Polypropylene composition capable of enhancing microwave absorption and weakening microwave reflection

Abstract

A composition comprises a thermoplastic resin comprising: a polypropylene polymer; and from about 0.15 wt% to about 4.75 wt% of a filler comprising carbon nanotubes. The carbon nanotubes have an average diameter of about 5 to 15 nanometers (nm), a surface area of at least about 100 square meters per gram (m2 / gr), and a volume resistivity of 10-3 ohm.cm (Ohm.cm) or less. The composition exhibits a volume resistivity of between 2.0 E + 14 Ohm.cm and 1.0 E + 03 Ohm.cm, and a molded sample of the composition exhibits an absorption power percentage of at least 65% measured in transmission mode at a frequency of from about 75 GHz to about 110 GHz. Also described are molded articles comprising micron-sized features that impart high absorption and low reflection properties to the articles.

Description

Technical Field

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

[0002] According to the Association For Safe International Road Travel (ASIRT), more than 1 million people die in road traffic accidents every year, and tens of millions are injured or disabled. Road traffic accidents are one of the leading causes of death, causing global losses of more than $500 billion, which accounts for a large portion of each country's annual GDP. Unless action is taken, road traffic injuries are expected to become the fifth leading cause of death by 2030 ( International Road Road Safety Association - ASIRT, 2016 ). For these reasons, the automotive industry is increasingly leveraging Advanced Driver Assistance Systems (ADAS) to assist drivers with features such as adaptive cruise control, automatic parking, reverse warning, blind spot detection, lane departure warning, collision avoidance, pedestrian detection, and many others.

[0003] Due to the reduced cost and increased availability of radar sensors, they are common in today's automotive safety field and are used in the most advanced ADAS systems. These automotive radar systems can be classified into three subcategories based on the range or distance of their operation: short-range, medium-range, and long-range automotive radars. Each of these sensors has different applications, where long-range radars (range exceeding about 100 meters) are typically used for forward collision avoidance and adaptive cruise control, mainly operating in the W-band of the electromagnetic spectrum at a frequency of about 75 to 110 GHz. On the other hand, short-range and medium-range radars (range of tens of meters) are used for blind spot detection, parking assistance systems, pre-collision alerts, or lane departure warnings, and mainly operate in the K-band at a frequency of about 18 to 26.5 GHz. Due to the strict regulations currently being implemented regarding low-frequency power output, it is expected that the frequency range of the K-band will be less used in automotive radar sensors for ADAS applications ( Source: R. Burger, T. Salinero, T., S. Sumida, "Beyond The Headlights: ADAS and Autonomous Sensing"; Market Report, Woodside Capital Partners; September 2016 ).

[0004] For a radar sensor to operate effectively, it is necessary to protect the radar sensor from interfering stray electromagnetic radiation sources. Since metal itself is a reflector of microwave radiation and thus a poor absorber, its use has proven to be of limited value in applications that require a high level of microwave absorption and a low level of microwave reflection. On the other hand, polymer / carbon composites are superior to metals, not only because they have higher microwave absorption properties, but also because they have lower density and cost, are easier to mold, and can be more directly made into mass-molded parts. Generally, carbon fillers can capture or deflect microwave (MW) radiation incident on the outer wall of the housing, thereby protecting the electronic sensor inside the cavity. Moderately high dielectric constant and conductivity, as well as large dielectric and magnetic losses, are some of the characteristics required for materials used in microwave shielding. In some applications, carbon nanotubes are superior to carbon powder, graphite, or carbon fiber because they can provide sufficient microwave interference performance at relatively low loadings. For example, reducing the carbon loading will improve the ductility, impact strength, surface aesthetics, and flowability of these materials under high shear rate conditions. The amount of carbon filler used in these compositions generally depends on the type of carbon used, where carbon fiber and carbon nanotubes require lower loadings to achieve a relatively high level of microwave absorption. On the other hand, low-structure (large particle size, small specific surface area) carbon black powder requires a higher loading when used in resins designed to achieve the same microwave absorption performance. Regardless of the type of filler used in these formulations, if the amount of carbon is too small, the transmittance will be high and both the absorption rate and the reflectance will be low; while if the amount of carbon is too large, the transmittance will generally be low and the reflectance will be high. Therefore, when designing materials with high microwave absorption but poor microwave reflectance for radar sensors operating at relatively high frequencies, it is very important to select the appropriate combination of carbon filler type and loading.

[0005] Microwave radiation (frequency of about 1 to 300 GHz, wavelength of about 300 to 1 mm) is the most commonly used electromagnetic energy source for the operation of radar sensors in automotive applications. Metals (aluminum, stainless steel, etc.), polymer composites containing metal fillers such as aluminum flakes, stainless steel fibers, and silver-plated polyamide fibers, metallized coatings, intrinsically conductive polymers (such as polyacetylene, polypyrrole, polythiophene, polyaniline, etc.), silicon carbide, ferrites (Fe2O3 + 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 destructive microwave electromagnetic radiation. Metals are the most commonly used materials for MW interference shielding, but they are heavy, expensive, and require complex processing to be molded into final parts. On the other hand, polymer / carbon composites are preferred because of their low density, low cost, ease of molding, and ability to be made into mass-molded parts.

[0006] Carbon (powder, flakes, fibers, nanotubes, etc.) is increasingly becoming a selected filler to endow thermoplastic polymers with electromagnetic interference properties. Unfilled thermoplastic polymers are mostly transparent (do not absorb, do not reflect) to microwave radiation. For example, when used in automotive hoods, polymer-carbon thermoplastic composites can protect radar sensors located inside the hood, thereby preventing the degradation of the electronic performance of the sensors by electromagnetic radiation from external sources. Additionally, carbon-containing elastomers such as silicone, polyurethane, and nitrile rubber can be used as high-loss, protective, and deformable sheets or covers to attenuate the resonance frequencies generated by the normal operation of sensors inside the cavity. In addition to thermoplastics and elastomers, these radar shielding materials are also available on the market in the form of liquid coatings, powder coatings, and closed-cell polymer foams. Electrical conductivity, dielectric loss, and magnetic loss, incident radiation frequency, and the wall thickness of the enclosure are some of the characteristics that are expected to affect the microwave interference performance of these materials.

[0007] The selection of microwave shielding materials for use in specific situations depends to some extent on the environment surrounding the electronic components to be protected (antennas, printed circuit boards, imaging devices for medical applications, etc.). When the incident radiation to be suppressed or minimized originates from outside the component to be protected, materials with microwave reflection properties may be sufficient, such as metal sheets (aluminum, stainless steel, etc.) or polymer composites containing metal fillers (e.g., materials from the Faradex™ product line of Saudi Basic Industries Corporation (SABIC)). In this case, the enclosure protects the electronic component by reflecting the incident radiation out of the cavity. On the other hand, if the incident radiation originates from inside the cavity to be protected, materials that absorb microwave energy may be required to isolate the sensor component from the standing electromagnetic waves (oscillations) caused by cavity resonances. Microwave absorbers can also be used to line the inner walls of an anechoic chamber for testing, thereby eliminating unwanted reflections that would otherwise have a negative impact on the dielectric response of the material under test inside the chamber.

