Crosslinked thermoplastic elastomers

Abstract

A cross-linkable thermoplastic polymer blend including a thermoplastic elastomer including a vinyl aromatic monomeric units and conjugated diene monomeric units; a nitrile butadiene rubber and a vulcanization package. The thermoplastic elastomer is derived at least in part from conjugated diene monomers. The vulcanization package comprises a silane crosslinker and an organic peroxide. The cross-linkable thermoplastic polymer blend forms a crosslinked thermoplastic elastomer when extruded or injection molded without the requiring a catalyst.

Description

CROSSLINKED THERMOPLASTIC ELASTOMERS CLAIM OF PRIORITY

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 595,328 bearing Attorney Docket Number 1202319 and filed on November 1, 2023, which is hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0002] Embodiments of the present disclosure are generally related to peroxide-vulcanizable compositions and partially crosslinked polymer systems formed therefrom. BACKGROUND

[0003] Crosslinked thermoplastic articles may have desirable properties, such as chemical and heat resistance. Conventional processes, such as reaction extrusion, are known for forming crosslinked thermoplastic articles. In reaction extrusion, a thermoplastic polymer is crosslinked by silane grafting in an extruder, and the crosslinked thermoplastic polymer is further formed into articles by conversion processes such as extrusion and / or injection molding. Additional steps, time, and materials may be required to achieve the desirable crosslink density and heat resistance for certain applications in the healthcare, automotive, and electronic fields.

[0004] However, although curing conjugated diene rubbers with peroxide is generally practiced in the rubber industry, such processes are batch processes and very different from the reaction extrusion processes in an extruder or injection mold of the plastics industry. The high reactivity of conjugated diene rubbers with peroxide makes the process difficult to control, and can “gum up” the extruder or cause other complications in the process.

[0005] Accordingly, there is a need for alternative methods for forming thermoplastic articles, such as effectively curing conjugated diene elastomers using an extrusion process, with improved crosslink density and heat resistance.SUMMARY

[0006] In light of the disclosure herein, and without limiting the scope of the invention in any way, in a first aspect of the present disclosure, which may be combined with any other aspect listed herein unless specified otherwise, a peroxide-vulcanizable composition comprises a thermoplastic elastomer that includes mer units derived from a conjugated diene monomer, a nitrile butadiene rubber, and a vulcanization package. The thermoplastic elastomer is derived at least in part from conjugated diene monomers. The vulcanization package comprises a silane crosslinker and an organic peroxide. The peroxide-vulcanizable composition forms a crosslinked polymer system when extruded or injection molded without the requiring a catalyst (e.g., a moisture cure catalyst).

[0007] In a second aspect of the present disclosure, which may be combined with any other aspect listed herein unless specified otherwise, a crosslinked polymer system comprises a silane-grafted nitrile butadiene rubber and a silane-grafted thermoplastic elastomer comprising a styrene-diene copolymer. The silane-grafted nitrile butadiene rubber and the silane-grafted thermoplastic elastomer are crosslinked via carbon-carbon bond crosslinks.

[0008] In a third aspect, a crosslinked polymer system comprises the crosslinked polymer system of any other aspect listed herein unless specified otherwise, wherein the thermoplastic elastomer has a number average molecular weight of from about 30,000 g / mol to about 400,000 g / mol.

[0009] In a fourth aspect, a crosslinked polymer system comprises the crosslinked polymer system of any other aspect listed herein unless specified otherwise, wherein the thermoplastic elastomer is a triblock copolymer that includes two polystyrene end blocks, and wherein the styrene content of the two polystyrene end blocks in the thermoplastic elastomer is from about 10 wt.% to about 50 wt.%.

[0010] In a fifth aspect, a crosslinked polymer system comprises the crosslinked polymer system of any other aspect listed herein unless specified otherwise, wherein the styrene-diene copolymer comprises styrene-butadiene-styrene (SBS) or styrene / isoprene block copolymer (SIS).

[0011] In a sixth aspect, a crosslinked polymer system comprises the crosslinked polymer system of any other aspect listed herein unless specified otherwise, wherein the styrene-diene copolymer is non-hydrogenated.

[0012] In a seventh aspect, a crosslinked polymer system comprises the crosslinked polymer system of any other aspect listed herein unless specified otherwise, wherein the crosslinked polymer system includes silane crosslinks.

[0013] In an eighth aspect, a crosslinked polymer system comprises the crosslinked polymer system of any other aspect listed herein unless specified otherwise, wherein the crosslinked polymer system is a thermoplastic vulcanizate.

[0014] In a ninth aspect, a crosslinked polymer system comprises the crosslinked polymer system of any other aspect listed herein unless specified otherwise, further comprising an olefin polymer.

[0015] In a tenth aspect, a peroxide-vulcanizable composition comprises a thermoplastic elastomer comprising vinyl aromatic monomeric units and conjugated diene monomeric units, a nitrile butadiene rubber, and a vulcanization package comprising an organic peroxide and a silane.

[0016] In an eleventh aspect, which is combinable with any other aspect listed herein unless specified otherwise, the peroxide-vulcanizable composition comprises from about 25 wt.% to about 95 wt.% of the thermoplastic elastomer, or from about 30 wt.% to about 85 wt.% of the thermoplastic elastomer, or from about 35 wt.% to about 75 wt.% of the thermoplastic elastomer.

[0017] In a twelfth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the peroxide vulcanizable composition comprises from about 15 wt.% to about 50 wt.% of the nitrile butadiene rubber.

[0018] In a thirteenth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the thermoplastic elastomer is selected from the group consisting of styrene- butadiene rubber, styrene-butadiene block copolymers, styrene-isoprene block copolymers, styrene-butadiene-isoprene rubber, styrene-butadiene / isoprene block copolymers, styrene- butadiene-isoprene block copolymers, and combinations thereof.

[0019] In a fourteenth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the thermoplastic elastomer is a triblock copolymer that includes two polystyrene end blocks, and wherein the styrene content of the two polystyrene end blocks in the thermoplastic elastomer is from about 10 wt.% to about 50 wt.%.

[0020] In a fifteenth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the peroxide-vulcanizable composition comprises from about 0.5 wt.% to about 5 wt.% of the silane.

[0021] In a sixteenth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the silane comprises vinyl trimethoxysilane, vinyl triethoxysilane, or a combination thereof.

[0022] In a seventeenth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the peroxide-vulcanizable composition comprises from about 0.05 wt.% to about 1 wt.% of the organic peroxide.

[0023] In an eighteenth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the organic peroxide comprises peroxyketal peroxide, di-tert alkyl peroxide, or a combination thereof.

[0024] In a nineteenth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the di-tert alkyl peroxide comprises dicumyl peroxide.

[0025] In a twentieth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the composition further comprises an olefin polymer. In some aspects, the olefin polymer is a polypropylene.

[0026] In a twenty-first aspect, which is combinable with any other aspect listed herein unless specified otherwise, the composition further comprises an oil.

[0027] In a twenty-second aspect, a process for making the crosslinked polymer system of any other aspect listed herein, comprising the steps of: preparing a carbon-carbon crosslinked, silane-grafted blend by blending a thermoplastic elastomer comprising a styrene-diene copolymer, a nitrile butadiene rubber, an organic peroxide, and a silane such that the thermoplastic elastomer and the nitrile butadiene rubber include carbon-carbon bond crosslinks and grafted silane moieties; and extruding the carbon-carbon crosslinked, silane-grafted blend.

[0028] In a twenty-third aspect, which is combinable with any other aspect listed herein unless specified otherwise, the step of blending the thermoplastic elastomer, the organic peroxide, and the silane is performed in the absence of a catalyst.

[0029] In a twenty-fourth aspect, which is combinable with any other aspect listed herein unless specified otherwise, the step of blending the thermoplastic elastomer, the organic peroxide, and the silane is performed in the absence of moisture. DETAILED DESCRIPTION

[0030] Disclosed herein are crosslinked polymer systems, and more specifically, partially crosslinked polymer systems comprising a vulcanized, silane-grafted thermoplastic elastomer with carbon-carbon bond crosslinks. The vulcanized, silane-grafted thermoplastic elastomer in various aspects comprises a thermoplastic elastomer that includes mer units derived from a conjugated diene monomer and a nitrile butadiene rubber.While the present disclosure describes certain aspects of the cross-linkable thermoplastic blends in detail, the present disclosure is to be considered exemplary and is not intended to be limited to the disclosed aspects.

[0031] The terminology as set forth herein is for description of the aspects only and should not be construed as limiting the disclosure as a whole. All references to singular characteristics or limitations of the present disclosure shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made. Unless otherwise specified, “a,” “an,” “the,” and “at least one” are used interchangeably. Furthermore, as used in the description and the appended claims, the singular forms “a,” “an,” and “the” are inclusive of their plural forms, unless the context clearly indicates otherwise.

[0032] To the extent that the term “includes” or “including” is used in the description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use.

[0033] The cross-linkable thermoplastic polymer blends of the present disclosure can comprise, consist of, or consist essentially of the essential elements of the disclosure as described herein, as well as any additional or optional element described herein, or which is otherwise useful in crosslinked thermoplastic elastomer applications.

[0034] All percentages, parts, and ratios as used herein are by weight of the total blend on an “dry” basis, i.e., without solvents, unless otherwise specified.

[0035] All ranges and parameters, including but not limited to percentages, parts, and ratios, disclosed herein are understood to encompass any and all sub-ranges assumed and subsumed therein, and every number between the endpoints. For example, a stated range of “1 to 10” should be considered to include any and all sub-ranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 1 to 6.1, or 2.3 to 9.4), and to each integer (1, 2, 3, 4, 5, 6, 7, 8, 9, and 10) contained within the range. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0036] The term “wt.%,” as described herein, refers to the weight fraction of the individual component based on a total weight of the peroxide-vulcanizable composition, unless otherwise noted.

