WO2021070155A1

WO2021070155A1 - Porous and cellular metals and metal structures of open porosity impregnated with cork, production processes thereof and uses of same

Info

Publication number: WO2021070155A1
Application number: PCT/IB2020/059560
Authority: WO
Inventors: Isabel Maria ALEXANDRINO DUARTE; Susana Cristina DOS SANTOS PINTO; Paula Alexandrina DE AGUIAR PEREIRA MARQUES
Original assignee: Universidade De Aveiro
Priority date: 2019-10-11
Filing date: 2020-10-12
Publication date: 2021-04-15
Also published as: EP4043125A1; PT2021070155B

Abstract

The present invention refers to porous and cellular metals and metal structures of open porosity impregnated with reinforced or non-reinforced cork, to the manufacturing processes thereof and to uses of same. The process for obtaining these new materials and structures comprises filling the open pores of porous and cellular metals and metal structures with a cork-based material in the form of particles, granules, grains, powder, and the like and combinations thereof, obtainable from cork of several types and origins. The developed materials are lightweight and multifunctional, and have improved properties of acoustic insulation and thermal behaviour as well as a significantly enhanced mechanical performance. The present invention pertains to the field of macromolecular organic compounds and the preparation thereof, in particular preparation of macromolecular compounds for porous or cellular materials, such as foams of composite materials, by impregnation, with applications in the construction industry, transportation, furniture and design, footwear, construction of machines, tools and devices.

Description

POROUS METALS AND METALLIC STRUCTURES AND OPEN POROSITY CELLS IMPREGNATED WITH CORK, ITS PROCESSES OF

PRODUCTION AND THEIR USES

Technical domain of the invention

The present invention relates to porous metals and metallic structures of open porosity impregnated with reinforced or not reinforced cork, their manufacturing processes and their uses.

The process of obtaining these new materials and structures comprises filling the open pores of metals and porous and cellular metallic structures, with a cork-based material in the form of particles, granules, grains, powder, the like and their combinations, which can be obtained from cork of various types and origins, such as natural, expanded, recycled cork, waste cork from the industrial process of different granulometries and densities, cork by-products, which can contain at least one natural, synthetic polymer , or recycled, which promotes the connection of cork with each other and with the porous metallic mesh, with the possibility of containing similar micro- or nano-metric reinforcement elements and their combinations, in order to improve the properties of traditional metals and porous and cellular metallic structures of open porosity.

The new materials thus obtained are light, multifunctional, and have improved properties of sound insulation, thermal behavior and a significant increase in mechanical performance.

For this reason they can be advantageously used in civil construction, transport, furniture and design, footwear, construction of machines, tools and devices, such as building houses, cars, trains, boats, airplanes, tools, machines, devices, furniture, design pieces, with good sound-absorbing properties, improved thermal behavior, mechanical performance, low weight with high rigidity and good ability to absorb energy on impact and shock.

Thus, the present invention falls within the technical domain of organic macromolecular compounds and their preparation, in particular the preparation of macromolecular compounds for porous or cellular materials, such as foams of composite materials by impregnation.

Background of the Invention

Solid and porous cellular materials, such as foams and sponges, have become the most promising light and multifunctional materials, being used or tested in a wide range of commercial, biomedical, industrial and military applications. This is mainly due to the rare combination of properties derived from their cellular structures formed by open or closed pores and the properties of the base material (matrix) from which they are made. Its use contributes to an immediate and significant reduction in weight, combined with other benefits, namely excellent noise and vibration damping, acoustic attenuation, impact and shock energy absorption, good filtration capacity, catalytic properties and sound insulation and thermal.

Cork and wood, examples of these materials of natural origin, were the first building materials used by man in the construction of houses, kitchen utensils, fishing and hunting. Recently, a wide variety of cork products have been developed and marketed (Gil, 2019) due to their excellent derived properties cell structure, such as low density, high friction coefficient, low thermal conductivity, high resistance to moisture and the penetration of liquids, resilience and excellent vibration absorption and compressibility.

Inspired by these natural cellular materials, man began to develop similar materials made of polymer, metal and ceramic, called synthetic cellular materials, also called artificial or bio-inspired (Duarte et al., Sei. Techn. Mater. 2018). Among these, porous metals have the best properties for engineering applications. They are easily recyclable and extremely resistant, deforming plastically and absorbing large amounts of energy, in addition to withstanding higher temperatures than cellular polymers. In addition, they are still non-flammable, unlike the known porous and cellular polymers.

In recent years, new products based on these cellular and porous metals have appeared, and consequently new processes or improvement of existing ones, with the objective of making them more multifunctional, with better properties, allowing the control of distribution, size and cell pore geometry during its manufacture, essential to predict its behavior in service, while simultaneously minimizing production costs and waste / waste.

With the rapid advances in additive manufacturing technologies, such as rapid prototyping and 3D printing, new cellular materials have emerged with regular or periodic open porosity cell structures in which they can be easily characterized by a unit cell (Wadley, 2006). Other cellular materials have also emerged, combining materials with a periodic or stochastic network combined with other materials. The metallic matrix syntactic foams, the hollow metallic sphere structures (in English metallic hollow sphere structures) and the hybrid structures of closed porosity metallic foam spheres and polymers (in metallic foam - polymer hybrid structures) are examples of these materials with an easily reproducible unit cell.

The syntactic foams are manufactured by simple infiltration of a molten metal through a predefined arrangement of hollow spheres or porous particles of ceramics, glass and metals, completely filling the empty spaces.

The documents "US2017307137 (Al)", "US2017307138 (Al)" and

"US2018099475 (Al)" disclose cellular structures in which each cell has a straight section of 12 corners, which are generally referred to as honeycomb structures, whose geometry can vary widely, but have, as a common characteristic, to be formed by a matrix of hollow cells arranged between thin vertical walls. Its production consists of the union of cells through processes, such as adhesive bonding (bonding), resistance welding, brazing, diffusion bonding or thermal fusion. All of these production methods are based on how the connection between adjacent plates is made in order to form a "node"

(connection point of the different plates). In these documents, cork is generally referred to here as a thermal insulating material or for solutions where temperature control is important. In addition, the structures disclosed in these documents, share the walls (hollow cells formed between thin vertical walls), cell structures for filling described in these patents are formed by hollow profiles / cells joined by thin walls using a bonding technique, cell structures that are relatively large and with a small number of cells, in which each cell can be manufactured by other processes separately and then joined, the materials that form cellular structures are very varied, for example, steel alloys, titanium alloys, aluminum alloys, magnesium alloys, nylons, plastics, polymers, compounds, fiber-reinforced composites, silicone, semiconductor, papers, rubber, foams, gels, wood, stoppers, hybrid materials (that is, multiple dissimilar materials), materials with shape memory and / or any other suitable materials, which gives them a totally different technical effect from porous and cellular metallic structures of open porosity impregnated with cork .

US20130098203A1 is an example of disclosure of this type of foam. These metallic matrix syntactic foams have density values much higher (> 1000 g / cm ³ ) than conventional closed porosity metal foams (<900 g / cm ³ ), limiting their applications.

