ELECTROMAGNETIC WAVE TRANSMISSION REDUCING MATERIAL

Abstract

The present invention relates to an electromagnetic millimetre wave transmission reducing material, preferably having a volume resistivity of more than 1 Ωcm, containing particles of at least an electrically conductive, magnetic or dielectric material and an electrically non-conductive polymer, wherein the transmission reducing material is capable of reducing transmission of electromagnetic waves in a frequency region of 60 GHz or more. The invention also relates to its use and method for reducing transmission as well as an electronic device comprising said transmission reducing material.

Claims

1. An electromagnetic millimetre wave transmission reducing material containing particles of at least an electrically conductive, magnetic, or dielectric material and an electrically non-conductive polymer, wherein the transmission reducing material is capable of reducing transmission of electromagnetic waves in a frequency region of 60 GHz or more.

2. The transmission reducing material of claim 1, wherein the material contains solid particles at least a first electrically conductive material.

3. The transmission reducing material of claim 1, wherein the particles of the at least first electrically conductive material are non-fibrous particles having a spherical or lamellar shape.

4. The transmission reducing material of claim 1, wherein the electrically non-conductive polymer is a thermoplast, thermoplastic elastomer, thermoset, or a vitrimer.

5. The transmission reducing material of claim 1, wherein the transmission reducing material is subject to injection molding, thermoforming, compression molding, or 3D printing.

6. The transmission reducing material of claim 1, wherein the amount of the particles of the electrically conductive, magnetic or dielectric material is from 0.1 wt.-% to 80 wt. % based on the total amount of the transmission reducing material.

7. The transmission reducing material of claim 1, wherein the at least first electrically conductive material is carbon or a metal or a metal oxide.

8. The transmission reducing material of claim 7, wherein the metal is zinc, nickel, copper, tin, cobalt, manganese, iron, magnesium, lead, chromium, bismuth, silver, gold, aluminum, titanium, palladium, platinum, tantalum, or an alloy thereof.

9. The transmission reducing material of claim 1, wherein the electrically conductive, magnetic, or dielectric material is selected from the group consisting of carbonyl iron powder, MnFePSi alloy, zinc oxide, barium titanate, and copper.

10. The transmission reducing material of claim 1, wherein at least one of the following prerequisites is fulfilled: the particles of the at least first electrically conductive material have a length of from 0.001 to 1 mm; the particles of the at least first electrically conductive material have a diameter of from 0.1 μm to 100 μm.

11. The transmission reducing material of claim 1, wherein the transmission reducing material additionally contains one or more additives.

12. An electronic device containing a radar absorber in form of a radar absorber part or a radar absorbing housing, the radar absorber comprising at least a transmission reducing material of claim 1, wherein the at least one transmission reducing material is comprised in the electronic device in the radar absorber; at least one transmission area, transmissible for electromagnetic millimeter waves in a frequency region of 60 GHz or more; and a sensor capable of detecting and optionally emitting electromagnetic millimeter waves in a frequency region of 60 GHz or more through the transmission area.

13. (canceled)

14. A method of reducing transmission of electromagnetic millimeter waves in a frequency region of 60 GHz or more, the method comprising irradiating a transmission reducing material of claim 1 with electromagnetic millimeter waves in a frequency region of 60 GHz or more.

15. A transmission reducing material of claim 1, wherein the frequency region is from 60 GHz to 90 GHz.

16. The transmission reducing material of claim 1 having a volume resistivity of more than 1 Ωcm.

17. The transmission reducing material of claim 2, wherein the particles have an aspect ratio (length:diameter) of less than or equal to 10.

Description

EXAMPLES

[0157] Materials

[0158] Poly(butylene terephthalate) (PBT, Ultradur B1950), carbonyl iron powder (CIP) and the alloy MnFePSi 1 were all obtained from BASF SE, this later was prepared according to the method described in WO2011/083446 A1. This sample has a transition temperature of T.sub.c=38.7° C. The zinc oxide (ZnO) was obtained from China Hishine Industry Co. Ltd. and Silvet 430-30 was obtained from Silverline. Barium titanate (BaTiO.sub.4) and copper powder were obtained from Sigma-Aldrich.

