WO2020132847A1

WO2020132847A1 - Silicone rubber compositions

Info

Publication number: WO2020132847A1
Application number: PCT/CN2018/123337
Authority: WO
Inventors: Shaohui Wang; Yusheng CHENG; Rui Wang; Bradley Jones
Original assignee: Dow Silicones Corporation
Priority date: 2018-12-25
Filing date: 2018-12-25
Publication date: 2020-07-02
Also published as: CN113227253B; CN113227253A

Abstract

A silicone rubber damping material having a high damping performance of (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃, the silicone rubber composition from which the material is made, a method for making the material and its uses are disclosed.

Description

SILICONE RUBBER COMPOSITIONS

This disclosure relates to silicone rubber elastomeric materials which may be used in damping applications and to the silicone rubber compositions from which they are cured.

Many engines and machines can generate unwanted and inefficient forms of energy created by e.g. vibration and/or noise when functioning. Often these effects may be limited or even prevented by the use of damping materials which are used to safely absorb and disperse the unwanted energy generated.

Silicone elastomeric materials are well known as damping materials for use in systems and applications requiring vibration damping and/or noise reduction, e.g. to decrease vibrations and noise transmitted from power and suspension devices and/or other machine/engine parts. They can also be used to limit the effect of e.g. shocks transmitted from foundations in building structures. These silicone elastomeric materials can be used to dampen vibrations in macro situations e.g. in automotive applications, e.g. road vehicles and trains, aircraft applications, industrial machinery applications, construction applications, i.e. building and bridge structures and/or they can be used in “micro” situations e.g. electronics and music systems. Specific examples include but are not limited to shock absorbers, vehicle suspension systems, vibroisolators, engine mounts, hydraulic systems, and for decreasing noise and vibrations between floors in multi-storey buildings.

Silicone elastomeric materials suitable to function as vibration dampers need to have the ability to support weight, e.g. of an engine/machine part, imparting heat resistance to high temperatures (>100℃. ) generated in and around engines during e.g. the running of a vehicle or machine whilst providing durability against repetitive loading. Silicone elastomeric materials are used in anti-vibration systems for e.g. automotive engine mounts, because of their excellent strength, fatigue resistance, high resilience and low level of strain sensitivity particularly at low temperatures but one of the most important aspects is that they can function over wide temperature ranges whilst e.g. vulcanized natural rubbers tends to degrade when used in high temperature environments (>100℃. ) which is a critical failing in the case of the latter given many of today’s engines etc. seek to function in environments at significantly greater temperatures than 100℃ in order to improve engine efficiency.

Because natural rubber is not allowed to be used in environments which function at > 100 ℃ or more, which is increasingly the case for e high-performance vehicles and due to regulations on exhaust gases, alternative synthetic organic rubber materials having better heat-resisting properties and ageing resistance have been proposed such as styrene butadiene rubber (SBR) , polybutadiene rubber (BR) , chloroprene rubber (CR) , nitrile butadiene rubber (NBR) , isobutylene isopropylene rubber (IIR) , and ethylene propylene diene monomer (EPDM) . However, the physical properties of such rubbers are still reasonably disappointing especially when subjected to wide temperature and frequency ranges. Silicone rubber materials have been found to provide a far more stable damping performance over said wide temperature and frequency ranges.

Known methods for improving the vibration damping characteristics of a silicone elastomeric material, obtained by hydrosilylation-induced curing in the presence of a platinum catalyst include those in which the content of silicon bonded alkenyl groups in an alkenyl group-containing polydiorganosiloxane is reduced, unreactive polydiorganosiloxanes may be added, and the content of the cross-linking agent in this composition is reduced or the like, to yield a low-hardness silicone gel.

Such low-hardness silicone gels tend to have poor shape retention properties because the gel material is very soft with having a very low mechanical strength. A lack of shape retention in the case of many vibration damping applications is clearly a major problem and as such these gel materials are only suitable for limited applications and/or situations. Whilst a gel has viscoelastic properties it is it’s viscous behavior which is the main contributor when used in damping applications and as such whilst it has acceptable damping properties it does not provide the elastic support needed and as such can’t be used in many if not most damping situations. Hence, for many applications alternative damping materials are required.

In order to solve the problem of the prior art, a silicone-based vibration damping rubber composition is described which, upon cure, provides the physical properties (e.g. tensile strength) of silicone rubber but also has excellent damping properties (tan delta > 0.1 over a temperature range of from -30℃ to 50℃) for damping vibration and as such is a suitable choice for a vibration damping silicone rubber.

Specifically, it is an object of the present invention to provide a vibration-proof rubber composition that cures by hydrosilylation to provide a rubber having excellent shape retention properties and superior vibration proofing characteristics across a wide range of temperatures and frequencies.

There is provided a silicone rubber damping material having a high damping performance of (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃; which material is the cured product of a composition comprising

(a) polydiorganosiloxane gum, having at least 2 alkenyl groups per molecule and a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, in an amount of 30 to 60%wt. of the composition;

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(d) an organohydrogenpolysiloxane containing at least two, alternatively at least 3 silicon bonded hydrogen atoms wherein the molar ratio of silicon bonded hydrogen atoms to Vi groups in the composition is from 0.75 : 1 to 2 : 1 , and

(e) a hydrosilylation catalyst.

There is provided a silicone rubber damping material having high damping performance having (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃, obtainable by curing a composition comprising

(a) polydiorganosiloxane gum, having at least 2 alkenyl groups per molecule and a Williams plasticity of at least30mm/100 measured in accordance with ASTM D-926-08, in an amount of 30 to 60%wt. of the composition;

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(e) a hydrosilylation catalyst.

The total weight %of the composition is always 100%wt. Tan delta was measured in the tensile mode using an RSA-G2 dynamic mechanical analysis testing apparatus from TA Instruments at a frequency of 1Hz and at 0.05%dynamic strain over a range of temperatures at a 2℃ per minute rate. Values of vinyl content are the cumulative totals of the weight %of vinyl groups in the composition, i.e. typically in gums/polymers, determined using quantitative infra-red spectroscopy in accordance with ASTM E168. Values of silicon bonded hydrogen atoms in weight %of the composition were also determined by infra-red spectroscopy in accordance with ASTM E168. Shore A hardness was measured in accordance with ASTM D2240.

