Halogenated Polyethylene and Ethylene Polymer Blends

Abstract

A rubber composition comprising an ethylene polymer, particularly a blend of a halogenated ethylene polymer and a non-halogenated ethylene polymer. The composition contains 25 to 50 weight percent halogenated ethylene based on the total composition. In some embodiments, the non-halogenated ethylene polymer is an ethylene acrylic elastomer. The composition may contain an organic peroxide or other accelerator. The rubber composition is useful for synchronous belts, which have medium to high temperature resistance, good fuel resistance, flexibility down to -40°C, and high structural integrity. Furthermore, the rubber composition allows for reduced use of fossil-fuel-derived reinforcing materials such as carbon black.

Description

[Technical Field]

[0001] The present invention relates to compositions, particularly rubber compositions, for use in flexible belts such as synchronous belts that have medium to high temperature resistance, good oil resistance, flexibility down to -40°C, and high structural integrity. [Background technology]

[0002] HNBR is a hydrogenated version of NBR rubber, a synthetic rubber with very good heat resistance and excellent oil resistance, and is widely used in synchronous belt compounds to meet application requirements.

[0003] There is a need for alternative materials that meet the application requirements of synchronous belts, such as heat resistance and oil resistance. Summary of the Invention

[0004] This Summary is provided to introduce some concepts in a simplified form that are more fully described below in the Detailed Description. This Summary and the foregoing Background Information are not intended to identify key or essential aspects of the claimed subject matter, nor is this Summary intended to be used as an aid in determining the scope of the claimed subject matter.

[0005] The present disclosure relates to rubber compositions having polymer blends of ethylene terpolymers, particularly compositions containing halogenated polyethylene. The compositions contain 25 to 50 weight percent halogenated polyethylene based on the total composition. In some embodiments, the halogenated polyethylene is a chlorinated polyethylene rubber. In some embodiments, the ethylene polymer is an ethylene acrylic elastomer. In other embodiments, the ethylene polymer is an EPDM rubber (a well-known rubber made from ethylene, propylene, and a diene comonomer that allows crosslinking by sulfur vulcanization). The compositions may also contain organic peroxides or other accelerators.

[0006] This rubber composition is useful for synchronous belts, as it has medium to high temperature resistance, excellent oil resistance, flexibility down to -40°C, and high structural strength. Furthermore, this rubber composition makes it possible to reduce the amount of reinforcing materials such as carbon black used while maintaining the properties required for synchronous belts.

[0007] These and other aspects of the technology described herein will become apparent upon consideration of the detailed description and drawings herein, with the understanding that the scope of the claimed subject matter is determined by the claims as they are filed, and not by whether the subject matter addresses some or all of the problems described in the Background or includes features or aspects described in the Abstract. [Brief explanation of the drawings]

[0008] Non-limiting and non-exhaustive embodiments of the disclosed technology, including preferred embodiments, are described with reference to the following figures, in which like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0009] [Figure 1] 1 is a perspective view of an example of a belt made with a composition of the present disclosure. Detailed Description of the Invention

[0010] As described above, the present invention relates to a rubber composition having a polymer blend of at least two ethylene polymers, one of which is a halogenated polyethylene. Specifically, the composition comprises 25 to 50 wt % of the total blend of halogenated ethylene polymers such as polyethylene rubber, 10 to 30 wt % of the total blend of ethylene polymers, and the remainder of the composition is made up of components such as activators, fillers, curing agents, reinforcing agents, anti-degradants (e.g., antioxidants, UV stabilizers), plasticizers, antistatic agents, colorants, processing aids, homogenizing agents, co-reactants, and catalysts.

[0011] This composition can be cured with organic peroxides or accelerators. The cured composition exhibits a minimum Mooney viscosity of less than 60 MU when tested at 133°C. It maintains its physical properties, possessing excellent adhesive strength, a tensile strength of greater than 18 MPa, and heat resistance up to 135°C. The cured composition exhibits less than 20% volume expansion after 168 hours in IRM 901 oil at 135°C, demonstrating excellent oil resistance even at high temperatures. Furthermore, the cured composition maintains flexibility even at -35°C.

