SECONDARY BATTERY PACK WITH IMPROVED THERMAL MANAGEMENT

Abstract

The present invention relates to a novel secondary battery pack with improved thermal management useful for an all-electric vehicle (EV), a plug-in hybrid vehicle (PHEV), a hybrid vehicle (HEV), or battery packs used for other vehicles batteries, and more particularly, to the use of a specific material for thermally insulating a secondary battery pack and further minimizing the propagation of thermal runaway within a battery pack.

Claims

1. A secondary battery pack comprising: at least one battery module casing 102 in which is disposed a plurality of battery cells 103 which are electrically connected to one another, a silicone rubber syntactic foam comprising a silicone rubber binder and hollow glass beads, and said silicone rubber syntactic foam fills partially or fully the open space of said battery module casing 102 and/or covering partially or totally said battery cells 103 and/or covering partially or totally said module casing 102, and optionally a lid covering the battery module casing 102, wherein the silicone rubber binder in which hollow glass beads are dispersed are obtained by curing a condensation type organopolysiloxane composition and wherein hollow glass beads are hollow borosilicate glass microspheres which have true density ranging from 0.10 gram per cubic centimeter to 0.65 gram per cubic centimeter.

2. A secondary battery pack according to claim 1, wherein battery cells 103 are of lithium-ion type.

3. A secondary battery pack according to claim 1, further comprising a plurality of heat dissipation members which are disposed at two or more interfaces between the battery cells, and at least one heat exchange member integrally interconnecting the heat dissipation members which is mounted to one side of the battery module casing 102, whereby heat generated from the battery cells during the charge and discharge of the battery cells is removed by the heat exchange member.

4. A secondary battery pack according to claim 3, wherein heat dissipation members are made of a thermally conductive material exhibiting high thermal conductivity and the heat exchange member is provided with one or more coolant channels for allowing a coolant such as a liquid or a gas to flow there.

5. A secondary battery pack according to claim 1, wherein the level of hollow glass beads is up to 80% volume loading in the silicone rubber syntactic foam, and preferably between 5% and 70% by volume loading of the silicone rubber syntactic foam.

6. A secondary battery pack according to claim 1, wherein said silicone rubber syntactic foam is used as a potting material disposed either in said battery module casing 102 to at least partially encapsulate said plurality of battery cells 103 and/or outside the battery module casing 102 so as to at least partially encapsulate the said battery module casing 102.

7. A process for preparation of a secondary battery pack as defined in claim 1 comprising the steps of: a) preparing at least one battery module casing 102 in which is disposed a plurality of battery cells 103 which are electrically connected to one another, b) introducing into the said battery module casing 102 the addition curing type organopolysiloxane composition X as defined in claim 3 or 11, c) filling completely or partially said battery module casing 102, and d) allowing the curing to occur so as to form a silicone rubber syntactic foam comprising a silicone rubber binder and hollow glass beads, and optionally e) covering the battery module casing 102 with a lid.

8. A secondary battery pack according to claim 1 which is located within a vehicle.

9. A secondary battery pack according to claim 1 which is located in an automotive motor vehicle.

10. A secondary battery pack according to claim 1 which is located in an all-electric vehicle (EV), a plug-in hybrid vehicle (PHEV), a hybrid vehicle (HEV).

11. A secondary battery pack according to claim 1 which is located in: an aircraft, a boat, a ship, a train or wall unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0179] FIG. 1 provides a top view of a secondary battery pack without a lid with batteries inside the pack;

[0180] FIG. 2 provides a perspective view of a secondary battery pack with batteries inside the pack;

[0181] FIG. 3 provides a top view of batteries in a secondary battery pack with silicone rubber syntactic foam according to the invention filling the space between batteries and the remaining space in the pack;

[0182] FIG. 4 provides a top view of battery cells in a secondary battery pack covered with silicone rubber syntactic foam according to the invention and with said foam filling the space between batteries and the remaining space in the pack;

[0183] FIGS. 5 and 6 provide a schematic representation of two preferred embodiments of a method for producing an addition curing type organopolysiloxane composition X wherein the inhibitor master batch MI and catalyst master batch MC are separately fed into other components so as to control the curing rate.