It was found that once cured the viscoelastomeric product of the above composition provides excellent physical properties such as heat-resistance, ageing and durability in comparison with organic based rubber materials, as well as being sufficiently elastomeric to retain its shape, unlike previously discussed silicone gel. The present composition once cured provides viscoelastomeric characteristics but is far more elastomeric and far less viscous in nature compared to the gels and as such has additional tensile strength compared to the gels enabling the cured product of the present composition to be sufficiently strong and resistant to damaging stress in real applications. Whilst not being bound by current theories it is the viscous properties that provide damping while the elasticity of the product will resist permanent deformation and retain its original shape. The crosslinking degree of gel is much lower than a cured rubber.

There is provided a use of a silicone rubber composition comprising

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(e) a hydrosilylation catalyst;

which upon cure provides a high damping performance silicone rubber having (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃.

There is provided a method of making a silicone rubber damping material which once cured provides a high damping performance silicone rubber having (i) a Shore A hardness of >10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃, by mixing and curing a composition comprising

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(e) a hydrosilylation catalyst.

There is also provided a structure comprising or consisting of the silicone rubber material described above.

There is furthermore provided a silicone rubber composition which cures to form a silicone damping material having a high damping performance of (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃;

the composition comprising

(a) polydiorganosiloxane gum, having at least 2 alkenyl groups per molecule and a

Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, in an amount of 30 to 60%wt. of the composition;

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(e) a hydrosilylation catalyst;

The silicone rubber composition of the present disclosure can yield rubber with comparatively (with respect to at least gels) high hardness, (i.e. > than 10 shore A) , and having a high loss coefficient (i.e. tan delta > 0.1) when cured by hydrosilylation; which forms a vibration damping rubber possessing high shape retention capabilities. Polydiorganosiloxane gum (a)

Polydiorganosiloxane gum (a) has multiple units of the formula (I) :

R _aSiO _(4-a) /2 (I)

in which each R is independently selected from aliphatic hydrocarbyl, aromatic hydrocarbyl, or organyl group (that is any organic substituent group, regardless of functional type, having one free valence at a carbon atom) . Saturated aliphatic hydrocarbyls are exemplified by, but not limited to alkyl groups such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl and cycloalkyl groups such as cyclohexyl. Unsaturated aliphatic hydrocarbyls are exemplified by, but not limited to, alkenyl groups such as vinyl, allyl, butenyl, pentenyl, cyclohexenyl and hexenyl; and by alkynyl groups and the gum herein must contain at least two alkenyl groups per molecule. Aromatic hydrocarbon groups are exemplified by, but not limited to, phenyl, tolyl, xylyl, benzyl, styryl, and 2-phenylethyl. Organyl groups are exemplified by, but not limited to, halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3, 3, 3-trifluoropropyl; nitrogen containing groups such as amino groups, amido groups, imino groups, imido groups; oxygen containing groups such as polyoxyalkylene groups, carbonyl groups, alkoxy groups and hydroxyl groups. Further organyl groups may include sulfur containing groups, fluoro containing groups, phosphorus containing groups, boron containing groups. The subscript “a” is 0, 1, 2 or 3.

Siloxy units may be described by a shorthand (abbreviated) nomenclature, namely - "M, " "D, " "T, " and "Q" , when R is a methyl group (further teaching on silicone nomenclature may be found in Walter Noll, Chemistry and Technology of Silicones, dated 1962, Chapter I, pages 1-9) . The M unit corresponds to a siloxy unit where a = 3, that is R ₃SiO _1/2; the D unit corresponds to a siloxy unit where a = 2, namely R ₂SiO _2/2; the T unit corresponds to a siloxy unit where a = 1, namely R ₁SiO _3/2; the Q unit corresponds to a siloxy unit where a = 0, namely SiO _4/2.

Examples of typical functional groups on polydiorganosiloxane gum (a) include hydroxyl; alkoxyl; alkenyl, such as vinyl; alkyl such as methyl, or alkyl chains up to 8 carbon atoms; aryl, such as phenyl. The functional group may be in a pendent position (on a D or T siloxy unit) , or may be terminal (on an M siloxy unit) .

The polydiorganosiloxane gum (a) may be selected from polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpolysiloxanes, hydroxyl functional siloxanes, alkoxy functional siloxanes and mixtures thereof. They may be linear or branched or cyclic but typically will be linear or branched. The polysiloxanes may have any suitable terminal groups, for example, they may be trialkyl terminated, alkenyldialkyl terminated, hydroxydialkyl terminated, alkoxydialkyl terminated or may be terminated with any other suitable terminal group combination.

Polydiorganosiloxane gum (a) may further be selected from polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpolysiloxanes, hydroxyl functional siloxanes, and mixtures thereof having at least two alkenyl groups per molecule.

Examples of polydiorganosiloxane gum (a) are polydiorganosiloxanes containing alkenyl groups at the two terminals and are represented by the general formula (I) :

R'R"R"'SiO- (R"R"'SiO) _m-SiOR”'R"R' (I)

In formula (I) , each R'is an alkenyl group, which typically contains from 2 to 10 carbon atoms, such as vinyl, allyl, and 5-hexenyl.

R"does not contain ethylenic unsaturation, Each R"may be the same or different and is individually selected from monovalent saturated hydrocarbon radical, which typically contain from 1 to 10 carbon atoms, and monovalent aromatic hydrocarbon radical, which typically contain from 6 to 12 carbon atoms. R"may be unsubstituted or substituted with one or more groups that do not interfere with curing of this inventive composition, such as halogen atoms. R"'is R'or R". The letter m represents a degree of polymerization suitable for polydiorganosiloxane gum (a) to have a viscosity of at least 1,000,000mPa. s at 25℃.

