weight, a dielectric filler of 0.5 to 1.5% by weight, and a dispersion and treatment additive of 0.5 to 2.0% by weight.

[0030] The composite polymer can exhibit a tensile strength at room temperature (73 °F) of at least 80 MPa; of at least 90 MPa, or of at least 100 MPa.

[0031] The composite polymer may exhibit an elongation at break of at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, or at least 70%.

[0032] The composite polymer can be an ESD composite polymer having an electrical resistance between 100 KQ and 100 MQ / 15".

[0033] The composite polymer can be an ESD composite polymer having an electrical resistance between 105 Q and 108 Q.

[0034] The composite polymer may exhibit a maximum tensile strength of 95 MPa or more, or 100 MPa or more.

[0035] The composite polymer can exhibit a strain energy at break of at least 15 MPa, or at least 18 MPa.

[0036] The composite polymer can exhibit an Izod impact resistance on a notched bar of at least 60 kJ / m², at least 80 kJ / m², or at least 100 kJ / m² at 275 °F. Brief description of the drawings

[0037] Fig. 1 shows a schematic drawing of an example of a non-metallic fuel transport circuit.

[0038] Fig. 2A shows a pie chart of fractional weight reduction and associated fuel gain (overall 20%) based on a single-aisle aircraft fuel transport circuit for parts prepared from conductive composite materials of the invention replacing aluminum components including fuel tubes, flanges, couplers, fasteners, and supports.

[0039] Fig. 2B shows an aircraft tube process map including mixing PAEK composite polymer with carbon nanotube fillers, tube extrusion, overmolding of ferrules, thermoforming / bending of the tube, and assembly. High strength and toughness are important for the bending and assembly stages.

[0040] Figure 3 shows a bar graph of tensile strength (MPa) at room temperature for, from left to right, the comparative base PEEK 1, the comparative base PEEK 2, the PEEK 1 composite polymer sample of the invention, the PEEK 2 composite polymer sample of the invention, and four comparative commercial NTC PEEK samples. The two samples of the invention and one commercial NTC conductive PEEK sample exhibit a tensile strength >100 MPa at room temperature according to ASTM D 638.

[0041] Figure 4 shows a bar graph of elongation at break (%) at room temperature for, from left to right, the comparative basic PEEK 1, the comparative basic PEEK 2, the PEEK 1 composite polymer sample of the invention, the PEEK 2 composite polymer sample of the invention, and four comparative commercial NTC PEEK samples. The elongation at break is > 20% for each of the basic PEEK 1 and basic PEEK 2 samples. The elongation at break is > 30% for the PEEK 1 composite polymer sample of the invention, and > 80% for the PEEK 2 composite polymer sample of the invention. However, the four commercial PEEK samples with conductive NTC filler exhibit an elongation at break < 4%.

[0042] Figure 5 shows a stress-strain data graph for two different formulations of the PEEK 2 composite polymer samples of the invention and the comparative PEEK 2 sample. Tensile stress (MPa) is plotted against tensile strain (mm / mm) to obtain the stress-strain curves.

[0043] The PEEK 2 composite polymer formula 2 sample of the invention exhibits a stress-strain curve indicating that the sample is strong and ductile, and the PEEK 2 composite polymer formula 1 sample of the invention exhibits a stress-strain curve indicating that the sample is strong and tough, while the comparative basic PEEK 2 sample exhibits a stress-strain curve indicating that the sample is strong and brittle.

[0044] Figure 6 shows a bar graph of mechanical properties including maximum tensile strength (MPa) and elongation at break (%) for samples of comparative base PEEK 1, comparative base PEEK 2, PEEK 1 composite polymer of the invention, and PEEK 2 composite polymer of the invention. The samples of the invention exhibit a maximum tensile strength similar to or slightly higher (101.5 MPa, 104.1 MPa respectively) than that of the comparative base PEEK 1 (98.7 MPa) and PEEK 2 samples. comparative base (93.6 MPa). The composite polymer samples of the invention show a significantly higher elongation at break (%), more than 2 times or more than 3 times greater than that of the comparative base PEEK 1 and comparative base PEEK 2 samples.