[0008] When selecting materials for microwave radar interference, radar designers consider a variety of dielectric properties. The complex dielectric constant (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 concern when manufacturing plastic components for radar sensor applications. As mentioned above, the frequency of the incident radiation and the material thickness are also important in capturing microwave energy, which, if not eliminated or minimized, can interfere with the normal operation of automotive electronic sensors.

[0009] Automotive radar sensors include a radome-type plastic component (which is mostly transparent to microwave radiation) and an absorber-type plastic component (which captures microwave energy within a specific frequency range to protect the sensor from external radiation interference). These plastic components are typically molded into final parts using relatively high injection pressures and melt temperatures to produce molded articles with a smooth appearance and no surface features. Microwave absorbing materials made with carbon as a microwave absorbing filler and molded into smooth surface parts can only provide a certain level (high) of microwave absorption and (low) microwave reflection, which can limit the value of these materials 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] Aspects of the present disclosure address these and other drawbacks. Summary of the Invention

[0011] Aspects of the present disclosure relate to a composition comprising a thermoplastic resin, wherein the thermoplastic resin comprises a polypropylene polymer and from about 0.15 wt% to about 4.75 wt% of a filler comprising carbon nanotubes. The carbon nanotubes have an average diameter of about 5 to 15 nanometers (nm), a surface area of at least about 100 square meters per gram (m 2 / gr), and a volume resistivity of 10 -3 Ohm·cm or less. When measured according to ASTM D257, the composition exhibits a volume resistivity between 2.0E+14 Ohm·cm and 1.0E+03 Ohm·cm. When observed according to the free space method at frequencies from about 75 GHz to about 110 GHz, a molded sample having a thickness of about 3.1 millimeters (mm) to about 3.3 mm of the composition exhibits an absorption power percentage of at least 65% measured in the transmission mode. The combined weight percentage values of all components do not exceed 100 wt%, and all weight percentage values are based on the total weight of the composition.

[0012] Other aspects of the present disclosure relate to an article comprising a molded plate, the molded plate comprising a surface having micron-scale features, wherein when observed according to the free space method at frequencies from about 75 GHz to 110 GHz, a molded plate region having a thickness of about 2.7 mm to about 2.9 mm and comprising the micron-scale features exhibits an absorption power percentage of at least 85% measured in the transmission mode and a reflection power percentage of 2% or less measured in the transmission mode. The micron-scale features have a height-to-base ratio between 2:1 and 10:1. Brief Description of the Drawings

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

[0014] Figure 1A and 1B are diagrams showing the notched and unnotched Izod impact properties of comparative and example compositions according to aspects of the present disclosure at 23 °C and -30 °C.

[0015] Figure 2 is a diagram showing the surface and volume resistivity of comparative and example compositions according to aspects of the present disclosure.

[0016] Figure 3 is a diagram showing the melt flowrate (MFR) of comparative and example compositions according to aspects of the present disclosure.

[0017] Figure 4A and 4B are schematic diagrams of apparatuses for determining the dielectric properties of materials of the present disclosure using the free space method for non-backed samples and metal-backed samples, respectively.

[0018] Figure 5 is a diagram showing the percentage of power (reflection, absorption, and transmission) in the transmission mode of comparative and example compositions according to aspects of the present disclosure at 77 GHz.

[0019] Figures 6A to 6C are diagrams showing, respectively, the real part of the complex dielectric constant, the imaginary part of the complex dielectric constant, and the attenuation constant of comparative and example compositions according to aspects of the present disclosure.

[0020] Figure 7 is a diagram showing the total shielding effectiveness of comparative and example compositions according to aspects of the present disclosure.

[0021] Figure 8 is a diagram showing the percentage of absorbed power in the transmission mode of comparative and example compositions according to aspects of the present disclosure.

[0022] Figure 9 is a diagram showing the percentage of absorbed power in the metal-backed reflection mode of comparative and example compositions according to aspects of the present disclosure.

[0023] Figure 10 is a diagram showing the percentage of power (absorption, reflection, and transmission) in the transmission mode of composition Ex1.3.

[0024] Figure 11Is a diagram showing the percentage of power (reflection, absorption, and transmission) of an exemplary composition according to aspects of the present disclosure in transmission mode at 77 GHz.

[0025] Figures 12A to 12C Are diagrams respectively showing the real part of the complex dielectric constant, the imaginary part of the complex dielectric constant, and the attenuation constant of an exemplary composition according to aspects of the present disclosure at frequencies from 75 to 110 GHz.

[0026] Figure 13 Is a diagram showing the total shielding effectiveness of an exemplary composition according to aspects of the present disclosure at frequencies from 75 to 110 GHz.

[0027] Figure 14 Is a diagram showing the percentage of absorbed power of an exemplary composition according to aspects of the present disclosure in transmission mode at frequencies from 75 to 110 GHz.

[0028] Figure 15A And 15B Are diagrams respectively showing the percentage of power in transmission mode and the percentage of power (absorption, reflection, and transmission) in metal-backed reflection mode of Composition Ex2.3 observed on a 3.1 mm thick sample at frequencies from 75 to 110 GHz.

[0029] Figure 16A And 16B Are 2D front and side perspective sketches of geometric features according to aspects of the present disclosure.

[0030] Figure 17A And 17B Are microscopic images respectively showing a top view and a cross-sectional view of a 2D triangular wedge imprinted or molded on the surface of a smooth molded part according to aspects of the present disclosure.

[0031] Figures 18A to 18C Is an image of exemplary three-dimensional (3D) imprinted or molded features according to aspects of the present disclosure.

[0032] Figure 19A And 19B Are schematic diagrams of devices for testing an imprinted plate in transmission mode and metal-backed reflection mode respectively.

[0033] Figure 20A And 20B Are diagrams respectively showing the dielectric properties of the imprinted Composition Ex2.3 measured in transmission mode and metal-backed reflection mode at frequencies from 75 to 110 GHz.

[0034] Figure 21 Is a diagram showing the percentage of power of a conventional carbon black composition in transmission mode at 77 GHz.

[0035] Figure 22 A diagram showing the percentage of power in the transmission mode at 77 GHz for examples and conventional compositions with and without imprinting.

[0036] Figure 23A and 23B show exemplary three-dimensional (3D) imprinted or molded features in accordance with aspects of the present disclosure. Detailed Description

[0037] Before the compounds, compositions, articles, systems, devices, and / or methods of the present invention are disclosed and described, it is to be understood that unless otherwise specified, the compounds, compositions, articles, systems, devices, and / or methods are not limited to particular synthetic methods or, unless otherwise specified, to particular reagents, as the compounds, compositions, articles, systems, devices, and / or methods can of course vary. It should also be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0038] The present disclosure encompasses various combinations of elements of the present disclosure, such as combinations of elements from dependent claims attached to the same independent claim.

[0039] Furthermore, it should be understood that unless otherwise expressly stated, no method set forth herein is intended to be construed as requiring that its steps be performed in a particular order. Accordingly, where a method claim does not actually recite an order of its steps or where the steps are not otherwise specifically limited to a particular order in the claims or the specification, no inference of order is to be read into any aspect. This applies to any possible non-explicit basis of interpretation, including: logical issues regarding step arrangement or operational flow; simple meaning derived from grammatical organization or punctuation; and the number or type of aspects described in the specification.

