Curable silicone-based compositions and applications thereof

Abstract

The present technology provides a curable silicone-based composition comprising a curable silicone polymer, a catalyst, an electrically conductive filler, and carbon nanostructures. The combination of the electrically conductive filler and the carbon nanostructures provide a cured material that exhibit good electrical conductivity and electromagnetic interference shielding.

Description

CURABLE SILICONE-BASED COMPOSITIONS AND APPLICATIONS THEREOFCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of India Provisional Application 202311077486 filed on November 14, 2023, the disclosure of which is incorporated herein by reference in its entirety.FIELD

[0002] The present technology relates to curable silicone-based compositions. In particular, the present technology relates to a curable silicone-based composition comprising a silicone polymer, a catalyst, first metal coated filler having a first particle size, and the second metal coated filler having a second particle size different from that of the first metal coated filler, and a carbon filler. The composition provides a silicone composite on curing having one or more of electrical conductivity, and / or electromagnetic shielding effectiveness.BACKGROUND

[0003] Silicones are known for their inherent properties such as high thermal stability, flexibility, and / or chemical resistance. Siloxanes are used for electronic or electrical applications based on their properties such as those mentioned above. While it might be desirable to use siloxanes in applications where electrical conductivity may be important, developing electrically conductive siloxane materials is challenging.

[0004] Electrical properties can be achieved in silicones by adding fillers into the silicone matrix, and desired conductivity may be achieved by increasing the filler loading in the composition. At higher loadings, however, the filler particles may separate out from the composition over a period. Hence, the dispersion of fillers with higher loading in the siloxane matrix is a major challenge. Higher loadings of fillers in the composition may also adversely affect the curing kinetics and processability of the composition. Other common challenges include, but not limited to. variable contact resistance and volume resistivity.

[0005] To solve these technical problems, an effort was made to develop curable silicone compositions with desired mechanical and chemical properties.BRIEF DESCRIPTION OF THE INVENTION

[0006] Provided is a curable silicone composition that can provide desired adhesion and other mechanical and chemical properties along with good conductivity and / or electromagnetic interference shielding. In some embodiments, the present technology provides a curable composition comprising a siloxane polymer, a catalyst, and one or more fillers.

[0007] In some embodiments, the polymer comprises an alkoxy radical, a hydroxyl radical, an isocyanate radical, a primary amine, or a carboxylic radical.

[0008] In some embodiments, the polymer includes a combination of organic units or siloxane units comprising one or more alkenyl functional groups, and organic units and siloxane units comprises one or more hydride functional groups. These and other embodiments and aspects are further understood with reference to the following detailed description.

[0009] In one aspect, provided is a curable silicone composition, comprising: a siloxane polymer; first metal coated filler having a first particle size, and the second metal coated filler having a second particle size different from that of the first metal coated filler; a carbon based filler; and a catalyst.

[0010] In one embodiment, the first metal coated filler and the second metal coated filler are each independently selected from a filler particle coated with a metal selected from nickel, silver, copper, gold, or an alloy of two or more thereof.

[0011] In one embodiment, the filler particle is selected from a ceramic, glass, quartz, metal, carbon, or organic resin material.

[0012] In one embodiment, the filler particle is a carbon selected from graphite, carbon black, carbon fibers, carbon nanotubes, or a combination of two or more thereof.

[0013] In one embodiment, the first and second metal coated fillers are each selected from nickel-coated graphite.

[0014] In one embodiment, the first metal coated filler has an average particle size of from above 50 pm to about 150 pm. and the second filler has an average particle size of from above 100 pm to about 200 pm.

[0015] In one embodiment, the first metal coated filler is from about 15 wt.% to about 95 wt.%, and the second metal coated filler is present in an amount of from about 5 wt.% to about 85 wt.% based on the total weight of the first and second metal fillers.

[0016] In one embodiment, the first and second metal coated fillers are each selected from nickel-coated graphite have an angular or flaky shape.

[0017] In one embodiment, the first metal coated filler has an apparent density of 1 to 2 g / cm3.

[0018] In one embodiment, the second metal coated filler has an apparent density of 1 to 2 g / cm3.

[0019] In one embodiment, the metal coated filler is present in an amount of from about 35 to about 70 wt.% based on the total weight of the composition.

[0020] In one embodiment, the carbon based filler is selected from graphite, carbon black, carbon fibers, carbon nanotubes, carbon nanostructures, fragments of carbon nanostructures, fractured carbon nanotubes, elongated carbon nanostructure strands dispersed carbon nanostructure or a combination of two or more thereof.

[0021] In one embodiment, the carbon nanostructures include a plurality of singlewalled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) that are crosslinked in a polymeric structure by being branched, interdigitated, entangled and / or sharing common walls

[0022] In one embodiment, the carbon nanostructures have a surface area of 100 m2 / g or greater.

[0023] In one embodiment, the carbon nanostructures have a surface area of 150- 300m2 / g or greater.

[0024] In one embodiment, the carbon nanostructures are present in an amount of from 0.05 wt.% to about 2 wt.% based on the total weight of the composition.

[0025] In one embodiment, the curable composition further comprises an additional filler.

[0026] In one embodiment, the additional filler is selected from alumina, silicon, magnesia, ceria, hafnia, lanthanum oxide, neodymium oxide, samaria, praseodymium oxide, thoria, urania, yttria, zinc oxide, zirconia, silicon aluminum oxynitride, borosilicate glasses, barium titanate, silicon carbide, silica, modified silica, boron carbide, titanium carbide, zirconium carbide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, zirconium nitride, zirconium boride, titanium diboride, aluminum dodecaboride, barytes, barium sulfate, asbestos, barite, diatomite, feldspar, gypsum, hormite, kaolin, mica, nepheline syenite, perlite, phyrophyllite, smectite, talc, vermiculite, zeolite, calcite, calcium carbonate, wollastonite, calcium metasilicate, clay, aluminum silicate, talc, magnesium aluminum silicate, hydrated alumina, hydrated aluminum oxide, silica, modified silica,silicon dioxide, titanium dioxide,glass fibers, glass flake, clays, exfoliated clays, or other high aspect ratio fibers, rods, or flakes, calcium carbonate, zinc oxide, magnesia, titania, calcium carbonate, talc, mica, wollastonite, alumina, aluminum nitride, silicon carbide, silicon nitride, aluminum nitride, zinc oxide, boron nitride nanosheets, zinc oxide nanotubes, and combinations of two or more thereof.

[0027] In one embodiment, the siloxane polymer comprises a hydrolysable silyl and / or alkoxy functional group.

[0028] In one embodiment, the siloxane polymer comprises at least one or more alkenyl functional groups; and at least one or more hydride functional groups

[0029] In one embodiment, the catalyst is a condensation and / or crosslinking catalyst.

[0030] In one embodiment, the catalyst is selected from the group consisting of metal condensation catalysts and non-metal condensation catalysts.

[0031] In one embodiment, the catalyst is a Hydrosilylation catalyst.

[0032] In one embodiment, the hydrosilylation catalyst is selected from transition metal complexes, wherein suitable transition metal for the catalyst may include, Pt, Ru, Rh, Fe, Ni, Co

[0033] In one embodiment, the curable composition of comprises a crosslinker.

[0034] In one embodiment, the curable composition of comprises an adhesion promoter.

[0035] In another aspect, provided is a cured material of the curable composition of any of the previous embodiments.

[0036] In one embodiment, the cured material has an electromagnetic interference (EMI) shielding efficiency between 15 to 50 dB as measured using Vector Network Analyzer method.

[0037] In one embodiment, the cured material has a volume resistivity between 200 to 500 Ohm-cm.

[0038] In one embodiment, the cured material has an electrical conductivity between 10'4to 2 S / cm.

[0039] In one embodiment, the cured material is used in coatings, adhesives, sealants, gaskets, electrodes, ink. thermally conductive materials, electrically conductive materials, sensors, actuators, heating pad, antibacterial packaging materials, conductive plastics, or EMI shielding materials.DETAILED DESCRIPTION

[0040] In the following specification and the claims which follow, reference will be made to a number of terms, which shall be defined to have the following meanings.

[0041] The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

[0042] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.