[0037] The term “number average molecular weight,” as described herein, refers to a total weight of polymer divided by the total number of molecules as measured using gel permeation chromatography (GPC) and polystyrene standards.

[0038] The term “melt flow rate,” as described herein, refers to the ability of a material’s melt to flow under pressure as measured according to ASTM D1238 at the given temperature and given weight.

[0039] The term “density,” as described herein, refers to the mass per unit volume of a material as measured according to ASTM D792 at 23 °C.

[0040] The term “specific gravity,” as described herein, refers to the ratio of the density of a material to the density of water as measured according to ASTM D792 at 23 °C.

[0041] The term “Mooney viscosity,” as described herein, refers to the viscosity reached after a rotor rotates for a given time interval at the specified temperature as measured according to ASTM D1646.

[0042] The term “yield,” as described herein, refers to the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior.

[0043] The term “tensile strength at yield,” as described herein, refers to the maximum stress that a material can withstand while being stretched before it begins to change shape permanently as measured according to ASTM D638 at 23 °C and a rate of strain of 0.85 mm / s.

[0044] The term “tensile elongation at yield,” as described herein, refers to the ratio between the increased length and initial length at the yield point as measured according to ASTM D638 at 23 °C and a rate of strain of 0.85 mm / s.

[0045] The term “tensile strength at break,” as described herein, refers to the maximum stress that a material can withstand while stretching before breaking as measured according to ASTM D638 at 23 °C and a rate of strain of 0.85 mm / s.

[0046] The term “tensile elongation at break,” as described herein, refers to the ratio between increased length and initial length after breakage as measured according to ASTM D638 at 23 °C and a rate of strain at 0.85 mm / s.

[0047] The term “Shore A hardness,” as described herein, refers to the hardness of a material as measured according to ASTM D2240.

[0048] The term “compression set,” as described herein, refers to the ability of a material to return to its original thickness after prolonged compressive stress as measured according to ASTM D395 at the temperature indicated.

[0049] The term “polyolefin,” as described herein, refers to a polymer that has a crystalline and amorphous phase prepared from olefin monomers.

[0050] The term “polyolefin elastomer (POE),” as described herein, refers to a low crystalline (i.e., less than or equal to 25% crystalline) polymer prepared from olefin monomers.

[0051] The term “silane grafted,” as described herein, refers to the thermoplastic elastomer having a silane side chain connected to the polymer main chain.

[0052] The term “copolymer,” as described herein, refers to a polymer formed when two or more different monomers are polymerized to form a chain.

[0053] The term “block,” as described herein, refers to a portion of a polymer, comprising many constitutional units, that has at least one feature which is not present in the adjacent portions.

[0054] As discussed above, crosslinked thermoplastic articles may have desirable properties, including chemical and heat resistance. However, conventional manufacturing processes may require additional steps, time, and materials to achieve the crosslink density and heat resistance required by certain applications, including, for example, healthcare, automotive, and electronic applications. Additionally, conventional process for curing conjugated diene rubbers with peroxide are limited to batch processes, as the conjugated diene is very reactive to peroxide and it is difficultto control the crosslink reaction in an extruder, and such reactions may “gum up” the extruder or cause other complications in the process.

[0055] The present concepts are directed to a peroxide-vulcanizable composition comprising a a thermoplastic elastomer that includes mer units derived from a conjugated diene monomer, a nitrile butadiene rubber, and a vulcanization package. The thermoplastic elastomer is derived at least in part from conjugated diene monomers. . For the purpose of this specification, the thermoplastic elastomer that includes mer units derived from a conjugated diene monomer may be referred to as simply the “thermoplastic elastomer.” The vulcanization package comprises a silane crosslinker and an organic peroxide. The peroxide-vulcanizable composition can be extruded or injection molded, and optionally can further be moisture cured to form a crosslinked polymeric article without the use of a catalyst.

[0056] Disclosed herein are peroxide-vulcanizable compositions having an advantageous crosslink density (e.g., a reduced tensile elongation at break) and heat resistance (e.g., a reduced compression set) as compared to non-crosslinked thermoplastic elastomers based on conjugated dienes (i.e., without a silane and peroxide vulcanization package). The vulcanization package including an organic peroxide and a silane can enable carbon-carbon bond crosslinking of the thermoplastic elastomer and nitrile-butadiene rubber upon blending without the need for additional steps or materials, such as a moisture cure catalyst.

[0057] Conventional processes for forming crosslinked polymeric articles include a silane grafting step in which a thermoplastic polymer is crosslinked by a silane crosslinker via reaction extrusion, followed by a conversion step in which the crosslinked polymers are formed into articles by extrusion or injection molding. The silane grafting step adds costs in terms of special equipment and operation for reaction extrusion, different reaction extrusion setups required for thermoplastic polymers having different properties, and the packaging and storage of the crosslinked thermoplastic polymer, which has a certain shelf life until it becomes unsuitable for further extrusion or injection molding. The peroxide-vulcanizable composition of the present disclosure addresses these issues in the conventional processes by eliminating the need for a separate silane grafting step. The thermoplastic elastomer and nitrile-butadiene rubber of the present disclosure can be blended with a silane crosslinking composition directly in the conventional conversionprocess, thus eliminating the initial silane grafting step. The crosslinking of the thermoplastic elastomer and the nitrile-butadiene rubber is performed in a one-step process where a crosslinked polymeric article is formed by extrusion or injection molding. As such, the costs and process concerns related to the silane grafting step can be eliminated. In addition, different types of rubbers and polymers can be flexibly included in the peroxide-vulcanizable composition without restriction from the reaction extrusion process. As result, the peroxide-vulcanizable compositions of the present disclosure significantly reduce manufacturing cost and improve formulation flexibility of crosslinked thermoplastic polymers. Polymer Composition

[0058] The peroxide-vulcanizable compositions disclosed herein may generally be described as a thermoplastic elastomer, a nitrile-butadiene rubber, and a vulcanization package including an organic peroxide and a silane. In various aspects, the polymer compostion comprises the thermoplastic elastomer and the conjugated diene rubber. Thermoplastic Elastomer

[0059] The thermoplastic elastomer is an elastomer that includes mer units derived from a conjugated diene monomer. In any of the exemplary aspects, the thermoplastic elastomer of the peroxide-vulcanizable composition may comprise vinyl aromatic monomeric units and conjugated diene monomeric units. The conjugated diene monomeric units can be selected from the group consisting of 1,3-butadiene monomeric units, 2,3-dimethyl-1,3-butadiene, piperylene monomeric units, isoprene monomeric units, and combinations thereof. The vinyl aromatic monomeric units can be selected from the group consisting of styrene monomeric units, α-methyl styrene monomeric units, p-methylstyrene monomeric units, o-methylstyrene monomeric units, p- butylstyrene monomeric units, p-tertbutylstyrene monomeric units, and combinations thereof.

[0060] In any of the exemplary aspects, the thermoplastic elastomer may be selected from the group consisting of styrene-butadiene rubber, styrene-butadiene block copolymers, styrene- isoprene block copolymers, styrene-butadiene-isoprene block copolymers, non-hydrogenated styrene-butadiene rubber, non-hydrogenated styrene-butadiene block copolymers, non- hydrogenated styrene-isoprene block copolymers, non-hydrogenated styrene-butadiene-isoprenerubber, non-hydrogenated styrene-butadiene / isoprene block copolymers, non-hydrogenated styrene-butadiene-isoprene block copolymers, and combinations thereof.

[0061] According to any of the exemplary aspects, the thermoplastic elastomer may be a block copolymer that includes a block defined by formula (I): (I) wherein the w, x, y,is independently a hydrogen atom or a methyl group, and each R2 is independently a hydrogen atom or a methyl group with the proviso that at least one R2 per unit is a hydrogen atom.

[0062] In thermoplastic elastomer defined by formula (I), the molar percent of the sum of the y and z units out of the total sum of the w, x, y, and z units in the block may be from about 30% to about 90%. The molar percent of the sum of the y and z units out of the total sum of the w, x, y, and z units in the block may be from about 50% to about 70%. The molar percent of the sum of the y and z units out of the total sum of the w, x, y, and z units in the block may be greater than or equal to about 30%, greater than or equal to about 35%, greater than or equal to about 40%, greater than or equal to about 45%, or even greater than or equal to about 50%. The molar percent of the sum of the y and z units out of the total sum of the w, x, y, and z units in the block may be less than or equal to about 90%, less than or equal to about 85%, less than or equal to about 80%, less than or equal to about 75%, or even less than or equal to about 70%. The molar percent of the sum of the y and z units out of the total sum of the w, x, y, and z units in the block may be from about 30% to about 90%, from about 30% to about 85%, from about 30% to about 80%, from about 30% to about 75%, from about 30% to about 70%, from about 35% to about 90%, from about 35% to about 85%, from about 35% to about 80%, from about 35% to about 75%, from about 35% to about 70%, from about 40% to about 90%, from about 40% to about 85%, from about 40% to about 80%, from about 40% to about 75%, from about 40% to about 70%, fromabout 45% to about 90%, from about 45% to about 85%, from about 45% to about 80%, from about 45% to about 75%, from about 45% to about 70%, from about 50% to about 90%, from about 50% to about 85%, from about 50% to about 80%, from about 50% to about 75%, or from about 50% to about 70%, or any and all endpoints or subranges therebetween.

[0063] In thermoplastic elastomer defined by formula (I), the ratio of y units to w units may be greater than the ratio of x units to z units. The ratio of y units to w units may also be less than the ratio of x units to z units.