[0040] All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and / or materials associated with the cited publications.

[0041] Definitions It should also 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 the specification and claims, the term "comprising" can encompass aspects of "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 pertains. In this specification and the subsequent claims, reference will be made to a number of terms defined herein.

[0042] As used in the specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" include plural referents. Thus, for example, reference to "a polypropylene polymer" includes mixtures of two or more polypropylene polymers.

[0043] As used herein, the term "combination" includes blends, mixtures, alloys, reaction products, and the like.

[0044] Ranges may be expressed herein as from one value (the first value) to another value (the second value). When such a range is expressed, in some aspects the range includes one or both of the first and second values. Similarly, when values are expressed as approximations by use of the antecedent "about", it is to be understood that the particular value forms another aspect. It is further to be understood that each end point of a range is significant with respect to the other end point and independent of the other end point. It is also to be understood that many values are disclosed herein, and each value is also disclosed herein 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 to be understood that each unit between two particular units is also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0045] As used herein, the terms "about" and "at or about" mean that the quantity or value being referred to can be the specified value, an approximation of the specified value, or about the same as the specified value. In general, it is to be understood that, as used herein, unless otherwise indicated or inferred, a nominal value indicates a variation of ±10%. The terms are intended to express similar values that promote equivalent results or effects as recited in the claims. That is, it is to be understood that quantities, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller as desired, reflecting tolerances, conversion factors, rounding, measurement error, and other factors known to those of skill in the art. In general, a quantity, size, formulation, parameter, or other quantity or characteristic is "about" or "approximate" whether or not expressly stated as such. It is to be understood that, where a "about" is used in front of a quantitative value, the parameter also includes the specific quantitative value itself unless otherwise specifically stated.

[0046] Components for preparing the compositions of the present disclosure and the compositions themselves used in the disclosed methods are disclosed. These materials and other materials are disclosed herein, and it should be understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed, although specific references to each individual and collective combination and permutation of these compounds are not explicitly disclosed, each combination and permutation is specifically contemplated and described herein. By way of example, if a particular compound is disclosed and discussed, and various modifications that may be made to a plurality of molecules containing the compound are discussed, then each combination and permutation of the compound and the possible modifications are specifically contemplated unless specifically stated to the contrary. Thus, if a class of molecules A, B, and C and a class of molecules D, E, and F are disclosed, and an example of the combination molecule A-D is disclosed, then each molecule is considered individually and collectively, even if each is not separately recited, which means that the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are considered disclosed. Similarly, any subset or combination of these combinations 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 the present application, including but not limited to the steps in the methods of preparing and using the compositions of the present disclosure. Thus, if there are a variety of additional steps that can be performed, it should be understood that each of these additional steps can be performed using any particular aspect or combination of aspects of the methods of the present disclosure.

[0047] References in the specification and concluding claims to the weight portions of a particular element or component in a composition or article denote the weight relationship between the element or component in the composition or article and any other element or component, expressed as weight portions. Thus, in a compound containing 2 weight portions of component X and 5 weight portions of component Y, X and Y are present in a weight ratio of 2:5 and are present in such ratio regardless of whether other components are present in the compound.

[0048] As used herein, unless otherwise specified, the terms “weight percent,” “wt%,” and “wt.%,” which are used interchangeably, denote the weight percentage of a given component based on the total weight of the composition. That is, unless otherwise specified, all wt% values are based on the total weight of the composition. It should be understood that the sum of the wt% values of all components in the disclosed composition or formulation equals 100.

[0049] Unless otherwise stated to the contrary herein, all test standards are the latest standards in effect at the time of filing this application.

[0050] Each raw material used in the examples and / or comparative compositions described herein is commercially available and / or its method of manufacture is known to those skilled in the art.

[0051] It should be understood that the compositions disclosed herein have certain functions. Certain structural requirements for performing the disclosed functions are disclosed herein, and it should be understood that there are various structures that can perform the same functions associated with the disclosed structures, and these structures will generally achieve the same results.

[0052] Thermoplastic composition Aspects of the present disclosure relate to a composition or article comprising a thermoplastic resin, wherein the thermoplastic resin comprises: a polypropylene polymer; and from about 0.15 wt% to about 4.75 wt% of a filler comprising carbon nanotubes. The carbon nanotubes have an average diameter of about 5 to 15 nanometers (nm), a surface area of at least about 100 square meters per gram (m 2 / gr), and a volume resistivity of 10 -3 Ohm·cm or less. When measured according to ASTM D257, the composition exhibits a volume resistivity between 2.0E+14 Ohm·cm and 1.0E+03 Ohm·cm. When observed according to the free space method at a frequency of about 75 GHz to about 110 GHz, a molded sample of the composition having a thickness of about 3.1 millimeters (mm) to about 3.3 mm exhibits an absorption power percentage of at least 65% measured in the transmission mode. The combined weight percentage values of all components do not exceed 100 wt%, and all weight percentage values are based on the total weight of the composition.

[0053] As used herein, "polypropylene" may be used interchangeably with poly(propylene). The polypropylene polymer may comprise a polypropylene homopolymer, a polypropylene copolymer, or a combination thereof. In some aspects, the composition comprises from about 40 wt% to about 90 wt% of the polypropylene polymer. In other aspects, the composition comprises from about 40 wt% to about 85 wt%, or from about 40 wt% to about 80 wt%, or from about 40 wt% to about 75 wt%, or from about 40 wt% to about 70 wt%, or from about 40 wt% to about 65 wt%, or from about 45 wt% to about 90 wt%, or from about 45 wt% to about 85 wt%, or from about 45 wt% to about 80 wt%, or from about 45 wt% to about 75 wt%, or from about 45 wt% to about 70 wt%, or from about 45 wt% to about 65 wt%, or from about 50 wt% to about 90 wt%, or from about 50 wt% to about 85 wt%, or from about 50 wt% to about 80 wt%, or from about 50 wt% to about 75 wt%, or from about 50 wt% to about 70 wt%, or from about 50 wt% to about 65 wt% of the polypropylene polymer.

[0054] In some aspects, the carbon nanotubes are included in the composition in the form of a polypropylene-based masterbatch. In certain aspects, the carbon nanotube content of the polypropylene-based masterbatch is from about 15 wt% to about 25 wt%. In other aspects, the carbon nanotube content of the polypropylene-based masterbatch is from about 18 wt% to about 22 wt%, or from about 19 wt% to about 21 wt%, or about 20 wt%. In a particular aspect, the composition comprises from about 0.6 wt% to about 2.75 wt% of carbon nanotubes. In a particular aspect, when observed at a frequency of 77 GHz, the percentage of absorbed power measured in the transmission mode for a composition containing such a carbon nanotube content is at least 80%.

[0055] In some aspects, the composition further comprises a reinforcing filler. The reinforcing filler can include but is not limited to glass fiber, glass beads, glass flakes, flake silicon carbide, ceramic fiber, calcium carbonate, kaolin, mica, clay, talc, feldspar, sillimanite (fillite), quartz, quartzite, perlite, tripoli, diatomaceous earth or combinations thereof.

