Polyamide-11-graphene composite material and assembly for hydrogen storage and / or transport

Abstract

The present patent disclosure concerns an assembly for hydrogen storage and / or transport, the assembly comprising a hollow solid body and at least one hydrogen barrier lining arranged along a surface of the hollow body, wherein the at least one hydrogen barrier lining comprises a polyamide-11-based composite material comprising a polyamide-11-based matrix and reduced graphene oxide in an amount of 0.1-15% in weight per weight of the polyamide-11-based composite material (200).

Description

[0001] POLYAMIDE- 11 -GRAPHENE COMPOSITE MATERIAL AND ASSEMBLY FOR HYDROGEN STORAGE AND / OR TRANSPORT

[0002] The present patent disclosure is within in the field of hydrogen transport and storage and polyamide- 11- based materials for such transport and storage. Particular embodiments concern a polyamide- 11 -based composite material, an assembly for hydrogen storage and / or transport, a method for manufacturing such assemblies and use of the polyamide- 11 -based composite material.

[0003] 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.

[0004] 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 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.

[0005] 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.

[0006] 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 the first choice as 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.

[0007] 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 concerns specific examples based upon polyamide-6 and is unrelated to the field of hydrogen storage and / or transport.

[0009] KR20220117826A relates to a hydrogen storage container for storing hydrogen in a storage space surrounded by a wall. The wall may comprise a liner made of a polyethylene based resin or polyamide based resin, such as PA6, PA11 and PA12. PA6 is preferred. The resin may comprise nanoparticles such as silicate, carbon nanotube, graphene, and nanoclay. The nanoparticles may be included in 2 to 10 wt%, preferably 4 to 8 wt%. An estimated hydrogen permeability for an unspecified composite material based on the found, or also estimated, mechanical properties is provided.

[0010] It is an object, among objects, to provide improved assemblies for hydrogen storage and / or transport. It is also an object, among objects, to provide improved materials that can be used in assemblies for hydrogen storage and / or transport.

[0011] To this end, in accordance with a first aspect, there is provided an assembly for hydrogen storage and / or transport in accordance with appended claim 1. The assembly comprises a hollow solid body and at least one hydrogen barrier lining arranged along a surface of the hollow body, wherein the at least one hydrogen barrier lining comprises a polyamide- 11 -based composite material comprising a polyamide- 11-based matrix and graphene in an amount of 0. 1-7.5% in weight per weight of the polyamide-11- based composite material.

[0012] The provided polyamide-11 -based composite material comprising graphene shows a reduced hydrogen permeability compared to bare / neat polyamide-11. The obtained experimental results for composite materials falling within this scope described below show decreasing hydrogen permeability the more graphene is in the composite material, even as low as 50% lower hydrogen permeation as neat polyamide-11. Compared to polyamide-6, which inherently has a lower hydrogen permeability than polyamide- 11, the present composite materials at least partially reduce this difference in permeability between polyamide-6 and polyamide-11, thus allowing polyamide-11 to be used in similar applications. Beneficially, polyamide- 11 is easier to handle, is less sensitive to moisture, is less prone to fatigue, has a higher impact resistance at low temperatures than polyamide-6 and polyamide- 12 and has improved resistance to blistering and crack formation, which is wanted in high pressure vessels which are pressurized and depressurized repeatably. Moreover, polyamide 11 is especially tough at low temperatures and has been observed to be twice as resilient as polyamide 12 at -30°C during a notched Charpy impact test.

[0013] In addition, beneficially, the composite materials according to the present patent disclosure have improved mechanical properties compared to reference polyamide-11. For example, respective elongations at break as measured for the composite materials are increased by at least 100% compared to the bare polyamide- 11 , even by as much as 161 %, and the obtained respective Charpy notched impact strengths measured for the composite materials at 23 °C are increased by at least 8%, compared to bare polyamide-11.

[0014] At the same time, at the above noted graphene concentration range of 0.1 wt% to 7.5 wt% relative to the polyamide- 11 -based matrix, the composite material can be processed using standard polymer processing techniques, such as injection moulding, rotational moulding, compression moulding, blow moulding and / or extrusion. Beneficially, the provided polyamide- 11 -based composite materials comprising graphene have a decreased melt flow rate as compared to the reference polyamide- 11 -based polymer without graphene. Thus, the composite materials of the present patent disclosure have improved processability of the bare polymer in several processes, e.g., a blow moulding process, where a reduced melt flow rate is required.

[0015] The provided polyamide-11 based composite materials comprises reduced graphene oxide which is preferably well dispersed. For the provided polyamide- 11 based composite materials, evidence suggests that the reduced graphene oxide is well adhered to the polyamide- 11 polymer matrix.

[0016] The hollow body being provided with the hydrogen barrier lining made from the polyamide -11 -based composite material reduces the hydrogen leakage towards the surface of the hollow body at which the lining is provided. Thereby also, the driving force for hydrogen to permeate into or through the hollow body is reduced. For instance, if the hollow body is made of a polymer material, such as high-density polyethylene or polyamide, the hydrogen permeation through the hollow body is reduced. If the hollow body is made of a hydrogen impermeable material, such as steel, then the rate of hydrogen embrittlement is reduced. The assembly may be a hydrogen carrying assembly. The assembly may additionally or alternatively be referred to as a hydrogen transport and / or storage assembly.