Hollow metallic sphere structures are typically obtained by connecting different metallic hollow spheres with a metal, polymer or polymeric foam (Andersen, 2000) and DE3724156A1 also discloses this process. The limitation in the use of these structures is associated with the high cost of producing these hollow spheres, making this process, to obtain it, very uncompetitive.

Hybrid structures of closed porosity metal foam spheres are manufactured by heating an empty mold or hollow structure containing small closed porosity aluminum spheres obtained by powder coated powder method (in English called Powder Metallurgy) by a polymeric material, described in document W02005000502A1. Simplification of the process, automated and continuous production are some of the advantages of these structures (Stõbener et al., 2009). However, this manufacturing process does not guarantee totally perfect spheres, nor is its cell structure controllable during its manufacture.

To overcome these limitations, metallic open porosity foams impregnated with polymer have also recently been developed, completely filling it, as disclosed in WO2012072543A1 and W02018087076A1 and Duarte et al., Polymer Testing, 2018. This type of process, which uses the use of these periodic foams, allows to predict their mechanical properties, and at the same time the mechanical resistance is guaranteed by the use of the polymer. Although the results are promising, in terms of mechanical properties, the use of polymers is the main disadvantage of these foams due to their high flammability, which increases the risk of fire, with the release of toxic gases and fumes. In addition, the fact that some of these polymers are not recyclable, and in others their recycling is not economically viable, makes their use very limited.

In this way, the present invention aims to provide an improved alternative to the materials of the prior art mentioned above proposing, for that purpose, porous metals and metallic structures of open porosity impregnated with cork, instead of polymer.

Summary of the invention

The present invention relates to open porous and cellular metal and metal structures impregnated with cork, which can be reinforced, its manufacturing process and its uses. The porous and cellular open porosity metal and metal structures of the present invention form a matrix containing open pores distributed periodically or randomly with at least one cork material in the form of particles, granules, grains, powder, the like and combinations thereof, and wherein said cork material is incorporated into the pores of the metallic material, as described in claim 1.

These new materials are multifunctional, and have improved properties of acoustic insulation, thermal behavior and a significant increase in mechanical performance. In addition, they are recyclable and non-flammable.

The process of obtaining these new materials and structures comprises filling the open pores of metals and porous and cellular metallic structures, with a cork-based material, such as that described in claim 9.

This process has the advantage of being able to control the dimensions of the used cork powders, in relation to the open pore size of the aluminum foam, with the possibility of recycling and reusing cork products and waste / waste from the cork industry, increasing its life cycle.

The flexibility, input products and the low cost of the process are also advantages in relation to the existing processes, since it is possible to use several by-products and low cost since in the process of the present invention no temperature is applied or, if it is applied, it is always infer the temperature that is needed when compared to other processes, such as, for example, precision casting, melting, additive manufacturing, 3D printing, etc. In this way, these new open porous and cellular metals and metallic structures impregnated with cork, present several multifunctionalities, with better acoustic, thermal and mechanical properties than the individual components, being possible to obtain the necessary characteristics to satisfy the requirements of a given specific application. It also allows the valuation of waste / waste from the cork industry, and "creates" new applications for open porosity cellular and metal structures and metals, that is, to be used also for structural applications.

Description of the Figures

Figure 1: Schematic representation of the process of manufacturing porous and cellular metal structures with open porosity impregnated with reinforced cork or not with reinforcement elements of nano and micrometric size.

Figure 2: Appearance and morphologies of the granules of cork (a) and the cellular cellular metal of open porosity (b), which are the main raw materials used for the manufacture of agglomerates of cork and (c) aluminum foams impregnated with cork.

Figure 3: Compression tension-extension curves, where:

Fig. 3a Displays the respective energy absorption curves,

Fig. 3b shows the tension-extension curves of compression of aluminum foams impregnated with cork and the respective individual components, in which it can be seen, in the aluminum foam of open porosity and in the agglomerate of cork, that the presence of cork inside of aluminum foams leads to increases of 159% and 81% in mechanical strength and energy absorption capacity, respectively, Fig. 3c shows the compression-strain curves of aluminum foams impregnated with cork reinforced or not with graphene oxide and the respective individual components, the open porosity aluminum foam, the cork agglomerate and the cork nanocomposite agglomerate , where it can be seen that the presence of cork inside the aluminum foams leads to increases of 395% in mechanical resistance to an extension of 0.6%, and

Fig. 3d shows the compression-tension curves of aluminum foams impregnated with cork reinforced or not with graphene oxide and the respective individual components, the open porosity aluminum foam, the cork agglomerate and the cork nanocomposite agglomerate , where it can be seen that the presence of cork inside the aluminum foams causes increases of 344% and 238% of mechanical resistance to an extension of 0.5% in a quasi-static or dynamic regime.

Figure 4: Comparison of sound absorption and noise reduction coefficients, in which:

Fig. 4a shows the comparison of the sound absorption and noise reduction coefficients of an aluminum foam impregnated with cork and the respective individual components, the aluminum foam with open porosity and the agglomerate of cork, where there is a significant increase in the coefficient of sound absorption and noise reduction in a wide range of medium-high frequencies (1000 to 3000 Hz), with the typical human frequency being between 1000-2000 Hz,

Fig. 4b shows the comparison of the sound absorption and noise reduction coefficients of an aluminum foam impregnated with cork reinforced with graphene oxide, called cork nanocomposite and the respective individual components, aluminum foam, cork nanocomposite agglomerate, in which the aluminum foam impregnated with cork nanocomposite has a high sound absorption coefficient over a wide range of medium-high frequencies (1000-4000 Hz), with a value of 1 between 1700 Hz and 2000 Hz and a value greater than 0.85 between 1261 Hz and 4000 Hz,

Fig. 4c shows the comparison of the sound absorption and noise reduction coefficients of aluminum foam and cork and aluminum foam impregnated with cork reinforced with graphene oxide, called the cork nanocomposite and the respective individual components, a aluminum foam, cork agglomerate, cork nanocomposite agglomerate, in which the aluminum foam impregnated with cork nanocomposite has a high sound absorption coefficient over a wide range of medium-high frequencies (1000-4000 Hz), with a value of 1 between 1700 Hz and 2000 Hz and a value greater than 0.85 between 1261 Hz and 4000 Hz.

Figure 5: Comparison of the thermal conductivity values of aluminum foams impregnated with cork reinforced or not with graphene oxide, with their individual components, the open porosity aluminum foam and the cork agglomerate, where it is verified that these ([ 0.091 W / (mk)] and 0.101 W / (mk)] have higher values than samples of reinforced agglomerated cork ([0.057 W / (mk)]) or not reinforced

([0.055 W / (m.k)]) of graphene oxide.

