Polyamide-6-graphene composite material and assembly for hydrogen storage and / or transport

Abstract

The present patent disclosure concerns an assembly (100) for hydrogen storage and / or transport, the assembly comprising a hollow solid body (101); and at least one hydrogen barrier lining (102), wherein the at least one hydrogen barrier lining (102) is a blow moulded hydrogen barrier lining (102) made of a polyamide-6-based composite material comprising a polyamide-6-based matrix and graphene in an amount of 0.1-10 wt% of the polyamide-6-based composite material. Further disclosed are a blow moulded product made of the polyamide-6-based composite material and the polyamide-6-based composite material comprising a polyamide-6-based matrix and graphene in an amount of 0.1%-10% in weight per weight of the polyamide-6-based composite material, having a melt flow rate of at most 13 g / 10 min as measured according to ISO 1133-1 at a temperature of 250 °C with a weight of 16.6 kg.

Description

[0001] POLYAMIDE-6-GRAPHENE COMPOSITE MATERIAL AND ASSEMBLY FOR HYDROGEN

[0002] STORAGE AND / OR TRANSPORT

[0003] The present patent disclosure is within in the field of hydrogen transport and storage and polyamide-6- based materials for such transport and storage. Particular embodiments concern a polyamide-6-based composite material, a blow-moulded product made of a polyamide-6-based composite material, an assembly for hydrogen storage and / or transport, a method for manufacturing such assemblies, use of the polyamide-6-based composite material and a method of producing a polyamide-6-graphene composite material.

[0004] In recent years there has been an increased interest in the use of hydrogen as in fuel cells to create electrical energy. Provided that the green hydrogen is created in a process that does not produce carbon dioxide it can be regarded as a zero-carbon electricity source.

[0005] For hydrogen to reach its full potential as a clean energy source, however, the hydrogen will need to be transported to where it is to be used, which could be far away. For example, hydrogen may have to be transported from hydrogen production sites to factories, or inside different vehicles such as cars, trucks, and buses where hydrogen can be used as a fuel. Hydrogen also needs to be stored at sites in large volume systems. Due to its small molecular size, it is challenging to transport and store hydrogen, both in its liquid and gaseous state. It is highly permeating and therefore hard to enclose.

[0006] In addition, numerous reports have discussed the problem with increased amounts of hydrogen emitted to the atmosphere. It has been discussed that hydrogen in the atmosphere affects other substances such as methane, ozone, and water vapour. This results in hydrogen to be considered as an indirect greenhouse gas with an estimated global warming potential of 5.8 over a 100-year time horizon. Therefore, hydrogen leakage into the atmosphere is unwanted and is a potential risk for a hydrogen economy of substantial size.

[0007] Due to weight restrictions, type IV pressure vessels where a polymer liner or lining is wrapped with carbon fiber-reinforced polymers (CFRP) are increasingly replacing type III pressure vessels where a metal liner is wrapped with CFRP. High-density polyethylene (HDPE) is used as a liner material for type IV hydrogen storage, because of its use in the field of natural gas storage / transport and its known good performance. Polyamides are emerging as alternatives to polyethylene due to their lower hydrogen permeability and greater mechanical strength compared to HDPE. However, the still relatively high hydrogen permeability and low mechanical strength of polymers limits commercialization of polymer- based pressure vessels. US 2022 / 0003362 according to its abstract states that a plant for delivering hydrogen includes a hydrogen tank and at least one pipe for delivering hydrogen. At least one surface of the hydrogen tank or the hydrogen delivery pipe is covered with a two-dimensional material mixed with a polydopamine- type polymer.

[0008] WO 2021072357 Al according to its abstract states that a graphene-reinforced polyamide composite material and a process to make the material are provided. The graphene-reinforced polyamide composite material has graphene-based nanofillers dispersed in polyamide resins during a melt compounding manufacturing process. The graphene-based nanofillers are selected from a group of single-layer graphene, double-layer graphene, multi-layer graphene, graphene nanoplatelet, doped graphene, graphene oxide, reduced graphene oxide, and a combination thereof. This patent document is unrelated to the field of hydrogen storage and / or transport.

[0009] It is an object, among objects, to provide improved materials that can be used in, or for manufacturing of, assemblies for hydrogen storage and / or transport.

[0010] To this end, in accordance with a first aspect, there is provided a blow moulded product made of a polyamide-6-based composite material comprising a polyamide-6-based matrix and graphene in an amount of 0.1-10 wt%, or 0. 1-8 wt%, of the polyamide-6-based composite material.

[0011] These materials advantageously exhibit a decreased hydrogen permeability compared to polyamide-6 without added graphene. In addition, the blow moulded product shows a decreased hydrogen permeability compared to extruded samples with the same polyamide-6-based composite material. This is especially beneficial for blow-moulded products with a hydrogen barrier function, such as hydrogen barrier linings.

[0012] Graphene is a 2-dimensional carbon material. Graphene is a layered material in the form of flakes or sheets. Graphene comprises at least 30 at% carbon, has a hexagonal lattice and a thickness 1-20 times the size of a carbon atom. Herein the term ‘graphene’ may refer to single layer graphene, few layers graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene nanoplatelets (GNP), doped graphene, chemically functionalized graphene, etc.

[0013] In an embodiment, the graphene is selected from the group consisting of single layer graphene, few layers graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene nanoplatelets (GNP), doped graphene, chemically functionalized graphene, and any combination thereof.

[0014] In an embodiment, the graphene is reduced graphene oxide (rGO) or graphene oxide (GO). These types of graphene are more readily dispersible in the polymer matrix than other types of graphene, such as GNP, especially when using techniques like extrusion for the dispersing of the graphene into the polymer matrix. It is found that rGO is safer and easier to process than GO, in particular for processes where the temperature is elevated, such as extrusion, because the GO may undergo an exothermic reduction reaction during such processing. Furthermore, rGO results in a safer polyamide-6-graphene composite material for applications with hydrogen, because of its electrostatic discharge properties, contrary to GO. rGO furthermore is expected to yield higher electrical conductivity than GNPs.

[0015] In an embodiment, the polyamide-6-based composite material comprises graphene in an amount of 0.1- 7.5 wt% of the polyamid-6-based composite material.

[0016] In an embodiment, the polyamide-6-based composite material comprises graphene in an amount of 0. 1- 6 wt% of the polyamid-6-based composite material.

[0017] In an embodiment, the polyamide-6-based composite material comprises graphene in an amount of 0.2- 3 wt% of the polyamid-6-based composite material.

[0018] In an embodiment, the polyamide-6-based composite material comprises graphene in an amount of 0.3- 0.8 wt% of the polyamid-6-based composite material.

[0019] In an embodiment, the graphene is distributed in the polyamide-6-based matrix.

[0020] In an embodiment, the graphene is uniformly distributed in the polyamide-6-based matrix.

[0021] In an embodiment, a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based composite material is reduced by at least 20%, preferably at least 30%, more preferably at least 40% compared to a blow moulded blow moulding grade polyamide-6 material.

[0022] In an embodiment, the blow-moulded product has a tensile modulus as measured according to ISO 527- 2 at 23 °C that is increased by at least 20%, preferably 50%, compared to neat polyamide-6.

[0023] In an embodiment, the blow-moulded product has a Charpy notched impact strength of at least 15, preferably at least 20 kJ / m2as measured according to ISO 179-1:2020 performed at a temperature of 23 °C with a 25 J impact.

[0024] In an embodiment, the blow moulded product is a blow moulded hydrogen barrier lining for lining of a hydrogen storage means or hydrogen transport means. The present patent disclosure may further relate to a product, such as a hydrogen barrier lining, obtainable or obtained by a blow moulding process, wherein the product is made of a polyamide-6- based composite material comprising a polyamide-6-based matrix and graphene in an amount of 0.1- 10 wt%, or 0.1-8 wt%, of the polyamide-6-based composite material. This product may be the blow moulded product. The composite material described below may be used to obtain the product.