[0043] As used herein, the term “aromatic” and “aromatic radical” are used interchangeably and refer to an array of atoms having a valence of at least one comprising at least one aromatic group. The array of atoms having a valence of at least one comprising at least one aromatic group may include heteroatoms such as nitrogen, sulfur, selenium, silicon, and oxygen, or may be composed exclusively of carbon and hydrogen. As used herein, the term “aromatic” includes but is not limited to phenyl, pyridyl, furanyl, thienyl, naphthyl, phenylene, and biphenyl radicals. As noted, the aromatic radical contains at least one aromatic group. The aromatic group is invariably a cyclic structure having 4n+2 “delocalized” electrons where “n” is an integer equal to 1 or greater, as illustrated by phenyl groups (n=l), thienyl groups (n=l ), furanyl groups (n=l), naphthyl groups (n=2), azulenyl groups (n=2), anthraceneyl groups (n=3) and the like. The aromatic radical may also include nonaromatic components. For example, a benzyl group is an aromatic radical which comprises a phenyl ring (the aromatic group) and a methylene group (the nonaromatic component). Similarly, a tetrahydronaphthyl radical is an aromatic radical comprising an aromatic group (CeH?) fused to a nonaromatic component — (CH2)4 — . For convenience, the term “aromatic radical” or “aromatic” is defined herein to encompass a wide range of functional groups such as alk l groups, alkenyl groups, alkynyl groups, haloalkyl groups, haloaromatic groups, conjugated dienyl groups, alcohol groups, ether groups, aldehyde groups, ketone groups, carboxylic acid groups, acyl groups (for example carboxylic acid derivatives such as esters and amides), amine groups, nitro groups, and the like. For example, the 4-methylphenyl radical is a C7 aromatic radical comprising a methyl group, the methyl group being afunctional group which is an alkyl group. Similarly, the 2-nitrophenyl group is a C6 aromatic radical comprising a nitro group, the nitro group being a functionalgroup. Aromatic radicals include halogenated aromatic radicals such as 4- trifluoromethylphenyl. hexafluoroisopropylidenebis(4-phen-l-yloxy) (i.e., —OPhC(CF?)2PhO — ), 4-chloromethylphen-l-yl, 3-trifluorovinyl-2-thienyl, 3- trichloromethylphen-l-yl (i.e., 3-CClsPh-), 4-(3-bromoprop-l-yl)phen-l-yl (i.e., 4- BrCH2CH2CH2Ph-), and the like. Further examples of aromatic radicals include 4- allyloxyphen-l-oxy, 4-aminophen-l-yl (i.e.. 4-H2NPh-), 3-aminocarbonylphen-l-yl (i.e., NFhCOPh-). 4-benzoylphen-l-yl. dicyanomethylidenebis(4-phen-l-yloxy) (i.e., — OPhC(CN)2PhO — ), 3-methylphen-l-yl, methylenebis(4-phen-l-yloxy) (i.e., — OPhCFhPhO — ), 2-ethylphen-l-yl, phenylethenyl, 3-formyl-2-thienyl, 2-hexyl-5-furanyl, hexamethylene-l,6-bis(4-phen-l-yloxy) (i.e., — OPh(CH2)ePhO — ), 4-hydroxymethylphen-l- yl (i.e.. 4-HOCH2PI1-), 4-mercaptomethylphen-l-yl (i.e., 4-HSCH2Ph-), 4-methy Ithi ophen- 1- yl (i.e., 4-CH3SPI1-), 3-methoxyphen-l-yL 2-methoxycarbonylphen-l-yloxy (e.g., methyl salicyl), 2-nitromethylphen-l-yl (i.e., 2-NO2CH2PI1), 3-trimethylsilylphen-l-yl, 4-t- butyldimethylsilylphen-l-yl, 4-vinylphen-l-yl, vinylidenebis(phenyl), and the like. The term “a C3-C10 aromatic radical"’ includes aromatic radicals containing at least three but no more than 10 carbon atoms. The aromatic radical 1 -imidazolyl (C3H2N2 — ) represents a C3 aromatic radical. The benzyl radical (C7H7 — ) represents a C7 aromatic radical. In one or more embodiments, the aromatic groups may include C6-C30 aromatic groups, C10-C30 aromatic groups. C15-C30 aromatic groups. C20-C30 aromatic groups. In some specific embodiments, the aromatic groups may include C3-C10 aromatic groups, C5-C10 aromatic groups, or C8- C10 aromatic groups.

[0044] As used herein the term “cycloaliphatic group” and “cycloaliphatic radical” may be used interchangeably and refers to a radical having a valence of at least one, and wherein the radical comprises an array of atoms which is cyclic but not aromatic. As defined herein a “cycloaliphatic radical” does not contain an aromatic group. A “cycloaliphatic radical” may comprise one or more noncyclic components. For example, a cyclohexylmethyl group (C6H11CH2 — ) is a cycloaliphatic radical which comprises a cyclohexyl ring (the array of atoms which is cyclic, but which is not aromatic) and a methylene group (the noncyclic component). The cycloaliphatic radical may include heteroatoms such as nitrogen, sulfur, selenium, silicon, and oxygen, or may be composed exclusively of carbon and hydrogen. For convenience, the term “cycloaliphatic radical” is defined herein to encompass a wide range of functional groups such as alkyl groups, alkenyl groups, alkynyl groups, haloalkyl groups, conjugated dienyl groups, alcohol groups, ether groups, aldehyde groups, ketone groups, carboxylic acid groups, acyl groups (for example carboxylic acid derivatives such as esters and amides), amine groups,nitro groups, and the like. For example, the 4-methylcyclopent-l-yl radical is a C6 cycloaliphatic radical comprising a methyl group, the methyl group being a functional group which is an alkyl group. Similarly, the 2-nitrocyclobut-l-yl radical is a C4 cycloaliphatic radical comprising a nitro group, the nitro group being a functional group. A cycloaliphatic radical may comprise one or more halogen atoms which may be the same or different. Halogen atoms include, for example; fluorine, chlorine, bromine, and iodine. Cycloaliphatic radicals comprising one or more halogen atoms include 2-trifluoromethylcyclohex-l-yl, 4- bromodifluoromethylcyclooct-l-yl, 2-chlorodifluoromethylcyclohex-l-yl, hexafluoroisopropylidene-2,2-bis(cyclohex-4-yl) (i.e., — CeHioC^CFs^CeHio — ), 2- chloromethylcyclohex-l-yl, 3-difluoromethylenecyclohex-l-yl, 4-trichloromethylcyclohex-l- yloxy, 4-bromodichloromethylcyclohex-l-ylthio, 2-bromoethylcyclopent-l-yl, 2- bromopropylcyclohex-l-yloxy (e.g., CHA'HBrCHjCfiHioO — ), and the like. Further examples of cycloaliphatic radicals include 4-allyloxycyclohex-l-yl, 4-aminocyclohex-l-yl (i.e., H2C6H10 — ), 4-aminocarbonylcyclopent-l-yl (i.e., NH2COC5Hs — ), 4-acetyloxycyclohex-l-yl, 2,2-dicyanoisopropylidenebis(cyclohex-4-yloxy) (i.e., — OCsHio CbThCeHioO — ), 3- methylcyclohex-l-yl, methylenebis(cyclohex-4-yloxy) (i.e., — OCeHioCTbCeHioO — ). 1- ethylcyclobut-l-yl, cyclopropylethenyl, 3-formyl-2-terahydrofuranyl, 2-hexyl-5- tetrahydrofuranyl, hexamethylene- l,6-bis(cy cl ohex-4-yloxy) (i.e., — OC6Hio(CH2)6CeHioO — ), 4-hydroxymethylcyclohex-l-yl (i.e., 4-HOCH2C6H10 — ), 4-mercaptomethylcyclohex-l-yl (i.e., 4-HSCH2C6H10 — ), 4-methylthiocyclohex-l-yl (i.e., 4-CH3SC6H10 — ), 4- methoxy cyclohex-1 -yl, 2-methoxycarbonylcyclohex-l -yloxy (2-CH3OCOC6H10O — ), 4- nitromethylcyclohex-l-yl (i.e., NO2CH2C6H10 — ), 3-trimethylsilylcyclohex-l-yl, 2-t- buty Idimethy Isily Icy clopent- 1 -y 1, 4-trimethoxy silylethylcyclohex- 1 -y 1 (e.g. ,(CH30)3SiCH2CH2CeHio — ), 4-vinylcyclohexen-l-yl. vinylidenebis(cyclohexyl), and the like. The term '‘a C3-C10 cycloaliphatic radical” includes cycloaliphatic radicals containing at least three but no more than 10 carbon atoms. The cycloaliphatic radical 2-tetrahydrofuranyl (C4H7O — ) represents a C4 cycloaliphatic radical. The cyclohexylmethyl radical (C6H11CH2 — ) represents a C7 cycloaliphatic radical. In some embodiments, the cycloaliphatic groups may include C3-C20 cyclic groups. C5-C15 cyclic groups. C6-C10 cyclic groups, or C8-C10 cyclic groups.