[0012] In the following description, reference is made to the accompanying drawings, which form a part of this specification. At least one specific embodiment is shown by way of example in the accompanying drawings. The following description also provides additional specific embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense. The present disclosure is not so limited, but rather various aspects of the disclosure can be appreciated through the description of the examples, including the figures set forth below. In some instances, a reference number may be associated with a sub-label consisting of a lower case letter to indicate one of multiple similar components. When a reference number is made without specifying a sub-label, the reference is intended to refer to all such multiple similar components.

[0013] The present disclosure relates to rubber compositions comprising a polymer blend of at least two ethylene polymers, one of which is a halogenated ethylene polymer. Specifically, the composition comprises 25-50 wt% (in some embodiments, 30-40 wt%) of the halogenated ethylene rubber and 10-30 wt% of the non-halogenated ethylene polymer, with the halogenated and non-halogenated ethylene polymers comprising 30-75 wt% (in some embodiments, 40-70 wt%) of the total composition. Chlorinated polyethylene rubber is one example of a suitable halogenated ethylene polymer. Examples of suitable non-halogenated ethylene polymers include EPDM rubber (a well-known rubber made from ethylene, propylene, and a diene comonomer that allows crosslinking by sulfur vulcanization) and ethylene acrylic polymers or elastomers. In some embodiments, the composition includes an organic peroxide or other accelerator added during curing. In some embodiments, the composition includes less than 15 wt% of the non-conjugated diene based on the weight of the ethylene polymer.

[0014] This rubber composition is ideal for synchronous belts in automotive and industrial applications, as the cured composition has medium to high temperature resistance, excellent oil resistance, flexibility down to -40°C, and high structural integrity.

[0015] FIG. 1 illustrates a typical belt 100. The belt 100 includes a body 102 formed of a flexible material having a back surface 104 and a front surface 106. A plurality of load-bearing cords 108 are disposed within the body 102. The cords 108 are shown in triplicate, although in other embodiments, the cords 108 may be single-stranded or otherwise bound. The cords 108 may be, for example, carbon cords, polymer cords (e.g., polyester, aramid), fiberglass cords, or the like. The front surface 106 defines a plurality of teeth 110. While the embodiment of FIG. 1 illustrates trapezoidal teeth, the shape of the teeth is not limited thereto and may be any shape compatible with a sprocket, gear, or other gearing. Each tooth 110 extends perpendicular to the length of the belt 100, and the plurality of teeth 110 are arranged circumferentially along the length of the belt 100. During use, the teeth 110 on the front surface 106 contact a drive mechanism, such as a gear or sprocket. Although not shown in FIG. 1, the belt 100 is an endless belt, and has a loop shape with no beginning or end.

[0016] The resulting blend of halogenated and non-halogenated ethylene polymers offers an ideal balance of heat resistance, aging resistance, ozone resistance, and solvent resistance. The composition also maintains sufficient flexibility at temperatures as low as -40°C, a requirement typically met for synchronous belts in automotive and industrial applications. Furthermore, when mixed with carefully selected adhesives, it exhibits excellent adhesion.

[0017] Halogenated ethylene polymers include, for example, chlorine (chlorinated), fluorine (fluorinated), and / or bromine (brominated). Examples of suitable halogenated ethylene polymers include chlorinated polyethylene rubber, polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluoroethylene vinyl ether (FEVE), fluorinated ethylene propylene (FEP), ethylene chlorotrifluoroethylene (EDTFE), and polychlorotrifluoroethylene (PCTFE).

[0018] Non-halogenated ethylene polymers suitable for blending with halogenated ethylene include ethylene acrylic elastomer, EPDM, ethylene propylene elastomer (EPM), ethylene butene (EBM), ethylene pentene, and ethylene octene (EOM).

[0019] The choice of polymer grade influences the flow characteristics of the blended compound. High molecular weight grades are unsuitable for synchronous belts in automotive applications because they have high Mooney viscosities, poor flow, and poor belt tooth formation. However, the final cured product (e.g., vulcanizate) has excellent physical properties, such as tensile strength, modulus, and elongation. On the other hand, low molecular weight grades improve flow, but the blended vulcanizate may lack sufficient physical strength. Commercially available ethylene polymers are available in halogenated and non-halogenated grades and with a variety of molecular weights (e.g., Mw, Mn). These polymers are characterized by Mooney viscosities (ML1+4 at 100°C) ranging from 30 to 90 MU.