[0025] According to a second aspect, there is provided a polyamide-6-based composite material for blowmoulding, the polyamide-6-based composite material comprising a polyamide-6-based matrix and graphene in an amount of 0. l%-10%, or 0.1% to 8%, in weight per weight of the polyamide-6-based composite material, and optionally having a melt flow rate of at most 13 g / 10 min as measured according to ISO 1133-1 at a temperature of 250 °C with a weight of 16.6 kg.

[0026] These materials advantageously exhibit a decreased hydrogen permeability compared to polyamide-6 without added graphene.

[0027] Beneficially, this polyamide-6-based composite material is suitable for blow moulding, a technique that is applicable for making products such as hydrogen barrier linings. When the material is blow moulded, the hydrogen permeability is even further reduced compared to extruded samples of the same material.

[0028] In an embodiment, the graphene is selected from the group consisting of single layer graphene, few layers graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene nanoplatelets (GNP), doped graphene, chemically functionalized graphene, and any combination thereof. In an embodiment, the graphene is reduced graphene oxide (rGO) or graphene oxide (GO).

[0029] In an embodiment, the melt flow rate lies in a range of 5 to 13 g / 10 min, preferably 6-12 g / 10 min, as measured according to ISO 1133-1 at a temperature of 250 °C with a weight of 16.6 kg. These ranges are especially suitable for blow moulding applications.

[0030] In an embodiment, the polyamide-6-based composite material comprises neat polyamide-6, a blow moulding grade polyamide-6 polymer material, the graphene, and optionally a first impact modifier. These mixtures may be prepared by blending or extrusion, for example with a twin screw extruder.

[0031] In the present patent disclosure, the blow moulding grade polyamide-6 may be a polyamide-6 based polymer for blow moulding comprising additives, such as a stabilizer, such as carbon black, and / or one or more second impact modifiers, such as maleic anhydride and ethylene / 1 -butene copolymer. The stabilizers may comprise one or more reinforcement agents, one or more heat stabilizers, one or more thermo-oxidation preventing stabilizers, and / or one or more UV stabilizers. The polyamide-6 based polymer for blow moulding may comprise the impact modifiers in a concentration of 1-30 wt%, for example 5-25 wt% or 10-25 wt%, per total weight of the polyamide-6 based polymer for blow moulding. The polyamide-6 based polymer for blow moulding may have a melt flow rate in the range of 0.1 - 15 g / 10 min, when measured according to ISO 1133-1 with a weight of 16.6 kg and at a temperature of 250 °C. Commercially available examples of suitable blow moulding grades polyamide-6 are Durethan BC550Z (Lanxess), Akulon® Fuel Lock FLE40-HP (Envalior), Akulon® Fuel Lock FLX-LP (K-X08836), Akulon® Fuel Lock FLE-LP BK29011, Akulon® Fuel Lock FLX40- HP(K-X09022), Technyl Shape C 548B BK (Domo), Technyl Shape C 550 BCR (Domo) and UBE Nylon 1218IU (UBE). Commercially available suitable impact modifiers comprise Elastron G (Elastron TPE) from Elastron, FUSABOND N493 and FUSABOND N525 Functional Polymer (DOW) and Surlyn 9320 (DOW). Elastron TPE is known to increase the impact strength of thermoplastics such as polyamides. As an example, Elastron TPE additions of 8 wt% have been shown to increase the impact strength of polyamide from 5.3 to 14 kJ / m2.

[0032] In an embodiment, the blow moulding grade polyamide-6 comprises 46-99 wt% polyamide-6 and 1- 54wt% additives.

[0033] In an embodiment, of the 1-54 wt% of additives, there is 1-20 wt% of one or more stabilizers, 0-30 wt% of the second impact modifier, and 0-4 wt% of the other additives.

[0034] In an embodiment, the blow moulding grade polyamide-6 comprises 46-97.5 wt% polyamide-6, 1-20 wt% of the stabilizers, 1-30 wt% of the second impact modifier, and 0.5-4 wt% of the other additives.

[0035] If the blow moulding grade polyamide-6 comprises the second impact modifier, the optional first impact modifier is then an additional impact modifier. The amount of first impact modifier in the polyamide- 6-based composite material may be 0.5 - 10 wt% in weight per weight of the polyamide-6-graphene composite material. A total amount of impact modifier, including respective amounts of the first and second impact modifier, may lie in the range of 1 - 30 wt%, such as 15-25 wt%.

[0036] The second impact modifier may be the same impact modifier as the first impact modifier, or they may be different. The first impact modifier may comprise a single impact modifier substance or may comprise a mixture of impact modifier substances. The second impact modifier may comprise a single impact modifier substance or may comprise a mixture of impact modifier substances.

[0037] In an embodiment the other additives may comprise one or more of known injection moulding supporting compounds for better release from moulds, improved mixing of the polymer matrix, polymer stabilizing compounds, processing aids, colour pigments, and flame retardants. A compound for better release from moulds may be a mould release lubricant. Processing aids may help the flow of the polymer during moulding to avoid shearing. The blow moulding grade polyamide-6 material may comprise 0.5 wt% to 1 wt% of processing aid, in weight per weight of the blow moulding grade polyamide-6 material.

[0038] In an embodiment the polyamide-6-based composite material comprises graphene in an amount of 0. l%-7.5% in weight per weight of the polyamide-6-based composite material.

[0039] In an embodiment, the amount of graphene in the polyamide-6-based composite material is 0. l%-6% in weight per weight of the polyamide-6-based composite material.

[0040] In an embodiment, the amount of graphene in the polyamide-6-based composite material is 2%-10%, preferably 2%-8%, more preferred 3%-7.5%, in weight per weight of the polyamide-6-based composite material.

[0041] In an embodiment, a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based composite material is reduced by at least 5%, preferably at least 10%, more preferably at least 30% compared to neat polyamide-6.

[0042] In an embodiment, when the amount of graphene in the polyamide-6-based composite material is 2%- 10%, preferably 2%-8%, more preferred 3%-7.5%, in weight per weight of the polyamide-6-based composite material, the hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based composite material is reduced by at least 30% compared to neat polyamide-6.

[0043] In an embodiment, the polyamide-6-based composite material has a tensile modulus as measured according to ISO 527-2 at 23 °C that is increased by at least 20%, preferably 50%, compared to neat polyamide-6.

[0044] In an embodiment, the polyamide-6-based composite material has an ultimate strength as measured according to ISO 527-2 at 23 °C of at least 55 MPa.

[0045] In an embodiment, the polyamide-6-based composite material has an ultimate strength as measured according to ISO 527-2 at 23 °C that is increased by at least 10%, preferably 20%, more preferred 24% compared to neat polyamide-6. According to a third aspect, there is provided an assembly for hydrogen storage and / or transport, the assembly comprising a hollow solid body; and at least one blow moulded hydrogen barrier lining as described above.

[0046] In an embodiment, the surface of the hollow solid body is an inner surface of the hollow solid body; the hollow solid body is a tank, a vessel, a pipe, a joint, or a cylinder.

[0047] In an embodiment, the assembly is a hydrogen storage container or a hydrogen transport container.

[0048] In an embodiment, the hydrogen storage container is a hydrogen storage tank, a hydrogen storage vessel, or a hydrogen cylinder.

[0049] In an embodiment, the hydrogen cylinder is a hydrogen gas cylinder; and / or the hydrogen transport container is a hydrogen transport pipe or a joint for joining hydrogen transport pipes; and / or the hollow solid body is a hollow stainless-steel body, a hollow carbon or glass fibre winded body, or a hollow polymer body.

[0050] In an embodiment, the hydrogen barrier lining is attached to the hollow solid body using an adhesive.