[0045] Figure 7 shows a bar graph of the strain energy at break (MPa) for samples of comparative base PEEK 1 and PEEK 2, and samples of the PEEK 1 and PEEK 2 composite polymers of the invention. The composite polymer samples of the invention exhibit increased toughness compared to the comparative PEEK 1 and PEEK 2 samples.

[0046] Figure 8 shows a bar graph of tensile strength (MPa) at three temperatures (-65°F, 73°F, 275°F) for comparative basic PEEK 1 and basic PEEK 2 samples and samples of the PEEK 1 composite polymer of the invention and the PEEK 2 composite polymer of the invention. Comparable tensile strength exists at each of the three temperatures between the comparative PEEK 1 and PEEK 2 composite polymers and the polymer of the invention.

[0047] Figure 9 shows a bar graph of the tensile modulus of elasticity (GPa) at three temperatures (-65°F, 73°F, 275°F) for comparative basic PEEK 1 and basic PEEK 2 samples and samples of the PEEK 1 composite polymer of the invention and the PEEK 2 composite polymer of the invention. A comparable tensile modulus of elasticity exists at each of the three temperatures between the comparative PEEK 1 and PEEK 2 composite polymers and the polymer of the invention.

[0048] Figure 10 shows a bar graph of impact resistance (Izod on notched bar) at three temperatures -65°F, 73°F, and 275°F for samples of comparative base PEEK 2 and PEEK 2 + NTC-2 of the invention. The samples of the invention show significantly improved impact resistance of at least approximately two times or more that of the comparative samples at each of the three temperatures.

[0049] Fig. 11 shows a photograph of the comparative base PEEK 2 samples where the samples broke or dislocated at high temperature at 275 °F in the impact resistance test (Izod on notched bar).

[0050] Figure 12A shows a photograph of the PEEK 1 composite polymer casing sample of the invention having an outside diameter of 2" and a wall thickness of 0.05" after the impact test. The casing sample showed no signs of failure after an impact at 35 J. Following the impact test, the casing sample was subjected to bursting and rupture pressures. The casing ruptured at -410 psi and did not fail at the point of impact.

[0051] Figure 12B shows a photograph of the PEEK 2 composite polymer tubing sample of the invention, having an outside diameter of 2" and a wall thickness of 0.05" after the impact test. The tubing sample survived an impact of 35 J and 50 J, finally failing at 65 J. After an impact test, the tubing sample was subjected to stamping and rupture pressures. Like the PEEK 1 composite polymer sample tubing of the invention, the PEEK 2 composite polymer sample tubing of the invention ruptured at -410 psi and did not fail at the point of impact.

[0052] Fig. 13 shows a tensile fatigue bar graph showing fatigue cycles at room temperature, 5 Hz, 73 MPa for a comparative basic PEEK, a lower toughness ESD PEEK, and a high toughness ESD PEEK as described exhibiting over 2,250,000 fatigue cycles. DETAILED DESCRIPTION

[0053] The present description provides composite polymer compositions and materials with electrical conductivity suitable for electrostatic discharge (ESD), while increasing the strength and toughness of the base PEEK (polyetheretherketone) polymer to approximately twice that of the base PEEK polymer, and achieving an improved elongation at break of up to 60% to 120%, which can be approximately two to three times that of the base PEEK. This makes it possible to design fuel lines and other fuel system components that are tough, exhibit high impact resistance, are more fatigue-resistant, and more elastic than commercially available ESD PEEK.

[0054] The terminology used here is solely for the purpose of describing particular embodiments and is not intended to limit the invention.

[0055] The singular forms "a / an" and "the" are intended to also include the plural forms, unless the context clearly indicates otherwise. The term "and / or" designates and encompasses any possible combination of one or more of the listed associated elements.

[0056] The term "approximately" when referring to a measurable value such as a quantity of a compound, a dose, a duration, a temperature and the like is intended to encompass variations of 10%, 5%, 1%, 0.5%, or even 0.1% of the specified quantity.

[0057] The terms "includes" and / or "comprising", when used in this specification, specify the presence of the features, integers, steps, operations, elements, and / or components mentioned, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0058] Unless otherwise specified, all terms, including technical and scientific terms used in the description, have the same meaning as that commonly understood by a person skilled in the art to whom this description belongs. In the event of conflicting terminologies, this specification takes precedence.

[0059] All patents, patent applications and publications mentioned herein are incorporated in their entirety by way of reference.