[0045] As used herein the term “aliphatic group” and “aliphatic radical” are used interchangeably and refers to an organic radical having a valence of at least one consisting of a linear or branched array of atoms which is not cyclic. Aliphatic radicals are defined to comprise at least one carbon atom. The array of atoms comprising the aliphatic radical mayinclude heteroatoms such as nitrogen, sulfur, silicon, selenium, and oxygen or may be composed exclusively of carbon and hydrogen. For convenience, the term ‘“aliphatic radical” is defined herein to encompass, as part of the ‘‘linear or branched array of atoms which is not cyclic” a wide range of functional groups such as alkyl groups, alkenyl groups, alkenyl groups, haloalkyl groups, conjugated dienyl groups, alcohol groups, ether groups, aldehyde groups, ketone groups, carboxylic acid groups, acyl groups (for example carboxylic acid derivatives such as esters and amides), amine groups, nitro groups, and the like. For example, the 4- methylpent-l-yl radical is a C6 aliphatic radical comprising a methyl group, the methyl group being a functional group which is an alkyl group. Similarly, the 4-nitrobut-l-yl group is a C4 aliphatic radical comprising a nitro group, the nitro group being a functional group. An aliphatic radical may be a haloalkyl group which comprises one or more halogen atoms which may be the same or different. Halogen atoms include, for example; fluorine, chlorine, bromine, and iodine. Aliphatic radicals comprising one or more halogen atoms include the alkyl halides trifluoromethyl, bromodifluoromethyl, chlorodifluoromethyl, hexafluoroisopropylidene, chloromethyl, difluorovinylidene, trichloromethyl, bromodichloromethyl, bromoethyl, 2- bromotnmethylene (e.g., — CH2CHBrCH2 — ). and the like. Further examples of aliphatic radicals include allyl, aminocarbonyl (i.e., — CONH2), carbonyl, 2,2-dicyanoisopropylidene (i.e., — CH2C(CN)2CH2 — ), methyl (i.e., — CH3), methylene (i.e., — CH2 — ), ethyl, ethylene, formyl (i.e., — CHO), hexyl, hexamethylene, hydroxymethyl (i.e., — CH2OH), mercaptomethyl (i.e., — CH2SH), methylthio (i.e.. — SCH3), methylthiomethyl (i.e., — CH2SCH3), methoxy, methoxycarbonyl (i.e., CH3OCO — ), nitromethyl (i.e., — CH2NO2), thiocarbonyl, trimethylsilyl (i.e., (CHsjsSi — ), t-butyldimethylsilyl, 3-trimethyoxysilylpropyl (i.e., (CH3O)3SiCH2CH2CH2 — ). vinyl, vinylidene, and the like. By way of further example, a Cl -CIO aliphatic radical contains at least one but no more than 10 carbon atoms. A methyl group (i.e., CH3 — ) is an example of a Cl aliphatic radical. A decyl group (i.e., CHs(CH2)9 — ) is an example of a CIO aliphatic radical. In one or more embodiments, the aliphatic groups or aliphatic radical may include, but is not limited to, a straight chain or a branched chain hydrocarbon having 1-20 carbon atoms, 2-15 carbon atoms, 3-10 carbon atoms, or 4-8 carbon atoms.

[0046] The present technology provides curable silicone-based compositions and the use of such compositions in a variety of applications. The curable silicone composition provides desired adhesion and other mechanical and chemical properties along with good electrical conductivity and electromagnetic interference shielding. Further, the present compositions allow for the use of relatively high loadings of fillers in the silicone matrixwithout affecting the curing and processing conditions of the compositions. The presence of non-silicone organic units can be employed to provide additional benefits to the overall properties of the hybrid silicone composites.

[0047] The curable silicone-based composition provides a system that upon curing provides a siloxane polymer. The silicon-based composition is not particularly limited and can be selected as desired for a particular purpose or intended application.

[0048] Curable silicone composition

[0049] Siloxane polymer

[0050] The siloxane polymer can be, for example, based on an addition cure composition or a condensation cure composition.

[0051] The addition cure composition can be selected as desired for a particular purpose or intended application. The addition cure composition generally comprises an alkenyl functional organopoly siloxane, a hydrogen functional organopolysiloxane, and a catalyst.

[0052] The alkenyl functional organopolysiloxane is an organopolysiloxane having at least two silicon-bonded alkenyl groups in a molecule. It may be any of well-known organopolysiloxanes used as the base polymer in addition cure silicone compositions. The size of the alkenyl functional organopolysiloxane can be selected as desired. In one embodiment, the alkenyl functional organopolysiloxane has a weight average molecular weight (Mw) of about 3,000 to about 300,000, as measured by gel permeation chromatography (GPC) versus polystyrene standards and a viscosity’ at room temperature (25° C.) of about 100 to about 1 ,000,000 mPa-s, about 200 to about 500,000 mPa-s, or about 500 to about 100,000 mPa-s as measured by a rotational viscometer.

[0053] In one embodiment, the alkenyl functional organopolysiloxane has an average compositional formula:

[0054] R^SiOrr-a)^

[0055] wherein R1is the same or different and selected from substituted or unsubstituted monovalent hydrocarbon groups of 1 to 10 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, and the subscript ‘"a” is a positive number and in embodiments is from 1.5 to 2.8. from 1.8 to 2.5. or from 1.95 to 2.05.

[0056] Illustrative, non-limiting examples of silicon-bonded monovalent hydrocarbon groups represented by R1include alkyl groups such as methyl, ethyl, propyl, isopropyl, buty l, isobutyl, tert-butyl, penty l, neopenty l, hexyl, cyclohexyl, octyl, nonyl and decyl; ary l groups such as phenyl, tolyl, xylyl and naphthyl; aralkyl groups such as benzyl, phenylethyl and phenylpropyl; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl,cyclohexenyl and octenyl; and substituted forms of the foregoing groups in which some or all hydrogen atoms are substituted by halogen atoms (e.g.. fluoro, bromo, chloro), cyano groups or the like, such as chloromethyl, chloropropyl, bromoethyl, trifluoropropyl and cyanoethyl.

[0057] In one embodiment, at least two of R1groups are alkenyl groups. In embodiments, the alkenyl group has 2 to 8 carbon atoms, 2 to 6 carbon atoms, or 2 to 4 carbon atoms. In one embodiment, the content of alkenyl groups is from about 0.01 to about 20 mol %, from about 0. 1 to about 10 mol %. or from about 0.5 to about 5 mol % based on the entire silicon-bonded organic groups (i.e., substituted, or unsubstituted monovalent hydrocarbon groups represented by R1). The alkenyl groups may be attached to silicon atoms at the ends and / or at intermediate positions of the molecular chain. In one embodiment, the alkenyl functional organopolysiloxane includes at least an alkenyl group attached to a silicon atom at the end of the molecular chain.

[0058] In one embodiment, the alkenyl functional organopolysiloxane is a linear diorganopolysiloxane whose backbone consists of recurring diorganosiloxane units ((R1)2SiO2 / 2 units) and whose molecular chain is capped at both ends with triorganosiloxy groups ((R^sSiOi^ units). The alkenyl functional organopolysiloxane may also have a branched structure containing RJSiO3 / 2 units and / or SiO4 / 2 units or it may be of a cyclic structure.

[0059] An organopolysiloxane having a resinous structure may be used in combination with the above alkenyl functional organopolysiloxane. The resinous structure may also be referred to as three-dimensional network structure. Examples of resinous organopolysiloxanes include those consisting essentially of SiO2units, R2kR3PSiOo.5 units or R2qR3rSiOi.o units wherein R2is vinyl or allyl, R3is a monovalent hydrocarbon group free of aliphatic unsaturation, k is 0, 1, 2 or 3, p is 0, 1, 2, or 3, k+p=3, q is 0, 1 or 2, r is 0, 1. or 2, and q+r=2. Suitable monovalent hydrocarbon groups represented by R3are those of 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms.