[0064] In any or all of the aspects described herein, the thermoplastic elastomer may be a block copolymer that includes a block defined by formula (II):wherein the a, b, c, are

[0065] In a thermoplastic elastomer defined by formula (II), the molar percent of the sum of the c units and d units out of the total sum of the a, b, c, and d units in the block may be from about 30% to about 90%. The molar percent of the sum of the c units and d units out of the total sum of the a, b, c, and d units in the block may be from about 50% to about 70%. The molar percent of the sum of the c units and d units out of the total sum of the a, b, c, and d units in the block may be greater than or equal to about 30%, greater than or equal to about 35%, greater than or equal to about 40%, greater than or equal to about 45%, or even greater than or equal to about 50%. The molar percent of the sum of the c units and d units out of the total sum of the a, b, c, and d units in the block may be less than or equal to about 90%, less than or equal to about 85%, less than or equal to about 80%, less than or equal to about 75%, or even less than or equal to about 70%. The molar percent of the sum of the c units and d units out of the total sum of the a, b, c, and d units in the block may be from about 30% to about 90%, from about 30% to about 85%, from about 30%to about 80%, from about 30% to about 75%, from about 30% to about 70%, from about 35% to about 90%, from about 35% to about 85%, from about 35% to about 80%, from about 35% to about 75%, from about 35% to about 70%, from about 40% to about 90%, from about 40% to about 85%, from about 40% to about 80%, from about 40% to about 75%, from about 40% to about 70%, from about 45% to about 90%, from about 45% to about 85%, from about 45% to about 80%, from about 45% to about 75%, from about 45% to about 70%, from about 50% to about 90%, from about 50% to about 85%, from about 50% to about 80%, from about 50% to about 75%, or from about 50% to about 70%, or any and all endpoints and subranges therebetween.

[0066] In thermoplastic elastomer defined by formula (II), the ratio of c units to a units may be greater than the ratio of d units to b units. The ratio of c units to a units may also be less than the ratio of d units to b units.

[0067] In accordance with various aspects, the thermoplastic elastomer can be a triblock copolymer that includes two polystyrene end blocks. The styrene content of the two polystyrene end blocks in the thermoplastic elastomer may be from about 10 wt.% to about 50 wt.%. The styrene content of the two polystyrene end blocks in the thermoplastic elastomer may be greater than or equal to about 10 wt.%, greater than or equal to about 15 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 25 wt.%, or even greater than or equal to about 27 wt.%. The styrene content of the two polystyrene end blocks in the thermoplastic elastomer may be less than or equal to about 50 wt.%, less than or equal to about 45 wt.%, less than or equal to about 40 wt.%, less than or equal to about 35 wt.%, or even less than or equal to about 33 wt.%. The styrene content of the two polystyrene end blocks in the thermoplastic elastomer may be from about 10 wt.% to about 50 wt.%, from about 10 wt.% to about 45 wt.%, from about 10 wt.% to about 40 wt.%, from about 10 wt.% to about 35 wt.%, from about 10 wt.% to about 33 wt.%, from about 15 wt.% to about 50 wt.%, from about 15 wt.% to about 45 wt.%, from about 15 wt.% to about 40 wt.%, from about 15 wt.% to about 35 wt.%, from about 15 wt.% to about 33 wt.%, from about 20 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%, from about 20 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 20 wt.% to about 33 wt.%, from about 25 wt.% to about 50 wt.%, from about 25 wt.% to about 45 wt.%, from about 25 wt.% to about 40 wt.%, from about 25 wt.% to about 35 wt.%, from about 25 wt.% to about 33 wt.%, from about 27 wt.% to about 50 wt.%, from about 27 wt.% to about 45 wt.%, from about 27 wt.% toabout 40 wt.%, from about 27 wt.% to about 35 wt.%, or from about 27 wt.% to about 33 wt.%, or any and all endpoints and subranges therebetween.

[0068] In any or all of the aspects described herein, the thermoplastic elastomer may have a number average molecular weight of from about 30,000 g / mol to about 400,000 g / mol. For example, the thermoplastic elastomer may have a number average molecular weight of greater than or equal to 30,000 g / mol, greater than or equal to about 50,000 g / mol, greater than or equal to about 100,000 g / mol, or even greater than or equal to about 150,000 g / mol. The thermoplastic elastomer may additionally or alternatively have a number average molecular weight less than or equal to about 400,000 g / mol, less than or equal to about 350,000 g / mol, less than or equal to about 300,000 g / mol, or even less than or equal to about 250,000 g / mol. According to one or more aspects described herein, the thermoplastic elastomer may have a number average molecular weight of from about 30,000 g / mol to about 400,000 g / mol, from about 30,000 g / mol to about 350,000 g / mol, from about 30,000 g / mol to about 300,000 g / mol, from about 30,000 g / mol to about 250,000 g / mol, from about 50,000 g / mol to about 400,000 g / mol, from about 50,000 g / mol to about 350,000 g / mol, from about 50,000 g / mol to about 300,000 g / mol, from about 50,000 g / mol to about 250,000 g / mol, from about 100,000 g / mol to about 400,000 g / mol, from about 100,000 g / mol to about 350,000 g / mol, from about 100,000 g / mol to about 300,000 g / mol, from about 100,000 g / mol to about 250,000 g / mol, from about 150,000 g / mol to about 400,000 g / mol, from about 150,000 g / mol to about 350,000 g / mol, from about 150,000 g / mol to about 300,000 g / mol, or even from about 150,000 g / mol to about 250,000 g / mol, or any and all endpoints and subranges therebetween.

[0069] In accordance with the present disclosure, when the thermoplastic elastomer has carbon-carbon double bond sites, the carbon-carbon double bond is non-hydrogenated or partially hydrogenated. Without being bound by theory, it is believed that crosslinking of thermoplastic elastomers occurs at least in part at the non-hydrogenated sites (i.e., carbon-carbon double bonds). By controlling the level of hydrogenation, the amount of crosslinking may also be controlled. It is further believed that the lack of hydrogenation of the thermoplastic elastomer can improve the crosslink density and heat resistance of the resulting crosslinked polymer system. Thus, in any of the aspects disclosed herein, the thermoplastic elastomer may have a degree of hydrogenation ofless than 1%, and preferably 0%, based on the unsaturated groups of the conjugated diene monomeric units in the thermoplastic elastomer.

[0070] In accordance with the various aspects, the thermoplastic elastomer may be a block copolymer having a hard phase and a soft phase, the general configuration being: A―B, A―B―A, or A―B―A′, wherein prior to hydrogenation, each A and A′ blocks is a hard phase comprised of vinyl aromatic monomeric units and each B block is a soft phase comprised of conjugated diene monomeric units. “Hard phase” refers to a portion of the block copolymer having a glass transition temperature from 90 ºC to 165 ºC. “Soft phase” refers to a portion of the block copolymer having a glass transition less than -20 ºC.

[0071] In various aspects, the thermoplastic polymer is included in the peroxide- vulcanizable composition in an amount of from about 25 wt.% to about 95 wt.%, based on a total weight of the peroxide-vulcanizable composition. For example, the peroxide-vulcanizable composition can include the thermoplastic polymer in an amount of from about 25 wt.% to about 95 wt.%, from about 30 wt.% to about 85 wt.%, or from about 35 wt.% to about 75 wt.%, based on a total weight of the peroxide-vulcanizable composition, including any and all endpoints and subranges therebetween. Nitrile Butadiene Rubber

[0072] In various aspects described herein, the peroxide-vulcanizable composition further includes a nitrile-butadiene rubber. The peroxide-vulcanizable composition can include the nitrile- butadiene rubber in an amount of from about 15 wt.% to about 50 wt.%, based on a total weight of the peroxide-vulcanizable composition. For example, the peroxide-vulcanizable composition can include the nitrile-butadiene rubber in an amount of from about 15 wt.% to about 50 wt.%,from about 18 wt.% to about 45 wt.%, or from about 20 wt.% to about 40 wt.%, based on a total weight of the peroxide-vulcanizable composition, including any and all endpoints and subranges therebetween. Vulcanization Package

[0073] The vulcanization package of the peroxide-vulcanizable composition comprises a silane crosslinker and an organic peroxide. As described herein, the vulcanization package facilitates peroxide vulcanization resulting in carbon-carbon bond crosslinking of the thermoplastic elastomer and the nitrile-butadiene rubber upon blending without the need for additional steps or materials. During blending of the peroxide-vulcanizable composition to form the crosslinked polymer system, the thermoplastic elastomer and the nitrile-butadiene rubber may be grafted with silane moieties. The blend may be aged such that the crosslinked polymer system forms silane crosslinks from the silane-grafts.

[0074] The silane crosslinker of the vulcanization package may comprise various silanes. Examples of suitable silanes include the silane represented by the following formula: SiRxH4-x wherein x is 1-4, and each R is individually and independently a monovalent hydrocarbon group or a monovalent alkoxy group.

[0075] In various aspects, the monovalent hydrocarbon group may be a linear, cyclic, or branched group. The monovalent hydrocarbon group may have 1-12 carbon atoms, 2-10 carbon atoms, or 3-8 carbon atoms. The monovalent hydrocarbon group may include one or more carbon- carbon double bonds. The monovalent hydrocarbon group may include one or more aromatic groups.

[0076] In accordance with the present disclosure, the monovalent alkoxy group may be a monovalent hydrocarbon group attached to an oxygen atom. The monovalent hydrocarbon group of the monovalent alkoxy group may be a linear, cyclic, or branched group. The monovalent hydrocarbon group of the monovalent alkoxy group may have 1-12 carbon atoms, 2-10 carbonatoms, or 3-8 carbon atoms. The monovalent hydrocarbon group of the monovalent alkoxy group may include one or more double carbon-carbon bonds. The monovalent hydrocarbon group of the monovalent alkoxy group may include one or more aromatic groups.

