Polypropylene composition with enhanced microwave absorption and reduced microwave reflection

Abstract

The composition includes a thermoplastic resin comprising a polypropylene polymer and about 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes. The carbon nanotubes have an average diameter of about 5 to 15 nanometers (nm) and a density of at least about 100 square meters per gram (m 2 / gr) surface area, and 10 -3 The composition has a volume resistivity of 0.01E+1.0 Ohm.cm or less. The composition exhibits a volume electrical resistivity of 2.0E+14 Ohm.cm to 1.0E+03 Ohm.cm, and molded samples of the composition exhibit a percent power absorption of at least 65% measured in transmission mode at frequencies of about 75 GHz to about 110 GHz. Molded articles containing micron-sized features that provide the article with high absorption and low reflection properties are also described.

Description

[Technical Field]

[0001] The present disclosure relates to thermoplastic compositions having good microwave absorption properties, particularly compositions comprising polypropylene polymer and carbon nanotubes. [Background technology]

[0002] According to the Association for Safe International Road Travel (ASIRT), more than one million people die in road accidents each year, and tens of millions are injured or disabled. Road traffic accidents rank as the leading cause of death, costing more than US$500 billion worldwide and accounting for a significant portion of each country's annual GDP. Unless action is taken, road traffic accidents are predicted to become the fifth leading cause of death by 2030 (Association for Safe International Road Travel-ASIRT, 2016). For these reasons, the automotive industry is increasingly leveraging advanced driver assistance systems (ADAS) to provide driver assistance with features such as adaptive cruise control, self-parking, back-up warning, blind-spot detection, lane departure warning, collision avoidance, and pedestrian detection.

[0003] Due to their decreasing cost and increasing availability, radar sensors are commonplace in today's automotive safety systems and are used in cutting-edge ADAS systems. These automotive radar systems can be divided into three subcategories depending on the range or distance at which they operate: short-range, medium-range, and long-range automotive radars. Each of these sensors has a different application. Long-range radars (ranges greater than 100 meters or so) are typically used for forward collision avoidance and adaptive cruise control and operate primarily in the W-band of the electromagnetic spectrum, at frequencies between approximately 75 and 110 GHz. Meanwhile, short- and medium-range radars (ranges of tens of meters) are used for blind spot detection, parking assistance systems, pre-collision warnings, or lane departure warnings and operate primarily in the K-band, at frequencies between approximately 18 and 26.5 GHz. The K-band frequency range is expected to see less use in automotive radar sensors for ADAS applications due to the strict regulations currently being implemented regarding output at lower frequencies (Source: Burger, R., Salinero, T., Sumida, S., “Beyond The Headlights: ADAS and Autonomous Sensing”; Market Report, Woodside Capital Partners; September 2016).

[0004] For radar sensors to operate effectively, they must be protected from spurious sources of electromagnetic radiation. Metals are inherently reflectors and therefore poor absorbers of microwave radiation, proving their value limited when used in applications requiring high levels of microwave absorption and low levels of microwave reflection. Polymer / carbon composites, on the other hand, are preferred over metals not only for their much higher microwave absorption properties but also for their lower density and cost, ease of molding, and easier manufacturability into large-volume molded parts. Carbon fillers generally capture or deflect microwave (MW) radiation impinging on the enclosure walls, thus protecting the electronic sensors within the cavity. Reasonably high permittivity and electrical conductivity, as well as large dielectric and magnetic losses, are some of the characteristics required for materials used in microwave shielding. In certain applications, carbon nanotubes are preferred over carbon powder, graphite, or carbon fiber because they offer adequate microwave interference performance at relatively low loadings. For example, low carbon loadings will improve the ductility, impact strength, surface aesthetics, and flow of these materials under high shear rate conditions. The amount of carbon filler used in these compositions typically depends on the type of carbon used, with carbon fibers and carbon nanotubes requiring low loadings to achieve relatively high levels of microwave absorption. On the other hand, low-structure (large particle size, small specific surface area) carbon black powders require higher loadings when used in resins designed to achieve the same microwave absorption performance. Regardless of the type of filler used in these formulations, too little carbon will result in high transmission and low absorption and reflection, while too much carbon will result in low transmission and high reflection. Therefore, selecting the appropriate combination of carbon filler type and loading can be important when designing a material that is a good microwave absorber but a poor microwave reflector when used in radar sensors at relatively high operating frequencies.

[0005] Microwave radiation (frequencies between approximately 1 and 300 GHz, wavelengths between approximately 300 and 1 mm) is the most common electromagnetic energy source used to operate radar sensors in automotive applications. Metals (e.g., aluminum, stainless steel), polymer composites containing metal fillers such as aluminum flakes, stainless steel fibers, or silver-coated polyamide fibers, metallized coatings, intrinsically conductive polymers such as polyacetylene, polypyrrole, polythiophene, and polyaniline, silicon carbide, ferrite (Fe2O3 with Ni / Zn / Cd / Co secondary oxides), iron silicide, and iron pentacarbonyl are some of the materials used in ADAS applications to protect automotive safety sensors from damaging microwave electromagnetic radiation. While metals are the most common material for MW interference shielding, they are heavy, expensive, and require complex processing to be formed into final parts. Polymer / carbon composites, on the other hand, are preferred due to their low density, low cost, ease of molding, and manufacturability into high-volume molded parts.

[0006] Carbon (powder, platelets, fibers, nanotubes, etc.) has emerged as a popular filler for imparting electromagnetic interference properties to thermoplastic polymers, which are largely transparent (non-absorbing, non-reflective) to microwave radiation when unfilled. For example, when used in interior automotive enclosures, polymer-carbon thermoplastic composites can protect sensors located within the enclosure, thus preventing electromagnetic radiation from external sources from degrading the sensor's electronic performance. Carbon-containing elastomers, such as silicone, polyurethane, and nitrile rubber, can also be used as high-loss, protective, and deformable sheets or blankets to dampen resonant frequencies generated by the normal operation of sensors within a cavity. Besides thermoplastics and elastomers, these radar-shielding materials are also commercially available in the form of liquid paints, powder coatings, and closed-pore polymer foams. Electrical conductivity, dielectric and magnetic losses, the frequency of incoming radiation, and the thickness of the enclosure wall are some of the characteristics expected to affect the microwave interference performance of these materials.

[0007] The choice of microwave shielding material used in a given situation depends in part on the environment surrounding the electronic component being protected (such as an antenna, a printed circuit board, or an imaging device for medical applications). If the incoming radiation to be suppressed or minimized originates outside the component being protected, a material with reflective microwave properties, such as a metal plate (aluminum, stainless steel, etc.) or a polymer composite containing a metal filler (such as those from SABIC's Faradex™ product line), may be all that's needed. In this case, the enclosure protects the electronic component by reflecting the incoming radiation away from the cavity. On the other hand, if the incoming radiation originates within the cavity being protected, it may be necessary to select a material that absorbs microwave energy to isolate the sensor component from standing electromagnetic waves (vibrations) caused by cavity resonance. Microwave absorbers can be used to line the inner walls of the test anechoic chamber, thus eliminating unwanted reflections that would otherwise adversely affect the dielectric response of the material being tested within the chamber.

[0008] There are several dielectric properties that radar designers consider when selecting materials for microwave radar interference. Complex permittivity (real and imaginary parts), the amount of radiation absorbed, reflected, or transmitted by the material, shielding effectiveness, reflection loss, and attenuation are just some of the material properties of interest for the manufacture of plastic components for radar sensor applications. As noted, the frequency of the incoming radiation and the thickness of the material are also important when capturing microwave energy that, if not eliminated or minimized, could potentially interfere with the normal operation of automotive electronic sensors.