Measurement of the Interaction with Electromagnetic Waves

[0159] The experimental setup for the characterization of the transmission reducing material in the range 60-90 GHz is as follows.

[0160] A vectoral network analyzer Keysight N5222A (10 MHz-26.5 GHz), two Keysight T/R mm head modules N5256AW12, 60-90 GHz and as a sample holder a swissto12 corrugated waveguide WR12+, 55-90 GHz. The calibration of the corrugated waveguide (cw) is done by doing a thru and short measurement. For the thru measurements the flanges of the cw are connected, for the short measurement, a metal plate is inserted between the flanges. The field distribution of the cw is described in: IEEE Transactions on Microwave Theory and Techniques 58, 11 (2010), 2772.

[0161] After the calibration, the sample (minimum diameter 2 cm) is inserted between the flanges of the cw and the S11 (reflection) and S21 (transmission) parameters are measured in the range 60-90 GHz (amplitude and phase). From the measured S11 and S22 parameters, the absorption A of the sample was calculated as follows: A (%)=100−S11(%)−S21(%).

[0162] From the measured parameters, the dielectric parameters £′ (dielectric permittivity) and E″ (dielectric loss factor) of the sample material is calculated at each frequency point using the swissto12 materials measurement software.

Preparation of the Example S1

[0163] Poly(butylene terephthalate) (PBT, Ultradur B1950) was obtained from BASF SE and was mixed with 10 wt % of zinc oxide (ZnO, China Hishine Industry Co. Ltd.) and the materials were subsequently dried at 100° C. under vacuum. This yielded a dry mixture with a water content below 0.04 wt %, required for processing of PBT. After the drying, the materials were loaded into a DSM mini-extruder and melted and mixed at 260° C. for 3 minutes. After these three minutes of mixing, the molten material was loaded in the cartridge for injection molding. This cartridge was pre-heated to 260° C. The samples were injection molded at 260° C. using 4-10 bar pressure, with a molding time of 2-5 seconds. This process yielded plates with a size of 30×30×1.4 mm (b×l×t), which were subsequently analyzed.

[0164] The composition of the examples containing various additives (S1-S19) and the comparative example (C1) have been listed in Table 1. Results can be found in Table 2.

TABLE-US-00002 TABLE 1 Compositions of the examples S1- S19 and comparative example C1. Silvet Copper Barium B1950 ZnO ClP 430-30 powder titanate MnFePSi Sam- (wt (wt (wt (wt (wt (wt (wt ple %) %) %) %) %) %) %) C1 100 S1 80 20 S2 60 40 S3 50 50 S4 40 60 S5 70 30 S6 50 50 S7 30 70 S8 20 80 S9 70 30 S10 50 50 S11 30 70 S12 70 30 S13 50 50 S14 30 70 S15 70 30 S16 50 50 S17 30 70 S18 70 30 S19 50 50

TABLE-US-00003 TABLE 2 Results of analysis examples S1-S19 and comparative example C1 Transmission Transmission Reflection Absorption Sample (%) reduction*) (%) (%) (%) C1 84 0 12.0 4.0 S1 59.6 29 20.0 20.4 S2 43.4 48 22.7 33.9 S3 36.5 57 25.3 38.2 S4 23.0 73 22.8 54.2 S5 56.7 33 34.0 9.3 S6 47.0 44 39.7 13.3 S7 36.0 57 18.1 46.9 S8 9.5 89 37.1 53.4 S9 19.4 77 53.7 26.9 S10 8.2 90 32.8 59.0 S11 1.8 98 58.7 39.5 S12 59.4 29 34.9 5.7 S13 37.6 55 53.3 9.1 S14 36.9 56 31.4 31.7 S15 52.2 38 40.7 7.1 S16 66.7 21 10.7 22.6 S17 21.8 74 58.3 19.9 S18 52.5 38 28.6 18.9 S19 19.6 77 18.9 19.6 *)(84% − T):84%