[0077] In any of the exemplary aspects, the silane crosslinker may comprise vinyl trialkoxysilane. For example, the silane crosslinker may comprise vinyl trimethoxysilane, vinyl triethoxysilane, or a combination thereof.

[0078] The silane crosslinker may have a specific gravity greater than or equal to about 0.90 or greater than or equal to about 0.95. The silane may have a specific gravity less than or equal to about 1.05 or less than or equal to about 1. The silane may have a specific gravity from about 0.90 to about 1.05, from about 0.90 to about 1.00, from about 0.95 to about 1.05, or from about 0.95 to about 1.00, including any and all endpoints and subranges therebetween.

[0079] In any of the aspects disclosed herein, the silane crosslinker may have a boiling point greater than or equal to about 75 °C or greater than or equal to about 100 °C. The silane crosslinker may have a boiling point less than or equal to about 150 °C or less than or equal to about 125 °C. For example, the silane crosslinker may have a boiling point from about 75 °C to about 150 °C, from about 75 °C to about 125 °C, from about 100 °C to about 150 °C, or from about 100 °C to about 125 °C, including any and all endpoints and subranges therebetween.

[0080] In any of the aspects disclosed herein, the silane crosslinker may have a number average molecular weight greater than or equal to about 50 g / mol, greater than or equal to about 100 g / mol, greater than or equal to 150 g / mol, or greater than or equal to about 200 g / mol. The silane crosslinker may have a number average molecular weight less than or equal to about 500 g / mol, less than or equal to about 400 g / mol, or less than or equal to about 300 g / mol. The silane crosslinker may have a number average molecular weight from about 50 g / mol to about 500 g / mol, from about 50 g / mol to about 400 g / mol, from about 50 g / mol to about 300 g / mol, from about 100 g / mol to about 500 g / mol, from about 100 g / mol to about 400 g / mol, from about 100 g / mol to about 300 g / mol, from about 150 g / mol to about 500 g / mol, from about 150 g / mol to about 400 g / mol, from about 150 g / mol to about 300 g / mol, from about 200 g / mol to about 500 g / mol, fromabout 200 g / mol to about 400 g / mol, or from about 200 g / mol to about 300 g / mol, including any and all endpoints and subranges therebetween.

[0081] Examples of suitable silane crosslinkers that are commercially available include grade A-171 vinyltrimethoxy silane under SILQUESTTMbrand from Momentive.

[0082] As mentioned above, the vulcanization package further includes an organic peroxide. The organic peroxide of the vulcanization package may comprise various peroxides and is not particularly limited. Examples of suitable peroxides include the peroxide represented by the following formula: R-O-O-R wherein each R is individually and independently a monovalent hydrocarbon group. In accordance with the present disclosure, the monovalent hydrocarbon group of the organic peroxide may be a linear, cyclic, or branched group. The monovalent hydrocarbon group of the organic peroxide may have 1-16 carbon atoms, 3-12 carbon atoms, or 5-10 carbon atoms. The monovalent hydrocarbon group of the organic peroxide may include one or more carbon-carbon double bonds. The monovalent hydrocarbon group of the organic peroxide may include one or more aromatic groups. In accordance with the present disclosure, the organic peroxide may comprise peroxyketal peroxide, di-tert alkyl peroxide, or a combination thereof. For example, the organic peroxide may comprise dicumyl peroxide (a di-tert alkyl peroxide).

[0083] In accordance with the present disclosure, the organic peroxide may have a density greater than or equal to about 1.00 g / cm3or greater than or equal to about 1.05 g / cm3. The organic peroxide may have a density less than or equal to about 1.20 g / cm3or less than or equal to about 1.15 g / cm3. The organic peroxide may have a density from about 1.00 g / cm3to about 1.20 g / cm3, from about 1.00 g / cm3to about 1.15 g / cm3, from about 1.05 g / cm3to about 1.20 g / cm3, or from about 1.05 g / cm3to about 1.15 g / cm3, including any and all endpoints and subranges therebetween.

[0084] Examples of suitable organic peroxide that are commercially available include grade BC-FF dicumyl peroxide under the PERKADOX® brand from AkzoNobel.

[0085] In accordance with the present disclosure, the weight ratio based on dry weight of the silane crosslinker and the organic peroxide in the vulcanization package may be 3:1 or more, 4:1 or more, or 5:1 or more. The weight ratio based on dry weight of the silane crosslinker and the organic peroxide in the vulcanization package may be 20:1 or less, 15:1 or less, or 10:1 or less. The weight ratio based on dry weight of the silane crosslinker and the organic peroxide in the vulcanization package may be from 3:1 to 20:1, from 3:1 to 15:1, from 3:1 to 10:1, from 4:1 to 20:1, from 4:1 to 15:1, from 4:1 to 10:1, from 5:1 to 20:1, from 5:1 to 15:1, from 5:1 to 10:1, including any and all endpoints and subranges therebetween. The dry weight of the silane crosslinker and the organic peroxide in the vulcanization package may be from 0.5 to 10% of the mass of the thermoplastic elastomer in the polymer pellet, including from 1% to 8%, from 2 to 7%, and from 3 to 6%.

[0086] In any of the aspects disclosed herein, the vulcanization package may be in the form of a dry silane masterbatch comprising a carrier material loaded with the silane crosslinker and organic peroxide. The carrier material may comprise porous pellets, a filler material (e.g., silica, talc, calcium carbonate, microspheres, etc.), or a combination thereof. The porous pellets may comprise high porosity pellets, such as plastics selected from polypropylene, ethylene vinyl acetate, polyethylene, and mixtures thereof. The carrier material may be loaded by soaking the carrier material in a solution containing the silane crosslinker, the organic peroxide, and other components, if present (e.g., additives), and drying the carrier material to remove solvents in the solution. The silane / peroxide loading of the carrier material may be 20% or more, 30% or more, or 40% or more, based on the dry weight ratio of silane / peroxide to carrier. The silane / peroxide loading of the carrier material may be 80% or less, 70% or less, or 60% or less, based on the dry weight ratio of silane / peroxide to carrier. The silane / peroxide loading of the carrier material may be from 20% to 80%, from 20% to 70%, from 20% to 60%, from 30% to 80%, from 30% to 70%, from 30% to 60%, from 40% to 80%, from 40% to 70%, from 40% to 60%, including any and all endpoints and subranges therebetween, based on the dry weight ratio of silane / peroxide to carrier. The dry silane masterbatch may be dry blended with the polymer pellet and fed to extrusion or injection molding processes for crosslinking the thermoplastic elastomer.

[0087] The vulcanization package may be present in the form of a solution, dispersion, or emulsion comprising the silane crosslinker and the organic peroxide. When forming the dry silane,the vulcanization package may be blended with the porous pellet to form the dry silane masterbatch, which may then be fed to an extrusion or injection molding process for crosslinking the thermoplastic elastomer and the nitrile-butadiene rubber. Alternatively, or in addition to the dry silane, the vulcanization package may be injected directly into the melt polymer pellet during extrusion or injection molding.

[0088] The peroxide-vulcanizable composition may comprise from about 0.5 wt.% to about 5 wt.% of the silane. In any of the exemplary aspects, the amount of silane in the peroxide- vulcanizable composition may be greater than or equal to about 0.5 wt.%, including, for example, at least 0.75 wt.%, at least 0.9 wt.%, at least 1 wt.%, at least 1.25 wt.%, at least 1.5 wt.%, at least 1.75 wt.%, or at least 2 wt.%, including all the endpoints and subranges therebetween. In any of the exemplary aspects, the amount of silane in the peroxide-vulcanizable composition may be less than or equal to about 5 wt.%, including, for example, less than or equal to about 4.75 wt.%, less than or equal to 4.5 wt.%, less than or equal to 4.2 wt.%, less than or equal to 4 wt.%, less than or equal to 3.7 wt.%, less than or equal to 3.5 wt.%, less than or equal to 3.2 wt.%, or less than or equal to about 3 wt. %, including all endpoints and subranges therebetween. The amount of silane in the peroxide-vulcanizable composition may be from 0.5 wt.% to 5 wt.%, including, for example, from 0.5 wt.% to about 4 wt.%, from about 0.5 wt.% to about 3 wt.%, from about 1 wt.% to about 5 wt.%, from about 1 wt.% to about 4 wt.%, or from about 1 wt.% to about 3 wt.%, including any endpoints and subranges therebetween.

[0089] While not wishing to be bound by theory, it is believed that increasing the organic peroxide amount in the peroxide-vulcanizable composition improves the crosslink density and heat resistance of the resulting crosslinked thermoplastic elastomer. In any of the aspects disclosed herein, the peroxide-vulcanizable composition may comprise from about 0.05 wt.% to about 1 wt.% of the organic peroxide. The amount of organic peroxide in the peroxide-vulcanizable composition may be greater than or equal to about 0.05 wt.%, greater than or equal to about 0.1 wt.%, or even greater than or equal to about 0.2 wt.%. The amount of organic peroxide in the peroxide-vulcanizable composition may be less than or equal to about 1 wt.%, less than or equal to about 0.8 wt.%, less than or equal to about 0.6 wt.%, or even less than or equal to about 0.4 wt.%. The amount of organic peroxide in the peroxide-vulcanizable composition may be from about 0.05 wt.% to about 1 wt.%, from about 0.05 wt.% to about 0.8 wt.%, from about 0.05 wt.%to about 0.6 wt.%, from about 0.05 wt.% to about 0.4 wt.%, from about 0.1 wt.% to about 1 wt.%, from about 0.1 wt.% to about 0.8 wt.%, from about 0.1 wt.% to about 0.6 wt.%, from about 0.1 wt.% to about 0.4 wt.%, from about 0.2 wt.% to about 1 wt.%, from about 0.2 wt.% to about 0.8 wt.%, from about 0.2 wt.% to about 0.6 wt.%, or from about 0.2 wt.% to about 0.4 wt.%, including all endpoints and subranges therebetween. Olefin Polymer

[0090] The peroxide-vulcanizable composition may further comprise an olefin polymer to tailor hardness and mechanical properties and improve flow properties. The olefin polymer may comprise polyolefin, polyolefin elastomer, or a combination thereof. For example, suitable examples of polyolefin include polypropylene, polyethylene, or a combination thereof. The polyolefin may be at least one of high-density polyethylene (e.g., greater than or equal to 0.940 g / cm3) or a crystalline polypropylene with a percent crystallinity of at least about 60%.