[0009] Automotive radar sensors include radome-type plastic components that are nearly transparent to microwave radiation, and absorber-type plastic components that capture microwave energy in a certain frequency range and protect the sensor from external radiation interference. These plastic components are typically formed into final parts using relatively high injection pressures and melt temperatures to produce molded articles that are smooth in appearance and featureless. Microwave-absorbing materials made from carbon as a microwave-absorbing filler and molded into smooth-surfaced parts can only provide certain levels of (high) microwave absorption and (low) microwave reflection, which may make these materials of limited value when used in automotive radar sensors that require relatively high levels of absorption and low levels of reflection when operating in the W-band of the electromagnetic spectrum.

[0010] These and other shortcomings are addressed by aspects of the disclosure. Summary of the Invention

[0011] An embodiment of the present disclosure relates to a composition comprising a thermoplastic resin, the thermoplastic resin comprising a polypropylene polymer and about 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes. The carbon nanotubes have an average diameter of about 5 to 15 nanometers (nm) and a density of at least about 100 square meters per gram (m 2 / gr) surface area, and 10 -3 The composition has a volume resistivity of 2.0E+14 Ohm.cm to 1.0E+03 Ohm.cm when measured in accordance with ASTM D257. Molded samples of the composition having a thickness of about 3.1 millimeters (mm) to about 3.3 mm exhibit a percent power absorption of at least 65% measured in transmission mode when observed in accordance with the free-space method at frequencies of about 75 GHz to about 110 GHz. The combined weight percentages of all components do not exceed 100% by weight, and all weight percentages are based on the total weight of the composition.

[0012] A further aspect of the present disclosure relates to an article comprising a shaped plaque comprising a surface having micron-sized features, the shaped plaque having a thickness of about 2.7 mm to about 2.9 mm, and the region of the shaped plaque comprising the micron-sized features exhibits a percent absorbed power measured in transmission mode of at least 85% and a percent reflected power measured in transmission mode of 2% or less when observed according to the free-space method at frequencies between about 75 GHz and 110 GHz, the micron-sized features having a height-to-base ratio of 2:1 to 10:1. [Brief explanation of the drawings]

[0013] In the drawings, which are not necessarily drawn to scale, like numerals may refer to like components in different views. Like numerals with different letter suffixes may represent different instances of like components. The drawings illustrate generally, by way of example, but not by way of limitation, various aspects discussed in the present document.

[0014] [Figure 1A] 1 is a graph demonstrating notched and unnotched Izod impact properties at 23° C. and −30° C., respectively, for comparative and example compositions according to aspects of the present disclosure. [Figure 1B] 1 is a graph demonstrating notched and unnotched Izod impact properties at 23° C. and −30° C., respectively, for comparative and example compositions according to aspects of the present disclosure. [Figure 2] 1 is a graph showing surface and volume electrical resistivity for comparative and example compositions according to aspects of the present disclosure. [Figure 3] 1 is a graph showing melt flow rates (MFR) for comparative and example compositions according to aspects of the present disclosure. [Figure 4A] 1A-1C are schematic diagrams of the apparatus used to determine the dielectric properties of materials of the present disclosure using the free-space method for unbacked and metal-backed samples, respectively. [Figure 4B]1A-1C are schematic diagrams of the apparatus used to determine the dielectric properties of materials of the present disclosure using the free-space method for unbacked and metal-backed samples, respectively. [Figure 5] 1 is a graph showing percent power (reflected, absorbed, and transmitted) in transmission mode at 77 GHz for comparative and example compositions according to embodiments of the present disclosure. [Figure 6A] 1 is a graph illustrating the real part of the complex dielectric permittivity, the imaginary part of the complex dielectric permittivity, and the attenuation constant for comparative and example compositions, respectively, according to aspects of the present disclosure. [Figure 6B] 1 is a graph illustrating the real part of the complex dielectric permittivity, the imaginary part of the complex dielectric permittivity, and the attenuation constant for comparative and example compositions, respectively, according to aspects of the present disclosure. [Figure 6C] 1 is a graph illustrating the real part of the complex dielectric permittivity, the imaginary part of the complex dielectric permittivity, and the attenuation constant for comparative and example compositions, respectively, according to aspects of the present disclosure. [Figure 7] 1 is a graph showing the total shielding effectiveness for comparative and example compositions according to aspects of the present disclosure. [Figure 8] 1 is a graph illustrating percent power absorbed in transmission mode for comparative and example compositions according to aspects of the present disclosure. [Figure 9] 1 is a graph showing percent power absorbed in metal-backed reflective mode for comparative and example compositions according to aspects of the present disclosure. [Figure 10] 1 is a graph showing the percent power (absorbed, reflected, and transmitted) in transmission mode for composition Ex1.3. [Figure 11] 1 is a graph showing percent power (reflected, absorbed, and transmitted) in transmission mode at 77 GHz for example compositions according to aspects of the present disclosure. [Figure 12A] 1 is a graph showing the real part of the complex permittivity, the imaginary part of the complex permittivity, and the attenuation constant for example compositions according to aspects of the present disclosure at frequencies from 75 to 110 GHz. [Figure 12B] 1 is a graph showing the real part of the complex permittivity, the imaginary part of the complex permittivity, and the attenuation constant for example compositions according to aspects of the present disclosure at frequencies from 75 to 110 GHz. [Figure 12C] 1 is a graph showing the real part of the complex permittivity, the imaginary part of the complex permittivity, and the attenuation constant for example compositions according to aspects of the present disclosure at frequencies from 75 to 110 GHz. [Figure 13] 1 is a graph showing the total shielding effectiveness for example compositions according to embodiments of the present disclosure at frequencies between 75 and 110 GHz. [Figure 14] 1 is a graph showing the percent power absorbed in transmission mode for example compositions according to embodiments of the present disclosure at frequencies between 75 and 110 GHz. [Figure 15A] 10A and 10B are graphs showing the percent power (absorbed, reflected, and transmitted) in transmission mode and the percent power in metal-backed reflection mode, respectively, of composition Ex2.3 observed on a 3.1 mm thick sample at frequencies from 75 to 110 GHz. [Figure 15B] 10A and 10B are graphs showing the percent power (absorbed, reflected, and transmitted) in transmission mode and the percent power in metal-backed reflection mode, respectively, of composition Ex2.3 observed on a 3.1 mm thick sample at frequencies from 75 to 110 GHz. [Figure 16A] 2D front and side perspective sketches of geometric features according to an embodiment of the present disclosure. [Figure 16B] 2D front and side perspective sketches of geometric features according to an embodiment of the present disclosure. [Figure 17A] 1A-1C are microscope images showing a top view and a cross-sectional view, respectively, of a 2D triangular wedge imprinted or molded into the surface of a smooth molded part, according to an embodiment of the present disclosure. [Figure 17B]1A-1C are microscope images showing a top view and a cross-sectional view, respectively, of a 2D triangular wedge imprinted or molded into the surface of a smooth molded part, according to an embodiment of the present disclosure. [Figure 18A] 1 is an image of an exemplary three-dimensional (3D) imprinted or molded feature according to an embodiment of the present disclosure. [Figure 18B] 1 is an image of an exemplary three-dimensional (3D) imprinted or molded feature according to an embodiment of the present disclosure. [Figure 18C] 1 is an image of an exemplary three-dimensional (3D) imprinted or molded feature according to an embodiment of the present disclosure. [Figure 19A] 1A-1C are schematic diagrams of an apparatus for testing imprinted plaques in transmission mode and metal-backed reflection mode, respectively. [Figure 19B] 1A-1C are schematic diagrams of an apparatus for testing imprinted plaques in transmission mode and metal-backed reflection mode, respectively. [Figure 20A] 1 is a graph showing the dielectric properties of imprinted composition Ex2.3 measured in transmission mode and metal-backed reflection mode at frequencies between 75 and 110 GHz, respectively. [Figure 20B] 1 is a graph showing the dielectric properties of imprinted composition Ex2.3 measured in transmission mode and metal-backed reflection mode at frequencies between 75 and 110 GHz, respectively. [Figure 21] 1 is a graph showing percent power in transmission mode for conventional carbon black compositions at 77 GHz. [Figure 22] 1 is a graph showing percent power in transmission mode at 77 GHz for examples and conventional compositions with and without marking. [Figure 23A] 1 illustrates an exemplary three-dimensional (3D) stamped or molded feature according to an embodiment of the present disclosure. [Figure 23B] 1 illustrates an exemplary three-dimensional (3D) stamped or molded feature according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] Before the present compounds, compositions, articles, systems, devices, and / or methods are disclosed and described, it is to be understood that they are not limited to particular synthetic methods, or to particular reagents, unless otherwise specified, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0016] Various combinations of elements of the present disclosure are encompassed by the present disclosure, such as combinations of elements from dependent claims that are dependent on the same independent claim.