[0056] In some aspects, the composition does not contain a conductive filler, such as but not limited to metal fiber or carbon fiber, as it would have a negative impact on the microwave absorption properties of the material. The reinforcing filler, if included, can be selected such that it does not adversely affect the microwave (MW) interference properties (absorption, transmission, reflection) provided by the CNTs included in the composition according to aspects of the present disclosure. For example, glass fiber is mostly transparent to MW radiation (minimal absorption and reflection). Thus, in a particular aspect, the reinforcing filler comprises glass fiber.

[0057] In certain aspects, the composition comprises from about 5 wt% to about 50 wt% of the reinforcing filler. In other aspects, the amount of the reinforcing filler present is from 5 wt% to about 45 wt%, or from 5 wt% to about 40 wt%, or from 5 wt% to about 35 wt%, or from 5 wt% to about 30 wt%, or from 5 wt% to about 25 wt%, or from 10 wt% to about 50 wt%, or from 10 wt% to about 45 wt%, or from 10 wt% to about 40 wt%, or from 10 wt% to about 30 wt%, or from 10 wt% to about 25 wt%, or from 15 wt% to about 50 wt%, or from 15 wt% to about 45 wt%, or from 15 wt% to about 40 wt%, or from 15 wt% to about 35 wt%, or from 15 wt% to about 30 wt%, or from 15 wt% to about 25 wt%, or about 20 wt%.

[0058] In some aspects, the composition further comprises a polycarbonate polymer. The polycarbonate polymer may comprise a polycarbonate homopolymer, a polycarbonate copolymer, or a combination thereof. In certain aspects, the polycarbonate polymer comprises a polycarbonate-siloxane copolymer having a siloxane content of from about 5 wt% to about 45 wt%. In other aspects, the siloxane content of the polycarbonate-siloxane copolymer is from about 4 - 8 wt% (e.g., transparent EXL from Sabic, having a siloxane content of about 6 wt%), from about 18 - 22 wt% (e.g., opaque EXL from Sabic, having a siloxane content of about 20 wt%), and / or from about 35 - 45 wt% (such as a 40 wt% siloxane copolymer from Sabic). The composition comprising a polycarbonate-siloxane copolymer according to aspects of the present disclosure may have a total siloxane content of from about 2 wt% to about 10 wt%.

[0059] In certain aspects, the composition comprises from about 5 wt% to about 30 wt% of the polycarbonate polymer. In other aspects, the polycarbonate polymer is present in the composition in an amount of from about 5 wt% to about 25 wt%, or from about 5 wt% to about 20 wt%, or from about 10 wt% to about 30 wt%, or from about 10 wt% to about 25 wt%, or from about 10 wt% to about 20 wt%, or about 15 wt%.

[0060] In certain aspects where the composition comprises a polycarbonate-siloxane copolymer as described above, the notched Izod impact strength of the composition at -30 °C can be at least 40 joules per meter (J / m) or the unnotched Izod impact strength at -30 °C is at least 165 J / m, wherein the Izod impact strength is tested according to ASTM D256 and ASTM D4812. In other aspects, the notched Izod impact strength of the composition at -30 °C is from 40 to 100 J / m, or from 40 to 90 J / , or from 40 to 80 J / m, or from 40 to 70 J / m, or from 40 to 60 J / m. In other aspects, the unnotched Izod impact strength of the composition at -30 °C is from 165 to 220 J / m, or from 165 to 210 J / m, or from 165 to 200 J / m, or from 165 to 190 J / m, or from 165 to 185 J / m.

[0061] Manufacturing method One or any of the foregoing components described herein can be dry blended with each other first, or with any combination of the foregoing components, and then fed into an extruder from one feeder or multiple feeders, or separately fed into an extruder from one feeder or multiple feeders. The fillers used in this disclosure can also be processed into masterbatches first and then fed into the extruder. The components can be fed into the extruder from a throat hopper or any side feeder.

[0062] The extruders used in this disclosure can have single screws, multiple screws, intermeshing co-rotating or counter-rotating screws, non-intermeshing co-rotating or counter-rotating screws, reciprocating screws, screws with pins, screws with sieves, barrels with pins, rollers, pistons, helical rotors, co-kneaders, disc-pack processors, various other types of extrusion equipment, or combinations comprising at least one of the foregoing components.

[0063] The components can also be mixed together and then melt blended to form a thermoplastic composition. The melt blending of the components involves the use of shear forces, tensile forces, compressive forces, ultrasonic energy, electromagnetic energy, thermal energy, or combinations comprising at least one of the foregoing force or energy forms.

[0064] If the resin is a semi-crystalline organic polymer, the barrel temperature on the extruder during compounding can be set at a temperature at which at least a portion of the polymer has reached a temperature greater than or equal to about the melting temperature, or if the resin is an amorphous resin, the barrel temperature can be set at the flow point (e.g., glass transition temperature).

[0065] If desired, the mixture comprising the foregoing components can undergo multiple blending and shaping steps. For example, the thermoplastic composition can be first extruded and shaped into pellets. The pellets can then be fed into a molding machine, where the pellets can be molded into any desired shape or product. Alternatively, the thermoplastic composition produced from a single melt blender can be shaped into sheets or strands and undergo post-extrusion processes such as annealing, uniaxial or biaxial orientation.

[0066] In some aspects, the temperature of the melt in this method can be kept as low as possible to avoid excessive thermal degradation of the components. In certain aspects, the melting temperature is kept between about 210 °C and about 290 °C, but higher temperatures can be used provided that the residence time of the resin in the processing equipment remains relatively short. In some aspects, the melt-processed composition exits the processing equipment, such as an extruder, through small exit holes in a die. The resulting molten resin strands can be cooled by passing the strands through a water bath. The cooled strands can be cut into pellets for packaging and further processing.

[0067] Article In some aspects, the present disclosure relates to formed, shaped, or molded articles comprising a thermoplastic composition. The thermoplastic composition can be molded into useful formed articles in a variety of ways, such as injection molding, extrusion, compression molding, rotational molding, blow molding, and thermoforming, to form articles and structural components such as radar sensors, cameras, electronic control units (ECUs), support brackets, or radar housings. In another aspect, the article is extrusion molded. In yet another aspect, the article is injection molded.

[0068] Exemplary articles further comprise surface features for providing high levels of microwave absorption (>85%) and low levels of microwave reflection (<2% or so) in radar sensors or other similar applications as required for the article. The surface appearance of the molded part can be altered to increase the absorption of microwave (MW) radiation and reduce the reflection of microwave radiation. Two-dimensional and three-dimensional features can be provided that are molded or imprinted on the surface of the part (e.g., an internal radar component or an external radar housing) to capture more incident microwave radiation, whereby the reflection of the surface can be minimized. Features such as wedges, pyramids, cones, or many other geometric 2D or 3D shapes added to the surface of the molded part act as microwave radiation receivers to block electromagnetic waves by forcing the electromagnetic waves to bounce back when they strike the features, causing the waves to lose energy with each bounce, thereby reducing reflection and increasing absorption according to the anechoic chamber principle. These features have a specific geometric design to allow the effective suppression of electromagnetic waves when they strike the part, thereby promoting the dissipation of the energy contained in the dissipated waves, thus enhancing absorption and reducing reflection. For example, 2D features such as long triangular wedges with a height / base ratio of 2:1 to 10:1 or in a particular aspect of about 5:1 can provide certain materials that have an absorption power percentage higher than 85% and a reflection power percentage lower than about 6% when tested at 77 GHz frequency. In some cases, a carbon-filled polymeric resin can be formed that absorbs at least 90% of the incident microwave radiation and reflects less than 1% of the incident microwave radiation when observed at 77 GHz frequency on a 1 / 8-inch nominal thickness plate.