[0017] The lining can additionally provide a pathway for conducting electricity and thus reduces the chance of discharges towards a hydrogen rich environment when the assembly is in use.

[0018] In an embodiment, the graphene is reduced graphene oxide. The reduced graphene oxide contains a certain amount of hydroxide and carboxyl groups which may interact with the polar amide groups of PA 11. Other types of graphene, such as Graphene Nano Platelets (GNPs), are less polar and tend to interact less with polar polymers such as polyamides. Thus, reduced graphene oxide is better suited to intermix with polyamides, leading to an improved polymer-graphene interaction. Without being bound by theory, it is thought that both permeation and mechanical properties are highly dependent on this interaction between the polymer and reduced graphene oxide, since, for example, any void in the composition leads to increased diffusion, decreased mechanical strength and increased risk of blistering.

[0019] Further embodiments are provided in the appended dependent claims 2 to 11.

[0020] In accordance with a second aspect, there is provided a polyamide- 11 -based composite material comprising a polyamide- 11 -based composite and graphene in an amount of 0.1%-8% in weight per weight of the polyamide -11 -based composite.

[0021] In an embodiment, the graphene is distributed in the polyamide- 11 -based matrix.

[0022] In an embodiment, the graphene is uniformly distributed in the polyamide- 11 -based matrix.

[0023] In an embodiment, the polyamide- 11 -based composite material comprises graphene in an amount of 2% to 8 %, preferably 3% to 7.5%, in weight per weight of the polyamide- 11 -based composite. This composite shows lowered hydrogen permeability and is also suitable for use as a masterbatch composition.

[0024] In an embodiment, the polyamide- 11 -based composite material comprises graphene in an amount of 0.2%-0.7%, such as 0.2%-0.5%, in weight per weight of the polyamide-11-based composite. This range results in a composite material having an even more advantageous combination of lowered hydrogen permeability and processability of the composite material using the standard polymer processing techniques. In an embodiment, the amount of graphene in the polyamide- 11 -based composite material is 0.1% to 0.7%, preferably 0.2 to 0.5%, most preferred 0.2%-0.4% in weight per weight of the polyamide-11- based composite. Surprisingly, when the graphene content is around 0.3 wt%, approximately between 0.1 and 0.7 wt%, such as 0.2 to 0.5 wt%, the hydrogen permeability is found to be already about 30% lower than neat polyamide-11. Also, the hydrogen permeability of this embodiment is found to be lower than that of a composite with 2.2 wt% graphene, as is described in further detail below. Also, at these graphene concentrations, the mechanical properties show improvements. These improvements include an increased impact strength compared to neat polyamide- 11. Higher concentrations of graphene, e.g. 2.2 wt% and higher, show a decreased impact strength compared to neat polyamide-11. The improvements further include an increased elongation at break, over 150% relative to neat polyamide- 11 while the ultimate strength is lowered by only about 25% relative to neat polyamide-11. In addition, these lower weight percentages of graphene, i.e. between 0.1 and 0.7 wt%, provide not only the surprising lowering in hydrogen permeability, but also are still processable with techniques such as blow moulding. This is further explained below, such as in relation to Table 3. This allows these composite materials based on polyamide-11 to be used in applications where earlier polyamide-6, due to its inherently lower hydrogen permeation, would have been selected. Using polyamide-11 with graphene is advantageous because polyamide-11 has better mechanical properties as outlined above. These properties can be further improved by adding graphene in the amount specified above. In comparison, blow moulding grade polyamide-6 shows a hydrogen permeability of about 0.9- 10'9mol m1s1MPa1while the present polyamide-11 based composite with only 0.3 wt% rGO shows a similar hydrogen permeability of about 1.15- 10'9mol m1s1MPa1under the same experimental conditions.

[0025] In an embodiment, a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-11-based composite material is reduced by at least 15%, preferably at least 20%, more preferably at least 30% compared to neat polyamide-11.

[0026] In an embodiment, when the polyamide-11 -based composite material comprises graphene in an amount of 0.1%-0.5%, preferably 0.2%-0.4%, in weight per weight of the polyamide-11-based composite, the hydrogen permeability as measured according to ASTM D1434-82, procedure M, ofthe polyamide-11- based composite material is reduced by at least 30% compared to neat polyamide- 11.

[0027] In an embodiment, the polyamide-11 -based composite material has an elongation at break as measured according to ISO 527-2 at 23 °C that is increased by at least 100%, preferably 130%, compared to neat polyamide-11. In an embodiment, the polyamide- 11 -based composite material has a Charpy notched impact strength as measured according to ISO 179:2010 at 23 °C that is increased by at least 8%, preferably 10%, compared to neat polyamide- 11.

