Polyester compositions containing carbon nanotubes as microwave absorbers in sensor applications

Abstract

A thermoplastic composition includes: a thermoplastic polymer component including a polyester; and from greater than 0.10 wt% to about 1.95 wt% carbon nanotube (CNT) filler. A 6 in x 8 in x 1 / 8 in molded sample of the composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free space method. In some embodiments, the polyester includes polybutylene terephthalate (PBT). Further embodiments include an article (e.g., radar sensor, camera, electronic control unit, etc.) that includes a molded part that includes a microwave absorbing material (absorber). The article may have at least two openings that allow the transmission of microwave radiation between a transmitting antenna and a receiving antenna located in / on the sensor's printed circuit board.

Description

[Technical Field]

[0001] The present disclosure relates to thermoplastic compositions comprising polyester and carbon nanotube (CNT) fillers suitable for use as microwave absorbers in sensor applications. [Background technology]

[0002] The automotive industry is increasingly using electronic radar sensors to provide driver assistance through features such as distance control, parking / lane change assist, reversing warnings, blind spot detection, collision avoidance, and many other functions. To operate effectively, these sensors must be protected from spurious electromagnetic radiation sources. Automotive radar sensors include a radome-type plastic component that is nearly transparent to microwave radiation and an absorber-type plastic component that captures microwave energy in a specific frequency range to protect the sensor from external radiation interference. These plastic components are typically injection molded using relatively high injection pressures and melt temperatures to form the final part. Microwave-absorbing materials made from carbon black powder, graphite, or carbon fiber typically require a relatively large amount of carbon filler to provide sufficient shielding interference in the K and W bands of the electromagnetic spectrum.

[0003] Electronic radar sensors are used in the automotive industry to assist with operations such as distance control, lane changing, self-parking, and blind spot detection. These sensors must be protected from electromagnetic interference that could impair their proper operation. Metals (aluminum, stainless steel) are the most common materials used for microwave (MW) shielding, but they are heavy, expensive, and require complex processing to form into final parts.

[0004] Polymer / carbon composites are preferred because of their low density, low cost, ease of molding, and the ability to be fabricated into large volume molded parts. The carbon filler traps or deflects MW radiation within the enclosure walls, protecting the electronic sensors within the cavity. Relatively high dielectric constants, electrical conductivities, and large dielectric and magnetic losses are some of the characteristics required for materials used in microwave shielding.

[0005] Microwave radiation (frequencies of approximately 1-300 GHz, wavelengths of approximately 300-1 mm) is the most common EM energy source used to operate radar sensors for automotive applications. Metals (e.g., aluminum and stainless steel), polymer composites containing metal fillers such as aluminum flakes, stainless steel fibers, and silver-coated polyamide fibers, metallized coatings, inherently conductive polymers (polyacetylene, polypyrrole, polythiophene, polyaniline, etc.), silicon carbide, ferrites (Fe2O3 + Ni / Zn / Cd / Co oxides), and carbonyl iron are some of the materials used to shield automotive radar sensors from harmful microwave electromagnetic radiation.

[0006] 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, and transmitted by the material, shielding effectiveness, return loss, and attenuation are just some of the material properties of interest for manufacturing plastic components for radar sensor applications. The frequency of the incident radiation and the thickness of the material are also important when capturing microwave energy that, if not eliminated or minimized, can interfere with the proper operation of automotive electronic sensors.

[0007] Carbon (e.g., powder, platelets, fibers) is emerging as the filler of choice for imparting electromagnetic interference properties to polymers that are substantially transparent to microwave radiation in their unfilled state. When used in, for example, under-the-hood housings in automobiles, polymer-carbon composites can protect radar sensors located inside the housing by preventing external or internal electromagnetic radiation from degrading the electronic performance of the sensors.

[0008] These and other shortcomings are addressed by aspects of the present disclosure. Summary of the Invention [Means for solving the problem]

[0009] Embodiments of the present disclosure relate to a thermoplastic composition comprising a thermoplastic polymer component including a polyester; and greater than 0.10 wt % to about 1.95 wt % carbon nanotube (CNT) filler. A 6 in (inch) x 8 in (inch) x 1 / 8 in (1 / 8 in) molded specimen of this composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free-space method. In some embodiments, the polyester comprises polybutylene terephthalate (PBT). Further embodiments include an article (e.g., radar sensor, camera, electronic control unit, etc.) that includes a molded portion that includes a microwave-absorbing material (absorber). The article may have at least two openings that allow transmission of microwave radiation between a transmitting antenna and a receiving antenna located in / on the sensor's printed circuit board.

[0010] In a further aspect, the present disclosure relates to a method of forming a thermoplastic composition comprising: combining a thermoplastic polymer component comprising a polyester with greater than 0.10 wt % to about 1.95 wt % of a carbon nanotube (CNT) filler to form a mixture; and molding the mixture to form a thermoplastic composition. A 6 in x 8 in x 1 / 8 in molded sample of the thermoplastic composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free space method.

[0011] The drawings are not necessarily drawn to scale, and in which like numerals may represent 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 herein. [Brief explanation of the drawings]

