Elastomeric Material

Abstract

An elastomeric material for providing electrical stress control comprises 5 to 40 volume percent low structured carbon black, 0.5 to 10 volume percent of high structured carbon black, up to about 30 volume percent of high permittivity inorganic fillers, and a remainder of polymeric carrier material and functional additives.

Claims

1. An elastomeric material for providing electrical stress control, comprising: 5 to 40 volume percent low structured carbon black; 0.5 to 10 volume percent of high structured carbon black; up to about 30 volume percent of high permittivity inorganic fillers; and a remainder of polymeric carrier material and functional additives.

2. The elastomeric material of claim 1, wherein the inorganic filler is less than 20 volume percent of the elastomeric material.

3. The elastomeric material of claim 1, wherein the inorganic filler comprises barium titanate.

4. The elastomeric material of claim 1, wherein the inorganic filler comprises titanium dioxide.

5. The elastomeric material of claim 1, wherein the polymeric carrier materials are selected from a group of ethylene, propylene, and diene monomer rubber.

6. The elastomeric material of claim 1, wherein the elastomeric material comprises thiophenol as a functional additive.

7. The elastomeric material of claim 1, wherein the elastomeric material has a relative permittivity greater than 15.

8. The elastomeric material of claim 1, wherein an elastomeric material dissipation factor of the material is less than 0.1 in 50 Hz to 60 Hz AC dielectric fields up to 2 kV/mm.

9. The elastomeric material of claim 1, wherein an elastomeric material dissipation factor of the material is less than 0.1 at frequencies from 1 Hz to 10 MHz.

10. The elastomeric material of claim 1, further comprising zinc stearate.

11. A heat or cold shrinkable article, comprising: an elastomeric material including: 5 to 40 volume percent low structured carbon black; 0.5 to 10 volume percent of high structured carbon black; up to about 30 volume percent of high permittivity inorganic fillers; and a remainder of polymeric carrier material and functional additives.

12. The article of claim 11, wherein the inorganic filler is less than 20 volume percent of the elastomeric material.

13. The article of claim 11, wherein the inorganic filler includes at least one of barium titanate or titanium dioxide.

14. The article of claim 13, wherein the polymeric carrier materials are selected from a group of ethylene, propylene, and diene monomer rubber.

15. The article of claim 11, wherein the elastomeric material comprises thiophenol as a functional additive.

16. The article of claim 11, wherein the elastomeric material has a relative permittivity greater than 15.

17. The article of claim 11, wherein an elastomeric material dissipation factor of the material is less than 0.1 in 50 Hz to 60 Hz AC dielectric fields up to 2 kV/mm.

18. The article of claim 11, wherein an elastomeric material dissipation factor of the material is less than 0.1 at frequencies from 1 Hz to 10 MHz.

19. The article of claim 11, wherein the article is formed by extruding, and the elastomeric material further includes an extrusion aid.

20. An elastomeric material for providing electrical stress control, comprising: 5 to 40 volume percent low structured carbon black; 0.5 to 10 volume percent of high structured carbon black; up to about 30 volume percent of high permittivity inorganic fillers including at least one of barium titanate or titanium dioxide; and a remainder of polymeric carrier material and functional additives.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] Exemplary embodiments of the present disclosure will be described hereinafter in detail. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein; rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the disclosure to those skilled in the art.

[0014] In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details.

[0015] The elastomeric material according to the present disclosure comprises inorganic fillers and high structure carbon black The incorporation of inorganic filler particles along with high structure carbon particles in a matrix of elastomeric material improve the electrical stress tolerance while retaining the essential insulating, rheological and mechanical properties. Further, the elastomeric material having high structure carbon black and inorganic fillers of the present disclosure show a low dissipation factor along a broad range of frequencies. The elastomeric material according to the present disclosure exhibiting a combination of all of these seemingly incompatible properties would be desirable for use in the high-electrical stresses, variable frequencies, and voltages environments that are frequently encountered in the electrical industry.