[0028] In an embodiment, the polyamide- 11 -based composite material has an ultimate strength as measured according to ISO 527-2 at 23 °C that is decreased by at least 15% compared to neat polyamide-11.

[0029] In one embodiment, the reduced graphene oxide is adhered or bonded to the polyamide-11 -based polymer matrix.

[0030] In accordance with another aspect, there is provided a method for manufacturing any embodiment of the assembly for hydrogen storage and / or transport described above and / or below, the method comprising lining a surface of the hollow solid body with one of the at least one hydrogen barrier linings.

[0031] In an embodiment, the surface of the hollow solid body lined with the hydrogen barrier lining is an inner surface of the hollow solid body.

[0032] In an embodiment, the assembly for hydrogen storage and / or transport is the assembly for hydrogen storage and / or transport according to any embodiment of the second aspect and / or any embodiment described below.

[0033] In accordance with a yet another aspect, use is provided of a polyamide-11 -graphene composite material according to any embodiment described above and below as a hydrogen barrier lining.

[0034] According to another aspect, there is provided a method of producing a polyamide-11 -graphene composite material, comprising diluting a polyamide-11 -graphene composite material comprising a polyamide-11-based matrix and reduced graphene oxide in an amount of 2%-8%, preferably 3%-7.5% in weight per weight of the polyamide-11 -based composite material with neat polyamide-11 polymer. With this method, it is possible to tune the properties of the composite. For example, the addition of the reduced graphene oxide to the polyamide-11 causes a reduction of the melt flow rate. By adding neat polyamide-11, the melt flow rate can be increased again. In this way, the composite can be tuned to obtain a desired mass flow rate, among other properties. In addition, specific polyamide-11 grades are available for different purposes, such as extrusion or blow moulding, which already have a reduced melt flow rate, even without reduced graphene oxide present. Also, these grades may comprise additives which sometimes increase the hydrogen permeability. Beneficially, it is found that adding neat polyamide- 11 to compensate for the lower melt flow rate caused by addition of reduced graphene oxide lowers the hydrogen permeability further. In an embodiment, the polyamide- 11 of the polyamide- 11 -based matrix of the polyamide- 11 -graphene composite material is a polyamide- 11 suitable for blow moulding.

[0035] According to a further aspect, there is provided use of a polyamide- 11 -graphene composite material comprising reduced graphene oxide in an amount of 2%-8%, preferably 3%-7.5% in weight per weight of the polyamide- 11 -based composite material as a masterbatch composition.

[0036] 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.

[0037] Brief Description of the Drawings

[0038] 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:

[0039] Figure la is a schematic drawing of an embodiment of the assembly according to the present patent disclosure;

[0040] Figure lb is a schematic drawing of another embodiment of the assembly according to the present patent disclosure;

[0041] Figure 1c is a schematic drawing of an embodiment of the assembly according to the present patent disclosure;

[0042] Figure Id is a schematic drawing of an embodiment of the assembly according to the present patent disclosure;

[0043] Figure 2 is a schematic drawing of one embodiment of the polyamide- 11 -based material of the present patent disclosure;

[0044] Figure 3A is a graph of IT permeability [mohn ’ s ’-MPa1] as a function of graphene concentration [wt%] in polyamide- 11 -based composite materials of the present patent disclosure;

[0045] Figure 3B is a graph of change in H2 permeability [%] as a function of graphene concentration [wt%] relative to neat polyamide- 11 of the polyamide- 11 -based composite materials of the present patent disclosure; Figure 4A is a graph of tensile modulus [MPa] as a function of graphene concentration [wt%] of the polyamide- 11 -based composite materials of the present patent disclosure;

[0046] Figure 4B is a graph of change in tensile modulus [%] as a function of graphene concentration [wt%] relative to neat polyamide- 11 (0% graphene) of the polyamide- 11 -based composite materials of the present patent disclosure shown in Figure 4A;

[0047] Figure 5A is a graph of ultimate strength [MPa] (left axis) and elongation at break [%] (right axis), both as a function of graphene concentration [wt%], of polyamide- 11 -based composite materials of the present patent disclosure;

[0048] Figure 5B is a graph of change in ultimate strength [MPa] (left axis) and change elongation at break [%] (right axis), both as a function of graphene concentration [wt%], relative to neat polyamide-11 (0% graphene) of polyamide-11 -based composite materials of the present patent disclosure shown in Figure 5A;

[0049] Figure 6A is a graph of impact strength [kJ / m2] as a function of graphene concentration [wt%] of polyamide-11 -based composite materials of the present patent disclosure;

[0050] Figure 6B is a graph of change in impact strength [%] as a function of graphene concentration [wt%] relative to neat polyamide-11 (0% graphene) of polyamide-11 -based composite materials of the present patent disclosure shown in Figure 6A;

[0051] Figure 7A is a scanning electron microscope image of neat polyamide- 11 at a magnification factor of 10000;

[0052] Figure 7B is a scanning electron microscope image of the sample of Figure 7A at a magnification factor of 80000;

[0053] Figure 8A is a scanning electron microscope image of a polyamide-11 -based composite material according to the present patent disclosure at a magnification factor of 1500;

[0054] Figure 8B is a scanning electron microscope image of a polyamide-11 -based composite material according to the present patent disclosure at a magnification factor of 7140;

[0055] Figure 8C is a scanning electron microscope image of a polyamide-11 -based composite material according to the present patent disclosure at a magnification factor of 50000; and

[0056] Figure 8D is a scanning electron microscope image of a polyamide-11 -based composite material according to the present patent disclosure at a magnification factor of 69160.

