阅读说明：本技术 具有高介电常数和低介电损耗的聚合物组合物 (Polymer composition with high dielectric constant and low dielectric loss ) 是由 焦云峰 于 2019-10-22 设计创作，主要内容包括：本文公开了具有低介电损耗、同时保持高介电常数的聚合物组合物。所述组合物包含：a)至少一种热塑性聚合物；和b)涂覆有二氧化硅涂覆颗粒的石墨薄片,其中所述经涂覆的石墨薄片具有的C：Si重量比范围为约10∶1-4∶1,并且所述二氧化硅涂覆颗粒具有约80-400nm的平均直径。(Disclosed herein are polymer compositions having low dielectric loss while maintaining a high dielectric constant. The composition comprises: a) at least one thermoplastic polymer; and b) graphite flakes coated with silica-coated particles, wherein the coated graphite flakes have a C: the Si weight ratio ranges from about 10: 1 to 4: 1, and the silica-coated particles have an average diameter of about 80 to 400 nm.)

1. A polymer composition comprising: a) at least one thermoplastic polymer; and b)2 to 30% by weight of graphite flakes coated with silica-coated particles, the total weight of the composition amounting to 100% by weight, wherein the coated graphite flakes have a C: Si weight ratio in the range from 10: 1 to 4: 1 and the silica particles have an average diameter of 80 to 400 nm.

2. The polymer composition of claim 1, wherein the at least one thermoplastic polymer is selected from the group consisting of: polyamide, polyester, polysulfone, polymethylmethacrylate, polyvinylchloride, polyketone, polyether, polyphenylene sulfide, polyphenylene oxide, polyoxymethylene, polycarbonate, polylactic acid, polystyrene, polyolefin, and combinations of two or more thereof, or the at least one thermoplastic polymer is selected from polyamide, or the at least one thermoplastic polymer is polyamide 6, 6.

3. The polymer composition according to claim 1 or 2, wherein the at least one thermoplastic polymer is present at a level of 30-96 wt. -%, or 40-90 wt. -%, or 50-85 wt. -%, based on the total weight of the composition.

4. The polymer composition of any of claims 1-3, wherein the coated graphite flakes are present at a level of 3-30 wt% or 4-25 wt% based on the total weight of the composition.

5. The polymer composition according to any one of claims 1 to 4, wherein the silica-coated particles have an average diameter of 85 to 350nm or an average diameter of 90 to 300 nm.

6. The polymer composition according to any of claims 1-5, wherein the coated graphite flakes have a C: Si weight ratio in the range of 9.5: 1-4: 1 or 9: 1-4.5: 1.

7. An article formed from the polymer composition of any of claims 1-6.

8. The article of claim 7 which is part of an electronic device.

Technical Field

The present invention relates to polymer compositions having high dielectric constants and low dielectric losses.

Background

There is a great need in the electronics industry for polymer composites with high dielectric constants. Such polymer composites may be used in a variety of electronic systems and devices, such as capacitors, actuators, power cable terminations, micro-antenna materials, and the like. One conventional approach to achieving high dielectric constants in polymeric materials is to incorporate conductive fillers, such as carbon-based or metal-based fillers. However, it has been found that although higher levels of conductive fillers in polymeric materials can improve their dielectric constant, this also causes an increase in dielectric loss. Therefore, there is still a need to develop conductive fillers for polymeric materials such that the dielectric constant of the polymeric material is increased while the dielectric loss thereof remains low.

Disclosure of Invention

Provided herein is a polymer composition comprising: a) at least one thermoplastic polymer; and b) about 2 to 30 weight percent of graphite flake coated with silica-coated particles, the total weight of the composition totaling 100 weight percent, wherein the coated graphite flake has a C: Si weight ratio ranging from about 10: 1 to 4: 1, and the silica particles have an average diameter of about 80 to 400 nm.

In one embodiment of the polymer composition, the at least one thermoplastic polymer is selected from the group consisting of: polyamide, polyester, polysulfone, polymethylmethacrylate, polyvinylchloride, polyketone, polyether, polyphenylene sulfide, polyphenylene oxide, polyoxymethylene, polycarbonate, polylactic acid, polystyrene, polyolefin, and combinations of two or more thereof, or the at least one thermoplastic polymer is selected from polyamide, or the at least one thermoplastic polymer is polyamide 6, 6.