[0069] It will be appreciated that the molded features can be incorporated on the surface of the part during part formation (i.e., formed continuously with the part), or they can be molded (or imprinted) separately on an already formed part.

[0070] Other aspects of the disclosure include components of an automotive radar sensor (e.g., a board, a housing, and a cover) molded from a material comprising a polymer and carbon black powder as a microwave absorbing filler. The molded component has improved microwave absorption characteristics, including microwave absorption efficiency, absorption bandwidth, shielding effectiveness, attenuation, and electrical surface resistivity and volume resistivity. In certain aspects, the molded component includes micron-scale features that can capture additional microwave radiation compared to a component molded from the same composition that does not include micron-scale features.

[0071] Another aspect includes an article, such as but not limited to a radar sensor, a camera, an electronic control unit (ECU), a support bracket, a radar housing, that includes a molded component made of a microwave absorbing material (absorber) and having at least two openings to allow microwave radiation to be transmitted between a transmit antenna and a receive antenna located in a printed circuit board of the sensor.

[0072] In a particular aspect, the article includes a molded board that includes a surface having micron-scale features, where a region of the molded board having a thickness of about 2.7 mm to about 2.9 mm and including micron-scale features exhibits a percentage of absorbed power measured in the transmit mode of at least 85% and a percentage of reflected power measured in the transmit mode of 2% or less when observed according to the free space method at a frequency of about 75 GHz to 110 GHz. The micron-scale features have a high-to-bottom ratio between 2:1 and 10:1.

[0073] In some aspects, a 6" (inch) × 8" × 1 / 8" sample of the molded board (where at least one square inch (1.0 in 2 ) of the surface area of the sample includes micron-scale features) has the indicated absorbed power and reflected power characteristics. In other aspects, the molded board includes micron-scale features on at least 1.5 in 2 、 or at least 2.0 in 2 、 or at least 2.5 in 2 、 or at least 3.0 in 2 、 or at least 3.5 in 2 、 or at least 4.0 in 2 、 or at least 4.5 in 2 、 or at least 5.0 in 2 、 or at least 6.0 in 2 、 or at least 7.0 in 2 、 or at least 8.0 in 2 of the sample surface area. In a particular aspect, the molded board includes micron-scale features on a sample surface area of 3.5 in 2 to 4.5 in 2 、 or about 4 in 2 of the sample surface area.

[0074] In some aspects, the micron-scale features are two-dimensional or three-dimensional in a linear direction. In certain aspects, the aspect ratio of the micron-scale features is between 3:1 and 9:1, or 3:1 and 8:1, or 3:1 and 7:1, or 3:1 and 6:1, or 4:1 and 9:1, or 4:1 and 8:1, or 4:1 and 7:1, or 4:1 and 6:1, or about 5:1.

[0075] In other aspects, neither the base nor the height of the micron-scale features has a dimension greater than 3000 micrometers (µm). In certain aspects, neither the base nor the height of the micron-scale features 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 recognized that if the feature is two-dimensional in a linear direction, then the linear direction can have a length greater than 1000 micrometers. See, for example Figure 16B and 17A . It will also be recognized that the thickness of the plate / article / component containing the feature is independent of the size of the feature; for example, while a thicker plate / article / component may typically contain larger features, this is not necessarily the case.

[0076] In some aspects, an article containing micron-scale features contains a thermoplastic resin according to any aspect described herein, and in particular contains a polypropylene polymer and a filler containing carbon nanotubes in an amount of about 0.15 wt% to about 4.75 wt%. In certain aspects, a molded plate contains a polypropylene polymer and a filler containing carbon nanotubes in an amount of about 0.15 wt% to about 4.75 wt%, wherein the carbon nanotubes have an average diameter of about 5 to 15 nm, a surface area of at least about 100 m 2 / gr and a volume resistivity of 10 -3 Ohm.cm or less.

[0077] The present disclosure encompasses various combinations of the elements of the present disclosure, such as combinations of elements from dependent claims that are attached to the same independent claim.

[0078] Aspects of the present disclosure In various aspects, the present disclosure relates to and at least includes the following aspects.

[0079] Aspect 1. A composition comprising a thermoplastic resin, wherein the thermoplastic resin comprises, consists of, or consists essentially of: a polypropylene polymer; and From about 0.15 wt% to about 4.75 wt% of a filler comprising carbon nanotubes, wherein the carbon nanotubes have an average diameter of about 5 to 15 nanometers (nm), a surface area of at least about 100 square meters per gram (m 2 / gr), and a volume resistivity of 10 -3 Ohm·centimeters (Ohm.cm) or less, wherein when measured according to ASTM D257, the composition exhibits a volume resistivity between 2.0E+14 Ohm.cm and 1.0E+03 Ohm.cm, wherein when observed according to the free space method at a frequency of about 75 GHz to about 110 GHz, a molded sample of the composition having a thickness of about 3.1 millimeters (mm) to about 3.3 mm exhibits an absorption power percentage measured in the transmission mode of at least 65%, and wherein the combined weight percentage values of all components do not exceed 100 wt%, and all weight percentage values are based on the total weight of the composition.

[0080] In some aspects, the thickness of the molded sample is 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.

[0081] Aspect 2. The composition according to aspect 1, wherein the composition comprises from about 0.6 wt% to about 2.75 wt% of the carbon nanotubes, and wherein when observed at a frequency of 77 GHz, the absorption power percentage measured in the transmission mode is at least 80%.

[0082] Aspect 3. The composition according to aspect 1 or 2, wherein the polypropylene polymer comprises a polypropylene homopolymer, a polypropylene copolymer, or a combination thereof.

[0083] Aspect 4. The composition according to any one of aspects 1 to 3, wherein the carbon nanotubes are in the form of a polypropylene-based masterbatch.

[0084] Aspect 5. The composition according to aspect 4, wherein the polypropylene-based masterbatch has a carbon nanotube content of from about 15 wt% to about 25 wt%.

[0085] Aspect 6. The composition according to any one of Aspects 1 to 5, wherein the composition further comprises a reinforcing filler.

[0086] Aspect 7. The composition according to Aspect 6, wherein the reinforcing filler comprises glass fibers.

[0087] Aspect 8. The composition according to any one of Aspects 1 to 7, wherein the composition further comprises a polycarbonate polymer.

[0088] Aspect 9. The composition according to Aspect 8, wherein the polycarbonate polymer comprises a polycarbonate-siloxane copolymer having a siloxane content of from about 5 wt% to about 45 wt%.

[0089] Aspect 10. The composition according to Aspect 9, 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.

[0090] Aspect 11. An article comprising the composition according to any one of Aspects 1 to 10.

[0091] Aspect 12. The article according to Aspect 11, wherein the article is a component of an automotive radar sensor.