Figure 6: Sequence of 2s images of a sample flame test, in which:

Fig. 6a refers to a sample (25 ^c 25 ^c 25 mm) of agglomerate with graphene oxide (a) and a sample (25 ^c 25 x 25 mm) of aluminum foam impregnated with cork reinforced with graphene oxide , called the cork nanocomposite, where it is found that the flame extinguishes more quickly in aluminum foams of open porosity impregnated with graphene oxide reinforced cork, and

Fig. 6b refers to a sample (25 ^c 25 ^c 25 mm) of cork agglomerate, a sample (25 ^c 25 ^c 25 mm) of aluminum foam and cork, a sample (25 ^c 25 ^c 25 mm) of cork agglomerate reinforced with graphene oxide, referred to as cork nanocomposite and of a sample (25 ^c 25 x 25 mm) of aluminum foam impregnated with cork nanocomposite where it is verified that the flame extinguishes faster in the foam of open porosity aluminum impregnated with graphene oxide reinforced cork.

Description of the invention

The present invention concerns the development of new metals and porous and cellular metallic structures of open porosity impregnated with reinforced or not reinforced cork, which comprise the filling of open pores, with a periodic or stochastic arrangement, by a cork-based filling material. .

1. Porous or cellular metal or a porous or cellular structure

Porous metals, cellular metals or porous or cellular structures are characterized by being constituted mostly of open, interconnected pores, which share the edges, forming three-dimensional arrangements periodically or stochastically distributed, which include metallic foams and metal sponges, and metallic cell structures, which include periodic cellular materials with different topologies, namely but not limiting, honeycomb, lattice lattices or prismatic. Materials of this type suitable for use within the scope of the present invention are, for example, open metal foams with a pore size of 5 ppi to 500 ppi (conversion: internationally this represents m ² ) manufactured by the precision casting method designated in English by Investment Casting and metallic cell structures manufactured by additive manufacturing technologies, such as rapid prototyping and 3D printing of metals, preferably presented with a variable dimension from 1 ppi to 500 ppi, more preferably from 10 ppi to 250 ppi, even more preferably from 50 ppi to 150 ppi, or from 75 ppi to 100 ppi.

2. Metallic matrix

The metallic matrix consisting of at least one metal or metallic alloy, are, for example, aluminum, magnesium, manganese, copper, silicon, zinc, tin, nickel and their alloys, used for the different structural and functional applications of this type of metals , such as acoustic and thermal and water filtration.

3. Cork-based filling material

Cork is a 100% natural material, of vegetable origin from the bark of cork oaks (Quercus suber), rich in suberin, a wax synthesized by the cells of the cork oak. It is highly hydrophobic, essentially comprising two reactive groups, a polyaromatic and a polyaliphatic group, each of which, respectively, is based on monomers of hydroxycinnamic acids and derivatives, such as feruloiltyramine, and monomers of a-hydroxy acids, such as 18-hydroxyoctadec-9-enoic) and oc, w-diacids, with for example octadec-9-ene-l, 18-dioic acid, which gives cork unique properties: - It is extremely light (eg natural cork: 160 - 260 kg / m ³ , granulated cork: 60 - 160 kg / m ³ , agglomerated cork: 140 - 600 kg / m ³ ), smooth and pleasant to the touch, which has a great elasticity and resilience, easily recovering its original shape, after being subjected to pressure;

- It is impermeable to both liquids and gases (does not rot), avoiding, for example, water absorption;

- It is very resistant to fire, does not ignite or expels toxic gases during combustion;

- Supports large variations in temperature and humidity;

- It presents low thermal conductivity, being, therefore, excellent thermal insulators, which is due to air inside the cells;

- It has a high noise and vibration absorption capacity, being, therefore, excellent acoustic insulators;

- It also has a good capacity to absorb impact energy.

Thus, cork is currently used for various purposes, for example, wine closures (stoppers for wine bottles), in footwear, furniture, decoration and design, in the construction of buildings for sound and thermal insulation in floors, walls, doors , windows, roofs, or for means of transport (cars, airplanes, trains, boats, etc.). Cork, as well as being one of the most environmentally friendly materials, recyclable, reusable, non-flammable.

Within the scope of the present invention, the cork material can be used in expanded form, in the form of particles, grains, granules or powder of different densities and / or particle sizes. This cork can come from recycled cork, cork waste from industrial processes, such as crushing, sanding powder, or technical products with floating powder, among others, or from the mixture of more than one of the varieties of cork waste or cork by-products, such as cork stoppers, from pure and expanded black agglomerates, which may contain at least one polymer of natural, synthetic or recycled origin, such as polyurethane, silicone, epoxide, polyethylene, polypropylene, ethylene, alkyl or aryl, polystyrene and polycarbonate.

In quantitative terms, the cork material can be used in amounts ranging from about 3% -30% by weight of polymer of natural origin, synthetic or recycled according to the intended application, with about 0% -15% by weight additives and about 0% -10% and 0% -50% by weight of nanometric and micrometric size reinforcement elements, respectively.

In addition, the cork material used can still be subject to pre-treatments, such as granulation processes, particle size reduction such as cutting, crushing, grinding and separation processes by sizes, such as sieving that promotes separation and ordering by the size of particles, granules or grains.

Cork should have a smaller size distribution than the open pore size distribution of the metal and the porous and cellular metallic structure to be used, to facilitate its incorporation in these pores.

In a preferred embodiment, the cork material has a variable dimension between nanometer scale and micrometric scale. The cork-based filling material can be reinforced, being prepared by mixing the raw materials, which can be optionally functionalized, for example by physical or chemical modification, as well as by removing impurities, to promote better adhesion between the various constituents, namely, washing with one or more solvents and drying cork residues, or using polymers previously functionalized with functional groups of thermosets such as, for example, epoxide and polyurethane.

The non-reinforced cork-based filling material is obtained by simply mixing the cork, in the form of particles, granules, grains or powder, with at least one polymer, which may or may not be functionalized with the addition of processing additives. , using mixing techniques used for this purpose, with, for example, a mechanical mixer.

The filling material based on reinforced cork is obtained using the usual techniques of incorporating reinforcement elements of nano and micro size, with the addition of at least one functionalized or not polymer, of natural, synthetic or recycled origin, and with the adding or not processing additives. For example, the incorporation of reinforcement elements of micrometric size into cork using a mechanical mixer, or the incorporation of reinforcement elements of nanometric size in cork using the layer by layer technique, known in English layer by layer technique, which can be aqueous solutions are used for this purpose.

In a preferred embodiment, the filling material is reinforced.

Reinforcement elements of the cork material suitable for the present invention are materials dispersed in the continuous matrix, which include fibers, particles, tubular structures or micro and nano-scale sheets of polymers, ceramics, glass and metals, carbon-based materials, the like and their combinations. If the reinforcement element is of micrometric size, it is called a composite material, or simply "composite cork". If the dispersed phase is nanometric in size, it is called nanocomposite material or simply "cork nanocomposite".

Polymeric materials, or simply "polymers" are materials of natural, synthetic or recycled origin, similar and their combinations, which according to mechanical characteristics, can be divided into thermoplastics, thermosets and elastomers. Thermoplastics include the known plastics, which can be melted several times and in some cases dissolved in various solvents, and are therefore recyclable materials. The thermosets are rigid and fragile, being very stable to temperature variations, although the heating of these polymers causes their decomposition before melting, and is therefore not easy to recycle. Elastomers have high elasticity, not being rigid or liable to be melted, which reduces the possibilities for recycling.

In a preferred embodiment, the filler material is reinforced with one or more of the following polymers of the epoxide or polyurethane type.