[0060] The embodiments described according to one aspect of this description are not limited to that aspect. The embodiments may also apply to a different aspect of the description, provided that the embodiments do not prevent those aspects of the invention from functioning for their intended purpose.

[0061] Unless otherwise specified, the term "room temperature" means approximately 73 °F (23 °C).

[0062] The invention provides adaptable nanocomposite polymers with ductility and toughness superior to those of the base polymer alone, and conferring functional properties such as electrical and thermal conductivity. Synergistic behavior appears when different compositions, the size and shape of the nanofiller, and appropriate ratios are used to enhance the properties of the nanocomposite, which may not appear with the addition of individual nanofillers. Each filler material can impart unique properties to the composite and enhance its properties to make it useful for replacing metal in aerospace and automotive applications.

[0063] A lightweight, non-metallic fuel transport circuit is proposed that is compatible with static electricity and lightning, and exhibits higher strength and toughness compared to the base polymer alone, or to commercially available PEEK-carbon nanotube materials. The fuel transport circuit may include tubing, flanges, fittings, couplers, fasteners, brackets, ferrules, housings, and seals, for example, as shown in [Fig. 1]. The tubing may be fuel tubing. The tubing may include rotary bending. The tubing may be extruded tubing. The fasteners may include installation fasteners. The flanges may include overmolded flanges. The seals may include conductive seals.The lightweight, non-metallic fuel transport system results in weight reduction (~20%) and fuel savings, as well as reduced system costs, and maintains a flexible tubing and coupling installation strategy. Weight reduction and associated fuel savings (overall 20%) are expected based on a single-aisle aircraft fuel transport system for components made from conductive composite materials of the invention, replacing aluminum components including tubes, flanges, and other fittings. couplers, fasteners, and supports, as shown in [Fig. 2A]. It is anticipated that replacing the fuel lines in the aircraft fuel transport system will contribute the greatest proportion of weight reduction. [Fig. 2B] shows an aircraft tube process map including mixing the PAEK composite polymer with carbon nanotube fillers, tube extrusion, ferrule overmolding, tube thermoforming / bending, and assembly. High strength and toughness are important for the bending and assembly steps.

[0064] Generally, the polymer composite can be prepared by taking a polyaryletherketone polymer, adding a conductive filler such as carbon nanotubes, one or more dispersion and processing fillers, and optionally a dielectric filler. The combinations described herein produce a synergistic effect on the structural properties of the non-metallic composite polymer.

[0065] The disclosure relates to a conductive composite polymer comprising a base polymer, a conductive filler, a dielectric filler, and one or more dispersion and processing fillers. In some embodiments, the conductive composite polymer does not contain polyamide, such as a nylon material.

[0066] The base polymer can be a thermoplastic polyaryletherketone (PAEK) polymer. PAEK is a linear aromatic polyetherketone polymer. The PAEK polymer can be selected from the group consisting of a polyetheretherketone (PEEK) and a polyetherketoneketone (PEKK). The structures of PEEK and PEKK have aromatic rings with different ratios of ether groups to ketone groups. PEKK has a second ketone group in its repeating structure.

[0067] PEEK polymers can be obtained by step-growth polymerization via the dialkylation of bisphenolate salts. This includes the reaction of 4,4'-difluorobenzophenone or 1,4-bis(4-fluorobenzoyl)benzene with hydroquinone in the presence of alkali carbonates. The polymer is then isolated by removing the alkali metal fluoride and the polymerization solvent.

[0068] The PEEK polymer may be a commercially available PEEK polymer. The PEEK polymer may be selected from, for example, a Victrex PEEK such as VICTREX®, VICTREX™ PEEK™ (Victrex pic), a Dow DuPont PEEK (Vespel), a Quadrant PEEK (Ketron), a SAB IC PEEK such as, for example, LNP™ THERMOCOMP™, LNP™ LUBRICOMP™, LNP™ STAT-KON™, a Lehman & Voss PEEK such as, for example, LUVOCOM®, a PEEK from the RTP company such as, for example, the RTP 2200 series; a Solvay PEEK such as, for example, KeTaSpire®, Solviva® Zeniva®, Tribocomp®, and Evonik PEEKs such as, for example, VESTAKEEP® PEEK. PEEK polymer can be unreinforced PEEK polymer. PEEK can be semi-crystalline. PEEK can be in the form of granules. The PEEK polymer can have a melt viscosity at 400 °C ranging from approximately 130 Pa·s to approximately 500 Pa·s. The PEEK polymer can have a medium to high melt viscosity ranging from approximately 300 Pa·s to approximately 500 Pa·s according to ISO 11443. The melt viscosity can be measured as [1000 s⁻¹] / Pa·s. In some embodiments, the base PEEK is not blended with a polyamide such as a nylon material. In some embodiments, the base PEEK polymer is unreinforced. In some embodiments, the base PEEK polymer may be semi-crystalline.