[0092] Aspect 13. An article comprising, consisting of, or consisting essentially of a molded panel, the molded panel comprising a surface having micron-scale features, wherein a region of the molded panel having a thickness of from about 2.7 mm to about 2.9 mm and comprising the micron-scale features exhibits a percentage of absorbed power measured in transmission mode of at least 85% and a percentage of reflected power measured in transmission mode of 2% or less when observed according to the free space method at a frequency of from about 75 GHz to 110 GHz, and wherein the micron-scale features have a high-to-bottom ratio between 2:1 and 10:1.

[0093] In some aspects, the thickness of the region of the molding plate is 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.

[0094] Aspect 14. The article according to aspect 13, wherein the micron-scale feature is two-dimensional or three-dimensional in a linear direction.

[0095] Aspect 15. The article according to aspect 13 or 14, wherein the micron-scale feature has an aspect ratio between 4:1 and 6:1.

[0096] Aspect 16. The article according to any one of aspects 13 to 15, wherein the polygon is a triangle.

[0097] Aspect 17. The article according to any one of aspects 13 to 16, wherein neither the base nor the height of the micron-scale feature has a dimension greater than 1000 micrometers (μm).

[0098] Aspect 18. The article according to any one of aspects 13 to 17, wherein the molding plate comprises the composition according to any one of aspects 1 to 10.

[0099] Aspect 19. The article according to any one of aspects 13 to 17, wherein the molding plate comprises a polypropylene polymer and from about 0.15 wt% to about 4.75 wt% of a filler comprising carbon nanotubes, wherein the carbon nanotubes have an average diameter of about 5 to 15 nm, a surface area of at least about 100 m 2 / gr and a volume resistivity of 10 -3 Ohm.cm or less.

[0100] Examples The following examples are presented to provide a complete disclosure and description to one of ordinary skill in the art of how to make and evaluate the compounds, compositions, articles, devices, and / or methods claimed herein, and are intended to be purely exemplary and not intended to limit the disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some error and deviation should be accounted for. Unless otherwise indicated, parts are parts by weight, temperature is in °C or at ambient temperature, and pressure is at or near atmospheric pressure. Unless otherwise indicated, percentages with respect to compositions are by wt%.

[0101] There are many reaction condition variations and combinations, such as component concentrations, desired solvents, solvent mixtures, temperature, pressure, and other reaction ranges and conditions that can be used to optimize the purity and yield of the products obtained from the described processes. Only reasonable and routine experimentation will be required to optimize such process conditions.

[0102] Example 1 - Composition Compositions formed in accordance with aspects of the present disclosure include one or more of the components listed in Table 1: Table 1 - Components Component Description Source PD702 PP <![CDATA[Pro-fax PD702 polypropylene homopolymer, MFR 35 g / 10 min (230 °C, 2.16 kg) (ASTM D1238), density 0.9 g / cm 3 (ASTM D792)]]> LyondellBasell CNT MB Plasticyl™ PP2001 PP masterbatch, 20 wt% NC7000 carbon nanotubes Nanocyl GF StarStran® JM738 glass fiber, 14 µm fiber diameter (ISO 1888), 738 sizing, 4 mm length, E - glass JohnsManville PC - Si Lexan™ EXL, polycarbonate - siloxane copolymer, 20 wt% siloxane Sabic Prepare example and comparative compositions as shown in Table 2, amounts are in wt% unless otherwise indicated: Table 2 - Example and Comparative PP / CNT Compositions Evaluate certain mechanical properties of the Table 2 compositions; the results are shown in Table 3: Table 3 - Mechanical Properties of the Table 2 Compositions Graphical representations of some of the results are included in Figures 1A to 3 and Figure 1A and 1B show the notched and unnotched cantilever impact properties at 23 °C and -30 °C, respectively. The surface and volume resistivity are shown in Figure 2 The melt flow rate is shown in Figure 3 and

[0103] It is observed from the data and schematics that the cantilever impact strength of these materials remains almost unchanged when tested at room temperature (23 °C) or low temperature (-30 °C), which may be attributed to the presence of polycarbonate-siloxane copolymer in these formulations. Figure 2 shows that electroosmotic flow appears to start at a carbon nanotube concentration of about 1 wt%. Figure 3 shows that as the concentration of carbon nanotubes in the formulation increases from about 0.1 wt% to 5 wt%, the viscosity of these materials also increases (MFR decreases).

[0104] The dielectric properties of the compositions described herein can be evaluated according to the free space method. The free space method comprises a vector network analyzer, two antennas facing each other, and a sample holder placed equidistantly therebetween. The basic experimental quantities generated by the free space method are called scattering parameters or S-parameters, which are used to describe the input-output relationship between different ports of an electrical network in terms of amplitude and phase versus frequency. The S-parameters are usually identified by two numerical subscripts, where the first number in the subscript refers to the response port and the second number refers to the incident port. Thus, S21 means the response at port 2 due to the signal at port 1. The scattering parameters are complex numbers with real and imaginary parts, and they describe the amount of microwave radiation reflected from or transmitted through the sample. For example, the reflection scattering parameter S11 represents the signal that originates from antenna 1 and is received back and reflected at the same antenna after being incident on the sample. Similarly, the transmission scattering parameter S21 represents the signal that originates from antenna 1 and is received by antenna 2 after transmission through the material under test. Scattering parameters can also be defined for transmission and reflection representing signals originating from antenna 2, with reflection being S22 and transmission being S12. The reflection coefficients and transmission gains on both sides of a two-port network can be determined using the S-parameter matrix, for which the four S-parameters S11, S22, S21, and S12 are identified as defined above. The scattering parameter output of the network analyzer is then converted to dielectric properties using software. The free space measurement technique provides a method for determining the dielectric constant and permeability of the magnetodielectric material under test. These methods are non-contact, that is, the material under test does not come into direct contact with any active components of the equipment involved in the measurement.

[0105] Figure 4A and 4B Schematic diagrams of equipment for using the free space method to determine the dielectric properties of the materials of the present disclosure for non-backed samples and metal-backed samples are shown in [[ID=]] and respectively. Injection molded plates of 6 inches × 8 inches × 1 / 8 inch size are used for these free space dielectric measurements.

[0106] Dielectric measurements using the free-space method can be performed in two different modes (transmission mode and metal-backed reflection mode). The transmission measurement mode measures three types of radiation: that absorbed into the sample; that reflected from the sample; and that transmitted through the sample. In the metal-backed reflection measurement mode, a metal plate (stainless steel, aluminum, etc.) is placed between the material under test and the receiving antenna, thus completely suppressing transmission through the sample, and only the microwave absorption of the material and the microwave reflection of the material can be evaluated. Since in the transmission mode the combination of the two antennas can only measure the scattered parameter S11 of reflection and the scattered parameter S21 of transmission, the amount of radiation absorbed by the material under test (in percentage) is calculated as the difference between the total energy incident on the sample (or 100%) and the sum (in percentage) of the radiation transmitted through the sample (measured from S21 and reaching the receiving antenna) and the radiation reflected from the sample (measured from S11 and returning to the transmitting antenna). In many applications, when measurements are made using the transmission mode, it is desirable to maximize the percentage of absorbed power and minimize the percentage of reflected power and the percentage of transmitted power. When selecting materials for microwave radar interference applications, radar designers consider a variety of dielectric properties. The complex dielectric constant (real and imaginary parts), the amount of radiation absorbed, reflected, or transmitted by the material, the shielding effectiveness, the reflection loss, and the attenuation are just some of the material properties that are of concern when manufacturing plastic components for radar sensor applications. The frequency of the incident radiation and the material thickness are also important when capturing microwave energy, and if the microwave energy is not eliminated or minimized, it will interfere with the normal operation of automotive electronic sensors.