[0060] In one embodiment, the resinous organopolysiloxane has aMw of 500 to 10,000 as measured by GPC versus polystyrene standards.

[0061] Without being bound to any particular theory, the resinous organopolysiloxane may be compounded for the purpose of improving the physical strength and surface tack of the cured composition. If employed, it may be compounded in an amount of 5 to 90% by weight, 10 to 80%, or 20 to 70% by weight based on the weight of the alkenyl functional organopolysiloxane.

[0062] The organohydrogenpolysiloxane has at least two hydrogen atoms each attached to a silicon atom (SiH groups) in a molecule. The organohydrogenpolysiloxane serves as a crosslinking agent capable of reacting with the alkenyl functional organopolysiloxane. The molecular structure of the organohydrogenpolysiloxane is not particularly limited. Any linear, cyclic, branched, or three-dimensional network (or resinous) structures which are prepared in the art may be used as long as they have at least two silicon-bonded hydrogen atoms (SiH groups) in a molecule. In one embodiment, the organohydrogenpolysiloxane has 2 to about 300, 2 to about 200, or 2 to about 100 SiH groups. In the organohydrogenpolysiloxane used, the number of silicon atoms per molecule (or degree of polymerization) is generally 2 to 300, preferably 3 to 200, and more preferably 4 to 100.

[0063] In one embodiment, the organohydrogenpolysiloxane used herein is a linear polyorganohydrogensiloxane in which each end is terminated with a RcRd2SiOi / 2 unit and intermediate units consist of a HRdSiO2 unit and a Rd2SiC>2'2 unit, wherein each Rcis a hydrogen atom or a C1-C6 alkyl group, and each Rdis independently a C1-C6 alkyl group, wherein alkyl group is selected from methyl, ethyl, propyl, butyl, pentyl or hexyl, and preferably methyl.

[0064] The at least two SiH groups per molecule may be located at the ends or any intermediate positions of the molecular chain or both. The organohydrogenpolysiloxane may have a linear, cyclic, branched, or three-dimensional network structure.

[0065] Examples of the organohydrogenpolysiloxane include, but are not limited to, 1 ,1 ,3,3-tetramethyldisiloxane, 1 ,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopoly siloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymers, trimethylsiloxy-endcapped methylhydrogenpolysiloxane, trimethylsiloxy- endcapped dimethylsiloxane-methylhydrogensiloxane copolymers, dimethylhydrogensiloxy- endcapped dimethylpolysiloxane, dimethylhydrogensiloxy-endcapped dimethylsiloxanemethylhydrogensiloxane copolymers, trimethylsiloxy-endcapped methylhydrogensiloxanediphenylsiloxane copolymers, trimethylsiloxy-endcapped methylhydrogensiloxane- diphenylsiloxane-dimethylsiloxane copolymers. trimethylsiloxy-endcapped methylhydrogensiloxane-methylphenylsiloxane-dimethylsiloxane copolymers, dimethylhydrogensiloxy-endcapped methylhydrogensiloxane-dimethylsiloxane- diphenylsiloxane copolymers, dimethylhydrogensiloxy-endcapped methylhydrogensiloxane- dimethylsiloxane-methylphenylsiloxane copolymers, copolymers of (CH3)2HSiOiz units, (CH?)?SiO 1 / 2 units and SiC>4 / 2 units, copolymers of (CH?)2HSiOi / 2 units and SiCh / 2 units, andcopolymers of (CH3)2HSiOi 2 units, SiOr / 2 units and (CeH5)SiO2 / 3 units. As used herein, the term “endcapped” means that the poly siloxane is capped at both ends of its molecular chain with the indicated groups.

[0066] The organohydrogenpolysiloxane may be added in such an amount as to give 0.1 to 5.0 equivalents, preferably 0.5 to 4.0 equivalents, and more preferably 0.8 to 3.0 equivalents of silicon-bonded hydrogen atoms per silicon-bonded alkenyl group in the alkenyl functional organopolysiloxane. With less than 0.1 equivalent of silicon-bonded hydrogen atoms, the crosslinked density may be too low, and the cured silicone may be less heat resistant. More than 5.0 equivalents of silicon-bonded hydrogen atoms may induce dehydrogenation reaction, giving rise to a problem of foaming and adversely affecting heat resistance.

[0067] In one embodiment, the silicone composition is a condensation cure type comprising an organopolysiloxane component capped with a hydroxyl or hydrolyzable group at an end of its molecular chain, a silane having at least three silicon-bonded hydrolyzable groups in a molecule or a partial hydrolytic condensate thereof, and a condensation catalyst.

[0068] The organopolysiloxane component capped with a hydroxyl or hydrolyzable group at an end of its molecular chain may be linear or a structure having a branched chain as long as it has two or more alkoxy groups bonded to silicon atoms in a molecule and a viscosity of 3 mPa s to 500 rnPa s. The linear polyorganosiloxane is preferable because the viscosity is easily set to the above-described range. Note that in the case of using the branched polyorganosiloxane, it is preferably used in combination with the linear polyorganosiloxane in order to maintain the viscosity as the whole of the component.

[0069] The viscosity of the component is 3 Pa s to 500 Pa s. When the viscosity of the component is less than 3 Pa s, a cured product to be obtained becomes poor in rubber elastic, whereas when it exceeds 500 Pa s, the workability’ when fabricating a cured product such as a cured coating film decreases. Further, when the viscosity of the component exceeds 500 Pa s, the compatibility' with a branched polyorganosiloxane is poor, resulting in failure to obtain a uniform composition.

[0070] In one embodiment, both ends alkoxy silyl group-terminated polyorganosiloxane is represented by the following general formula

[0071]

[0072] Wherein d is 0 or 1. And n is an integer so that the viscosity of the polyorganosiloxane becomes 3 Pa s to 500 Pa s and concretely an integer of l<n<250.

[0073] Besides, as the above component, a branched polyorganosiloxane can be used which has tetrafunctional siloxane unit. The tetrafunctional siloxane unit is expressed as a Q unit. The branched polyorganosiloxane may be used together with the linear polyorganosiloxane, to constitute the both ends alkoxysilyl group-terminated polyorganosiloxane.

[0074] Catalyst

[0075] Condensation catalyst

[0076] The condensation catalyst is a component for accelerating a hydrolysis condensation of the above-mentioned condensation cure composition. As the condensation catalyst, for example, a metal catalyst, an organic acid catalyst, an inorganic acid catalyst, or a base catalyst can be used. From the viewpoint of the curing rate of the composition, the condensation catalyst is preferably a metal catalyst.

[0077] With respect to the metal atom contained in the metal catalyst, for example, there can be mentioned titanium, zirconium, and tin. Particularly , an organotin compound or an alkoxy titanium is preferred. As one mode of the metal catalyst, a compound having an alkoxide as a ligand, preferably an alkoxide having 1 to 4 carbon atoms, further preferably having 1 to 3 carbon atoms, can be used. When using such a catalyst, the catalyst is easily dissolved or dispersed in the curable composition to contribute to acceleration of a uniform condensation reaction.

[0078] Examples of preferred metal catalysts include organic titanium chelate compounds such as ethyl acetoacetonate titanate, titanium diisopropoxybis(ethylacetoacetate) and titanium diisopropoxybis(ethylacetoacetate); organic titanates such as tetrabutyl titanate and tetraisopropyl titanate;; organoaluminum compounds such as tris(acetylacetonato)aluminum and tris(ethylacetoacetato)aluminum; organozirconium compounds such as tetra(acetylacetonato)zirconium and zirconium tetrabutyrate; organotin compounds such as dibutyl tin dioctoate, dibutyl tin dilaurate and dibutyl tin di(2- ethylhexanoate).

[0079] Other condensation catalysts may include metal salts of organic carboxylic acids such as tin naphthenate, tin oleate, tin butyrate, cobalt naphthenate, and zinc stearate; amine compounds such as hexylamine and dodecylamine phosphate; quaternary ammonium salts such as benzyltriethylammonium acetate; alkali metal salts of lower fatty7acids such as potassium acetate and lithium nitrate; dialkylhydroxylamines such as dimethylhydroxylamine and diethylhydroxylamine; guanidyl-containing organosilicon compoundscarbonic acid metal salts, such as iron octoate, manganese octoate, zinc octoate, tin naphthate, tin caprylate, and tinoleate; organotin compounds, such as dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin dioleate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis(triethoxysiloxy)tin, dioctyltin dilaurate, and dimethyltin dineodecanoate; organotitaniums, such as tetraethoxytitanium, tetrapropoxytitanium, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetraisobutoxytitaniuin, diisopropoxytitanium bis(ethylacetoacetate), and 1,3 -propanedi oxy titanium bis(ethylacetoacetate); organoaluminums, such as aluminum trisacetylacetonate. aluminum trisethylacetoacetate, diisopropylaluminum ethylacetoacetate, and triethoxyaluminum; and organozirconium compounds, such as zirconium tetraacetylacetonate, tetraisopropoxyzirconium, tetrapropoxyzirconium, tetra-n- butoxy zirconium, tetraisobutoxyzirconium, tributoxyzirconium acetylacetonate, and tributoxy zirconium stearate.