Suitable additives for this purpose are substances used in small amounts, used to modify and / or improve various properties such as promoting processability, providing thermal stability, coloring, improving antistatic properties, surface hardness, fire resistance, among others. In a preferred embodiment, the filler material, reinforced or not, comprises one or more additives.

4. Metal matrix reinforcement elements

The reinforcement elements can be of natural, synthetic or recycled origin, including, but not limited to, ceramic, polymer and metal, carbon derivatives, for example graphene oxide, in the form of tubular structures, sheets, particles, fibers, of micrometric size or nanometric, similar or combinations thereof.

These new porous and cellular open porous and cellular metal structures and impregnated with reinforced or not, light and multifunctional cork can integrate the usual transformation processes of the various companies related to the metal industry and porous and cellular metallic structures with open porosity and cork industry.

5. Process for obtaining porous metals and metallic structures of open porosity impregnated with cork

The present invention also refers to the production process of these new metals and porous and cellular metallic structures of open porosity impregnated with reinforced or not reinforced cork, which is outlined in Figure 1.

After the selection of the raw materials, depending on the desired final material and according to what was previously described, the cork-based filling material is prepared, which can be reinforced or not, also depending on the desired final material. . Then, the open pores of a metal or a cellular or porous structure are filled with the cork-based filling material. Finally, the resulting material is densified and cured. The preparation of the filling material is carried out by mixing the various components selected for the purpose, namely cork, the polymer, if the filling material is to be reinforced, with the possibility of adding processing additives and reinforcement elements.

The mixing is carried out in a single phase, i.e. promoting the contact of all selected components simultaneously, under environmental conditions with vigorous mechanical agitation.

In case it is desired to obtain filling material with reinforced cork, the incorporation of the reinforcement elements can be carried out using dry and / or wet techniques, such as mechanical stirrers, colloidal processing and step-by-step technique, similar and combinations, selected according to the chemical, physical characteristics, the shape, geometry and size distribution of these reinforcement elements.

The step of filling the open pores of metals and porous and cellular metallic structures is carried out by pouring the filling material, prepared according to the previously described, into the open pores of a porous or cellular metal or metallic structure with a distribution periodic or random, preferably performed under vibration and / or pressure, to ensure the filling of these pores.

For this purpose, molds or hollow structures of thin walls of simple and complex geometries can be used, optionally with the use of coatings with non-stick properties, such as tracing paper, teflon sheets, Kraft paper, paper and films based on of silicone to facilitate the extraction of the new materials resulting from it. Finally, the material resulting from the described steps is subjected to a stage of densification and curing carried out under controlled conditions, in air or in a vacuum, preferably in air without application of temperature or, also, with the possibility of varying the temperature, typically up to 250 ° C.

For this purpose, said material, which is formed by a metal skeleton with pores filled, at least partially, with a cork-based material, is pressed by exerting a pressure in order to obtain the required density for each application, but that ensures that the metal or an initial porous and cellular metallic structure of open porosity is not damaged.

This is followed by the curing step, which refers to the curing of at least one polymer material by crosslinking, the beginning of which can take place by chemical additives (e.g. water), heat or ultraviolet light.

Finally, the resulting material, metal or a porous and cellular metallic structure impregnated with cork, is extracted from the mold.

In summary, the process of producing open porous and cellular metal and metallic structures impregnated with cork, of the present invention, comprises the following steps: a) Preparation of cork-based filling material; b) Filling the open pores of a metal or a cellular or porous structure with the filling material of (a); c) Densification and curing of the material of (b).

Definitions : In the context of the present invention, the percentages mentioned in the present description and claims refer to mass percentages.

In the context of the present invention, the term "comprising" is to be understood as "including, among others". As such, the term should not be interpreted as "consisting only of".

Note that any X value presented in the course of this description should be interpreted as an approximate value of the real X value, since such an approximation to the real value would be reasonably expected by the person skilled in the art due to experimental and / or measurement conditions that introduce deviations from the real value.

In the context of the present invention, the ranges of values presented in the present description are intended to provide a simplified and technically accepted way to indicate each individual value within the respective range. By way of example, the expression "1 to 2 or" between 1 and 2 means any value within this range, including the limit values. All values mentioned should be interpreted as approximate values. For example, a reference to "0.1" means "about 0.1"

In the present invention, the term "cellular metal" refers to porous metals, solids characterized by being composed mostly of open pores, which include metallic foams and metallic sponges obtained by processes commonly used for this purpose, and metallic cell structures. , which includes periodic cellular materials with different topologies, namely but not limited to, honeycomb, lattice lattices or prismatic, obtained mainly by additive manufacturing technologies, such as rapid prototyping and 3D printing. In the present invention, the term "open porous cell metal" refers to solid porous metals made up mostly of open, interconnected pores that share the edges, forming three-dimensional arrays distributed periodically or stochastically.

The number of these pores that fills an inch is called "pores per inch", PPI and is a way of characterizing the pore size of an open porosity cellular metal.

In the present invention, the term "metal" refers to metals and their metal alloys, namely, but not limited to, copper and its alloys, manganese and its alloys, aluminum and its alloys, magnesium and its alloys, zinc and its alloys .

In the present invention, the term "porous and cellular metallic structure" encompasses preferably periodic cellular structures with different topologies, namely, but not limited to, honeycomb, lattice lattices or prismatic, obtained mainly by additive manufacturing technologies, such as prototyping and 3D printing.

In the present invention, the term "porous and cellular metal impregnated with reinforced or not cork" refers to materials typically constituted by porous and cellular metal formed by a network of open pores distributed periodically or randomly, which their pores / voids are filled with a cork-based filling material, in the form of cork particles, cork grains, cork granules, natural cork powder, recycled, cork residues from the production process or a by-product or product from cork, similars and their combinations, and at least one natural, synthetic, recycled polymer, which may contain nano or micro size similar reinforcement elements and their combinations to modify and improve thermal, acoustic and performance properties mechanical, so its combination results in the characteristics of the product.

In the present invention, the term "reinforcement element" refers to materials dispersed in a continuous matrix, in this case in cork-based filling material, which include fibers, particles, tubular structures or sheets in micro and nano scale of polymers, ceramics, glass and metals, carbon-based materials, the like and their combinations. If the reinforcement element is of micrometric size, it is called a composite material, or simply "composite cork". If the dispersed phase is nanometric in size, it is called nanocomposite material or simply "cork nanocomposite".

In the present invention, the term "cork material" or simply "cork" refers to particles, grains, granules or powder from natural cork, colmated natural cork, agglomerated cork, micro agglomerated cork, recycled cork, waste cork, cork expanded, similar or their combinations.

In the present invention, the reinforcing elements may or may not enter the composition of the cork-based filler material formulations, used to fill the open pores of the metals and cellular and porous structures, which give rise to the new materials and structures object of this invention .

The term "cork-based material" in the context of the present invention refers to cork material, as defined above, combined with another material or materials, such as, for example, a polymeric material of natural, synthetic or recycled.