In another embodiment of the polymer composition, the at least one thermoplastic polymer is present in the composition at a level of about 30 to 96 weight percent, or about 40 to 90 weight percent, or about 50 to 85 weight percent, based on the total weight of the composition.

In yet another embodiment of the polymer composition, the coated graphite flakes are present in the composition at a level of about 3 to 30 weight percent or about 4 to 25 weight percent based on the total weight of the composition.

In yet another embodiment of the polymer composition, the silica-coated particles have an average diameter of about 85-350nm or an average diameter of about 90-300 nm.

In yet another embodiment of the polymer composition, the coated graphite flakes have a C: Si weight ratio in a range of about 9.5: 1 to 4: 1 or about 9: 1 to 4.5: 1.

Further provided herein are articles formed from the polymer compositions disclosed above.

In one embodiment, the article is part of an electronic device.

Detailed Description

Disclosed herein are polymer compositions having high dielectric constants and low dielectric losses. The polymer composition comprises: a) at least one thermoplastic polymer, and b) about 2 to 30 weight percent of graphite flakes coated with silica particles, wherein the coated graphite flakes have a C: Si weight ratio in the range of about 10: 1 to 4: 1, and the silica-coated particles have an average diameter of about 80 to 400 nm.

The term "thermoplastic polymer" as used herein refers to a polymer that becomes liquid when heated and freezes to a rigid state when sufficiently cooled. Suitable thermoplastic polymers in accordance with the present disclosure include, but are not limited to, polyamides, polyesters, polysulfones, polymethylmethacrylate, polyvinyl chloride, polyketones, polyethers, polyphenylene sulfide, polyphenylene oxide, polyoxymethylene, polycarbonate, polylactic acid and copolymers thereof, polystyrene and copolymers thereof (e.g., ABS, SBS, SAN, etc.), polyolefins (e.g., polyethylene, polypropylene, copolymers of polyethylene and/or polypropylene), and the like.

In one embodiment, the thermoplastic polymer used herein is selected from polyamides. Suitable polyamides include both aliphatic and aromatic polyamides.

Polyamides are the condensation products of (a) one or more dicarboxylic acids and one or more diamines, or (b) one or more aminocarboxylic acids, or (c) the ring-opening polymerization product of one or more cyclic lactams. The aramid used herein may be a homopolymer, copolymer, terpolymer or high polymer containing at least one aromatic monomer component. For example, the aromatic polyamide can be obtained by using an aliphatic dicarboxylic acid and an aromatic diamine or an aromatic dicarboxylic acid and an aliphatic diamine as raw materials and polycondensing them.

Suitable diamines for use herein may be selected from aliphatic diamines, alicyclic diamines, and aromatic diamines. Exemplary diamines useful herein include, but are not limited to, tetramethylenediamine; hexamethylenediamine; 2-methylpentamethylene diamine; nonamethylenediamine; undecamethylene diamine; dodecamethylenediamine; 2, 2, 4-trimethylhexamethylenediamine; 2, 4, 4-trimethylhexamethylenediamine; 5-methyl nonamethylenediamine; 1, 3-bis (aminomethyl) cyclohexane; 1, 4-bis (aminomethyl) cyclohexane; 1-amino-3-aminomethyl-3, 5, 5-trimethylcyclohexane; bis (4-aminocyclohexyl) methane; bis (3-methyl-4-aminocyclohexyl) methane; 2, 2-bis (4-aminocyclohexyl) propane; bis (aminopropyl) piperazine; aminoethylpiperazine; bis (p-aminocyclohexyl) methane; 2-methyl octamethylene diamine; trimethylhexamethylenediamine; 1, 8-diaminooctane; 1, 9-diaminononane; 1, 10-diaminodecane; 1, 12-diaminododecane; m-xylylenediamine; p-xylylenediamine; and the like and derivatives thereof.

Suitable dicarboxylic acids for use herein may be selected from aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids. Exemplary dicarboxylic acids useful herein include, but are not limited to, adipic acid; sebacic acid; azelaic acid; dodecanoic acid; terephthalic acid; isophthalic acid; phthalic acid; glutaric acid; pimelic acid; suberic acid; 1, 4-cyclohexanedicarboxylic acid; naphthalenedicarboxylic acid; and the like and derivatives thereof.