[0017] Furthermore, it should be understood that unless expressly stated otherwise, the methodologies described herein are in no way intended to be construed as requiring that its steps be performed in a particular order. Thus, where a method claim does not actually recite the order its steps are to follow, or where the claim or description does not specifically state that the steps are limited to a particular order, no order is intended to be inferred in any respect. This applies to any possible implicit basis for interpretation, including matters of logic regarding the arrangement of steps or operational flow, the apparent meaning derived from grammatical construction or punctuation, and the number or type of aspects described herein.

[0018] All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the publications are cited.

[0019] definition It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to be limiting. As used in this specification and the claims, the term "comprising" can include aspects "consisting of" and "consisting essentially of." Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In this specification and the claims below, reference will be made to certain terms defined herein.

[0020] As used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "polypropylene polymer" includes a mixture of two or more polypropylene polymers.

[0021] As used herein, the term "combination" is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0022] Ranges may be expressed herein as from one value (the first value) to another value (the second value). When such a range is expressed, the range, in some embodiments, includes either or both of the first and second values. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it is understood that the particular value forms another embodiment. It is further understood that the endpoints of each of the ranges are significant in relation to the other endpoint, and independently of the other endpoint. It is understood that there are a number of values ​​disclosed herein, and that each value is also herein disclosed as "about" that particular value in addition to the value itself. For example, if the value "10" is disclosed, then "about 10" is also disclosed. It is also understood that each unit between two specified units is disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0023] As used herein, the terms "about" and "at" or "about" mean that the quantity or value in question can be the specified value, approximately the specified value, or approximately the same as the specified value. When used herein, it is generally understood to be a nominal value, indicating a ±10% variation, unless otherwise indicated or inferred. The term is intended to convey that similar values ​​promote the same results or effects as those recited in the claims. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics need not be exact but may be approximate and / or larger or smaller, as appropriate, to reflect tolerances, conversion factors, rounding, measurement errors, etc., and other factors known to those skilled in the art. In general, amounts, sizes, formulations, parameters, or other quantities or characteristics are "about" or "approximate," whether or not expressly stated as such. When "about" is used before a quantitative value, it is understood that the parameter also includes the specific quantitative value itself, unless otherwise stated.

[0024] Disclosed are the components used to prepare the disclosed compositions, as well as the compositions themselves used within the methods disclosed herein. When these and other materials are disclosed herein, and when combinations, subsets, interactions, groups, etc. of these materials are disclosed, it is understood that specific reference to the various individual and collective combinations and permutations of each of these compounds may not be explicitly disclosed, but each is specifically contemplated and described herein. For example, when a particular compound is disclosed and discussed, and several modifications that can be made to many molecules comprising that compound are discussed, what is specifically contemplated are any and all combinations and permutations of the compounds and possible modifications, unless specifically indicated to the contrary. Thus, when classes of molecules A, B, and C, and classes of molecules D, E, and F, and examples of combined molecules are disclosed, this means that A-D are disclosed, and then each is individually and collectively contemplated, even if each is not individually detailed, and combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are considered to be disclosed. Likewise, any subset or combination thereof is also disclosed. Thus, for example, the subgroups A-E, B-F, and C-E are considered disclosed. This concept applies to all aspects of this application, including, but not limited to, steps in methods of making and using the disclosed compositions. Thus, where there are various additional steps that may be performed, it is understood that each of these additional steps can be performed in any specific aspect or combination of aspects of the disclosed methods.

[0025] References in the specification and concluding claims to parts by weight of a particular element or component in a composition or article indicate the weight relationship between the element or component and any other element or component in the composition or article for which the parts by weight are expressed. Thus, in a compound containing 2 parts by weight of component X and 5 parts by weight of component Y, X and Y are present in a weight ratio of 2:5, and are present in such ratio regardless of whether additional components are contained in the compound.

[0026] As used herein, the terms "weight percent," "% by weight (wt%)," and "% by weight (wt.%)," which may be used interchangeably, refer to the weight percent of a given component relative to the total weight of the composition, unless otherwise specified. That is, all weight percent values ​​are based on the total weight of the composition, unless otherwise specified. It is understood that the sum of the weight percent values ​​of all components in a disclosed composition or formulation equals 100.

[0027] Unless stated to the contrary herein, all test specifications are the latest specifications in effect at the time of filing this application.

[0028] Each of the raw materials used in the examples and / or comparative compositions described herein is either commercially available and / or methods for its production are known to those of skill in the art.

[0029] It is understood that the compositions disclosed herein have specific functions. Disclosed herein are specific structural requirements for performing the disclosed functions, and it is understood that there are various structures that can perform the same function related to the disclosed structures, and that these structures typically achieve the same result.

[0030] thermoplastic composition An embodiment of the present disclosure relates to a composition or article comprising a thermoplastic resin, the thermoplastic resin comprising a polypropylene polymer and about 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes. The carbon nanotubes have an average diameter of about 5 to 15 nanometers (nm) and a density of at least about 100 square meters per gram (m 2 / gr) surface area, and 10 -3The composition has a volume resistivity of 2.0E+14 Ohm.cm to 1.0E+03 Ohm.cm when measured in accordance with ASTM D257. Molded samples of the composition having a thickness of about 3.1 millimeters (mm) to about 3.3 mm exhibit a percent power absorption of at least 65% measured in transmission mode when observed in accordance with the free-space method at frequencies of about 75 GHz to about 110 GHz. The combined weight percentages of all components do not exceed 100% by weight, and all weight percentages are based on the total weight of the composition.

[0031] As used herein, "polypropylene" may be used interchangeably with poly(propene). Polypropylene polymers may include polypropylene homopolymers, polypropylene copolymers, or combinations thereof. In some embodiments, the composition comprises about 40% to about 90% by weight of polypropylene polymer. In further embodiments, the composition comprises about 40% to about 85% by weight, or about 40% to about 80% by weight, or about 40% to about 75% by weight, or about 40% to about 70% by weight, or about 40% to about 65% by weight, or about 45% to about 90% by weight, or about 45% to about 85% by weight, or about 45% to about 80% by weight, or about 45% to about 75% by weight, or about 45% to about 70% by weight, or about 45% to about 65% by weight, or about 50% to about 90% by weight, or about 50% to about 85% by weight, or about 50% to about 80% by weight, or about 50% to about 75% by weight, or about 50% to about 70% by weight, or about 50% to about 65% by weight.