The term "polymeric material", or simply "polymer" refers to material of natural, synthetic or recycled, similar and their combinations which, according to the mechanical characteristics, can be divided into thermoplastics, thermosets and elastomers. Thermoplastics include the known plastics, which can be melted several times and in some cases dissolved in various solvents, and are therefore recyclable materials. The thermosets are rigid and fragile, being very stable to temperature variations, although the heating of these polymers causes their decomposition before melting, and is therefore not easy to recycle. Elastomers have high elasticity, not being rigid or liable to be melted, which reduces the possibilities for recycling.

The term "additive" or "processing additives", in the context of the present invention, refers to substances used in small quantities, used to modify and / or improve various properties such as promoting processability, providing thermal stability, coloring, improving properties antistatic, surface hardness, fire resistance, among others.

It is an objective of the present invention to obtain porous metals and metallic structures of open porosity impregnated with reinforced cork or not with reinforcing elements, which exhibit additional characteristics of the combination of these cellular metal and cork materials, which provide an improvement of comfort at the level acoustic, thermal, as well as better mechanical performance, presenting great versatility in its application.

Detailed description of the invention

The present invention relates to the development of porous metals and metallic structures of open porosity impregnated with cork characterized by comprise at least two porous and cellular materials or structures or cellular materials, the first (1) comprising a metal or metal alloy matrix, with open pores distributed periodically or randomly, and the second (2) a cellular material natural, cork in the form of particles, granules, grains, powder, similar and their combinations, which can be made of natural, expanded, recycled cork, waste cork from the industrial process, cork by-products, which can be reinforced with reinforcement elements of natural, synthetic or recycled origin, namely but not limited to metal, polymer or ceramic, glass and carbon of micro- or nano-metric size namely but not limited in the form of tubular structures, fibers, particles and their combinations, containing at least one synthetic, natural or recycled polymer, and optionally, with the addition of processing additives.

In one embodiment, porous and cellular open porosity metal and metal structures impregnated with cork are characterized by comprising:

(a) a porous and cellular metal or metal structure of open porosity obtained by any process one of the processes used for this purpose, including additive manufacturing technologies;

(b) a natural cellular material based on cork in the form of particles, granules, grains, powder, similar and combinations thereof, which can be natural, expanded, granulated, recycled cork, waste cork from the industrial process of different granulometries, cork by-products and cork residues, similar and their combinations; and optionally (c) one or more synthetic, natural or recycled polymers that may or may not be previously subjected to physical or chemical modification to improve compatibility with the other components, with the possibility of adding processing additives.

In one embodiment, porous and cellular open porosity metal and metal structures impregnated with cork composite are characterized by further comprising:

(a) 0.1% - 50% by weight of reinforcement elements of micrometric size of natural, synthetic, recycled, similar origin and combinations thereof, including, but not limited to, fibers, particles, tubular structures, or sheets, similar and their combinations made of metal, carbon, ceramic or polymer, similar and their combinations.

In one embodiment, the porous metals and metal structures of open porosity impregnated with cork nanocomposites are characterized by also comprising,

(a) 0.1% -10% by mass of nanometric size reinforcement elements of natural, artificial or recycled origin, similar and combinations thereof, including but not limited to fibers, particles, tubular structures, or sheets, the like and their combinations, made of metal, carbon, ceramic or polymer, with the possibility of adding other reinforcement elements of micrometric size.

In one embodiment, the porous and cellular metal and metal structures of open porosity impregnated with cork composite are characterized by the aforementioned cork-based material to be selected from the group comprising particles, granules, grains, powder, derived from natural, expanded, granulated, recycled cork, cork waste from the industrial process of different particle sizes, cork by-products and cork waste, similar and their combinations.

In one embodiment, the porous and cellular metal and metallic structures of open porosity impregnated with simple cork, cork composite or cork nanocomposite are characterized by the fact that cork may or may not be previously subjected to treatments, such as a physical or chemical modification for improve compatibility for different components.

In one embodiment, the porous and cellular metal and metal structures of open porosity impregnated with simple cork, cork composite or cork nanocomposite are characterized in that said polymer is selected from the group comprising similar, synthetic and recycled polymer, and combinations thereof. , such as thermoplastics, thermosets and elastomers, for example, polyethylene, polyurethane, silicone, epoxide, polypropylene, ethylene, alkyl or aryl anhydride, polystyrene, polycarbonate and the like and combinations thereof.

In one embodiment, the porous and cellular metal and metal structures of open porosity impregnated with simple cork, cork composite or cork nanocomposite are characterized in that the said polymer can be subjected to a physical or chemical modification to improve the compatibility of the different components and its uniform distribution of components, such as cork and reinforcement elements, if any. In one embodiment, porous and cellular open porous metals and metallic structures impregnated with cork composite or cork nanocomposite are characterized by the reinforcement elements being selected from the group comprising reinforcements of natural, synthetic, recycled, similar nature and combinations thereof .

In one embodiment, open porous and cellular porous metals and metal structures impregnated with cork composite or cork nanocomposite are characterized in that the reinforcement elements are selected from the group comprising fibers, particles, tubular structures or sheets on a micrometric scale and / or nanometric, similar and their combinations.

In one embodiment, porous and cellular open porous metals and metal structures impregnated with cork composite or cork nanocomposite are characterized in that the reinforcement elements are selected from the group comprising ceramics, metals and polymers, glass, carbon, for example, graphite, graphene, graphene oxide, carbon nanotubes, nano or micro graphite, nano or microparticles or ceramic fibers such as silicon carbide, metals, glass and polymers and the like and combinations thereof.

In one embodiment, porous and cellular open porosity metal and metal structures impregnated with cork composite or cork nanocomposite are characterized in that the reinforcing elements of micrometric or nanometric size can be subjected to a physical or chemical modification to improve compatibility to the different components and their uniform distribution in the cork matrix. The invention also relates to the process of producing open porous and cellular metal and metallic structures impregnated with cork, natural cellular material, reinforced or not with reinforcing elements, which comprises the following steps: a) Preparation and selection of raw materials cousins; b) Preparation of the filling material based on reinforced or not reinforced cork; c) Filling the open pores of a metal or cell or porous structure with reinforced or not reinforced cork-based filling material; and d) Densification and curing of cellular material made of metal and cork, whether reinforced or not.

The invention also concerns the uses of these new ones, which are light and multifunctional for use in military, engineering and commercial applications. These are light, recyclable, reusable, in addition to presenting acoustic insulation properties, improving thermal properties in relation to cork, they have excellent durability, excellent fire behavior with absence or extinguishing of flame and release of toxic gases.

The present invention is useful for developing new porous and cellular materials and structures of metal and cork, obtained by impregnating cork, a natural cellular material in the open pores of a metal or a porous and cellular metallic structure, with the possibility of cork becoming it is reinforced with reinforcement elements of similar size, micro- or nanometer and their combinations, which are light, recyclable, non-flammable, and with high mechanical, acoustic performance and improvement of its thermal properties. The advantages of this invention include, among others, the following:

- Obtaining new porous metals and metallic structures of open porosity impregnated with reinforced or not reinforced cork, light and multifunctional, recyclable and non-flammable for light construction;

- Obtaining new metals and porous and cellular metallic structures of open porosity impregnated with reinforced or not reinforced cork, light for acoustic insulation and with an improvement of thermal conductivity in relation to cork;

- Obtaining new porous metals and metallic structures of open porosity impregnated with reinforced or not reinforced cork, light with good capacity to absorb energy to impact and shock, noise and vibrations that can be used as a core and filling of tubular structures of thin wall of different geometries and sandwich panels for structural applications, respectively.