[0016] The elastomeric material according to the present disclosure has a further advantage in that it does not require a state change to recover and can be used both as a hot shrink and a cold shrink. The optimized use of high structured carbon black imparts the elastomeric material according to the present disclosure with the distinguishing technical effects like high permittivity, low dissipation factor with minimal loading of the high permittivity filler while maintaining good mechanical and rheological properties.

[0017] According to an exemplary embodiment of the present disclosure disclosed is an elastomeric material for providing electrical stress control and comprising: 5 to 40 volume percent low structured carbon black, 0.5 to 10 volume percent of high structured carbon black, up to about 30 volume percent of high permittivity inorganic fillers, and remaining of polymeric carrier material and functional additives.

[0018] According to another exemplary embodiment of the present disclosure inorganic filler in the elastomeric material is preferably less than 20 volume percent of the elastomeric material.

[0019] According another exemplary embodiment of the present disclosure inorganic filler comprises barium titanate.

[0020] According to another exemplary embodiment of the present disclosure said inorganic filler comprises titanium dioxide.

[0021] According to another exemplary embodiment of the present disclosure the polymeric carrier materials for the elastomeric composition is selected from the group of ethylene, propylene, diene monomer rubber.

[0022] According to another exemplary embodiment of the present disclosure the elastomeric material comprises preferably thiophenol as functional additive.

[0023] According to another exemplary embodiment of the present disclosure the elastomeric material has relative permittivity greater than 15.

[0024] According to another exemplary embodiment of the present disclosure the elastomeric material has dissipation factor is less than 0.1 in 50 Hz to 60 Hz AC dielectric fields up to 2 kV/mm.

[0025] According to another exemplary embodiment of the present disclosure the elastomeric material dissipation factor is less than 0.1 at frequencies from 1 Hz to 10 MHz.

[0026] According to an exemplary embodiment of the present disclosure disclosed does an article for use in heat shrink and/or cold shrink that comprise an elastomeric material according to any of embodiments of the present disclosure.

[0027] According to an exemplary embodiment of the present disclosure disclosed is an insulation material for electrical stress control that comprise the elastomeric material according to any of embodiments of the present disclosure.

[0028] According to an exemplary embodiment of the present disclosure disclosed is use of elastomeric material according to any of embodiments of the present disclosure for insulating electric cables.

[0029] According to an exemplary embodiment of the present disclosure disclosed is use of the elastomeric material according to any of embodiments of the present disclosure for medium stress control termination tubing.

[0030] Table 1 shows the standards use for measuring the physical parameters of the elastomeric material according to the examples of the present disclosure.

TABLE-US-00001 TABLE 1 Parameter Measurement Standard Permittivity IEC 62631-1 Dissipation Factor IEC 62631-1 Hardness Shore A ASTM D2240-15e1 100% Modulus ASTM D412-16 Ultimate Tensile Strength ASTM D412-16 Ultimate Tensile Strain ASTM D412-16 Dielectric Strength ASTM D149-09 (213)

[0031] The advantages of a high permittivity and low dissipation factor exhibited by the elastomeric material of the present disclosure comprising an optimized amount of high structure carbon black and inorganic high permittivity filler may be attributed to the percolation phenomenon inherently seen with the high structure carbon black.

[0032] The elastomeric material according to the present disclosure is capable of being extruded or molded into a tubular shape, and in a preferred embodiment can also be expanded onto a core for subsequent application. Such a device is typically designated a “PST”, which stands for pre-stretched tube. The core can be external, i.e. on the outside of the tube, or can be inside the tube. Preferably, the core is internal and is a one-piece rigid spiral core having interconnected adjacent coils in a closed helix configuration.