[0020] The amount of ethylene polymer, both halogenated and non-halogenated, is 30% to 75% by weight of the total weight of the raw materials forming the uncured blend composition, with the halogenated ethylene polymer being 25% to 50% by weight of the total and the non-halogenated ethylene polymer being 10% to 30% by weight of the total. In some embodiments, the ethylene polymer is about 40% to 70% by weight of the total weight of the raw materials, and in other embodiments, about 45% to 60% by weight.

[0021] The weight ratio of halogenated ethylene to non-halogenated ethylene is from 3:1 to 1:1, and in some embodiments, the weight ratio of halogenated ethylene to non-halogenated ethylene is about 2:1.

[0022] EPDM is a terpolymer of ethylene and propylene, consisting of a saturated polymer backbone, a saturated non-conjugated diene monomer, and an ethylene-propylene copolymer. Examples of diene monomers contained in EPDM include dicyclopentadiene (DCPD), ethylidene norbornene (ENB), 1,4-hexadiene, and methylidene norbornene.

[0023] EPDM typically contains about 30 to about 80% by weight of ethylene and about 0 to about 15% of a non-conjugated diene. The diene content is typically identified by an iodine value of about 5 to about 30. The Mooney viscosity (ML1+4 at 125°C) is typically about 40 to about 100 MU. When the ethylene content exceeds 70% by weight, the EPDM polymer becomes crystalline.

[0024] In addition to the halogenated polyethylene polymer (rubber) and non-halogenated ethylene polymer, the blend composition may include additional rubber materials, including, but not limited to, styrene butadiene rubber (SBR), chloroprene rubber (CR), nitride butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), and fluoroelastomers (e.g., FKM).

[0025] The rubber stock (halogenated polyethylene, non-halogenated polyethylene, etc.) is often in the form of a solid powder, pellets, bales, or blocks, but in some embodiments may be liquid or semi-liquid.

[0026] As described above, the mixed composition can include an organic peroxide or other accelerator to accelerate the curing of the mixed composition. Various types of organic peroxides can be used in the mixed composition. The organic peroxides decompose at a specific temperature to generate radicals that initiate the crosslinking reaction in the compound. A specific example of an organic peroxide used in polyethylene is α,α-bis(t-butylperoxy)diisopropylbenzene. In some embodiments, the total amount of organic peroxide is less than about 3% by weight of the raw materials, and in other embodiments, it is less than about 2.5% by weight of the raw materials.

[0027] Polymer compositions cured with organic peroxides exhibit higher heat resistance due to the formation of C-C crosslinks between polymer chains. On the other hand, sulfur-cured polymers form C-S-C or C-(S)xC bonds. The formation of monosulfide (CS) or polysulfide (SS) bonds leads to a decrease in the heat resistance of the polymer. The C-C bond energy (346 kJ / mol) is higher than the C-S bond energy (272 kJ / mol) and the S-S bond energy (226 kJ / mol), which is reflected in the high heat resistance of peroxide-cured vulcanizates.

[0028] The blended composition may contain various additives such as activators, fillers, curing agents, reinforcing agents, anti-degradants (e.g., antioxidants, UV stabilizers), plasticizers, antistatic agents, colorants, processing aids, homogenizing agents, copolymerization agents, catalysts, etc. Generally, the total weight percent of additives is less than 75% by weight of the total composition ingredients, and in some embodiments, less than 65% by weight or less than 50% by weight.

[0029] Examples of active agents include stearic acid and zinc oxide.

[0030] Stearic acid is generally a solid, available in flake or pellet form, with a specific gravity of approximately 0.85. Stearic acid typically contains up to 10% iodine by weight. Its acid number ranges from 193 to 213. Zinc oxide is also a solid, e.g., with a surface area of ​​4 to 6 m. 2 It is a fine powder with a specific gravity of 5.6 at 1 / g. Zinc oxide may contain impurities such as CuO<0.0005 wt%, MnO<0.0005 wt%, SiO2<0.02 wt%, and / or water-soluble salts<0.05 wt%. In some embodiments, the total amount of activator is less than about 5 wt% of the feedstock, and in some embodiments, less than about 3 wt%. Long-chain fatty acids (LCFs) can be used as homogenizing agents and, when combined with zinc oxide, function as activators.

