Coating composition, non-conductive coating, non-conductive film, article thereof, method of making same, and method of using same

Abstract

The present disclosure provides coating compositions, non-conductive coatings, non-conductive films, articles thereof, methods of manufacture thereof, and methods of use thereof. The coating composition includes a film-forming resin and a conductive additive. A coating formed from the coating composition has an irreversible increase in resistivity of at least 20%, at least 50%, at least 100%, at least 500%, at least 1,000%, at least 10,000%, at least 100,000%, or at least 300,000%, all as measured with a probe before and after exposure to an external stimulus.

Description

Technical Field

[0001] This disclosure relates to coating compositions, non-conductive coatings, non-conductive films, articles thereof, methods of manufacturing thereof, and methods of using thereof. Background Technology

[0002] The use of radar is becoming ubiquitous in modern transportation, including in buses equipped with advanced driver assistance systems (ADAS) such as adaptive cruise control (ACC) and automatic braking. As autonomous driving advances further, radar usage is likely to increase. However, radar performance can be affected by unintended radar signal loss caused by bumpers or rearview mirror housings (where radar may be located). Manufacturing systems and components to minimize radar interference can be challenging. Summary of the Invention

[0003] This disclosure may include a coating composition comprising a film-forming resin and a conductive additive, wherein the coating formed by the coating composition has an irreversible increase in resistivity of at least 20%, as measured with an ohmmeter probe before and after exposure of the coating to an external stimulus. In some aspects, the coating formed by the coating composition has an irreversible increase in resistivity of at least 20%, at least 50%, at least 100%, at least 500%, at least 1,000%, at least 10,000%, at least 100,000%, or at least 300,000%, all as measured with an ohmmeter probe before and after exposure to an external stimulus.

[0004] This disclosure also relates to coatings or films produced by a curing coating composition. The coating composition comprises a film-forming resin and a conductive additive. The coating formed from the coating composition has an irreversible increase in resistivity of at least 20%, at least 50%, at least 100%, at least 500%, at least 1,000%, at least 10,000%, at least 100,000%, or at least 300,000%, all as measured by probes before and after exposure to an external stimulus.

[0005] This disclosure may also include an article comprising a substrate; and a non-conductive coating or non-conductive film formed on the substrate, wherein: the non-conductive coating or film comprises a film-forming resin and a conductive additive having been subjected to external stimulation; the non-conductive coating or film transmits 20% or more of electromagnetic radiation with frequencies ranging from 1 GHz to 300 GHz through the coating or film. In some aspects, the non-conductive coating or non-conductive film is formed by applying external stimulation to a coating or film produced by a cured coating composition. The coating composition may further comprise a film-forming resin and a conductive additive. The coating formed from the coating composition may have an irreversible increase in resistivity of at least 20%, at least 50%, at least 100%, at least 500%, at least 1,000%, at least 10,000%, at least 100,000%, or at least 300,000%, all as measured by probes before and after exposure to external stimulation.

[0006] This disclosure may further include a method for manufacturing an article of articles, wherein the method may include: applying a coating composition to a substrate, wherein the coating comprises a film-forming resin and a conductive additive; curing and / or drying the coating composition on the substrate to form a self-supporting coating; and subjecting the self-supporting coating to an external stimulus to form a coating layer on the substrate; wherein the coating layer is non-conductive and transmits 20% or more of electromagnetic radiation, including frequencies from 1 GHz to 100 GHz, through the non-conductive coating. In some aspects, the coating formed from the coating composition has an irreversible increase in resistivity of at least 20%, at least 50%, at least 100%, at least 500%, at least 1,000%, at least 10,000%, at least 100,000%, or at least 300,000%, all as measured by a probe before and after exposure to the external stimulus. The method includes drying and / or curing the coating composition on the substrate to form a self-supporting coating. The method includes subjecting the self-supporting coating to an external stimulus to form a coating layer on the substrate.

[0007] This disclosure also relates to a method for improving radio detection and ranging of an automotive radar sensor mounted behind a coated article in the electromagnetic radiation frequency range of 1 GHz to 300 GHz (such as 1 GHz to 100 GHz or 76 GHz to 81 GHz). The method includes applying a coating and / or film formed of a coating composition to an automotive substrate. The coating composition comprises a film-forming resin and conductive additives. The coating formed by the coating composition has an irreversible increase in resistivity of at least 20%, at least 50%, at least 100%, at least 500%, at least 1,000%, at least 10,000%, at least 100,000%, or at least 300,000%, all as measured by probes before and after exposure to external stimuli.

[0008] It should be understood that this disclosure is not limited to the examples outlined in this invention. Various other aspects are described and illustrated herein. Attached Figure Description

[0009] The features and advantages of the example, as well as the way in which it is implemented, will become more apparent and the example will be better understood by referring to the following description in conjunction with the accompanying drawings, wherein:

[0010] Figure 1 This is a schematic diagram of a radar transmission system according to the present disclosure.

[0011] The examples listed herein illustrate certain non-limiting embodiments in one form, and such examples should not be construed as limiting the scope of the appended claims in any way. Detailed Implementation

[0012] In many previous applications, radar systems were located behind covers (such as radomes, bumpers, or rearview mirror housings) to ensure the desired aesthetics and / or protection of the radar system. However, radar performance can be affected by unintended radar signal transmission and reception losses caused by the covers (including coatings on the covers).

[0013] A prior coating layer is applied to the substrate using various methods, such as electrodeposition and electrostatic assisted application. These methods utilize electrical charge to assist the deposition of the prior coating composition onto the substrate to form the prior coating layer. The substrate may be negatively charged, and the prior coating composition may be positively charged, causing the prior coating composition to be attracted to the substrate and form a uniform coating on the substrate. Some substrates may be non-conductive (e.g., non-conductive polymer-based substrates), and it may be necessary to deposit a prior conductive coating onto the substrate before the electrodeposition process so that the prior conductive coating can be used to form a negative charge. However, this prior conductive coating may affect radar transmission. To compensate for radar signal loss, prior electrodeposition or electrostatic assisted application may be avoided, and / or a more powerful radar system may be adopted, which may lead to increased manufacturing costs, changes in the performance of the deposited coating, and / or changes in the size of the radar system.

[0014] This disclosure provides coating compositions, non-conductive coatings, non-conductive films, articles thereof, methods of manufacturing thereof, and methods of using thereof, which can achieve desired aesthetics, desired manufacturing processes, and / or reduced radar transmission loss. For example, the coating composition can be deposited on a substrate and self-supported to form a self-supporting coating and / or self-supporting film having a first resistivity suitable for assisted electrodeposition and / or electrostatic assisted application of subsequent coating layers to form a coating system. The coating and / or film can be exposed to external stimuli, causing the first resistivity to increase irreversibly, thereby reducing the radar transmission loss of the resulting coating system.

[0015] The coating composition according to this disclosure comprises a film-forming resin and a conductive additive. This coating composition can form a coating and / or film suitable for assisted electrodeposition and / or electrostatic application of subsequent coating layers.

[0016] The coating composition may contain an amount of conductive additive suitable for forming a coating having a first resistivity suitable for assisting electrodeposition and / or electrostatic application of the coating composition itself and / or subsequent coating layers. The range of the first resistivity may vary depending on the application and desired efficiency. The first resistivity may be 30 ohms × cm or less, such as 25 ohms × cm or less, 20 ohms × cm or less, 15 ohms × cm or less, 10 ohms × cm or less, or 5 ohms × cm or less. The coating composition may contain at least 0.01% by weight of conductive additive, such as, for example, at least 0.1% by weight, at least 0.5% by weight, at least 1% by weight, at least 2% by weight, at least 5% by weight, or at least 10% by weight, all based on the total weight of the coating composition. The coating composition may contain no more than 30% by weight of conductive additive, such as, for example, no more than 20% by weight, no more than 15% by weight, no more than 10% by weight, no more than 5% by weight, or no more than 2% by weight, all based on the total weight of the coating composition. For example, the coating composition may contain conductive additives ranging from 0.01% to 30% by weight, such as, for example, 0.1% to 20% by weight, 0.5% to 20% by weight, 1% to 20% by weight, or 1% to 10% by weight, all based on the total weight of the conductive additives.

[0017] Conductive additives can affect the conductivity of a coating composition (e.g., increase the conductivity of the coating composition compared to the same coating without the additive). For example, conductive additives may include carbon; metals, particularly conductive metals, such as metal alloys and metal oxides; conductive polymers, or combinations thereof. Carbon may include carbon black, carbon fibers, carbon nanotubes, graphene, or combinations thereof. Metals or metal alloys may include aluminum, aluminum alloys, silver, silver alloys, copper, copper alloys, nickel, nickel alloys, or combinations thereof (e.g., silver-plated copper). Metal oxides may include indium tin oxide, nickel oxide, zinc oxide, chromium oxide, their doped forms, or combinations thereof. Various dopants can be used. For example, the dopant for zinc oxide is aluminum. Conductive polymers may include poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PDOT:PSS), polythiophene, polyaniline, polyphenylene ether, polypyrrole, polyacetylene, or combinations thereof.

[0018] The coating composition may contain an amount of film-forming resin suitable for forming a coating and / or film on the surface of a substrate. For example, the coating composition may contain at least 20% by weight of film-forming resin based on the total weight of the coating composition, such as, for example, at least 25% by weight or at least 30% by weight, all based on the total weight of the coating composition. The amount of film-forming resin and / or conductive additives may be adjusted based on the desired application and the presence of solvents and / or other additives.

[0019] Film-forming resins may include resins that, upon removal of any diluent or carrier during physical drying and / or curing at ambient or high temperatures, can form a self-supporting (e.g., capable of maintaining as a material film with defined thickness, length, and width, and retaining this state in the absence of a supporting substrate) continuous film. As used herein, “film-forming resin” means self-crosslinking resins, resins crosslinked by reaction with a crosslinking agent, resins that form solid films by solvent evaporation, and mixtures thereof.