[0033] By utilizing this PST technique, a completely insulated termination can be applied in a one-step operation. The application consists essentially of a high permittivity tube covered by an arc/track and weather resistant insulation, which is applied to the prepared cable simultaneously with core removal. This can provide a completely insulated termination in which the electric field stresses are controlled effectively by the high permittivity tube through the refraction of electric flux lines at the interface between the cable insulation and high permittivity tube. Another characteristic of a PST that more directly pertains to the method, in which it is applied, is cold shrink. This implicitly means that such devices may be applied to cables without the necessity of a heat source, as is conventionally used with heat shrink tubing. Rather, the characteristics of shrinking behavior are a function of superior elastic memory characteristics of the composition. The composition may also be formulated so as to be utilized in accordance with conventional slide-on techniques.

[0034] The elastomeric material comprises 5 to 40 volume percent of low structured carbon black. The carbon black may consist of essentially any commercial grade, from the large particulate size thermal types to the fine reinforcing furnace grades, including the materials termed conductive carbon black. A preferred carbon black, especially for PST applications, is a coarse furnace grade. Preferably, 10 to 30 volume percent of low structured carbon black of the composition is used. Carbon black is necessary to achieve an effective refraction of electric flux lines in the terminating device, and yet allow maintenance of a desired level of elasticity. Typically, the larger the particle size of the carbon black and the lower the structure thereof, the greater the volume fraction thereof is necessary. For the composition of the present disclosure, 7 to 25 volume percent of low structured carbon black is most preferred.

[0035] High structure carbon black exhibits a higher surface area when compared to low structure carbon black. The elastomeric material comprises 0.5 to 10 volume percent of high structured carbon black, and preferably 1 to 7 volume percent of high structured carbon black, and most preferably 3 to 5 volume percent of high structured carbon black. The percolation phenomenon exhibited by high-structure carbon black leads to surprising effects of the enhanced dielectric performance of elastomeric material. The percolation threshold depends on the structure of the carbon black and high structure carbon black leads to high permittivity and low dissipation factor of the elastomeric material according to the present disclosure.

[0036] While not absolutely essential to functionality of the elastomeric material according the present disclosure, it has been determined that the incorporation of high permittivity inorganic fillers can provide desirable results in the composition of the elastomeric material. Examples of such materials include barium titanate, titanium dioxide, strontium titanate, etc. The use of such materials can provide superior permittivity stability over a range of electrical stresses and can assist in the generation of lower electrical loss for a given permittivity level. Up to about 30.0 percent by volume of these fillers can be included, with less than about 20.0 percent being preferred. The inorganic fillers that are used in the elastomeric material of the present disclosure have been used in the known materials for high performance electrical stress grading materials. However, the combination of high structure carbon black with inorganic fillers exhibiting enhanced dielectric performance is a surprising effect of the present disclosure. Furthermore, the inorganic fillers of the present disclosure can be replaced with liquid rubbers for producing tape/patch products with comparable superior dielectric characteristics.

[0037] The balance of the elastomeric material according to the present disclosure comprises polymeric carrier materials like ethylene, propylene, diene monomer rubber and other functional additives like anti-oxidants and stabilizers. The preferred functional additives are selected from the group of commercially available functional additives like Irganox-1010, Evanstab 1218, Lowinox TBm-6 and likes thereof. To the person skilled in the art it is readily recognizable that any other functional additives can also be used. Furthermore, the elastomeric material also uses the extrusion aids of the like of Zinc stearate.

[0038] The term “balance”, in this case, means normal conventional operations in which ingredients are added to provide the required processing behavior and physical properties of the elastomeric material. Processing could entail open mill or internal mixing, extrusion, steam autoclave or continuous vulcanization or molding techniques. In keeping with conventional preparation of such elastomeric materials, typical process aids, process oils, coupling agents, and vulcanizing agents (if necessary) are included in the compounded elastomeric component.

[0039] As aforementioned, one of the key characteristics of the elastomeric material according to the present disclosure is the high permittivity but a low loss (dissipation factor). Both these physical parameters are consistent and stable across a range of frequencies and voltages. The elastomeric material of the present disclosure shows a relative permittivity higher than 15 with dissipation factor less than 0.1 from electric field ranges of 1 to 2 kV/mm and frequency ranges of 1 Hz to 10 MHz

[0040] The disclosure will now be specifically defined by the aid of the following non-limiting examples, wherein all parts are by weight unless otherwise specified.