The polydiorganosiloxane gum (a) typically has a viscosity of at least 1,000,000 mPa. s at 25℃. However, because of the difficulty in measuring viscosity above these values, gums tend to be described by way of their Williams plasticity values in accordance with ASTM D-926-08 as opposed to by viscosity. As hereinbefore stated the polydiorganosiloxane gum (a) has a viscosity resulting in a Williams’s plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, alternatively at least 50mm/100 measured in accordance with ASTM D-926-08, alternatively at least 100mm/100 measured in accordance with ASTM D-926-08, alternatively alternatively at least 125mm/100, alternatively 125mm/100 to 300mm/100 measured in accordance with ASTM D-926-08. Polydiorganosiloxane gum (a) is present in the composition in an amount of from 30 to 60%wt. of the composition;

(b) Reinforcing filler

Component (b) of the composition is a reinforcing filler such as finely divided silica. Silica and other reinforcing fillers (b) are often treated with one or more known filler treating agents to prevent a phenomenon referred to as "creping" or "crepe hardening" during processing of the curable composition.

Finely divided forms of silica are preferred reinforcing fillers (b) . Colloidal silicas are particularly preferred because of their relatively high surface area, which is typically at least 50 m ²/g (BET method in accordance with ISO 9277: 2010) . Fillers having surface areas of from 50 to 450 m ²/g (BET method in accordance with ISO 9277: 2010) , alternatively of from 50 to 300 m ²/g (BET method in accordance with ISO 9277: 2010) , are typically used. For the avoidance of doubt colloidal silicas as described herein may be can be provided in the form of precipitated silica and/or fumed silica. Both types of silica are commercially available.

The amount of reinforcing filler (b) e.g. finely divided silica in the composition herein is from 5 to 40%wt, alternatively of from 5 to 30%wt. In some instances, the amount of reinforcing filler may be of from 7.5 to 30%wt alternatively from 10 to 30%wt. based on the weight of the composition.

When reinforcing filler (b) is naturally hydrophilic (e.g. untreated silica fillers) , it is typically treated with a treating agent to render it hydrophobic. These surface modified reinforcing fillers (b) do not clump, and can be homogeneously incorporated into polydiorganosiloxane gum (a) as the surface treatment makes the fillers easily wetted by polydiorganosiloxane gum (a) . This results in improved room temperature mechanical properties of the compositions and resulting cured materials cured therefrom.

The surface treatment may be undertaken prior to introduction in the composition or in situ (i.e. in the presence of at least a portion of the other ingredients of the composition herein by blending these ingredients together at room temperature or above until the filler is completely treated. Typically, untreated reinforcing filler (b) is treated in situ with a treating agent in the presence of polydiorganosiloxane gum (a) , whereafter mixing a silicone rubber base composition is obtained, to which other ingredients may be added.

Typically reinforcing filler (b) may be surface treated with any low molecular weight organosilicon compounds disclosed in the art applicable to prevent creping of organosiloxane compositions during processing. For example organosilanes, polydiorganosiloxanes, or organosilazanes e.g. hexaalkyl disilazane, short chain siloxane diols or fatty acids or fatty acid esters such as stearates to render the filler (s) hydrophobic and therefore easier to handle and obtain a homogeneous mixture with the other ingredients. Specific examples include but are not restricted to silanol terminated trifluoropropylmethyl siloxane, silanol terminated ViMe siloxane, tetramethyldi (trifluoropropyl) disilazane, tetramethyldivinyl disilazane, silanol terminated MePh siloxane, liquid hydroxyl-terminated polydiorganosiloxane containing an average from 2 to 20 repeating units of diorganosiloxane in each molecule, hexaorganodisiloxane, hexaorganodisilazane. A small amount of water can be added together with the silica treating agent (s) as processing aid.

c) non-reinforcing filler

The composition herein may include one or more non-reinforcing fillers. Non-reinforcing filler (c) may comprise crushed quartz, diatomaceous earths, barium sulphate, iron oxide, titanium dioxide and carbon black, wollastonite and platelet type fillers such as, graphite, graphene, talc, mica, clay, sheet silicates, kaolin, montmorillonite and mixtures thereof. Other non-reinforcing fillers (c) which might be used alone or in addition to the above include aluminite, calcium sulphate (anhydrite) , gypsum, calcium sulphate, magnesium carbonate, aluminium trihydroxide, magnesium hydroxide (brucite) , graphite, copper carbonate, e.g. malachite, nickel carbonate, e.g. zarachite, barium carbonate, e.g. witherite and/or strontium carbonate e.g. strontianite.

Non-reinforcing fillers (c) may alternatively or additionally be selected from aluminium oxide, silicates from the group consisting of olivine group; garnet group; aluminosilicates; ring silicates; chain silicates; and sheet silicates. The olivine group comprises silicate minerals, such as but not limited to, forsterite and Mg ₂SiO ₄. The garnet group comprises ground silicate minerals, such as but not limited to, pyrope; Mg ₃Al ₂Si ₃O ₁₂; grossular; and Ca ₂Al ₂Si ₃O ₁₂. Aluninosilicates comprise ground silicate minerals, such as but not limited to, sillimanite; Al ₂SiO ₅ ; mullite; 3Al ₂O ₃.2SiO ₂; kyanite; and Al ₂SiO _5. The ring silicates group comprises silicate minerals, such as but not limited to, cordierite and Al ₃ (Mg, Fe) ₂ [Si ₄AlO ₁₈] . The chain silicates group comprises ground silicate minerals, such as but not limited to, wollastonite and Ca [SiO ₃] .

Suitable sheet silicates e.g. silicate minerals which may be utilised include but are not limited to mica; K ₂AI ₁₄ [Si ₆Al ₂O ₂₀] (OH) ₄; pyrophyllite; Al ₄ [Si ₈O ₂₀] (OH) ₄; talc; Mg ₆ [Si ₈O ₂₀] (OH) ₄; serpentine for example, asbestos; Kaolinite; Al ₄ [Si ₄O ₁₀] (OH) ₈; and vermiculite. When present, the non-reinforcing filler (s) is/are present up to a cumulative total of from 1 to 50%wt. of the composition,

In one embodiment the non-reinforcing filler (c) may be selected from the group of platelet non-reinforcing fillers such as, graphite, graphene, talc, mica, clay, layered silicates, kaolin (and/or kaolinite) , montmorillonite, pyrophyllite, and vermiculite and mixtures thereof. When non-reinforcing filler (c) is a platelet type filler, the non-reinforcing filler (c) may be present in a range of from 10 to 40 %by weight, alternatively 10 to 30%wt. of the composition.