[0051] In an embodiment, the hydrogen barrier lining is attached to the hollow solid body in a binder-free manner.

[0052] According to a fourth aspect, there is provided a method for manufacturing an assembly for hydrogen storage and / or transport as described above and below, comprising lining a surface of the hollow solid body with one of the at least one hydrogen barrier linings.

[0053] According to a fifth aspect, there is provided use of a polyamide-6-graphene composite material as described above and below as a hydrogen barrier lining.

[0054] According to a sixth aspect, there is provided a method of producing a polyamide-6-graphene composite material for blow moulding, comprising: providing a first mixture of neat polyamide-6 or blow moulding grade polyamide-6 material, and graphene in an amount of 4-8 wt% of the first mixture; and diluting the first mixture with at least a blow moulding grade polyamide-6 material when the first mixture comprises the neat polyamide-6 or with at least neat polyamide-6 when the first mixture comprises the blow moulding grade polyamide-6 material, and optionally an impact modifier, such that the polyamide-6-graphene composite material (200) with a reduced amount of graphene compared to the first mixture is obtained.

[0055] Beneficially, this method allows for the tuning of properties of the produced polyamide-6-graphene composite material, the tuneable properties including, for example, the hydrogen permeability, the Melt Flow Rate, and the impact strength (e.g. Charpy notched impact strength).

[0056] In an embodiment, when the first mixture comprises the neat polyamide-6, the diluting comprises diluting 3-70 wt% of the first mixture with 30-97 wt% of blow moulding grade polyamide-6 material.

[0057] In an embodiment, when the first mixture comprises the blow moulding grade polyamide-6 material, the diluting comprises diluting 30-85 wt% of the first mixture with 15-70 wt% of the neat polyamid-6.

[0058] In an embodiment, the method further comprises adding 0.5 - 20 wt% of an impact modifier in weight per weight of the polyamide-6-graphene composite material.

[0059] In an embodiment, 0.5 - 15 wt%, preferably 5-15 wt% of an impact modifier in weight per weight of the polyamide-6-graphene composite material is added.

[0060] In an embodiment, the blow moulding grade polyamide-6 material comprises 15 to 30 wt% of an impact modifier in weight per weight of the blow moulding grade polyamide-6 material.

[0061] According to yet another aspect, there is provided the use of a polyamide-6-graphene composite material as described above and below comprising the graphene in an amount 2%-10%, preferably 2%- 8%, more preferred 3%-7.5%, in weight per weight of the polyamide-6-based composite material as a masterbatch composition.

[0062] According to a still a further aspect, there is provided a polyamide-6-based composite material comprising a polyamide-6-based matrix and graphene in an amount of 0.3%-0.8% in weight per weight of the polyamide-6-based composite material.

[0063] With these graphene concentrations, the composite materials exhibit enhanced mechanical properties. For example, the composite materials may exhibit a higher ultimate strength than outside of the graphene range. The impact strength for composites with graphene in the above mentioned range is further not reduced compared to a reference without graphene. At higher concentrations, on the other hand, the impact strength may be significantly reduced. In an embodiment, the polyamide-6-based composite material comprises the graphene in an amount of 0.3% - 0.5% in weight per weight of the polyamide-6-based composite material.

[0064] In an embodiment, the polyamide-6-based composite material comprises the graphene in an amount of 0.35% - 0.45% in weight per weight of the polyamide-6-based composite material.

[0065] It will be understood that technical advantages and effects associated with features and / or embodiments of one aspect, apply to the corresponding, similar, or equivalent features and / or embodiments the other aspects. It will also be apparent that the features of the various aspects and / or embodiments thereof may be applied to the other aspects and / or embodiments thereof.

[0066] Brief Description of the Drawings

[0067] The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of devices of the present disclosure. The above and other advantages of the features and objects of the disclosure will become more apparent, and the aspects and embodiments will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

[0068] Figure la is a schematic drawing of an embodiment of the assembly according to some examples of the present patent disclosure;

[0069] Figure lb is a schematic drawing of another embodiment of the assembly according to some examples of the present patent disclosure;

[0070] Figure 1c is a schematic drawing of an embodiment of the assembly according to some examples of the present patent disclosure;

[0071] Figure Id is a schematic drawing of an embodiment of the assembly according to some examples of the present patent disclosure;

[0072] Figure 2 is a schematic drawing of one embodiment of the polyamide-6-based material according to some examples of the present patent disclosure;

[0073] Figure 3A is a graph of Ft permeability [mol-m ’ s ’ -MPa1] as a function of graphene concentration [wt%] in polyamide-6-based composite materials according to some examples of the present patent disclosure;

[0074] Figure 3B is a graph of change in H2 permeability [%] as a function of graphene concentration [wt%] relative to neat polyamide-6 for the data shown in Fig. 3 A;

[0075] Figure 4 is a bar chart of H2permeability [mobm ' s ' MPa1] for various extruded and blow moulded compositions according to some examples of the present patent disclosure; Figure 5 is a graph of impact strength [kJ / m2] as a function of graphene concentration [wt%] of polyamide-6-based composite materials according to some examples of the present patent disclosure; Figure 6 is a graph of tensile modulus [MPa] as a function of graphene concentration [wt%] of the polyamide-6-based composite materials according to some examples of the present patent disclosure; Figure 7 is a graph of ultimate strength [MPa] as a function of graphene concentration [wt%] of polyamide-6-based composite materials according to some examples of the present patent disclosure; and

[0076] Figure 8 is a graph of average impact strength [kJ / m2] as a function of additional impact modifier content [wt%] of polyamide-6-based composite materials according to some examples of the present patent disclosure.

[0077] Abbreviations

[0078] GO - graphene oxide;

[0079] PA6 - polyamide-6; and rGO - reduced graphene oxide.

[0080] MFR - Melt Flow Rate

[0081] Detailed description

[0082] Assemblies for carrying or being in contact with hydrogen, such as storage containers and transport pipes and pipe joints, such as tanks, vessels, cylinders, etc. have requirements in terms of thermal endurance, mechanical strength, and gas permeability. Examples of storage containers include tanks, vessels, cylinders, cartridges, canisters, cages, and caves. Assemblies for hydrogen storage and / or transport as used herein can be open- or close-ended, it can also be open at one end but closed at the other.

[0083] Graphene is a 2-dimensional carbon material. Graphene is a layered material in the form of flakes or sheets. Graphene comprises at least 30 at% carbon and up to 100 at% carbon, has a hexagonal lattice and a thickness of 1-34 times the size of a carbon atom. In some examples, reduced graphene oxide (rGO) is used in the composite materials described herein. The rGO may comprise carbon in a range of 70 at% to 99 at%, preferably 90-98 at%. If, in any of the examples described below, rGO is used, then the rGO may be exchanged for GO or any other type of graphene as described above.

[0084] In Fig. 1 there is shown an assembly 100 comprising a hollow body 101 and at least one hydrogen barrier lining or liner 102. The at least one hydrogen barrier lining 102 may be at least one hydrogen gas barrier lining 102. The hydrogen barrier layer 102 comprises a polyamide-6-based composite material 200, comprising a polyamide-6-based matrix 202 and graphene 201 in an amount of 0.1%- 10% in weight per weight of the polyamide-6-based composite. In the polyamide-6-based composite material 200, the graphene201 may be distributed or dispersed in the polyamide-6 matrix 202.

[0085] A ‘lining’ 102 refers to a thin layer or coating provided on the surface of the hollow body 101. The lining 102 may have a thickness in the pm -cm range, for instance 0,1 pm - 1 cm. The hollow body 101 may have a thickness in the cm range, for instance 0.5 - 10 cm. The lining 102 can bond directly to the mechanically hollow body 101. Alternatively, an adhesive layer can be provided in between the hollow body 101 and the lining 102. A further alternative is that there is no adhesion or bonding to the hollow body 101, but that the lining 102 is present within the hollow body 101, such as when performing coextrusion. The liner or lining may be provided on the inner surface 101a of the hollow body 100.