Example 1

[0041] An elastomeric material was prepared by utilizing the following composition:

TABLE-US-00002 Part By Weight Vistalon 3666 (trade name for an ethylene/propylene/diene 42.7 monomer rubber commercially available from EXXON MOBIL) Vistalon 2502 (trade name for an polyisobutylene rubber 5.4 commercially available from EXXON MOBIL) Oppanol B13 SFN (trade name for an 5.4 ethylene/propylene/diene monomer rubber commercially available from BASF) N990 Carbon Black (a low structured grade commercially 42 available from Cancarb) N330 Carbon Black (a highly structured carbon black 3 commercially available from Cabot) Irganox-1010 (tradename for a sterically hindered primary 0.5 phenolic antioxidant stabilizer commercially available from BASF) Evanstab 1218 (tradename for a Lauryl/Stearyl 1 Thiodipropionate secondary antioxidant stabilizer commercially available from EVANS CHEMETICS)

[0042] This provides for a concentration in percent by volume of 26.5 for low structured carbon black and 4.3 for the high-structured carbon black. (Concentration level is specified in terms of volume percentage because electrical characteristics are dependent on the spatial arrangement of particles. The composition was extruded, together with an insulating outer layer into a high permittivity coextruded tubing using a conventional cold feed extruder and vulcanized with the use of an electron beam irradiation source.

[0043] As for the physical properties the material exhibited 100 percent modulus of 0.6 MPa; permittivity value was of 10; dissipation factor was found to be 0.007; hardness shore A was measured to be 30, the ultimate tensile strength was of 2.4 MPa; ultimate tensile strain was of 750% and dielectric strength was of 7.2 kV/mm.

Example 2

[0044] An elastomeric material was prepared as per Example 1 using the following components:

TABLE-US-00003 Part By Weight Nordel IP4640 (trade name for an 41 ethylene/propylene/diene monomer rubber commercially available from DOW) EVATANE 28-40 (trade name for an ethyl vinyl acetate 10 commercially available from Arkema) N990 Carbon Black (a low structured grade 42 commercially available from Cancarb) N330 Carbon Black (a highly structured carbon black 3 commercially available from Cabot) Irganox-1010 (tradename for a sterically hindered 1 primary phenolic antioxidant stabilizer commercially available from BASF) Zinc-Stearate (tradename for a polymeric extrusion 2 process aid ecommercially available from Univar) Lowinox TBM-6 (tradename for a hindered thiophenol 1 antioxidant stabilizer commercially available from Addivant)

[0045] As for the physical properties, the material exhibited 100 percent modulus of 2.4 MPa; permittivity value was of 24; dissipation factor was found to be 0.25; hardness shore A was measured to be 70, the ultimate tensile strength was of 7.2 MPa; ultimate tensile strain was of 650% and dielectric strength was of 7.3 kV/mm.

[0046] Composition demonstrated the use of a low-level elastomeric polymer ethylene-vinyl acetate (EVA) which is “rubber like” in its softness and flexibility. The characteristics of the EVA material from the semi crystalline structure of the polymer and the presence of the vinyl acetate group creates a polar polymer network that can be used to enhance the dielectric properties of a stress control material.