[0012] [Figure 1] 1A and 1B are schematic diagrams 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, respectively. [Figure 2] Figure 2 shows a typical graph of the magnitude of the scattering parameters (in dB) S11 (for reflection) and S21 (for transmission) for carbon-based materials used to absorb microwave radiation in the W-band at frequencies between 75 GHz and 110 GHz. [Figure 3] FIG. 3 is a graph illustrating the dielectric constant (real and imaginary parts) as a function of CNT loading observed at a frequency of 77 GHz for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 4] FIG. 4 is a graph illustrating the dielectric loss tangent (Df), or tan δ, as a function of CNT loading observed at a frequency of 77 GHz for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 5]FIG. 5 is a graph illustrating the attenuation constant as a function of CNT loading observed at a frequency of 77 GHz for exemplary compositions according to embodiments of the present disclosure and comparative compositions. [Figure 6] FIG. 6 is a graph illustrating the total shielding effectiveness as a function of CNT loading observed at a frequency of 77 GHz for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 7] FIG. 7 is a graph illustrating percent power in transmission mode as a function of CNT loading observed at a frequency of 77 GHz for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 8] FIG. 8 is a graph illustrating percent absorbed power in transmission mode and metal-backed reflection mode as a function of CNT loading for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 9] FIG. 9 is a graph illustrating surface resistivity as a function of CNT loading for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 10] FIG. 10 is a graph illustrating volume resistivity as a function of CNT loading for example compositions and comparative compositions according to aspects of the present disclosure. [Figure 11] FIG. 11 is a graph illustrating surface resistivity and volume resistivity as a function of CNT loading for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 12] FIG. 12 is a graph illustrating percent reflected power in transmission mode observed at a frequency of 77 GHz as a function of volume electrical resistivity for example compositions according to aspects of the present disclosure and comparative compositions. [Figure 13] FIG. 13 is a graph illustrating percent absorbed power in transmission mode observed at a frequency of 77 GHz as a function of volume electrical resistivity for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 14]FIG. 14 is a graph illustrating the real part of the complex permittivity as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 15] FIG. 15 is a graph illustrating the imaginary part of the complex permittivity as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 16] FIG. 16 is a graph illustrating attenuation as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 17] FIG. 17 is a graph illustrating total shielding effectiveness as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 18] FIG. 18 is a graph illustrating percent absorbed power measured in transmission mode as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 19] FIG. 19 is a graph illustrating percent absorbed power measured in metal-backed reflection mode as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 20] FIG. 20 is a graph illustrating absorbed power, reflected power, and transmitted power as a function of frequency in the W-band (75-110 GHz) for example composition Ex1 according to an embodiment of the present disclosure. [Figure 21] FIG. 21 is a graph illustrating absorbed power, reflected power, and transmitted power as a function of frequency in the W-band (75-110 GHz) for example composition Ex2 according to an embodiment of the present disclosure. [Figure 22] FIG. 22 is a graph illustrating the absorbed power, reflected power, and transmitted power as a function of frequency in the W-band (75-110 GHz) for the comparative composition CEx2. [Figure 23]FIG. 23 is a graph illustrating the absorbed power, reflected power, and transmitted power as a function of frequency in the W-band (75-110 GHz) for the comparative composition CEx3. [Figure 24] FIG. 24 is a graph illustrating notched and unnotched Izod impact strength at 23° C. for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 25] FIG. 25 is a graph illustrating notched and unnotched Izod impact strength at −30° C. for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 26] FIG. 26 is a graph illustrating the dielectric constant (real and imaginary parts) as a function of CNT loading observed at a frequency of 77 GHz for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 27] FIG. 27 is a graph illustrating the dielectric loss tangent (Df), or tan δ, as a function of CNT loading observed at a frequency of 77 GHz for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 28] FIG. 28 is a graph illustrating percent power in transmission mode as a function of CNT loading observed at a frequency of 77 GHz for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 29] FIG. 29 is a graph illustrating the real part of the complex permittivity as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 30] FIG. 30 is a graph illustrating the imaginary part of the complex permittivity as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 31] FIG. 31 is a graph illustrating attenuation as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. [Figure 32]FIG. 32 is a graph illustrating percent absorbed power measured in transmission mode as a function of frequency in the W-band (75-110 GHz) for example compositions and comparative compositions according to embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present disclosure describes a plastic thermoplastic material containing relatively low levels of multi-walled carbon nanotubes that can be used to manufacture microwave absorbers for sensors such as automotive radar sensors, and that can be injection molded using conventional molding processes.

[0014] Carbon nanotubes are preferred over carbon powder, graphite, or carbon fiber because they provide sufficient microwave interference performance at relatively low loadings. For example, lower carbon loadings improve the ductility, impact strength, surface aesthetics, and flowability of these materials under high shear rate conditions.

[0015] Another aspect of the present disclosure is an automotive radar sensor component (plate, housing, cover, etc.) molded from a material comprising a polymer and carbon nanotubes as a microwave absorbing filler, where the molded part has specific design, average thickness, microwave absorption efficiency, absorption bandwidth, shielding effectiveness, attenuation, and electrical surface resistivity and electrical volume resistivity properties.

[0016] A further aspect of the present disclosure includes an article (e.g., a radar sensor, a camera, an electronic control unit, etc.) that includes a molded portion that includes a microwave absorbing material (absorber). The article may have at least two openings that allow transmission of microwave radiation between a transmitting antenna and a receiving antenna located in / on the sensor's printed circuit board.

[0017] The present disclosure may be more readily understood by reference to the following detailed description and examples included therein. In various aspects, the present disclosure relates to a thermoplastic composition comprising a thermoplastic polymer component comprising a polyester; and greater than 0.10 wt % to about 1.95 wt % carbon nanotube (CNT) filler. A 6 in x 8 in x 1 / 8 in molded sample of this composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free-space method.

[0018] 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, unless otherwise specified, or to particular reagents, unless otherwise specified, as such may, 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.

[0019] Various combinations of elements of the present disclosure are encompassed by the present disclosure, for example combinations of elements from dependent claims that are dependent on the same independent claim.

[0020] Furthermore, unless expressly stated otherwise, it is understood that it is in no way intended that any method described herein be construed as requiring that its steps be performed in a specific order. Thus, where a method claim does not actually recite the order in which its steps are to be followed, or where the claim or the specification does not otherwise specifically indicate that the steps are limited to a specific order, no order is intended to be inferred in any respect. This applies to logical considerations regarding the sequencing of steps or the flow of operations; the plain meaning derived from grammatical construction and punctuation; and any possible implicit basis for interpretation, including the number or type of embodiments described herein.

[0021] All publications mentioned herein are incorporated by reference to disclose and describe the methodologies and / or materials in connection with which the publications are cited. definition

[0022] 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. As used herein and in the claims, the term "comprising" can include embodiments such as "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. In this specification and in the appended claims, reference will be made to several terms that are intended to be defined herein.

[0023] As used herein and in 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 "polyethylene polymer" includes a mixture of two or more polyethylene polymers.

[0024] As used herein, the term "combination" is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0025] Ranges can be expressed herein as from one value (first value) to another value (second value). When such a range is expressed, the range, in some embodiments, includes one or both of the first and second values. Similarly, when values ​​are expressed as approximations, it will be understood that the use of the antecedent "about" introduces another embodiment of the specified value. It will be further understood that the endpoints of each range are valid both relative to the other endpoint, and independently of the other endpoint. It is also understood that there are multiple values ​​disclosed herein, and that each value is also herein disclosed as "about" that value in addition to the specified value itself. For example, if the value "10" is disclosed, then "about 10" is also disclosed. It is also understood that every unit between two specified units is disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0026] As used herein, the terms "about" and "at or near" mean that the quantity or value in question can be the specified value, approximately the specified value, or nearly the same as the specified value. As used herein, unless otherwise indicated or inferred, the value is generally understood to be a ±10% variation of the stated nominal value. This term is intended to convey that an equivalent result or effect as recited in the claims is facilitated by such similar values. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but can be approximate and / or larger or smaller as desired, reflecting tolerances, conversion factors, rounding, measurement errors, and the like, as well as 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 defined as such. When "about" is used before a quantitative value, the parameter is also understood to include the specific quantitative value itself, unless specifically defined otherwise.