[0032] In some embodiments, the carbon nanotubes are included in the composition in the form of a polypropylene-based masterbatch. The polypropylene-based masterbatch, in certain embodiments, has a carbon nanotube content of about 15% to about 25% by weight. In further embodiments, the polypropylene-based masterbatch has a carbon nanotube content of about 18% to about 22% by weight, or about 19% to about 21% by weight, or about 20% by weight. In certain embodiments, the composition contains about 0.6% to about 2.75% by weight of carbon nanotubes. In certain embodiments, compositions containing this amount of carbon nanotubes have a percent power absorption of at least 80% measured in transmission mode when observed at a frequency of 77 GHz.

[0033] In some embodiments, the composition further comprises a reinforcing filler, which may include, but is not limited to, glass fiber, glass spheres, glass flakes, flaked silicon carbide, ceramic fiber, calcium carbonate, kaolin, mica, clay, talc, feldspar, fillite, quartz, quartzite, perlite, tripoly, diatomaceous earth, or combinations thereof.

[0034] In some embodiments, the compositions do not include conductive fillers, such as, but not limited to, metal fibers or carbon fibers, because they adversely affect the microwave absorption properties of the material. Reinforcing fillers, if included, may be selected so that they do not adversely affect the microwave (MW) interference properties (absorption, transmission, reflection) provided by the CNTs included in compositions according to embodiments of the present disclosure. For example, glass fibers are nearly transparent (minimal absorption and reflection) to MW radiation. In certain embodiments, the reinforcing filler includes glass fibers.

[0035] In certain embodiments, the composition comprises from about 5% to about 50% by weight of the reinforcing filler. In further embodiments, the reinforcing filler is present in an amount of from 5% to about 45% by weight, or from 5% to about 40% by weight, or from 5% to about 35% by weight, or from 5% to about 30% by weight, or from 5% to about 25% by weight, or from 10% to about 50% by weight, or from 10% to about 45% by weight, or from 10% to about 40% by weight, or from 10% to about 30% by weight, or from 10% to about 25% by weight, or from 15% to about 50% by weight, or from 15% to about 45% by weight, or from 15% to about 40% by weight, or from 15% to about 35% by weight, or from 15% to about 30% by weight, or from 15% to about 25% by weight, or about 20% by weight.

[0036] In some embodiments, the composition further comprises a polycarbonate polymer. The polycarbonate polymer can comprise a polycarbonate homopolymer, a polycarbonate copolymer, or a combination thereof. In certain embodiments, the polycarbonate polymer comprises a polycarbonate-siloxane copolymer having a siloxane content of about 5% to about 45% by weight. In further embodiments, the polycarbonate-siloxane copolymer has a siloxane content of about 4-8% by weight (e.g., a transparent EXL available from SABIC having a siloxane content of about 6% by weight), about 18-22% by weight (e.g., an opaque EXL available from SABIC having a siloxane content of about 20% by weight), and / or about 35-45% by weight (e.g., a 40% by weight siloxane copolymer available from SABIC). Compositions including polycarbonate-siloxane copolymers according to embodiments of the present disclosure may have a total siloxane content of from about 2% to about 10% by weight.

[0037] In certain embodiments, the composition comprises from about 5% to about 30% by weight of polycarbonate polymer. In further embodiments, the polycarbonate polymer is present in the composition in an amount of from about 5% to about 25% by weight, or from about 5% to about 20% by weight, or from about 10% to about 30% by weight, or from about 10% to about 25% by weight, or from about 10% to about 20% by weight, or about 15% by weight.

[0038] In certain embodiments, wherein the composition comprises the polycarbonate-siloxane copolymer described above, the composition may have a notched Izod impact strength of at least 40 Joules per meter (J / m) at −30° C., or an unnotched Izod impact strength of at least 165 J / m at −30° C., where the Izod impact strength is tested according to ASTM D256 and ASTM D4812. In further embodiments, the composition has a notched Izod impact strength at −30° C. of 40 to 100 J / m, or 40 to 90 J / m, or 40 to 80 J / m, or 40 to 70 J / m, or 40 to 60 J / m. In other embodiments, the composition has an unnotched Izod impact strength at -30°C of 165 to 220 J / m, or 165 to 210 J / m, or 165 to 200 J / m, or 165 to 190 J / m, or 165 to 185 J / m.

[0039] Manufacturing method One or any of the aforementioned components described herein may first be dry-blended with each other or with any combination of the aforementioned components and then fed into the extruder through one or more feeders, or may be fed separately into the extruder through one or more feeders. The fillers used in the present disclosure may also be first processed into a masterbatch and then fed into the extruder. The components may be fed into the extruder through a throat hopper or any side feeder.

[0040] Extruders used in this disclosure may have a single screw, multiple screws, intermeshing co-rotating or counter-rotating screws, non-intermeshing co-rotating or counter-rotating screws, reciprocating screws, pinned screws, screened screws, pinned barrels, rolls, rams, helical rotors, co-kneaders, disc pack processors, various other types of extrusion equipment, or a combination comprising at least one of the foregoing.

[0041] The components may also be mixed together and then melt-blended to form the thermoplastic composition. Melt-blending of the components involves the use of shear forces, extensional forces, compression forces, ultrasonic energy, electromagnetic energy, thermal energy, or a combination comprising at least one of the foregoing forces or forms of energy.

[0042] The barrel temperature of the extruder during compounding can be set to a temperature at which at least a portion of the polymer has reached approximately its melting temperature if the resin is a semi-crystalline organic polymer, or at least its pour point (e.g., glass transition temperature) if the resin is an amorphous resin.

[0043] A mixture containing the aforementioned components can be subjected to multiple blending and molding steps, if desired. For example, the thermoplastic composition can be first extruded and formed into pellets. The pellets can then be fed to a molding machine, where they can be formed into any desired shape or product. Alternatively, the thermoplastic composition emerging from a single melt blender can be formed into a sheet or strand and subjected to post-extrusion processes such as annealing, uniaxial or biaxial stretching, etc.

[0044] The melt temperature in this process can be kept as low as possible in some embodiments to avoid excessive thermal decomposition of the components. In certain embodiments, the melt temperature is maintained between about 210°C and about 290°C, although higher temperatures can be used provided that the residence time of the resin in the processing equipment is kept relatively short. In some embodiments, the melt-processed composition exits the processing equipment, such as an extruder, through small exit holes in a die. The resulting strands of molten resin can be cooled by passing the strands through a water bath. The cooled strands can be chopped and pelletized for packaging and further processing.

[0045] Manufactured product In certain embodiments, the present disclosure relates to shaped, formed, or molded articles comprising the thermoplastic compositions. The thermoplastic compositions can be formed into useful shaped articles by various means, such as injection molding, extrusion, compression molding, rotational molding, blow molding, and thermoforming, to form articles and structural components of, for example, radar sensors, cameras, electronic control units (ECUs), support brackets, or radar enclosures. In further embodiments, the articles are extruded. In even further embodiments, the articles are injection molded.