[0069] PEEK can be processed by conventional methods such as injection molding, extrusion, compression molding, etc. However, the processing conditions used for molding PEEK can affect its crystallinity, and therefore its mechanical properties. As a linear thermoplastic, polyetheretherketone can be melt-processed in the temperature range of approximately 370 to approximately 420 °C. No corrosive gases are produced during the processing of polyetheretherketone.

[0070] The base polymer may be present in the composition in an amount in a range from about 90% by weight to about 99% by weight, from about 95% by weight to about 99% by weight, or from about 96% by weight to about 98.5% by weight.

[0071] The conductive filler can be electrically conductive. The conductive filler can be both electrically and thermally conductive. The conductive filler can be selected from the group consisting of carbon nanotubes, graphene, graphene oxide, carbon nanofibers, and other carbon nanostructures. Graphene oxide can be reduced graphene oxide. Carbon nanotubes can enhance mechanical properties, such as stiffness and strength, electrical conductivity, and thermal conductivity. Nano-additives in wafers, such as graphene, can affect stiffness and strength, barrier properties, and can impart electrical and thermal conductivity. In one particular embodiment, the conductive filler consists of carbon nanotubes.

[0072] Electrically conductive fillers may be present in the composition in an amount ranging from approximately 0.25% by weight to approximately 5% by weight, from approximately 0.5% by weight to approximately 4% by weight, from approximately 0.5% by weight to approximately 3% by weight, or from approximately 0.5% by weight to approximately 2% by weight, or from approximately 1% by weight to approximately 2% by weight, or < 5% by weight, < 4% by weight, < 3% by weight, or < 2% by weight. Lower loading may help to preserve the properties of the base polymer.

[0073] The dielectric charge can be chosen from the group consisting of sublimated silica, sublimated alumina, nano-alumina, nano-silica, platelets of Boron nitride, boron nitride nanoflakes, boron nitride nanotubes, ZnO, and TiO2. In one particular embodiment, the dielectric filler is sublimed silica. Nano-alumina fillers can be used to improve the dielectric permittivity, direct current (DC) volume resistivity, and DC breakdown resistance of the composite polymer. The dielectric filler can be present in the conductive composite composition in an amount ranging from approximately 0% to approximately 3% by weight, 0.05% to approximately 3% by weight, 0.1% to 2% by weight, or approximately 0.5% to approximately 1.5% by weight of the composition.

[0074] Dispersion and processing additives can be selected from the group consisting of polyhedral oligomeric silsesquioxanes (POSS), silanes, and silanol-POSS. The dispersion additive can be used to improve the dispersion of the additives throughout the polymer matrix. For example, polyhedral oligomeric silsesquioxane (POSS) can be used alone as an additive, e.g., Octalsobutyl POSS, TriSilanolPhenyl POSS, TriSilanolIsobutyl POSS, or as a flux or dispersion additive (e.g., silanol-POSS). POSS compounds can be purchased commercially, e.g., from Hybrid Plastics. In a specific composition, the dispersion and processing additive is POSS.Dispersion and processing additives may be present in the composition in quantities ranging from approximately 0.1% by weight to approximately 5% by weight, from approximately 0.3% to approximately 5.0% by weight, from approximately 0.5% by weight to approximately 3% by weight, and from approximately 0.5% by weight to approximately 2.0% by weight.

[0075] In some embodiments, the above-combined conductive and dielectric fillers may be used in a range of 0.1 wt% to 5 wt% in combination while maintaining the overall wt% of the fillers < 5 wt%, < 4 wt%, or < 3 wt% to achieve the improvement in properties.