[0027] Disclosed are not only the components used to prepare the disclosed compositions, but also the compositions themselves used within the methods disclosed herein. These and other materials are disclosed herein, and it is understood that when disclosing combinations, subsets, interactions, groups, etc. of these materials, each of the various individual and collective combinations and permutations of these compounds is specifically contemplated and described herein, although not all specifically mentioned. For example, when a particular compound is disclosed and discussed, and multiple modifications that can be made to multiple molecules comprising the compound are discussed, what is specifically contemplated is each and every combination and permutation of the compound and modifications possible, unless otherwise specifically indicated to the contrary. Thus, when a class of molecules A, B, and C is disclosed, as well as classes of molecules D, E, and F, and an example of a combined molecule AD is disclosed, this means that each is individually and collectively contemplated, even if not individually mentioned, and that the combinations AE, AF, BD, BE, BF, CD, CE, and CF are considered to be disclosed. Likewise, any subsets or combinations of these are also disclosed. Thus, for example, the subgroups AE, BF, and CE could be 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 can be performed, it is understood that each of these additional steps can be performed with any specific aspect or combination of aspects of the disclosed methods.

[0028] In this specification and the appended claims, reference to parts by weight of a particular component or ingredient in a composition or article indicates the weight relationship, expressed in parts by weight, between that component or ingredient and the other components or ingredients in the composition or article. 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 included in the compound.

[0029] Weight percentages of ingredients are based on the total weight of the formulation or composition in which the ingredient is included, unless specifically stated to the contrary.

[0030] The terms "residue" and "structural unit" used in reference to components of polymers are synonymous throughout this specification.

[0031] As used herein, the terms "weight percent," "wt%," and "wt.%" can be used interchangeably and refer to the weight percent of a given component based on the total weight of the composition, unless otherwise specified. That is, all wt% values ​​are based on the total weight of the composition, unless otherwise specified. It is best understood that the sum of the wt% values ​​of all components in a disclosed composition or formulation equals 100.

[0032] Unless otherwise stated herein to the contrary, all test standards are the latest standards in effect at the time of filing this application.

[0033] Each of the materials disclosed herein is commercially available and / or methods for its preparation are known to those skilled in the art.

[0034] It is understood that the compositions disclosed herein have specific functions. Disclosed herein are specific structural requirements that perform the disclosed functions, and it is understood that there are various structures that can perform the same function associated with the disclosed structures, and that these structures will typically achieve the same result. thermoplastic composition

[0035] In some embodiments, a polyester (e.g., polybutylene terephthalate (PBT)) masterbatch containing a certain amount of multi-walled carbon nanotubes (CNTs) is combined with virgin, unfilled polyester resin to dilute the original masterbatch and form blends with varying concentrations of nanotubes. The carbon nanotubes impart electrical conductivity and microwave absorption properties to the composition. One suitable masterbatch composition for use in embodiments of the present disclosure is PLASTICYL™ PBT1501 (available from NANOCYL), a multi-walled carbon nanotube (MWCNT) PBT masterbatch containing 15 weight percent nanotubes. NANOCYL® nanotubes are thin, multi-walled carbon nanotubes produced by catalytic chemical vapor deposition (CCVD). Carbon nanotubes are tubular materials with nanometer-sized diameters composed entirely of carbon atoms. Graphite layers can be visualized as a rolled-up wire mesh, with a continuous, unbroken hexagonal network and carbon atoms at the vertices of the hexagons. Due to the action of van der Waals forces, carbon nanotubes tend to aggregate into bundles or weak aggregates. As a result, carbon nanotubes appear as a black powder. However, at the nanoscale, they have a spaghetti-like structure.

[0036] One advantage of carbon nanotubes is that compositions containing them have improved mechanical properties compared to other conductive fillers, such as carbon black or graphite, due to the relatively low amount of nanotubes required to reach a particular electrical conductivity as a result of their high aspect ratio. Nanotubes typically increase viscosity more than carbon black at equal loadings, but in most cases, significantly less nanotube is required for processing. Other advantages of CNTs include high electrical conductivity, good processability, retention of mechanical properties, high recyclability in thermoplastics, and good heat dissipation properties (among others). Specific properties of Nanosil's NC7000™ CNTs are as follows:

[0037] [Table 1] From Nanosil's NC7000™ technical data sheet.

[0038] In certain embodiments, the present disclosure relates to a thermoplastic composition comprising a thermoplastic polymer component comprising a polyester; and greater than 0.10 wt % to about 1.95 wt % carbon nanotube (CNT) filler. A 6 in x 8 in x 1 / 8 in molded specimen of the composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free-space method. As used herein, "molded specimen" refers to a 6 in x 8 in x 1 / 8 in injection-molded specimen of the composition.

[0039] The free-space method used to measure the dielectric properties of the compositions of the present disclosure involves a vector network analyzer, two antennas facing each other, and a sample holder positioned equidistant between the antennas. The basic experimental quantities generated by the free-space method are so-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. S-parameters are typically identified by a two-digit suffix, the first of which refers to the response port, while the second refers to the input port. Thus, S 21 denotes the response at port 2 due to a signal at port 1. Scattering parameters are complex numbers with real and imaginary parts that describe the amount of microwave radiation that is either reflected from or transmitted through the sample. For example, the scattering parameter S for reflection is 11 represents the signal originating from antenna 1 and, after hitting the sample and being reflected back and received at the same antenna. Similarly, the scattering parameter S for transmission 21 represents the signal originating from antenna 1 and received at antenna 2 after transmitting through the material under test. The scattering parameters for reflection and transmission, S for reflection, represent the signal originating from antenna 2. 22 and S for transmission 12 can also be defined. The four S-parameters defined above, S 11 , S 22 , S 21 , S 12 can be determined for a two-port network, and the S-parameter matrix can be used to determine the reflection coefficient and transmission gain from both sides of this network. 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 permeability of the magneto-dielectric material under test. These methods are non-contact, meaning that the material under measurement does not come into direct contact with any active components of the equipment involved in the measurement.

[0040] Schematics of the apparatus used to measure the dielectric properties of the materials of this disclosure using the free-space method are shown in Figures 1A and 1B for unbacked and metal-backed samples, respectively. These free-space permittivity measurements use injection-molded plaques measuring 6 inches by 8 inches by 1 / 8 inch.

[0041] Dielectric measurements using the free-space method can be performed in two different modes: transmission mode and metal-backed reflection mode. In the transmission mode of measurement, it is possible to measure three types of radiation: absorption into the sample, reflection from the sample, and transmission through the sample. On the other hand, in the metal-backed reflection mode of measurement, a metallic plate (stainless steel, aluminum, etc.) is placed between the material under test and the receiving antenna, so that transmission through the sample is almost completely suppressed and only the microwave absorption into and reflection from the material can be evaluated. The combination of two antennas in transmission mode provides the scattering parameter S for reflection. 11 and the scattering parameter S for transmission 21 Since only the total energy incident on the sample (i.e., 100%) can be measured, the amount of radiation absorbed (in percent) by the material under test is the sum of the total energy incident on the sample (i.e., 100%) and the radiation transmitted through the sample (S 21 and reaches the receiving antenna) and the radiation reflected from the sample (S 11 The percent absorbed power is calculated as the difference between the sum of the amount (in percent) of radiation (measured from the radiating antenna and returned to the radiating antenna). In many applications, it is desirable to maximize the percent absorbed power and minimize the percent reflected and transmitted power when measured using the transmission mode. 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 manufacturing plastic components for radar sensor applications. The frequency of the incident radiation and the thickness of the material are also important when capturing microwave energy that, if not eliminated or minimized, could interfere with the proper operation of automotive electronic sensors.