- Obtaining new metals and porous and cellular metallic structures with open porosity impregnated with reinforced or not reinforced cork, for design and furniture pieces, including the modern one due to its beauty and lightness.

- Increase the range of metal applications and porous and cellular metallic structures with open porosity generally used for functional applications, and can also be used for structural applications, since they are impregnated with reinforced cork or not which increases its mechanical performance.

- Possibility of using waste from cork by-products, such as cork stoppers, from pure agglomerates and blacks expanded through regranulation, from cork waste from the industrial process of different granulometries.

- Recovery of waste from the cork industry.

As main applications, the following can be highlighted:

- The manufacture of furniture, decorative and design pieces;

- The manufacture of lightweight components for sound insulation and noise and vibration damping in the construction of tools, machines and devices.

- The manufacture of light exterior and interior cladding panels for sound and thermal insulation of buildings, houses and auditoriums, as well as in the automotive and aeronautical industry;

- The incorporation of these new cellular metal and cork materials, such as core and filling of sandwich panels and hollow structures for the transport industry, to guarantee a light construction, sound insulation, noise and vibration damping and a good absorption capacity. energy to impact.

- The manufacture of ballistic protection systems for personal protective equipment (eg vests), vehicles and houses.

EXAMPLES

Example 1. Preparation of an open porosity aluminum foam impregnated with cork and its compression behavior

Open porosity aluminum foams impregnated with cork with a density of approximately 178.7 kg / m ³ prepared using granulated cork granules with a particle size between 0.5 mm and 1 mm (Figure 2a).

An open porosity aluminum cellular metal (25 ^c 25 ^c 25 mm) was prepared, with a density of approximately 113.5 kg / m ³ and a pore size of 10 ppi (pores per inch, in English pores per inch obtained for leaking suspensions, in english investment castíng method.

It started with the preparation of the cork-based filling material by mixing 1.5 g of granulated cork powders with a particle size between 0.5 mm and 1 mm, with 10% by weight of polyurethane and 5% by weight. mass of water, using a paddle mixer, for 5 minutes. Water was used as a processing additive to promote the crosslinking of the polymer, that is, its hardening.

The resulting mixture was then poured into a stainless steel mold opened at the top which contained the aluminum foam of open porosity (25 ^c 25 ^c 25 mm) in its cavity (25 ^c 25 ^c 25 mm), which was previously coated with a non-stick film to facilitate the extraction of the resulting aluminum foam and cork.

After filling, the mold was closed at the top and the aluminum cell metal of open porosity impregnated with the resulting cork was compressed only to guarantee its densification, exerting a pressure that does not damage the aluminum foam of initial open porosity.

The closed mold containing the open porosity aluminum foam was then placed in a preheated oven at 140 ° C for 2h. Finally, the open porosity aluminum foam impregnated with cork was extracted from the interior of the stainless steel mold. To compare the mechanical properties of open porosity aluminum foams impregnated with cork, the following samples were prepared:

A. 126 kg / m ³ cork agglomerate (25 ^c 25 ^c 25 mm), using the same methodology described above, but in this case the stainless steel mold was empty, and

B. Cork agglomerate with cork granules of cork size less than 700 pm, in which 20% epoxide (w / w) was used as an adhesive material instead of polyurethane and without the addition of water.

The mechanical properties (method described in example 1) of cork agglomerated with graphene oxide and hybrid nanocomposite structures were also evaluated.

The process of modifying cork with graphene oxide (nanocomposites and hybrid nanocomposite structure) is in accordance with that described in example 3, below.

The mechanical performance of the open porosity aluminum foam samples impregnated with cork produced according to this methodology, were evaluated through compression tests using a speed of 0.1 mm / s, according to ISO 13314: 2011. The behavior the compression of these open porosity aluminum foams impregnated with cork was compared with the behavior of their individual components (open porosity aluminum foams and cork agglomerates). The number of samples tested for each type of material was three.

Figure 3 shows the average voltage-extension curves (Figure 3a) and mechanical energy absorbed per volume unit (Figure 3b) of the different types of samples. The mechanical energy curve absorbed per volume unit is obtained by the integration of the tension-extension curve, according to ISO 13314: 2011.

The results clearly show that the open porosity aluminum foams impregnated with developed cork have better mechanical properties than their individual components, the open porosity aluminum foams and the cork agglomerate samples (Figure 3). The tension-extension curves (Figure 3a) and the respective energy curves absorbed by volume (Figure 3b) of open porosity aluminum foams impregnated with cork are superior to those of open porosity aluminum foams and those of cork agglomerates. For example, for the 0.6 extension, the values of tension and absorbed energy of open porosity aluminum foam samples impregnated with cork are 159% and 81% higher than the values of the initial open porosity aluminum foam, respectively . It is also noted that the yield strength of samples developed from open porosity aluminum foams impregnated with cork is much higher (about 0.344 MPa) than the yield strength of agglomerated cork samples (about 0.116 MPa) .

In the case of samples B (figure 3c), it can be seen that the presence of cork inside the aluminum foams leads to increases of 395% in mechanical resistance to an extension of 0.6%.

The mechanical performance of open porosity aluminum foam samples impregnated with cork produced according to this methodology, were evaluated through quasi-static and dynamic compression tests, using a speed of 0.1 mm / s and 284 mm / s, according to ISO 13314: 2011, respectively, as can be seen in figure 3d. Example 2. Preparation of open porosity aluminum foams impregnated with cork and its acoustic properties

Open porosity aluminum foams impregnated with 50 mm diameter and 25 mm high cork with a density of 230 kg / m ³ were prepared using cork granules with a particle size of less than 700 pm, which were obtained through sieving the initial granules with a size distribution of 5 mm to 10 mm (Figure 2a).

For this purpose, aluminum foams with open porosity of 50 mm in diameter and 25 mm in height were used (Figure 2b), with a density of 117.5 kg / m ³ and with a pore size of 10 ppi (pores per inch, prepared by precision casting method, in english investment castíng method.

It started with the preparation of a cork-based filling material by mixing 6.30 g of cork granules less than 700 pm in size with 20% by weight of epoxide, without using processing additives, using a paddle mixer for this purpose, for 5 minutes.

7 g of the resulting mixture was poured into a cylindrical stainless steel mold opened at the top with an inner cavity (50 mm in diameter and 25 mm in height) where the 50 mm diameter open porosity aluminum foam was previously placed and 25 mm in height, which was under mechanical vibration.

To facilitate the filling of the open pores of the open porosity aluminum foam, the mold containing the open porosity aluminum foam was placed on a vibrating platform. At the end of the pore filling, the mold was closed at the top and the aluminum foam of open porosity impregnated with cork (pores filled with cork) was compressed to ensure its densification, exerting pressure not to damage the aluminum foam of initial open porosity. Then, the mold with the resulting open porosity aluminum foam impregnated with cork was placed in an oven preheated to 80 ° C for 2h. Finally, the open porosity aluminum foam impregnated with cork (Figure 2d) was extracted from the interior of the mold.