[0091] In accordance with the present disclosure, the olefin polymer may comprise polypropylene. The polypropylene may comprise a polypropylene homopolymer (i.e., composed of propylene monomers) or a polypropylene copolymer having greater than 50 wt.% propylene monomer and one or more additional comonomer such as C2and C4-C12alpha olefins. The polyethylene may comprise a polyethylene homopolymer (i.e., composed of ethylene monomers) or a polyethylene copolymer having greater than 50 wt.% ethylene monomer and an additional comonomer, such as C3-C12 alpha olefins.

[0092] The polypropylene may have a melt flow rate (230 °C / 2.16 kg) greater than or equal to about 0.1 g / 10 min, greater than or equal to about 0.5 g / 10 min, greater than or equal to about 1 g / 10 min, or even greater than or equal to about 3 g / 10 min. The polypropylene may have a melt flow rate (230 °C / 2.16 kg) less than or equal to about 10 g / 10 min or even less than or equal to about 5 g / 10 min. The polypropylene may have a melt flow rate (230 °C / 2.16 kg) from about 0.1 g / 10 min to about 10 g / 10 min, from about 0.1 g / 10 min to about 5 g / 10 min, from about 0.5 g / 10 min to about 10 g / 10 min, from about 0.5 g / 10 min to about 5 g / 10 min, from about 1 g / 10 min to about 10 g / 10 min, from about 1 g / 10 min to about 5 g / 10 min, from about 3 g / 10 min to about 10g / 10 min, or from about 3 g / 10 min to about 5 g / 10 min, or any and all subranges formed from any of these endpoints.

[0093] In accordance with the present disclosure, the polyolefin may have a density greater than or equal to about 0.80 g / cm3or even greater than or equal to about 0.85 g / cm3. The polyolefin may have a density less than or equal to about 1.10 g / cm3or even less than or equal to about 1.00 g / cm3. The polyolefin may comprise a density from about 0.80 g / cm3to about 1.10 g / cm3, from about 0.80 g / cm3to about 1.00 g / cm3, from about 0.85 g / cm3to about 1.10 g / cm3, or from about 0.85 g / cm3to about 1.00 g / cm3, or any and all subranges formed from any of these endpoints.

[0094] In accordance with the present disclosure, the polyolefin may have a melting point greater than or equal to about 100 °C, greater than or equal to about 110 °C, or even greater than or equal to about 120 °C.

[0095] In accordance with the present disclosure, the polyolefin may have a tensile strength at yield greater than or equal to about 25 MPa or even greater than or equal to about 30 MPa. The polyolefin may have a tensile strength at yield less than or equal to about 45 MPa or even less than or equal to about 40 MPa. The polyolefin may have a tensile strength at yield from about 25 MPa to about 45 MPa, from about 25 MPa, to about 40 MPa, from about 30 MPa to about 45 MPa, or from about 30 MPa to about 40 MPa, including any and all endpoints and subranges therebetween.

[0096] In accordance with the present disclosure, the polyolefin may have a tensile elongation at yield greater than or equal to about 3% or even greater than or equal to about 5%. The polyolefin may have a tensile elongation at yield less than or equal to about 20% or even less than or equal to about 15%. The polyolefin may have a tensile elongation at yield from about 3% to about 20%, from about 3% to about 15%, from about 5% to about 20%, or from about 5% to about 15%, including any and all endpoints and subranges therebetween.

[0097] Examples of suitable polyolefins that are commercially available include polypropylene homopolymer grade 1102KR under the FORMOLENE® brand from Formosa Plastics.

[0098] In accordance with the present disclosure, the polyolefin elastomer may comprise polypropylene elastomer. Examples of suitable polyolefin elastomers that are commercially available include polypropylene elastomer grades 6201 and 6202 under the VISTAMAXX™ brand from Exxon.

[0099] In accordance with the present disclosure, the polyolefin elastomer may comprise olefin block copolymer, ethylene alpha-olefin copolymer, or a combination thereof. The olefin block copolymer may comprise an ethylene alpha-olefin repeating unit. The ethylene alpha-olefin repeating unit is the polymerized reaction product of ethylene and C3-C12 olefins. For example, the ethylene alpha-olefin repeating unit may comprise ethylene-octene copolymer, ethylene- hexene copolymer, ethylene-butene copolymer, or a combination thereof.

[0100] In accordance with the present disclosure, the olefin block copolymer may have a melt flow rate (190 °C / 2.16 kg) greater than or equal to about 1 g / 10 min or even greater than or equal to about 5 g / 10 min. The olefin block copolymer may have a melt flow rate (190 °C / 2.16 kg) less than or equal to about 25 g / 10 min or even less than or equal to about 20 g / 10 min. The olefin block copolymer may have a melt flow rate (190 °C / 2.16 kg) from about 1 g / 10 min to about 25 g / 10 min, from about 1 g / 10 min to about 20 g / 10 min, from about 5 g / 10 min to about 25 g / 10 min, or from about 5 g / 10 min to about 20 g / 10 min, or any and all subranges formed from any of these endpoints.

[0101] In accordance with the present disclosure, the olefin block copolymer may have a density greater than or equal to about 0.80 g / cm3or even greater than or equal to about 0.85 g / cm3. The olefin block copolymer may have a density less than or equal to about 0.95 g / cm3or even less than or equal to about 0.90 g / cm3. The olefin block copolymer may have a density from about 0.80 g / cm3to about 0.95 g / cm3, from about 0.80 g / cm3to about 0.90 g / cm3, from about 0.85 g / cm3to about 0.95 g / cm3, or from about 0.85 g / cm3to about 0.90 g / cm3, including any and all endpoints and subranges therebetween.

[0102] In accordance with the present disclosure, the olefin block copolymer may have a Shore A hardness greater than or equal to about 50 or even greater than or equal to about 60. The olefin block copolymer may have a Shore A hardness less than or equal to about 85 or even lessthan or equal to about 75. The olefin block copolymer may have a Shore A hardness from about 50 to about 85, from about 50 to about 75, from about 60 to about 85, or from about 60 to about 75, including any and all endpoints and subranges therebetween.

[0103] Examples of suitable olefin block copolymers that are commercially available include 9500 and 9817 under the INFUSE™ brand from Dow Chemical Company.

[0104] The ethylene alpha-olefin copolymer is the polymerized reaction product of ethylene and C3-C12olefins. For example, the ethylene alpha-olefin copolymer may comprise ethylene- octene copolymer, ethylene-hexene copolymer, ethylene-butene copolymer, or a combination thereof.

[0105] In accordance with the present disclosure, the ethylene-alpha olefin copolymer may have a melt flow rate (190 °C / 2.16 kg) greater than or equal to 0.1 g / 10 min or even greater than or equal to 0.25 g / 10 min. The ethylene-alpha olefin copolymer may have a melt flow rate (190 °C / 2.16 kg) less than or equal to 3 g / 10 min or even less than or equal to 1 g / 10 min. The ethylene- alpha olefin copolymer may have a melt flow rate (190 °C / 2.16 kg) from 0.1 g / 10 min to 3 g / 10 min, from 0.1 g / 10 min to 1 g / 10 min, from 0.25 g / 10 min to 3 g / 10 min, or even from 0.25 g / 10 min to 1 g / 10 min, including any and all endpoints and subranges therebetween.

[0106] In accordance with the present disclosure, the ethylene-alpha olefin copolymer may have a density greater than or equal to 0.80 g / cm3or even greater than or equal to 0.85 g / cm3. The ethylene-alpha olefin copolymer may have a density less than or equal to 0.95 g / cm3or even less than or equal to 0.90 g / cm3. The ethylene-alpha olefin copolymer may have a density from 0.80 g / cm3to 0.95 g / cm3, from 0.80 g / cm3to 0.90 g / cm3, from 0.85 g / cm3to 0.95 g / cm3, or even from 0.85 g / cm3to 0.90 g / cm3, including any and all endpoints and subranges therebetween.

[0107] In accordance with the present disclosure, the ethylene-alpha olefin copolymer may have a Mooney viscosity (ML 1+4, 121 °C) greater than or equal to 20, greater than or equal to 30, or even greater than or equal to 40. The ethylene-alpha olefin copolymer may have a Mooney viscosity (ML 1+4, 121 °C) less than or equal to 70, less than or equal to 60, or even less than or equal to 50. The ethylene-alpha olefin copolymer may have a Mooney viscosity (ML 1+4, 121 °C) from 20 to 70, from 20 to 60, from 20 to 50, from 30 to 70, from 30 to 60, from 30 to 50, from40 to 70, from 40 to 60, or from 40 to 50, or any and all subranges formed from any of these endpoints.

[0108] In accordance with the present disclosure, the ethylene-alpha olefin copolymer may have a Shore A hardness greater than or equal to 40 or even greater than or equal to 45. The ethylene-alpha olefin copolymer may have a Shore A hardness less than or equal to 60 or even less than or equal to 65. The ethylene-alpha olefin copolymer may have a Shore A hardness from 40 to 60, from 40 to 55, from 45 to 60, or from 45 to 55, or any and all subranges formed from any of these endpoints.