[0042] Figure 2 shows the scattering parameters (in dB) S of carbon-based materials used to absorb microwave radiation in the W band at frequencies between 75 GHz and 110 GHz. 11 (for reflection) and S 21 A typical graph of the magnitude of the S 11 S equal to zero dB indicates that the material exhibits no reflection loss (is 100% reflective), which is the case for metal plates made of aluminum or stainless steel. 21 S equal to zero dB means that the material experiences no transmission loss (100% transmission), which is the case for air. In this context, S greater than 0 dB 11 Any material with an S greater than 0 dB will be less than 100% reflective (will experience some loss in reflection). 21 A material with a value of 0.05 GHz will have less than 100% transmission (some loss in transmission). The negative sign in the S-parameter value indicates that energy has been lost, with larger negative numbers indicating larger losses. As the graph shows for a frequency of 77 GHz, S 11 is equal to approximately -2.5 dB, representing a percent reflected power of 31.6%, and S 21 equal to approximately -15 dB corresponds to a percent transmitted power of 0.1%, and a difference of 100% equals a percent absorbed power of approximately 68.3%.

[0043] In its most general definition, the shielding effectiveness (SE) of a material describes its ability to reduce electromagnetic radiation around it by blocking the field with a barrier or shield made from conductive and / or magnetic components. In these cases, shielding can be achieved by either absorbing or reflecting some or all of the electromagnetic radiation incident on the material to be protected. The ability of a shielding material to block this harmful radiation typically depends on the frequency (or wavelength) of the incident radiation, the thickness of the protective layer, and is expected to vary with the electrical conductivity and / or dielectric properties of the material. The total shielding effectiveness of a material is the result of reflection, absorption, and internal reflection losses and is given by the following formula: SE T (dB) = SE A + SE R + SE M It is expressed as:

[0044] If the total shielding efficiency is greater than 10 dB, the multiple reflection SE M The shielding effectiveness due to is usually negligible. Therefore, the total shielding effectiveness is: SE T (dB)=SE A +SE R It becomes simple as

[0045] SE A and S.E. R The following is obtained from S-parameter measurements using a vector network analyzer:

[0046]

number

[0047] In the above equation, S 11 is the scattering parameter for reflection, and S 21 is the scattering parameter for transmission. R and SE A In the formula, SE T Substituting the formula, the total shielding effectiveness is SE T=-10 log(|S 21 | 2 ), which is similar to the equation for transmission loss or insertion loss. Similar equations can be used to calculate attenuation, reflection, and insertion loss, absorbed power, and many other dielectric properties in terms of scattering parameters. The formulas used to calculate the properties of the materials of this disclosure are provided below.

[0048] Reflection and transmission coefficients: * The reflection coefficient formula is:

[0049]

number

[0050] In the above formula,

[0051]

number

[0052]

number

[0053]

number

[0054] Complex relative permittivity:

[0055]

number

[0056]

number

[0057] Loss tangent:

[0058]

number

[0059] Propagation constant: γ=α+jβ, where γ is calculated using the extracted complex permittivity and complex permeability as follows:

[0060]

number

[0061] The attenuation constant α reduces the signal amplitude along the transmission line and is calculated as α = Real(γ) (Np / m, or Neper / m), as follows: α(dB / cm)=-0.086859 α(Np / m) The signal is plotted in dB / cm using

[0062] Return loss (RL) and insertion loss (IL):

[0063]

number

[0064] Calculated S 11 and S 21 Parameters

[60] : The reflection and transmission coefficients are calculated using the extracted permittivity and permeability as follows:

[0065]

number

[0066]

number

[0067] Percent Power: Microwave absorption cannot be measured directly and is measured by reflection (S 11 from) and transmission (S 21 Since only 1 / 2 of the radiated current is absorbed, the percent absorbed power can be calculated from:

[0068]

number

[0069] Scattering parameters for reflection in metal-backed reflection mode: S 11 is calculated using the transmission line model:

[0070]

number

[0071]

number

[0072]

number

[0073]

number

[0074]

number

[0075]

number

[0076] Suitable polyesters include, but are not limited to, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), poly(cyclohexylene dimethylene terephthalate) (PCT), polyethylene terephthalate glycol (PETG), polycyclohexylene dimethylene terephthalate glycol (PCTG), polycyclohexylene dimethylene terephthalic acid (PCTA), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymers thereof, or combinations thereof. Suitable polyester components include, but are not limited to, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), poly(cyclohexylene dimethylene terephthalate) (PCT), polyethylene terephthalate glycol (PETG), polycyclohexylene dimethylene terephthalate glycol (PCTG), polycyclohexylene dimethylene terephthalic acid (PCTA), copolymers thereof, or combinations thereof. PCT is a crystalline polyester formed from cyclohexanedimethanol (CHDM) and dimethyl terephthalate (DMT) or terephthalic acid (TPA). PETG and PCTG are copolyesters formed by including ethylene glycol (EG) in the polymerization reaction. PETG is formed when less than 50% of the diol content in the copolyester is CHDM, and PCTG is formed when 50% or more of the diol content in the copolyester is CHDM. PCTA is formed by including an additional diacid, such as isophthalic acid (IPA). In a detailed embodiment, the polyester component comprises PBT.

[0077] CNT fillers, in some embodiments, have an average diameter of about 5 to 15 nanometers (nm) and a density of at least 100 square meters per gram (m 2 / g) surface area, and / or 10 -3 The CNT filler may have a volume resistivity of less than ohm-centimeter (Ω-cm). Exemplary CNTs are available from Nanosil (e.g., NC7000™). In specific embodiments, the CNT filler is in the form of a masterbatch. In detailed embodiments, the CNT filler does not include CNT powder.

[0078] The CNT filler can be present in the composition in an amount of about 0.01 wt% to about 1.95 wt%. In some embodiments, the composition comprises 0.10 wt% to about 1.95 wt%, or greater than 0.10 wt% to about 1.95 wt%, or 0.25 wt% to about 1.95 wt%, or 0.25 wt% to about 1.95 wt%, or greater than 0.25 wt% to about 1.0 wt%, or greater than 0.25 wt% to less than 1.0 wt% CNT filler.

[0079] In certain embodiments, the composition includes a polycarbonate-siloxane copolymer. The polycarbonate-siloxane copolymer can be present in an amount of about 5 wt% to about 45 wt%, or about 5 wt% to about 25 wt%, or about 15 wt% to about 25 wt%, or about 20 wt% in some embodiments. In detailed embodiments, the polycarbonate-siloxane copolymer has a siloxane content of about 20 wt%. Exemplary polycarbonate-siloxane copolymers suitable for use in embodiments of the present disclosure are EXL copolymers available from SABIC, with exemplary siloxane contents of 6 wt% or 20 wt%.