[0086] In some examples, the adhesive layer may additionally comprise graphene, in such examples the graphene may provide advantageous properties to the adhesive such as for example increased mechanical strength.

[0087] One way of providing the liner or lining in or on the hollow body is by co-manufacturing techniques, such as co-extrusion. Another way of providing the liner or lining is by separately manufacturing the hollow body and the lining, and then providing the lining inside or outside the hollow body. It is an option to provide the lining by blow-moulding the polyamide-6-based composite. The lining may, for example, be used as an inner hydrogen container of a glass fiber or carbon fiber winded hydrogen tank.

[0088] In Figure 1A, the assembly 100 is embodied as a hydrogen storage container 100 with closed ends. The assembly 100 may comprise an opening (not shown) for allowing the hydrogen to enter and exit the assembly. This opening may be provided with means for attaching further components such as valves and / or pressure reducers and the like.

[0089] Figure 1A shows a schematic illustration of a hydrogen storage container 100 according to the invention. Such a container 100 can be used to store and / or transport hydrogen. Figure 1A shows a schematic longitudinal cross-section of a hydrogen storage container 100. As can be seen the hydrogen storage container 100 is composed of a hollow body 101, for example a hollow stainless-steel body or hollow carbon or glass fiber winded body, that is provided with a hydrogen barrier lining 102. Figure IB shows a cross-section along A-A of the hydrogen storage container 100 illustrated in Figure la.

[0090] The hydrogen storage container 100 may comprise more than one gas barrier lining 102 and / or more than one hollow body 101. A hydrogen storage container 100 can for example have two hollow bodies 101 and 101’, each provided with a hydrogen barrier lining 102 and 102’ as illustrated in Figure 1C. The hydrogen storage container 100 has an inner surface 100a and an outer surface 100b. The hollow body 101 has an inner surface 101a. The lining 102 is typically provided at the inner surface 101a of the hollow body as illustrated in Figures 1A-C. As such during use of a hydrogen storage container 100 the lining 102 is in direct contact with the hydrogen when present in the inside space 104 within the container 100. In the examples of assemblies 100 illustrated in Figures 1A-C, the outer surface 100b is the outer surface of the hollow body 101.

[0091] The cross sections of Figs. IB, 1C and ID can alternatively be schematic cross sections of a hydrogen transport pipe or pipe joint. The present patent disclosure concerns improving the hydrogen permeability properties of hydrogen carrying assemblies and / or hydrogen storage and / or transport assemblies by applying the polyamide-6-based composite material as a hydrogen barrier lining 102. In some examples, the hydrogen barrier lining 102 is blow-moulded.

[0092] Other examples of assemblies 100 includes three layers: an outer layer 100’, an inner layer 100”, and an intermediate layer 100’”. Such an example is illustrated in Fig ID. The assembly, in Fig. ID embodied as hydrogen storage container 100, comprises an inner layer 100” being a hydrogen barrier lining 102, an intermediate layer 100’” being a hollow body 101, and an outer layer 100’. The outer layer 100’ may be an additional hollow body, a layer or a lining that provides another function to the hydrogen storage container 100. For instancing, the additional hollow body, layer, or lining may provide improved corrosion resistance to the hollow body 101 when it is to be used in corrosive conditions, such as in sea water.

[0093] The hydrogen barrier lining 102 in all examples disclosed herein comprises a polyamide-6-based composite material 200 that comprises graphene 201 in a polyamide-6 matrix 202. The polyamide-6- based composite material 200 may also be referred to as polymer-graphene composite material. The polymer-graphene composite material 200 will be discussed in more detail below.

[0094] A hydrogen barrier lining 102 can be provided in the assembly by providing the hollow body, for example a stainless-steel tank, a carbon or glass fibre winded tank, a stainless-steel pipe, a polymer pipe, etc., with an inner lining of the graphene-based composite material 200. The lining can be made using for example extrusion, co-extrusion, injection moulding, rotational moulding, blow moulding or spray coating. When co-extruding, the hollow body is polymer based, and the lining and the hollow body can be made at the same time.

[0095] Extrusion of polymers is a processing technique wherein the polymer is melted and formed into a desired profile. The polymer is melted by heaters and by mechanical energy generated by screws used in the process. The polyamide-6-graphene composite material 101 can be manufactured by mixing polyamide-6 with rGO using for example an extruder.

[0096] In one aspect of the present patent disclosure there is provided a method for manufacturing an assembly for carrying hydrogen or an assembly for hydrogen storage and / or transport, wherein an inner surface 101a of a hydrogen storage container 100 is lined with, or coated with, the hydrogen barrier lining 102. Typically, the assembly 100 is manufactured by coating an inner surface of a hollow body with the polyamide-6-based composite material 200. The polyamide-6-based composite material 200 can be manufactured by mixing polyamide-6 with at least graphene (e.g. GO or rGO), using for example an extruder.

[0097] The polymer-graphene composite material 200 is schematically illustrated in Figure 2. As is schematically indicated in the Figure, the graphene 201 may be homogeneously or almost homogenously distributed throughout the polyamide-6 matrix 202. Without being bound by any theory, it is believed that the homogenous distribution of graphene 201 in the polyamide-6 matrix 202 is beneficial in terms of gas permeability. In other words, a lower gas permeation can be achieved for a polymer-graphene composite material 200 wherein the graphene 201 is distributed throughout the polyamide-6 matrix 202 as compared to a polyamide-6-based composite material wherein the graphene is more lumped together in parts of the composite material while less present in other parts of the composite material.

[0098] The polyamide-6 matrix 202 is made of polyamide-6 (PA6). Polyamide-6 is a polymer that is widely used and is also known as nylon-6. Polyamide 6 (PA6) or Nylon 6 is an 6-carbon chain polymer which can be produced by the ring-opening polymerization of caprolactam. PA6 can be processed using standard manufacturing techniques such as extrusion, blow moulding, rotational moulding, and injection moulding. PA6 advantageously has, compared to other PA grades and HDPE, a lower hydrogen permeability than other available polymers. As stated by Dong et al. in “Hydrogen Permeability of Polyamide 6 Used as Liner Material for Type IV On-Board Hydrogen Storage Cylinders”, Polymers 2023, 15, 3715. https : / / doi .org / 10,3390 / polvm 15183715. PA6 has slightly stronger hydrogen permeation resistance than PA11, while HDPE has the least resistance. One advantage of the present compositions, formulations and / or blow moulded products, is that permeability of hydrogen is further reduced compared to PA6 polymer in combination with improved tensile modulus and ultimate strength, allowing for decreased liner thickness, which can save cost or for further reduction of permeability. This in turn increases competitiveness towards metal-based liners.

[0099] One advantage of the assembly 100 is that less hydrogen leaks out from the assembly 100 compared to if no hydrogen barrier lining 102 is present. Additional improved properties of an assembly 100 according to the present patent disclosure can be increased conductivity and reduced electrostatic effects.

[0100] The hydrogen storage container 100 typically is configured to withstand both a wide range of temperatures and high pressure. For instance, in hydrogen transport, the hydrogen may be transported at pressures ranging from 1 bar to 100 bar, for instance 10 - 90 bar. In a hydrogen gas container, such as a hydrogen gas bottle, the hydrogen pressure may be up to 700 bar, with operating temperatures varying from -65 °C to 85 °C. Hence, the associated assemblies will be subjected to substantial mechanical load as well as thermal chock. The hollow body 101 may be configured to withstand pressures within these ranges.

[0101] As discussed earlier, the assembly 100 as discussed herein can be any type of container that is used to store and / or transport hydrogen in liquid and / or gaseous, pressurized gaseous form. Examples includes tanks, vessels, pipes, joints, cylinders, cartridges, etc.