Exemplary aliphatic polyamides for use herein include, but are not limited to, polyamide 6; polyamide 6, 6; polyamide 4, 6; polyamide 6, 10; polyamide 6, 12; polyamide 11; polyamide 12; polyamide 9, 10; polyamide 9, 12; polyamide 9, 13; polyamide 9, 14; polyamide 9, 15; polyamide 6, 16; polyamide 9, 36; polyamide 10, 10; polyamide 10, 12; polyamide 10, 13; polyamide 10, 14; polyamide 12, 10; polyamide 12, 12; polyamide 12, 13; polyamide 12, 14; polyamide 6, 14; polyamide 6, 13; polyamide 6, 15; polyamide 6, 16; and the like.

Exemplary aromatic polyamides for use herein include, but are not limited to, poly (m-xylylene adipamide) (polyamide MXD, 6); poly (dodecamethylene terephthalamide) (polyamide 12, T); poly (undecamethylene terephthalamide) (polyamide 11, T); poly (decamethylene terephthalamide) (polyamide 10, T); poly (nonamethylene terephthalamide) (polyamide 9, T); poly (hexamethylene terephthalamide) (polyamide 6, T); hexamethylene adipamide/hexamethylene terephthalamide copolyamide (polyamide 6, T/6, 6, i.e., polyamide 6, T/6, 6 having at least about 50 mole% of repeat units derived from 6, T); hexamethylene terephthalamide/hexamethylene adipamide copolyamide (polyamide 6, 6/6, T, i.e., polyamide 6, 6/6, T having at least about 50 mole% of repeat units derived from 6, 6); poly (hexamethylene terephthalamide/hexamethylene isophthalamide) (polyamide 6, T/6, I, i.e., polyamide 6, T/6, I having at least about 50 mole% of repeat units derived from 6, T); hexamethylene terephthalamide/2-methylpentamethylene terephthalamide copolyamide (polyamide 6, T/D, T); hexamethylene adipamide/hexamethylene terephthalamide/hexamethylene isophthalamide copolyamide (polyamide 6, 6/6, T/6, I); poly (caprolactam-hexamethylene terephthalamide) (polyamide 6/6, T); poly (hexamethylene isophthalamide/hexamethylene terephthalamide) (polyamide 6, I/6, T, i.e., polyamide 6, I/6, T having at least about 50 mole% of repeat units derived from 6, I); poly (hexamethylene isophthalamide) (polyamide 6, I); poly (m-xylylene isophthalamide/hexamethylene isophthalamide) (polyamide MXD, I/6, I); poly (m-xylylene isophthalamide/m-xylylene terephthalamide/hexamethylene isophthalamide) (polyamides MXD, I/MXD, T/6, I/6, T); poly (m-xylylene isophthalamide/dodecamethylene isophthalamide) (polyamide MXD, I/12, I); poly (m-xylylene isophthalamide) (polyamide MXD, I); poly (dimethyldiaminodicyclohexylmethane isophthalamide/dodecanamide) (polyamide MACM, I/12); poly (dimethyldiaminodicyclohexylmethane isophthalamide/dimethyldiaminodicyclohexylmethane terephthalamide/dodecanamide) (polyamides MACM, I/MACM, T/12); poly (hexamethylene isophthalamide/dimethyldiaminodicyclohexylmethane isophthalamide/dodecanamide) (polyamide 6, I/MACM, I/12); poly (hexamethylene isophthalamide/hexamethylene terephthalamide/dimethyldiaminodicyclohexylmethane isophthalamide/dimethyldiaminodicyclohexylmethane terephthalamide) (polyamide 6, I/6, T/MACM, I/MACM, T); poly (hexamethylene isophthalamide/hexamethylene terephthalamide/dimethyldiaminodicyclohexylmethane isophthalamide/dimethyldiaminodicyclohexylmethane terephthalamide/dodecane amide) (polyamide 6, I/6, T/MACM, I/MACM, T/12); poly (dimethyldiaminodicyclohexylmethane isophthalamide/dimethyldiaminodicyclohexylmethane dodecanamide) (polyamide MACM, I/MACM, 12); and the like.

In another embodiment, the thermoplastic polymer used herein is polyamide 6, 6.

The at least one thermoplastic polymer may be present at a level of about 30 to 96 weight percent, about 40 to 90 weight percent, or about 50 to 85 weight percent, based on the total weight of the polymer composition disclosed herein.