[0080] In some embodiments, the composition includes at least one additional additive. The at least one additional additive may include, but is not limited to, an acid scavenger, an anti-drip agent, an antioxidant, an anti-static agent, a colorant, a demolding agent, a flow promoter, a lubricant, a mold release agent, a plasticizer, a quenching agent, a flame retardant, a UV reflective additive, an impact modifier, a blowing agent, a reinforcing agent, or a combination thereof. The at least one additional additive may be included in the thermoplastic composition in any amount that does not significantly adversely affect the desired properties of the composition. In certain embodiments, the at least one additional additive does not include a chain extender. In further embodiments, the at least one additional additive does not include a dispersant. In still further embodiments, the at least one additional additive does not include a curing agent.

[0081] In certain embodiments, the composition comprises at least 10 11 In a further embodiment, the composition has a volume resistivity of at least 10 Ω.cm. The volume resistivity may be determined in accordance with ASTM D257. 12 Ω.cm, or at least 10 13 Ω.cm, or at least 10 14 Ω.cm, or 10 11 Ω.cm to 10 15 It has a volume resistivity of Ω.cm.

[0082] In some embodiments, a 6 in x 8 in x 1 / 8 in molded sample of the composition has a percent absorbed power measured in transmission mode when observed at frequencies from 75 GHz to 110 GHz according to the free-space method of at least 60%. In other embodiments, a molded sample of the composition has a percent absorbed power measured in transmission mode when observed at frequencies from 75 GHz to 110 GHz according to the free-space method of at least 61%, or at least 62%, or at least 63%, or at least 64%, or at least 65%, or at least 66%, or at least 67%, or at least 68%, or at least 69%, or at least 70%, or at least 71%, or at least 72%, or at least 73%, or at least 74%, or at least 75%, or 60-85%, or 65-85%, or 70-85%, or 74-85%.

[0083] In certain embodiments, the composition comprises greater than 0.25 wt% and less than 1 wt% CNT filler, and a 6 in x 8 in x 1 / 8 in molded sample of the composition has a percent absorbed power measured in transmission mode of at least 74% when observed at a frequency of 77 GHz according to the free space method. Manufacturing method

[0084] One or any of the preceding components described herein may first be dry-blended with each other or with any combination of the preceding components, and then fed into the extruder from a single or multiple feeder, or fed separately from a single or multiple feeder. 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 from a throat hopper or any side feeder.

[0085] The extruder 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.

[0086] The components may also be mixed together and then melt-blended to form the thermoplastic composition. Melt-blending the components may involve the use of shear force, extensional force, compression force, ultrasonic energy, electromagnetic energy, thermal energy, or a combination comprising at least one of the foregoing forms of force or energy.

[0087] The barrel temperature on the extruder during compounding can be set to a temperature such that at least a portion of the polymer reaches a temperature above about the melting point if the resin is a semi-crystalline organic polymer, or above about the pour point (e.g., glass transition temperature) if the resin is an amorphous resin.

[0088] A mixture containing the aforementioned components may be subjected to multiple blending and forming steps, if desired. For example, the thermoplastic composition may first be extruded and formed into pellets. The pellets may then be fed to a molding machine where they may be formed into any desired shape or product. Alternatively, the thermoplastic composition exiting a single melt blender may be formed into sheets or strands and subjected to post-extrusion processes such as annealing, uniaxial or biaxial orientation, etc.

[0089] In some embodiments, the melt temperature in this process may be kept as low as possible to avoid excessive thermal degradation of the components. In certain embodiments, the melt temperature is maintained between about 230°C and about 350°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 may be cooled by passing them through a water bath. The cooled strands can be cut into pellets for packaging and further handling.

[0090] In some embodiments, a method of forming a thermoplastic composition includes: combining a thermoplastic polymer component including a polyester with greater than 0.10 wt% to about 1.95 wt% of a carbon nanotube (CNT) filler to form a mixture; and molding the mixture to form a thermoplastic composition. A 6 in x 8 in x 1 / 8 in molded sample of the thermoplastic composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free-space method. In further embodiments, the molding step includes at least one of extruding, injection molding, rotational molding, blow molding, or thermoforming the mixture to form the thermoplastic composition. manufactured goods

[0091] In certain embodiments, the present disclosure relates to formed, formed, or molded articles comprising the thermoplastic compositions. The thermoplastic compositions can be molded into useful shapes by various means, such as injection molding, extrusion, rotational molding, blow molding, and thermoforming, to form articles and structural components for, for example, energy storage batteries, battery electrodes, plates for heat exchangers, personal or commercial electronic devices, including, but not limited to, cell phones, tablet computers, personal computers, notebooks, and portable computers, and other such devices, medical applications, RFID applications, automotive applications, and the like. In further embodiments, the articles are extruded. In yet other embodiments, the articles are injection molded. In certain embodiments, the articles are microwave absorbers for internal or external radar sensors. In further embodiments, the articles are microwave absorbers for radar sensors, cameras, or electronic control units. In certain embodiments, the articles include a transmitting antenna, a receiving antenna, and at least two openings that allow microwave radiation to be transmitted between the transmitting and receiving antennas.

[0092] Various combinations of elements of the present disclosure are encompassed by the present disclosure, for example combinations of elements from dependent claims that are dependent on the same independent claim. Aspects of the Disclosure

[0093] In various aspects, the present disclosure relates to and includes at least the following aspects:

[0094] Aspect 1. A thermoplastic polymer component comprising a polyester; greater than 0.01 wt% to about 1.95 wt% carbon nanotube (CNT) filler; A thermoplastic composition comprising, consisting of, or consisting essentially of: A composition having a percent absorbed power measured in transmission mode of at least 60% when a molded sample of the composition is observed at a frequency of 77 GHz according to the free space method.

[0095] Embodiment 2. The thermoplastic composition of embodiment 1, wherein the polyester comprises polybutylene terephthalate (PBT), polyethylene terephthalate (PET), poly(cyclohexylene dimethylene terephthalate) (PCT), polyethylene terephthalate glycol (PETG), polycyclohexylene dimethylene terephthalate glycol (PCTG), polycyclohexylene dimethylene terephthalate (PCTA), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymers thereof, or combinations thereof.

[0096] Embodiment 3. The thermoplastic composition of embodiment 1 or 2, wherein the composition comprises polybutylene terephthalate (PBT).

[0097] Embodiment 4. The CNT filler has an average diameter of about 5 to 15 nanometers (nm), a density of at least 100 square meters per gram (m 2 / g) surface area, and 10 -3 4. The thermoplastic composition of any one of embodiments 1 to 3, having a volume resistivity of less than ohm.centimeter (Ω.cm).