[0109] Examples of suitable ethylene-alpha olefin copolymers that are commercially available include XLT 8677 under the ENGAGE™ brand from Dow Chemical Company.

[0110] In accordance with the present disclosure, the cross-linkable thermoplastic polymer blend may comprise from about 2 wt.% to about 50 wt.% of the olefin polymer, from about 4 wt.% to about 40 wt.% of the olefin polymer, or from about 6 wt.% to about 30 wt.% of the olefin polymer. The amount of the olefin polymer in the cross-linkable thermoplastic polymer blend may be greater than or equal to about 2 wt.%, greater than or equal to about 4 wt.%, or even greater than or equal to about 6 wt.%. The amount of the olefin polymer in the cross-linkable thermoplastic polymer blend may be less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 20 wt.%, less than or equal to about 17 wt.%, less than or equal to about 15 wt.%, less than or equal to about 13 wt.%, or even less than or equal to about 10 wt.%. The amount of olefin polymer in the cross-linkable thermoplastic polymer blend may be from about 2 wt.% to about 50 wt.%, from about 2 wt.% to about 40 wt.%, from about 2 wt.% to about 30 wt.%, from about 2 wt.% to about 20 wt.%, from about 2 wt.% to about 17 wt.%, from about 2 wt.% to about 15 wt.%, from about 2 wt.% to about 13 wt.%, from about 2 wt.% to about 10 wt.%, from about 4 wt.% to about 50 wt.%, from about 4 wt.% to about 40 wt.%, from about 4 wt.% to about 30 wt.%, from about 4 wt.% to about 20 wt.%, from about 4 wt.% to about 17 wt.%, from about 4 wt.% to about 15 wt.%, from about 4 wt.% to about 13 wt.%, from about 4 wt.% to about 10 wt.%, from about 6 wt.% to about 50 wt.%, from about 6 wt.% to about 40 wt.%, from about 6 wt.% to about 30 wt.%, from about 6 wt.% to about 20 wt.%, from about 6 wt.% to about 17 wt.%, from about 6 wt.% to about 15 wt.%, from about 6wt.% to about 13 wt.%, or from about 6 wt.% to about 10 wt.%, or any and all subranges formed from any of these endpoints. Plasticizer

[0111] In accordance with the present disclosure, the peroxide-vulcanizable composition may further comprise a plasticizer. The plasticizer may help to improve flow in the peroxide- vulcanizable composition. In accordance with the present disclosure, the plasticizer may comprise non-polar plasticizer (e.g., mineral oil).

[0112] In accordance with the present disclosure, the amount of plasticizer in the peroxide- vulcanizable composition may be greater than or equal to about 0 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 25 wt.%, greater than or equal to about 30 wt.%, or greater than or equal to about 35 wt.%. The amount of plasticizer in the peroxide-vulcanizable composition may be less than or equal to about 60 wt.%, less than or equal to about 55 wt.%, less than or equal to about 50 wt.%, less than or equal to about 45 wt.%, less than or equal to about 40 wt.%, or less than or equal to about 35 wt.%. The amount of plasticizer in the peroxide-vulcanizable composition may be from about 0 wt.% to about 60 wt.%, including from about 10 wt.% to 55 wt.%, from about 20 wt.% to 50 wt.%, from about 25 wt.% to 45 wt.%, from about 30 wt.% to 40 wt.%, and any and all subranges formed from any of these endpoints.

[0113] Examples of suitable plasticizers that are commercially available include grade PSO 380 under the PURETOL™ brand from Petro-Canada. Tackifier

[0114] In accordance with the present disclosure, the peroxide-vulcanizable composition may further comprise a tackifier for adhesive applications (e.g., hot melt adhesive).

[0115] In accordance with the present disclosure, the tackifier may comprise hydrocarbon resin. Exemplary hydrocarbon resins may include aliphatic resins (e.g., C5 resins), aromatic resins (e.g., C9 resins), dicyclopentadiene resins, and resins including a combination of two or more ofaliphatic monomers, aromatic monomers, and dicyclopentadiene. The hydrocarbon resin may be hydrogenated. In accordance with the present disclosure, the hydrocarbon resin may have a number average molecular weight of less than or equal to about 2,000 g / mol, less than or equal to about 1,500 g / mol, less than or equal to about 1,200 g / mol, less than or equal to about 1,100 g / mol, less than or equal to about 1,000 g / mol, or less than or equal to about 900 g / mol.

[0116] In accordance with the present disclosure, the peroxide-vulcanizable composition may comprise from about 15 wt.% to about 50 wt.% of the tackifier, or from about 17 wt.% to about 40 wt.% of the tackifier, or from about 20 wt.% to about 30 wt.% of the tackifier. The amount of tackifier in the peroxide-vulcanizable composition may be greater than or equal to about 15 wt.%, greater than or equal to about 17 wt.%, or even greater than or equal to about 20 wt.%. The amount of tackifier in the peroxide-vulcanizable composition may be less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 27 wt.%, or even less than or equal to about 25 wt.%. The amount of tackifier in the peroxide-vulcanizable composition may be from about 15 wt.% to about 50 wt.%, from about 15 wt.% to about 40 wt.%, from about 15 wt.% to about 30 wt.%, from about 15 wt.% to about 27 wt.%, from about 15 wt.% to about 25 wt.%, from about 17 wt.% to about 50 wt.%, from about 17 wt.% to about 40 wt.%, from about 17 wt.% to about 30 wt.%, from about 17 wt.% to about 27 wt.%, from about 17 wt.% to about 25 wt.%, from about 20 wt.% to about 50 wt.%, from about 20 wt.% to about 40 wt.%, from about 20 wt.% to about 30 wt.%, from about 20 wt.% to about 27 wt.%, or even from about 20 wt.% to about 25 wt.%, or any and all endpoints and subranges therebetween.

[0117] Examples of suitable tackifiers that are commercially available include grade R1140 under the PLASTOLYN™ brand from Eastman Chemicals. Co-crosslinkable Polymer

[0118] In accordance with the present disclosure, the peroxide-vulcanizable composition may further comprise a co-crosslinkable polymer, which may crosslink with the thermoplastic elastomer and the nitrile-butadiene rubber by the vulcanization package.

[0119] In accordance with the present disclosure, the co-crosslinkable polymer may comprise ethylene-vinyl acetate. The ethylene-vinyl acetate may have a vinyl acetate content greater than or equal to about 10 wt.%, greater than or equal to about 25 wt.%, greater than or equal to about 40 wt.%, or even greater than or equal to 55 wt.%, based on a total weight of the ethylene-vinyl acetate. The ethylene-vinyl acetate may have a vinyl acetate content less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, or even less than or equal to about 60 wt.%. The ethylene-vinyl acetate may have a vinyl acetate content from about 10 wt.% to about 80 wt.%, from about 10 wt.% to about 70 wt.%, from about 10 wt.% to about 60 wt.%, from about 25 wt.% to about 80 wt.%, from about 25 wt.% to about 70 wt.%, from about 25 wt.% to about 60 wt.%, from about 40 wt.% to about 80 wt.%, from about 40 wt.% to about 70 wt.%, from about 40 wt.% to about 60 wt.%, from about 55 wt.% to about 80 wt.%, from about 55 wt.% to about 70 wt.%, or from about 55 wt.% to about 60 wt.%, or any and all endpoints and subranges therebetween.

[0120] In accordance with the present disclosure, the peroxide-vulcanizable composition may comprise from about 25 wt.% to about 45 wt.% of the co-crosslinkable polymer, or from about 27 wt.% to about 43 wt.% of the co-crosslinkable polymer, or from about 30 wt.% to about 40 wt.% of the co-crosslinkable polymer. The amount of the co-crosslinkable polymer in the cross- linkable thermoplastic polymer blend may be greater than or equal to about 25 wt.%, greater than or equal to about 27 wt.%, or even greater than or equal to about 30 wt.%. The amount of the co- crosslinkable polymer in the peroxide-vulcanizable composition may be less than or equal to about 45 wt.%, less than or equal to about 43 wt.%, or even less than or equal to about 40 wt.%. The amount of the co-crosslinkable polymer in the peroxide-vulcanizable composition may be from about 25 wt.% to about 45 wt.%, from about 25 wt.% to about 43 wt.%, from about 25 wt.% to about 40 wt.%, from about 27 wt.% to about 45 wt.%, from about 27 wt.% to about 43 wt.%, from about 27 wt.% to about 40 wt.%, from about 30 wt.% to about 45 wt.%, from about 30 wt.% to about 43 wt.%, or from about 30 wt.% to about 40 wt.%, or any and all endpoints and subranges therebetween.

[0121] Examples of suitable co-vulcanizable polymers that are commercially available include grade 265 under the ELVAX™ brand from Dow Chemical Company.Additives

[0122] In accordance with the present disclosure, the peroxide-vulcanizable composition may further comprise one or more additives. The additive may comprise adhesion promoters; biocides; anti-fogging agents; anti-static agents; blowing and foaming agents; bonding agents and bonding polymers; dispersants; flame retardants and smoke suppressants; mineral fillers; initiators; lubricants; micas; pigments, colorants, and dyes; processing aids; release agents; silanes, titanates, and zirconates; slip and anti-blocking agents; stearates; ultraviolet light absorbers; viscosity regulators; waxes; or combinations thereof. Crosslinking of Thermoplastic Elastomer and Nitrile-Butadiene Rubber

[0123] In accordance with the present disclosure, the peroxide-vulcanizable composition, including the polymer pellet, the vulcanization package, and optional components such as the olefin polymer, plasticizer, or tackifier, can be blended to form a crosslinked polymeric article having an advantageous crosslink density and heat resistance. In some aspects, the crosslinked polymeric article may be a thermoplastic vulcanizate.