[0020] As used herein, the term "curing" refers to the chemical crosslinking of components in a coating composition applied as a layer to a substrate. Therefore, the term "curing" does not encompass the physical drying of the coating composition solely by solvent or carrier evaporation. In this regard, the term "cured" as used herein refers to the state of a layer in which the components of the coating composition forming the layer undergo a chemical reaction to form new covalent bonds within the layer (e.g., new covalent bonds between the adhesive resin and the curing agent).

[0021] Film-forming resins may include at least one of thermosetting film-forming resins and / or thermoplastic film-forming resins. As used herein, the term "thermosetting" refers to a resin that irreversibly "solidifies" upon curing or crosslinking, wherein the polymer chains of the polymer components are linked together by covalent bonds, typically induced, for example, by heat or radiation, to form a three-dimensional network. The curing or crosslinking reaction may be carried out under ambient conditions (e.g., ambient temperature and atmospheric pressure (e.g., 1 atmosphere)). Once cured or crosslinked, thermosetting film-forming resins may not melt upon heating and may be insoluble in common solvents (e.g., less than 0.001 g of material may dissolve in 1 g of a given solvent after 24 hours at 20°C). As used herein, the term "thermoplastic" refers to a resin comprising polymer components not linked by covalent bonds to form a three-dimensional network, and thus capable of undergoing liquid flow upon heating, and is typically soluble in common solvents (e.g., at least 0.1 g of material may dissolve in 1 g of a given solvent after 24 hours at 20°C).

[0022] The film-forming resin (e.g., in examples of thermosetting coating compositions) may further comprise a crosslinking agent, such as, for example, amino plastics, polyisocyanates (including blocked isocyanates and blocked polyisocyanates), polyepoxides, β-hydroxyalkylamides, polybasic acids, acid anhydrides, organometallic acid functionalized materials, polyamines, polyamides, or combinations thereof.

[0023] The film-forming resin may have functional groups that react with the crosslinking agent. The film-forming resin in the coating compositions described herein may be selected from any of a variety of polymers. The film-forming resin may comprise acrylic polymers, epoxy polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyether polymers, polysiloxane polymers, copolymers thereof, or combinations thereof. The film-forming resin may contain a backbone of at least 10 carbon chains (e.g., at least 10 carbon atoms between ester bonds), such as at least 12 carbon chains. Typically, these polymers can be any of these types of polymers prepared by various methods.

[0024] The functional groups on the film-forming resin can be selected from any reactive functional group of various reactive functional groups, including, for example, carboxylic acid groups, amine groups, epoxy groups, hydroxyl groups, thiol groups, urethane groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), or combinations thereof. For example, the functional groups on the film-forming resin may include hydroxyl and carboxylic acid groups.

[0025] The coating composition may include a positive temperature coefficient (PTC) resin, the physical properties of which (i.e., phase, shape, morphology, or combination thereof) change in response to external stimuli. The PTC resin may include 1,2-propanediol. Changes in the physical properties of the PTC resin, i.e., changes in phase, shape, morphology, or combination thereof, can affect the electrical conductivity of the coating formed therefrom. For example, the PTC resin may be in a contracted state, wherein the average distance between the conductive particles is suitable to give the coating formed therefrom a desired resistivity. After the coating formed therefrom is subjected to external stimuli, the PTC resin may be in an expanded state, wherein the average distance between the conductive particles increases, resulting in an increase in the resistivity of the coating formed therefrom.

[0026] PTC resin can be a polyester polymer comprising a backbone containing at least 10 consecutive carbon atoms between ester bonds (the amount of consecutive carbon atoms includes carbon atoms forming a portion of the ester bonds), such as at least 12 consecutive carbon atoms between ester bonds, such as at least 14, at least 16, at least 18, or at least 20 consecutive carbon atoms. The backbone having a continuous carbon chain may include repeating carbon-containing units, such as consecutive methylene groups. The backbone having a continuous carbon chain may contain a mixture of carbon-containing units, such as a mixture of methylene and carbonyl groups.

[0027] Polyester polymers may contain the following chemical structures:

[0028]

[0029] Where n≥1, X is incorporated through any polyol, and R is any component, including H.

[0030] Polyester polymers may contain the following chemical structures:

[0031]

[0032] Where n≥1, Y is derived from any polybasic acid (including polybasic acid halides), polyester, etc., and R is any component, including H.

[0033] Polyester polymers can have a linear structure. As used herein, the term "linear structure" refers to a linear polymer that does not contain branches formed from the straight chain. Polyester polymers can be substantially unbranched, such that the degree of branching in a polyester polymer is less than 50% lower than that of a fully linear polyester polymer, reducing endothermic (glass transition endothermic or melting endothermic) levels. Glass transition endothermic and melting endothermic measurements were performed according to ASTM D3418. To determine glass transition endothermic or melting endothermic, each sample was sealed in an aluminum disc and scanned twice in the TA INSTRUMENTS DISCOVERY DSC at a rate of 10 °C / min from -30 °C to 250 °C. The DSC was calibrated using indium, tin, and zinc standards and purged with a nominal nitrogen purging rate of 50 ml / min. The half-maximum glass transition temperature (Tg) was determined at two points, and the peak area was determined using a linear baseline.

[0034] Polyester polymers may include non-aromatic polyester polymers. As used herein, the term "non-aromatic polyester polymer" refers to a polyester polymer that does not contain aromatic groups. As used herein, the term "aromatic group" refers to a cyclic planar molecule with resonant rings that exhibits greater stability than other geometric or interconnected arrangements with the same atomic set.

[0035] Polyester polymers may include saturated polyester polymers. As used herein, the term "saturated polyester polymer" refers to a polyester polymer in which all atoms except ester bonds are linked by single bonds. Polyester polymers may also be unsaturated polyester polymers having one or two degrees of unsaturation in addition to ester bonds.

[0036] Polyester polymers may include semi-crystalline polyester polymers. As used herein, the term "semi-crystalline polyester polymer" refers to a polyester polymer containing both crystalline and amorphous regions.

[0037] Polyester polymers may include bio-based polyester polymers. As used herein, the term "bio-based polyester polymer" refers to a polyester polymer prepared at least in part from bio-based monomers. Polyester polymers may be prepared using diacid monomers derived from plants or vegetable oils. Polyester polymers may be prepared using polyols derived from plants or vegetable oils. Polyester polymers may be prepared using glycerol as a polyol.

[0038] Polyester polymers can be prepared by reacting a polyacid component and / or a polyester component with a polyol component. The polyacid component may include diacid monomers. The polyacid component may include polyacid halides. The polyester component may include diester monomers.

[0039] As used herein, the term "polyacid" refers to a compound having two or more acid or acid equivalent groups (or combinations thereof), and includes esters and / or anhydrides of acids. "Acid equivalent group" means that a non-double-bonded oxygen atom in an acid group has been replaced by another component (such as a halide component). Therefore, a polyacid can include polyacid halides or other polyacid equivalents. "Diacid" refers to a compound having two acid groups, including esters and / or anhydrides of diacids. As used herein, the term "polyester" refers to a compound having two or more ester groups. "Diester" refers to a compound having two ester groups. As used herein, the term "polyol" refers to a compound having two or more hydroxyl groups.

[0040] Polyester polymers can be the reaction product of a polyol and a polyacid (e.g., a diacid), the polyacid comprising at least 10 consecutive carbon atom chains, such as at least 12, at least 14, at least 16, at least 18, or at least 20 consecutive carbon atom chains. Polyester polymers can also be the reaction product of a polyol and a polyester (e.g., a diester), the polyester comprising at least 10 consecutive carbon atom chains, such as at least 12, at least 14, at least 16, at least 18, or at least 20 consecutive carbon atom chains. Polyester polymers can also be the reaction product of a polyol comprising at least 12 consecutive carbon atom chains, such as at least 14, at least 16, at least 18, or at least 20 consecutive carbon atom chains, and a polyester or a polyacid. Therefore, polyester polymers can comprise polyester polyol polymers and / or polyester polyacid polymers.

[0041] Suitable polyacids for preparing polyester polymers include, but are not limited to, saturated polyacids such as adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, octadecanoic acid, hexadecanoic acid, tetradecanoic acid, sebacic acid, dodecanoic acid, cyclohexanediol, hydrogenated C36 dimer fatty acids and their esters and anhydrides. Suitable polyacids include polyacid halides. Polyacids may comprise 20 to 80% by weight of the reaction mixture, such as 30 to 70% by weight or 40 to 60% by weight. Any combination of these polyacids may be used.

[0042] Suitable polyesters for preparing polyester polymers include, but are not limited to, esters of the aforementioned suitable polybasic acids. The polyester may comprise 20 to 80% by weight of the reaction mixture, such as 30 to 70% by weight or 40 to 60% by weight. Any combination of these polyesters may be used.

[0043] Suitable polyols for preparing polyester polymers include, but are not limited to, any known polyols used for preparing polyesters. Examples include, but are not limited to, alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,2-propanediol, triethylene glycol, tripropylene glycol, hexanediol, polyethylene glycol, polypropylene glycol, and neopentyl glycol; hydrogenated bisphenol A; cyclohexanediol; propylene glycol, including 1,2-propanediol, 1,3-propanediol, butyl ethyl propylene glycol, 2-methyl-1,3-propanediol, and 2-ethyl-2-butyl-1,3-propanediol; butanediol, including 1,4-butanediol, 1,3-butanediol, and 2-ethyl-1,4-butanediol; pentanediol, including triethylene glycol, ethylene glycol, dipropylene glycol, dipropylene glycol, 1,2-propanediol, triethylene glycol, tripropylene glycol, hexanediol, polyethylene glycol, polyethylene glycol, polypropylene glycol, and neopentyl glycol; hydrogenated bisphenol A; cyclohexanediol; propylene glycol, including 1,2-propanediol, 1,3-propanediol, butyl ethyl propylene glycol, 2-methyl-1,3-propanediol, and 2-ethyl-2-butyl-1,3-propanediol; butanediol, including 1,4-butanediol, 1,3-butanediol, and 2-ethyl-1,4-butanediol; pentanediol, including triethylene glycol, butyl ethyl propylene glycol, butyl ethyl propylene glycol, butyl ethyl propylene glycol, butyl ethyl propylene glycol, butyl ethyl propylene glycol, butyl ethylene glycol, butyl propylene glycol, butyl propylene glycol, butyl propylene glycol, butyl propylene glycol, butyl propylene glycol, butyl propylene glycol, butyl propylene glycol, butyl propylene glycol, butyl Methylpentanediol and 2-methylpentanediol; 2,2,4-trimethyl-1,3-pentanediol, cyclohexanediol; hexanediol, including 1,6-hexanediol; 2-ethyl-1,3-hexanediol, caprolactone diol (e.g., the reaction product of ε-caprolactone with ethylene glycol); hydroxyalkylated bisphenols; polyether glycols, such as poly(oxytetramethylene) glycol; trimethylolpropane, di-trimethylolpropane, pentaerythritol, dipentaerythritol, trimethylolethane, trimethylolbutane, dimethylolcyclohexane, glycerol, tri(2-hydroxyethyl)isocyanurate, etc.