[0057] Abbreviations

[0058] GO - graphene oxide;

[0059] PA 11 - polyamide- 11 ; rGO - reduced graphene oxide;

[0060] Detailed description 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.

[0061] 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 the present patent disclosure, reduced graphene oxide (rGO) is used in the composite materials. The rGO may comprise carbon in a range of 70 at% to 99 at%, preferably 90-98 at%.

[0062] 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- 11 -based composite material 200, comprising a polyamide- 11 -based matrix 202 and reduced graphene oxide 201 in an amount of 0.1 %-7.5% in weight per weight of the polyamide-11 composite. In the polyamide-11-based composite material 200, the reduced graphene oxide 201 may be distributed or dispersed in the polyamide-11 matrix 202.

[0063] A ‘lining’ 102 refers to a thin layer or coating provided on the surface of the hollow body 101. The lining 102 may have athickness in the pm-cm range, for instance 0,1 pm - 1 cm. The hollow body 101 may have athickness 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.

[0064] In some embodiments the adhesive layer may additionally comprise rGO, in such embodiments the rGO may provide advantageous properties to the adhesive such as for example increased mechanical strength.

[0065] 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. 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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-11-based composite material as a hydrogen barrier lining 102.

[0070] 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. The hydrogen barrier lining 102 in all embodiments disclosed herein comprises a polyamide- 11 -based composite material 200 that comprises reduced graphene oxide (rGO) 201 in a polyamide- 11 matrix 202. The polyamide- 11 -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.

[0071] The polymer-graphene composite material 200 is schematically illustrated in Figure 2. As can be seen in the Figure the rGO 201 is homogeneously or almost homogenously distributed throughout the polyamide-11 matrix 202. Without being bound by any theory, it is believed that the homogenous distribution of graphene 201 in the polyamide- 11 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 rGO 201 is distributed throughout the polyamide-11 matrix 202 as compared to a polyamide- 11 -based composite material wherein the rGO is more lumped together in parts of the composite material while less present in other parts of the composite material.

[0072] The polyamide-11 matrix 202 is made of polyamide-11 (PA11). Polyamide-11 is a polymer that is widely used and is also known as nylon-11. Polyamide 11 (PA11) or Nylon 11 is an 11 -carbon chain polymer which can be produced by the polymerization of 11-aminoundecanoic acid. PA11 can be derived from bio- or petroleum-based sources. It can be processed using standard manufacturing techniques such as extrusion, blow moulding, rotational moulding, and injection moulding.

[0073] 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.

[0074] 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.

[0075] 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. The hydrogen gas barrier layer or lining 102 comprises the polyamide- 11 -based composite material 200. As discussed, the polymer-graphene composite material 200 comprises rGO 201 distributed in a polyamide-11 matrix 202. The amount of rGO in a polymer-graphene composite material 200 is 0. 1%- 7.5 % in weight per weight of the composite, 0.5-9 % in weight per weight of the composite, 0.2-5.5 % in weight per weight of the composite, 0.2-2.5% in weight per weight of the composite, 0.2-0.8% in weight per weight of the composite, or 0.2-0.4% in weight per weight of the composite. The rGO may be made from any type of graphene source. The rGO may comprise 0. 1-30 wt% of oxygen.

[0076] 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.

[0077] All samples were manufactured using twin screw extrusion, unless stated otherwise. The used PA11 was Rilsan® BESNO TL made by Arkema, unless stated otherwise. The PAI 1 grade can be changed for another biobased or petroleum based PAI 1 grade. The rGO had a carbon content > 97 at%.

[0078] The composite compositions were processed in a 24-mm twin screw extruder where the graphene was fed through a side feeder to be mixed with the neat polyamide PAI 1.

[0079] The compounding process was conducted in two steps, the first step was to make a masterbatch of the composite material with a relatively high loading (e.g. 2-8 wt%) of the reduced graphene oxide in the neat PAI 1.

[0080] The second step was dedicated to extruding the dilution of the masterbatch with the neat PA 11 and obtaining the final compound with the desired concentration of the graphene.

[0081] Extruded samples of neat PA11, masterbatch and diluted masterbatch were used for evaluation of mechanical properties. To evaluate hydrogen permeation, samples of neat PA11, masterbatch and diluted masterbatch were extruded to sheets.

[0082] Samples with a first type polyamide-11 -based composite material shown in Figure 3 were manufactured using a grade of polyamide-11 suitable for extruding. Figure 3A shows the hydrogen permeability results for the composite materials. Figure 3B shows the relative change in hydrogen permeability compared to neat polyamide-11, i.e. without added graphene or rGO.