[0184] FIGS. 1 and 2 show that battery cells 103 can be very close together in a battery module casing 102. In one embodiment of the invention a crosslinkable silicone composition according to the invention and precursor of a lightweight silicone rubber syntactic foam comprising a silicone rubber binder and hollow glass beads is poured into the battery module casing 102 after the batteries have been placed and installed (FIG. 3, 104) and yield to a silicone syntactic foam when it is cured (FIG. 4. 105).

[0185] FIG. 5 shows a method for producing an addition curing type organopolysiloxane composition X according to one embodiment of the invention wherein said liquid silicone base MS1 is stored in a storage tank 1, said catalyst master batch MC is stored in a storage tank 20, said inhibitor master batch MI is stored in a storage tank 50 and said additive masterbatch MA is stored in a storage tank 65 and are fed separately into their respective feed lines 200, 210, 220 and 230 respectively. The storage tank 1 of the liquid silicone base MS2 is connected to the stirring tank 80 via a feed pump 10, which can be any large displacement pump, and via an optional feed rate adjuster 15. The storage tank 20 of the catalyst master batch MC is connected to the stirring tank 80 via a feed pump 25, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 30. The storage tank 50 of the inhibitor master batch MI is connected to the stirring tank 80 via a feed pump 55, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 60. The storage tank 65 of the additive masterbatch MA is connected to the stirring tank 80 via a feed pump 70, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 75. When said liquid silicone base MS2, said catalyst master batch MC and said inhibitor master batch MI and optionally said additive masterbatch MA are directed into said stirring tank 80; the resulting mixture is mixed preferably by using a high flow, low-shear mixer to yield the addition curing type organopolysiloxane composition X according to the invention. Said composition is now available to be introduced into the said battery module casing 102 by mean 100 which could be either via an injection apparatus or via a pump to allow free flow to fill the free spaces of battery module casing 102 and cures via crosslinking.

[0186] FIG. 6 shows a method for producing an addition curing type organopolysiloxane composition X according to another embodiment of the invention wherein said liquid silicone base MS2 is stored in a storage tank 1, said catalyst master batch MC is stored in a storage tank 20, said inhibitor master batch MI is stored in a storage tank 50 and said additive masterbatch MA is stored in a storage tank 65 and are fed separately into their respective feed lines 200, 210, 220 and 230 respectively. The storage tank 1 of the liquid silicone base MS2 is connected to the stirring tank 80 via a feed pump 10, which can be any large displacement pump, and via an optional feed rate adjuster 15. The storage tank 20 of the catalyst master batch MC is connected to the stirring tank 80 via a feed pump 25, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 30. The storage tank 50 of the inhibitor master batch MI is connected to the stirring tank 80 via a feed pump 55, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 60. The storage tank 65 of the additive masterbatch MA is connected to the stirring tank 80 via a feed pump 70, which can be any small piston displacement pump, gear pump, micro motion injector pump, or other positive displacement pump, and via an optional feed rate adjuster 75. When said liquid silicone base MS2, said catalyst master batch MC and said inhibitor master batch MI and optionally said additive masterbatch MA are directed into said stirring tank 80; the resulting mixture is mixed preferably by using a high flow, low-shear mixer. To said resulting mixture, hollow glass beads D and preferably hollow borosilicate glass microspheres D1 which are stored in storage tank 90, which is preferably a hopper, are transferred into said stirring tank 80 either directly by gravity discharge or via screw feeder 95 to yield addition curing type organopolysiloxane composition X according to the invention. Said composition is now available to be introduced into the said battery module casing 102 by mean 100 which could be either via an injection apparatus or via a pump to allow free flow to fill the free spaces of battery module casing 102 and cures via crosslinking.

[0187] Other advantages provided by the present invention will become apparent from the following illustrative examples.

EXAMPLES

I) Definition of the Components

[0188] Organopolysiloxane A1=polydimethylsiloxane with dimethylvinylsilyl end-units with a viscosity at 25° C. ranging from 80 mPa.Math.s to 120 mPa.Math.s; Organopolysiloxane A2=polydimethylsiloxane with dimethylvinylsilyl end-units with a viscosity at 25° C. ranging from 500 mPa.Math.s to 650 mPa.Math.s;

[0189] Organopolysiloxane B1 (CE) as chain extender=polydimethylsiloxane with dimethylsilylhydride end-units with a viscosity at 25° C. ranging from 7 mPa.Math.s to 10 mPa.Math.s and formula: M′D.sub.xM′