[0080] With respect to the organic acid catalyst, for example, there can be mentioned compounds having a carboxylic acid, sulfonic acid, or phosphoric acid, and specific examples include acetic acid, trifluoroacetic acid, methanesulfonic acid, toluenesulfonic acid, and an alkylphosphoric acid. With respect to the inorganic acid catalyst, for example, there can be mentioned hydrochloric acid and sulfuric acid.

[0081] Examples of the base catalysts include amine compounds, such as ammonia, trietylamme. and diethylamine, dialkylhydroxyamines, such as dimethylhydroxyamine and diethylhydroxyamine, and guanidyl compounds, such as tetramethylguanidine and guanidyl group-containing silane or siloxane.

[0082] In the curable composition of the present invention, the condensation catalyst is preferably contained in an amount of 0.01 to 20.0 parts by mass, more preferably 0.1 to 5.0 parts by mass, relative to 100 parts by mass of siloxane polymer.

[0083] Hydrosilylation catalyst or addition curing catalyst

[0084] When the combination of alkenyl functional organopolysiloxane and a hydrogen functional organopolysiloxane causes a crosslinking reaction due to an addition reaction, a hydrosilylation catalyst is used as the curing catalyst.

[0085] Examples of suitable hydrosilylation catalysts include, but are not limited to, transition metal complexes. Examples of suitable transition metal for the catalyst may include, but are not limited to. Pt, Ru, Rh, Fe, Ni, Co, and the like. The catalyst can be unsupported or immobilized on a support material, for example, carbon, silica, modified silica, alumina, MgCb or zirconia, or on a polymer or prepolymer, for example polyethylene, polypropylene, polystyrene, or poly(aminostyrene).

[0086] As a representative example of such a curing catalyst, there can be mentioned a platinum catalyst. The platinum catalyst is a curing catalyst for reacting the curable functional group of alkenyl functional organopolysiloxane with the hydrogen group of hydrogen functional organopolysiloxane to obtain a cured product. Examples of platinum compounds include chloroplatinic acid, a platinum-olefm complex, a platinum-vinylsiloxane complex, a platinum-phosphorus complex, a platinum-alcohol complex, and platinum black.

[0087] Examples of suitable Platinum catalyst include, but not limited to, Platinum vinyl siloxane dimer complex and Pt vinyl siloxane tetramer complex.

[0088] The amount of the platinum group metal based catalyst added may be determined in accordance with the desired cure rate. Generally, the catalyst may be used in such an amount to give 0.1 to 1,000 ppm, 1 to 200 ppm or 2.5 to 50 ppm of platinum group metal based on the weight of the alkenyl functional organopolysiloxane.

[0089] The amount of the platinum catalyst incorporated is 0.1 to 1,000 ppm, in terms of a platinum element, based on siloxane polymer. When the amount of the platinum catalyst is smaller than 0.1 ppm, the composition is not satisfactorily cured, and, even when the amount of the platinum catalyst is more than 1.000 ppm. the curing rate cannot be particularly expected to be improved.

[0090] The composition includes one or more electrically conductive fillers. The electrically conductive fillers can be selected from a conductive metal, a metal coated filler, or a mixture of two or more thereof. In embodiments, the conductive filler is selected from at least a metal coated filler.

[0091] Metal coated filler

[0092] The metal coated filler can be selected from a filler material comprising a conductive metal coating. The filler material coated with a conductive metal can be selected from a ceramic, glass, quartz, metal, carbon, or organic resin material typically in particulate form. The particles or filler coated with a metal for the metal coated fillers can have any shape or morphology7as selected for a particular purpose or intended application. The fillers can be flakes, spheres, rods, elongated, and the like. In one embodiment the filler particles are carbon selected from graphite, carbon black, carbon fibers, carbon nanotubes, carbon nanostructures, fragments of carbon nanostructures, fractured carbon nanotubes, elongated carbon nanostructure strands dispersed carbon nanostructure or a combination of two or more thereof. The filler particles are coated with a metal in any suitable manner such as, but not limited to, vacuum deposition, plating, etc. The metal coating can be selected, for example, from nickel, silver, copper, gold, alloys of two or more thereof, and the like.

[0093] Examples of suitable metal coated fillers include, but are not limited to, nickel- coated graphite (NiG).

[0094] In one embodiment, the metal coated filler is present in an amount of from about 10 to about 90 wt.%, from about 20 wt.% to about 80 wt.%, or from about 30 wt.% to about 70 wt.% based on the total weight of the composition.

[0095] The metal coated fillers can have an average particle size of from about 1 pm to about 200pm. from about 10 pm to about 150 pm. from about 25 pm to about 140 pm. the average particle size is measured by dynamic light scattering or image analysis techniques.

[0096] In one embodiment, the composition comprises a first metal coated filler of a first particle size (or particle size range), and a second metal coated filler of a second particle size (or particle size range). The first metal coated filler and the second metal coated filler may have the same chemical composition, e.g., both are nickel-coated graphite, or the first and second metal coated fillers may be of different chemical compositions. In one embodiment, the first metal coated filler has an average particle size of from about 50 pm to about 150 pm, from about 60 pm to about 120 pm, from about 70 pm to about 110 pm, and the second filler has an average particle size of from about 100 pm to about 200 pm , 125 pm to about 180 pm. from about 130 pm to about 160 pm, or.

[0097] In one embodiment, the amount of the first metal coated filler is from about 1 wt.% to about 100 wt.%, from about 5 wt.% to about 95 wt.%, or from about 10 wt.% to about 90 wt.%. preferably 80-90% based on the total weight of the first and second metal coated fillers, and the second metal coated filler is present in an amount of from about 0 to about 99 wt.%, from about 1 wt.% to about 50 wt.%, from about 2 wt.% to about 40 wt.%, or from about 5 wt.% to about 35 wt.%, preferably 10 to 20% based on the total weight of the first and second metal fillers. In one embodiment, the amount of the first metal coated filler is from about 60 wt.% to about 90 wt.%, from about 65 wt.% to about 85 wt.%, or from about 75 wt.% to about 80 wt.% based on the total weight of the first and second metal coated fillers, and the second metal coated filler is present in an amount of from about 10 wt.% to about 40 wt.%, from about 15 wt.% to about 35 wt.%. or from about 20 wt.% to about 25 wt.% based on the total weight of the first and second metal fillers. In one embodiment, the first metal coated filler is about 85 wt.% and the second metal coated filler is about 15 wt.% based on the total weigh of the first and second metal coated fillers. In one embodiment, the first and second metal coated fillers are each selected from nickel-coated graphite.

[0098] For the metal coated fillers, the metal coating is present in an amount of from about 5 wt.% to about 80 wt.%, from about 10 wt.% to about 65 wt.%, from about 20 wt.% toabout 50 wt.%, or from about 25 wt.% to about 30 wt.% based on the total weight of the metal coated filler. In one embodiment, the metal coating is about 60 wt.% based on the total weight of the filler.

[0099] The first and second metal coated fillers may, in embodiments, independently have an apparent density of from about 1 g / cm3to about 2 g / cm3, from about 1.2 g / cm3to about 1.8 g / cm3, or from about 1.4 g / cm3to about 1.6 g / cm3. The apparent density may be determined, for example according to ASTM B212.

[0100] Carbon based filler

[0101] The composition includes a carbon based filler. The carbon based filler can be selected from graphite, carbon black, carbon fibers, carbon nanotubes, carbon nanostructures, fragments of carbon nanostructures, fractured carbon nanotubes, elongated carbon nanostructure strands dispersed carbon nanostructure or a combination of two or more thereof.