Whenever deemed necessary the non-reinforcing filler (c) may also be treated as described above with respect to the reinforcing fillers (b) to render them hydrophobic and thereby easier to handle and obtain a homogeneous mixture with the other components. As in the case of the reinforcing fillers (b) surface treatment of the non-reinforcing fillers (c) makes them easily wetted by polydiorganosiloxane gum (a) which may result in improved properties of the compositions, such as better processability (e.g. lower viscosity, better mold releasing ability and/or less adhesive to processing equipment, such as two roll mill) , heat resistance, and mechanical properties.

d) Organohydrogenpolysiloxane Cross-linkers

The organohydrogenpolysiloxane (s) (d) , which operate (s) as cross-linker (s) for polydiorganosiloxane gum (a) will undergo a hydrosilylation (addition) reaction by way of its silicon-bonded hydrogen atoms with the alkenyl groups in polydiorganosiloxane gum (a) catalysed by one or more hydrosilylation catalysts discussed below. The organohydrogenpolysiloxane (d) normally contains 3 or more silicon-bonded hydrogen atoms per molecule so that the hydrogen atoms of this ingredient can sufficiently react with the alkenyl groups of polydiorganosiloxane gum (a) to form a network structure therewith and thereby cure the composition.

The molecular configuration of the organohydrogenpolysiloxane (d) is not specifically restricted, and it can be straight chain, branch-containing straight chain, or cyclic. While the molecular weight of this ingredient is not specifically restricted, the viscosity is typically from 0.001 to 50 Pa. s at 25 ℃ using a Brookfield DV-III Ultra Programmable Rheometer for viscosities ≥ 50,000 mPa. s, and a Brookfield DV 3T Rheometer for viscosities less than 50,000 mPa. s, unless otherwise indicated.

The organohydrogenpolysiloxane (d) is typically added in an amount such that the molar ratio of silicon bonded hydrogen atoms to Vi groups in the composition is from 0.75 : 1 to 2 : 1.

Examples of the organohydrogenpolysiloxane include but are not limited to:

(i) trimethylsiloxy-terminated methylhydrogenpolysiloxane,

(ii) trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane,

(iii) dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogensiloxane copolymers,

(iv) dimethylsiloxane-methylhydrogensiloxane cyclic copolymers,

(v) copolymers composed of (CH ₃) ₂HSiO _1/2 units and SiO _4/2 units, and

(vi) copolymers composed of (CH ₃) ₃SiO _1/2 units, (CH ₃) ₂HSiO _1/2 units, and SiO _4/2 units.

When present such cross-linkers are present the amount used is within the range described above, i.e. dependent on the molar ratio of silicon bonded hydrogen atoms to Vi groups discussed above but in terms of weight %they will typically be present in the composition in an amount somewhere within the approximate range of 2 to 10%by weight of the composition but this may vary depending on the cross-linker chosen.

e) Hydrosilylation catalyst

As hereinbefore described the composition is cured via a hydrosilylation reaction catalysed by a hydrosilylation (addition cure) catalyst (e) that is a metal selected from the platinum metals, i.e. platinum, ruthenium, osmium, rhodium, iridium and palladium, or a compound of such metals. The metals include platinum, palladium, and rhodium but platinum and rhodium compounds are preferred due to the high activity level of these catalysts for hydrosilylation reactions.

Example of preferred hydrosilylation catalysts (e) include but are not limited to platinum black, platinum on various solid supports, chloroplatinic acids, alcohol solutions of chloroplatinic acid, and complexes of chloroplatinic acid with ethylenically unsaturated compounds such as olefins and organosiloxanes containing ethylenically unsaturated silicon-bonded hydrocarbon groups. The catalyst (e) can be platinum metal, platinum metal deposited on a carrier, such as silica gel or powdered charcoal, or a compound or complex of a platinum group metal.

Examples of suitable platinum based catalysts include

(i) complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups are described in US 3,419,593;

(ii) chloroplatinic acid, either in hexahydrate form or anhydrous form;

(iii) a platinum-containing catalyst which is obtained by a method comprising reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound, such as divinyltetramethyldisiloxane;

(iv) alkene-platinum-silyl complexes as described in US Pat. No. 6,605,734 such as (COD) Pt (SiMeCl ₂) ₂ where “COD” is 1, 5-cyclooctadiene; and/or

(v) Karstedt's catalyst, a platinum divinyl tetramethyl disiloxane complex typically containing about 1 wt. %of platinum in a solvent, such as toluene may be used. These are described in US3,715,334 and US3,814,730.

The hydrosilylation catalyst (e) is present in the total composition in a catalytic amount, i.e., an amount or quantity sufficient to promote a reaction or curing thereof at desired conditions. Varying levels of the hydrosilylation catalyst (e) can be used to tailor reaction rate and cure kinetics. The catalytic amount of the hydrosilylation catalyst (e) is generally between 0.01 ppm, and 10,000 parts by weight of platinum-group metal, per million parts (ppm) , based on the combined weight of the components (a) , (b) and (c) , if the latter is present ; alternatively between 0.01 and 5000ppm; alternatively between 0.01 and 3,000 ppm, and alternatively between 0.01 and 1,000 ppm. In specific embodiments, the catalytic amount of the catalyst may range from 0.01 to 1,000 ppm, alternatively 0.01 to 750 ppm, alternatively 0.01 to 500 ppm and alternatively 0.01 to 100 ppm of metal based on the weight of the composition. The ranges may relate solely to the metal content within the catalyst or to the catalyst altogether (including its ligands) as specified, but typically these ranges relate solely to the metal content within the catalyst. The catalyst may be added as a single species or as a mixture of two or more different species. Typically, dependent on the form/concentration in which the catalyst package is provided the amount of catalyst present will be within the range of from 0.001 to 3.0%by weight of the composition.

Additives

Additives may be present in the composition depending on the intended use of the curable silicone elastomer composition. For example, given the composition is cured via hydrosilylation, inhibitors designed to inhibit the reactivity of the hydrosilylation catalysts may be utilised. Other examples of optional additives include electrical conductive fillers, thermally conductive fillers, non-conductive filler, pot life extenders, flame retardants, pigments, colouring agents, adhesion promoters, chain extenders heat stabilizers, compression set improvement additives and mixtures thereof.