In which: [0190] D is a siloxy unit of formula (CH.sub.3).sub.2SiO.sub.2/2 [0191] M′ is a siloxy unit of formula (CH.sub.3).sub.2(H)SiO.sub.1/2 [0192] and x is an integer ranging from 8 to 11;

[0193] Organopolysiloxane B2 (XL) as crosslinker, with a viscosity at 25° C. ranging from 18 mPa.Math.s to 26 mPa.Math.s, over 10 SiH reactive groups are present (in average from 16 to 18 SiH reactive groups): poly(methylhydrogeno) (dimethyl)siloxane with SiH groups in-chain and end-chain (α/ω),

[0194] Hollow glass beads D1: 3M™ Glass Bubbles Series S15, sold by 3M Company, Particle Size (50%) microns by volume=55 microns, Isostatic Crush Strength: Test Pressure 300 psi (2.07 MPa.), True Density (g/cc)=0.15.

[0195] Hollow glass beads D2: 3M™ Glass Bubbles Series K25, sold by 3M Company, (Particle Size (50%) microns by volume=55 microns, Isostatic Crush Strength Test Pressure 750 psi, True Density (g/cc)=0.25.

[0196] Cure rate controller G1: 1,3,5,7-tetramethyl-1,3,5,7-tetravinyl-cyclotetrasiloxane.

[0197] Cure rate controller G2: 1-Ethynyl-1-cyclohexanol (ECH).

[0198] Catalyst C: 10% platinum as Karstedt catalyst in 350 cS dimethylvinyldimer, sold by Johnson Matthey Company.

[0199] Reactive diluent E=1-tetradecene.

II) Examples Part I

[0200]

TABLE-US-00001 TABLE 1 Inventive two-parts formulation 1 precursor of a silicone rubber syntactic foam Part A Parts by weight Organopolysiloxane A1 81.88 Reactive diluent E 5.03 Catalyst C 0.037 hollow glass beads D1 13.05 Part B Organopolysiloxane A1 81.88 Organopolysiloxane B2 (XL) 8.6 Organopolysiloxane B1 (CE) 53.41 Cure rate controller G1 0.01 hollow glass beads D1 13.05

TABLE-US-00002 TABLE 2 Inventive two-parts formulation 2 precursor of a silicone rubber syntactic foam. Part A Parts by weight Organopolysiloxane A1 78.27 Reactive diluent E 8.62 Catalyst C 0.063 hollow glass beads D1 13.05 Part B Organopolysiloxane A1 69.23 Organopolysiloxane B2 (XL) 2.46 Organopolysiloxane B1 (CE) 15.26 Cure rate controller G1 0.0029 hollow glass beads D1 13.05 [0201] For two-parts formulation 1, parts A and B were combined as a 6:1 w/w (weight ratio) to prepare the compositions I before curing [0202] For two-parts formulation 2, parts A and B were combined as a 1:1 w/w (weight ratio) to prepare the compositions II before curing.

[0203] Each formulation 1 and 2 were poured before curing inside a battery module casing 102 in which was disposed a plurality of battery cells 103 which were electrically conductively connected to one another. The curing occurred at room temperature to yield a rubber syntactic foam comprising a silicone rubber binder and hollow glass beads which filled fully the open space of said battery module casing 102 and covered totally said battery cells 103.

III) Examples Part II

[0204]

TABLE-US-00003 TABLE 3 Formulation 3-Comparative The following formulations were prepared: Part A Percent by weight Organopolysiloxane A1   99.8% Catalyst C    0.2% Total   100.0% Part B Percent by weight Organopolysiloxane A1  78.0749% Organopolysiloxane B1 (CE)  19.5550% Organopolysiloxane B2 (XL)  2.3689% Cure rate controller G2   0.0012% Total 100.0000%

TABLE-US-00004 TABLE 4 Formulation 4-Invention Part A Percent by weight Organopolysiloxane A1  83.6900% Catalyst C  0.0335% Hollow glass beads D2  16.2800% Total 100.0035% Part B Percent by weight Organopolysiloxane A1   65.21% Organopolysiloxane B1 (CE)   16.69% Organopolysiloxane B2 (XL)   1.82% Hollow glass beads D2   16.28% Total  100.00%