[0124] In any of the exemplary aspects, the peroxide-vulcanizable composition may include from 90 to 99.9 parts of the polymer pellet and 0.1 to 10 parts vulcanization package, including, for example 94 to 99.5 parts polymer pellet and 0.5 to 5 parts vulcanization package. In any of the exemplary aspects, the peroxide-vulcanizable composition may comprise the vulcanization package in an amount of 0.1% to 10%, including, for example, 0.2% to 6%, 0.3% to 4%, 0.5% to 3%, and 1.0% to 2%, based on dry weight of the vulcanization package relative to the weight of the thermoplastic elastomer and nitrile-butadiene rubber in the polymer pellet, including all endpoints and subranges therebetween.

[0125] The crosslinked polymeric article can be made by a batch process or a continuous process. Blending (also known as compounding) devices are well known to those skilled in the art and generally include feed means, especially at least one hopper for pulverulent materials and / or at least one injection pump for liquid materials; high-shear blending means, for example a co-rotating or counter-rotating twin-screw extruder, usually comprising a feed screw placed in a heated barrel (or tube); an output head, which gives the extrudate its shape; and means for coolingthe extrudate, either by air cooling or by circulation of water. The extrudate is generally in the form of rods continuously exiting the device and able to be cut or formed into granules. However, other forms may be obtained by fitting a die of desired shape on the output die.

[0126] For example, the peroxide-vulcanizable composition (i.e., the polymer pellet, the vulcanization package, and any additives) may be fed to an extruder (e.g., 27 MM Leistriz Twin Extruder (L / D 52)) and blended. The blending (e.g., in the barrel of the extruder) may be carried out at a temperature from 240 °F to 500 °F (about 115 °C to about 260 °C). In accordance with the present disclosure, the blending results in carbon-carbon bond crosslinking and grafted silane moieties on the thermoplastic elastomer and nitrile-butadiene rubber.

[0127] As described herein, the vulcanization package including both organic peroxide and silane enables the carbon-carbon bond crosslinking of the thermoplastic elastomer and nitrile- butadiene rubber without the need for additional steps or materials (e.g., moisture cure catalyst). Accordingly, in aspects, the step of blending the thermoplastic elastomer and nitrile-butadiene rubber, the organic peroxide, and the silane is performed in the absence of a catalyst. Moreover, the step of blending the thermoplastic elastomer and nitrile-butadiene rubber, the organic peroxide, and the silane may be performed in the absence of moisture (e.g., water). Accordingly, the silane may also be grafted to the thermoplastic elastomer and nitrile-butadiene rubber in the extruder. However, due to the absence of moisture, silane crosslinking does not occur in the extruder or (to the extent that any crosslinking happens at all) occurs only to a very small degree. However, upon exiting the extruder, the thermoplastic elastomer and nitrile-butadiene rubber are free of, or substantially free of, silane-silane crosslinks. The extrudate can be shaped to form a shaped carbon-carbon crosslinked, silane grafted blend. In aspects, the shaped carbon-carbon crosslinked, silane grafted blend is aged (e.g., heat treated or cured) such that the crosslinked polymer system includes silane-silane crosslinks.

[0128] In aspects described herein, upon extruding, the crosslinked polymer system has an extrusion tensile elongation at break greater than or equal to about 30% and a tensile elongation of the crosslinked polymer system remains within 5% of the extrusion tensile elongation at break for 24 hours at room temperature. In any or all of the aspects described herein, upon extruding, the crosslinked polymer system has an extrusion compression set greater than or equal to about 20%and a compression set of the crosslinked polymer system remains within 5% of the extrusion compression set at break for 24 hours at room temperature. Properties

[0129] In accordance with the present disclosure, the crosslinked thermoplastic elastomer may have a tensile elongation at break from about 30% to about 500% as measured under ASTM D412. The crosslinked thermoplastic elastomer may have a tensile elongation at break greater than or equal to about 30%, greater than or equal to about 50%, or even greater than or equal to about 100%. The crosslinked thermoplastic elastomer may have a tensile elongation at break less than or equal to about 500%, less than or equal to about 450%, less than or equal to about 400%, less than or equal to about 350%, less than or equal to about 300%, less than or equal to about 250%, or even less than or equal to about 200%. The crosslinked thermoplastic elastomer may have a tensile elongation at break from about 30% to about 500%, from about 30% to about 450%, from about 30% to about 400%, from about 30% to about 350%, from about 30% to about 300%, from about 30% to about 250%, from about 30% to about 200%, from about 50% to about 500%, from about 50% to about 450%, from about 50% to about 400%, from about 50% to about 350%, from about 50% to about 300%, from about 50% to about 250%, from about 50% to about 200%, from about 100% to about 500%, from about 100% to about 450%, from about 100% to about 400%, from about 100% to about 350%, from about 100% to about 300%, from about 100% to about 250%, or from about 100% to about 200%, or any and all endpoints and subranges therebetween.

[0130] In accordance with the present disclosure, the crosslinked thermoplastic elastomer may have a compression set from about 20% to about 90%, as measured at 100 ºC. Compression set is measured in accordance with ASTM D395B. The crosslinked thermoplastic elastomer may have a compression set less than or equal to about 90%, including, for example, a compression set less than or equal to about 80%, less than or equal to about 70%, less than or equal to about 60%, less than or equal to about 55%, or less than or equal to about 50%, as measured at 100 ºC. The crosslinked thermoplastic elastomer may have a compression set from 0% to about 90%, including for example, from about 10% to about 80%, from about 15% to about 70%, from about 20% to about 65%, from about 25% to about 60%, from about 27% to about 55%, from about 30% toabout 50%, from about 35% to about 65%, or from about 40% to about 60%, or any and all endpoints and subranges therebetween. Low compression set is indicative of high crosslink density, where 100% compression set indicates no crosslinks and 0% compression set indicates fully crosslinked thermoplastic elastomer.

[0131] In accordance with the present disclosure, the crosslinked thermoplastic elastomer may have a Shore A hardness greater than or equal to about 25 as measured under ASTM D2240, including, for example, greater than or equal to about 30, greater than or equal to about 35, greater than or equal to about 40, greater than or equal to about 45, greater than or equal to about 47, greater than or equal to about 50, greater than or equal to about 55, greater than or equal to about 57, or greater than or equal to about 60. The crosslinked thermoplastic elastomer may have a Shore A hardness less than about 95, including, for example, less than or equal to about 90, less than or equal to about 85, less than or equal to about 80, less than or equal to about 75, or even less than or equal to about 70. The crosslinked thermoplastic elastomer may have a Shore A hardness from about 25 to about 95, from about 27 to about 90, from about 30 to about 85, from about 33 to about 80, from about 35 to about 75, from about 30 to about 90, from about 30 to about 85, from about 30 to about 80, from about 30 to about 75, from about 30 to about 70, from about 35 to about 90, from about 35 to about 85, from about 35 to about 80, from about 35 to about 75, from about 35 to about 70, from about 40 to about 90, from about 40 to about 85, from about 40 to about 80, from about 40 to about 75, from about 40 to about 70, from about 45 to about 90, from about 45 to about 85, from about 45 to about 80, from about 45 to about 75, or from about 45 to about 70, including all endpoints and subranges therebetween.

[0132] In accordance with the present disclosure, the crosslinked thermoplastic elastomer may have a tensile strength at break greater than or equal to about 1.5 MPa as measured under ASTM D412, greater than or equal to about 2.0 MPa, greater than or equal to about 2.5 MPa, or even greater than or equal to about 3.0 MPa. The crosslinked thermoplastic elastomer may have a tensile strength at break less than or equal to about 8.0 MPa, including, for example, less than or equal to about 7.5 MPa, less than or equal to about 7.0 MPa, less than or equal to about 6.5 MPa, or even less than or equal to about 6.0 MPa. The crosslinked thermoplastic elastomer may have a tensile strength at break from about 1.5 MPa to about 8.0 MPa, from about 1.5 MPa to about 7.5 MPa, from about 1.5 MPa to about 7.0 MPa, from about 1.5 MPa to about 6.5 MPa, from about1.5 MPa to about 6.0 MPa, from about 2.0 MPa to about 8.0 MPa, from about 2.0 MPa to about 7.5 MPa, from about 2.0 MPa to about 7.0 MPa, from about 2.0 MPa to about 6.5 MPa, from about 2.0 MPa to about 6.0 MPa, from about 2.5 MPa to about 8.0 MPa, from about 2.5 MPa to about 7.5 MPa, from about 2.5 MPa to about 7.0 MPa, from about 2.5 MPa to about 6.5 MPa, from about 2.5 MPa to about 6.0 MPa, from about 3.0 MPa to about 8.0 MPa, from about 3.0 MPa to about 7.5 MPa, from about 3.0 MPa to about 7.0 MPa, from about 3.0 MPa to about 6.5 MPa, or even from about 3.0 MPa to about 6.0 MPa, including all endpoints and subranges therebetween.

[0133] In accordance with the present disclosure, the crosslinked thermoplastic elastomer may have an increase in weight of 170% or less after 903 oil immersion at 125 °C for 3 days, including 160% or less, 150% or less, 140% or less, 130% or less, and 125% or less. Low increase in weight after oil immersion is indicative of high crosslink density, where thermoplastic elastomer with no crosslinks will dissolve when immersed in oil. Methods of Crosslinking Thermoplastic Elastomers

[0134] In accordance with the present disclosure, a method for forming a crosslinked thermoplastic elastomer comprises blending of the thermoplastic elastomer, the nitrile butadiene rubber, and the vulcanization package to form a thermoplastic polymer blend. As described above, the vulcanization package may be a dry silane masterbatch, and the polymer pellets and the dry silane masterbatch are dry blended. The method further comprises melting the thermoplastic polymer blend to form a cross-linkable thermoplastic polymer melt, and extruding or injection molding the cross-linkable thermoplastic polymer melt to form a crosslinked thermoplastic elastomer. The method includes a one-step conversion process where the thermoplastic elastomer in the polymer pellet is crosslinked, and there is no separate silane grafting processes.