[0102] The composition, in embodiments, comprises carbon nanotube structures as an additional conducting filler. Carbon nanostructures (CNS), as used herein, refers to a plurality of carbon nanotubes (CNTs) that are crosslinked in a polymeric structure. The crosslinked carbon nanotubes forming the CNS can be branched, interdigitated, entangles, and / or share common walls with one another. The carbon nanostructures may include fragments, fractured CNTs, and / or elongated CNS strands. In a CNS structure, it is not necessary7that every' carbon nanotube be branched, crosslinked, or share a common wall with another CNT. The carbon nanotubes forming the carbon nanostructures can be single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs). Multi-walled carbon nanotubes may comprise 2 or more concentric walls.

[0103] The morphology of CNTs present in a CNS, in a fragment of a CNS, or in a fractured CNT derived from a CNS will often be characterized by a high aspect ratio, with lengths typically more than 100 times the diameter, and in certain cases much higher. For instance, in a CNS (or CNS fragment), the length to diameter aspect ratio of CNTs can be within a range of from about 200 to about 1000.

[0104] In embodiments, the carbon nanostructures have a surface area of 100 m2 / g or greater. In embodiments, the carbon nanostructures have a surface are of 100 m2 / g to about 500 m2 / g, from about 150 m2 / g to about 450 m2 / g, or from about 175 m2 / g to about 400 m2 / g. In one embodiment, the carbon nanostructures have a surface area of from about 150 m2 / g to about 300 m2 / g, or from about 200 m2 / g to about 250 m2 / g.

[0105] The carbon nanotube structures can be coated. Coating of carbon nanostructures may also be referred to herein as sizing or encapsulating. The coating can be a partial orcomplete coating of the carbon nanostructures. The coating can be selected as desired for a particular purpose or intended application. Examples of suitable coatings include, but are not limited to, epoxy, polyester, vinyl ester, polyetherimide, polyetherketoneketone, polyphthalamide, polyether ketone, polyetheretherketone, polyimide, phenol-formaldehyde, bismaleimide, acrylonitrile-butadicne sty rene (ABS), polycarbonate, polyethyleneimine, polyurethane, polyvinyl chloride, polystyrene, polyolefins, polypropylenes, polyethylenes, polytetrafluoroethylene, elastomers such as, for example, polyisoprene, polybutadiene, butyl rubber, nitrile rubber, ethylene-vinyl acetate polymers, siloxane-based polymers, fluorosilicone polymers, combinations thereof, or other polymers or polymeric blends. Some specific examples of suitable coatings include, but are not limited to, poly(vinyldifluoroethylene) (PVDF), poly(vinyldifluoroethylene-co-hexafluoropropylene) (PVDF-HFP), polytetrafluoroethylene) (PTFE), polyimides, and water-soluble binders, such as poly (ethylene) oxide, poly viny 1-al cohol (PVA), cellulose, carboxy methylcellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone (PVP), a polyurethane (PU), a thermoplastic polyurethane (TPU), polyethylene glycol (PEG), and copolymers and mixtures thereof.

[0106] Carbon nanostructures may be prepared by any suitable method or process include those as described in, but not limited to, U.S. Patent Application Publication No. 2014 / 0093728, and U.S. Pat. Nos. 8.784,937; 9,005,755; 9,107,292; and 9,447,259. The entire contents of these documents are incorporated herein by this reference.

[0107] The carbon nanostructures can be present in an amount of from about 0.05 wt.% to about 2 wt.%, from about 0.08 wt.% to about 1.5 wt.%, from about 0. 1 wt.% to about 1 wt.%, or from about 0.25 wt.% to about 0.5 wt.% based on the total weight of the composition.

[0108] The composition may optionally comprise one or more additional fillers other than an electrically conductive filler. Additional fillers can be added to support other properties such as reinforcement, strength, etc. Examples of suitable additional fillers include, but are not limited to, alumina, silicon, magnesia, ceria, hafnia, lanthanum oxide, neodymium oxide, samaria, praseodymium oxide, thoria, urania, yttria, zinc oxide, zirconia, silicon aluminum oxynitride, borosilicate glasses, barium titanate, silicon carbide, silica, modified silica, boron carbide, titanium carbide, zirconium carbide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, zirconium nitride, zirconium boride, titanium diboride, aluminum dodecaboride, bary tes, barium sulfate, asbestos, barite, diatomite, feldspar, gypsum, hormite, kaolin, mica, nepheline syenite, perlite, phyrophyllite, smectite, talc, vermiculite, zeolite, calcite, calcium carbonate, wollastonite, calcium metasilicate, clay, aluminum silicate, talc,magnesium aluminum silicate, hydrated alumina, hydrated aluminum oxide, silica, silicon dioxide, modified silica, titanium dioxide, glass fibers, glass flake, clays, exfoliated clays, or other high aspect ratio fibers, rods, or flakes, calcium carbonate, zinc oxide, magnesia, titania, calcium carbonate, talc, mica, wollastonite, alumina, aluminum nitride, silicon carbide, silicon nitride, aluminum nitride, zinc oxide, boron nitride nanosheets, zinc oxide nanotubes, and combinations of two or more thereof.

[0109] Examples of modified silica includes silica treated with a surface treating agent. Examples of suitable surface treating agents include, but are not limited to, alkyl groups, siloxanes, alkylsiloxanes, alkydsilanes, disilazanes, and the like. In embodiments, modified silica is selected from silica treated with disilazanes. An example of a suitable disilazane includes, but is not limited to. hexamethyldisilazane. In embodiments, the silica treated with the surface treatment agent is selected from fumed silica.

[0110] Various weight ratios of fillers are added to the composition to achieve desired properties for the hybrid composite. The additional fillers (i.e., those fillers other than the first metal filler, the second metal filler, and the carbon based filler) may be present in varied amounts. In embodiments, the additional filler(s). when included, may be present in an amount of from about 0.1 % to about 50 %, from about 0.5% to about 40%, from about 1% to about 30%, from about 2% to about 25%, from about 5% to about 20%, or from about 10% to about 15% by weight based on the total weight of the composition. In embodiments, the additional filler(s) may be present in an amount of from about 0 to about 2%. from about 0.1% to about 1.8%, from about 0.2% to about 1.5%, or from about 0.5% to about 1 % based on the total weight of the composition. In one embodiment, the composition comprises an additional filler selected from silica, a modified silica, or combination thereof, wherein the additional filler is present in an amount of from about 0 to about 2%. from about 0. 1 % to about 1.8%, from about 0.2% to about 1.5%, or from about 0.5% to about 1% based on the total weight of the composition.

[0111] In one or more embodiments, the curable composition has a total filler content in a range from about 5% to 80%. In some embodiments, the curable composition comprises the fillers in a range from about 20% to 80%. In some embodiments, the curable composition comprises the fillers in a range from about 20% to 60%. In some embodiments, the curable composition comprises the fillers in a range from about 25% to 80%. In some embodiments, the curable composition comprises the fillers in a range from about 30% to 75%. In some embodiments, the curable composition comprises the fillers in a range from about 40% to 60%. In some embodiments, the curable composition comprises the fillers in a range from about 50%to 80%. The percent is the total weight percent of the fillers based on the total weight of the composition.

[0112] Adhesion Promoter

[0113] The adhesion promoter or adhesion imparting agent is a component for improving the adhesion of a cured product of the composition to a substrate, such as glass, a metal, or a plastic. A compound having a functional group other than the hydrolyzable group of the above-mentioned crosslinking agent also can be used as an adhesion imparting agent.

[0114] Specific examples include an alkoxy silane or a hydride containing alkoxy silane.

[0115] Examples of alkoxy silane include vinyltrimethoxy silane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane. 3- glycidoxypropylmethyldimethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3- acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3- acryloxypropylmethyldimethoxysilane. 3-methacryloxypropylmethyldimethoxysilane, 3- methacryloxypropylmethyldiethoxysilane, tetramethoxy silane, tetraethoxysilane and tetrapropoxysilane.

[0116] In one embodiment, the alkoxy silane based adhesion promoter is selected from a 3-glycidoxypropyltrimethoxysilane and tetraethoxy silane.

[0117] In one embodiment, the hydride based alkoxy silanes, include, for example, a reaction product between 1.1.3.5.7-pentamethylcyclotetrasiloxane and 3- methacryloxypropyltrimethoxysilane.

[0118] Specifically, alkoxy silanes having side chains represented by the formula below are preferable.