[0102] The hydrogen gas barrier layer or lining 102 comprises the polyamide-6-based composite material 200. The amount of graphene in a polymer-graphene composite material 200 is 0.1 %-8 % in weight per weight of the composite, 0.1-7.5 % % in weight per weight of the composite, 0.1-6 % in weight per weight of the composite, 0.2-3% in weight per weight of the composite, 0.3-0.8% in weight per weight of the composite, or 0.4-7.5% in weight per weight of the composite. When the graphene is rGO or GO, the graphene may comprise 0.1-30 wt% of oxygen.

[0103] The rGO may be any type of rGO, or any type of graphene that has been first oxidized and then reduced to form rGO. rGO can be seen as a form of graphene oxide (GO) that is processed in order to reduce the oxygen content. The processing can be by chemical, thermal, or other methods known to persons skilled in the art.

[0104] Examples

[0105] The purpose of a hydrogen barrier lining 102 is to prevent or reduce the permeability of hydrogen through the walls of the assembly 100. Therefore, the hydrogen permeability was tested for various composites according to the present patent disclosure.

[0106] Preparation of samples with graphene as additive

[0107] A masterbatch (MB) PA6 composition comprising 7.6 wt% graphene relative to the total rate of the composition was processed in a 24-mm twin screw extruder where graphene (rGO with a carbon content > 97 at%) was fed through a side feeder to be mixed with the neat PA6 (Durethan B40F, Lanxess). Two sets of compositions were prepared. A first set of compositions were prepared by blending the MB PA6 with further neat PA6, in order to obtain a specific, lower, graphene concentration. A second set of compositions were compositions for blow moulding and were prepared by blending the MB PA6 composition with a blow moulding grade PA6 (Durethan BC550Z, Lanxess). Several of the second set of compositions further comprised additional impact modifier over the impact modifier already present in the blow moulding grade PA6.

[0108] The blends of both the first and second sets of samples were extruded with a twin-screw extruder to disperse the graphene. At least several of the blends of the second sets of compositions were, as an alternative, directly extrusion blow moulded, that is, the blending of MB PA6 composition and blowmoulding PA6 grade was done without the pre-extrusion using the twin screw extruder. The MB PA6 composition and blow-moulding PA6 grade was then mixed in the (single screw) extruder of the blow moulding device. The extruded composition then enters the blow-moulding device, forming the parison. These latter compositions are referred to as “blended”, while the former compositions are referred to as “extruded” or “pre -extruded”. All of the second set of samples (blended and pre-extruded) where then used to blow mould sample products or test specimens.

[0109] Table 1A Compositions ofPA6 and PA6-graphene samples.

[0110] Table 2B Compositions ofPA6 and PA6-graphene samples of Table 1A with concentrations of MB, BM grade PA6, additional impact modifier, neat PA6 and graphene. The weight percentages of graphene correspond to the graphene concentrations as obtained via TGA of Table 1A.

[0111] The carbon content (using TGA), Melt Flow Rate (MFR), the hydrogen permeability, tensile properties and impact strength were evaluated for extruded pellets and sheets. For blow-moulded parts, the hydrogen permeability, tensile properties and impact strength were evaluated. Blow moulding process

[0112] The blow moulding process comprised the following steps. The composition to be blow moulded was pre-dried for 24 hours and liners were blow moulded under a pressure of around 20 bars. The produced liners of the compositions according to the present patent disclosure exhibited an improved surface finish compared to a blow moulding reference (only blow moulding grade PA6), which contained lumps, probably of a filler. The pre-extruded liners had a better surface finish (less wavy than the blended liners).

[0113] Hydrogen gas permeability testing

[0114] Samples for hydrogen permeability of the extruded samples were prepared by sheet extrusion. Samples for hydrogen permeability of the blow-moulded samples were prepared by cutting the blow moulded parison in half and flattening it out. Then dog bones were milled out from the flattened parison. Permeation experiments were conducted in a permeation set-up along standard ASTM D 1434-82 (manometric, procedure M). Prior to the testing all samples were degassed in a vacuum furnace at 60 °C at 5 mbar for a minimum of 2 days. Testing proceeded for 1 day per sample, and was performed as follows:

[0115] The sample was installed in the cell. Vacuum overnight at the desired temperature (50°C) was applied to allow for an additional degassing of the sample. Subsequently, a vacuum test was performed for approximately 1 h to assure a sufficiently low degassing rate as this may otherwise be incorrectly assessed as permeating species.

[0116] Subsequently the upstream side of the sample was exposed to hydrogen at approximately 20 bars, and the downstream side was monitored until steady-state conditions were achieved.

[0117] The test provides direct measurement of permeability (stable permeation) and diffusivity (via the breakthrough / permeation curve). The solubility coefficient was calculated according to the solution / diffiision mechanism principle. Variation of sample thickness is taken into account in the calculations.

[0118] Mechanical property testing

[0119] Test pieces for mechanical property evaluation were prepared using compression moulding using a Fontijne Labtop 300 TMP005 & polished steel flash moulds according to ISO 293:2023 followed by water cutting of test specimens in form of bars.

[0120] The compression moulding was performed according to ISO 293:2023 by using flash moulds and a compression of 5 MPa at 240°C for PA6 followed by cooling with 10 °C / min. Test pieces were cut using waterjet cutting into dog bones and bars according to ISO 527-2 and ISO 179.

[0121] Test pieces were also prepared from blow-moulded liners by flattening the warm liner out right after blow-moulding and milling dog bones out of the liner. Although these dog bones were not prepared fully according to the above mentioned ISO standard, obtained data for the reference material (BM Ref) agreed with the supplier data sheet values (100 kJ / m2) - see results below related to Table 3B. The test pieces from the blow-moulded samples were equilibrated according to ISO179-2 at 23°C and 50% RH for 10 days prior to testing.

[0122] Test pieces for impact testing were notched using a Tinius Olsen model 899 Specimen Notcher according to ISO 179-1 / leA. The test pieces were subjected to thermal conditioning for 3h at 23° C before testing.

[0123] The tensile testing was performed on a Tinius Olsen H10ST according to ISO 527-2:2019.

[0124] The impact testing was performed on a Tinius Olsen IT503 according to ISO 179-1 / 1 eA: Test piece 1, edgewise, notched. A 25 J impact was used.

[0125] Melt flow rate testing

[0126] Melt flow rate was measured using a Melt Index Tester PCE-MFI 400. Tests were performed according to the standard ISO 1133-1. The melt flow rate was measured at various temperatures and using various weights, as indicated in the results below.

[0127] RESULTS

[0128] Hydrogen gas permeability results

[0129] Figure 3A shows the obtained hydrogen permeabilities for respectively, from left to right, the PA6 Ref and Samples SI to S6. As can be seen, at relatively low graphene concentrations, the permeability drops significantly, after which it stabilizes at about half of the permeability of the PA6 Ref at 0 wt% graphene. In other words, PA6 with added graphene beneficially shows a significant reduction in the hydrogen permeability. Figure 3B show the same data, but then in percentage relative to the PA6 Ref.

[0130] Since generally for blow moulding additives are required, which may have an effect on the hydrogen permeability, several of the specific blow moulding formulations were also tested for hydrogen permeability. The results are shown in Table 2 and in Figure 4. Table 3 Hydrogen permeability comparison of extruded and blow-moulded samples, including preextruded blow moulded and blended blow moulded samples. The composition, process and applied pressure in the parison during blow -moulding are described for each sample. By comparing extruded samples with blow moulded samples of the same base composition formulation 7, the blow moulded samples EX6H and EX10H have a reduced hydrogen permeability compared to the extruded sample F7. In addition, the blow moulded samples with the compositions according to the present application, samples EX6H and EX10H, show reduced hydrogen permeabilities compared to the reference samples based on only blow moulding grade PA6, that is, sample RF8L.