[0031] Any suitable curing agent or material that promotes or assists curing can be used. Examples of suitable curing agents include sulfur and peroxides. In some embodiments, the amount of curing agent used is less than about 8% by weight, for example, less than 5% by weight, of the total weight of the raw materials.

[0032] The addition of silica can improve the tensile strength, modulus, compression set, and abrasion resistance of the mixed composition. Silica is typically a solid (e.g., powder) and can be treated or untreated. The surface area of ​​silica is typically 120-200 m / g. For example, treated silica with 5-8 wt. % organosilane treatment has a specific gravity of 1.9-2.0. The volatile content of this silica is 3-5% and the pH is 6-8. The organosilane is a trialkoxysilane type. Therefore, the treated silica material has low hygroscopicity and generates significantly less volatile matter during mixing and processing. In some embodiments, the total amount of silica is about 10-35 wt. % of the raw materials.

[0033] Carbon black and / or graphite can be used as fillers in rubber compounds. Other fillers include metal oxides such as aluminum oxide, magnesium oxide, and zinc oxide, clay, Montrealonite clay, pulp, and mica.

[0034] The raw materials for the blended composition may include reinforcing materials such as chopped fiber segments, although other reinforcing materials such as elongated segments, fibers, nanotubes, etc. can also be used. The reinforcing materials, whether chopped or elongated, can be aramid, polyester (PET), cotton, nylon, glass, carbon fiber cord, hybrid cord, metals, ceramics, other plastics, etc. The reinforcing materials can be made from organic materials, synthetic materials, or a mixture of organic and synthetic materials.

[0035] The dimensions of the reinforcing material are generally not limited. In some embodiments, the chopped fibers have a high aspect ratio with lengths ranging from 0.2 mm to 3 mm. In some embodiments, the reinforcing material (e.g., chopped fibers or elongated materials) has an aspect ratio of 10 to 250. In some embodiments, the amount of reinforcing material is 5% to 30% by weight of the total weight of the raw materials. The reinforcing material is mixed with the raw materials, and the resulting belt has the reinforcing material uniformly dispersed throughout the mixed composition.

[0036] In some embodiments, the amount of filler (including silica, carbon black, or carbon reinforcing fiber) is between 5% and 45% by weight of the total raw material weight, while in other embodiments, the filler is between about 10% and about 20% by weight of the total raw material weight. Polymer blends of ethylene polymers allow for a reduction in the amount of carbon reinforcing fiber or other carbon and an increase in other fillers while maintaining acceptable properties for the synchronous belt. In some embodiments, the silica to reinforcing carbon ratio is between 5:1 and 3:1, e.g., about 4:1.

[0037] Polymers generally degrade when exposed to various environmental factors, including oxygen, heat / temperature, ultraviolet light, weathering, catalytic degradation by heavy metal ions, and dynamic fatigue. Failures observed in rubber compounds due to environmental degradation include a loss of elasticity and tensile strength, the formation of cracked surfaces, and the appearance of cracks. The presence of unsaturation in a polymer increases its propensity for failure due to thermal aging due to the allylic C-H bond in its unsaturated chemical structure. The bond energy of the allylic C-H bond is the weakest among the various types (primary, secondary, and tertiary) of C-H bonds. This factor promotes the formation of free radicals and peroxy radicals in the presence of oxygen and heat, resulting in chain scission. Once the polymer backbone is scissed, the compound begins to lose physical and mechanical strength and begin to degrade. Antioxidants function as radical traps, capturing radicals to prevent polymer chain scission and thereby improving the service life of the resulting product.

[0038] Antioxidants that can be used in rubber compounds include polymerized quinoline derivatives and 1,2-dihydro-2,2,4-trimethylquinoline. Other antioxidants that can be used include alkylated imidazole condensates with diarylamines or ketones and mercaptobenzimidazole condensates with diphenylamine / acetone. These are strong, colorless antioxidants for both natural and synthetic rubbers, and they offer excellent heat and flex resistance, even at high temperatures.

[0039] Plasticizers are added to elastomer compounds for various purposes, such as improving softness and flexibility, lowering the glass transition temperature, inhibiting crystallization, improving dispersibility, reducing compound costs, etc. Plasticizers commonly used in elastomer compounds include mineral oil and esters such as phthalates, sebacates, and adipates.