[0076] The improvement in properties obtained with the nanocomposite polymer of the invention compared to the base polymer may include an increase in tensile strength of at least about 1.1x, or from about 1.1x to about 1.25x; an increase in toughness of at least about 1.5x, or from about 1.5x to about 3x; an increase in impact resistance of at least about 1.5x, or from about 1.5x to about 3x; and an increase in elongation at break of at least about 1.5x, or from about 1.5x to about 3.5x.

[0077] Electrically conductive composite polymers can be processed, for example, by injection molding or extrusion processes. The composite polymer materials of the invention exhibit comparable or superior strength and higher toughness than the comparative basic PEEK materials. or commercially available comparative PEEK and carbon nanotube composite materials. The composite polymers of the invention retain the ductility of the base PEEK polymer and do not become brittle like commercially available PEEK-NTC polymers. The composite polymers of the invention are easy to post-process, for example, by tube bending, machining, and the like, without the fracture problem due to brittleness typically observed with several commercially available PEEK-NTC composites.

[0078] A lightweight, non-metallic fuel tube is proposed, comprising at least one layer prepared from a composition of the invention. The non-metallic tube can exhibit a controlled electrical resistance of between 100 kQ and approximately 100 MQ / 15", an operating pressure of 120 psi between -65 °F and 275 °F continuous, and up to 325 °F at the outlet. The non-metallic tube conforms to the (environmental) DO-160 standard of the Radio Technical Commission for Aeronautics (RTCA). The electrical resistance can be measured as a surface resistance.

[0079] In this description, tensile strength, tensile modulus of elasticity, and elongation at break are measured according to ASTM D638 or ISO 527, for example, using the Instron 3369 machine. Toughness is measured as the area under the stress-strain curve. Impact strength is determined according to ASTM D 256; the impact on a notched bar according to Izod is measured using the Ceast 9000. Thermal conductivity can be measured using a TPS 2500 instrument. Surface resistivity and volume resistivity can be measured according to ASTM D257 and IEC 62631-3-1; electrical conductivity is measured according to ASTM D257 and D4496; and thermal conductivity is measured using a transient hot-plate source method with a TPS2500 ThermTest.Tensile fatigue can be measured according to the test method of ASTM D3479 for the fatigue-tension of polymer matrix materials.

[0080] Compositions

[0081] The conductive composite polymer of the invention can be prepared from a composition according to Table 1.

[0082] [Table 1] Compositions of the invention Component Formula 1 Formula 2 Formula 3 Base Polymer 90-99% by weight 95-98.9% by weight 96-98.5% by weight Conductive Filler 0.25-5.0% by weight 0.5-3% by weight 0.5-2.0% by weight Dielectric Filler 0-3.0% by weight 0.1-2% by weight 0.25-1.5% by weight Dispersion and Treatment Additive 0.25-5.0% by weight 0.5-3% by weight 0.5-2.0% by weight Examples

[0083] Example 1

[0084] Six comparative samples and three samples of the invention are prepared. A first comparative base PEEK 1 sample is prepared using commercially available Victrex 450G PEEK. A second comparative base PEEK 2 sample is prepared using a commercially available Evonik 5000G PEEK kit. Four comparative NTC composite PEEK samples are prepared from: PEEK RTP 2299 X 115090 L (RTP Plastics, Winona, MN), which is a PEEK comprising ESD-shielded carbon nanotubes; RTP 2299 X 115090 M, which is a PEEK comprising ESD-shielded carbon nanotubes; RTP 2299 X 115092 A, which is a PEEK comprising ESD-shielded carbon nanotubes; and TECAPEEK ELS nano black (Ensinger) which comprises the PEEK VICTREX 450 G polymer and carbon nanotubes. Sample compositions of the invention are shown in Table 2.

[0085] [Table 2] Conductive composite polymer compositions of the invention PEEK ESD 1 PEEK ESD 2 (Formula 1) PEEK ESD 2 (Formula 2) Component % by weight Component % by weight Component % by weight Base polymer PEEK Victrex 450G 97.75 PEEK Evonik 5000G 97.75 PEEK Evonik 5000G 97.00 Conductive filler Carbon nanotubes 1.25 Carbon nanotubes 1.25 Carbon nanotubes 1.00 Dielectric filler Sublimated silica - Sublimated silica - Sublimated silica 1.00 Dispersion and treatment additive Silsesquioxane polyhedral oligomer (POSS) 1.00 POSS 1.00 POSS 1.00

[0086] The samples are prepared first by drying the additives and the polymer to remove residual moisture and by dry mixing the components to form a uniform mixture. The mixture is introduced into the hopper of a twin-screw extruder at a temperature of approximately 380 °C to approximately 425 °C and a screw speed of approximately 100 rpm to 800 rpm.