[0098] Aspect 5. At least 1.0 x 10 11 5. The thermoplastic composition of any one of the preceding aspects, having a volume electrical resistivity of Ω·cm.

[0099] Embodiment 6. The thermoplastic composition of any one of embodiments 1 to 5, wherein a molded sample of the composition has a percent absorbed power measured in transmission mode of at least 65% when observed at frequencies from 75 GHz to 110 GHz according to the free space method.

[0100] Embodiment 7. The thermoplastic composition of any one of embodiments 1 to 6, comprising from about 0.01 wt % to less than about 1 wt % CNT filler, wherein a molded sample of the composition has a percent absorbed power measured in transmission mode of at least 75% when observed at a frequency of 77 GHz according to the free space method.

[0101] Embodiment 8. The thermoplastic composition of any one of Embodiments 1 to 7, further comprising at least one additional additive.

[0102] Embodiment 9. The thermoplastic composition of embodiment 8, wherein the at least one additional additive comprises an acid scavenger, an anti-drip agent, an antioxidant, an anti-static agent, a chain extender, a colorant, a demolding agent, a flow promoter, a lubricant, a mold release agent, a plasticizer, a quenching agent, a flame retardant, a UV reflective additive, an impact modifier, a blowing agent, a reinforcing agent, or a combination thereof.

[0103] Embodiment 10. An article comprising the thermoplastic composition.

[0104] Aspect 11. The article of aspect 10, which is a microwave absorber for an internal or external radar sensor.

[0105] Embodiment 12. The article of embodiment 10 or 11, which is a microwave absorber for a radar sensor, a camera, or an electronic control unit.

[0106] Embodiment 13. The article of any one of embodiments 10 to 12, comprising a transmitting antenna, a receiving antenna, and at least two openings that allow transmission of microwave radiation between the transmitting and receiving antennas.

[0107] Embodiment 14. A method of forming a mixture by combining a thermoplastic polymer component comprising a polyester with about 0.01 wt% to about 1.95 wt% of a carbon nanotube (CNT) filler; molding the mixture to form a thermoplastic composition; 1. A method for forming a thermoplastic composition comprising, consisting of, or consisting essentially of: A method wherein a molded sample of the thermoplastic composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free space method.

[0108] Embodiment 15. The method of embodiment 14, wherein molding the mixture comprises at least one of extruding, injection molding, rotational molding, blow molding, or thermoforming the mixture to form a thermoplastic composition.

[0109] Embodiment 16. A thermoplastic polymer component comprising a polyester; greater than 0.10 wt% to about 1.95 wt% carbon nanotube (CNT) filler; A thermoplastic composition comprising, consisting of, or consisting essentially of: A thermoplastic composition having a percent absorbed power measured in transmission mode of at least 60% when a 6 inch (in) x 8 in x 1 / 8 inch molded sample of the composition is observed at a frequency of 77 GHz according to the free space method.

[0110] Embodiment 17. The thermoplastic composition of embodiment 16, wherein the polyester comprises polybutylene terephthalate (PBT), polyethylene terephthalate (PET), poly(cyclohexylene dimethylene terephthalate) (PCT), polyethylene terephthalate glycol (PETG), polycyclohexylene dimethylene terephthalate glycol (PCTG), polycyclohexylene dimethylene terephthalate (PCTA), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymers thereof, or combinations thereof.

[0111] Embodiment 18. The thermoplastic composition of embodiment 16 or 17, wherein the composition comprises polybutylene terephthalate (PBT).

[0112] Embodiment 19. The CNT filler has an average diameter of about 5 to 15 nanometers (nm), a density of at least 100 square meters per gram (m 2 / g) surface area, and 10 -3 19. The thermoplastic composition of any one of embodiments 16 to 18, having a volume resistivity of less than ohm.centimeter (Ω.cm).

[0113] Aspect 20. At least 1.0 x 10 11 20. The thermoplastic composition of any one of embodiments 16 to 19, having a volume electrical resistivity of Ω·cm.

[0114] Embodiment 21. The thermoplastic composition of any one of embodiments 16 to 20, wherein a 6 in x 8 in x 1 / 8 in molded sample of the composition has a percent absorbed power measured in transmission mode of at least 60% when observed at frequencies from 75 GHz to 110 GHz according to the free space method.

[0115] Embodiment 22. The thermoplastic composition of any one of embodiments 16 to 21, comprising greater than 0.25 wt % and less than 1 wt % CNT filler, wherein a 6 in x 8 in x 1 / 8 in molded sample of the composition has a percent absorbed power measured in transmission mode of at least 74% when observed at a frequency of 77 GHz according to the free space method.

[0116] Embodiment 23. The thermoplastic composition of any one of embodiments 16 to 22, further comprising a polycarbonate-siloxane copolymer.

[0117] Embodiment 24. The thermoplastic composition of any one of embodiments 16 to 21, comprising greater than 0.25 wt % to about 1.95 wt % CNT filler, wherein a molded sample of the composition has an attenuation constant of at least −30 dB / cm when observed at a frequency of 77 GHz according to the free space method.

[0118] Embodiment 25. The thermoplastic composition of any one of embodiments 16 to 24, further comprising at least one additional additive, wherein the at least one additional additive comprises an acid scavenger, an anti-drip agent, an antioxidant, an anti-static agent, a colorant, a demolding agent, a flow promoter, a lubricant, a mold release agent, a plasticizer, a quenching agent, a flame retardant, a UV reflective additive, an impact modifier, a blowing agent, a reinforcing agent, or a combination thereof.

[0119] Embodiment 26. An article comprising the thermoplastic composition of any one of embodiments 16 to 25.

[0120] Aspect 27. The article of aspect 26, which is a microwave absorber for an internal or external radar sensor.

[0121] Embodiment 28. The article of embodiment 26, which is a microwave absorber for a radar sensor, a camera, or an electronic control unit.

[0122] Embodiment 29. The article of any one of embodiments 26 to 28, comprising a transmitting antenna, a receiving antenna, and at least two openings that allow transmission of microwave radiation between the transmitting antenna and the receiving antenna.

[0123] Embodiment 30. A method of forming a mixture by combining a thermoplastic polymer component comprising a polyester with greater than 0.10 wt% to about 1.95 wt% of a carbon nanotube (CNT) filler; molding the mixture to form a thermoplastic composition; 1. A method for forming a thermoplastic composition comprising, consisting of, or consisting essentially of: A method in which a 6 in x 8 in x 1 / 8 in molded sample of the thermoplastic composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free space method.

[0124] Embodiment 31. The method of embodiment 30, wherein molding the mixture comprises at least one of extruding, injection molding, rotational molding, blow molding, or thermoforming the mixture to form a thermoplastic composition. [Example]

[0125] The following examples are presented to provide those skilled 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 not intended to limit the disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but it is desirable to account for some error and deviation. Unless otherwise indicated, parts are parts by weight, temperature is in ° C. or is ambient temperature, and pressure is at or near atmospheric pressure. Unless otherwise indicated, percentages referring to compositions are in terms of wt%.