[0120] wherein QI and Q2 are each independently an alkylene group, preferably a Cl- C4 alkylene group, and each R3 is a C1-C4 alkyl group.

[0121] Examples of such alkoxy silanes include the following compounds.

[0122] The adhesion promoter may be present in an amount of from about 0.01 wt.% to about 10 wt.%, from about 0.05 wt.% to about 7.5 wt.%, from about 0.1 wt.% to about 5wt.%, from about 0.5 wt.% to about 2.5 wt.%, or from about 1 wt% to about 2 wt.% based on the total weight of the composition. In one embodiment, the adhesion promoter is present in an amount of from about 0.1 wt.% to about 5 wt% based on the total weight of the composition.

[0123] In some embodiments, the curable composition further comprises a reactive diluent. The reactive diluent may include, but is not limited to, substituted glycidyl ether. The reactive diluent may include one or more solvents. Suitable solvents may include, but are not limited to, liquid hydrocarbons or silicone fluids. The hydrocarbon solvent may include hexane or heptane, a silicone fluid may include polydiorganosiloxane.

[0124] In some embodiments, the curable composition further comprises a rheology modifier, or flow additives. The rheology modifier may include, but is not limited to, silica, modified silica, tetrahydrolinalool, thermoplastic resin and polyvinyl acetals. The flow additives may include, but are not limited to silicone fluids, or acrylated copolymers.

[0125] In one or more embodiments, the formulation is prepared by homogenizing a siloxane polymer and the filler in presence of catalyst. The appropriate components, e.g., siloxane, crosslinkers, catalysts, etc. for a t pe curing system are mixed with filler in a highspeed mixer. For condensation curable compositions, a mixture of the respective materials is cured at room temperature. For addition curable compositions, curing may be carried out by heating a mixture of the materials such as, for example, at a temperature of from about 80 to about 120 °C for 30 to 60 minutes. A series of examples (as shown in the examples below) are prepared by using the cured composition. In one embodiment, the curing of the curable composition is a condensation curing. In another embodiment, the curing of the curable composition is an addition curing.

[0126] In some embodiment, the application of the cured material and its end use is in coatings, adhesive, gaskets, sealants, electrodes, ink, thermally conductive material, electrically conductive material, sensors, actuators, heating pad, antibacterial packaging material, conductive plastic, electromagnetic shielding material.

[0127] This written description uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

[0128] EXAMPLES

[0129] The following examples are intended to illustrate aspects and embodiments of the present technology. All parts and percentages are by weight and all temperatures are in Celsius unless explicitly stated otherwise. All patents, other publications, and U.S. patent applications referred to in the instant application are incorporated herein by reference in their entireties.

[0130] Process flow for condensation cure systems: Carbon nanostructure filler was dispersed in Both ends methyldimethoxysilyl group-terminated poly dimethylsiloxane using a speed mixer at around 2350 rpm for 3 minutes. MQ Resin in siloxane and Both ends Trimethoxysilyl terminated poly dimethylsiloxane were added and again mixed at 2350 rpm for 1 minute. Fillers were added one by one, and the sequence of filler addition was based on particle size, the smaller one was added first followed by larger sizes. After every addition, the composition was mixed at 1500-2000 rpm for 1 minute. Once the fillers are dispersed well, crosslinker and additives were added and mixed again for 1-2 min at 1500-2000rpm. Finally, the catalyst was added, purged nitrogen, and mixed at 1500-2000rpm for 2-3minutes. Formulation was stored under nitrogen in sealed condition.

[0131] Testing of condensation cure system: The prepared formulation was then dispensed to a Teflon mold of 2mm thick and squeezed with a metal plate to form a uniform sheet. This sheet was then allowed to cure under room temperature conditions for 7 days before testing. Similarly for adhesion specimen preparation, formulation was dispensed onto the substrates at 1mm thickness and allowed to cure for 7 days.

[0132] Process flow for addition cure system: Vinyl polymers were weighed and mixed using a speed mixer at 2350rpm for 1 minute. Carbon nanostructure filler was dispersed in this solution using a speed mixer at around 2350 rpm for 3 minutes. Fillers were added one by one, and the sequence of filler addition was based on particle size, the smaller particles were added first followed by larger sizes. After every addition, the composition was mixed at 1500-2000 rpm for 1 minute. Once the fillers are dispersed well, catalyst, inhibitor, crosslinkers and adhesion promoters were added in the same sequence and mixed for Imin at 1500-2000 rpm after each addition. Formulation was stored at <10°C sealed condition.

[0133] Testing of addition cure system: The prepared formulation was then dispensed to a Teflon coated mold of 2mm thick and compression molded at 120°C for 30min to form a uniform sheet. Similarly for adhesion specimen preparation, formulation was dispensed onto the substrates at 1mm thickness and allowed to cure at 120°C for 30min.

[0134] Tensile and elongation properties were tested using ASTM D412 method using Instron at a pull speed was 200mm / min.

[0135] Volume resistivity of the cured sheet was checked using ASTM D 991.

[0136] EMI shielding effectiveness was checked using Vector Network Analyzer method (8-12GHz).

[0137] Electrical conductivity of the cured sheet was measured using a Four Probe method.

[0138] The lap shear adhesion of the developed formulations was measured using the ASTM D3163 standard using an Instron instrument. The substrate was cleaned with MEK / IPA and allowed to evaporate the solvent and sample was applied onto it. Test was performed using Instron with a pull speed of lOmm / min. Sample thickness of 1 mm and area of 10-20mm x 25mm were used.

[0139] Hardness of the developed composites was measured according to ASTM D2240 standard.

[0140] Compression set was measured for certain examples using the ASTM D395 text fixture. Test specimens which are in the form of cylindrical disc of about 6mm thickness were compressed up to 25% of their size. This fixture assembly was placed in an oven maintained at 125 °C for 22 hours. After removing the sample from the oven, the specimen is allowed to cool for 30 minutes before measuring the final thickness. The value of percentage decrease thus derived indicates the percentage a material sample fails to recover of its original size. The compression set is stated as a percentage of the original deflection.

[0141] Nickel-Graphite and Carbon nanostructures

[0142] Compositions were made employing nickel-coated graphite and carbon nanostructures. The materials employed and compositions are described below.

[0143] Polymers were selected from the following materials:

[0144] Table 1

[0145] Crosslinkers, adhesion promoters and inhibitor were selected from the following materials:

[0146] Table 2

[0147] The catalyst was selected from ethyl acetoacetonate titanate, and Pt catalyst 1 which is vinyl dimer complex with 2% Pt content and Pt catalyst 2 which is a vinyl tetramer complex with 1.8% Pt content.

[0148] The carbon nanostructures and nickel coated graphite are:

[0149] Carbon nanostructures ATHLOS SR 1200 having surface area 200 m2 / g was purchased either from CABOT Corporation. USA.

[0150] Nickel coated Graphite EFill 2701 having average particle size 100 micron and 60Ni / 40C was purchased from Oerlikon Metco Canada.

[0151] Nickel coated Graphite EFill 2702 having having average particle size 135 micron and 60Ni / 40C was purchased from Oerlikon Metco Canada.

[0152] Nickel coated Graphite having 300 mesh particle size and 75Ni / 25C was purchased from Chengdu Nuclear 857 New Materials, China.

[0153] Nickel coated Graphite having 200 mesh particle size 75Ni / 25C was purchased from Chengdu Nuclear 857 New Materials, China.

[0154] Modified Silica 1 (Aerosil R8200)is hydrophobic fumed silica modified with hexamethyldisilazane (HMDS) and having specific surface area (BET) of 135-185 m2 / g.

[0155] Modified silica 2 is hydrophobic silica prepared by treating a high purity fumed silica with hexamethyldisilazane (Reolosil HM-30S) having specific surface area (BET) of 185-225 m2 / g Alkoxy silyl isocyanurate or Tris[3-(trimethoxysilyl)propyl] isocyanurate is isocyanurate based adhesion promoter having following structure

[0156] Hydride based adhesion promoter 1 is a reaction product of 1, 1,3, 5,7- pentamethylcyclotetrasiloxane and 3-methacyloxypropyltrimethoxysilane.

[0157] Hydride based adhesion promoter 2 is a reaction product of 1, 1,3, 5,7- pentamethylcyclotetrasiloxane and 3-methacyloxypropyltrimethoxysilane which is partially condensed and polymerized.