[0040] Dialkyl esters and dioctyl adipate (DOA) are highly efficient plasticizers that impart excellent low-temperature flexibility and impact resistance. In addition to excellent low-temperature properties, they also possess chemical stability and colorfastness, remaining stable even under prolonged temperature and UV exposure. The combination of low viscosity and high efficiency results in excellent dry blending and processing properties.

[0041] Microcrystalline waxes can be added as physical antiozonants. Because polymer chains containing double bonds are susceptible to ozonolysis and chain scission in the presence of ozone, microcrystalline waxes form a shielding layer or barrier over the compound, protecting it from degradation due to chain scission.

[0042] Modified resorcinol is a resorcinol-formaldehyde homopolymer resin modified with selected groups and can be used as a pre-condensed drying adhesive. Chemically, it is a resorcinol-formaldehyde homopolymer resin modified with selected groups. The modified resorcinol promotes adhesion of the mixed composition.

[0043] Metal acrylates, such as zinc dimethacrylate, can be used to improve the physical and mechanical properties of the compound, functioning as coagents. In the presence of organic peroxides, the metal coagents form ionic bonds, improving the compound's tear strength, modulus, and flex resistance.

[0044] Modified polybutadiene (containing maleic anhydride) can be used as an adhesion promoter for peroxide-cured vulcanizates. Chemically, it is a low-molecular-weight, low-vinyl-content butadiene with maleic anhydride functionality. This anhydride functionality reacts with epoxy, amine, and hydroxyl groups, enabling the development of unique adhesives, sealants, encapsulants, and coatings. It also improves compatibility with non-polar elastomers such as EPDM and enhances adhesion of peroxide-cured elastomers to polyester, aramid, or metal substrates.

[0045] Substituted phenol derivatives such as 2,6-di-tert-butyl-N,N-dimethylamino-p-cresol can be used as scorch inhibitors in peroxide-cured systems. They initially form adducts that trap radicals from the peroxide, affecting the processability and flow time of the compound.

[0046] The elastomer (ethylene polymer) and other ingredients can be mixed using conventional rubber mixing methods. In some embodiments, all ingredients are typically mixed using an industrial mixer such as a Banbury mixer, although other mixing techniques and methods can be used. For example, a roll mill or internal mixer can be used. In some embodiments, the individual ingredients are added to the mixer in a specific order to ensure adequate mixing and dispersion of the ingredients. In some embodiments, certain ingredients can be mixed with each other before being added sequentially to the mixture.

[0047] Table 1 shows examples of component ranges for blend compositions according to the present disclosure. [Table 1]

[0048] For the above ingredients, the specific gravity of the medium reinforcing carbon black is 1.8, the DBP absorption is 30-48 CC / 100 g, the iodine absorption is 6-12 mg / g, the maximum heat loss is 1%, the 325 mesh sieve residue is 0.1%, the ash content is less than 0.5%, and the pellet hardness is 30 g.

[0049] Precipitated silica has a specific gravity of 2.0 and is a white, odorless, fine powder. The BET specific surface area of ​​silica is 130-200 m2 / g. The loss on drying (105°C, 2 hours) is 3-7%. The loss on ignition (anhydrous basis, 1000°C, 2 hours) is a maximum of 6%. The pH of a 5% water slurry is 6-8, the SiO2 moisture content is at least 87%, and the DBP absorption is 200-280 mL per 100 g.

[0050] The specific gravity of the treated silica is 1.9-2.0. The trialkoxysilane content is 5-8%. The volatile content of this treated silica is 3-5%, the pH value is 6-8, and it is a white powder. The specific surface area of ​​this silica grade is 120-150 m2 / g.

[0051] Zinc oxide is an odorless, white, fine powder with a specific gravity of 5.6 and a surface area of ​​4-6 m2 / g. Its heat loss at 110°C is a maximum of 0.5%. Its ash content is 99%, its wet sieve residue (#325 mesh residue) is less than 0.05%, and its #200 mesh residue is less than 0.02%. Its CuO content is less than 0.0005%, MnO content is less than 0.0005%, SiO2 content is less than 0.02%, and water-soluble salt content is less than 0.05%.