[0135] In some aspects of the present disclosure, the carbon-carbon crosslinked thermoplastic elastomer is shaped.

[0136] As described above, instead of the dry silane masterbatch, the vulcanization package may comprise a solution of the silane crosslinker and the organic peroxide. Accordingly, instead of dry blending the polymer pellets and the dry silane masterbatch and then melting the thermoplastic polymer blend, the method may comprise blending one or more polymer pellets withthe solution and melting the blend to form a cross-linkable thermoplastic polymer melt, which is further extruded or injection molded to form a crosslinked thermoplastic elastomer. EXAMPLES

[0137] Table 1 below shows sources of ingredients to form Comparative Examples C1-C9 and Examples E1-E6.

[0138] Table 1: Ingredient Brand Source nitrile butadiene rubber (NBR) CHEMIGUM® P615D Synthomer y [001erties of Comparative Examples C1-C9 and Examples E1-E6.

[0140] To prepare plaques for Comparative Examples C1-C9 and Examples E1-E6, the components of the formulations listed in Tables 2-4 were added into a 27 MM Leistriz Twin Extruder (L / D / 52) and blended at a barrel temperature of 193 °C and a rate of 300 rotations per minute. The mixed formulation was extruded at a speed of from about 3.78 g / s to about 6.30 g / s. Compression set was measured in accordance with ASTM D395. The 3-day 903 motor oil immersion test was performed on specimens in the form of 29 mm disks having a thickness of 3 mm.

[0141] Table 2 C1 C2 C3 C4 parts wt.% parts wt.% parts wt.% parts wt.% SEPTONTMV9461 - - - - 130 91 130 91 6 9 9 .0

[0142] Table 2, cont’d. C5 C6 C7 parts wt.% parts wt.% parts wt.% 1 3 3 070 °C / 3 days (%) oil; could not oil; could not oil; could not be measured be measured be measured Compression set

[0143] Table 3 C8 E1 E2 parts wt.% parts wt.% parts wt.% VE T R 21 1 1 4 1 6 5 2 6 0

[0144] Table 4 C9 E3 E4 parts wt% parts wt% parts wt% 7 6 7 7 0(%) 903 Motor oil immersion weight increase 70 °C / 3 days (%) 120 83 75

[0145] Table 4, cont’d. E5 E6 parts wt.% parts wt.% TM3 0

[0146] As sho, , er systems formed from a peroxide-vulcanizable composition including a nitrile butadiene rubber (CHEMIGUM® P615D), thermoplastic elastomer (HYBRAR™ 5217 and / or VECTOR® 2518), silane (SILQUEST™ A-171), and organic peroxide (PERKADOX® BC-FF) showed a significant improvement in oil resistance as compared to a peroxide-vulcanizable composition including the thermoplastic elastomer, the silane, and the organic peroxide without the nitrile butadiene rubber. Although Table 2 demonstrates that there is an improvement in oil resistance upon crosslinking (Comparative Examples C1-C4 as compared to Comparative Examples C5-C7), the incorporation of a nitrile butadiene rubber (Examples E1-E6) results in an even greater improvement in oil resistance than crosslinking alone.

[0147] Examination of the Comparative Examples in Table 2 further show that crosslinked SBS has better oil resistance than SIS when included in approximately similar weight percentages (Comparative Example C1 as compared to Comparative Examples C3-C4). However, the addition of nitrile butadiene (Examples E1-E6) enables the amount of SBS to be reduced without sacrificing the improvement in oil resistance.

[0148] As shown in Table 2, crosslinked polymer systems formed from a peroxide- vulcanizable composition including a thermoplastic elastomer, silane (SILQUESTTMA-171), and organic peroxide (PERKADOX® BC-FF) (Comparative Examples C1-C4) showed a reduced tensile elongation at break and a reduced compression set as compared to Comparative Examples C5-C7, non-crosslinked thermoplastic articles formed from a composition including a thermoplastic elastomer without silane and organic peroxide. As shown in Tables 3 and 4, the reduction in tensile elongation at break and compression set are maintained upon the addition of nitrile butadiene rubber (Examples E1-E6). Accordingly, the Examples demonstrate that a peroxide-vulcanizable composition including a thermoplastic elastomer, nitrile butadiene, silane, and organic peroxide results in a crosslinked polymer system having improved crosslink density and heat resistance as compared to an article that was not formed with a composition including silane and organic peroxide.

[0149] It will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

Claims

CLAIMS 1. A crosslinked polymer system comprising: a silane-grafted nitrile butadiene rubber; and a silane-grafted thermoplastic elastomer that includes mer units derived from a conjugated diene monomer; wherein the silane-grafted nitrile butadiene rubber and the silane-grafted thermoplastic elastomer are crosslinked via carbon-carbon bond crosslinks.

2. The crosslinked polymer system of claim 1, wherein the thermoplastic elastomer has a number average molecular weight of from about 30,000 g / mol to about 400,000 g / mol.

3. The crosslinked polymer system of claim 1 or claim 2, wherein the thermoplastic elastomer is a triblock copolymer that includes two polystyrene end blocks, and wherein the styrene content of the two polystyrene end blocks in the thermoplastic elastomer is from about 10 wt.% to about 50 wt.%.

4. The crosslinked polymer system of any preceding claim, wherein the thermoplastic elastomer comprises styrene-butadiene-styrene (SBS) or styrene / isoprene block copolymer (SIS).

5. The crosslinked polymer system of any preceding claim, wherein the thermoplastic elastomer copolymer is non-hydrogenated.

6. The crosslinked polymer system of any preceding claim, wherein the styrene / diene copolymer is partially hydrogenated.

7. The crosslinked polymer system of any preceding claim, wherein the crosslinked polymer system includes silane crosslinks.

8. The crosslinked polymer system of any preceding claim, wherein the crosslinked polymer system is a thermoplastic vulcanizate.

9. The crosslinked polymer system of any preceding claim, further comprising an olefin polymer.

10. A peroxide-vulcanizable composition comprising: a thermoplastic elastomer comprising vinyl aromatic monomeric units and conjugated diene monomeric units; a nitrile butadiene rubber; and a vulcanization package comprising an organic peroxide and a silane.

11. The peroxide-vulcanizable composition of claim 10, wherein the peroxide-vulcanizable composition comprises from about 25 wt.% to about 95 wt.% of the thermoplastic elastomer, or from about 30 wt.% to about 85 wt.% of the thermoplastic elastomer, or from about 35 wt.% to about 75 wt.% of the thermoplastic elastomer.

12. The peroxide-vulcanizable composition of claim 10 or claim 11, wherein the peroxide vulcanizable composition comprises from about 15 wt.% to about 50 wt.% of the nitrile butadiene rubber.

13. The peroxide-vulcanizable composition of any one of claims 10-12, wherein the thermoplastic elastomer is selected from the group consisting of styrene-butadiene rubber, styrene- butadiene block copolymers, styrene-isoprene block copolymers, styrene-butadiene-isoprene rubber, styrene-butadiene / isoprene block copolymers, styrene-butadiene-isoprene block copolymers, and combinations thereof.

14. The peroxide-vulcanizable composition of any one of claims 10-13, wherein the thermoplastic elastomer is a triblock copolymer that includes two polystyrene end blocks, and wherein the styrene content of the two polystyrene end blocks in the thermoplastic elastomer is from about 10 wt.% to about 50 wt.%.

15. The peroxide-vulcanizable composition of any one of claims 10-14, wherein the peroxide- vulcanizable composition comprises from about 0.5 wt.% to about 5 wt.% of the silane.

16. The peroxide-vulcanizable composition of any one of claims 10-15, wherein the silane comprises vinyl trimethoxysilane, vinyl triethoxysilane, or a combination thereof.

17. The peroxide-vulcanizable composition of any one of claims 10-16, wherein the peroxide- vulcanizable composition comprises from about 0.05 wt.% to about 1 wt.% of the organic peroxide.

18. The peroxide-vulcanizable composition of any one of claims 10-17, wherein the organic peroxide comprises peroxyketal peroxide, di-tert alkyl peroxide, or a combination thereof.

19. The peroxide-vulcanizable composition of claim 18, wherein the di-tert alkyl peroxide comprises dicumyl peroxide.

20. The peroxide-vulcanizable composition of any one of claims 8-17, further comprising an olefin polymer.

21. The peroxide-vulcanizable composition of claim 20, wherein the olefin polymer is a polypropylene.

22. The peroxide-vulcanizable composition of any one of claims 10-21, further comprising an oil.

23. A process for making the crosslinked polymer system of claim 1 comprising the steps of: preparing a carbon-carbon crosslinked, silane-grafted blend by blending a thermoplastic elastomer that includes mer units derived from a conjugated diene monomer, a nitrile butadiene rubber, an organic peroxide, and a silane such that the thermoplastic elastomer and the nitrile butadiene rubber include carbon-carbon bond crosslinks and grafted silane moieties; and extruding the carbon-carbon crosslinked, silane-grafted blend.

24. The process of claim 23, wherein the step of blending the thermoplastic elastomer, the organic peroxide, and the silane is performed in the absence of a catalyst.

25. The process of claim 22 or claim 24, wherein the step of blending the thermoplastic elastomer, the organic peroxide, and the silane is performed in the absence of moisture.

Images