[0044] Any combination of these polyols can be used to form at least one polyester polymer for use in conductive polymer compositions. Conductive polymer compositions may include a variety of different types of polyester polymers, each prepared using a different polyol and / or combination of polyols. Conductive polymer compositions may include a single type of polyester polymer, with the prepared polyester polymer comprising a variety of different types of polyols. Polyol combinations (used to prepare one or more polyester polymers contained in the conductive polymer composition) may include, but are not limited to, at least one of 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 1,6-hexanediol.

[0045] The solid hydroxyl value of the polyester polymer can be from 5 to 120 mg KOH / g, such as 10 to 100 mg KOH / g as measured according to ASTM D4274-16. The solid acid value of the polyester polymer can be from 5 to 120 mg KOH / g, such as 10 to 100 mg KOH / g as measured according to ASTM D4662-15. The average molecular weight (Mn) of the polyester polymer can be from 1,000 to 15,000 g / mol, such as 1,500 to 10,000 g / mol, such as 2,000 to 8,000 g / mol. The weight-average molecular weight (Mw) of the polyester polymer can be from 1,000 to 90,000 g / mol, such as 1,500 to 60,000 g / mol, such as 2,000 to 48,000 g / mol, such as 3,000 to 30,000 g / mol. Mn and Mw can be measured by gel permeation chromatography relative to linear polystyrene standards ranging from 580 to 2,698,000 g / mol, such as by using a WATERS 2695 separation module with a WATERS 2414 differential refractometer (RI detector), with tetrahydrofuran (THF) as the eluent, at a flow rate of 1 ml / min, and separated using two PLgel Mixed C (300 x 7.5 mm) columns at room temperature.

[0046] The polyester polymer (in the conductive polymer composition) can itself be a non-conductive polymer.

[0047] The polyester polymer, PTC resin, may comprise at least 5% by weight of the total weight of the coating composition, such as at least 10%, at least 20%, or at least 30% by weight. The polyester polymer may comprise up to 40%, 50%, 60%, 70%, or 80% by weight of the total weight of the coating composition, such as 90% by weight. The polyester polymer may comprise 5 to 40% by weight of the coating composition, such as 10 to 30% by weight or 10 to 20% by weight.

[0048] The polyester polymer, PTC resin, may comprise at least 5% by weight, such as at least 10%, at least 20%, or at least 30% by weight, of the coating composition based on total solids (non-volatile fraction). The polyester polymer may comprise up to 90% by weight, such as up to 85% by weight, or up to 75% by weight, of the coating composition based on total solids. The polyester polymer may comprise 5 to 90% by weight, such as 10 to 85% by weight, or 20 to 85% by weight, of the coating composition based on total solids.

[0049] Polyester polymers can be included in coating compositions along with other polymers. Polyester polymers can be incorporated as segments of the polymer included in the coating composition. For example, polyester polymers can react with isocyanates to form polyurethane polymers containing polyester polymers as segments (still polyester polymers). The polyester segments of the polyurethane polymer will still cause the polymer to have PTC properties because the polyester segments will still expand at certain temperatures.

[0050] The coating composition may further comprise a crosslinking inhibitor. The crosslinking inhibitor inhibits (if it cannot prevent) the crosslinking of the film-forming resin. The crosslinking inhibitor can be used to control the curing conditions of the film-forming resin. In response to an external stimulus, the crosslinking inhibitor may be at least partially deactivated (including by removal, degradation, reaction, or a combination thereof), reducing its ability to inhibit (if it cannot prevent) the crosslinking of the film-forming resin. After the inhibition ability is reduced, the coating composition can be cured. For example, the crosslinking inhibitor can inhibit the curing of PTC resin in a contracted state and promote the curing of PTC resin in a swollen state, resulting in an irreversible increase in the resistivity of the coating.

[0051] Crosslinking inhibitors may comprise solvents, acids, bases, metal chelating agents, or combinations thereof. For example, crosslinking inhibitors may comprise dimethylethanolamine, propionic acid, acetic acid, amines, ammonia, acetylacetone, thiols, or combinations thereof.

[0052] The coating composition may contain additional components such as, for example, pigments, plasticizers, abrasion-resistant particles, film-reinforcing particles, flow control agents, thixotropic agents, rheology modifiers, cellulose acetate butyrate, catalysts, antioxidants, bactericides, defoamers, surfactants, wetting agents, dispersants, adhesion promoters, clay, hindered amine light stabilizers, UV absorbers and / or stabilizers, stabilizers, fillers, organic solvents, water, reactive diluents, abrasive carriers, or combinations thereof.

[0053] This coating composition can form a coating and / or film suitable for assisted electrodeposition and / or electrostatic application of subsequent coating layers. The coating composition can be formulated as a solvent-based composition, a water-based composition, or a 100% solid (i.e., non-volatile) composition excluding volatile solvents (e.g., readily evaporable at ambient temperature) or an aqueous carrier. For example, the coating composition can be formulated as a liquid, paste, slurry, or powder depending on the desired application. The coating composition can be liquid at temperatures of -10°C or higher, such as, for example, 0°C or higher, 10°C or higher, 30°C or higher, 40°C or higher, or 50°C or higher. The coating composition can be liquid at temperatures of 60°C or lower, such as, for example, 50°C or lower, 40°C or lower, 30°C or lower, 10°C or lower, or 0°C or lower. The coating composition can be liquid in a temperature range of -10°C to 60°C, such as, for example, -10°C to 50°C, -10°C to 40°C, -10°C to 30°C, or 0°C to 40°C. The coating composition may be liquid at ambient temperature.

[0054] As used in this article, “ambient temperature” refers to a temperature of 23℃ + / -3℃.

[0055] This disclosure provides a method for manufacturing a radar transmission system, the system comprising a coating formed of a coating composition. The method may include applying the coating composition according to this disclosure onto a first surface of a substrate. The coating composition may be applied using at least one of electrodeposition, electrostatic assisted application, spraying, spin coating, dip coating, roll coating, flow coating, slot die coating, brush coating, in-mold coating, thin film coating, extrusion, dot coating (e.g., strip dot coating), or combinations thereof. The coating composition may be formed as a preformed film and then applied to at least a portion of the substrate.

[0056] As used herein, the terms “on,” “applied to,” “formed on,” “deposited on,” “covered,” “provided on,” etc., mean to be formed, covered, deposited, or provided on a surface but not necessarily in contact with the surface. For example, a layer formed “applied to a substrate layer” does not exclude the presence of one or more other layers of the same or different composition located between the formed layer and the substrate layer.

[0057] The substrate may be at least partially coated with a coating composition. For example, the coating composition according to this disclosure may be applied to 1% or more of the first surface of the substrate layer, such as, for example, 10% or more, 20% or more, 50% or more, 70% or more, 90% or more, or 99% or more of the first surface of the substrate. The coating composition according to this disclosure may be applied to 100% or less of the first surface of the substrate layer, such as, for example, 99% or less, 90% or less, 70% or less, 50% or less, 20% or less, or 10% or less of the first surface of the substrate. The coating composition according to this disclosure may be applied to 1% to 100% of the first surface of the substrate, such as, for example, 5% to 99%, 5% to 90%, 5% to 70%, 5% to 20%, or 50% to 100% of the first surface of the substrate.

[0058] After the coating composition is applied to the substrate, it may be allowed to coalesce to form a substantially continuous film on the substrate, and the coating composition may be cured and / or dried to form a first self-supporting coating.

[0059] The first self-supporting coating can be a coating, a film, or a combination thereof. As used herein, a "coating" is a surface covering such as a paint applied to at least a portion of an object, which may be applied in the form of a liquid, paste, slurry, or powder, and after drying and / or curing, forms a self-supporting continuous film over at least a portion of the object. A film is a surface covering applied as a solid and flexible layer to at least a portion of an object, which is cured and / or dried before being applied to at least a portion of the object. The first self-supporting coating can be a pretreatment layer, an adhesion promoter layer, a primer layer, an intermediate layer, a topcoat layer, a base coat layer, or a combination thereof.

[0060] [1] A second coating composition may be applied onto a first self-supporting coating. The second coating composition may be deposited using at least one of electrodeposition and electrostatic-assisted application, such that during at least a portion of the application of the second coating composition, the first self-supporting coating is charged (e.g., negatively charged) and the second coating composition is charged (e.g., positively charged). The application of the second coating composition may occur before subjecting the first self-supporting coating to external stimuli. After the second coating composition is applied onto the first self-supporting coating, the second coating composition may be allowed to coalesce to form a substantially continuous film on the cured coating, and the second coating composition may be cured to form a second cured coating.

