Composite material for shielding electromagnetic radiation, raw material for additive manufacturing methods and a product comprising the composite material, as well as a method of manufacturing the product

Abstract

The invention relates to a composite material for shielding electromagnetic radiation, a raw material for additive manufacturing methods and a product comprising the material as well as a method of manufacturing the product. The composite material according to the invention can serve as a material protecting electronic elements, electronic devices or living organisms from electromagnetic radiation in the microwave and terahertz range (0.3-10000 GHz).

Claims

1. A composite material for shielding electromagnetic radiation, comprising: 88-99.88 wt % of a thermoplastic, electrically non-conductive polymer, 0.1-10 wt % of a nanocarbon material in form of flakes having a diameter to thickness ratio higher than 3, the thickness of the flakes not exceeding 30 nm and the diameter being of 100 to 5000 nm, wherein the nanocarbon material is selected from the group consisting of flake graphene, graphene oxide, reduced graphene oxide, modified flake graphene, nanographite, and combinations thereof, 0.01-1 wt % of nanoparticles introducing a loss unrelated to electrical conductivity, wherein the nanoparticles are selected from the group consisting of nanoparticles of silicon carbide (SiC), nanoparticles of Fe—BN, ferrite-based nanoparticles, and combinations thereof, 0.01-1 wt % of an auxiliary material which allows control of a dispersion of the nanocarbon material and the nanoparticles in a polymer matrix and/or which can change the properties of the nanocarbon material and the nanoparticles, wherein the composite material is in form of a homogeneous mixture.

2. The composite material according to claim 1, wherein the thermoplastic polymer is selected from the group consisting of polystyrene (PS), polyethylene (PE), polypropylene (PP), polyurethane (PU), terpolymer of acrylonitrile-butadiene-styrene (ABS), polyester, a derivative of one of said polymers, and combinations thereof.

3. The composite material according to claim 1, wherein the auxiliary material is a graphene-functionalizing compound.

4. The composite material according to claim 3, wherein the graphene-functionalizing compound is a plasticizer, and the plasticizer is selected from the group consisting of an organic oil, an alcohol, an anhydride, and combinations thereof.

5. The composite material according to claim 3, wherein the graphene-functionalizing compound includes an antioxidant, wherein the antioxidant is a natural antioxidant.

6. A raw material for additive methods of manufacturing elements for shielding electromagnetic radiation, comprising the composite material defined in claim 1.

7. A product for shielding electromagnetic radiation, comprising the composite material defined in claim 1.

8. The composite material according to claim 1, wherein the thermoplastic polymer is selected from the group consisting of poly(ethylene terephthalate) (PET), poly(tetrafluoroethylene) (PTFE), polyamide (PA), terpolymer of acrylonitrile-styrene-acrylic (ASA), poly(vinyl chloride) (PVC), modified poly(phenylene ether) (MPPE), and combinations thereof.

9. The composite material according to claim 1, wherein the nanoparticles are ferrite-based nanoparticles, the ferrite-based nanoparticles have a hexagonal structure, and the ferrite-based nanoparticles contain at least one of cobalt, barium, and strontium.

10. The composite material according to claim 9, wherein the ferrite-based nanoparticles are selected from the group consisting of CoFe.sub.2O.sub.4, BaFe.sub.12O.sub.19, SrFe.sub.12O.sub.19, Ba.sub.3Me.sub.2Fe.sub.24O.sub.41, Ba.sub.3Sr.sub.2Fe.sub.24O.sub.41, Ba.sub.2Co.sub.2Fe.sub.12O.sub.22, BaCo.sub.2Fe.sub.16O.sub.27, Ba.sub.2Co.sub.2Fe.sub.28O.sub.46, Ba.sub.4Co.sub.2Fe.sub.36O.sub.60, and combinations thereof.

11. The composite material according to claim 3, wherein the graphene-functionalizing compound is selected from the group consisting of a plasticizer, an antioxidant, a hardener, and combinations thereof.

12. The composite material according to claim 5, wherein the natural antioxidant is selected from the group consisting of a carotenoid, a flavonoid, vitamin C, vitamin E, phenols, and combinations thereof.

13. The raw material according to claim 6, wherein the composite material is in the form of a granulate, a filament or a tape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The object of the invention is presented in more detail in embodiments in the drawing, in which:

(2) FIG. 1 shows measurement results in the transmission mode of the shielding efficiency of the composites from Example 1 in the range of 0.1-12.5 GHz (results on a logarithmic scale; the sign “-” in the graph means the weakening of the EM wave after passing through the material);

(3) FIG. 2a shows the degree of weakening (logarithmic scale) of electromagnetic radiation in the range of 0.1-0.95 THz of the material from Example 2;

(4) FIG. 2b shows the transmission level (logarithmic scale) of electromagnetic radiation in the range of 0.1-1.8 GHz of the material from Example 2;

(5) FIG. 3 shows the current-voltage characteristics for the distance of electrodes equal to 1 mm of the materials from Example 3.