[0052] The compositions from Table 1 or any of the above can be used to form belts, such as synchronous belts for automobiles.

[0053] <Example>

[0054] Objects and advantages of the present disclosure are further illustrated by the following non-limiting examples, in which the particular materials and amounts thereof, as well as other conditions and details, recited should not be construed to unduly limit the present disclosure. Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and elsewhere in this disclosure are by weight.

[0055] Example 1

[0056] The materials set forth in Table 2, in the amounts set forth, were used to prepare compositions according to the present disclosure. [Table 2]

[0057] The raw materials were mixed in three stages. In the first stage, all ingredients except the hardener were added to the mixer at 10-20 revolutions per minute. The total mixing time was 8-12 minutes, and the discharge temperature was 150°C. In the second stage, the compound was heated again to 150°C to improve dispersion and homogeneity. The peroxide hardener was added in the third stage, the speed was kept at 8-10 revolutions per minute, and the batch was discharged at 95°C.

[0058] The mixed raw materials were cured at 180°C for 20 minutes using a hydraulic press.

[0059] From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the scope of the invention. Accordingly, the invention is limited only by the appended claims.

[0060] Although the present technology has been described in terms specific to particular structures and materials, it should be understood that the invention defined in the appended claims is not necessarily limited to the particular structures and materials described. Rather, specific aspects are described as forms of implementing the claimed invention. Because many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention is encompassed by the claims hereinafter appended.

[0061] Unless otherwise noted, all numerical values ​​or expressions (such as those expressing dimensions, physical properties, etc.) used in this specification (excluding the claims) are understood to be modified in all instances by the term "about" or "approximately." Without intending to limit the application of the doctrine of equivalents to the claims, at a minimum, each numerical parameter described in the specification or claims modified by the term "about" or "approximately" should be construed in light of the number of significant digits recited and by applying rounding techniques. Furthermore, all ranges disclosed herein should be understood to encompass and provide support for claims reciting any subranges or individual values ​​subsumed therein. For example, a range of 1 to 10 should be interpreted to encompass and provide support for claims reciting any subranges or individual values ​​between and / or including the minimum value of 1 and the maximum value of 10. That is, all subranges starting with a minimum value greater than or equal to 1 and ending with a maximum value less than or equal to 10 (e.g., 5.5 to 10, 2.34 to 3.56, etc.), or ending with any value between 1 and 10 (e.g., 3, 5.8, 9.9994, etc.) are included.

Claims

1. A synchronous belt formed from an uncured composition comprising a halogenated polyethylene polymer and a non-halogenated ethylene polymer, wherein the halogenated polyethylene polymer and the ethylene polymer are present as 25 to 75 weight percent of the uncured composition.

2. 10. A belt formed from the uncured composition of claim 1, wherein the halogenated polyethylene polymer is present in an amount of 25 to 50% by weight of the uncured composition and the ethylene polymer is present in an amount of 10 to 30% by weight of the uncured composition.

3. 10. A belt formed from the uncured composition of claim 1, wherein the halogenated polyethylene polymer is 30 to 40 weight percent of the uncured composition.

4. 10. A belt formed from the uncured composition of claim 1, wherein the halogenated polyethylene polymer is chlorinated.

5. 10. A belt formed from the uncured composition of claim 1, wherein the uncured composition further comprises an organic peroxide.

6. 10. A belt formed from the uncured composition of claim 1, wherein the ethylene polymer is an ethylene acrylic elastomer.

7. 10. A belt formed from the uncured composition of claim 1, wherein the uncured composition further comprises a carbon reinforcing filler and silica.

8. 8. A belt formed from the uncured composition of claim 7 wherein the silica is present at a higher level than the carbon reinforcing filler.

9. 9. A belt formed from the uncured composition of claim 8, wherein the silica is present at a level of about 10-35% by weight of the uncured composition and the carbon reinforcing filler is present at a level of about 3-8% by weight.

10. 9. A belt formed from the uncured composition of claim 8 wherein the silica is present in a ratio of about 4:1 to the carbon reinforcing filler.

11. 2. A belt formed from the uncured composition of claim 1, having a tensile strength of 18 MPa or greater.

12. 10. A belt formed from the uncured composition of claim 1, which is sufficiently flexible at -35°C.

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