Example 3

[0047] An elastomeric material was prepared as per Example 1 using the following components:

TABLE-US-00004 Part By Weight Nordel IP4640 (trade name for an 49.5 ethylene/propylene/diene monomer rubber commercially available from DOW) Epichlomer D (trade name for an Epichlorohydrin rubber 1.5 commercially available from Osaka Soda) N990 Carbon Black (a low structured grade commercially 42 available from Cancarb) N330 Carbon Black (a highly structured carbon black 3 commercially available from Cabot) Irganox-1010 (tradename for a sterically hindered 1 primary phenolic antioxidant stabilizer commercially available from BASF) Zinc-Stearate (tradename for a polymeric extrusion 2 process aid ecommercially available from Univar) Lowinox TBM-6 (tradename for a hindered thiophenol 1 antioxidant stabilizer commercially available from Addivant)

[0048] As for the physical properties, the material exhibited 100 percent modulus of 1.1 MPa; permittivity value was of 30; dissipation factor was found to be 0.5; hardness shore A was measured to be 40, the ultimate tensile strength was of 6.0 MPa; ultimate tensile strain was of 900% and dielectric strength was of 6.5 kV/mm.

[0049] Composition demonstrated the use of a low level a chlorinated rubber. The presence of the chlorine creates a highly polar polymer network which can be used to enhance the dielectric properties of a stress control material.

Example 4

[0050] An elastomeric material was prepared as per Example 1 using the following components:

TABLE-US-00005 Part By Weight Nordel IP4640 (trade name for an 50 ethylene/propylene/diene monomer rubber commercially available from DOW) N990 Carbon Black (a low structured grade 10 commercially available from Cancarb) N330 Carbon Black (a highly structured carbon black 3 commercially available from Cabot) Irganox-1010 (tradename for a sterically hindered 1 primary phenolic antioxidant stabilizer commercially available from BASF) Zinc-Stearate (tradename for a polymeric extrusion 2 process aid ecommercially available from Univar) Lowinox TBM-6 (tradename for a hindered thiophenol 1 antioxidant stabilizer commercially available from Addivant) Tioxide TR81 (tradename for titanium dioxide 20 commercially available from HUNTSMAN)

[0051] As for the physical properties, the material exhibited 100 percent modulus of 1.2 MPa; permittivity value was of 30; dissipation factor was found to be 0.5; hardness shore A was measured to be 40, the ultimate tensile strength was of 4.5 MPa; ultimate tensile strain was of 600% and dielectric strength was of 8.0 kV/mm.

[0052] Composition demonstrated the use of high permittivity filler titanium dioxide. Titanium dioxide has a typical particle permittivity >50 and with the dielectric properties given by the percolation of the carbon black a high permittivity material can be formulated.

Example 5

[0053] An elastomeric material was prepared as per Example 1 using the following components:

TABLE-US-00006 Part By Weight Nordel IP4640 (trade name for an ethylene/propylene/diene 21 monomer rubber commercially available from DOW) N990 Carbon Black (a low structured grade commercially 19 available from Cancarb) N330 Carbon Black (a highly structured carbon black 1.2 commercially available from Cabot) Irganox-1010 (tradename for a sterically hindered primary 0.5 phenolic antioxidant stabilizer commercially available from BASF) Zinc-Stearate (tradename for a polymeric extrusion process 0.8 aid ecommercially available from Univar) Lowinox TBM-6 (tradename for a hindered thiophenol 0.5 antioxidant stabilizer commercially available from Addivant) HBPT-01 (tradename for barium titanate commercially 58 available from Whyte Chemicals)

[0054] The material exhibited 100 percent modulus of 1.5 MPa; permittivity value was of 30; dissipation factor was found to be 0.1; hardness shore A was measured to be 50, the ultimate tensile strength was of 3.5 MPa; ultimate tensile strain was of 500% and dielectric strength was of 7.5 kV/mm.

[0055] Composition demonstrated the use of high permittivity filler barium titanate. Barium Titanate has a typical particle permittivity >200 and with the dielectric properties given by the percolation of the carbon black a high permittivity material can be formulated.

[0056] It should be appreciated for those skilled in this art that the above embodiments are intended to be illustrated, and not restrictive. For example, many modifications may be made to the above embodiments by those skilled in this art, and various features described in different embodiments may be freely combined with each other without conflicting in configuration or principle.

[0057] Although several exemplary embodiments have been described, it would be appreciated by those skilled in the art that various changes or modifications may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.

[0058] As used herein, an element recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.