DETAILED DESCRIPTION

Example 1

(6) Two samples were made. In both samples, a thermoplastic polymer, polyethylene (PE) was used as a polymer material, and a flake graphene (2 wt %) was used as a filler. The first sample contained also maleic anhydride (1 wt %) and a negligible amount of nanoparticles based on BaFe.sub.12O.sub.19 ferrites 0.05 wt %), while the other one—maleic anhydride (a negligible amount, i.e. <0.05 wt %) and 0.5 wt % of nanoparticles based on ferrites (BaFe.sub.12O.sub.19). The materials were prepared using injection technology. Initially, a mixture of the above-mentioned components was prepared and they were mixed together mechanically, and then mixed again using a hot extruder (at a temperature above 220° C.) and thin plates having a thickness of 0.8-1 mm were formed using hot extrusion technique.

(7) In the transmission mode, shielding efficiencies of the composites in the range of 0.1-12.5 GHz were measured (results on a logarithmic scale; the sign “-” in the graph means the weakening of the EM wave after passing through the material). Both materials had an efficiency exceeding 10 dB at least in part of the above-mentioned range.

(8) The above example illustrates the shielding properties of the materials according to the invention for EM radiation in the microwave range.

Example 2

(9) A thermoplastic polymer from the group of polyesters-polyethylene terephthalate (PET) was used a polymer material, and a flake graphene (2 wt %) and minimum amounts of SrFei.sub.2O.sub.19 nanoparticles (<0.1 wt %) and maleic anhydride (<0.1 wt %) were used as a filler, and the material was prepared by injection technology. Graphene was added to the polymer when it was in a liquid state (i.e. above 265° C.) and hot mixed using an extruder and hot extrusion technique. The material was then hot pressed into a mould, the filling of which yielded a thin plate having a thickness of about 1.8 mm, and then cooled.

(10) Degree of weakening (logarithmic scale) of electromagnetic radiation in the range of 0.1-0.95 THz (FIG. 2a) was measured. Negative values of transmission were indicative of how much radiation in decibels is weakened after passing through the material. The technology of time-resolved terahertz spectroscopy was used for the tests.

(11) Transmission level (logarithmic scale) of electromagnetic radiation in the range of 0.1-1.8 GHz was also measured (FIG. 2b), demonstrating that in this range the material is permeable to the above-mentioned range and thus demonstrating selectivity of shielding efficiency in various ranges.

(12) Furthermore, the tested material did not conduct direct current (DC) and its resistivity exceeded 36.10.sup.6 Ω.Math.cm.

(13) The above example illustrates the ability of the materials according to the invention to shield EM radiation in the THz range and selectivity of shielding efficiency.

Example 3

(14) A composite comprising polyethylene (PE), a filler in form of flake graphene (2 wt %), maleic anhydride (1 wt %) and a negligible amount (<0.1 wt %) of BaFe.sub.12O.sub.19 dielectric nanoparticles was obtained analogously to Example 1, producing samples in form of 1 mm thick plates. In a similar manner, samples of a comparative composite made of polyethylene and flake graphene (2 wt %) and negligible amounts of anhydride and nanoparticles (<0.05% by weight) were obtained. Electrical conductivity of both composites in various ranges was measured. In the DC range, the current-voltage characteristics for the distance of electrodes equal to 1 mm (curves in FIG. 3) was examined, from which the resistance value of a given material can be determined. In the microwave range, the resistivity per square was directly examined using a microwave resonator operating at a frequency of 5 GHz. Data from both methods are summarised in the table under the curves in the graph in FIG. 3. The data collected in this table show that the comparative composite containing PE and graphene is conductive only in the microwave range, while the composite according to the invention containing PE, graphene, maleic anhydride (and BaFe.sub.12O.sub.19 nanoparticles) is conductive over the entire measured range.

(15) The above example illustrates that depending on the composition, the composite is conductive or non-conductive at different frequency ranges.

Example 4

(16) A composite comprising polyethylene (PE), a filler in form of flake graphene (2 wt %) having two different diameters (5 μm and 25 μm), maleic anhydride (1 wt %) and a negligible amount (<0.1 wt %) of BaFe.sub.12O.sub.19 nanoparticles was obtained analogously to Example 1. Plates having a thickness below 1 millimetre were made from the composites, and their resistivity in various ranges was examined, as illustrated in the following table 1.

(17) TABLE-US-00001 TABLE 1 Resistivity values for composite samples from Example 4 Alternating Current Composite Direct Current (5 GHz) With graphene flakes having ~10 MOhm 200 Ohm/sq a diameter of 5 μm With graphene flakes having non-conductive 700 Ohm/sq a diameter of 25 μm (unmeasurable)

(18) Only the composite including flake graphene with a flake size of 5 μm is conductive in the direct current (DC) range. In turn, in the microwave (5 GHz) range, both materials are conductive.

(19) The above example illustrates the effect of the size of graphene flakes on whether the composite material according to the invention is conductive or non-conductive at different frequency ranges.