[0061] The first self-supporting coating may be exposed to external stimuli such that the resistivity of the first self-supporting coating composition may irreversibly increase. The resistivity of the first self-supporting coating may irreversibly increase by at least 20%, at least 50%, at least 100%, at least 500%, at least 1,000%, at least 10,000%, at least 100,000%, or at least 300,000%, all as measured by probes before and after exposing the coating to external stimuli. For example, the resistivity of the first self-supporting coating may irreversibly increase by at least 0.5 ohms × cm, such as at least 0.75 ohms × cm, at least 1 ohm × cm, at least 2 ohms × cm, at least 10 ohms × cm, at least 50 ohms × cm, at least 100 ohms × cm, at least 500 ohms × cm, at least 1 kΩ × cm, at least 100 kΩ × cm, at least 500 kΩ × cm, or at least 1 mohm × cm, all as measured by four-point probes after exposing the coating to external stimuli. For example, the first resistivity of the first self-supporting coating can be increased to a second resistivity. The second resistivity can be non-conductive. As used herein, "non-conductive" means that the element contains a resistivity of at least 1 ohm × cm (as measured with a four-point probe), such as, for example, at least 1.5 ohm × cm, at least 2 ohm × cm, or at least 5 ohm × cm, at least 10 ohm × cm, at least 50 ohm × cm, at least 100 ohm × cm, at least 500 ohm × cm, at least 1 kΩ × cm, at least 100 kΩ × cm, at least 500 kΩ × cm, or at least 1 mohm × cm, all as measured with a four-point probe.

[0062] As used herein, "irreversible" and "irreversibly" when referring to the resistivity of a coating mean that the resistivity does not return to its previous resistivity after the removal of the external stimulus. For example, a self-supporting coating has a first resistivity before the external stimulus, and the resistivity of the self-supporting coating increases after the first self-supporting coating is subjected to the external stimulus. After the removal of the external stimulus, the resistivity of the self-supporting coating may change over time, but the resistivity of the self-supporting coating will not return to the first resistivity and may remain at least 0.5 ohms × cm higher than the first resistivity, such as at least 0.75 ohms × cm, at least 1 ohm × cm, at least 2 ohms × cm, at least 10 ohms × cm, at least 50 ohms × cm, at least 100 ohms × cm, at least 500 ohms × cm, at least 1 kΩ × cm, at least 100 kΩ × cm, at least 500 kΩ × cm, or at least 1 mohm × cm higher than the first resistivity.

[0063] External stimuli may include heat, photochemical radiation (e.g., particle radiation and / or electromagnetic radiation), electric current, application of chemical reagents, other stimuli used to interrupt permeation or conductive pathways, or combinations thereof. External stimuli may be applied in a time and / or amount that irreversibly increases the resistivity of the coating and / or coating composition while substantially maintaining desired aesthetics (e.g., appearance, color) and mechanical properties. Aesthetics may also include surface roughness (which also affects mechanical properties), while mechanical properties typically include at least cohesive strength and adhesion to adjacent layers after the application of external stimuli. External stimuli may at least partially remove or degrade film-forming resins, conductive additives, crosslinking agents and / or crosslinking inhibitors, alter their phase, shape, and / or morphology.

[0064] As described above, the external stimulus can be applied for a time and / or amount that irreversibly increases the resistivity of the coating and / or coating composition and substantially maintains the desired aesthetics (e.g., appearance, color) and mechanical properties. The time can be from 0.0001 seconds to 12 hours, such as 0.001 seconds to 8 hours, and can vary depending on the external stimulus used. For example, when the stimulus is photochemical radiation or electric current, the stimulus can be applied for 0.0001 seconds to 4 hours, such as 0.0001 seconds to 2 hours, such as 0.0001 seconds to 1 hour, such as 0.0001 seconds to 30 minutes, such as 0.0001 seconds to 10 minutes, such as 0.001 seconds to 5 minutes. Further, when the external stimulus is heat, the time can be from 0.1 seconds to 12 hours, such as 1 second to 8 hours, such as 1 second to 4 hours, such as 1 second to 1 hour, such as 1 minute to 1 hour, and can vary depending on the temperature selected as the external stimulus.

[0065] It is understood that external thermal stimuli at more than one temperature may be effective, but lower temperatures may require a longer time to achieve a suitable irreversible increase in the resistivity of the coating and / or coating composition compared to higher temperatures. When the desired external stimulus is the application of a chemical reagent, the chemical reagent may remain in contact with the coating and / or coating composition, or the chemical reagent may have a removal mechanism, such as evaporation. In the presence of a removal mechanism, the contact time of the chemical reagent as an external stimulus may be at least 1 second, such as 10 seconds, such as 1 minute, such as 5 minutes, such as 10 minutes, such as 20 minutes, such as 30 minutes, and at most no more than 1 year, such as 6 months, such as 3 months, such as 1 month, such as 1 week, such as 1 day, such as 8 hours, such as 4 hours, such as 1 hour, or any range with any two of the above values ​​as endpoints, such as 1 second to 1 year, such as 10 seconds to 6 months, such as 1 minute to 8 hours, such as 1 minute to 1 hour.

[0066] [2] Exposing the first self-supporting coating to external stimulation may include heating the first self-supporting coating in an oven, with a hot air gun, a heating lamp, or other means. External stimulation may include heating the first self-supporting coating to a temperature of at least 30°C, such as at least 40°C, at least 50°C, at least 60°C, at least 70°C, or at least 80°C. External stimulation may include heating the first self-supporting coating to a temperature in the range of 30°C to 200°C, such as 40°C to 200°C, 50°C to 200°C, 60°C to 200°C, 60°C to 150°C, or 60°C to 120°C. For example, in examples including coating compositions comprising a PTC resin, a crosslinking agent, and a crosslinking inhibitor, the coating composition may be applied to a surface and then dried to form a self-supporting coating. Heating may then at least partially remove and / or degrade the crosslinking inhibitor in the self-supporting coating at a desired temperature, such that the PTC resin is substantially fixed in an expanded state by the curing of the self-supporting coating.

[0067] Exposing the first self-supporting coating to external stimuli may include irradiating the first self-supporting coating with a particle radiation source. Particle radiation may include ionizing radiation, such as alpha radiation, beta radiation, gamma radiation, or combinations thereof. For example, particle radiation may degrade crosslinking inhibitors and / or conductive additives.

[0068] Exposing the first self-supporting coating to external stimuli may include irradiating the first self-supporting coating with an electromagnetic source (such as, for example, a lamp, LED, laser diode, other electromagnetic source, or a combination thereof). For example, electromagnetic radiation may include ultraviolet radiation (e.g., 100 nm to 400 nm), visible radiation (e.g., 400 nm to 700 nm), infrared radiation (e.g., 700 nm to 1 mm), or a combination thereof. For example, electromagnetic radiation may degrade crosslinking inhibitors and / or conductive additives.

[0069] Exposing the first self-supporting coating to external stimuli may include applying an electric current to the first self-supporting coating using a power source (such as, for example, direct current (DC) and / or alternating current (AC)). The electrical power used in the external stimuli may be greater than the electrical power used during the application of the second coating composition. For example, the current may degrade crosslinking inhibitors and / or conductive additives.

[0070] Exposing the first self-supporting coating to external stimuli may include applying a chemical reagent to the first self-supporting coating, thereby altering the chemical properties of the first self-supporting coating. For example, the chemical reagent may include water, acid, base, other chemical substances, or combinations thereof. Applying a chemical reagent may increase the water content of the first self-supporting coating; decrease the pH of the first self-supporting coating; increase the pH of the first self-supporting coating; alter the shape of the chemical structure in the first self-supporting coating; block electrical pathways in the first self-supporting coating; and / or otherwise affect the chemical structure and / or bonds in the first self-supporting coating, which may cause an irreversible increase in the resistivity of the first self-supporting coating. The application of the chemical reagent may be alone, or the chemical reagent may be present in the second coating composition and applied simultaneously with the second coating composition.

[0071] After the application of external stimuli, the first self-supporting coating can substantially maintain the desired aesthetics, surface roughness, cohesion, and adhesion to adjacent layers. It can be applied using the International Commission on Illumination (CIE) L... 15 Values ​​quantify the aesthetics of coatings, films, and / or articles, as described herein. CIE lab (or CIE Lch) color values ​​can be measured using a multi-angle spectrophotometer (such as the BYKMAC I from ALTANA) with D65 illumination and a 10° view, at measurement angles of 15°, 25°, 45°, 75°, and / or 110° relative to the mirror orientation. For example, a first self-supporting coating may have a CIELAB ΔE of 15 or less, such as 10 or less, 5 or less, or 2 or less, all as measured at 15° using a multi-angle spectrophotometer with D65 illumination and a 10° view, relative to the first self-supporting coating before the application of external stimulation. According to Formula 1, ΔE is the difference between two colors in the cIELAB color space based on the difference between the collected L, a, and b values.

[0072] Formula 1

[0073]

[0074] After being subjected to external stimuli, the first self-supporting coating maintains its adhesion to the substrate, adhesion to the topcoat, surface roughness, appearance, and / or color. The first self-supporting coating may not form bubbles or cracks after external stimuli.

[0075] Compared to the first self-supporting coating before the application of external stimulation, the first self-supporting coating may include 20 units or less of a change in surface roughness (DOI), as measured by BYK WAVESCAN. Compared to the first self-supporting coating before the application of external stimulation, the first self-supporting coating may include 2 units or less of a decrease in adhesion grade, as measured according to ASTM D3359-22 Test Method B at grades 0B-5B.

[0076] The coating compositions according to this disclosure can be selected based on the external stimulus to be used, or the external stimulus can be selected based on the coating composition according to this disclosure. The conductive additive may include carbon nanotubes and / or a conductive polymer configured to degrade in response to an external stimulus. The carbon nanotubes may be subjected to heating and / or electromagnetic radiation, wherein the crystal structure of the carbon nanotubes changes after the external stimulus. The carbon nanotubes may be modified with various chemical groups to alter their response to external stimuli and / or their conductivity. The conductive polymer may be subjected to ultraviolet radiation, which can disrupt the conductive chemical pathways within the polymer.

[0077] The figure shows a schematic diagram of a radar transmission system 100 disclosed herein, which includes a substrate 102, a first layer 104, and a second layer 106. The substrate 102 includes a first surface 102a and a second surface 102b positioned opposite to the first surface 102a. The first surface 102a and the second surface 102b may be parallel or non-parallel. In use, the second surface 102b may point towards the radar system 108.