[0083] As can be seen in the Figures 3A and 3B, all polyamide- 11 -based composite materials comprising a graphene additive, i.e. rGO, exhibit a lower H2-gas permeability compared to the bare polyamide-11 polymer samples with 0 wt% additive concentration. All samples show a reduced hydrogen permeability. Generally speaking, the higher the concentration of rGO, the lower the H2gas permeability, except for the composite with a concentration of 0.3 wt% rGO. This concentration surprisingly has a relatively low hydrogen permeability, lower than composites with 0.7 wt% and 2.2 wt% rGO, respectively. The measurements were redone several times to make sure that this dip was because of the composite material and not because of an experimental error.

[0084] As mentioned above the rGO in a composite material 200 according to the present patent disclosure 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.

[0085] A hydrogen barrier lining 102 can typically 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.

[0086] 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- 11 -graphene composite material 101 can be manufactured by mixing polyamide- 11 with rGO using for example an extruder.

[0087] 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- 11 -based composite material 200. The polyamide- 11 -based composite material 200 can be manufactured by mixing polyamide- 11 with at least rGO, using for example an extruder.

[0088] Experimental

[0089] Gas permeability testing

[0090] Seven different samples were prepared, as mentioned above, and further shown in Tables 1 and 2 below.

[0091] Preparation of samples with rGO as additive A batch of polyamide-11 comprising 7.3 wt% of rGO was first prepared. Thereafter, this batch was diluted to concentrations of lower weight% through mixing with more polyamide- 11 as described above.

[0092] Table 1: Hydrogen permeability and various mechanical properties of neat polyamide-11 and composites with various reduced graphene oxide concentrations in accordance with the present disclosure.

[0093] Table 2: Relative change compared to neat polvamide-11 (0 wt% graphene) of the various parameters shown in Table 1.

[0094] Gas permeability testing

[0095] Samples were around 0.2-0.5 mm thick. Circular samples for the permeation measurements were obtained by stamping. The sample was placed in a Millipore HP sample holder (active area 9.6 cm2) for permeation testing. In the holder a porous stainless steel filter plate was applied to support the sample during the high-pressure conditions. The sealing between feed and permeate side was obtained by an O-ring placed between the sample and the feed side of the module. An additional sealing was used to prevent leakages towards the external environment.

[0096] Permeation experiments were conducted in a home-made 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:

[0097] 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 incorrectly be assessed as permeating species.

[0098] Subsequently the upstream side of the sample was exposed to hydrogen at approximately 20 bar, and the downstream side was monitored until steady-state conditions were achieved.

[0099] 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 / diffusion mechanism principle.

[0100] Results gas permeability testing

[0101] Figure 3A shows a permeability graph wherein H2 permeability is measured for samples comprising polyamide- 11 and rGO, As can be seen for all samples a decreased permeability can be seen with increasing concentrations of reduced graphene oxide.

[0102] Mechanical properties

[0103] 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.

[0104] The compression moulding was performed according to ISO 293:2023 by using flash moulds and a compression of 5 MPa at 240°C for PA11 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.

[0105] 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.

[0106] The tensile testing was performed on a Tinius Olsen H10ST according to ISO 527-2:2019.

[0107] 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.

[0108] Figure 4A shows the obtained tensile moduli for various samples, results of which are given in Tables 1 and 2 above. Figure 4B shows the relative change of the tensile moduli compared to neat polyamide- 11. A maximum in tensile modulus is found for an rGO concentration of 2.2 wt%. The composite with 3.6 wt% rGO shows a reduced tensile modulus compared to neat polyamide- 11. Figure 5A shows the ultimate strength, as well as the corresponding elongation at break in %, as a function of the rGO concentration. Figure 5B shows the change in these parameters compared to neat polyamide- 11 (0% rGO). A corresponding anomaly for 0.3 wt% is observed also in these mechanical properties as for the hydrogen permeation experiments of Figs. 3A and 3B. Figure 5B shows that a an optimum for a combination of ultimate strength and elongation at break is obtained at around 0.3 wt% rGO.

[0109] Impact strength measurements, performed by a Charpy notched impact test, are shown in Figure 6A, with their respective changes compared to neat polyamide- 11 (0% rGO) shown in Figure 6B. A peak at 0.3 wt% to higher impact strength is observed, as compared to composites with higher rGO concentrations, which show a lower impact strength than the polyamid-11 without rGO. These results again confirm that concentrations of rGO around 0.3 wt% are surprisingly beneficial for the composite compared to bare polymer (no rGO) and composites with higher rGO concentrations, e.g., higher than 2 wt%.

[0110] Scanning electron microscopy

[0111] Neat PAI 1 and PAI 1 / 0.3 wt% graphene composite samples were prepared by cryo-cracking in liquid nitrogen. Both sides of the cracked interface were investigated in SEM. The samples were coated for 30 s using an Au / Pb sputter coater.