[0087] The molten strands of the polymer composite are then soaked in water and formed into composite pellets from 1 mm to 3 mm in size. To produce samples and test tubes, the pellets are dried and then injection molded into various shapes and sizes, or extruded. The tensile properties of the resulting samples are measured according to ASTM D638, the impact properties are measured according to ASTM D256, the electrical conductivity is measured according to ASTM D257 and D4496, and the thermal conductivity is measured using a transient hot-plate source method with a TPS2500 ThermTest.

[0088] Tensile strength

[0089] Tensile strength is measured according to ASTM D638 using the Instron 3369. Samples of comparative base PEEK 1 (PEEK Victrex 450G), comparative base PEEK 2 (PEEK Evonik 5000G), a PEEK 1 composite polymer sample of the invention, a PEEK 2 composite polymer sample of the invention, and four comparative samples of commercial PEEK-NTC are prepared and tested according to ASTM D638 for tensile strength (MPa) at room temperature. Figure 3 shows a bar graph of tensile strength (MPa) data at room temperature for the comparative base PEEK 1, the comparative base PEEK 2, and the composite polymer sample. PEEK 1 of the invention, PEEK 2 composite polymer sample of the invention, and four comparative commercial PEEK-NTC samples. The composite polymer samples of the invention exhibit slightly higher tensile strength than the comparative basic PEEK samples. The composite polymer samples of the invention exhibit comparable or slightly higher tensile strength than the comparative commercial PEEK-NTC samples. The samples of the invention and one commercial conductive PEEK-NTC sample exhibit a tensile strength > 100 MPa at room temperature according to ASTM D 638. The tensile strength can be 100 MPa or more.

[0090] Elongation at break

[0091] Elongation is measured according to ASTM D638 using the Instron 3369. Samples of comparative basic PEEK 1 (Victrex PEEK), comparative basic PEEK 2 (Evonik PEEK), a PEEK 1 composite polymer sample of the invention, a PEEK 2 composite polymer sample of the invention, and four comparative commercial PEEK-NTC samples are prepared and tested according to ASTM D638 for elongation at break (%) at room temperature. Figure 4 shows a bar graph of elongation at break (%) at room temperature. The elongation at break is > 20% for each of the comparative basic PEEK 1 and basic PEEK 2 samples. The elongation at break is > 30% for the PEEK 1 composite polymer sample of the invention, and > 80% for the PEEK 2 composite polymer sample of the invention. However, the four commercial PEEK samples with conductive NTC filler exhibit an elongation at break < 4%.

[0092] Tenacity

[0093] Toughness is calculated as the area under the tensile stress-strain curve. Figure 5 shows a stress-strain data graph for two different formulations of the PEEK 2 composite polymer samples of the invention and the comparative PEEK 2 sample. Tensile stress (MPa) is plotted against tensile strain (mm / mm) to obtain the stress-strain curves.

[0094] The PEEK 2 composite polymer formula 2 sample of the invention exhibits a stress-strain curve indicating that the sample is strong and ductile, and the PEEK 2 composite polymer formula 1 sample of the invention exhibits a stress-strain curve indicating that the sample is strong and tough, while the comparative basic PEEK 2 sample exhibits a stress-strain curve indicating that the sample is strong and brittle.

[0095] Figure 7 shows a bar graph of the strain energy at break (MPa) for the comparative basic PEEK 1 and basic PEEK 2 samples, the PEEK 1 formula sample of the invention, and the PEEK 2 formula sample of the invention. The samples of the invention exhibit increased toughness compared to the comparative basic PEEK 1 and basic PEEK 2 samples. The strain energy at break can be 18 MPa or more, as shown in Figure 7.

