CONDUCTIVE LIQUID SILICONE RUBBER AND PREPARATION METHOD AND USE THEREOF

Abstract

A conductive liquid silicone rubber is described, in which the conductive filler used in the conductive liquid silicone rubber includes single-walled carbon nanotubes. Also described, is the use of single-walled carbon nanotubes as a conductive filler to prepare a single-walled carbon nanotube conductive liquid silicone rubber composite material. A two-step pre-mixing method and formulation design is also described that can effectively disperse the single-walled carbon nanotubes at an extremely small addition amount minimizing problems such as agglomeration, sedimentation and precipitation while reducing viscosity and enhancing processing performance. A resulting conductive liquid silicone rubber can exhibit not only a low conductive filler addition amount and excellent electrical properties, but also excellent physical and mechanical properties and weather resistance, as well reduced pollutant generation during vulcanization.

Claims

1. A conductive liquid silicone rubber, comprising a conductive filler that comprises single-walled carbon nanotubes, wherein the single-walled carbon nanotubes are in the form of a premix and wherein the premix is obtained by pre-mixing the single-walled carbon nanotubes and a polyorganosiloxane.

2. The conductive liquid silicone rubber according to claim 1, wherein the single-walled carbon nanotubes have a diameter of from 1 nm to 50 nm and a length of greater than 5 μm.

3. The conductive liquid silicone rubber according to claim 2, wherein a masterbatch of the conductive liquid silicone rubber is obtained by mixing the premix containing single-walled carbon nanotubes and a base rubber.

4. The conductive liquid silicone rubber according to claim 3, wherein the base rubber comprises a vinyl silicone oil, a silica, a silazane and a deionized water that are thoroughly and uniformly mixed.

5. The conductive liquid silicone rubber according to claim 4, wherein the vinyl silicone oil is a vinyl-terminated silicone oil and/or a polyvinyl silicone oil.

6. The conductive liquid silicone rubber according to claim 3, wherein, in addition to the masterbatch, the raw materials for preparing the liquid silicone rubber further comprise: a Component I, a Component II, a catalyst and an inhibitor; wherein the Component I is one or a mixture of several of the compounds represented by the general Formula (1): ##STR00004## in the general Formula (1), n represents an integer from 0 to 100; m represents an integer from 70 to 4000; R represents a saturated hydrocarbyl; R.sup.1 represents an unsaturated hydrocarbyl; R.sup.2 represents a saturated or unsaturated hydrocarbyl; preferably, the Component I is a vinyl-terminated silicone oil in which R.sup.1 is vinyl and R.sup.2 is a saturated hydrocarbyl, and/or a side chain vinyl silicone oil in which R.sup.1 is a wherein saturated hydrocarbyl and R.sup.2 is vinyl, and/or a vinyl-terminated side chain vinyl silicone oil in which both R.sup.1 and R.sup.2 are vinyl; the Component II is one or a mixture of several of compounds represented by general Formulas (2) and (3): ##STR00005## in the general Formula (2), x represents an integer from 8 to 200; y represents an integer from 0 to 60; R.sup.3 represents methyl, hydrogen or SiH group; R.sup.4 represents methyl, ethyl, propyl or phenyl; ##STR00006## in the general formula (3), a represents an integer of 1 to 300; R.sup.5 represents methyl, ethyl or hydrogen group; optionally, the Component II is a hydrogen-containing silicone oil containing SiH at both ends and side chain in which R.sup.3 is hydrogen group and y is greater than 1, and/or a terminal hydrogen-containing silicone oil in which R.sup.3 is hydrogen and y is 0, and/or a side chain hydrogen-containing silicone oil in which R.sup.3 is a saturated hydrocarbyl and y is greater than 1, and/or a hydrogen-containing silicone resin in which R.sup.5 is hydrogen group; wherein, when the Component II consists of only the compound of the general Formula (2), the two conditions that y=0 and R.sup.3 is methyl do not exist at the same time; when the Component II consists of only the compound of the general Formula (3), R.sup.5 is hydrogen group; when the Component II is one or a mixture of several of the compounds of the general Formulas (2) and (3), at least one of the compounds of the general Formulas (2) and (3) has a SiH bond; the catalyst is a Karstedt catalyst; and wherein the inhibitor is at least one selected from the group consisting of 1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-ol, 3,5-dimethyl-1-hexyn-3-ol and 3-methyl-1-dodecyn-3-ol.