[0078] To form the first layer 104, the coating composition according to this disclosure may be applied to at least a portion of the first surface 102a of the substrate 102 and cured and / or dried. To form the second layer 106, the second coating composition may be applied to at least a portion of the first surface 104a of the first layer 104. The second layer 106 may be a layer different from the first layer 104. For example, the second layer 106 may be a primer, intermediate coat, or topcoat.

[0079] The first layer 104 and the second layer 106 may be automotive original equipment manufacturer coatings, automotive repair coatings, industrial coatings, architectural coatings, coil coatings, packaging coatings, marine coatings, aerospace coatings, consumer electronics coatings, or combinations thereof.

[0080] The second layer 106 may comprise a film-forming resin and optionally a pigment. As used herein, "pigment" refers to insoluble particles that provide reflective properties in the visible wavelengths of the electromagnetic spectrum. As used herein, the term "visible light" refers to the visible wavelengths of the electromagnetic spectrum. For example, the visible wavelength range may be from 400 nm to 700 nm. Pigments can provide visible light reflective properties to compositions incorporating pigments.

[0081] As used herein, “insoluble” in relation to pigments means that the pigment (including components containing the pigment) is insoluble in water and typical solvents, such as organic solvents used in coating compositions, film compositions, and article compositions. Solubility can be tested, for example, by preparing a mixture of the solute (e.g., pigment particles) at ambient temperature in a desired medium (based on the total weight of the mixture, such as water and / or organic solvents). If the pigment dissolves in the desired medium, the pigment is soluble. If the pigment remains as a separate phase, the pigment is insoluble. Therefore, when formulating coatings, films, or articles incorporating pigments, solvents in which the pigment is insoluble can be selected.

[0082] Substrate 102 may include a radar-transmitting substrate. "Radar-transmitting substrate" refers to a substrate having a composition and thickness suitable for transmitting electromagnetic radiation at various radar frequencies (e.g., in the automotive frequency range of 76 GHz to 81 GHz), having a minimum transmission loss (if any). With respect to transmission loss, "minimum" means no more than 5 dB, such as, for example, no more than 4 dB, no more than 3 dB, no more than 2 dB, no more than 1 dB, no more than 0.5 dB, no more than 0.2 dB, or no more than 0.1 dB. For example, the radar-transmitting substrate may be transparent to various radar frequencies. That is, the radar-transmitting substrate may have a one-way radar transmission loss (OWRTL) of no more than 5 dB (described below), which is measured by using a radar transmission system as described below in the 76 GHz to 81 GHz radar range. Radar-transmitting substrates can be non-metallic and include polymeric substrates (e.g., polymers), such as plastics, including polyesters, polyolefins, polyamides, cellulose, polystyrene, polyethylene terephthalate, polyacrylic acid, polyethylene naphthalate, polypropylene, polyethylene, polyepoxides, nylon, ethylene-vinyl alcohol copolymers, polylactic acid, other “green” polymeric substrates, polycarbonate, polycarbonate-acrylonitrile-butadiene-styrene, polyurethane, thermoplastic olefins, or combinations thereof. Radar-transmitting substrates can be filled or unfilled plastics. Filled plastics include plastics with additives (such as fibers, such as glass fibers) and / or particles (such as talc). For example, radar-transmitting substrates may contain carbon fibers. Filled plastics may also be referred to as composite materials. Radar-transmitting substrates may include glass, wood, or combinations thereof.

[0083] Substrate 102 may be an automotive substrate, industrial substrate, building substrate, roll-to-roll substrate, packaging substrate, marine substrate, aerospace substrate, consumer electronics device substrate (e.g., telephone, computer, or tablet computer), or a combination thereof. Substrate 102 may be a bumper trim, rearview mirror housing, fender, hood, trunk, door, radome, antenna cover, etc., or a combination thereof, or aerospace components, such as, for example, nose cones, radomes, etc., or combinations thereof. As used herein, “automobile” in its broadest sense refers to all types of vehicles, such as, but not limited to, cars, trucks, buses, tractors, harvesters, heavy equipment, vans, golf carts, motorcycles, bicycles, railcars, aircraft, helicopters, boats of all sizes, etc.

[0084] The dry film thickness t1 of the first layer 104 and the dry film thickness t2 of the second layer 106 may each be at least 0.2 μm, such as at least 0.25 μm, at least 1 μm, at least 5 μm, at least 10 μm, at least 20 μm, at least 30 μm, at least 50 μm, or at least 100 μm. The dry film thickness t1 of the first layer 104 and the dry film thickness t2 of the second layer 106 may each be no greater than 1000 μm, such as at least 900 μm, at least 800 μm, at least 750 μm, at least 500 μm, at least 200 μm, at least 100 μm, or at least 80 μm. The dry film thickness t1 of the first layer 104 and the dry film thickness t2 of the second layer 106 can be in the range of 0.2 μm to 1000 μm, such as, for example, 10 μm to 500 μm, 1 μm to 100 μm, 0.25 μm to 130 μm, 2 μm to 50 μm or 10 μm to 25 μm.

[0085] The thickness t of substrate 102 s It can be at least 0.2 mm, such as, for example, at least 0.5 mm, at least 2 mm, or at least 2.5 mm. The thickness t of the substrate 102... s It can be no greater than 6mm, such as, for example, no greater than 5mm, no greater than 4mm, or no greater than 3.5mm. The thickness t of the substrate 102... s It can be in the range of 0.2mm to 6mm, such as, for example, 0.5mm to 6mm, 2mm to 5mm, 2.5mm to 4mm or 2.5mm to 3.5mm.

[0086] As described below, OWRTL quantifies the radar transmission loss (if any) of the radar transmitted through radar transmission system 100. OWRTL can be measured in dB using the PERISENS GMBH Radome Measurement System - Benchtop (RMS-D) (October 2021 specifications). PERISENS' RMS-D has a frequency range of 76 GHz to 81 GHz and a measurement accuracy of + / - 0.1 dB.

[0087] Radar transmission loss (in dB) can be calculated using Formula 2.

[0088] Formula 2:

[0089] OWRTL(db) = Free space transport (dbm) - Sample transport (dbm).

[0090] Formula 3 shows that radar transmission loss is related to the percentage of radar signal transmittance (%T).

[0091] Formula 3:

[0092] %T = 100 × 10 -(OWRTL / 10) .

[0093] Compared to the transmission of electromagnetic radiation through the coating before external stimulation, after external stimulation, the first layer 104 and / or the radar transmission system 100 are capable of transmitting 10% or more of electromagnetic radiation, including frequencies from 1 GHz to 300 GHz (such as 1 GHz to 100 GHz or 76 GHz to 81 GHz), through the coating, such as 20% or more, 30% or more, 40% or more, 50% or more, 75% or more, 100% or more, 200% or more, or 300% or more. The wavelength range of 76 GHz to 81 GHz (e.g., 77 GHz) can be used for automotive radar and other radar applications. For example, the first layer 104 and / or the radar transmission system can transmit 10% or more of electromagnetic radiation at a specific frequency and / or for all frequencies in the 1 GHz to 300 GHz range (as desired, such as, for example, 76 GHz, 76.5 GHz, 77 GHz, and / or 81 GHz).

[0094] This disclosure provides a component including a radar transmission system 100 and a radar system 108. The radar system 108 can be configured for various purposes, including blind spot detection, lane change assist, collision mitigation, collision warning, parking assist, rear cross-traffic alert, adaptive cruise control, pre-collision, reversing parking assist, rear collision avoidance, other functions, or combinations thereof. The radar system 108 can detect the distance between the radar system 108 and another object 110. The radar system 108 can be, for example, a direct-propagation radar system, an indirect-propagation radar system, a phased-array radar, a 4D radar, or a combination thereof.

[0095] Radar system 108 may be configured to transmit electromagnetic radiation 112 through radar transmission system 100 and receive electromagnetic radiation 114 reflected by object 110. Radar system 108 may be located near and / or adjacent to substrate 102. The radar system may transmit electromagnetic radiation 112 that can pass through radar transmission system 100. Radar transmission system 100 may minimize (if any) the transmission of electromagnetic radiation 112 through it, such that electromagnetic radiation 112 can exit radar transmission system 100. Electromagnetic radiation 112 exiting radar transmission system 100 may be used to detect object 110. For example, electromagnetic radiation 112 may be reflected from object 110 and returned to radar system 108 as electromagnetic radiation 114 through radar transmission system 100.

[0096] In addition to the first layer 104 and the second layer 106, the radar transmission system 100 may optionally further include a pretreatment layer, an adhesion promoter layer, a primer layer, a mid-coat layer, a topcoat layer, a primer layer, or a combination thereof, applied to at least a portion of the first surface 102a of the substrate 102. For example, a single layer or multiple layers may be stacked on at least a portion of the first surface 102a, such as a multilayer layer stack comprising at least three layers (the first layer 104, the second layer 106, and a third layer below or above at least a portion of the first layer 104 or the second layer 106). Additional layers (such as, for example, a pretreatment layer, an adhesion promoter layer, a primer layer, a mid-coat layer, a topcoat layer (e.g., a varnish, a coloring varnish), a primer layer, or a combination thereof) may be deposited before or after the first layer 104 and the second layer 106. The coloring varnish may be, for example, a varnish in which dyes and / or pigments (including nanoscale pigment dispersions) are added, all of which are incorporated herein by reference in their entirety. Coloring varnishes may contain nanoscale pigment dispersions with an average native particle size of less than 150 nm (as measured by transmission electron microscopy (TEM), such as, for example, less than 100 nm (as measured by TEM). The nanoscale pigment dispersions may have an average native particle size in the range of 20 nm to 150 nm, such as, for example, 20 nm to 100 nm, 20 nm to 80 nm, 20 nm to 60 nm, or 20 nm to 40 nm. For example, nanoscale pigment dispersions may have particle sizes of 25 nm, 35 nm, or 50 nm. As used herein, “average particle size measured by transmission electron microscopy (TEM)” refers to the average Ferrette diameter of the particles as measured by TEM.