Samples of cork agglomerate 50 mm in diameter and 25 mm in height (Figure 2c) with a density of 158 kg / m ³ were prepared from cork granules with a particle size of less than 700 pm, using the same methodology used and described in the preparation of open porosity aluminum foams impregnated with cork, but in this case the cork-based filling material is poured into an empty mold with an inner cavity (50 mm in diameter and 25 mm in height) followed by pressing, curing (80 ° C and 2h), mold extraction.

The acoustic performance and / or the sound absorption efficiency of these open porosity aluminum foams and their individual components were evaluated according to the ASTM E 1050 standard. According to this standard, the test consists of placing a sample with a diameter of 50 mm and 25 mm. mm thick of a given material at the end of the inside of a 50 mm diameter impedance tube. At the other end, there is the sound source, a RG10 noise generator that emits random noise.

There are also two microphones placed inside the tube between the sound source and the sample to be tested, which measures the pressure variations that the sound exerts on the test piece. The measured parameter is the sound absorption coefficient, which is defined as the property that materials have that are capable of transforming part of the sound energy that affects them in another form of energy (eg mechanical or thermal energy). According to the standard, this property is defined as the sound absorption of a medium as the reduction of sound power by dissipation resulting from the propagation of sound in that medium. It depends on the type of surfaces, the angle of incidence of the sound, the frequency of the wave and the application conditions of the system of which the material is a constituent. Thus, a (alpha) is the relationship between the amount of sound energy that is dissipated or absorbed by a given material and that on that material. This varies between 0 (0% absorption) and 1 (100%). The more the% of sound absorbed, the more effective the insulation. This relationship is quantified from 0 to 1, which symbolizes that a material that has a sound absorption coefficient of 0.5 absorbs 50% of the energy that falls on it. This is a property on which materials can be classified, with materials with coefficients equal to or greater than 0.5 being considered absorbent. Another parameter is the NRC indicator, the noise reduction coefficient, in English Noíse Reduction Coefficient, which is the arithmetic mean of the sound absorption coefficients, and for the frequencies 250 Hz, 500Hz, 1000 Hz and 2000Hz, rounded up to multiples of 0.05. The results clearly showed that these open porosity aluminum cellular metals impregnated with cork are materials that can be used for sound insulation, being highly effective noise absorbers in a wide range of medium-high frequencies (1000 to 3000 Hz). Performance is less impressive at low frequencies (below 1000 Hz), as shown in Figure 4a.

For comparison purposes, aluminum foams were also prepared from only new composite samples, with the addition of graphene oxide, according to examples 2 and 3. Figure 4b shows the comparison of the sound absorption and noise reduction coefficients of an aluminum foam impregnated with cork reinforced with graphene oxide, called cork nanocomposite and the respective individual components, aluminum foam, nanocomposite agglomerate of cork. cork, in which the aluminum foam impregnated with cork nanocomposite has a high sound absorption coefficient in a wide range of medium-high frequencies (1000-4000 Hz), with a value of 1 between 1700 Hz and 2000 Hz and a value greater than 0.85 between 1261Hz and 4000 Hz.

Figure 4c shows the comparison of the sound absorption and noise reduction coefficients of aluminum foam and cork and aluminum foam impregnated with cork reinforced with graphene oxide, called the cork nanocomposite and the respective individual components, a aluminum foam, cork agglomerate, cork nanocomposite agglomerate, in which the aluminum foam impregnated with cork nanocomposite has a high sound absorption coefficient over a wide range of medium-high frequencies (1000-4000 Hz), with a value of 1 between 1700 Hz and 2000 Hz and a value greater than 0.85 between 1261 Hz and 4000 Hz.

Example 3: Preparation of aluminum foams of open porosity impregnated with cork and cork reinforced with graphene oxide and their thermal properties.

Open porosity aluminum foams impregnated with simple cork with a density of 230.4 kg / m ³ and open porosity aluminum foams impregnated with graphene oxide reinforced cork with a density of 223.8 kg / m ³ were prepared using particle size granules less than 700 mpi, obtained by sieving the initial granules from 5 mm to 10 mm.

For this purpose, samples of aluminum foams with open porosity (25 ^c 25 ^c 25 mm) with a density of 117.5 kg / m ³ and with a pore size of 10 ppi (pores per inch), prepared by casting method, were used. for accuracy, in english investment castíng method. Commercial graphene oxide, chemically exfoliated and marketed in 0.4% w / w aqueous suspension, was also used as a reinforcement element for cork to prepare open porosity aluminum foams impregnated with graphene oxide reinforced cork (cork nanocomposite).

The open porosity aluminum foams impregnated with cork (25 ^c 25 ^and 25 mm) were prepared using the same methodology described in example 2. 1.60 g of cork granules were mixed with 20% by weight of epoxide. The resulting mixture is poured into the open pores of an aluminum cellular metal (25 ^c 25 ^c 25 mm) with 10 ppi that was inside the cavity (25 ^c 25 ^c 25 mm) in a stainless steel mold placed on a vibrating platform, followed by densification, curing (80 ° C for 2 h) and extraction from the mold. Samples of cork agglomerates (25 ^c 25 x 25 mm) with 154.6 kg / m ³ of density were also prepared following this methodology, in which the filling material was poured into an empty mold with a hollow cavity (25 x 25 x 25 mm).

The open porosity aluminum foams impregnated with reinforced cork, were prepared using graphene oxide as reinforcement elements. The first stage of this process consisted of incorporating and evenly distributing the graphene oxide in the cork granules. This was achieved using the layer by layer deposition technique, in English layer by layer, LBL. For this purpose, the cork granules (<700 mpi) were immersed in successive solutions - aqueous solution of 0.1% by weight of poly (diallyldimethylammonium chloride; 0.1% solution by weight of Poly (sodium 4-styrene sulfonate) and 0.1% solution by weight of poly (diallyldimethylammonium chloride, for 15 minutes, followed by filtration and washing with distilled water, to remove impurities.

Then, these cork granules were immersed in an aqueous solution of 0.1% by weight graphene oxide for 15 min, followed by filtration and washing with distilled water. The agglomerated cork granules containing the graphene oxide nanoparticles were dried in an oven at 40 ° C for 24 h. 1.6 g of these granules were then mixed with and mixed with 20 mass% epoxide. The resulting mixture was poured into the open pores of an aluminum foam of open porosity (25 ^c 25 ^c 25 mm), which is inside a stainless steel mold, which was placed on a vibrating platform under vibration, followed by densification, curing (80 ° C for 2 h) and extraction from the mold.

Likewise, samples of graphene oxide reinforced cork (25 x 25 x 25 mm) with ^{a density of 154.9 kg / m 3} , were prepared using the same methodology described for the preparation of aluminum porosity foams impregnated with reinforced cork graphene oxide, in which the mold was empty.