7. The liquid silicone rubber according to claim 6, wherein the raw materials for preparing the liquid silicone rubber comprise: the masterbatch in an amount of 100 parts, the Component I in an amount of from 10 parts to 100 parts, the Component II in an amount of 0.4 to 10 parts, preferably 0.4 to 5 parts, the catalyst in an amount of 0.002 to 0.02 parts, and the inhibitor in an amount of 0.02 to 1 parts; optionally, the Component I is a vinyl-terminated silicone oil, a side-chain vinyl silicone oil, and/or a vinyl-terminated side-chain vinyl silicone oil; the Component II is a hydrogen-containing silicone oil containing SiH at both ends and side chains and/or a terminal hydrogen-containing silicone oil.

8. A preparation method for the conductive liquid silicone rubber according claim 1, the method comprising the following steps: pre-mixing single-walled carbon nanotubes and a polyorganosiloxane to obtain a premix; mixing the premix and a base rubber to prepare a masterbatch, and then mixing the masterbatch with other raw materials and vulcanizing it to prepare a conductive liquid silicone rubber optionally, the other raw materials include: a Component I, a Component II, a catalyst and an inhibitor.

9. The method according to claim 8, the method further-comprising the following steps: uniformly mixing the masterbatch containing single-walled carbon nanotubes, a catalyst and at least one Component I, and vacuum degassing to obtain a Component A; uniformly mixing the masterbatch containing single-walled carbon nanotubes, at least one Component I, at least one Component II and at least one inhibitor, and vacuum degassing to obtain Component B; uniformly mixing the Component A and the Component B in equal proportion, subjected to curing to obtain a test piece, and vulcanizing to obtain the conductive liquid silicone rubber; optionally, the method comprises the following steps: (1) Preparation of premix: premixing the single-walled carbon nanotubes and the polyorganosiloxane to obtain the premix, wherein the single-walled carbon nanotubes constitute 5% to 20% percentage by mass of the premix; (2) Preparation of base rubber: taking a methyl vinyl silicone oil, a silica, a silazane and a deionized water, thoroughly mixing at 60° C. to 90° C. under the protection of inert atmosphere, then heated to 130° C. to 180° C. and starting vacuuming, kept at temperature at 130° C. to 180° C. during the vacuuming, cooled to 120° C. to 140° C. after the completion of the vacuuming, adding a methyl vinyl silicone oil for dilution, stirred until homogeneous to obtain the base rubber; (3) Preparation of masterbatch: thoroughly mixing the premix containing single-walled carbon nanotubes and the base rubber on a three-roll mill to obtain the masterbatch; (4) Preparation and vulcanization of Components A and B: uniformly mixing the masterbatch, the catalyst and at least one Component I, vacuum degassing to obtain a Component A; uniformly mixing the masterbatch, at least one Component I, at least one Component II and at least one inhibitor, vacuum degassing to obtain a Component B; uniformly mixing the Component A and the Component B in equal proportion, subjected to curing to obtain a test piece, and vulcanizing to obtain the conductive liquid silicone rubber.

10. A method of manufacturing a power grid accessory or electric cable accessory, the method comprising making the accessory with the conductive liquid silicone rubber according to claim 1.

11. The conductive liquid silicone rubber according to claim 1, wherein the single-walled carbon nanotubes are present in an amount of from 0.1% to 10% of the total mass of the liquid silicone rubber.

12. The conductive liquid silicone rubber according to claim 1, wherein the single-walled carbon nanotubes constitute from 5% to 20% by mass of the premix.

13. The conductive liquid silicone rubber according to claim 2, wherein the single-walled carbon nanotubes have a diameter of 1.2 nm to 2 nm and a length of greater than 10 μm.

14. The conductive liquid silicone rubber according to claim 3, wherein the premix and base rubber are mixed at a mass ratio of (1 to 10):100.

15. The conductive liquid silicone rubber according to claim 14, wherein the ratio is (3.8 to 10):100.

16. The conductive liquid silicone rubber according to claim 3, wherein the masterbatch is prepared by a process comprising the steps: thoroughly mixing the premix and the base rubber on a three-roll mill to obtain masterbatch.