[0107] The dielectric properties of the compositions in Table 2 were evaluated at frequencies in the W-band (75 to 110 GHz); the results selected at 77 GHz are shown in Table 4: Table 4 - Dielectric Properties of the Compositions in Table 2 (77 GHz) The percentage of power (reflected, absorbed, and transmitted) in the transmission mode at 77 GHz is shown graphically in Figure 5 . It is observed from the data in Table 4 and Figure 5 that as the concentration of carbon nanotubes in the formulation increases and the material becomes more and more conductive, the percentage of reflected power in the transmission mode mostly increases and the percentage of transmitted power in the transmission mode decreases. The percentage of absorbed power in the transmission mode first increases from about 33% to about 76% at low concentrations of carbon nanotubes and then decreases from about 71% to about 63%, reaching a maximum of about 81% at about 1 wt% of carbon nanotubes.

[0108] The dielectric properties of the compositions in Table 2 over the full W-band (75 to 110 GHz) are shown graphically in Figures 6A to 10 . Figures 6A to 6C The real part of the complex dielectric constant, the imaginary part of the complex dielectric constant, and the attenuation constant are shown respectively.Figure 7 Shows the total shielding effectiveness, Figure 8 Shows the percentage of absorbed power in the transmission mode, Figure 9 Shows the percentage of absorbed power in the metal-backed reflection mode, and Figure 10 Shows the power percentages (absorbed, reflected, and transmitted) of Composition Ex1.3 in the transmission mode. It is observed from these figures that for all the studied frequencies, as the concentration of carbon nanotubes in the composition increases, both the real and imaginary parts of the complex dielectric constant increase. The same observations can be made for the attenuation constant (becoming more negative) and the total shielding effectiveness (becoming more positive). Figure 8 Shows that when the frequency of the incident radiation increases from 75 to 110 GHz, the percentage of absorbed power in the transmission mode remains fairly constant. Figure 9 Shows that for certain frequencies and compositions, the percentage of absorbed power in the metal-backed reflection mode can reach values higher than 80% because more of the radiation incident on the metal plate behind the sample under test is reflected back and re-absorbed into the material. Figure 10 Shows that for all the studied frequencies, a 3.3-mm thick sample of Composition Ex1.3 can absorb more than 80% and reflect less than 20%.

[0109] Example 2 - Articles Containing Micron-Scale Features Articles formed in accordance with aspects of the present disclosure contain one or more of the components listed in Table 5: Table 5 - Components Component Description Source PD702 PP <![CDATA[Pro-fax PD702 polypropylene homopolymer, MFR 35 g / 10 min (230 °C, 2.16 kg) (ASTM D1238), density 0.9 g / cm 3 (ASTM D792)]]> LyondellBasell CB <![CDATA[Ensaco® 360G carbon black, electrically conductive, highly branched, 770 m 2 / g (ASTM D3037), OAN absorption 320 ml / 100g (ASTM D2414)]]> Imerys GF StarStran® JM738 glass fiber, 14 µm fiber diameter (ISO 1888), 738 sizing, 4 mm length, E - glass JohnsManville Compositions based on thermoplastic PP are prepared as shown in Table 6, unless otherwise indicated, the amounts are in wt%: Table 6 - PP / CB Compositions Contain carbon powder (carbon black) to impart conductivity and microwave interference properties to the composition. Certain mechanical properties of Compositions Ex2.3 and Ex2.4 are evaluated; the results are shown in Table 7: Table 7 - Mechanical Properties of the Compositions in Table 6 It is observed from the data in Table 7 that when the concentration of carbon powder in the formulation increases from 4 wt% to 10 wt%, both the specific gravity and the melt viscosity increase, and the surface / volume resistivity and the MFR decrease.

[0110] The dielectric properties of the compositions in Table 6 are evaluated at frequencies in the W band (75 to 110 GHz); the selected results at 77 GHz are shown in Table 8: Table 8 - Dielectric Properties of the Compositions in Table 6 (77 GHz) The percentage of power in the transmission mode (reflection, absorption, and transmission) at 77 GHz is shown graphically in Figure 11 . As shown in Table 8, these materials can absorb from about 69% to about 78% of the incident microwave radiation at 77 GHz, where the amount of energy reflected by these compositions at 77 GHz ranges from about 13% to 31%.

[0111] Table 6 The dielectric properties of the compositions in the full W-band (75 to 110 GHz) are shown graphically in Figures 12A to 15B . Figures 12A to 12C The real part of the complex dielectric constant, the imaginary part of the complex dielectric constant, and the attenuation constant are shown respectively. Figure 13 The total shielding effectiveness is shown, Figure 14 the percentage of absorbed power in the transmission mode is shown, and Figure 15A and 15B show the percentage of power in the transmission mode and the percentage of power in the metal-backed reflection mode (absorption, reflection, and transmission) of Composition Ex2.3 observed on a 3.1-mm thick sample, respectively. It is observed from these figures that for all the studied frequencies, as the concentration of carbon black powder in the composition increases, both the real and imaginary parts of the complex dielectric constant increase. The same observations can be made for the attenuation constant (becoming more negative) and the total shielding effectiveness (becoming more positive). Figure 14 shows that as the frequency of the incident radiation increases from 75 to 110 GHz, the percentage of absorbed power in the transmission mode remains fairly constant. Figure 15A and 15B show that the percentage of power in the transmission mode and the metal-backed reflection mode are similar, which can be explained by the fact that for all the studied frequencies, the samples measured in the transmission mode show very low transmission.

[0112] In some applications, the above levels of microwave absorption and reflection may not be sufficient to capture the incident electromagnetic radiation, which may interfere with the normal operation of automotive radar sensors if not eliminated or minimized. These applications typically require a combined microwave absorption level of 85% or higher and a microwave reflection level of about 2% or lower. Through careful experiments, two-dimensional features are laser-embossed on the surface of a relatively smooth injection-molded part. It is observed that these features contribute to an increase in microwave absorption and a decrease in microwave reflection when compared to a smooth molded part of the same composition without these features. These geometric features are embossed in the form of two-dimensional triangular wedges with a base of about 100 micrometers (µm), a height of about 500 µm, and a length of 2 inches (in), and there is no gap between consecutive rows of these arranged features. Sketches of the 2D front and side perspectives of the geometric features are shown respectively in Figure 16A and 16B .

[0113] It is hypothesized that these features serve to block incident electromagnetic waves by forcing them to bounce back and forth between adjacent wedges after impinging on the surface of the component, causing the waves to lose energy with each bounce, thereby reducing reflection and increasing absorption according to anechoic chamber principles. These features are laser imprinted in a 2 in × 2 in square area at the center of a 6 in × 8 in rectangular plate. The dielectric properties of this pattern are tested in the W-band (75 to 110 GHz frequencies) using a vector network analyzer. Figure 17A and 17B are micrographs showing a top view and a cross-sectional view, respectively, of 2D triangular wedges imprinted on the surface of a smooth molded component using laser mapping techniques. In some aspects, the features can be molded on the surface of the smooth molded component.