TABLE-US-00005 TABLE 5 Formulation 5-Invention Part A Percent by weight Organopolysiloxane A1  80.0396% Catalyst C  0.1604% Hollow glass beads D2  19.8000% Total 100.0000% Part B Percent by weight Organopolysiloxane A1  62.6161% Organopolysiloxane B1 (CE)  15.6831% Organopolysiloxane B2 (XL)  1.8999% Cure rate controller G2  0.0010% Hollow glass beads D2  19.8000% Total 100.0000% [0205] Formulation 3 was mixed at 1:1 mix ratio by weight and cured at room temperature (25° C.) overnight for 16 hours to yield a cured silicone elastomer. [0206] Formulations 4 to 7 were mixed at 1:1 mix ratio by weight and cured at room temperature (25° C.) overnight for 16 hours to yield silicone syntactic foams according to the inventions. [0207] Formulation 8 was prepared by mixing at 1:1 mix ratio by weight the two part component sold by Elkem Silicones under the reference RTV-3040 (2 part component, polyaddition curing system) and cured at room temperature (25° C.) overnight for 16 hours to yield a cured silicone elastomer. [0208] Formulation 9 was prepared by mixing at 1:1 mix ratio by weight the two part component sold by Elkem Silicones under the reference Bluesil™ ESA 7242 (which is a two-component heat curing liquid silicone elastomer that cross-links by a polyaddition) and was cured at room temperature (25° C.) overnight for 16 hours to yield a cured silicone elastomer. [0209] Formulation 10 has been prepared based on Sakrete Concrete The concrete used was from SAKRETE of North America, LLC located in Charlotte, N.C. The product is called SAKRETE High Strength Concrete Mix. The concrete sample was made using the following process: [0210] Pour 1 kg of the high strength concrete mix into a container forming an indentation in the center of the concrete. [0211] Enough water was added to obtain a workable mix (70 g). [0212] Material was poured into a 51 mm diameter mold. [0213] The material was worked into voids and then flattened with a metal spatula. [0214] The material was allowed to harden until a thumb print could not be left in the material. [0215] A metal spatula was used to obtain a desired finish and flatness as the material was hardening. [0216] The material was kept moist and underneath plastic for 7 days while constantly being kept at room temperature.

TABLE-US-00006 TABLE 8 Physical properties of the cured products Cured Tensile Strength Specific Durometer Samples psi Gravity Shore A Formulation 5 (Invention) 40.0 0.55 80 Formulation 7 (Invention) 18.4 0.61 62 Formulation 4 (Invention) 18.9 0.67 53 Formulation 6 (Invention) 16.1 0.55 59 Formulation 3 (Comparative) Gel Gel Gel Formulation 9 (Comparative) 48.0 1.37 48

TABLE-US-00007 TABLE 9 Thermal conductivity measurement of cured samples. Cured Bulk Thermal sample Conductivity (W/m.K) Formulation 5 (Invention) 0.1266 Formulation 7 (Invention) 0.1240 Formulation 4 (Invention) 0.1274 Formulation 6 (Invention) 0.1203 Formulation 3 (comparative) 0.1760 Formulation 8 (comparative) 0.2280 Formulation 9 (comparative) 0.4261 Formulation 10 (comparative) 1.9190

[0217] Thermal conductivity was measured using a Thermtest Hot Disk TPS (Transient Plane Source) 2500S Tester and are quoted in Table 9. Table 9 shows that the example formulations according to the invention (Formulations 4 to 6) have lower thermal conductivity than the comparative materials: formulation 8 (RTV 3040), formulation 9 (ESA 7242), formulation 10 (Sakrete Concrete) and formulation 3 (ESA 7200).

[0218] It is an advantage to have a thermally insulating material. If a battery or multiple batteries in the pack overheat, an insulating material surrounding the battery will help prevent excessive heat from reaching the passenger area of an electric vehicle (car, truck, boat, train, plane, etc.).

[0219] Another advantage of the cured formulations 4 to 7 according to the invention is that they can absorb vibration. Resilience is related to vibration. The more resilient a material is, the more vibration is translated through the material. Using a Shore® Model SRI Resiliometer, commonly referred to as a Bayshore Resiliometer, to quickly and accurately measure the “Rubber Property—Resilience by Vertical Rebound” as described in ASTM D2632. The resilience of example according to the invention and comparative materials were measured and the results are disclosed in Table 9. All the formulations were mixed at 1:1 mix ratio by weight and cured at room temperature overnight for 16 hours. A weight drops on the test sample, and rebounds above the test sample when it hits the sample. When the weight hits the sample and bounces high, it is more resilient. When the weight does not bounce as high, the material is less resilient.