As used herein, graphite flake is graphite particles that are not in the form of fibers. Graphite flake also includes graphite powder and graphite particles. The graphite may be naturally occurring graphite or synthetic graphite. Non-fibrous graphite or graphite flakes have an aspect ratio (aspect ratio) of less than 2. Such flakes are typically round, oval, flat, or irregularly shaped.

In accordance with the present disclosure, graphite flake used herein is fully or partially coated with silica particles, which is referred to as coated graphite flake. The silica-coated particles have an average diameter of about 80-400nm or about 85-350nm or about 90-300 nm. The average diameter may be determined by measuring the diameter of 100 or more randomly selected coated graphite flakes using, for example, a Scanning Electron Microscope (SEM) and averaging them. And, in the coated graphite flake, the weight ratio of C to Si is in the range of about 10: 1 to 4: 1, or about 9.5: 1 to 4: 1, or about 9: 1 to 4.5: 1.

The coated graphite flakes used herein can be prepared by a sol-gel process, such as the process disclosed in PCT patent application publication No. WO201531570 (which is incorporated herein by reference). The sol-gel process includes mixing graphite flakes, a silica precursor, a hydrolysis, and a surfactant (optional and may be a cationic surfactant or an amphoteric surfactant) in a solvent to produce a mixture solution. This mixing results in a chemical reaction of the silica precursors to form a layer of silica particles on the surface of the graphite flake. Also, the coated graphite flakes may be removed from the mixture solution by filtration.

The solvent used in the sol-gel process is an aqueous solution in which graphite flakes, silica precursor, hydrolysis and optionally surfactant are uniformly dispersed and reacted. Preferably, the solvent used herein is a solvent mixture of water and any one or more of the following: isopropyl alcohol (IPA), methanol, ethanol, Methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK), Propylene Glycol Monomethyl Ether (PGME), Propylene Glycol Monomethyl Ether Acetate (PGMEA), Monoethanolamine (MEA), dipropylene glycol diacrylate (DPGDA), and mixtures of two or more thereof. In one embodiment, the solvent is an aqueous solution of water and one or more of the following: isopropyl alcohol (IPA), methanol, ethanol, Methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK), Propylene Glycol Monomethyl Ether (PGME), Propylene Glycol Monomethyl Ether Acetate (PGMEA), Monoethanolamine (MEA), dipropylene glycol diacrylate (DPGDA). In one embodiment, the solvent may be a mixture of water and one or more of the following: isopropanol (IPA), methanol and ethanol. When the solvent is an aqueous solution of water and IPA, methanol or ethanol, the amount of the solvent may be in the range of about 300 to 5000 parts by weight per 100 parts by weight of the graphite flake, and the mass ratio between water and IPA, methanol and/or ethanol is in the range of about 1: 3 to about 1: 10.

The silica precursors used in the sol-gel process are a source of silica that coats the graphite flakes.

The silica precursor may be a silicon alkoxide represented by formula (I):

(R¹)n Si(OR²)4-n, wherein

R¹Represents a hydrocarbon having 1 to 8 identical or different, substituted or unsubstituted carbon atoms, n represents 0, 1, 2 or 3, and R²Represents a hydrocarbon having 1 to 8 carbon atoms. The silicon alkoxide reacts with water and a hydrolysis catalyst to form silicon dioxide, which is the entity coating the carbon particles.

The silicon alkoxide may be a tetraalkoxysilane. Alternatively, the tetraalkoxysilane can be tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetrapentoxysilane, tetraoctyloxysilane, tetranonoxysilane, dimethoxydiethoxysilane, dimethoxydiisopropoxysilane, diethoxydibutoxysilane, diethoxydi (trityloxy) silane, or mixtures of two or more thereof.

When the silicon alkoxide is tetraethoxysilane (TEOS, Si (OC2H5)4)), the hydrolysis reaction is:

Si(OC₂H₅)₄+2H₂O→SiO₂+4C₂H₅OH

the hydrolysis catalyst acts as an acidic hydrolysis catalyst or a basic hydrolysis catalyst to promote the hydrolysis reaction of the silica precursor. The processes described herein may use either an acidic hydrolysis catalyst or a basic hydrolysis catalyst. The acidic hydrolysis catalyst is a proton (H)⁺) Donors which promote the hydrolysis reaction by protonation of the oxygen atom, while the basic hydrolysis catalyst is a proton (H)⁺) An acceptor which facilitates the reaction by transferring a proton from a carbon atom in hydrolysis to effect nucleophilic addition.