Inhibitor

To obtain a longer working time or pot life of the silicone rubber composition when a dual cure system is being utilised, a suitable inhibitor may be incorporated into the composition in order to retard or suppress the activity of the catalyst.

Inhibitors of platinum metal based catalysts, generally a platinum metal based catalyst are well known in the art. Hydrosilylation or addition-reaction inhibitors include hydrazines, triazoles, phosphines, mercaptans, organic nitrogen compounds, acetylenic alcohols, silylated acetylenic alcohols, maleates, fumarates, ethylenically or aromatically unsaturated amides, ethylenically unsaturated isocyanates, olefinic siloxanes, unsaturated hydrocarbon monoesters and diesters, conjugated ene-ynes, hydroperoxides, nitriles, and diaziridines. Alkenyl-substituted siloxanes as described in US 3, 989, 887 may be used, of which cyclic methylvinylsiloxanes are preferred.

Another class of known inhibitors of platinum catalysts includes the acetylenic compounds disclosed in US 3, 445, 420. Acetylenic alcohols such as 2-methyl-3-butyn-2-ol constitute a preferred class of inhibitors that will suppress the activity of a platinum-containing catalyst at 25 ℃. Compositions containing these inhibitors typically require heating at temperature of 70 ℃ or above to cure at a practical rate.

Examples of acetylenic alcohols and their derivatives include 1-ethynyl-1-cyclohexanol (ETCH) , 2-methyl-3-butyn-2-ol, 3-butyn-1-ol, 3-butyn-2-ol, propargylalcohol, 2-phenyl-2-propyn-1-ol, 3, 5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclopentanol, 1-phenyl-2-propynol, 3-methyl-1-penten-4-yn-3-ol, and mixtures thereof.

When present, inhibitor concentrations as low as 1 mole of inhibitor per mole of the metal of catalyst (e) will in some instances impart satisfactory storage stability and cure rate. In other instances inhibitor concentrations of up to 500 moles of inhibitor per mole of the metal of catalyst (e) are required. The optimum concentration for a given inhibitor in a given composition is readily determined by routine experimentation. Dependent on the concentration and form in which the inhibitor selected is provided/available commercially, when present in the composition, the inhibitor is typically present in an amount of from 0.0125 to 10%by weight of the composition. Mixtures of the above may also be used.

Other Additives

Other commonly used additives may be present in the composition as and when required depending on the intended use of the curable silicone elastomer composition. Examples of additives include electrical conductive fillers, thermally conductive fillers, non-conductive filler, pot life extenders, flame retardants, pigments, colouring agents, adhesion promoters, chain extenders, heat stabilizers, compression set improvement additives and mixtures thereof.

Examples of electrical conductive fillers include metal particles, metal oxide particles, metal-coated metallic particles (such as silver plated nickel) , metal coated non-metallic core particles (such as silver coated talc, or mica or quartz) and a combination thereof. Metal particles may be in the form of powder, flakes or filaments, and mixtures or derivatives thereof.

Examples of thermally conductive fillers include boron nitride, aluminium nitride, silicon carbide, metal oxides (such as zinc oxide, magnesium oxide, and aluminium oxide, graphite, diamond, and mixtures or derivatives thereof.

Examples of non-conductive fillers include quartz powder, diatomaceous earth, talc, clay, alumina, mica, calcium carbonate, magnesium carbonate, hollow glass, glass fibre, hollow resin and plated powder, and mixtures or derivatives thereof.

Pot life extenders, such as triazole, may be used, but are not considered necessary in the scope of the present invention. The liquid curable silicone elastomer composition may thus be free of pot life extender.

Examples of flame retardants include aluminium trihydrate, magnesium hydroxide, calcium carbonate, zinc borate, wollastonite, mica and chlorinated paraffins, hexabromocyclododecane, triphenyl phosphate, dimethyl methylphosphonate, tris (2, 3-dibromopropyl) phosphate (brominated tris) , and mixtures or derivatives thereof.

Examples of lubricants include tetrafluoroethylene, resin powder, graphite, fluorinated graphite, talc, boron nitride, fluorine oil, silicone oil, phenyl functional silicone oil, molybdenum disulfide, and mixtures or derivatives thereof.

Further additives include silicone fluids, such as trimethylsilyl or OH terminated siloxanes. Such trimethylsiloxy or OH terminated polydimethylsiloxanes typically have a viscosity < 150 mPa. sat 25℃. When present such silicone fluid may be present in the liquid curable silicone elastomer composition in an amount ranging of from 0.1 to 5%weight, based on the total weight of the composition. Other additives include silicone resin materials, which may or may not contain alkenyl or hydroxyl functional groups.

Examples of pigments include carbon black, iron oxides, titanium dioxide, chromium oxide, bismuth vanadium oxide and mixtures or derivatives thereof.

Examples of colouring agents include vat dyes, reactive dyes, acid dyes, chrome dyes, disperse dyes, cationic dyes and mixtures thereof.

Examples of adhesion promoters include silane coupling agents, alkoxysilane containing methacrylic groups or acrylic groups such as methacryloxymethyl-trimethoxysilane, 3-methacryloxypropyl-tirmethoxysilane, 3-methacryloxypropyl-methyldimethoxysilane, 3-methacryloxypropyl-dimethylmethoxysilane, 3-methacryloxypropyl-triethoxysilane, 3-methacryloxypropyl-methyldiethoxysilane, 3-methacryloxyisobutyl-trimethoxysilane, or a similar methacryloxy-substituted alkoxysilane; 3-acryloxypropyl-trimethoxysilane, 3-acryloxypropyl-methyldimethoxysilane, 3-acryloxypropyl-dimethyl-methoxysilane, 3-acryloxypropyl-triethoxysilane, or a similar acryloxy-substituted alkyl-containing alkoxysilane; zirconium chelate compound such as zirconium (IV) tetraacetyl acetonate, zirconium (IV) hexafluoracetyl acetonate, zirconium (IV) trifluoroacetyl acetonate, tetrakis (ethyltrifluoroacetyl acetonate) zirconium, tetrakis (2, 2, 6, 6-tetramethyl-heptanethionate) zirconium, zirconium (IV) dibutoxy bis(ethylacetonate ) , diisopropoxy bis (2, 2, 6, 6-tetramethyl-heptanethionate) zirconium, or similar zirconium complexes having β-diketones (including alkyl-substituted and fluoro-substituted forms thereof) ; epoxy-containing alkoxysilanes such as 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl methyldimethoxysilane, 4-glycidoxybutyl trimethoxysilane, 5, 6-epoxyhexyl triethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, or 2- (3, 4-epoxycyclohexyl) ethyltriethoxysilane.