TABLE-US-00008 TABLE 10 resilience measurement of some of the cured products. Cured Resilience sample Number of units Formulation 5 (Invention) 14 Formulation 7 (Invention) 10 Formulation 4 (Invention) 10 Formulation 6 (Invention) 13 Formulation 8 (comparative) 61 Formulation 9 (comparative) 64

[0220] Table 10 shows that the comparative formulation have higher resilience and will translate vibration through the materials more readily whereas cured formulations according to the invention have lower resilience.

[0221] “Tan delta” is an abbreviated form of the terms “Tangent of Delta”. The tan delta quantifies the way in which a material absorbs and disperses energy. It expresses the out-of-phase time relationship between an impact force and the resultant force that is transmitted to the supporting body. The tan delta is also known as the Loss Factor due to this loss of energy from the impact force via conversion to, and dispersal of, a safer form of energy. Thus, the tan delta is ultimately an indication of the effectiveness of a material's damping capabilities. The higher the tan delta, the greater the damping coefficient, the more efficient the material will be in effectively accomplishing energy absorption and dispersal. Tan delta is equal to the ratio of loss modulus over the storage modulus or tan(delta)=G″/G′.

G″=loss modulus and G′=storage modulus. Higher values correlate to a material that dampens more effectively than those with lower values.
Table 11 shows that the examples of the inventive materials dampen better than the comparative material.

TABLE-US-00009 TABLE 11 tan delta measurements of some of the cured products Cured Tan Delta sample Number of units Formulation 5 (Invention) 18.2679 Formulation 7 (Invention) 17.7256 Formulation 4 (Invention) 24.1223 Formulation 6 (Invention) 22.9557 Formulation 9 (comparative) 12.6070 Formulation 10 (comparative) 8.7501

[0222] Tan delta measurements were made using an Anton Parr MCR 302 at 25° C. G″ and G′ were measured as the material cured. The tan delta was calculated from these two values. The cured sample of the silicone syntactic foams prepared from addition curing type organopolysiloxanes compositions according to a preferred embodiment of the invention could be advantageously used as damping material and fulfill the required targeted goal within electric vehicle field which is looking eagerly to a damping control strategy to minimize drivetrain oscillations.

[0223] Flame resistance of 3 cured material according to the invention were measured and are quoted in Table 12. All formulations tested were self-extinguishing.

TABLE-US-00010 TABLE 12 Flame resistance results of some cured material according to the invention. Flame Burn Flame Burn Time Glow Time Time After After 2nd 10 s After 2nd 10 s Cured 10 s Burn Burn Burn Samples seconds seconds seconds Formulation 7 (Invention) 68.0 0.0 0.0 Formulation 4 (Invention) 46.0 0.0 0.0 Formulation 6 (Invention) 48.6 0.0 0.0

IV) Examples Part III

[0224]

TABLE-US-00011 TABLE 13 Formulation 11-Invention Part A Percent by weight Organopolysiloxane A1  84.1263% Catalyst C  0.0337% Hollow glass beads D2  15.8400% Total 100.0000% Part B Percent by weight Organopolysiloxane A1  65.551% Organopolysiloxane B1 (CE)  16.778% Organopolysiloxane B2 (XL)   1.830% Cure rate controller G2    0.001% Hollow glass beads D2  15.840% Total  100.000%

[0225] Formulation 11 (invention) and a comparative formulation 12 (tin catalyzed condensation cured product) are prepared according to the ingredient described respectively in Tables 13 and 14.

TABLE-US-00012 TABLE 14 Formulation 12-Condensation Cured Comparative Formulation 12 Condensation Cured Comparative Formulation 12 Percent by weight *Dimethylsilanol α,ω-endblocked 70.16% polydimethylsiloxane with a viscosity of approximately 3500 mPa-s. Hollow glass beads D2 15.84% Hi Pro Green-Tin based cure catalyst  5.00% with alkoxy silanes for curing silanol functional siloxane-Product is sold by Elkem Silicones USA Corporation in York South Carolina USA Total 91.00%