As the acidic hydrolysis, hydrochloric acid may be preferable, and as the basic hydrolysis catalyst, ammonium hydroxide may be preferable.

Surfactants are optionally included in the sol-gel process. The surfactant used herein may be a cationic surfactant having a hydrophilic group that dissociates into cations in an aqueous solution, or may be an amphoteric surfactant that dissociates into both anions and cations in an aqueous solution. The surfactant acts as a binder for the graphite flakes and silica in the process.

Exemplary amphoteric surfactants for use herein include, but are not limited to, polyvinylpyrrolidone, lauryl dimethyl glycine betaine, stearyl dimethyl glycine betaine, lauryl dimethyl amine oxide, lauric amidopropyl betaine, lauryl hydroxysultaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, N-lauroyl-N '-carboxymethyl-N' -hydroxyethyl ethylenediamine sodium, N-cocoyl fatty acid-N '-carboxyethyl-N' -hydroxyethyl ethylenediamine sodium, oleyl-N-carboxyethyl-N-hydroxyethyl ethylenediamine sodium, cocoamidopropyl betaine, lauryl amidopropyl betaine, myristamidopropyl betaine, lauryl dimethyl betaine, lauryl amidopropyl betaine, lauryl betaine, and lauryl amidopropyl betaine, Palm kernel amidopropyl betaine, laurylamidopropyl hydroxysultaine, laurylamidopropylamine oxide, hydroxyalkyl (C12-14) hydroxyethylsarcosine, and the like.

Suitable cationic surfactants may be selected from quaternary ammonium salts, alkylamine salts, pyridinium salts, and the like. The quaternary ammonium salt and alkylamine salt are represented by formula (II):

wherein

R represents identical or different alkyl groups, and X represents halogen fluorine (F), chlorine (Cl) and bromine (Br).

Examples of quaternary ammonium salts for use herein include, but are not limited to, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, octyltrimethylammonium chloride, octyltrimethylammonium bromide, decyltrimethylammonium chloride, decyltrimethylammonium bromide, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, stearyltrimethylammonium chloride, stearyltrimethylammonium bromide, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, distearyldimethylammonium chloride, distearyldimethylammonium bromide, benzalkonium chloride, benzethonium chloride, cetylpyridinium chloride, decahydronaphthalene (decalinium chloride), and fluoroalkyltrimethylammonium iodide, and the like.

Examples of alkylamines for use herein include, but are not limited to, trioctylamine hydrochloride (rioctylamine), trioctylamine hydrobromide, tridecylamine hydrochloride, tridecylamine hydrobromide, tridodecyl amine hydrochloride, tridodecyl amine hydrobromide, trihexadecyl amine hydrochloride, trihexadecyl amine hydrobromide, trioctadecyl amine hydrochloride, trioctadecyl amine hydrobromide, and the like.

The pyridinium salt has a pyridine ring and is represented by the general formula (III):

wherein

R represents an alkyl group, and X represents halogen fluorine (F), chlorine (Cl) and bromine (Br).

Examples of pyridinium salts as used herein include, but are not limited to, pyridinium chloride, cetyl pyridinium bromide, myristyl pyridinium chloride, myristyl pyridinium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, ethyl pyridinium chloride, ethyl pyridinium bromide, hexadecyl pyridinium chloride, hexadecyl pyridinium bromide, butyl pyridinium chloride, butyl pyridinium bromide, methyl hexyl pyridinium chloride, methyl hexyl pyridinium bromide, methyl octyl pyridinium chloride, methyl octyl pyridinium bromide, dimethyl butyl pyridinium chloride, and dimethyl butyl pyridinium bromide.

To obtain the coated graphite used herein, graphite, hydrolysis and optionally a surfactant are uniformly dispersed in a solvent by sonication at room temperature followed by addition of a silica precursor to the dispersion in a weight ratio between silica precursor and graphite of about 0.8: 1 to 4: 1. The coating reaction is carried out at room temperature for about 4-20 hours, and the resulting coated graphite can be obtained by filtration and drying.

The coated graphite flakes may be present at a level of about 3 to 30 weight percent, or about 4 to 25 weight percent, based on the total weight of the polymer composition disclosed herein.