Examples of chain extenders include disiloxane or a low molecular weight polyorganosiloxane containing two silicon-bonded hydrogen atoms at the terminal positions. The chain extender typically reacts with the alkenyl groups of polydiorganosiloxane gum (a) , thereby linking two or more molecules of polydiorganosiloxane gum (a) together and increasing its effective molecular weight and the distance between potential cross-linking sites.

A disiloxane is typically represented by the general formula (HR ^a ₂Si) ₂O. When the chain extender is a polyorganosiloxane, it has terminal units of the general formula HR ^a ₂SiO _1/2 and non-terminal units of the formula R ^b ₂SiO. In these formulae, R ^a and R ^b individually represent unsubstituted or substituted monovalent hydrocarbon groups that are free of ethylenic unsaturation, which include, but are not limited to alkyl groups containing from 1 to 10 carbon atoms, substituted alkyl groups containing from 1 to 10 carbon atoms such as chloromethyl and 3, 3, 3-trifluoropropyl, cycloalkyl groups containing from 3 to 10 carbon atoms, aryl containing 6 to 10 carbon atoms, alkaryl groups containing 7 to 10 carbon atoms, such as tolyl and xylyl, and aralkyl groups containing 7 to 10 carbon atoms, such as benzyl.

Further examples of chain extenders include tetramethyldihydrogendisiloxane or dimethylhydrogen-terminated polydimethylsiloxane.

Where the optional additives may be used for more than one reason e.g. as a non-reinforcing filler and flame retardant, when present they may function in both roles. When or if present, the aforementioned additional ingredients are cumulatively present in an amount of from 0.1 to 30%wt, alternatively of from 0.1 to 20%wt based on the weight of the composition.

Hence, the composition as hereinbefore described may comprise

(a) polydiorganosiloxane gum, having at least 2 alkenyl groups per molecule and a Williams plasticity of at least 30mm/100, alternatively at least 50mm/100, alternatively at least 100mm/100, alternatively at least 125mm/100, alternatively 125mm/100 to 300mm/100 measured in accordance with ASTM D-926-08, in an amount of 30 to 60%wt. of the composition;

(b) a reinforcing filler in an amount of 5 to 40%wt., alternatively from 5 to 30%wt, alternatively from 7.5 to 30%wt., alternatively, 10 to 30%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(d) an organohydrogenpolysiloxane containing at least two, alternatively at least 3 silicon bonded hydrogen atoms wherein the molar ratio of silicon bonded hydrogen atoms to Vi groups in the composition is from 0.75 : 1 to 2 : 1, which will typically result in about 2 to 10%wt of organohydrogenpolysiloxane being present in the composition, dependent of the cross-linker selected and

(e) a hydrosilylation catalyst, present in a suitable amount, e.g. for the sake of example in an amount of from 0.1 to 500 parts by weight of platinum-group metal, per million parts (ppm) , based on the weight of the composition, with the total weight %of the composition being 100%wt.

Given the composition is cured via a hydrosilylation process the composition is typically stored in two parts prior to use. Typically catalyst (e) is placed in one part, often referred to as Part A and the cross-linker and if present the inhibitor, when present, is placed in the second part, often referred to as Part B. The other ingredients may typically be present in either or both compositions. The part A and Part B compositions are then mixed immediately prior to use. The mixing ratios by weight will depend on the level of ingredients in each part and can vary for part A to part B from about 15 : 1 to 1 to 1, typically dependent on whether components (a) and/or (b) are in both components and indeed the amounts in each. Typically in the present invention it is anticipated that more often than not components (a) and (b) will be in both parts in relatively equal amounts and therefore part A : Part B will be in a ratio of from 5 : 1 to 1 : 1, alternatively from 3 : 1 to 1 : 1.

The composition may be cured at any suitable temperature e.g. from 80℃ to 250℃, typically dependent on the curing agent (s) being used. The temperature for curing via hydrosilylation however is typically from 80℃ to 150℃, alternatively between 100℃ to 150℃, alternatively between 100℃ to 130℃.

The composition may be mixed or processed with any suituable processing equipment and/or mixers, such as a two roll mill, a kneader mixer, an internal mixer, an extruder or a calender machine.

The silicone rubber composition may be cured by any suitable means, such as for the sake of example a compression molding press, a transfer molding press, an injection machine, by hot air oven, by autoclave or even by way of a salt bath.

Silicone rubber elastomeric materials made from the composition described may be utilised in a wide range of applications. For example, they may be used to dampen vibrations/noise in macro situations such as in automotive applications, e.g. in road vehicles, trams, trains and aircraft applications; in industrial machinery applications; in construction applications, i.e. building and bridge structures and/or they can be used in “micro” situations e.g. for damping electronics and music/acoustic systems. Specific examples include but are not limited to shock absorbers, vehicle suspension systems, vibroisolators, engine mounts, bushes, hydraulic systems, for decreasing shocks, noise and vibrations between floors in multi-storey buildings; noise and vibration reduction in washing machines and dryers and also in electronic devices such as in loud speakers, mobile phones, laptops and televisions, drones and the like

The following examples, illustrating the compositions and components of the compositions, elastomers, and methods, are provided to illustrate and not to limit the invention.

EXAMPLES

A series of comparative examples (Comps) and examples supporting the present disclosure were prepared in accordance with the compositions identified in Tables 1a (comparatives) , 2a (comparatives) and 3a (examples) . Each gum had a Williams plasticity value measured in accordance with ASTM D-926-08. All viscosities measured were done so at 25 ℃ using a Brookfield DV-III Ultra Programmable Rheometer for viscosities ≥ 50,000 mPa. s, and a Brookfield DV 3T Rheometer for viscosities less than 50,000 mPa. s, unless otherwise indicated.