[0131] The blow-moulded samples exhibited an average decrease in the hydrogen permeability of 57% for the graphene containing samples, compared to the benchmark grade Durethan BC550Z. The change in permeability due to the blow-moulding process only, i.e. not due to the graphene, was 22%. The decrease in hydrogen permeability due to graphene addition only was on average 36%. There was no significant change in permeability due to applied increased pressure in the parison during blow moulding.

[0132] Although the extruded samples based on neat PA6 (Samples S1-S6) show lower hydrogen permeabilities compared to the present blow moulded samples, the neat PA6 based compositions are not suitable for blow moulding and / or the produced blow moulded products will have poor properties, such as mechanical properties.

[0133] Mechanical property results

[0134] The obtained mechanical properties can be found in Table 3A below. The Charpy notched impact strength results are shown for samples S1-S4 in Figure 5. Compared to the PA6 reference without graphene, in particular the sample SI exhibits a similar impact strength as the PA6 reference (PA6 Ref). It is noted that actual blow moulded products may exhibit a different, perhaps higher, impact strength. The samples in Table 3A are all prepared by the same technique; compression moulding of extruded pellets, allowing for internal comparison.

[0135] Table 3 A: Results for notched impact strength, tensile modulus, and ultimate strength for compositions mentioned above. Although the values are mainly given in absolute terms according to the unit given at the top row and respective column, when a value indicates a percentage, the percentage is the change in the parameter associated with the respective column compared to the PA6 ref Referring now to Figure 6. the tensile modulus increases by almost a factor 2. A plateau is visible between 0.8 and 3% graphene. For sample SI the tensile modulus is increased by 45%. The ultimate strength, see Figure 7, shows a different trend than the tensile modulus. The ultimate strength of sample SI is increased compared to the PA6 Ref sample by 30%. This shows that a graphene content of or around 0.39 %, for example 0.3% - 0.5%, provides compositions with improved mechanical properties, wanted for polymer products.

[0136] Also in the higher graphene content range, for example from 2%-4%, the ultimate strength shows increased values over the PA6 Refat 0% graphene. Samples S3 and S4 have 27% and 17% higher ultimate strengths, respectively. The respective impact strengths (Figure 5) of these samples are reduced, but higher than outside of this graphene range. This graphene range of 2%-4% may be especially suitable for hydrogen barrier applications, since they exhibit a combination of low hydrogen permeability and good mechanical properties.

[0137] The formulations 5-8, which comprise the BM grade PA6, exhibit higher impact strength. The impact strength data for these samples is indicated in Figure 8 as a function of additional impact modifier content in % by weight per total weight of the formulation. Formulation 5 comprised no additional impact modifier, formulation 6 comprised 1% additional impact modifier, formulation 7 comprised 2% additional impact modifier, and formulation 8 comprised 3% additional impact modifier. The average impact strength increases with increasing impact modifier content. The graphene content of formulations 5-7 was the same. Formulation 8 had somewhat less graphene. All of formulations 5-8 comprised similar amounts of BM grade PA6 (ranging from 58 wt% to 60 wt%), meaning that the total amount of impact modifier was similar.

[0138] Charpy notched impact strength was further measured for blow moulded samples. The obtained results are given in Table 3B below. The samples are the same as indicated in Table 2. Sample RF9L is made in the same way as sample RF8L. Beneficially, the blow-moulded samples of the same composition (formulation 7) have a higher impact strength than the compression moulded samples of which the data is shown in Table 3 A. The reference for the BM Ref samples (RF9L and RF8L) was found to be 102 kJ / m2, close to the supplier data sheet value of 100 kJ / m2, indicating that the samples are made according to standards. Table 3B: Results for Charpy notched impact strength for blow moulded liner samples mentioned above.

[0139] Low temperature impact strength measurements

[0140] The conditions to which hydrogen pressure vessels and pipes are exposed can be extreme. For example, the loading and unloading of hydrogen into a pressure vessel exposes the vessel to temperatures ranging down to -40 °C or even lower. Therefore, there are requirements on mechanical stability at low and high temperature of hydrogen pressure vessels and pipes. To certify safety for mobile storage of hydrogen specifically, hydrogen pressure vessels are tested, for example according to regulation UN / ECE-R134. This regulation requires performance durability and expected on-road performance of hydrogen pressure vessels, including cycling between -40 °C and + 50 °C followed by burst testing, that is, a test where the vessel experiences an impact.

[0141] Therefore, impact strengths of some examples of the liner materials according to the present patent disclosure were tested at -40 °C and compared to the BM Ref sample. Results are shown in the table below. Formulation 7 comprised 2% additional impact modifier, while formulation 10 comprised 8% additional impact modifier. The relative impact strengths are similar. It can be concluded that the additional impact modifier has little effect on the impact strength at low temperature. Because of this, compared to the much larger drop in impact strength of the reference, even at a higher temperature, it can be concluded that the effect of the presence of graphene (rGO) in the formulations has the effect of lowering the effect of extreme cold on the mechanical properties, specifically impact strength, of the compositions according to the present patent disclosure. Table 4: Drop in impact strength relative to the impact strength at room temperature for two samples according to the present disclosure and a reference blow moulding grade material BM Ref .

[0142] Melt Flow Rate (MFR) results

[0143] Obtained results are indicated in Table 5 below. The addition of graphene results in a lowered MFR. Formulation 1-7, which comprise respective amounts of BM grade PA6, show suitable MFR values for use with blow moulding. Formulations 4-7 will satisfy an upper limit MFR, even more suitable for blow-moulding, of 15 g / 10 min, measured at 250 °C and with a weight of 16.6 kg. Although the MFR for formulation 4 was only measured using a lower weight of 11.6 kg, its MFR under the same conditions is similar to that of formulation 5. In turn, formulation 5 has an MFR of 10.5 kg / 10 min at 16.6, meaning that formulation 4 will also have a similar MFR at this applied weight, thus satisfying the mentioned upper limit.

[0144] The impact modifier, BM grade PA6 and graphene all contribute to a lower MFR, such that all of these parameters can be used to tune the MFR, depending on the desired amount of graphene. For example, for obtaining the same MFR, for hydrogen barrier applications, the amount of graphene may be higher while the amount of BM grade PA6 or additional impact modifier may be lower.

[0145] Table 5: Melt flow rates for compositions at various applied weights (2.16, 11.6, 16.6, and 21.6 kg) and at two temperatures.

[0146] Further examples 1. Blow moulded product made of a polyamide-6-based composite material comprising a polyamide 6- based matrix and graphene in an amount of 0.1-8 wt% of the polyamide-6-based composite material.

[0147] 2. Blow moulded product according to example 1, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.1-7.5 wt% of the polyamid-6-based composite material.

[0148] 3. Blow moulded product according to example 1 or 2, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.1-6 wt% of the polyamid-6-based composite material.

[0149] 4. Blow moulded product according to any one of examples 1 to 3, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.2-3 wt% of the polyamid-6-based composite material. 5. Blow moulded product according to any one of examples 1 to 4, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.3-0.8 wt%, such as 0.3 - 0.5 wt%, of the polyamid-6-based composite material.

[0150] 6. Blow moulded product according to any one of examples 1 to 5, wherein the graphene (201) is distributed in the polyamide-6-based matrix (202); and / or the graphene (201) is uniformly distributed in the polyamide-6-based matrix (202).

[0151] 7. Blow moulded product according to any one of examples 1 to 6, wherein a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based composite material is reduced by at least 20%, preferably at least 30%, more preferably at least 40% compared to a blow moulded blow moulding grade polyamide-6 material.

[0152] 8. Blow moulded product according to any one of examples 1 to 7, having a tensile modulus as measured according to ISO 527-2 at 23 °C that is increased by at least 20%, preferably 50%, compared to neat polyamide-6.