[0158] Pt catalyst 1 is a Pt complex obtained by heating chloroplatinic acid and 1, 3,5,7- tetramethylcyclotetrasiloxan and having a platinum content of 1.8% by weight.

[0159] Pt catalyst 2 is a l,3-diethenyl-l,l,3,3-tetramethyldisiloxane complex of Pt and having a platinum content of 2% by weight.

[0160] The compositions are described in Tables 3-6 below.

[0161] Condensation Curable compositions are described in Table 3 and Table 4

[0162] Table 3*ND: Not determined

[0163] Tabled

[0164] Comparing Table 3 and Table 4, low EMI shielding, and electrical conductivity was observed when a combination of CNS with Nickel coated Graphite (60Ni / 40C ) were not used in the formulations (CE-1, CE-2 and CE-4 and CE-5).

[0165] To improve the EMI shielding and electrical conductivity of the formulations, different quantities of Nickel coated Graphite (60Ni / 40C) were used (Table 1). As can be seen from table 4, examples 1 to 6 have EMI shielding greater than 17 dB with electrical conductivity >10‘4S / cm.

[0166] Addition Curable compositions described in Table 5 and Table 6

[0167] Table 5Table 6

[0168] Six different optimization runs for compositions comprising CNS and combination of Nickel coated Graphite having average particle size 100 micron and 60Ni / 40C and Nickel coated Graphite having average particle size 135 micron and 60Ni / 40C achieving good EMI shielding and electrical conductivity are shown in Table 6.

[0169] Comparing Table 5 and Table 6, when a combination of CNS with Nickel coated Graphite (60Ni / 40C ) were not used in the formulations (CE-1) , low EMI shielding, and electrical conductivity was observed.

[0170] To improve the EMI shielding and electrical conductivity of the formulations, different quantities of Nickel coated Graphite (60Ni / 40C) were used (Table 1). As can be seen from table 6, examples 7 to 12 have EMI shielding >25 dB with electrical conductivity greater than > 9.3 x 10'3S / cm. These compositions also show excellent tensile strength, elongation, and adhesion.

[0171] Embodiments of the present technology have been described above and modification and alterations may occur to others upon the reading and understanding of this specification. The claims as follows are intended to include all modifications and alterations insofar as they come within the scope of the claims or the equivalent thereof.

Claims

CLAIMSWhat is claimed is:1 . A curable silicone composition, comprising: a siloxane polymer; first metal coated filler having a first particle size, and the second metal coated filler having a second particle size different from that of the first metal coated filler; a carbon based filler; and a catalyst.

2. The curable composition of claim 1, wherein the first metal coated filler and the second metal coated filler are each independently selected from a filler particle coated with a metal selected from nickel, silver, copper, gold, or an alloy of tw o or more thereof.

3. The curable composition of claim 2, wherein the filler particle is selected from a ceramic, glass, quartz, metal, carbon, or organic resin material.

4. The curable composition of claim 3, wherein the filler particle is a carbon selected from graphite, carbon black, carbon fibers, carbon nanotubes, or a combination of tw o or more thereof.

5. The curable composition of claim 1, wherein first and second metal coated fillers are each selected from nickel-coated graphite.

6. The curable composition of claim 4 or 5, wherein the first metal coated filler has an average particle size of from above 50 pm to about 150 pm, and the second filler has an average particle size of from above 100 pm to about 200 pm.

7. The curable composition of any of claims 1 to 6, wherein the first metal coated filler is from about 15 wt.% to about 95 wt.%, and the second metal coated filler is present in an amount of from about 5 wt.% to about 85 wt.% based on the total weight of the first and second metal fillers.

8. The curable composition of any of claims 6 to 7, wherein first and second metal coated fillers are each selected from nickel-coated graphite having an angular or flaky shape.

9. The curable composition of any of claims 6 to 7, wherein the first metal coated filler has an apparent density of 1 to 2 g / cm3.

10. The curable composition of any of claims 6 to 7, wherein the second metal coated filler has an apparent density of 1 to 2 g / cm3.

11. The curable composition of any of claims 1 to 10, having a total content of the first and second metal coated filler in an amount of from about 35 to about 70 wt.% based on the total weight of the composition.

12. The curable composition of any of claims 1-11, wherein the carbon based filler is selected from graphite, carbon black, carbon fibers, carbon nanotubes, carbon nanostructures, fragments of carbon nanostructures, fractured carbon nanotubes, elongated carbon nanostructure strands dispersed carbon nanostructure or a combination of two or more thereof.

13. The curable composition of claim 12, wherein the carbon nanostructures include a plurality of single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) that are crosslinked in a polymeric structure by being branched, interdigitated, entangled and / or sharing common walls14. The curable composition of any of claims 12 or 13, wherein the carbon nanostructures have a surface area of 100 m2 / g or greater.

15. The curable composition of any of claims 14, wherein the carbon nanostructures have a surface area of 150-300m2 / g or greater.

16. The curable composition of any of claims 1 to 15, wherein the carbon nanostructures are present in an amount of from 0.05 wt.% to about 2 wt.% based on the total weight of the composition.

17. The curable composition of any of claims 1 to 16 further comprising an additional filler selected from a filler other than the first metal filler, the second metal filler, and the carbon based filler.

18. The curable composition of claim 17, wherein the additional filler is selected from alumina, magnesia, ceria, hafnia, lanthanum oxide, neodymium oxide, samaria, praseodymium oxide, thoria, urania, yttria, zinc oxide, zirconia, silicon aluminum oxynitride, borosilicate glasses, barium titanate, silicon carbide, silica, modified silica, boron carbide, titanium carbide, zirconium carbide, boron nitride, silicon nitride, aluminum nitride, titanium nitride, zirconium nitride, zirconium boride, titanium diboride, aluminum dodecaboride, barytes, barium sulfate, asbestos, barite, diatomite, feldspar, gypsum, hormite, kaolin, mica, nepheline syenite, perlite, phyrophyllite. smectite, talc, vermiculite, zeolite, calcite, calcium carbonate, wollastonite, calcium metasilicate, clay, aluminum silicate, talc, magnesium aluminum silicate, hydrated alumina, hydrated aluminum oxide, silica, modified silica, silicon dioxide, titanium dioxide, glass fibers, glass flake, clays, exfoliated clays, or other high aspect ratio fibers, rods, or flakes, calcium carbonate, zinc oxide, magnesia, titania, calcium carbonate, talc, mica, wollastonite, alumina, aluminum nitride, silicon carbide, silicon nitride, aluminum nitride, zinc oxide, boron nitride nanosheets, zinc oxide nanotubes, and combinations of two or more thereof.

19. The curable composition of claim 17, wherein the additional filler is selected from a modified silica comprising silica particles treated with a hydrphobizing agent.

20. The curable composition of any of claims 1 to 19, wherein the siloxane polymer comprises a hydrolysable silyl and / or alkoxy functional group.

21. The curable composition of any of claims 1 to 20, wherein the siloxane polymer comprises at least one or more alkenyl functional groups; and at least one or more hydride functional groups22. The curable composition of any of claims 1 to 21, wherein the catalyst is a condensation and / or crosslinking catalyst.

23. The curable composition of claim 22, wherein the catalyst is selected from the group consisting of metal condensation catalysts and non-metal condensation catalysts.

24. The curable composition of any of claims 1 to 21, wherein the catalyst is a Hydrosilylation catalyst.

25. The curable composition of claim 24, wherein the hydrosilylation catalyst is selected from transition metal complexes, wherein suitable transition metal for the catalyst may include. Pt, Ru, Rh, Fe, Ni, Co26. The curable composition of any of claims 1 to 25 comprising a crosslinker.

27. The curable composition of any of claims 1 to 26 comprising an adhesion promoter.

28. A cured material of the curable composition of any of claims 1 to 27.

29. The cured material of claim 28, wherein the cured material has an electromagnetic interference (EMI) shielding efficiency between 15 to 50 dB as measured using Vector Network Analyzer method.

30. The cured material of claim 29, wherein the cured material has a volume resistivity between 200 to 500 Ohm-cm.

31. The cured material of any of claims 28 to 30, wherein the cured material has an electrical conductivity7between 10'4S / cm to 2 S / cm.

32. The cured material of any of claims 28 to 31, wherein the cured material is used in coatings, adhesives, sealants, gaskets, electrodes, ink, thermally conductive materials, electrically conductive materials, sensors, actuators, heating pad, antibacterial packaging materials, conductive plastics, or EMI shielding materials.

Images