[0046] Exemplary articles further include surface features that provide the article with high levels of microwave absorption (>85%) and low levels of microwave reflection (on the order of <2%) necessary for use in radar sensors or other similar applications. The surface appearance of molded parts can be modified to increase microwave (MW) radiation absorption and decrease reflection. Two-dimensional and three-dimensional features molded or imprinted into the surface of a part (e.g., internal radar components or external radar enclosures) can be provided to capture more incoming microwave radiation so that reflection from the surface can be minimized. Features added to the surface of molded parts, such as wedges, pyramids, cones, or many other geometric 2D or 3D shapes, act as microwave radiation sinks, blocking electromagnetic waves by forcing them to bounce when they impact the feature, causing the waves to lose energy with each bounce, thus reducing reflection and increasing absorption in accordance with the principles of anechoic chambers. These features are of a specific geometric design that allows them to efficiently attenuate electromagnetic waves as they strike the part, thus promoting the dissipation of the energy contained in the waves, increasing absorption and decreasing reflection. For example, 2D features such as long triangular wedges having a height / base ratio of 2:1 to 10:1, or in certain embodiments, about 5:1, can provide certain materials with a percent power absorption of greater than 85% and a percent power reflection of less than about 6% when tested at a 77 GHz frequency. In some examples, on a plaque that is nominally 1 / 8 inch thick, a carbon-filled polymer resin can be formed that absorbs at least 90% of incoming microwave radiation and reflects less than 1% when observed at a frequency of 77 GHz.

[0047] It will be appreciated that molded features may be incorporated into the surface of the part during its formation (i.e., formed continuously with the part), or they may be molded (or imprinted) separately onto an already formed part.

[0048] Further aspects of the present disclosure include automotive radar sensor components (e.g., plates, enclosures, and covers) molded from a material comprising a polymer and carbon black powder as a microwave-absorbing filler. The molded parts have improved microwave absorption properties, including microwave absorption efficiency, absorption bandwidth, shielding effectiveness, attenuation, and electrical surface and volume resistivity. In certain aspects, the molded parts contain micron-sized features that can capture additional microwave radiation compared to parts molded from the same composition that do not contain micron-sized features.

[0049] Yet further aspects include articles including, but not limited to, radar sensors, cameras, electronic control units (ECUs), support brackets, radar enclosures, and the like, which include a molded part made from a microwave absorbing material (absorber) and have at least two openings that allow transmission of microwave radiation between a transmitting antenna and a receiving antenna located on the sensor's printed circuit board.

[0050] In certain embodiments, the article includes a shaped plaque including a surface having micron-sized features, the shaped plaque having a thickness of about 2.7 mm to about 2.9 mm, and the region of the shaped plaque including the micron-sized features exhibits a percent absorbed power measured in transmission mode of at least 85% and a percent reflected power measured in transmission mode of 2% or less when observed according to the free-space method at frequencies between about 75 GHz and 110 GHz, and the micron-sized features have a height-to-base ratio of 2:1 to 10:1.

[0051] In some embodiments, at least 1 square inch (1.0 in) of the sample 2 A 6" (inch) x 8" x 1 / 8" sample of a molded plaque containing micron-sized features over a surface area of ​​at least 1.5 inches of the sample has the indicated absorbed and reflected power characteristics. 2 , or at least 2.0 inches 2 , or at least 2.5 inches 2 , or at least 3.0 inches2 , or at least 3.5 inches 2 , or at least 4.0 inches 2 , or at least 4.5 inches 2 , or at least 5.0 inches 2 , or at least 6.0 inches 2 , or at least 7.0 inches 2 , or at least 8.0 inches 2 In a specific embodiment, the molded plaque comprises micron-sized features over a surface area of ​​3.5 inches. 2 ~4.5 inches 2 , or about 4 inches 2 The sample contains micron-sized features on a surface area of ​​.mu.m.

[0052] In some embodiments, the micron-sized features are two-dimensional or three-dimensional in the linear direction. In certain embodiments, the micron-sized features have a height to base ratio of 3:1 to 9:1, or 3:1 to 8:1, or 3:1 to 7:1, or 3:1 to 6:1, or 4:1 to 9:1, or 4:1 to 8:1, or 4:1 to 7:1, or 4:1 to 6:1, or about 5:1.

[0053] In further embodiments, neither the base nor the height of a micron-sized feature has a dimension greater than 3000 microns (μm). In certain embodiments, neither the base nor the height of a micron-sized feature has a dimension greater than 2800 μm, or greater than 2600 μm, or greater than 2400 μm, or greater than 2200 μm, or greater than 2000 μm, or greater than 1800 μm, or greater than 1600 μm, or greater than 1400 μm, or greater than 1200 μm, or greater than 1000 μm. However, it will be appreciated that if a feature is two-dimensional in a linear direction, the linear direction may have a length greater than 1000 microns. See, e.g., Figures 16B and 17A. It will also be appreciated that the thickness of a plaque / article / component containing a feature is independent of the dimension of the feature. For example, thicker plaques / articles / components may typically contain larger features, but this is not necessarily the case.

[0054] In some embodiments, an article comprising micron-sized features comprises a thermoplastic resin according to any of the embodiments described herein, particularly a polypropylene polymer and about 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes. In a particular embodiment, a molded plaque comprises a polypropylene polymer and about 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes, the carbon nanotubes having an average diameter of about 5-15 nm and a size of at least about 100 m. 2 / gr surface area, and 10 -3 It has a volume resistivity of ohm.cm or less.

[0055] Various combinations of elements of the present disclosure are encompassed by the present disclosure, such as combinations of elements from dependent claims that are dependent on the same independent claim.

[0056] Aspects of the Disclosure In various aspects, the present disclosure relates to and includes at least the following aspects:

[0057] Aspect 1. A composition comprising a thermoplastic resin, the thermoplastic resin comprising: a polypropylene polymer; 1. About 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes, wherein the carbon nanotubes have an average diameter of about 5 to 15 nanometers (nm) and an average diameter of at least about 100 square meters per gram (m 2 / gr) surface area, and 10 -3 a filler having a volume resistivity of 0.01 ohm.cm or less, the composition exhibits a volume electrical resistivity of 2.0E+14 Ohm.cm to 1.0E+03 Ohm.cm when measured in accordance with ASTM D257; a molded sample of the composition having a thickness of about 3.1 millimeters (mm) to about 3.3 mm exhibits a percent absorbed power of at least 65% measured in a transmission mode when observed according to a free-space method at a frequency of about 75 GHz to about 110 GHz; A composition wherein the combined weight percentage of all components does not exceed 100% by weight, and all weight percentages are based on the total weight of the composition. In certain embodiments, the molded sample has a thickness of about 3.10 mm, or about 3.11 mm, or about 3.12 mm, or about 3.13 mm, or about 3.14 mm, or about 3.15 mm, or about 3.16 mm, or about 3.17 mm, or about 3.175 mm, or about 3.18 mm, or about 3.19 mm, or about 3.20 mm, or about 3.21 mm, or about 3.22 mm, or about 3.23 mm, or about 3.24 mm, or about 3.25 mm, or about 3.26 mm, or about 3.27 mm, or about 3.28 mm, or about 3.29 mm, or about 3.30 mm.

[0058] Embodiment 2. The composition of embodiment 1, wherein the composition comprises about 0.6% to about 2.75% by weight of carbon nanotubes, and wherein the percent absorbed power measured in transmission mode is at least 80% when observed at a frequency of 77 GHz.

[0059] Embodiment 3. The composition of embodiment 1 or 2, wherein the polypropylene polymer comprises a polypropylene homopolymer, a polypropylene copolymer, or a combination thereof.

[0060] Aspect 4. The composition of any one of Aspects 1-3, wherein the carbon nanotubes are in the form of a polypropylene-based masterbatch.

[0061] Embodiment 5. The composition of embodiment 4, wherein the polycarbonate copolymer has a carbon nanotube content of about 15% to about 25% by weight.