[0153] 9. Blow moulded product according to any one of examples 1 to 8, having a Charpy notched impact strength in the range of 5-20 kJ / m2 as measured according to ISO 179-1:2020 performed at a temperature of 23 °C with a 25 J impact.

[0154] 10. Blow moulded product according to any one of examples 1 to 9, wherein the product is a hydrogen barrier lining for lining of a hydrogen storage means or hydrogen transport means.

[0155] 11. Polyamide-6-based composite material (200) for blow-moulding, the polyamide-6-based composite material (200) comprising a polyamide-6-based matrix (202) and graphene (201) in an amount of 0.1%- 8% in weight per weight of the polyamide-6-based composite material (200), and having a melt flow rate of at most 15 g / 10 min as measured according to ISO 1133-1 at a temperature of 250 °C with a weight of 16.6 kg.

[0156] 12. Polyamide-6-based composite material (200) according to example 11, wherein the melt flow rate lies in a range of 5 to 13 g / 10 min, preferably 6-12 g / 10 min, as measured according to ISO 1133-1 at a temperature of 250 °C with a weight of 16.6 kg.

[0157] 13. Polyamide-6-based composite material (200) according to example 11 or 12, comprising graphene (201) in an amount of 0. l%-7.5% in weight per weight of the polyamide 6-based composite material (200). 14. Polyamide-6-based composite material (200) according to example 11, 12 or 13, wherein the amount of graphene (201) in the polyamide-6-based composite material (200) is 0. l%-6% in weight per weight of the polyamide-6-based composite material (200).

[0158] 15. Polyamide-6-based composite material (200) according to example 11 or 12, wherein the amount of graphene (201) in the polyamide-6-based composite material (200) is 2%-8%, preferably 3%-7.5% in weight per weight of the polyamide-6-based composite material (200).

[0159] 16. Polyamide-6-based composite material (200) according to any one of examples 11 to 15, wherein a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6- based composite material is reduced by at least 5%, preferably at least 10%, more preferably at least 30% compared to neat polyamide 6.

[0160] 17. Polyamide-6-based composite material (200) according to example 15, wherein the hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based composite material is reduced by at least 30% compared to neat polyamide 6.

[0161] 18. Polyamide-6-based composite material (200) according to example 17, having a tensile modulus as measured according to ISO 527-2 at 23 °C that is increased by at least 20%, preferably 50%, compared to neat polyamide-6.

[0162] 19. Assembly (100) for hydrogen storage and / or transport, the assembly comprising:

[0163] - a hollow solid body (101); and

[0164] - at least one hydrogen barrier lining (102) according to example 10.

[0165] 20. Assembly (100) according to example 19, wherein the surface of the hollow solid body (101) is an inner surface (101a) of the hollow solid body (101); the hollow solid body (101) is atank, a vessel, a pipe, a joint, or a cylinder.

[0166] 21. Assembly (100) according to example 19 or 20, wherein the assembly is a hydrogen storage container or a hydrogen transport container, wherein optionally the hydrogen storage container is a hydrogen storage tank, a hydrogen storage vessel, or a hydrogen cylinder; and / or the hydrogen cylinder is a hydrogen gas cylinder; and / or the hydrogen transport container is a hydrogen transport pipe or a joint for joining hydrogen transport pipes; and / or the hollow solid body (101) is a hollow stainless-steel body, a hollow carbon or glass fibre winded body, or a hollow polymer body.

[0167] 22. Assembly (100) according to example 19, 20 or 21, wherein the hydrogen barrier lining (102) is attached to the hollow solid body (101) using an adhesive.

[0168] 23. Assembly (100) according to any one of examples 19-22, wherein the hydrogen barrier lining (102) is attached to the hollow solid body in a binder-free manner.

[0169] 24. Method for manufacturing an assembly for hydrogen storage and / or transport (100) according to any one of examples 20 to 23, comprising lining a surface (101a) of the hollow solid body (101) with one of the at least one hydrogen barrier linings (102).

[0170] 25. Use of a polyamide-6-based composite material (200) according to any one of examples 11 to 18 as a hydrogen barrier lining (102).

[0171] 26. Method of producing a polyamide-6-graphene composite material (200) for blow moulding, comprising: providing a first mixture of neat polyamide-6 or blow moulding grade polyamide-6 material, and graphene in an amount of 4-8 wt% of the first mixture; and diluting the first mixture with a blow moulding grade polyamide-6 material when the first mixture comprises the neat polyamide-6 and with neat polyamide-6 when the first mixture comprises the blow moulding grade polyamide-6 material, and optionally an impact modifier, such that the polyamide-6- graphene composite material (200) with a reduced amount of graphene compared to the first mixture is obtained.

[0172] 27. Method according to example 26, wherein the diluting comprises diluting 5-50 wt% of the first mixture with 95-50 wt% of blow moulding grade polyamide-6 material.

[0173] 28. Method according to example 26 or 27, further comprising adding 0.5 - 20 wt%, preferably 0.5 - 10 wt%, of an impact modifier in weight per weight of the polyamide-6-graphene composite material (200). 29. Method according to example 26 or 27, wherein the blow moulding grade polyamide-6 material comprises 15 to 30 wt% of an impact modifier in weight per weight of the blow moulding grade polyamide-6 material. 30. Use of a polyamide-6-graphene composite material (200) according to any one of examples 15 and

[0174] 16 to 18 in dependence of example 15, as a masterbatch composition.

[0175] Although the present patent disclosure refers to specific examples, which may also be shown in the appended drawings, it will be apparent to those skilled in the art that many variations and modifications can be done within the scope of the present patent disclosure as described in the specification and defined with reference to the claims below.

Claims

CLAIMS1. Assembly (100) for hydrogen storage and / or transport, the assembly comprising:- a hollow solid body (101); and- at least one hydrogen barrier lining (102), wherein the at least one hydrogen barrier lining (102) is a blow moulded hydrogen barrier lining (102) made of a polyamide-6-based composite material comprising a polyamide-6-based matrix and graphene in an amount of 0.1-10 wt% of the polyamide-6-based composite material.

2. Assembly (100) according to claim 1, wherein a surface of the hollow solid body (101) is lined with one of the at least one hydrogen barrier linings ( 102), wherein optionally the surface of the hollow solid body ( 101 ) is an inner surface (101a) of the hollow solid body (101); and / or the hollow solid body (101) is a tank, a vessel, a pipe, a joint, or a cylinder; and / or the polyamide-6-based composite material (200) has a melt flow rate of at most 15 g / 10 min as measured according to ISO 1133-1 at a temperature of 250 °C with a weight of 16.6 kg. wherein the polyamide-6-based composite material comprises graphene in an amount of 0. 1-7.5 wt% of the polyamid-6-based composite material.

3. Assembly (100) according to claim 1 or 2, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.1-6 wt% of the polyamid-6-based composite material.

4. Assembly (100) according to any one of claims 1 to 3, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.2-3 wt% of the polyamid-6-based composite material.

5. Assembly (100) according to any one of claims 1 to 4, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.3-0.8 wt%, such as 0.3 - 0.5 wt%, of the polyamid- 6-based composite material.

6. Assembly (100) according to any one of claims 1 to 5, wherein the graphene (201) is distributed in the polyamide-6-based matrix (202); and / or the graphene (201) is uniformly distributed in the polyamide-6-based matrix (202).

7. Assembly (100) according to any one of claims 1 to 6, wherein a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based compositematerial is reduced by at least 20%, preferably at least 30%, more preferably at least 40% compared to a blow moulded blow moulding grade polyamide-6 material.

8. Assembly (100) according to any one of claims 1 to 7, having a tensile modulus as measured according to ISO 527-2 at 23 °C that is increased by at least 20%, preferably 50%, compared to neat polyamide-6.