[0097] A coating stack for automotive applications may include an adhesion promoter layer applied to at least a portion of a substrate 102, a primer layer disposed on the adhesion promoter layer, a base coat layer disposed on the primer layer, and a clear coat layer disposed on the base coat layer. The first layer 104 may be an adhesion promoter layer, a primer layer, a base coat layer, or a clear coat layer. The second layer 106 may be a primer layer, a base coat layer, or a clear coat layer, and is different from the first layer 104.

[0098] A coating stack applied to at least a portion of substrate 102 (such as, for example, in automotive refinish or aerospace applications) may include an optional pretreatment layer and / or adhesion promoter layer, a primer layer, an undercoat layer, and a clear coat layer. A coating stack applied to at least a portion of substrate 102 (such as, for example, in automotive refinish, general industrial, or aerospace applications) may include an optional pretreatment layer or adhesion promoter layer, a primer layer, and a direct gloss topcoat layer. A direct gloss topcoat layer is a layer that includes both color and gloss in a single coating, and this layer is typically the last coating applied in the coating stack. An additional clear coat may optionally be applied to at least a portion of the direct gloss topcoat layer.

[0099] The membrane may be a multilayer membrane comprising at least two layers, including a first membrane layer (including a thermosetting or thermoplastic layer) and an optional adhesive layer. The adhesive layer may be used for protection as a removable layer or release liner that can be removed before the membrane is applied to a substrate. The first membrane layer may be applied to at least a portion of a carrier membrane that supports the first membrane layer until the first membrane layer is formed, and the carrier membrane may then optionally be removed. The first membrane layer may be applied to at least a portion of a protective transparent film that may itself be on the carrier membrane. The protective transparent film may be thermosetting or thermoplastic, and this protective transparent film will be the top layer when the multilayer membrane is applied to at least a portion of the substrate 102 through contact with the adhesive layer. The layers of the multilayer membrane may comprise thermosetting or thermoplastic polyurethane. The first membrane layer may be sprayed, extruded, molded, or polymerized in situ, or otherwise deposited onto adjacent layers or removable layers of the multilayer membrane.

[0100] In-mold coating (IMC) is an alternative to painting for injection-molded plastic parts. IMC can be accomplished by applying a coating composition to the surface of the article while it is still in the mold by spraying, injection, or other methods known in the art. The coating is then allowed to solidify and adhere to the article. The coating composition or film can be applied in the mold prior to injection molding of the article, such that the coating or film is applied to at least a portion of the surface of the molded article. Both methods are IMC according to this disclosure.

[0101] This disclosure also provides a method for improving radio detection and ranging with a radar system mounted behind a coated article in the electromagnetic radiation frequency range of 1 GHz to 300 GHz (such as 1 GHz to 100 GHz or 76 GHz to 81 GHz). The method includes applying a coating and / or film formed from a coating composition according to this disclosure to a substrate and subjecting the coating and / or film to external stimuli. The improvement may be relative to the coated article before the external stimuli.

[0102] As used herein, unless otherwise expressly stated, all figures, such as those representing values, ranges, quantities, or percentages, may be interpreted as beginning with the word “about,” even if the term is not explicitly stated. Any numerical range described herein is intended to include all subranges contained therein. Plurals encompass singulars, and vice versa. For example, while this disclosure uses terms such as “a” layer, “a” substrate, “a” radar-transmitting substrate, “a” pigment, etc., more than one of these and other components, including mixtures, may be used. When ranges are given, any endpoints of those ranges and / or figures within those ranges may be combined within the scope of this disclosure. The terms “comprising,” “such as,” “e.g.,” and similar terms mean “comprising / such as / e.g., but not limited to.”

[0103] Furthermore, as used herein, the term "polymer" refers to both prepolymers, oligomers, and homopolymers and copolymers; and the prefix "poly" refers to two or more. Unless otherwise expressly stated, the terms "acrylic acid" and "acrylate" are used interchangeably (unless doing so would alter their original meaning) and include acrylic acid, acid anhydrides and their derivatives, lower alkyl-substituted acrylic acid (e.g., C1-C2 substituted acrylic acid, such as methacrylic acid, ethylacrylic acid, etc.), and their C1-C6 alkyl and hydroxyalkyl esters.

[0104] As used in this specification, the term "formation" means the production of an article from a composition by a suitable process, such as curing. For example, a coating formed from a curable coating composition means a single or multiple layer of coating or coated article produced by curing the coating composition under suitable process conditions.

[0105] Example

[0106] This disclosure will be more fully understood by referring to the following examples, which provide illustrative and non-limiting aspects of this disclosure. It should be understood that this disclosure described in this specification is not necessarily limited to the examples described in this section.

[0107] As used herein, unless otherwise indicated, the term “part” refers to a part by weight.

[0108] Measure resistance using the probes of a FLUKE 1587FC insulated multimeter, which is used in ohmmeter mode. Positive temperature Examples of resins with high strength coefficient (PTC)

[0109] PTC Resin 1 (PTC1)

[0110] A positive temperature coefficient (PTC) resin was prepared under a nitrogen atmosphere by adding 345.45 g of octadecanoic acid, 152.18 g of 1,2-propanediol, and 2.54 g of butylstannic acid to a suitable reaction vessel equipped with a stirrer, temperature probe, and Dean-Stark water separator with a condenser. The reactor contents were gradually heated to 130 °C and held until the exothermic reaction subsided, or held for about 1 hour if no exothermic reaction was observed. The temperature was then raised to 180 °C, and after about 20 minutes, gentle bubbling with nitrogen was initiated, and the water distillate was collected. After about 2 hours, the temperature was raised to 200 °C and held until no more water distillate was observed and the acid value was below 1 mg KOH / g. The temperature was lowered to 175 °C, and 48.03 g of trimellitic anhydride was added and held at this temperature until the acid value was about 28 mg KOH / g. The temperature was then set to 60°C, and a mixture of 863.22 g of AROMATIC 200 (available from EXXONMOBILCORP) and 575.48 g of diacetone alcohol was added, followed by further cooling and dilution of the resin.

[0111] As described in ASTM D2369, the measured percentage of solids in the final resin solution (110°C / 1 hour) was 23.9% by weight, and the theoretical hydroxyl value was 26.9 mg KOH / g. Using gel permeation chromatography with tetrahydrofuran solvent and polystyrene standards, the weight-average molecular weight (Mw) was determined to be 10,060 g / mol, and the number-average molecular weight (Mn) was 2,886 g / mol. Unless otherwise stated, Mw and / or Mn reported herein were measured by gel permeation chromatography using polystyrene standards according to ASTM D6579-11 (using a Waters 2695 separation module with a Waters 2414 differential refractometer (RI detector); tetrahydrofuran (THF) was used as the eluent at a flow rate of 1 ml / min, and separation was performed using two PLgelMixed C (300 x 7.5 mm) columns at room temperature; the weight-average molecular weight and number-average molecular weight of the polymer samples were measured by gel permeation chromatography relative to linear polystyrene standards of 800 to 900,000 Da.

[0112] PTC resin 2 (PTC 2)

[0113] Positive temperature coefficient (PTC) resins for some of the following examples were prepared by adding 150.95 g of octadecanoic acid, 48.70 g of 1,2-propanediol, and 0.81 g of butylstannic acid to a suitable reaction vessel equipped with a stirrer, temperature probe, and Dean-Stark water separator with a condenser under a nitrogen atmosphere. The reactor contents were gradually heated to 130°C and held until the exothermic reaction subsided, or held for 1 hour if no exothermic reaction was observed. The temperature was then raised to 180°C, and after 20 minutes, gentle bubbling with nitrogen was initiated, and the water distillate was collected. After 2 hours, the temperature was raised to 200°C and held until no more water distillate was observed and the acid value was below 2 mg KOH / g. The temperature was lowered to 175°C, and 15.37 g of trimellitic anhydride was added and held at this temperature until the acid value was 35 mg KOH / g. The temperature was then set to 60°C, and 276.23 g of aromatic 200 (available from EXXONMOBIL CORP) was added. 184.15 g of diacetone alcohol was also added, and the resin was further cooled and diluted.

[0114] As described in ASTM D2369, the measured percentage of solids in the final resin solution (110°C / 1 hour) was 20.9% by weight, and the theoretical hydroxyl value was 21.7 mg KOH / g. Using gel permeation chromatography with tetrahydrofuran solvent and polystyrene standards, the weight-average molecular weight (mw) was determined to be 19,048 g / mol, and the number-average molecular weight (mn) was 4,061 g / mol. Unless otherwise stated, Mw and / or mn reported herein are measured by gel permeation chromatography using polystyrene standards according to ASTM D6579-11. This was performed using a WATERS 2695 separation module equipped with a WATERS 2414 differential refractometer (RI detector); tetrahydrofuran (THF) was used as the eluent at a flow rate of 1 ml / min, and separation was performed using two plgel mixedc (300 x 7.5 mm) columns at room temperature. The weight-average molecular weight and number-average molecular weight of polymer samples can be measured by gel permeation chromatography relative to linear polystyrene standards ranging from 800 to 900,000 g / mol.

[0115] Test program

[0116] Example 1 is a comparative example containing a non-PTC resin and a carbon conductive additive, which exhibits resistive loss in response to external heating stimuli. Examples 2 through 7 aim to illustrate coating compositions containing PTC resin and a carbon conductive additive that, compared to a comparative coating composition containing PTC resin, achieve an irreversible increase in resistance in response to external heating stimuli. Each coating composition was prepared by mixing Monarch 120 carbon black (conductive additive) with PTC resin (film-forming resin), a crosslinking agent, and optionally a dimethylethanolamine (DMEA) crosslinking inhibitor in a THINKY mixer (THINKY USA, Inc., Laguna Hills, CA) at 2000 rpm for 1 minute. The coating compositions were applied to polyethylene terephthalate (PET) substrates to a thickness of 5 mils using a slit die. The coating compositions were allowed to dry at ambient temperature for 24 hours to form a tactilely dry coating (“sample piece”) on each substrate.