The electrically conductive polyester compositions disclosed herein may further comprise other additives such as colorants, antioxidants, ultraviolet stabilizers, ultraviolet absorbers, heat stabilizers, lubricants, viscosity modifiers, nucleating agents, plasticizers, mold release agents, scratch and mar modifiers, impact modifiers, emulsifiers, optical brighteners, antistatic agents, acid adsorbents, odor adsorbents, hydrolysis resistance agents, antibacterial agents, density modifiers, reinforcing fillers, thermally conductive fillers, electrically conductive fillers, coupling agents, end capping agents, and combinations of two or more thereof. Such additional additives may be present at a level of about 0.005 to 30 weight percent, or about 0.01 to 25 weight percent, or about 0.02 to 20 weight percent, based on the total weight of the conductive polyester composition disclosed herein.

As demonstrated herein, by incorporating graphite flakes coated with silica particles, polymer compositions having high dielectric constants and low dielectric losses ("dielectric constant/dielectric loss" ratio greater than 300) can be obtained.

Further disclosed herein are articles formed from the polymer compositions disclosed herein. Such polymer compositions can be used in many fields, including communications equipment, electronics, and power systems. Exemplary articles formed from the polymer composition include, but are not limited to, capacitors, actuators, power cable terminations, and micro-antennas.

Examples of the invention

Material

·PA66Polyamide 6, 6, available from DuPont (E.I. du Pont de Nemours and Company) (USA) (hereinafter "DuPont") under the trade name DuPont101NC010；

·Irganox 1010Antioxidants, pentaerythritol tetrakis (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate), available from BASF (germany);

·Crodamide 212-a lubricant, stearylerucamide, available from Croda (british);

·GFgraphite flakes, available from Ningboxin far graphite, Inc. (China) (D90 ═ 50 μm);

·C-GF-1coated graphite flakes (average diameter of the silica-coated particles: 243. + -.38 nm, and C: Si weight ratio: 15: 1), prepared as follows: adding 2g GF into a solution consisting of 80ml of ethanol, 20ml of deionized water and 3ml of ammonium hydroxide; the dispersion was mixed with ultrasound for 20 minutes at room temperature; 4ml of tetraethoxysilane are added dropwise to the dispersion over 10 minutes; the dispersion was stirred at room temperature for about 2 hours; extracting the coated graphite flakes by filtration and drying at 90 ℃;

·C-GF-2coated graphite flakes (average diameter of the silica-coated particles: 236. + -. 33nm, C: Si weight ratio: 8: 1), prepared as follows: to a solution consisting of 80ml ethanol, 20ml deionized water and 3ml ammonium hydroxide was added 2g GF: the dispersion was mixed with ultrasound for 20 minutes at room temperature; 4ml of tetraethoxysilane are added dropwise to the dispersion over 10 minutes; the dispersion was stirred at room temperature for about 6 hours; extracting the coated graphite flakes by filtration and drying at 90 ℃;

·C-GF-3coated graphite flakes (mean diameter of the silica-coated particles: 249. + -.34 nm, C: Si weight ratio: 5: 1), prepared as follows: adding 2g GF into a solution consisting of 80ml of ethanol, 20ml of deionized water and 3ml of ammonium hydroxide; the dispersion was mixed with ultrasound for 20 minutes at room temperature; 4ml of tetraethoxysilane are added dropwise to the dispersion over 10 minutes; the dispersion was stirred at room temperature for about 10 hours; extracting the coated graphite flakes by filtration and drying at 90 ℃;

·C-GF-4coated graphite flakes (mean diameter of the silica-coated particles: 258. + -.31 nm, C: Si weight ratio: 2.8: 1), prepared as follows: in a mixture of 80ml ethanol, 20ml deionized water and2g GF is added into the solution formed by 3ml of ammonium hydroxide; the dispersion was mixed with ultrasound for 20 minutes at room temperature; 4ml of tetraethoxysilane are added dropwise to the dispersion over 10 minutes; the dispersion was stirred at room temperature for about 24 hours; extracting the coated graphite flakes by filtration and drying at 90 ℃;