9. Assembly (100) according to any one of claims 1 to 8, having a Charpy notched impact strength in the range of 5-20 kJ / m2as measured according to ISO 179-1 : 2020 performed at a temperature of 23 °C with a 25 J impact.

10. Assembly (100) according to any one of claims 1 to 9, wherein the assembly is a hydrogen storage container or a hydrogen transport container, wherein optionally the hydrogen storage container is a hydrogen storage tank, a hydrogen storage vessel, or a hydrogen cylinder; and / or the hydrogen cylinder is a hydrogen gas cylinder; and / or the hydrogen transport container is a hydrogen transport pipe or a joint for joining hydrogen transport pipes; and / or the hollow solid body (101) is a hollow stainless-steel body, a hollow carbon or glass fibre winded body, or a hollow polymer body.

11. Assembly (100) according to any one of claims 1 to 10, wherein the hydrogen barrier lining (102) is attached to the hollow solid body (101) using an adhesive.

12. Assembly (100) according to any one of claims 1 to 10, wherein the hydrogen barrier lining (102) is attached to the hollow solid body in a binder-free manner.

13. Method for manufacturing an assembly for hydrogen storage and / or transport (100) according to any one of claims 1 to 12, comprising lining a surface (101a) of the hollow solid body (101) with one of the at least one hydrogen barrier linings (102).

14. Use of a polyamide-6-based composite material (200) as a hydrogen barrier lining (102), wherein the polyamide-6-based composite material (200) comprises a polyamide-6-based matrix (202) and graphene (201) in an amount of 0. 1 %- 10%, or 0. l%-8%, in weight per weight of the polyamide-6- based composite material (200).

15. Use according to claim 25, wherein the polyamide-6-based composite material (200) for blow-moulding; and / or the polyamide-6-based composite material (200) is a polyamide-6-based composite material (200) for blow-moulding, the polyamide-6-based composite material (200) comprising a polyamide-6-based matrix (202) and graphene (201) in an amount of 0. l%-10%, or 0. l%-8%, in weight per weight of the polyamide-6-based composite material (200), and having a melt flow rate of at most 15 g / 10 min as measured according to ISO 1133-1 at a temperature of 250 °C with a weight of 16.6 kg..

16. Method of producing a polyamide-6-based composite material (200) for blow moulding, wherein the polyamide-6-based composite material (200) comprises a polyamide-6-based matrix (202) and graphene (201) in an amount of 0. 1 %- 10%, or 0. l%-8%, in weight per weight of the polyamide-6- based composite material (200), wherein the method comprises: providing a first mixture of neat polyamide-6 or blow moulding grade polyamide-6 material, and graphene in an amount of 4-8 wt% of the first mixture; and diluting the first mixture with a blow moulding grade polyamide-6 material when the first mixture comprises the neat polyamide-6 and with neat polyamide-6 when the first mixture comprises the blow moulding grade polyamide-6 material, and optionally an impact modifier, such that the polyamide-6-graphene composite material (200) with a reduced amount of graphene compared to the first mixture is obtained.

17. Method according to claim 16, wherein the diluting comprises diluting 5-50 wt% of the first mixture with 95-50 wt% of blow moulding grade polyamide-6 material.

18. Method according to claim 16 or 17, further comprising adding 0.5 - 20 wt%, preferably 0.5 - 10 wt%, of an impact modifier in weight per weight of the polyamide-6-graphene composite material (200).

19. Method according to claim 16 or 17, wherein the blow moulding grade polyamide-6 material comprises 15 to 30 wt% of an impact modifier in weight per weight of the blow moulding grade polyamide-6 material.

20. Method according to claim 13, or use according to claim 14 or 15, wherein the polyamide-6- based composite material is produced according to a method of any one of claims 16 to 19.

21. Blow moulded product made of a polyamide-6-based composite material comprising a polyamide-6-based matrix and reduced Graphene Oxide, rGO in an amount of 0.1-10 wt% of the polyamide-6-based composite material.

22. Blow moulded product according to claim 21, wherein the polyamide-6-based composite material comprises graphene in an amount of 0. 1-7.5 wt% of the polyamid-6-based composite material.

23. Blow moulded product according to claim 21 or 22, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.1-6 wt% of the polyamid-6-based composite material.

24. Blow moulded product according to any one of claims 21 to 23, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.2-3 wt% of the polyamid-6-based composite material.

25. Blow moulded product according to any one of claims 21 to 24, wherein the polyamide-6-based composite material comprises graphene in an amount of 0.3-0.8 wt%, such as 0.3 - 0.5 wt%, of the polyamid-6-based composite material.

26. Blow moulded product according to any one of claims 21 to 25, wherein the graphene (201) is distributed in the polyamide-6-based matrix (202); and / or the graphene (201) is uniformly distributed in the polyamide-6-based matrix (202).

27. Blow moulded product according to any one of claims 21 to 26, wherein a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based composite material is reduced by at least 20%, preferably at least 30%, more preferably at least 40% compared to a blow moulded blow moulding grade polyamide-6 material.

28. Blow moulded product according to any one of claims 21 to 27, having a tensile modulus as measured according to ISO 527-2 at 23 °C that is increased by at least 20%, preferably 50%, compared to neat polyamide-6.

29. Blow moulded product according to any one of claims 21 to 28, having a Charpy notched impact strength in the range of 5-20 kJ / m2as measured according to ISO 179-1:2020 performed at a temperature of 23 °C with a 25 J impact.

30. Blow moulded product according to any one of claims 21 to 29, wherein the product is a hydrogen barrier lining for lining of a hydrogen storage means or hydrogen transport means.

31. Polyamide-6-based composite material (200) for blow-moulding, the polyamide-6-based composite material (200) comprising a polyamide-6-based matrix (202) and reduced Graphene Oxide, rGO (201), in an amount of 0. l%-10%, or 0. l%-8%, in weight per weight of the polyamide- 6-based composite material (200), and having a melt flow rate of at most 15 g / 10 min as measured according to ISO 1133-1 at a temperature of 250 °C with a weight of 16.6 kg.

32. Polyamide-6-based composite material (200) according to claim 31, wherein the polyamide-6- based matrix (202) comprises neat polyamide-6 and a blow moulding grade polyamide-6 polymer material.

33. Polyamide-6-based composite material (200) according to claim 31 or 32, comprising graphene (201) in an amount of 0.1%-7.5% in weight per weight of the polyamide-6-based composite material (200).

34. Polyamide-6-based composite material (200) according to claim 31, 32 or 33, wherein the amount of graphene (201) in the polyamide-6-based composite material (200) is 0.1 %-6% in weight per weight of the polyamide-6-based composite material (200).

35. Polyamide-6-based composite material (200) according to claim 31 or 32, wherein the amount of graphene (201) in the polyamide-6-based composite material (200) is 2%-10%, preferably 2%- 8%, more preferred 3%-7.5%, in weight per weight of the polyamide-6-based composite material (200).

36. Polyamide-6-based composite material (200) according to any one of claims 31 to 35, wherein a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based composite material is reduced by at least 5%, preferably at least 10%, more preferably at least 30% compared to neat polyamide-6.

37. Polyamide-6-based composite material (200) according to claim 35, wherein the hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-6-based composite material is reduced by at least 30% compared to neat polyamide-6.

38. Polyamide-6-based composite material (200) according to claim 37, having a tensile modulus as measured according to ISO 527-2 at 23 °C that is increased by at least 20%, preferably 50%, compared to neat polyamide-6.

39. Use of a polyamide-6-graphene composite material (200) according to any one of claims 35 and36 to 38 in dependence of claim 15, as a masterbatch composition for manufacturing a hydrogen barrier lining for use in an assembly for hydrogen storage and / or transport, wherein optionally the assembly for hydrogen storage and / or transport is the assembly according to any one of claims 1 to 12.