[0096] Mechanical properties

[0097] Tensile strength is measured according to ASTM D638 using the Instron 3369. Figure 6 shows a bar graph of mechanical properties including maximum tensile strength (MPa) and elongation at break (%) for the comparative basic PEEK 1, comparative basic PEEK 2, the PEEK 1 formula sample of the invention, and the PEEK 2 formula sample of the invention. The samples of the invention exhibit a similar or slightly higher maximum tensile strength (101.5 MPa, 104.1 MPa respectively) than that of the comparative basic PEEK 1 (98.7 MPa) and basic PEEK 2 (93.6 MPa) samples. The maximum tensile strength can be 100 MPa or more, as shown in Figure 6. The samples of the invention show a significantly higher elongation at break (%), more than 2 times or more than 3 times greater than that of the comparative basic PEEK 1 and basic PEEK 2 samples.

[0098] Tensile strength

[0099] Tensile strength is measured according to ASTM D638 using the Instron 3369. Figure 8 shows a bar graph of tensile strength (MPa) at three temperatures (-65°F, 73°F, 275°F) for comparative basic PEEK 1 and basic PEEK 2 samples and samples of the PEEK 1 composite polymer of the invention and the PEEK 2 composite polymer of the invention. Comparable tensile strength exists at each of the three temperatures between the comparative PEEK 1 and PEEK 2 composite polymers and the polymer of the invention. The tensile strength at -65°F can be 140 MPa or more. The tensile strength at 73°F can be 90 MPa or more. The tensile strength at 275°F can be 50 MPa or more, as shown in Figure 8.

[0100] Tensile modulus of elasticity

[0101] The tensile modulus of elasticity is measured according to ASTM D638 using the Instron 3369. Figure 9 shows a bar graph of the tensile modulus of elasticity (GPa) at three temperatures (-65°F, 73°F, 275°F) for comparative basic PEEK 1 and basic PEEK 2 samples and samples of the PEEK 1 composite polymer of the invention and the PEEK 2 composite polymer of the invention. A comparable tensile modulus of elasticity exists at each of the three temperatures between the comparative PEEK 1 and PEEK 2 composite polymers and the polymer of the invention. The modulus The tensile strength at -65 °F can be 4.5 GPa or more. The tensile modulus at 73 °F can be 4.0 GPa or more. The tensile modulus at 275 °F can be 3.5 GPa or more, as shown in [Fig. 9].

[0102] Shock resistance of samples

[0103] Impact resistance on a notched bar is measured using the Ceast 9000 and according to ASTM D266. [Fig. 10] shows a bar graph of impact resistance (Izod on notched bar) at three temperatures -65 °F, 73 °F, and 275 °F for samples of comparative base PEEK 2 and PEEK 2 + NTC-2 of the invention. The samples of the invention show significantly improved impact resistance of at least about 2 times or more that of the comparative base PEEK samples at each of the three temperatures. The base PEEK sample broke or partially dislocated at high temperature. [Fig. 11] is a photograph of the comparative base PEEK 2 samples where the samples broke or dislocated at high temperature at 275 °F in the impact resistance test (Izod on notched bar). Impact resistance (Izod on notched bar) at -65°F can be 15 KJ / m2 or more.Impact resistance (Izod on notched bar) at 73°F can be 16 kJ / m² or more. Impact resistance (Izod on notched bar) at 275°F can be 100 kJ / m² or more.

[0104] Impact resistance test - Tube level

[0105] A sample casing with an outside diameter of 2 inches and a wall thickness of 0.05 inches is prepared from the PEEK 1 composite polymer material of the invention (comprising Victrex PEEK) and the PEEK 2 composite polymer material of the invention (comprising Evonik PEEK). Impact resistance is determined according to ASTM D 256, impact test on a notched bar according to Izod, and measured using the Ceast 9000. Photographs after the impact resistance test of the PEEK 1 and PEEK 2 composite polymer casing samples of the invention are shown in [Fig. 12A] and [Fig. 12B], respectively. The PEEK 1 and PEEK 2 composite polymer tubes of the invention show no signs of failure after a 35 J shock. The PEEK 2 composite polymer sample tube of the invention survives shocks of 35 J and 50 J, finally failing at a 65 J shock. After the shock resistance test, the tubes are subjected to stamping and rupture pressures.Both sets of tubes ruptured at ~410 psi but did not fail at the point of impact.