·C-GF-5coated graphite flakes (average diameter of the silica-coated particles: 104. + -.15 nm, C: Si weight ratio: 7: 1), prepared as follows: adding 2g GF into a solution consisting of 80ml of ethanol, 20ml of deionized water and 3ml of ammonium hydroxide; the dispersion was mixed with ultrasound for 20 minutes at room temperature; 2ml of tetraethoxysilane were added dropwise to the dispersion over 10 minutes; stirring the dispersion at ambient temperature for about 12 hours; extracting the coated graphite flakes by filtration and drying at 90 ℃;

·C-GF-6coated graphite flakes (average diameter of the silica-coated particles: 15. + -.4 nm, C: Si weight ratio: 10: 1), prepared as follows: 2g GF and 0.3g cetyl trimethylammonium bromide (as cationic surfactant) are added to a solution consisting of 80ml ethanol, 20ml deionized water and 3ml ammonium hydroxide; the dispersion was mixed with ultrasound for 20 minutes at room temperature; 0.5ml of tetraethoxysilane was added to the dispersion; the dispersion was stirred at room temperature for about 6 hours; extracting the coated graphite flakes by filtration and drying at 90 ℃;

·C-GF-7coated graphite flakes (mean diameter of the silica-coated particles: 102. + -.16 nm, C: Si weight ratio: 8: 1), prepared as follows: 2g GF and 0.3g cetyl trimethylammonium bromide (as cationic surfactant) are added to a solution consisting of 80ml ethanol, 20ml deionized water and 3ml ammonium hydroxide; the dispersion was mixed with ultrasound for 20 minutes at room temperature; 2ml of tetraethoxysilane were added dropwise to the dispersion over 10 minutes; the dispersion was stirred at room temperature for about 10 hours; extracting the coated graphite flakes by filtration and drying at 90 ℃;

·C-GF-8coated graphite flakes (average diameter of the silica-coated particles: 16. + -.5 nm, C: Si weight ratio: 8: 1), prepared as follows: in a mixture consisting of 80ml of ethanol, 20ml of deionized water and 3ml of ammonium hydroxide2g GF and 0.3g cetyl trimethylammonium bromide (as cationic surfactant) were added to the solution; the dispersion was mixed with ultrasound for 20 minutes at room temperature; 0.5ml of tetraethoxysilane was added to the dispersion; the dispersion was stirred at room temperature for about 10 hours; extracting the coated graphite flakes by filtration and drying at 90 ℃;

· ₂SiOsilica nanoparticles, available from new materials science and technology limited, hong kong, china (D90 ═ 200 nm).

The average diameter of the silica-coated particles was determined by randomly selecting 100 silica particles and averaging their diameters using a Scanning Electron Microscope (SEM) (Sigma 500, manufactured by ZEISS (ZEISS) (germany)). The C: Si weight ratio was measured by energy dispersive spectrometry (X-MAX80, Oxford Instruments (UK)) at 20 keV. First, 10 different regions were randomly selected on the coated graphite sheet, with no more than two regions selected from one coated sheet. Then, the contents of C and Si in each region were measured, and the average weight ratio of C: Si was calculated.

In each of comparative examples CE1-CE8 and examples E1-E6, a Process 11 Parallel Twin-Screw Extruder (Parallel Screw-Screen Extruder) (manufactured by Sermer fly science, USA) was used to prepare a polymer composition (all components listed in Table 1) at a barrel temperature set to about 280 ℃ and a Screw speed of about 150 rpm. Test samples were prepared by hot pressing the pellets into 60 x 2mm cube blocks using a hot press (model 4386, manufactured by Carver, Inc.) (usa) with the melt temperature set at 290 ℃. A60X 2mm cube was then used to determine the dielectric constant and dielectric loss of the composition using a N5221A PNA Microwave Network Analyzer (Microwave Network Analyzer) (manufactured by Keysight Technologies, USA).

As shown in CE1-CE4, the addition of conductive fillers (such as graphite) improves the dielectric constant of the polymeric material. However, this also increases its dielectric loss and results in a "dielectric constant/dielectric loss" ratio of less than 200. However, by replacing graphite (E1-E6) with certain silica-coated graphite flakes, a polymeric material with a high dielectric constant and low dielectric loss ("dielectric constant/dielectric loss" ratio higher than 300) is obtained. In such silica-coated graphite flakes, the weight ratio of C to Si ranges from about 10: 1 to 4: 1, and the silica-coated particles have an average diameter of about 80 to 400 nm.