[0126] There are numerous variations and combinations of reaction conditions, such as component concentrations, desired solvents, solvent mixtures, temperatures, pressures, and other reaction ranges, as well as 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 no more than reasonable and routine experimentation.

[0127] The PBT-MWCNT masterbatch used in the compositions described herein was diluted with different amounts of virgin, unfilled Ultradur® B4500 (BASF), a medium-viscosity PBT grade suitable for use in the production of thin-walled profiles and pipes. This grade is also suitable for the production of industrial features for injection molding applications. The amount of masterbatch in the composition was varied from 20 weight percent to 5 weight percent, and the amount of virgin PBT resin was varied from 80 weight percent to 95 weight percent. These polymer / masterbatch ratios produced materials containing about 3 weight percent to about 0.75 weight percent carbon nanotubes in the final formulation. Example and comparative compositions were prepared and various properties were measured as described in Table 1:

[0128] [Table 2] * The PBT for CEx1 was Valox 325

[0129] Graphs of the above data are illustrated in Figures 3-23.

[0130] Figure 3 shows that both the real and imaginary parts of the complex permittivity increase with the CNT loading in the formulation. Figure 4 shows the same trend for the dielectric loss tangent (ε" / ε'), or tan δ, observed in these formulations. Figure 5 shows that the attenuation constant increased from approximately -35 dB / cm to approximately -160 dB / cm, and Figure 6 shows that the total shielding effectiveness increased from approximately 12 dB to approximately 60 dB with increasing CNT loading in the formulation. Figure 7 shows that the percent reflected power measured in transmission mode increases with CNT loading, while both the percent transmitted and absorbed power measured in transmission mode decrease with increasing CNT loading. As these results show for a frequency of 77 GHz, the percent reflected power measured in transmission mode increased from approximately 19 dB to approximately 19 dB for 0.75 wt% nanotubes. % nanotubes to approximately 46% at 3 wt% nanotubes. Similarly, the percent transmitted power measured in transmission mode decreased from approximately 4% at 0.75 wt% nanotubes to virtually unmeasurable at 3 wt% nanotube concentrations. The percent absorbed power measured in transmission mode decreased monotonically from approximately 77% at 0.75 wt% nanotubes to approximately 54% at 3 wt% nanotubes. These results can be explained in terms of the observed electrical resistivity of these materials, since with increasing amounts of conductive fillers, these materials become more conductive, thereby exhibiting metal-like dielectric behavior, resulting in less absorption, transmission, and more reflection of microwave radiation compared to polymer-based materials.

[0131] Figure 8 shows that the percent absorbed power at 77 GHz, measured in both transmission and metal-backed reflection modes, was similar for all CNT loadings investigated. This result may be explained by the low microwave transmission observed in these compositions, which may cause the material under test to behave approximately as a metal plate positioned between the sample and the receiving antenna. Figures 9 and 10 show how the surface and volume electrical resistivities, respectively, decreased with the amount of CNT filler added to the formulation. It is also worth noting that relatively small amounts of CNT conductive filler render these compositions essentially opaque (non-transparent) to microwave radiation at 77 GHz, while the electrical resistivity of the base polymer was only marginally affected. Figure 11 shows a back-to-back comparison of the surface and volume electrical resistivities of compositions of the present disclosure in terms of CNT loading. The similar results observed for both electrical resistivities suggest that the compounding step used to prepare these materials resulted in a relatively uniform distribution of conductive fibrils in the polymer matrix. 12 and 13 show that as the CNT loading increases and these compositions become more conductive (lower volume resistivity), the percent reflected power in transmission mode increases and the percent absorbed power in transmission mode decreases.

[0132] Figures 14 and 15 show the real and imaginary parts of the complex permittivity, respectively, for the entire frequency range (75-110 GHz) in the W-band. As both graphs show, the complex permittivity of the compositions of the present disclosure is substantially independent of frequency over the frequency range examined. Figures 16 and 17 show the attenuation constant and total shielding effectiveness, respectively, for the entire frequency range examined (75-110 GHz). Figures 18 and 19 show the percent absorbed power in transmission mode and metal-backed reflection mode, respectively, for the entire frequency range examined (75-110 GHz). Figures 20, 21, 22, and 23 show the percent absorption, reflection, and transmitted power measured in transmission mode, respectively, for the entire frequency range of the W-band (75-110 GHz) for Ex1, Ex2, CEx2, and CEx3 described in the present disclosure.

[0133] Measurements of ε' and ε" observed at 67 GHz for a 3.132 mm thick slab of pure, unfilled VALOX / PBT showed that the calculated percent transmitted, reflected, and absorbed power for the pure resin at 67 GHz were 72%, 27.5%, and 0.4%, respectively. From these results, it can be inferred that the highest percent absorbed power measured in transmission mode for example compositions of the present disclosure will occur at 0.75 wt% or less of carbon nanotubes. Most preferred compositions will absorb 60% or more, and more preferably 65% ​​or more, of 77 GHz microwave radiation.

[0134] Additional comparative and example compositions were prepared and tested as shown in Tables 2A and 2B:

[0135] [Table 3-1]

[0136] [Table 3-2]

[0137] [Table 4-1]

[0138] [Table 4-2]

[0139] The compositions in Tables 2A and 2B were tested to evaluate the CNT content that could produce the highest microwave absorption at 77 GHz. The compositions in Table 1 demonstrate that the highest microwave absorption at 77 GHz can occur at 0.75 wt% or less of CNT. Table 2A shows that composition Ex2.4, which contained only 0.5 wt% CNT, had a MW absorption at 77 GHz of 78.46%.

[0140] Graphs of impact properties for the compositions in Table 2 are illustrated in Figures 24 and 25. At 23°C, compositions Ex2.3-Ex2.7 all had an NII of at least 146 J / m, in contrast to comparative composition C2.3, which had an NII of 130 J / m. Thus, compositions according to embodiments of the present disclosure have an NII at 23°C, tested according to ASTM D256 and ASTM D4812, of greater than 130 J / m, or at least greater than 135 J / m, or at least greater than 140 J / m, or at least greater than 145 J / m, or from greater than 130 J / m to 180 J / m, or from 135 J / m to 180 J / m, or from 140 J / m to 180 J / m, or from 145 J / m to 180 J / m.

[0141] Similarly, compositions Ex2.3-Ex2.7 according to embodiments of the present disclosure had improved low-temperature (-30°C) impact properties compared to comparative composition C2.3. Thus, compositions according to embodiments of the present disclosure may have an NII at -30°C, tested according to ASTM D256 and ASTM D4812, of at least 90 J / m, or at least 92 J / m, or at least 95 J / m, or at least 100 J / m, or at least 102 J / m, or from 90 J / m to 150 J / m, or from 92 J / m to 150 J / m, or from 95 J / m to 150 J / m, or from 100 J / m to 150 J / m, or from 102 J / m to 150 J / m.