[0112] The samples were characterized using a Zeiss Merlin Field Emission Gun (FEG) - Scanning Electron Microscopy (SEM). A voltage of 2-3 eV and a probe current of 1.0 nA was applied and the in-lens detector was used.

[0113] Figure 7 shows scanning electron microscopy images displaying the detailed structure of cross-sections of extruded sheets of neat PA11. Figure 8 shows scanning electron microscope images of the PA11- graphene composite, here with 0.3 wt% reduced graphene oxide. Figure 7A shows the neat PA11 displaying typical morphology and Figure 7B shows the cross-section surface of the neat PAI 1 surface at higher magnification.

[0114] Figure 8A shows the PAI 1-rGO composite in which 2 rGO particles, which can be seen by having a lighter, almost white shade of grey in the images, can be seen oriented along the extrusion direction, which is parallel to the indicated sample edge 810. Figure 8B shows an enlarged section, in which three rGO particles are indicated with respective size measurements. The orientation of the rGO particles relative to the sample surface can be seen here as well. Figure 8C shows a close-up of one of the rGO particles, while Figure 8D displays a close-up of another rGO particle. It can be derived from the images of Figure 8, including a comparison with the images of Figure 7, that the reduced graphene oxide particles are dispersed in the PAI 1 matrix.. It can be further observed that the adhesion between the reduced graphene oxide and PAI 1 matrix is strong as seen in Figure 8C and 8D.

[0115] Example compounds for blow moulding

[0116] Further compounds of the PAI 1-rGO composite examples were made for blow moulding applications. Two approaches were conducted.

[0117] In the first approach, the compound denoted as BMC1 was extruded after mixing 7.5% of a master batch comprising 96% neat PA 11 (Rilsan® BESNO TL, Arkema) and 4 wt% rGO with neat blow moulding grade PAI 1 (Rilsan® BESN BLACK Pl 23 TL, Arkema). Compound BMC1 thus comprised about 0.3 wt% rGO.

[0118] In the second approach, the compound denoted as BMC2 was extruded after mixing 7.5wt% of a masterbatch comprising 96 wt% Rilsan® BESN BLACK P123 TL and 4wt% rGO, with 92.5 wt% blow moulding grade PAI 1.

[0119] Both compounds BMC 1 and BMC2 were extruded one time more to make sample sheets for further evaluation, such as hydrogen permeation experiments.

[0120] The above details are indicated in Table 3 below, which further includes measured melt flow rates of compounds BMC1, BMC2, neat PAI 1 reference (BESNO TL) and a blow moulding PAI 1 reference (BESNBLACK Pl 23 TL). The melt flow rates of several of these compounds were measured using a Melt Index Tester PCE-MFI 400. The MFR of the neat reference was too high to measure at the 21.6 kg load. The MFR of the blow-moulding reference was too low to measure at 11.6 kg load.

[0121] Table 3: Measured melt flow rates at 250 °C, with 21,6 and 11.6 kg loads for the samples suitable for blow moulding. Standard deviations for measured MFRs are given.

[0122] The melt flow rate for BMC1 of 5.6 g / 10 min is higher than that of BMC2 of 1.7 g / 10 min, and much closer to the melt flow rate of 6.4 g / 10 min of a blow moulding PAI 1 reference (BESN BLACK P123 TL). These results also show the large effect on melt flow rate due to the presence of graphene at relatively low amounts. While the addition of graphene lowers the melt flow rate, the blending of the masterbatch comprising neat PAI 1 and rGO with a blow moulding grade PAI 1 resulted in a melt flow rate of 5.6 g / 10 min, still lower than the melt flow rate of the blow moulding grade PAI 1 reference, 6.4 g / min. Lowering of the melt flow rate is beneficial for blow moulding, since it indicates an increase of the melt strength and a decrease in sagging during the blow moulding process (increased parison stiffness). The increase of the melt flow rate by including the neat PAI 1 allows the blow moulding to be done within the same processing parameters as blow moulding grade PAI 1 without graphene.

[0123] The samples BMC 1 and BMC2 are examples of another aspect of the present patent disclosure, namely a method of producing a blow moulding grade PA- 11 composite material. The method comprises providing a master batch polyamide- 11 -based composite material comprising a blow moulding grade polyamide- 11 -based matrix and reduced graphene oxide in an amount of 2%-8%, preferably 3%-7.5% in weight per weight of the blow moulding grade polyamide- 11 -based composite material, and diluting the master batch polyamide- 11 -based composite material with neat polyamide- 11 or blow-moulding grade polyamide-11 in order to obtain the blow moulding grade PA-11 composite material. The neat polyamide- 11 and blow-moulding grade polyamide-11 added during the diluting do not comprise graphene or reduced graphene oxide, so that a lower concentration of reduced graphene oxide is obtained in the final blow moulding grade PA- 11 composite material than in the master batch. Beneficially, the blow moulding grade PA- 11 composite material has a reduced hydrogen permeability compared to blow moulding grade PA- 11 without reduced graphene oxide, and in addition the composite material comprises all the desirable properties for blow moulding.