The thermal conductivities of the different samples were measured (Figure 5), using equipment from the Hot Disk brand, model TPS2500, according to the ISO 22007-2 standard. The measurement is determined using a transient flat area sensor, which is placed between two identical test pieces of the same type of material. This method consists of applying an electric current intensity and the resistance of the propagation of the heat by the sample, that is, it registers the temperature profile inside the sample (axial and radial) as a function of time.

The results (Figure 5) clearly demonstrate that aluminum foams with open porosity are those with a higher value ([0.178 W / (mk)], followed by aluminum foams with open porosity impregnated with cork ([0.091 W / ( mk)]) and those reinforced with graphene oxide ([0.101 W / (mk)]). These samples have higher values than the samples of unreinforced agglomerated cork ([0.055 W / (mk)]) and of agglomerated cork reinforced with graphene oxide ([0.057 W / (mk)]). These open porosity aluminum foams impregnated with reinforced or undeveloped cork have thermal conductivity values that can be used for certain applications, in which it is important to have values higher than those of cork.

There are materials on the market that are used as thermal insulators with values of thermal conductivity similar or even higher than these aluminum foams of open porosity impregnated with reinforced or undeveloped cork

A good thermal insulation must have not only a low thermal conductivity, but also a good thermal diffusion, so that the variations of the outside temperature are not easily transmitted to the interior spaces. Furthermore, they must be chemically inert, dimensionally stable and easy to apply to the surface. The advantage of these resulting aluminum and cork foams is their low density, withstand high temperatures and good resistance to compression. These new open porosity aluminum cell metals impregnated with reinforced or undeveloped cork are important in certain applications where these thermal properties are to be improved, maintaining good sound insulation. Example 5: Preparation of open porosity aluminum foams impregnated with graphene oxide reinforced cork and its flame retardant and flame extinction behavior

Samples of open porosity aluminum foams impregnated with graphene oxide reinforced cork and graphene oxide reinforced cork agglomerates were prepared using the methodology described in example 4. Figure 6a presents a sequence of images from the flame test carried out for each type of sample. The images presented were taken every 2 seconds. The time of extinguishing the flame of the samples was determined by subjecting the samples previously to a flame of a lamp for 5 s, then measuring the time that the flame took to extinguish completely. The results show that the flame extinguishes faster in the foam aluminum foams of open porosity impregnated with reinforced cork of graphene oxide.

Figure 6b refers to a sample (25 ^c 25 ^c 25 mm) of cork agglomerate, a sample (25 ^c 25 ^c 25 mm) of aluminum foam and cork, a sample (25 ^c 25 ^c 25 mm) of cork agglomerate reinforced with graphene oxide, referred to as cork nanocomposite and of a sample (25 ^c 25 x 25 mm) of aluminum foam impregnated with cork nanocomposite where it is verified that the flame extinguishes faster in the foam of open porosity aluminum impregnated with graphene oxide reinforced cork.

References

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Claims

1. Metals and porous and cellular metallic structures of open porosity impregnated with cork characterized by comprising:

- at least one porous or cellular metal or a porous or cellular structure with open, interconnected pores that share the edges, forming three-dimensional arrangements periodically or stochastically distributed, forming a metallic matrix foam of at least one metal or metal alloy, and

- a pore filling material for said matrix comprising cork, in which cork is present in the form of particles, grains, granules or powder of different densities and / or granulometries, whose size distribution is less than that of open pores of said metal and porous and cellular metallic structure.

2. Metals and porous and cellular metallic structures of open porosity impregnated with cork, according to claim 1, characterized in that the metal is selected from aluminum, magnesium, manganese, copper, silicon, zinc, tin, nickel and their alloys.

3. Porous and cellular open porosity metallic and metallic structures impregnated with cork, according to any of the previous claims, characterized in that the filling material comprises cork from recycled cork or from cork waste from industrial processes.

4. Metals and porous and cellular metallic structures of open porosity impregnated with cork, according to any of the previous claims, characterized because the open metal foams are pore size between 1 ppi to 500 ppi, more preferably from 10 ppi to 250 ppi, even more preferably from 50 ppi to 150 ppi, or even from 75 ppi to 100 ppi.

5. Metals and porous and cellular metallic structures of open porosity impregnated with cork, according to any of the previous claims, characterized in that the filler material comprises at least one reinforcement element selected from ceramics, metals, polymers, glass, carbon-based materials, similar in the form of particles, fibers, tubular structures or sheets, similar and their combinations.

6. Metals and porous and cellular metallic structures of open porosity impregnated with cork, according to any of the previous claims, characterized in that the polymeric filler material is polyurethane or epoxide.

7. Metals and porous and cellular metallic structures of open porosity impregnated with cork, according to any of the previous claims, characterized in that the filler material contains 0 -50% by weight of reinforcement elements, of micrometric size or 0-10 % by mass of reinforcement elements, of nanometric size.

8. Metals and porous and cellular metallic structures of open porosity impregnated with cork, according to any of the previous claims, characterized in that the filler material comprises processing additives, preferably of the crosslinking type.

9. Process of production of porous metals and metallic structures of open porosity impregnated with cork, as described in claims 1 to 8, characterized by comprising the following steps: a) Preparation of cork-based filling material, by mixing the selected raw materials, in particular the cork material with the polymer and optionally with incorporation of at least one reinforcement element; b) Filling the open pores of a metal or a cellular or porous structure with the filling material of (a), by pouring that material into the open pores of the metal matrix of at least one metal or metal alloy; and c) Densification and curing of the material of (b).

Process according to claim 9, characterized in that in step (a) the incorporation of the reinforcement element is carried out by dry and / or wet techniques, in mechanical stirrers, by colloidal processing and step by step technique .

Process according to claim 9 or 10, characterized in that in step (b), the pore filling is carried out under vibration and / or pressure.

Process according to claim 9, 10 or 11, characterized in that in step (b), hollow-wall molds or structures of simple and / or complex geometries are used.

13. Process according to the preceding claim, characterized in that in step (b) the molds or hollow structures of thin walls of simple and complex geometries have a coating with non-stick properties.

14. Process according to the preceding claim, characterized in that the coating with properties nonstick be tracing paper, teflon sheets, kraft paper and / or paper and silicone-based films.

Process according to claim 9, 10, 11, 12, 13 or 14, characterized in that step (c) is carried out in air or in a vacuum, without applying temperature or, also, with the possibility of varying the temperature, typically up to 250 ° C.

16. Use of open porous and cellular metals and metal structures impregnated with cork, as described in claims 1 to 8, characterized in that they are applied in the open porosity and cellular metal and metal structures industry, namely, in metal foams and metal sponges.

17. Use of open porous and cellular metals and metallic structures impregnated with cork, as described in claims 1 to 8, characterized by being applied in the construction of houses, cars, trains, boats, airplanes, tools, machines, devices, furniture, design piece, for sound insulation, sound absorption, light construction, with improved thermal behavior, energy to impact and shock.

18. Use of open porous and cellular metals and metallic structures impregnated with cork, as described in claims 1 to 8, characterized by being applied as a core or filling for sandwich panels or hollow thin-walled tubular structures for impact energy absorption and for ballistic protection systems for vehicles, houses and personal protective equipment such as vests.