[0062] Embodiment 6. The composition of any one of Embodiments 1-5, wherein the composition further comprises one or more additional reinforcing fillers.

[0063] Embodiment 7. The composition of embodiment 6, wherein the reinforcing filler comprises glass fibers.

[0064] Embodiment 8. The composition of any one of embodiments 1-7, wherein the composition further comprises a polycarbonate polymer.

[0065] Embodiment 9. The composition of embodiment 8, wherein the polycarbonate polymer comprises a polycarbonate-siloxane copolymer having a siloxane content of 5% to 45% by weight.

[0066] Embodiment 10. The composition of embodiment 9, wherein the composition has a notched Izod impact strength at -30°C of at least 40 Joules per meter (J / m), or an unnotched Izod impact strength at -30°C of at least 165 J / m, wherein the Izod impact strength is tested according to ASTM D256 and ASTM D4812.

[0067] Embodiment 11. An article comprising the composition of any one of embodiments 1-10.

[0068] Aspect 12. The article of aspect 11, wherein the article is a component of an automotive radar sensor.

[0069] Embodiment 13. An article comprising, consisting of, or consisting essentially of a molded plaque comprising a surface having micron-sized features, a region of the shaped plaque having a thickness of about 2.7 mm to about 2.9 mm and containing micron-sized features, when observed according to a free-space method at frequencies between about 75 GHz and 110 GHz, exhibits a percent absorbed power measured in transmission mode of at least 85% and a percent reflected power measured in transmission mode of 2% or less; The article, wherein the micron-sized features have a height-to-base ratio of 2:1 to 10:1. In certain embodiments, the region of the shaped plaque has a thickness of about 2.70 mm, or about 2.71 mm, or about 2.72 mm, or about 2.73 mm, or about 2.74 mm, or about 2.75 mm, or about 2.76 mm, or about 2.77 mm, or about 2.78 mm, or about 2.79 mm, or about 2.80 mm, or about 2.81 mm, or about 2.82 mm, or about 2.83 mm, or about 2.84 mm, or about 2.85 mm, or about 2.86 mm, or about 2.87 mm, or about 2.88 mm, or about 2.89 mm, or about 2.90 mm.

[0070] Embodiment 14. The article of embodiment 13, wherein the micron-sized features are two-dimensional or three-dimensional in the linear direction.

[0071] Embodiment 15. The article of embodiment 13 or 14, wherein the micron-sized features have a height-to-base ratio of 4:1 to 6:1.

[0072] Embodiment 16. The article of any one of embodiments 13 to 15, wherein the polygon is a triangle.

[0073] Embodiment 17. The article of any one of embodiments 13-16, wherein neither the base nor the height of the micron-sized features has a dimension greater than 1000 microns (μm).

[0074] Embodiment 18. The article of any one of embodiments 13-17, wherein the molded plaque comprises the composition of any one of embodiments 1-10.

[0075] Embodiment 19. A molded plaque comprising a polypropylene polymer and about 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes, the carbon nanotubes having an average diameter of about 5 to 15 nm and a length of at least about 100 m. 2 / gr surface area, and 10 -3 18. The article of any one of embodiments 13-17, having a volume resistivity of less than or equal to Ohm.cm. [Example]

[0076] The following examples are presented to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices, and / or methods claimed herein are made and evaluated, and are intended to be purely illustrative and are not intended to limit the present disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperatures, etc.), but some errors and deviations should be accounted for. Unless otherwise indicated, parts are parts by weight, temperature is °C or ambient temperature, and pressure is at or near atmospheric pressure. Unless otherwise indicated, percentages with respect to compositions are expressed as % by weight.

[0077] There are many variations and combinations of reaction conditions, such as component concentrations, desired solvents, solvent mixtures, temperatures, pressures, and other reaction ranges and conditions, that can be used to optimize the purity and yield of the products obtained from the described processes. Optimizing such process conditions will require only reasonable and routine experimentation.

[0078] Example 1 - Composition Compositions formed according to embodiments of the present disclosure included one or more of the ingredients listed in Table 1.

[0079] [Table 1]

[0080] Unless otherwise indicated, the examples and comparative compositions were prepared as shown in Table 2 and amounts are in weight percent.

[0081] [Table 2]

[0082] Certain mechanical properties of the compositions in Table 2 were evaluated and the results are shown in Table 3.

[0083] [Table 3-1]

[0084] [Table 3-2]

[0085] Graphical representations of some of the results are included in Figures 1A-3. Figures 1A and 1B show notched and unnotched Izod impact properties at 23°C and -30°C, respectively. Surface and volume electrical resistivities are illustrated in Figure 2. Melt flow rates are shown in Figure 3.

[0086] From the data and figures, it is observed that the IZOD impact strength of these materials changed little when tested at either room temperature (23°C) or low temperature (-30°C), likely due to the presence of polycarbonate-siloxane copolymer present in these formulations. Figure 2 shows that electroosmosis appears to begin at a carbon nanotube concentration of approximately 1 wt%. Figure 3 shows that the viscosity of these materials increased (MFR decreased) as the concentration of carbon nanotubes in the formulation increased from approximately 0.1 wt% to 5 wt%.

[0087] The dielectric properties of the compositions described herein can be evaluated using the free-space method. The free-space method involves a vector network analyzer with two antennas facing each other and a sample holder positioned equidistant between them. The basic experimental quantities generated by the free-space method are called scattering parameters, or S-parameters, and are used to describe the input-output relationship between different ports of an electrical network in terms of amplitude and phase versus frequency. S-parameters are typically identified with two subscripts, the first of which refers to the response port and the second to the incident port. Thus, S21 refers to the response at port 2 resulting from a signal at port 1. Scattering parameters are complex numbers with real and imaginary parts, and they describe the amount of microwave radiation reflected from or transmitted through a sample. For example, the scattering parameter S11 for reflection represents the signal originating from antenna 1 and received by the same antenna after hitting the sample. Similarly, the scattering parameter S21 for transmission represents the signal originating from antenna 1 and received by antenna 2 after transmitting through the material under test. Scattering parameters for reflection and transmission, S22 for reflection and S12 for transmission, representing the signal originating from antenna 2, can also be defined. Using the S-parameter matrix, the reflection coefficient and transmission gain from each side of the two-port network can be determined, from which the four previously defined S-parameters, S11, S22, S21, and S12, can be identified. Software is then used to convert the scattering parameter output of the network analyzer into dielectric properties. Free-space measurement techniques provide a method for determining the permittivity and magnetic permeability of a magnetic dielectric material under test. These methods are non-contact, meaning the material under test does not come into direct contact with the passive components of the equipment involved in the measurement.

[0088] Schematics of the apparatus used to determine the dielectric properties of the materials of the present disclosure using the free-space method for unbacked and metal-backed samples are shown in Figures 4A and 4B, respectively. Injection-molded plaques measuring 6" x 8" x 1 / 8" are used for these free-space dielectric measurements.