[0142] Graphs of the dielectric properties of the compositions in Table 2 at 77 GHz are shown in Figures 26 to 28. Figure 26 shows that as the carbon nanotube concentration in the composition increases from 0.05 wt% to 3 wt%, both the real and imaginary parts of the complex dielectric constant increase. Because the imaginary part of the complex permittivity increases more rapidly than the real part of the complex permittivity with increasing carbon nanotube concentration in the composition, the dielectric loss tangent (Df), i.e., the ratio of the imaginary permittivity to the real permittivity (e" / e'), also increased with increasing carbon nanotube concentration in the composition (Figure 27). The average thicknesses of 6 in × 8 in × 1 / 8 in slabs molded from compositions C2.1, C2.2, Ex2.3–Ex2.7, and C2.8 were 2.983 mm, 3.10 mm, 3.092 mm, 3.086 mm, 3.054 mm, 3.051 mm, 3.126 mm, and 3.065 mm, respectively.

[0143] Similarly, as the concentration of carbon nanotubes in the composition increased from 0.05 wt% to 3%, the percent reflected power measured in transmission mode increased from about 9% to about 42%, while the percent transmitted power measured in transmission mode decreased continuously from about 64% to virtually no transmission. The percent absorbed power measured in transmission mode exhibited surprising behavior: it increased continuously from about 27.5% at 0.05 wt% CNTs to about 78.5% at 0.5 wt% CNTs, and then decreased continuously to about 58% at 3 wt% CNTs in the formulation. These results suggest that the highest microwave absorption at 77 GHz occurs when the concentration of carbon nanotubes in the composition is about 0.5 wt% (Figure 28).

[0144] Graphs of the dielectric properties of the compositions in Table 2 at various frequencies in the W-band (75-110 GHz) are shown in Figures 29-32. Figure 29 shows that as the carbon nanotube concentration in the composition increases from 0.05 wt% to 3 wt%, the real part of the complex permittivity increases for all frequencies examined (75-110 GHz). Similar behavior was observed for the imaginary part of the complex permittivity when measured in the W-band at all concentrations (Figure 30). Figure 31 shows that as the carbon nanotube concentration in the composition increases from 0.05 wt% to 3 wt%, the attenuation constant (in dB / cm) becomes more negative (higher attenuation) for all W-band frequencies examined. The percent absorbed power measured in transmission mode increases with carbon nanotube concentration up to a certain loading, after which it decreases across at least a portion of the W-band frequency range examined (Figure 32).

[0145] The foregoing is intended to be illustrative, not limiting. For example, the above examples (or one or more aspects thereof) may be used in combination with each other. Other aspects may be used, for example, as one of ordinary skill in the art may consider the above. The Abstract is provided to enable the reader to quickly ascertain the nature of the technical disclosure in accordance with 37 CFR §1.72(b). 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. However, no unclaimed disclosed feature should be construed as intended as essential to any claim. Rather, inventive subject matter may lie in fewer than all features of a particular disclosed embodiment. Thus, it is contemplated that the appended claims are incorporated into the Detailed Description as examples or aspects, with each claim standing on its own as a separate embodiment, and that such embodiments can be combined with each other in various combinations or permutations. The scope of the present disclosure should preferably be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. a thermoplastic polymer component comprising a polyester; greater than 0.10 wt % to 1.95 wt % of a carbon nanotube (CNT) filler, based on the total weight of the composition; a polycarbonate-siloxane copolymer; A thermoplastic composition comprising: A composition having a percent absorbed power measured in transmission mode of at least 60% when a 6 inch (in) x 8 in x 1 / 8 inch molded sample of said composition is observed at a frequency of 77 GHz according to the free space method.

2. 10. The thermoplastic composition of claim 1, wherein the polyester comprises polybutylene terephthalate (PBT), polyethylene terephthalate (PET), poly(cyclohexylene dimethylene terephthalate) (PCT), polyethylene terephthalate glycol (PETG), polycyclohexylene dimethylene terephthalate glycol (PCTG), polycyclohexylene dimethylene terephthalic acid (PCTA), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymers thereof, or combinations thereof.

3. The thermoplastic composition of claim 1 , wherein the composition comprises polybutylene terephthalate (PBT).

4. The CNT filler has an average diameter of 5 to 15 nanometers (nm) and a density of at least 100 square meters per gram (m ２ / g) surface area, and 10 －３ 10. The thermoplastic composition of claim 1, having a volume resistivity of less than ohm.centimeter (Ω.cm).

5. At least 1.0 x 10 １１ 10. The thermoplastic composition of claim 1 having a volume electrical resistivity of Ω.cm.

6. 10. The thermoplastic composition of claim 1, wherein a 6 in x 8 in x 1 / 8 in molded sample of the composition has a percent absorbed power measured in transmission mode of at least 60% when observed at frequencies from 75 GHz to 110 GHz according to the free space method.

7. The thermoplastic composition of claim 1, comprising greater than 0.25 wt% and less than 1 wt% CNT filler, based on the total weight of the composition, wherein a 6 in x 8 in x 1 / 8 in molded sample of the composition has a percent absorbed power measured in transmission mode of at least 74% when observed at a frequency of 77 GHz according to the free space method.

8. The thermoplastic composition of claim 1, comprising greater than 0.25 wt % to 1.95 wt % CNT filler, based on the total weight of the composition, wherein a molded sample of the composition has an attenuation constant of at least -30 dB / cm when observed at a frequency of 77 GHz according to the free space method.

9. 10. The thermoplastic composition of claim 1, further comprising at least one additional additive, wherein the at least one additional additive comprises an acid scavenger, an anti-drip agent, an antioxidant, an anti-static agent, a colorant, a demolding agent, a flow promoter, a lubricant, a mold release agent, a plasticizer, a quenching agent, a flame retardant, a UV reflective additive, an impact modifier, a blowing agent, a reinforcing agent, or a combination thereof.

10. An article comprising the thermoplastic composition of any one of claims 1 to 9.

11. 11. The article of claim 10, which is a microwave absorber for an internal or external radar sensor.

12. 11. The article of claim 10, which is a microwave absorber for a radar sensor, a camera, or an electronic control unit.

13. 11. The article of claim 10, comprising a transmitting antenna, a receiving antenna, and at least two openings that allow transmission of microwave radiation between the transmitting antenna and the receiving antenna.

14. combining a thermoplastic polymer component comprising a polyester with greater than 0.10 wt % to 1.95 wt %, based on the total weight of the composition, of a carbon nanotube (CNT) filler and a polycarbonate-siloxane copolymer to form a mixture; molding the mixture to form a thermoplastic composition; 1. A method of forming a thermoplastic composition comprising: wherein a 6 in x 8 in x 1 / 8 in molded sample of said thermoplastic composition has a percent absorbed power measured in transmission mode of at least 60% when observed at a frequency of 77 GHz according to the free space method.

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