[0117] After curing, the corner-to-corner resistivity (initial resistivity) of a 4-inch x 4-inch cut in each sample specimen was measured. The cut was then placed in an oven and heated at 60°C for 30 minutes, and the corner-to-corner resistivity was measured again immediately after removal. The corner-to-corner resistivity was then measured daily while the samples cooled at ambient temperature until the daily percentage change was less than 5%.

[0118] Example 1 (Comparison)

[0119] Example 1 is a coating composition comprising 13 parts Monarch 120 carbon black, 11 parts Cymel 303 melamine crosslinking agent (available from ALLNEXUSA INC.), and 76 parts 40 / 60 vinyl acetate / vinyl chloride copolymer (VINNOL H 40 / 60 available from WACKER CHEMIE AG), used to prepare the sample specimens as described above. It is noteworthy that VINNOL 40 / 60 is not a PTC resin and therefore exhibits increased conductivity upon heating. For example, Example 1 was measured to have an initial resistivity of 7.09 kΩ, and after heating in an oven, the resistivity of Example 1 immediately decreased to 3.53 kΩ, a reduction of 50%. After being left at ambient temperature for one week, the daily percentage change was less than 1%, and the resistivity of Example 1 was measured to be 3.36 kΩ, a reduction of 53% compared to the initial resistivity. Therefore, Example 1 demonstrates that the resin in a conductive ink coating composition that does not possess PTC properties does not become more resistive upon heating.

[0120] Example 2

[0121] Example 2 is a coating composition comprising 13 parts Monarch 120 carbon black, 11 parts Cymel 303 melamine crosslinking agent, and 76 parts PTC 1 resin, used to prepare the sample specimen as described above. Example 2 was measured to have an initial resistivity of 0.041 MΩ, and after heating in an oven, the resistivity of Example 2 immediately increased to 0.469 MΩ, an increase of 1044%. After being placed at ambient temperature for one week, the daily percentage change was less than 5%, and the resistivity of Example 2 was measured to be 0.113 MΩ, an increase of 175% compared to the initial resistivity. Therefore, Example 2 is considered to have an irreversible increase in resistivity compared to the initial resistivity.

[0122] Example 3

[0123] Example 3 is a coating composition comprising 13 parts Monarch 120 carbon black, 11 parts Cymel 303 melamine crosslinking agent, and 76 parts PTC 2 resin, used to prepare the sample specimen as described above. Example 3 was measured to have an initial resistivity of 0.0266 MΩ, and after heating in an oven, the resistivity of Example 3 immediately increased to 5.15 MΩ, an increase of 19242%. After being placed at ambient temperature for one week, the daily percentage change was less than 5%, and the resistivity of Example 3 was measured to be 1.00 MΩ, an increase of 3666% compared to the initial resistivity. Therefore, Example 3 is considered to have an irreversible increase in resistivity compared to the initial resistivity.

[0124] Example 4

[0125] Example 4 is a coating composition comprising 13 parts Monarch 120 carbon black, 22 parts Cymel 303 melamine crosslinking agent, and 65 parts PTC 2 resin, used to prepare the sample specimen as described above. Example 4 was measured to have an initial resistivity of 14.9 MΩ, and after heating in an oven, the resistivity of Example 4 immediately increased to 41.41 MΩ, an increase of 178%. After being placed at ambient temperature for three days, the daily percentage change was less than 5%, and the resistivity of Example 4 was measured to be 32.87 MΩ, an increase of 120% compared to the initial resistivity. Therefore, Example 4 is considered to have an irreversible increase in resistivity compared to the initial resistivity.

[0126] Example 5

[0127] Example 5 is a coating composition comprising 13 parts Monarch 120 carbon black, 3.67 parts n,n'-carbonyldiimidazole (CDI) crosslinking agent, and 83.33 parts PTC 2 resin, used to prepare the sample specimen as described above. Example 5 was measured to have an initial resistivity of 0.048 MΩ, and after heating in an oven, the resistivity of Example 5 immediately increased to 0.179 MΩ, an increase of 273%. After being placed at ambient temperature for six days, the daily percentage change was less than 5%, and the resistivity of Example 5 was measured to be 0.09 MΩ, an increase of 87.5% compared to the initial resistivity. Therefore, Example 5 is considered to have an irreversible increase in resistivity compared to the initial resistivity.

[0128] Example 6

[0129] Example 6 is a coating composition comprising 13 parts Monarch 120 carbon black, 17 parts Resimene HM-2608 melamine crosslinking agent (available from PREFERE RESINS HOLDING GMBH), and 70 parts PTC 2 resin, used to prepare the sample specimen as described above. Example 6 was measured to have an initial resistivity of 0.482 MΩ, and after heating in an oven, the resistivity of Example 6 immediately increased to 0.933 MΩ, an increase of 93.5%. After one week of heating, no permanent increase in resistance was observed in Example 6. It was observed that the coating composition was substantially crosslinked at the time of initial resistivity measurement because the HM-2608 melamine crosslinking agent was not prevented from crosslinking prior to the application of heat.

[0130] Example 7

[0131] Example 7 is a coating composition comprising 13 parts Monarch 120 carbon black, 17 parts Resimene HM-2608 melamine crosslinking agent, 0.01 parts DMEA (100% effective neutralizing crosslinking agent), and 70 parts PTC 2 resin, used to prepare the sample specimen as described above. Example 7 was measured to have an initial resistivity of 0.034 MΩ and an OWRTL of 2.9 dB as measured using PERISENS RMS-D as described above. After heating in an oven, the resistivity of Example 7 increased to 48.44 MΩ, an increase of 142203%. After being placed at ambient temperature for ten days, the daily percentage change was less than 5%, and the resistivity of Example 7 was measured to be 1.63 MΩ, an increase of 4676% compared to the initial resistivity, with an OWRTL of 2.2 dB, a decrease of 0.7 dB. Therefore, Example 7 is considered to have an irreversible increase in resistivity compared to the initial resistivity.

[0132] Although the above description is based on specific examples only, other coating compositions according to this disclosure can achieve an irreversible increase in conductivity and can be used with other external stimuli.

[0133] Although the numerical ranges and parameters described in this disclosure are approximate, the values ​​illustrated in specific examples are reported as precisely as possible. However, any numerical value inherently contains a certain degree of error, which is inevitably caused by standard variations in its respective test measurements.

[0134] Although specific examples have been described above for illustrative purposes, it will be apparent to those skilled in the art that many detailed changes may be made to this disclosure without departing from the scope of the disclosure as defined in the appended claims.

[0135] As used in this article, the term "average" refers to the mean of any variable x (such as wavelength, diameter, lateral dimension, thickness, etc.), and it is calculated using the following formula: Average = (1 / n)σx i The N values ​​of variable x are averaged such that i = 1 to N, and σx i = x1 + x2 + ... + x n .

[0136] Various features and characteristics are described in this specification to provide an understanding of the composition, structure, production, function, and / or operation of this disclosure, which includes the disclosed compositions, coatings, and methods. It should be understood that the various features and characteristics of this disclosure described in this specification can be combined in any suitable manner, regardless of whether such features and characteristics are expressly combined and described in this specification. The inventors and the applicant expressly represent that such combinations of features and characteristics should be included within the scope of this disclosure as set forth in this specification. Thus, the claims may be amended to state any feature and characteristic expressly or inherently described in this specification or otherwise expressly or inherently supported by this specification in any combination. Furthermore, the applicant reserves the right to amend the claims to expressly waive features and characteristics that may be present in the prior art, even if such features and characteristics are not expressly described in this specification. Therefore, any such amendment will not add anything new to the specification or claims and will comply with the requirements of written description, sufficiency of description, and additional matters.

[0137] Unless otherwise specified, any patent, publication or other document identified in this specification is generally incorporated herein by reference in its entirety, but only to the extent that the incorporated material does not conflict with any existing descriptions, definitions, statements, descriptions or other disclosures expressly set forth in this specification. Thus, and to the extent necessary, any conflicting material incorporated by reference as expressly set forth in this specification supersedes any conflicting material incorporated by reference. Any material or portion thereof incorporated by reference in this specification that conflicts with any existing definitions, statements or other disclosures set forth herein is incorporated only to the extent that the incorporated material does not conflict with any existing disclosure. The applicant reserves the right to amend this specification to expressly describe any subject matter or portion thereof incorporated by reference. Amendments to this specification to add such incorporated subject matter will comply with the requirements of written description, sufficiency of description and additional matters.

[0138] In addition to the foregoing, this disclosure may be described in various configurations and alternative configurations to provide specific physical properties, characteristics, compositions, and / or results. For example, at least one configuration of this disclosure includes a coating composition that may comprise a film-forming resin and a conductive additive; wherein the coating formed by the coating composition has an irreversible increase in resistivity of at least 20%, as measured with an ohmmeter probe before and after exposing the coating to an external stimulus.

[0139] In the additional or alternative configuration, the irreversible increase in the measured resistivity is at least 50%. In the additional or alternative configuration, the conductive additive includes carbon, a conductive metal, a conductive polymer, or a combination thereof. In the additional or alternative configuration, the conductive additive includes carbon black, carbon fiber, graphene, or a combination thereof. In the additional or alternative configuration, the conductive additive includes carbon nanotubes configured to degrade in response to an external stimulus, and the conductive additive includes a conductive polymer, or a combination thereof, configured to degrade in response to an external stimulus. In the additional or alternative configuration, the external stimulus includes any one of heat, photochemical radiation, or a combination thereof. In the additional or alternative configuration, the external stimulus includes any one of the application of an electric current, a chemical reagent, or a combination thereof. In the additional or alternative configuration, the external stimulus includes heating to a temperature of at least 30 degrees Celsius. In the additional or alternative configuration, the film-forming resin includes a positive temperature coefficient resin that changes its physical properties in response to an external stimulus.