[0106] Traction fatigue

[0107] Tensile fatigue tests are performed at room temperature, 5 Hz and 73 MPa on a comparative base PEEK material sample, a PEEK ESD composite polymer sample with lower toughness and a PEEK ESD composite polymer with high toughness. The PEEK ESD composite polymer with high toughness The high-performance conductive composite polymer exhibits tensile fatigue comparable to that of the comparative base PEEK sample as shown in [Fig. 13]. The conductive composite polymer can exhibit tensile fatigue at room temperature, 5 Hz, 73 MPa, at 2,200,000 fatigue cycles or more.

Claims

Demands

1. Solid polymer conductive composite material, prepared from a composition comprising 90-99 wt% polyetheretherketone (PEEK), 0.25% to 5 wt% conductive filler and 0.25% to 5 wt% dispersion and processing additive, wherein the dispersion and processing additive is selected from polyhedral oligomeric silsesquioxane silanes (POSS), silanes, and silanol-POSS.

2. Solid polymer conductive composite material according to claim 1, further comprising from 0.05% to 3% by weight of a dielectric filler.

3. Solid polymer conductive composite material according to claim 1, wherein the PEEK polymer is a PEEK polymer having a molten viscosity between 300 Pa.s and 500 Pa.s.

4. Solid polymer conductive composite material according to claim 1, wherein the conductive filler is selected from the group consisting of graphene, graphene oxide, and carbon nanostructures.

5. Solid polymer conductive composite material according to claim 4, wherein the carbon nanostructures are carbon nanotubes and / or carbon nanofibers.

6. Solid polymer conductive composite material according to claim 1, wherein the POSS is selected from the group consisting of Octalsobutyl POSS, TriSilanolPhenyl POSS, and TriSilanolIsobutyl POSS.

7. Solid polymer conductive composite material according to claim 2, wherein the dielectric charge is selected from the group consisting of nano alumina, nano silica, sublimated alumina, sublimated silica, ZnO, boron nitride nanotubes, boron nitride platelets, boron nitride nanoflakes, and TiO2.

8. Solid polymer conductive composite material according to claim 1, comprising 95% by weight to 99% by weight of a basic polyetheretherketone (PEEK) polymer.

9. Solid polymer conductive composite material according to claim 1, comprising 0.25% by weight to 3% by weight of the conductive charge, in which the conductive charge is an electrically conductive charge.

10. Solid polymer conductive composite material according to claim 1, comprising 0.3 wt% to 5 wt% of dispersion and processing additives.

11. Solid polymer conductive composite material according to claim 2, comprising 0.1 wt% to 2 wt% of the dielectric filler.

12. Solid polymer conductive composite material according to claim 2, prepared from a composition comprising 95 to 98.5% by weight of a PEEK polymer; 0.5 to 3.0% by weight of a conductive filler; 0.25 to 2% by weight of a dielectric filler; and 0.5 to 3.0% by weight of a dispersion and processing additive.

13. Solid polymer conductive composite material according to claim 12, wherein the total amount of combined fillers does not exceed 5% by weight.

14. 14. Solid polymer conductive composite material according to any one of claims 1 to 11, having one or more properties selected from the group consisting of a tensile strength at room temperature (73 °F) of at least 80 MPa; an elongation at break of at least 20%; an electrical resistance between 105 Q and 108 Q; a maximum tensile strength of at least 95 MPa or more; a strain energy at break of at least 15 MPa or more; and an Izod impact resistance on notched bar of at least 60 KJ / m2 or more.

15. 15. Non-metallic fuel transport circuit component for an aircraft, prepared from the conductive polymer composite material according to claim 1.

16. 16. Part according to claim 15, selected from the group consisting of a fuel tube, a hose, a coupling, a clamp, a conduit, a reducer, a flange, a ferrule, a support and a housing.

17. 17. Non-metallic fuel tube comprising at least one layer prepared from the polymer conductive composite material according to claim 1.

18. 18. Fuel tube according to claim 17, wherein the polyetheretherketone (PEEK) polymer is a PEEK polymer having in the molten state a viscosity between 300 Pa.s and 500 Pa.s.

19. 19. Fuel tube according to claim 17, wherein the fuel tube has an electrical resistance between 100 KQ and 100 MQ / 15”; a maximum operating pressure of at least 120 psi; a continuous operating temperature of -65 °F or less than at least 275 °F; an outlet operating temperature of at least 325 °F; and compliance with RTCA DO-160 environmental standards.

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