[0124] The disclosure comprises the following examples:

[0125] 1. Assembly (100) for hydrogen storage and / or transport, the assembly comprising:

[0126] - a hollow solid body (101); and

[0127] - at least one hydrogen barrier lining (102) arranged along a surface of the hollow body (101); wherein the at least one hydrogen barrier lining (102) comprises a polyamide- 11 -based composite material (200) comprising a polyamide- 11 -based matrix (202) and reduced graphene oxide (201) in an amount of 0.1-8% in weight per weight of the polyamide-11-based composite material (200).

[0128] 2. Assembly (100) according to example 1, wherein the reduced graphene oxide (201) is distributed in the polyamide-11 -based matrix (202).

[0129] 3. Assembly according to example 1 or 2, wherein the reduced graphene oxide (201) is uniformly distributed in the polyamide-11 -based matrix (202).

[0130] 4. Assembly according to any one of the preceding examples, wherein the polyamide-11 -based composite comprises reduced graphene oxide (201) in an amount of 0.1%-2.5% in weight per weight of the polyamide-11 -based composite material (200).

[0131] 5. Assembly according to any one of the preceding examples, wherein the polyamide-11 -based composite comprises reduced graphene oxide (201) in an amount of 0.2%-0.4% in weight per weight of the polyamide-11 -based composite material (200).

[0132] 6. Assembly (100) according to any one of the preceding examples, wherein the surface of the hollow solid body (101) is an inner surface (101a) of the hollow solid body (101).

[0133] 7. Assembly (100) according to any one of the preceding examples, wherein the hollow solid body (101) is a tank, a vessel, a pipe, a joint, or a cylinder.

[0134] 8. Assembly (100) according to any one of the preceding examples, 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.

[0135] 9. Assembly (100) according to any one of the preceding examples, wherein the hollow solid body (101) is a hollow stainless-steel body, a hollow carbon or glass fibre winded body, or a hollow polymer body. 10. Assembly (100) according to any one of the preceding examples, wherein the hydrogen barrier lining (102) is attached to the hollow solid body (101) using an adhesive.

[0136] 11. Assembly (100) according to any one of the preceding examples, wherein the hydrogen barrier lining (102) is attached to the hollow solid body in a binder-free manner.

[0137] 12. Polyamide- 11 -based composite material (200) comprising a polyamide-11-based matrix (202) and reduced graphene oxide (201) in an amount of 0.1%-8% in weight per weight of the polyamide-11- based composite material (200).

[0138] 13. Polyamide- 11 -based composite material (200) according to example 12, wherein the reduced graphene oxide (201) is distributed in the polyamide-11 -based matrix (202).

[0139] 14. The polymer based composite material (200) according to example 13, wherein the reduced graphene oxide (201) is uniformly distributed in the polyamide-11-based matrix (202).

[0140] 15. Polyamide-11 -based composite material (200) according to any one of examples 12 to 14, comprising reduced graphene oxide (201) in an amount of 0.2%-0.7% in weight per weight of the polyamide- 11 -based composite material (200).

[0141] 16. Polyamide-11 -based composite material (200) according to any one of examples 12 to 15, wherein the amount of reduced graphene oxide (201) in the polyamide- 11 -based composite material (200) is 0.2%-0.4% in weight per weight of the polyamide-11-based composite material (200).

[0142] 17. Polyamide-11 -based composite material (200) according to any one of examples 12 to 15, wherein the amount of reduced graphene oxide (201) in the polyamide- 11 -based composite material (200) is 2%-8%, preferably 3%-7.5% in weight per weight of the polyamide-11-based composite material (200).

[0143] 18. Polyamide-11 -based composite material (200) according to example 12-17, wherein a hydrogen permeability as measured according to ASTM D1434-82, procedure M, of the polyamide- 11 -based composite material is reduced by at least 15%, preferably at least 20%, more preferably at least 30% compared to neat polyamide-11.

[0144] 19. Polyamide-11-based composite material (200) according to example 18, in dependence of example 15 or 16, wherein the hydrogen permeability as measured according to ASTM D1434-82, procedure M, of the polyamide-11 -based composite material is reduced by at least 30% compared to neat polyamide-11. 20. Polyamide-11-based composite material (200) according to example 19, having: an elongation at break as measured according to ISO 527-2 at 23 °C that is increased by at least 100%, preferably 130%, compared to neat polyamide- 11 ; and / or a Charpy notched impact strength as measured according to ISO 179:2010 at 23 °C that is increased by at least 8%, preferably 10%, compared to neat polyamide-11.

[0145] 21. Method for manufacturing an assembly for hydrogen storage and / or transport (100) according to any one of examples 1 to 11, comprising lining a surface (101a) of the hollow solid body (101) with one of the at least one hydrogen barrier linings (102).

[0146] 22. Use of a polyamide-11-graphene composite material (200) according to any one of examples 12-20 as a hydrogen barrier lining (102).