[0114] More specifically, the geometric features imprinted on the surface of the molded plate of Example 2 are in the form of two-dimensional triangular wedges having a base of approximately 100 microns, a height of approximately 500 microns, and a length of 2 inches, with no gaps between consecutive rows of these arranged features. Thus, the height-to-base ratio of the micron-scale features is 5:1 (500 µm height and 100 µm base), which is between 2:1 and 10:1. The length of the wedge (2 inches in this case) is irrelevant to the determination of the height-to-base ratio.

[0115] Similarly, three-dimensional features in the form of pyramids, cones, etc. can also be imprinted or molded on the surface of a smooth molded component to even further enhance the microwave absorption / reflection effects observed in these materials. Exemplary three-dimensional images are shown in Figures 18A to 18C In. Further exemplary three-dimensional features are shown in Figure 23A and 23B In. The three-dimensional features can include, for example, a base having a triangular, square, rectangular, pentagonal, or hexagonal cross-section as shown in Figure 23A In, or a circular cross-section as shown in Figure 23B In.

[0116] 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 having a shape as shown in Figure 23A In (such as a pyramid), or the height of a conical feature as shown in Figure 23B In) to the length of the base of the feature (e.g., the length at the base of the pyramid or cone).

[0117] The 2D features described above are imprinted on plates of several compositions, and their dielectric properties are evaluated and compared to those of plates of the same composition without the features. The imprinted plates are tested in transmission mode and metal-backed reflection mode using the devices depicted in Figure 19A and 19B In, respectively.

[0118] The dielectric properties of the imprinted composition Ex2.3 in the W-band (75 to 110 GHz) are shown graphically in Figure 20A and 20B . Specifically, the percentage of power in the transmission mode is shown in Figure 20A , and the percentage of power in the metal-backed reflection mode is shown in Figure 20B . It is observed from Figure 20A that in the transmission mode, the absorption is at least 89% across the entire W-band, and the reflection is 1% or less across the entire band. It is observed from Figure 20B that in the metal-backed reflection mode, the absorption is at least 97% across the entire W-band, and the reflection is 3% or less across the entire band.

[0119] Example 3 - Comparison with Conventional Carbon Black Compositions Some conventional radar absorbing compositions containing Ensaco® 360 G carbon black are shown in Table 9: Table 9 - Conventional Carbon Black Compositions These conventional compositions were purchased from Sabic. As shown in Figure 21 , they all have similar dielectric properties at 77 GHz, with approximately 65% absorption and approximately 35% reflection, and essentially no transmission.

[0120] Additional conventional compositions containing carbon (Ensaco® 360G CB or carbon nanotubes (CNT)) are listed in Table 10: Table 10 - Conventional Carbon Compositions Plates of compositions C3.6 to C3.9 with and without the 2D features described above were prepared, and their dielectric properties were evaluated at 77 GHz and compared with the example composition Ex2.3 of Example 2 above. The results are shown in Table 11: Table 11 - Dielectric Properties of Table 10 Compositions and Ex2.3 at 77 GHz Composition Reflected power % Transmitted power % Absorbed power % Sample thickness (mm) Ex2.3 17.42 5.04 77.54 3.115 Ex2.3(I) 0.88 9.37 89.75 2.788 C3.6 35.10 0.00 64.89 2.344 C3.6(I) 17.01 0.01 82.98 2.313 C3.7 19.94 3.14 76.92 2.884 C3.7(I) 5.37 6.22 88.41 2.84 C3.8 18.66 5.00 76.34 3.077 C3.8(I) 4.86 7.79 87.35 3.03 C3.9 19.23 4.11 76.66 3.132 C3.9(I) 6.90 7.80 85.30 2.883 The imprinted plates are marked with "(I)". The results are shown graphically in Figure 22Among them. It is observed from the data that when a 2D triangular wedge is added to the surface of the component, all the compositions show an increase in microwave absorption and a decrease in microwave reflection. Depending on the composition, the improvement in the absorption percentage ranges from 9 percentage points to 18 percentage points. Specifically, it is observed that when observed at a frequency of 77 GHz, the example composition Ex2.3 can achieve a combined effect of at least 85% microwave absorption and less than 2% reflection. The compositions C3.6 to C3.9 fail to reach the absorption threshold of 85% or the reflection threshold of <2%. These results also show that the effect of adding micron-sized features to the surface of the molded component is not related to the composition, but rather to the formulation of the material used to mold the test component, thus indicating a synergistic effect between the geometric features and the composition of the test component on which these features are imprinted. The reduction in the reflected power achieved by the presence of the 2D feature varies, for example, from approximately 20:1 in the composition Ex2.3 to approximately 4:1 in the composition C3.8, to only approximately 2:1 in the composition C3.6.

[0121] The above description is intended to be illustrative and not restrictive. For example, the examples described above (or one or more aspects thereof) can be used in combination with each other. Other aspects can be used by those of ordinary skill in the art after reviewing the above description. The abstract is provided to comply with 37 C.F.R.§1.72(b) to allow the reader to quickly determine the nature of the technical disclosure. The abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the above detailed description, various features can be combined together to simplify the disclosure. This should not be construed as requiring that the disclosed features not claimed are essential for any claim. On the contrary, the subject matter of the present invention may have fewer features than all the features of a particular disclosed aspect. Therefore, the appended claims are hereby incorporated into the detailed description as examples or aspects, where each claim stands alone as a separate aspect, and it is expected that these aspects can be combined with each other in various combinations or permutations. The scope of the disclosure should be determined with reference to the appended claims and the full scope of the equivalents thereto.

Claims

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

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

3. The composition according to claim 1 or 2, wherein the carbon nanotubes are in the form of a polypropylene-based masterbatch.

4. The composition according to claim 3, wherein the carbon nanotube content of the polypropylene-based masterbatch is from about 15 wt% to about 25 wt%.

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

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

7. The composition according to 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 according to any one of claims 1 to 7, wherein the article is a component of an automotive radar sensor.

9. An article comprising a molded plate, the molded plate comprising a surface having micron-scale features, wherein when observed according to the free space method at frequencies from about 75 GHz to 110 GHz, a region of the molded plate having a thickness of about 2.7 mm to about 2.9 mm and comprising the micron-scale features exhibits a percentage of absorbed power measured in transmission mode of at least 85% and a percentage of reflected power measured in transmission mode of 2% or less, and wherein the micron-scale features have a height-to-base ratio between 2:1 and 10:

1.

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

11. The article according to claim 9 or 10, wherein the micron-scale feature has an aspect ratio between 4:1 and 6:

1.

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

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

14. The article according to any one of claims 9 to 13, wherein the molding plate comprises the composition according to any one of claims 1 to 7.

15. The article according to any one of claims 9 to 13, wherein the molded plate comprises a polypropylene polymer and a filler comprising carbon nanotubes in an amount of from about 0.15 wt% to about 4.75 wt%, wherein the carbon nanotubes have an average diameter of from about 5 to 15 nm, a surface area of at least about 100 m 2 / gr and a volume resistivity of 10 -3 Ohm.cm or less.

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