Values of vinyl content are the cumulative totals of the weight %of vinyl groups in the composition, i.e. typically in gums/polymers, determined using quantitative infra-red spectroscopy in accordance with ASTM E168. Values of silicon bonded hydrogen atoms in weight %of the composition were also determined by infra-red spectroscopy in accordance with ASTM E168. The ratio of silicon bonded hydrogen atoms: vinyl groups in the composition is a molar ratio. The measurements taken using ASTM D412 used Die C, Modulus M100 means at 100%extension and modulus M300 means at 300%extension.

Table 1a

Table 1 b-vinyl and Si-H Contents

Comp 1

Comp 2

Comp 3

Comp 4

Vi in composition (wt. %)	.099	0.065	0.065	0.06
Si-H in composition (wt. %)		0.76	0.76
Si-H : Vi molar ratio		3.23

For the sake of comparison, despite having Si-H content, Comp 3 was cured using a peroxide curing agent and not by hydrosilylation using a platinum catalyst and as such Si-H : Vi ratio was not determined.

The filler (s) and filler treating agent (s) were first mixed with and evenly dispersed into the gum (s) to form a silicone rubber base.

In the case of peroxide cure comparatives in Table 1a, comps 1, 3 and 4, the peroxide curing agent was added and dispersed into the base and the compositions were press cured for 10 minutes at a temperature of 170℃.

In the case of Comp. 2 a two part composition was utilised. Part A, containing base and platinum catalyst and Part B containing the remaining ingredients including the crosslinker and inhibitor. In this instance part A and part B were mixed together in a 1 : 1 weight ratio and then mixed and press cured for 10 minutes at a temperature of 116℃.

Physical properties of the resultant elastomeric materials were then analysed as identified in Table 1c below using ASTM standards indicated.

Table 1c

	Comp 1,	Comp 2	Comp 3	Comp 4
Hardness (Shore A) (ASTM D2240)	60	54	36	38
Tensile strength, (MPa) (ASTM D412)	9.7	9.5	9.7	8.1
Modulus M100 (MPa) (ASTM D412)	2.85	1.67	0.80	0.65
Modulus M300 (MPa) (ASTM D412)	5.33	3.26	2.87	2.84
Elongation (%) (ASTM D412)	532	743	665	539
Tear strength (kN/m) (ASTM D624 Die B)	48.0	36.8	25.6	11.0

Dynamic mechanical analysis was used to determine Tan delta in the tensile (tension) mode (sometimes referred to as the Loss Factor) . Tan delta is = E”/E’where E”is the viscous (loss) modulus in the tensile mode and E’is the elastic (storage) modulus in the tensile mode. The storage and loss modulus in viscoelastic materials measure the stored energy, representing the elastic portion, and the energy dissipated as heat, representing the viscous portion. It varies with the state of the material being analysed, its temperature, and with the frequency.

Hence, It is effectively a measure of the ability of the elastomeric materials prepared from Comps 1 to 4 to absorb (and disperse) energy. The tan delta is ultimately an indication of the effectiveness of a material’s damping capabilities. The higher the tan delta, the greater the damping coefficient, the more efficient the material will be in effectively accomplishing energy absorption and dispersal. Tan delta was measured in the tensile mode using an RSA-G2 dynamic mechanical analysis testing apparatus from TA Instruments at a frequency of 1Hz and at 0.05%dynamic strain over a range of temperatures at a 2℃ per minute rate. The results for comps 1-4 are shown in Table 1d.

Table 1d loss Factor (Tan delta) –Tensile Mode

The stability factor is intended to show the variation of tan delta across the temperature. It was measured and is tan delta at -30℃/tan delta at 80℃. Generally for silicone rubber, in most cases the value of tan delta declines as temperature increases and as such the closer values are to the more stable was the value of tan delta across the temperature range of from -30 to +80℃. It will be appreciated based on the stability factor values above and in the examples below that the stability factor for the examples using compositions as hereinbefore described are generally closer to 1 than comparative compositions

_Further comparative compositions were prepared and cured in the same manner as the above. The compositions are provided in table 2a below.

Table 2a

In this instance because all the compositions were peroxide cure no Si-H containing materials were incorporated in the compositions but the vinyl content per composition is indicated in Table 2b below

Table 2b

Vi in composition (wt. %)	0.060	0.060	0.069
Si-H in composition (wt. %)	0	0	0

Again the physical properties of the resultant elastomeric materials were then analysed as identified in Table 2c below using ASTM standards indicated.

Table 2c

	Comp 5	Comp 6	Comp 7
Hardness (Shore A) (ASTM D2240)	32	40	63
Tensile strength, (MPa) (ASTM D412)	6.8	6.3	6.9
Modulus M100 (MPa) (ASTM D412)	0.52	0.51	3.18
Modulus M300 (MPa) (ASTM D412)	2.37	2.29	6.06
Elongation (%) (ASTM D412)	544	547	387
Tear strength (kN/m) (ASTM D624 Die B)	8.5	7.1	22.5

Similarly the Loss factor of the materials was determined as were the stability factors and these are all depicted in Table 2d below

Table 2d

Compositions of the_examples in accordance with the disclosure herein are depicted in Table 3a below

Table 3a

The vinyl content and Si-H content and molar ratio are shown in table 3b

Table 3b

	Ex. 1	Ex. 2	Ex. 3	Ex. 4
Vi in composition (wt. %)	0.012	0.012	0.014	0.014
Si-H in composition (wt. %)	0.57	0.50	0.56	0.56
Si-H/Vi molar ratio	1.19	1.19	1.24	1.24

It will be seen that when compared to the Comparatives above that less vinyl content gums were introduced in order to have a good control on the total crosslinking density once the silicone rubber was cured. At the same time, the crosslinker content was also controlled at relevant lower levels for the same objective.

The physical properties of the resultant examples of elastomeric materials were then analysed as identified in Table 3c below using ASTM standards indicated.