[0089] Dielectric measurements using the free-space method can be performed in two different modes: transmission mode and metal-backed reflection mode. The transmission mode of measurement measures three types of radiation: absorption into the sample, reflection from the sample, and transmission through the sample. In the metal-backed reflection mode of measurement, placing a metal plate (stainless steel, aluminum, etc.) between the material under test and the receiving antenna completely suppresses transmission through the sample, allowing only microwave absorption into and reflection from the material to be evaluated. The combination of two antennas in transmission mode allows only the scattering parameter for reflection, S11, and the scattering parameter for transmission, S21, to be measured. Therefore, the amount (percentage) of radiation absorbed by the material under test is calculated as the difference between the total energy impinging on the sample (or 100%) and the sum of the amount (percentage) of radiation transmitted through the sample (measured from S21 and reaching the receiving antenna) and the amount (percentage) of radiation reflected from the sample (measured from S11 and returning to the emitting antenna). In many applications, when performing measurements using transmission mode, it is desirable to maximize the percent absorbed power and minimize the percent reflected and transmitted power. There are several dielectric properties that radar designers consider when selecting materials for microwave radar interference applications. Complex permittivity (real and imaginary parts), the amount of radiation absorbed, reflected, or transmitted by the material, shielding effectiveness, return loss, and attenuation are just some of the material properties of interest for the manufacture of plastic components for radar sensor applications. The frequency of the incoming radiation and the thickness of the material are also important when capturing microwave energy that, if not eliminated or minimized, would interfere with the proper operation of automotive electronic sensors.

[0090] The dielectric properties of the compositions in Table 2 were evaluated at frequencies in the W-band (75-110 GHz), and selected results at 77 GHz are shown in Table 4.

[0091] [Table 4]

[0092] The percent power (reflected, absorbed, and transmitted) in the transmission mode at 77 GHz is illustrated graphically in Figure 5. From the data in Table 4 and Figure 5, it can be observed that as the concentration of carbon nanotubes in the formulation increased and the material became increasingly conductive, the percent reflected power in the transmission mode mostly increased and the percent transmitted power in the transmission mode decreased. The percent absorbed power in the transmission mode first increased from about 33% to about 76% at low concentrations of carbon nanotubes, then decreased from about 71% to about 63%, and passed a maximum of about 81% at about 1 wt% carbon nanotubes.

[0093] The dielectric properties of the compositions in Table 2 over the full W-band (75-110 GHz) are graphically illustrated in Figures 6A-10. Figures 6A-6C illustrate the real part of the complex permittivity, the imaginary part of the complex permittivity, and the attenuation constant, respectively. Figure 7 illustrates the total shielding effectiveness, Figure 8 illustrates the percent power absorbed in the transmission mode, Figure 9 illustrates the percent power absorbed in the metal-backed reflection mode, and Figure 10 illustrates the percent power (absorbed, reflected, and transmitted) in the transmission mode for composition Ex1.3. From these figures, it can be observed that both the real and imaginary parts of the complex permittivity increased as the concentration of carbon nanotubes in the composition increased for all frequencies investigated. The same observation can be made for the attenuation constant (becoming more negative) and the total shielding effectiveness (becoming more positive). Figure 8 shows that the percent power absorbed in the transmission mode remained approximately constant as the frequency of the incoming radiation increased from 75 GHz to 110 GHz. Figure 9 shows that the percent power absorbed in the metal-backed reflection mode can reach values ​​above 80% for certain frequencies and compositions, as more radiation striking the metal plate behind the test sample is reflected and reabsorbed by the material. Figure 10 shows that a 3.3 mm thick sample of composition Ex1.3 can absorb more than 80% and reflect less than 20% for all frequencies investigated.

[0094] Example 2 - Articles containing micron-sized features Articles formed according to embodiments of the present disclosure included one or more of the components listed in Table 5.

[0095] [Table 5]

[0096] Unless otherwise indicated, the thermoplastic PP base compositions were prepared as shown in Table 6, amounts are in wt %.

[0097] [Table 6]

[0098] Carbon powder (carbon black) was included to impart electrical conductivity and microwave interference properties to the composition. Certain mechanical properties of compositions Ex2.3 and Ex2.4 were evaluated and the results are shown in Table 7.

[0099] [Table 7]

[0100] From the data in Table 7, it is observed that when the concentration of carbon powder in the formulation increased from 4 wt% to 10 wt%, both the specific gravity and melt viscosity increased, and both the surface / volume electrical resistivity and MFR decreased.

[0101] The dielectric properties of the compositions in Table 6 were evaluated at frequencies in the W-band (75-110 GHz), and selected results at 77 GHz are shown in Table 8.

[0102] [Table 8]

[0103] The percent power (reflected, absorbed, transmitted) in transmission mode at 77 GHz is illustrated graphically in Figure 11. As Table 8 shows, these materials can absorb about 69% to about 78% of the incoming microwave radiation at a 77 GHz frequency, and the amount of energy reflected by these compositions at 77 GHz ranges from about 13% to 31%.

[0104] The dielectric properties of the compositions in Table 6 across the W-band (75-110 GHz) are graphically illustrated in Figures 12A-15B. Figures 12A-12C illustrate the real part of the complex permittivity, the imaginary part of the complex permittivity, and the attenuation constant, respectively. Figure 13 shows the total shielding effectiveness, Figure 14 illustrates the percent power absorbed in the transmission mode, and Figures 15A and 15B illustrate the percent power in the transmission mode and the percent power (absorbed, reflected, and transmitted) in the metal-backed reflection mode, respectively, for composition Ex2.3 observed on a 3.1 mm thick sample. From these figures, it can be observed that both the real and imaginary parts of the complex permittivity increased as the concentration of carbon black powder in the composition increased for all frequencies investigated. The same observation can be made for the attenuation constant (becoming more negative) and the total shielding effectiveness (becoming more positive). Figure 14 shows that the percent power absorbed in transmission mode remained nearly constant as the frequency of the incoming radiation increased from 75 GHz to 110 GHz. Figures 15A and 15B show that the percent power in transmission mode and metal-backed reflection mode was similar, which can be explained by the fact that the sample measured in transmission mode showed very low transmission for all frequencies investigated.

[0105] In some applications, the above-mentioned levels of microwave absorption and reflection may not be sufficient to capture incoming electromagnetic radiation that, if not eliminated or minimized, could interfere with the normal operation of automotive radar sensors. These applications typically require a combination of microwave absorption levels of 85% or greater and microwave reflection levels of approximately 2% or less. Through careful experimentation, two-dimensional features were laser engraved into the surface of a relatively smooth injection-molded part. These features were observed to contribute to increased microwave absorption and reduced microwave reflection compared to a smooth molded part of the same composition without these features. These geometric features were engraved in the form of two-dimensional triangular wedges with bases of approximately 100 microns (μm), heights of approximately 500 μm, and lengths of 2 inches (in), with no separation between successive rows of these aligned features. 2D front and side perspective sketches of the geometric features are shown in Figures 16A and 16B, respectively.

[0106] These features block incoming electromagnetic waves by forcing them to bounce back and forth when they impact the part's surface, causing the waves to lose energy with each bounce, thus reducing reflection and increasing absorption, in accordance with anechoic chamber principles. These features were laser engraved into a 2-inch by 2-inch square area in the center of a 6-inch by 8-inch rectangular plaque. This pattern was tested for its dielectric properties in the W-band (75-110 GHz frequencies) using a vector network analyzer. Figures 17A and 17B are microscope images showing the top and cross-sectional views, respectively, of a 2D triangular wedge engraved into the surface of a smooth molded part using laser patterning techniques. In some embodiments, features can be molded into the surface of a smooth molded part.

[0107] More specifically, the geometric features imprinted on the surface of the molded plaque of Example 2 were in the form of two-dimensional triangular wedges with bases of approximately 100 microns, heights of approximately 500 microns, and lengths of 2 inches, with no separation between successive rows of these aligned features. Thus, the micron-sized features had a height-to-base ratio of 5:1 (500 μm height and 100 μm base), which is between 2:1 and 10:1. The length of the wedge (in this case, 2 inches) is not relevant in determining the height-to-base ratio.