[0147] 23. Method of producing a polyamide-11-graphene composite material (200), comprising diluting a polyamide-11-graphene composite material (200) according to example 17 with neat polyamide-11 polymer.

[0148] 24. Use of a polyamide-11-graphene composite material (200) according to example 17 as a masterbatch composition.

[0149] Although the present invention has been described with reference to specific embodiments, also 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 invention 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) arranged along a surface of the hollow body (101); wherein the at least one hydrogen barrier lining (102) comprises a polyamide- 11 -based composite material (200) comprising a polyamide- 11 -based matrix (202) and reduced graphene oxide (201) in an amount of 0.1-8% in weight per weight of the polyamide-11-based composite material (200).

2. Assembly (100) according to claim 1, wherein the reduced graphene oxide (201) is distributed in the polyamide-11 -based matrix (202).

3. Assembly according to claim 1 or 2, wherein the reduced graphene oxide (201) is uniformly distributed in the polyamide-11-based matrix (202).

4. Assembly according to any one of the preceding claims, wherein the polyamide-11 -based composite comprises reduced graphene oxide (201) in an amount of 0. 1%-1% in weight per weight of the polyamide-11 -based composite material (200).

5. Assembly according to any one of the preceding claims, wherein the polyamide-11 -based composite comprises reduced graphene oxide (201) in an amount of 0.1% to 0.7%, 0.1% to 0.5%, or 0.2%-0.4% in weight per weight of the polyamide-11 -based composite material (200).

6. Assembly (100) according to any one of the preceding claims, wherein the surface of the hollow solid body (101) is an inner surface (101a) of the hollow solid body (101).

7. Assembly (100) according to any one of the preceding claims, wherein the hollow solid body (101) is a tank, a vessel, a pipe, a joint, or a cylinder.

8. Assembly (100) according to any one of the preceding claims, 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.

9. Assembly (100) according to any one of the preceding claims, wherein the hollow solid body (101) is a hollow stainless-steel body, a hollow carbon or glass fibre winded body, or a hollow polymer body.

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

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

12. Polyamide- 11 -based composite material (200) comprising a polyamide- 11 -based matrix (202) and reduced graphene oxide (201) in an amount of 0. l%-8% in weight per weight of the polyamide- 11 -based composite material (200).

13. Polyamide- 11 -based composite material (200) according to claim 12, wherein the reduced graphene oxide (201) is distributed in the polyamide-11-based matrix (202).

14. The polymer based composite material (200) according to claim 13, wherein the reduced graphene oxide (201) is uniformly distributed in the polyamide-11-based matrix (202).

15. Polyamide-11 -based composite material (200) according to any one of claims 12 to 14, comprising reduced graphene oxide (201) in an amount of 0.2%-0.7% in weight per weight of the polyamide-11-based composite material (200).

16. Polyamide-11 -based composite material (200) according to any one of claims 12 to 15, wherein the amount of reduced graphene oxide (201) in the polyamide-11 -based composite material (200) is 0.2%-0.4% in weight per weight of the polyamide-11-based composite material (200).

17. Polyamide-11 -based composite material (200) according to any one of claims 12 to 15, wherein the amount of reduced graphene oxide (201) in the polyamide-11 -based composite material (200) is 2%-8%, preferably 3%-7.5% in weight per weight of the polyamide-11 -based composite material (200).

18. Polyamide-11 -based composite material (200) according to claim 12-17, wherein a hydrogen permeability as measured according to ASTM D 1434-82, procedure M, of the polyamide-11 -basedcomposite material is reduced by at least 15%, preferably at least 20%, more preferably at least 30% compared to neat polyamide- 11.

19. Polyamide-11-based composite material (200) according to claim 18, in dependence of claim 15 or 16, wherein the hydrogen permeability as measured according to ASTM D1434-82, procedure M, of the polyamide- 11 -based composite material is reduced by at least 30% compared to neat polyamide-11.

20. Polyamide-11-based composite material (200) according to claim 19, having: an elongation at break as measured according to ISO 527-2 at 23 °C that is increased by at least 100%, preferably 130%, compared to neat polyamide-11; and / or a Charpy notched impact strength as measured according to ISO 179:2010 at 23 °C that is increased by at least 8%, preferably 10%, compared to neat polyamide-11.

21. Method for manufacturing an assembly for hydrogen storage and / or transport (100) according to any one of claims 1 to 11, comprising lining a surface (101a) of the hollow solid body (101) with one of the at least one hydrogen barrier linings (102).

22. Use of a polyamide-11-graphene composite material (200) according to any one of claims 12-20 as a hydrogen barrier lining (102).

23. Method of producing a polyamide-11-graphene composite material (200), comprising diluting a polyamide- 11 -graphene composite material (200) according to claim 17 with neat polyamide-11 polymer or neat blow moulding grade polyamide-11 polymer.

24. Method according to claim 23, wherein, before the diluting, the polyamide-11 -based matrix is a blow moulding grade polyamide-11 -based matrix.

25. Use of a polyamide- 11 -graphene composite material (200) according to claim 17 as a masterbatch composition.

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