Table 3c

	Ex. 1	Ex. 2	Ex. 3	Ex. 4
Hardness (Shore A) (ASTM D2240)	27	12	37	42
Tensile strength, (MPa) (ASTM D412)	4.1	2.5	7.5	6.9
Modulus M100 (MPa) (ASTM D412)	0.36	0.20	0.46	0.81
Modulus M300 (MPa) (ASTM D412)	0.93	0.48	1.34	1.83
Elongation (%) (ASTM D412)	887	963	877	815
Tear strength (kN/m) (ASTM D624 Die B)	12.3	14.6	38.1	19.8

It can be seen that when compared with the comparatives above that the tan delta of the examples is much higher (almost all are in the range of 0.11～0.184 at all temperatures while for Comp samples in most cases it is in the range of 0.05～0.099) . That is, the tan delta value almost doubled. At the same time, compared with Comp samples, the stability factor of the examples is more close to 1.0, which means the higher tan delta could be well maintained over the wide temperature range of -30～+50℃ and in nearly all instances to +80℃. This is a very important characteristic when the application environment involves a relevant higher or lower temperature beyond a relevant narrow range around room temperature.

The tan delta (Loss factor) of the materials was determined as were the stability factors and these are all depicted in Table 3d bellows

Table 3d

	Ex. 1	Ex. 2	Ex. 3	Ex. 4
Tan delta at -30℃	0.153	0.167	0.114	0.145
Tan delta at 0℃	0.180	0.165	0.125	0.154
Tan delta at 25℃	0.176	0.149	0.114	0.146
Tan delta at 50℃	0.174	0.140	0.110	0.143
Tan delta at 80℃	0.184	0.127	0.079	0.132
Stability factor (tan delta at -30℃/tan delta at 80℃)	0.83	1.31	1.44	1.10

When compared with the comparative examples it will be seen that the tan delta values are much higher and as such it can be concluded that the examples herein are much better at absorbing and dispersing energy i.e. damping than the comparatives. Furthermore, the examples herein have a much narrower range of stability factors which indicates they are more stable over the temperature range tested or the material has quite similar damping performances at lower temperature end -30 and higher temperature end +80℃.

Claims

A silicone rubber damping material having a high damping performance of (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃; which material is the cured product of a composition comprising

(a) polydiorganosiloxane gum, having at least 2 alkenyl groups per molecule and a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, in an amount of 30 to 60%wt. of the composition;

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(d) an organohydrogenpolysiloxane containing at least two, alternatively at least 3 silicon bonded hydrogen atoms wherein the molar ratio of silicon bonded hydrogen atoms to Vi groups in the composition is from 0.75 : 1 to 2 : 1 , and

(e) a hydrosilylation catalyst;
A silicone rubber damping material having high damping performance having (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃, obtainable by curing a composition comprising

(a) polydiorganosiloxane gum, having at least 2 alkenyl groups per molecule and a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, in an amount of 30 to 60%wt. of the composition;

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(d) an organohydrogenpolysiloxane containing at least two, alternatively at least 3 silicon bonded hydrogen atoms wherein the molar ratio of silicon bonded hydrogen atoms to Vi groups in the composition is from 0.75 : 1 to 2 : 1 , and

(e) a hydrosilylation catalyst.
A silicone rubber damping material in accordance with claim 1 or 2 having a tan delta in the tensile mode of from 0.12 to 0.40 in a temperature range of from -30℃ to +80℃.
A silicone rubber damping material in accordance with any preceding claim having a shore A hardness of > 10 as measured in accordance with ASTM D2240.
A silicone rubber damping material in accordance with any preceding claim wherein the fluorinated polydiorganosiloxane gum used had a Williams plasticity of at least100mm/100 measured in accordance with ASTM D-926-08.
A silicone rubber damping material in accordance with any preceding claim comprising a non-reinforcing filler (c) selected from the group of graphite, graphene, talc, mica, clay, layered silicates, kaolin/kaolinite, montmorillonite, pyrophyllite, and vermiculite and mixtures thereof..
A structure comprising or consisting of a silicone rubber damping material in accordance with any preceding claim.
A method of making a silicone rubber damping material which once cured provides a high damping performance silicone rubber having (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from-30℃ to 50℃, by mixing and curing a composition comprising

(a) polydiorganosiloxane gum, having at least 2 alkenyl groups per molecule and a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, in an amount of 30 to 60%wt. of the composition;

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(d) an organohydrogenpolysiloxane containing at least two, alternatively at least 3 silicon bonded hydrogen atoms wherein the molar ratio of silicon bonded hydrogen atoms to Vi groups in the composition is from 0.75 : 1 to 2 : 1 , and

(e) a hydrosilylation catalyst.
A method in accordance with claim 9 wherein the composition is stored in two parts prior to mixing, a first part, Part A containing the catalyst (e) and second part, Part B containing the cross-linker (d) .
A silicone rubber composition which cures to form a silicone damping material having a high damping performance of (i) a Shore A hardness of > 10 and (ii) a tan delta of > 0.1 over a temperature range of from -30℃ to 50℃;

said composition comprising

(a) polydiorganosiloxane gum, having at least 2 alkenyl groups per molecule and a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, in an amount of 30 to 60%wt. of the composition;

(b) a reinforcing filler in an amount of 10 to 40%wt. of the composition;

(c) from 0 to 50 %wt of the composition of one or more non-reinforcing fillers;

(d) an organohydrogenpolysiloxane containing at least two, alternatively at least 3 silicon bonded hydrogen atoms wherein the molar ratio of silicon bonded hydrogen atoms to Vi groups in the composition is from 0.75 : 1 to 2 : 1 , and

(e) a hydrosilylation catalyst;
A silicone rubber composition in accordance with claim 10 wherein the polydiorganosiloxane gum (a) used had a Williams plasticity of at least100mm/100 measured in accordance with ASTM D-926-08.
A silicone rubber composition in accordance with claim 10 or 11 comprising a non-reinforcing filler (c) selected from the group of graphite, graphene, talc, mica, clay, layered silicates, kaolin/kaolinite, montmorillonite, pyrophyllite, and vermiculite and mixtures thereof.
A silicone rubber damping material in accordance with any one of claims 1 to 6 used to dampen vibrations and/or /noise in in automotive applications, in industrial machinery applications; in construction applications, or for damping electronics and music/acoustic systems.
A silicone rubber damping material in accordance with claim 14 used to dampen vibrations and/or /noise in shock absorbers, vehicle suspension systems, vibroisolators, engine mounts, bushes, hydraulic systems, for decreasing shocks, noise and vibrations between floors in multi-storey buildings; noise and vibration reduction in washing machines and dryers and also in electronic devices such as in loud speakers, mobile phones, laptops, drones, wearable electronic devices, and televisions.