[0108] Similarly, three-dimensional features in the form of pyramids, cones, etc., can be imprinted or molded into the surface of smooth molded parts to further enhance the microwave absorption / reflection effects observed in these materials. Exemplary three-dimensional images are shown in Figures 18A-18C. Exemplary three-dimensional features are further illustrated in Figures 23A and 23B. Three-dimensional features can include, for example, bases having triangular, square, rectangular, pentagonal, or hexagonal cross-sections as illustrated in Figure 23A, or circular cross-sections as illustrated in Figure 23B.

[0109] In describing the height-to-base ratio of a three-dimensional feature, the height-to-base ratio can be described by comparing the height of the feature (e.g., the height of a three-dimensional feature such as a pyramid having a shape such as that shown in FIG. 23A, or the height of a cone-shaped feature such as that shown in FIG. 23B) to the length of the base of the feature (e.g., the length of the base of the pyramid or cone).

[0110] The above 2D features were imprinted into plaques of several compositions, and their dielectric properties were evaluated and compared to those of plaques of the same compositions without the features. The imprinted plaques were tested in transmission mode and metal-backed reflection mode using the setups shown in Figures 19A and 19B, respectively.

[0111] The dielectric properties of the imprinted composition Ex2.3 in the W-band (75-110 GHz) are graphically illustrated in Figures 20A and 20B. Specifically, the percent power in transmission mode is shown in Figure 20A, and the percent power in metal-backed reflection mode is shown in Figure 20B. From Figure 20A, it is observed that the absorption in transmission mode was at least 89% across the W-band, and the reflection was 1% or less across the band. From Figure 20B, it is observed that the absorption in metal-backed reflection mode was at least 97% across the W-band, and the reflection was 3% or less across the band.

[0112] Example 3 - Comparison with conventional carbon black compositions Some conventional radar-absorbing compositions containing Ensaco® 360G carbon black are shown in Table 9.

[0113] [Table 9]

[0114] These conventional compositions are available from SABIC. As shown in Figure 21, they all have similar dielectric properties at 77 GHz, with absorption of about 65% and reflection of about 35%, with virtually no transmission.

[0115] Additional conventional compositions containing carbon (Ensaco® 360G CB or carbon nanotubes (CNTs)) are listed in Table 10.

[0116] [Table 10]

[0117] Plaques of compositions C3.6-C3.9 were prepared with and without 2D features as described above, and their dielectric properties were evaluated at 77 GHz and compared with example composition Ex2.3 from Example 2 above. The results are shown in Table 11.

[0118] [Table 11]

[0119] The imprinted plaques bear the designation "(I)." The results are graphically depicted in Figure 22. From the data, it was observed that when a 2D triangular wedge was added to the part surface, all compositions exhibited increased microwave absorption and reduced microwave reflection, with the percent improvement in absorption varying from 9 to 18 percentage points depending on the composition. In particular, example composition Ex2.3 was observed to be able to achieve a combined effect of at least 85% microwave absorption and less than 2% reflection when observed at a frequency of 77 GHz. Compositions C3.6 to C3.9 were unable to achieve either the 85% absorption threshold or the less than 2% reflection threshold. These results also indicated that the effect of adding micron-sized features to the surface of molded parts was independent of composition but correlated with the formulation of the material used to mold the test parts, suggesting a synergistic effect between the geometric features and the composition of the test parts into which these features were imprinted. The reduction in reflected power affected by the presence of 2D features varied, for example, from about 20:1 in composition Ex2.3 to about 4:1 in composition C3.8 to only about 2:1 in composition C3.6.

[0120] The above description is intended to be illustrative, not limiting. For example, the above examples (or one or more aspects thereof) could be used in combination with each other. Other aspects may be utilized by those of ordinary skill in the art, etc., upon review of the preceding description. The Abstract is provided to comply with 37 CFR §1.72(b) to enable the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be construed as intending that an unclaimed disclosed feature is essential to a claim. Rather, inventive subject matter may consist of less than all features of a particular disclosed embodiment. Accordingly, the following claims are hereby incorporated into the Detailed Description as an example or embodiment, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the present disclosure should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A composition comprising a thermoplastic resin, the thermoplastic resin comprising: a polypropylene polymer; 1. About 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes, the carbon nanotubes having an average diameter of about 5 to 15 nanometers (nm) and an average diameter of at least about 100 square meters per gram (m ２ / gr) surface area, and 10 －３ a filler having a volume resistivity of 0.01 ohm. centimeter (Ohm.cm) or less; the composition exhibits a volume electrical resistivity of from 2.0E+14 Ohm.cm to 1.0E+03 Ohm.cm, as measured in accordance with ASTM D257; a molded sample of the composition having a thickness of about 3.1 millimeters (mm) to about 3.3 mm exhibits a percent power absorption of at least 65% measured in a transmission mode when observed according to a free-space method at a frequency of about 75 GHz to about 110 GHz; A composition wherein the combined weight percentage of all components does not exceed 100% by weight, and all weight percentages are based on the total weight of said composition.

2. 10. The composition of claim 1, wherein the composition comprises from about 0.6% to about 2.75% by weight of the carbon nanotubes, and the percent absorbed power measured in transmission mode is at least 80% when observed at a frequency of 77 GHz.

3. 3. The composition of claim 1, wherein the carbon nanotubes are in the form of a polypropylene-based masterbatch.

4. 4. The composition of claim 3, wherein the polypropylene-based masterbatch has a carbon nanotube content of about 15% to about 25% by weight.

5. The composition of any one of claims 1 to 4, wherein the composition further comprises a reinforcing filler comprising glass fibers.

6. The composition of any one of claims 1 to 5, wherein the composition further comprises a polycarbonate polymer comprising a polycarbonate-siloxane copolymer having a siloxane content of from about 5% to about 45% by weight.

7. 7. The composition of claim 6, wherein the composition has a notched Izod impact strength of at least 40 Joules per meter (J / m) at −30° C. or an unnotched Izod impact strength of at least 165 J / m at −30° C., wherein the Izod impact strength is tested according to ASTM D256 and ASTM D4812.

8. An article comprising the composition of any one of claims 1 to 7, said article being a component of an automotive radar sensor.

9. 1. An article comprising a molded plaque comprising a surface having micron-sized features, a region of the shaped plaque having a thickness of about 2.7 mm to about 2.9 mm and containing the micron-sized features, when observed according to a free-space method at a frequency of about 75 GHz to 110 GHz, exhibits a percent absorbed power measured in transmission mode of at least 85% and a percent reflected power measured in transmission mode of 2% or less; The article, wherein the micron-sized features have a height-to-base ratio of 2:1 to 10:

1.

10. The article of claim 9 , wherein the micron-sized features are two-dimensional in a linear direction or three-dimensional.

11. The article of claim 9 or 10, wherein the micron-sized features have a height to base ratio of 4:1 to 6:

1.

12. The article of any one of claims 9 to 11, wherein the polygon is a triangle.

13. The article of any one of claims 9 to 12, wherein neither the base nor the height of the micron-sized features has a dimension greater than 1000 microns (μm).

14. The article of any one of claims 9 to 13, wherein the molded plaque comprises the composition of any one of claims 1 to 7.

15. The molded plaque comprises a polypropylene polymer and about 0.15% to about 4.75% by weight of a filler comprising carbon nanotubes, the carbon nanotubes having an average diameter of about 5-15 nm and a length of at least about 100 m. ２ / gr surface area, and 10 －３ 14. The article of any one of claims 9 to 13, having a volume resistivity of no more than 100 Ohm.cm.

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