[0140] In additional or alternative configurations, the film-forming resin comprises at least 10 carbon backbones. In additional or alternative configurations, the film-forming resin comprises hydroxyl functional groups and / or carboxylic acid functional groups. In additional or alternative configurations, the film-forming resin further comprises a crosslinking agent. In additional or alternative configurations, the film-forming resin further comprises a crosslinking inhibitor. In additional or alternative configurations, the crosslinking inhibitor is at least partially deactivated in response to external stimuli. In additional or alternative configurations, the crosslinking agent includes amino plastics, polyisocyanates, polyepoxides, β-hydroxyalkylamides, polybasic acids, acid anhydrides, organometallic acid-functionalized materials, polyamines, polyamides, or combinations thereof. In additional or alternative configurations, the crosslinking inhibitor comprises a solvent, an acid, a base, a metal chelating agent, or a combination thereof.

[0141] In the additional or alternative configuration, the crosslinking inhibitor comprises dimethylethanolamine, propionic acid, acetic acid, amine, ammonia, acetylacetone, thiol, or a combination thereof. In the additional or alternative configuration, the coating substantially maintains its cohesiveness after the application of an external stimulus. In the additional or alternative configuration, the coating substantially maintains its initial (i) aesthetic properties and (ii) its mechanical coating properties with adjacent layers after the application of an external stimulus. In the additional or alternative configuration, compared to the transmission of electromagnetic radiation through the coating before the external stimulus, the coating is able to transmit 10% or more of electromagnetic radiation, including frequencies from 1 GHz to 300 GHz, through the coating after the external stimulus.

[0142] In additional or alternative configurations, after exposure to external stimuli, the coating composition may further comprise: a non-conductive coating or a non-conductive film; wherein the non-conductive coating or film transmits 20% or more of electromagnetic radiation, including frequencies from 1 GHz to 300 GHz, through the coating or film. In additional or alternative configurations, using a multi-angle spectrophotometer with D65 illumination and a 10° viewfinder, the non-conductive coating or film comprises 15 or less CIELABΔE compared to the coating / film before the application of external stimuli. In additional or alternative configurations, the non-conductive coating or film has a dry film thickness in the range of 0.2 micrometers to 1000 micrometers.

[0143] In addition to the foregoing, this disclosure may include an article comprising a substrate; and a non-conductive coating or film formed on the substrate, wherein: the non-conductive coating or film comprises a film-forming resin and conductive additives to which external stimulation has been applied; the non-conductive coating or film transmits 20% or more of electromagnetic radiation with frequencies ranging from 1 GHz to 300 GHz through the coating or film. In an additional or alternative configuration, using a multi-angle spectrophotometer with D65 illumination and a 10° viewfinder, the non-conductive coating or film comprises 15 or less CIELABΔE compared to the coating / film before external stimulation. In an additional or alternative configuration, the non-conductive coating or film has a dry film thickness in the range of 0.2 micrometers to 1000 micrometers. In an additional or alternative configuration, the substrate comprises a bumper trim panel, a rearview mirror housing, a radome, or a combination thereof. In an additional or alternative configuration, the substrate is radar transmissive. In an additional or alternative configuration, the non-conductive coating or film comprises a pretreatment layer, an adhesion promoter layer, a primer layer, a mid-coat layer, a topcoat layer, a primer layer, or a combination thereof.

[0144] Furthermore, another configuration of this disclosure may include a method for manufacturing an article, wherein the method may include: applying a coating composition to a substrate, wherein the coating comprises a film-forming resin and a conductive additive; curing and / or drying the coating composition on the substrate to form a self-supporting coating; and subjecting the self-supporting coating to an external stimulus to form a coating layer on the substrate; wherein the coating layer is non-conductive and transmits 20% or more of electromagnetic radiation, including frequencies from 1 GHz to 300 GHz, through the non-conductive coating.

[0145] In additional or alternative configurations, the method may further include applying the second coating composition to the self-supporting coating using electrodeposition, electrostatic-assisted application, or a combination thereof. In additional or alternative configurations, subjecting the self-supporting coating to an external stimulus includes one or more of the following: heating the self-supporting coating; and applying a chemical reagent to the self-supporting coating. In additional or alternative configurations, the external stimulus further includes any one or more of the following: subjecting the self-supporting coating to particle radiation; applying electromagnetic radiation to the self-supporting coating; and applying an electric current to the self-supporting coating. In additional or alternative configurations, applying the external stimulus results in an improvement of at least 10% in the radar transmission loss of the coating composition in the electromagnetic frequency range of 1 GHz to 300 GHz.

[0146] In further additional or alternative configurations, this disclosure may include a coating composition comprising: a positive temperature coefficient resin; a conductive additive; and a crosslinking agent. In additional or alternative configurations, the positive temperature coefficient resin may comprise a polyester polymer having the following chemical structure: Where n≥1, X is incorporated through any polyol, and R is any component, including H; and / or the positive temperature coefficient resin may comprise a polyester polymer with the following chemical structure: Wherein n≥1, Y is derived from any polybasic acid (including polybasic acid halides), polyester, etc., and R is any component, including H. In additional or alternative configurations, the coating formed by this coating composition has an irreversible increase in resistivity of at least 20%, as measured with an ohmmeter probe before and after exposure of the coating to an external stimulus, such as the angle-to-diagonal resistance of the coating before and after exposure to an external stimulus as described in this specification. In additional or alternative configurations, the crosslinking agent includes amino plastics, polyisocyanates (including blocked isocyanates), polyepoxides, β-hydroxyalkylamides, polybasic acids, acid anhydrides, organometallic acid functionalized materials, polyamines, polyamides, or combinations thereof.

[0147] While this disclosure provides descriptions of various specific aspects for illustrating different aspects of this disclosure and / or its potential applications, it should be understood that variations and modifications will occur to those skilled in the art. Therefore, the scope of this disclosure should be understood to be at least as broad as the claims made thereto, and not as narrow as defined by the specific illustrative aspects provided herein.

Claims

1. A coating composition comprising: Film-forming resins; and A conductive additive, wherein the conductive additive is conductive; The coating formed from the coating composition has an irreversible increase in resistivity of at least 20%, as measured with an ohmmeter probe before and after the coating is exposed to an external stimulus.

2. The coating composition according to claim 1, wherein the measured irreversible increase in resistivity is at least 50%.

3. The coating composition according to claim 1 or 2, wherein the conductive additive comprises carbon, a conductive metal, a conductive polymer, or a combination thereof.

4. The coating composition according to any one of claims 1 to 3, wherein the conductive additive comprises carbon black, carbon fiber, graphene, or a combination thereof.

5. The coating composition according to any one of claims 1 to 4, wherein: The conductive additive includes carbon nanotubes configured to degrade in response to the external stimulus, and The conductive additive includes a conductive polymer or a combination thereof configured to degrade in response to the external stimulus.

6. The coating composition according to any one of claims 1 to 5, wherein the external stimulus includes any one of heat, photochemical radiation, or a combination thereof.

7. The coating composition according to any one of claims 1 to 5, wherein the external stimulus comprises any one of an electric current, the application of a chemical reagent, or a combination thereof.

8. The coating composition according to any one of claims 1 to 7, wherein the film-forming resin comprises a positive temperature coefficient resin that changes its physical properties in response to the external stimulus.

9. The coating composition according to any one of claims 1 to 8, wherein the coating composition further comprises: Crosslinking inhibitors; The crosslinking inhibitor is at least partially inactivated in response to the external stimulus.

10. The coating composition according to any one of claims 1 to 9, wherein after the application of the external stimulus, the coating substantially retains any one or all of the following: (i) Cohesion after the application of the external stimulus; (ii) Initial aesthetic properties, and (iii) Mechanical coating properties of adjacent layers after the application of the external stimulus.

11. The coating composition according to any one of claims 1 to 10, wherein, compared to the transmission of electromagnetic radiation through the coating before the external stimulus, the coating is capable of transmitting 10% or more of electromagnetic radiation with frequencies ranging from 1 GHz to 300 GHz through the coating after the external stimulus.

12. The coating composition of claim 11, wherein after exposure to the external stimulus, the coating composition comprises: Non-conductive coating or non-conductive film; The non-conductive coating or non-conductive film transmits 20% or more of electromagnetic radiation, including frequencies from 1 GHz to 300 GHz, through the coating or film.

13. An article of manufacture, said article comprising: Substrate; and A non-conductive coating or non-conductive film formed on the substrate, wherein: The non-conductive coating or film comprises a film-forming resin to which an external stimulus has been applied and a conductive additive, wherein the conductive additive is conductive. The non-conductive coating or non-conductive film transmits 20% or more of electromagnetic radiation at frequencies from 1 GHz to 300 GHz through the coating or film.

14. The article of claim 13, wherein the substrate comprises a bumper trim panel, a rearview mirror housing, a radar dome, or a combination thereof.

15. A method for manufacturing an article of articles, the method comprising: Curing and / or drying a coating composition on a substrate to form a self-supporting coating, wherein the coating composition comprises a film-forming resin and a conductive additive; as well as The self-supporting coating is subjected to external stimuli to form a coating layer on the substrate; Wherein, due to the external stimulus, the coating layer: It is non-conductive and has a resistivity of at least 1 ohm × cm as measured by a four-point ohmmeter probe. as well as The non-conductive coating allows 20% or more of electromagnetic radiation at frequencies from 1 GHz to 300 GHz to pass through it.

16. The method of claim 15, further comprising: The second coating composition is applied to the self-supporting coating using electrodeposition, electrostatic assisted application, or a combination thereof.

17. The method according to any one of claims 15 to 16, wherein subjecting the self-supporting coating to the external stimulus comprises one or more of the following: Heating the self-supporting coating; and Chemical reagents are applied to the self-supporting coating.

18. The method according to any one of claims 15 to 17, wherein the external stimulus comprises any one or more of the following: The self-supporting coating is subjected to particle radiation; Electromagnetic radiation is applied to the self-supporting coating; and An electric current is applied to the self-supporting coating.

19. The method according to any one of claims 15 to 18, wherein applying the external stimulus causes the coating composition to improve radar transmission loss by at least 10% in the electromagnetic frequency range of 1 GHz to 300 GHz.

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