[0226] Battery packs can have long distances that the insulating material (the liquid precursor, before crosslinking, of the silicone syntactic foam according to the invention) needs to travel from the outside air when filling the pack. The comparative formulation 12 described above needs moisture from the air to cure quickly. The formulation was mixed at 25° C. and allowed to rest at that temperature until it had cured enough for an initial durometer reading could be taken. The condensation curable comparative formulation 12 was also made and allowed to rest in the same fashion as the inventive formulation 11. Both samples were made and then allowed to rest after being poured into an aluminum dish that had material at 1 cm thickness and 5.2 cm in diameter. One 5.2 cm face of the material was exposed to the air and no air (or moisture from the air) could move through the bottom or sides of the aluminum dish. This configuration is representative of what might happen in a typical battery pack. Air with moisture could be present over one face of the potting material for a battery, while much of the material is below that surface relying on moisture to migrate through the bulk of the potting material.

[0227] Regarding inventive formulation 11 it took approximately 12 minutes to be able to measure the durometer of the material on a Shore A range. The durometer was approximately 15 Shore A. At one hour the durometer was 50 Shore A. Similar formulations reached approximately 52-54 Shore A in previous examples. When checking the condensation curable formulation 12, it took until 1 hour and 42 minutes before a durometer measurement could be made, and the value was 11.7 Shore A. When pressing on the sample by hand, and then pulling a second sample (equivalent in a dish) apart, it was found that the bottom half of the sample was still liquid. The test sample was only cured in a layer on the top. This indicates that the condensation cured material requires significantly longer time to cure in a representative test configuration than the inventive formulation. It would be advantageous if the material cures more quickly to speed up production times when potting battery packs.

[0228] Another cure system, a peroxide cure system was tested. However, peroxides typically require heat to cure so this is already a disadvantage. As shown above, the inventive formulation 11 can be made to cure very quickly if that is desired, and no heat or energy to heat is required.

[0229] As below a peroxide comparative formulation 13 is described in Table 15:

TABLE-US-00013 TABLE 15 Formulation 13-Peroxide Cured Comparative Formulation 1:1 Mix Ratio by weigth Part A Percent by weight Hollow glass beads D2  15.84% Organopolysiloxane A2  84.16% Total 100.00% Part B Percent by weight Hollow glass beads D2  15.84% Organopolysiloxane A2  62.54% Organopolysiloxane A3  21.02% DBPH*  0.61% Total 100.01% DBPH* = Varox ® = consist of greater than 90% by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and is sold by R. T. Vanderbilt Organopolysiloxane A3: Poly(methylvinyl)(dimethyl)siloxane with dimethylvinylsilyl end-units with a viscosity at 25° C. = 390 mPa .Math. s;

[0230] Class and Grasso suggest curing silicones with a DBPH catalyst at 177° C. for one hour (reference: Class, J. B.; Grasso, R. P., The Efficiency of Peroxides for Curing Silicone Elastomers, Rubber Chemistry and Technology, September 1993, Vol. 66, No. 4, pp. 605-622). We followed this advice in curing our formulation as well. No post cure was done.

[0231] The same type of container was used to hold the material during cure (aluminum dish, one open face, 5.2 cm in diameter and 1 cm thickness of the poured material). We kept one face open, because when performing potting, it is common to pour into a container and cure the material open to the air. Placing a lid on the container to keep air out would be an extra cost for the lid and extra time to attach the lid in a production setting. When cured for one hour at 177° C., the sample was removed from the oven. The surface facing the air was not cured. This is not an unusual phenomenon, but was tested in these formulations to see if a similar formulation to the inventive formulation would have the issues seen in other peroxide cured silicone formulations. Once the uncured layer was removed, the cured peroxide comparative elastomer formulation 13 had a durometer of 20 Shore A.

[0232] Three ways to eliminate lack of cure at an oxygen containing interface are typically used in the industry: [0233] Removal of oxygen from the cure zone by use of inert gas, by use of waxes that migrate to the surface and form a barrier, or by use of films that are in direct contact with the coating. [0234] Increasing free radical concentration by increasing the peroxide level. [0235] Use chemicals that react with the peroxy radicals.

[0236] All of these solutions to lack of cure may work. However, heating would still be needed for the sample and implementation of the solutions would either require much more complicated formulations which change the cured elastomer (i.e. waxes, chemicals that react with the peroxy radicals, etc.) and more expensive formulations (i.e. more free radical peroxides).