17. The conductive liquid silicone rubber according to claim 16, wherein the mixing is conducted until the resulting mixture has a particle size of from 0.1 μm to 20 μm.

18. The conductive liquid silicone rubber according to claim 4, wherein the base rubber comprises from 30 to 70 parts of the vinyl silicone oil, from 15 to 40 parts of the silica, from 5 to 15 parts of the silazane and from 1 to 10 parts of the deionized water.

19. The conductive liquid silicone rubber according to claim 4, wherein the base rubber is prepared by a process comprising the steps: taking a methyl vinyl silicone oil, a silica, a silazane and a deionized water, thoroughly mixing at 60° C. to 90° C. under the protection of an inert atmosphere, then increasing the temperature of 130° C. to 180° C. and vacuuming for 2 to 4 hours, kept at the temperature of 130° C. to 180° C. during the vacuuming, cooled to a temperature of 120° C. to 140° C. after the vacuuming, then adding a methyl vinyl silicone oil for dilution, and stirred until homogeneous to obtain the base rubber.

20. The conductive liquid silicone rubber according to claim 5, wherein the vinyl-terminated silicone oil is an alkyl vinyl silicone oil.

21. The conductive liquid silicone rubber according to claim 20, wherein the alkyl vinyl silicone oil is a methyl vinyl silicone oil.

22. The conductive liquid silicone rubber according to claim 5, wherein the silica is a fumed silica that has been grafted in situ with a treating agent such as a silazane and has a specific surface area of not less than 200 m.sup.2/g.

23. The conductive liquid silicone rubber according to claim 22, wherein the treating agent is a silazane.

24. The conductive liquid silicone rubber according to claim 5, wherein the silica has a specific surface area of from 280 m.sup.2/g to 320 m.sup.2/g.

25. The conductive liquid silicone rubber according to claim 23, wherein the silazane is at least one or a mixture of two members selected from the group consisting of hexamethylsilazane, tetramethyldivinylsilazane, heptamethyldisilazane and vinyl-mono-terminated silazane, combinations thereof and the like.

26. The conductive liquid silicone rubber according to claim 25, wherein the hexamethylsilazane and/or tetramethyldivinylsilazane.

27. The conductive liquid silicone rubber according to claim 7, wherein the Component I is present in an amount of from 10 parts to 65 parts.

28. The conductive liquid silicone rubber according to claim 27, wherein the Component I is present in an amount of from 10 parts to 35 parts.

29. The conductive liquid silicone rubber according to claim 7, wherein the Component II is present in an amount of from 0.4 parts to 5 parts.

30. The conductive liquid silicone rubber according to claim 7, wherein the catalyst is present in an amount of from 0.003 parts to 0.01 parts.

31. The conductive liquid silicone rubber according to claim 7, wherein the inhibitor is present in an amount of from 0.02 parts to 0.5 parts.

32. The method according to claim 8, wherein the single-walled carbon nanotubes constitute from 5% to 20% by mass of the premix.

33. The conductive liquid silicone rubber according to claim 8, wherein the mass ratio of the premix and the base rubber in the masterbatch is from (1 to 100): 100.

34. The conductive liquid silicone rubber according to claim 33, wherein the ratio is (3.8 to 10):100.

35. The conductive liquid silicone rubber according to claim 9, wherein the curing is carried out at a temperature of 130° C. to 170° C.; and/or, and the vulcanization is carried out at a temperature of 180° C. to 220° C.

36. A method of manufacturing a power grid accessory or electric cable accessory, the method comprising manufacturing the accessory using a conductive liquid silicone rubber prepared by the method of claim 8.

Description

SPECIFIC MODELS FOR CARRYING OUT THE INVENTION

[0045] The technical solution of the present invention will be further fully described in detail in conjunction with the examples below.

[0046] The single-walled carbon nanotubes used in the following examples were commercially available and had a diameter of about 1.5 nm (in the range of 1.2 nm to 2 nm) and a length of 12 μm.

Preparation of Liquid Conductive Silicone Rubber

Example 1

[0047] In this example, a single-walled carbon nanotube conductive liquid silicone rubber was provided, which was prepared by the following method:

[0048] (1) Preparation of premix: the single-walled carbon nanotubes and polyorganosiloxane were pre-mixed to obtain a premix, wherein the single-walled carbon nanotubes constitute 10% percentage by mass of the premix.

[0049] (2) Preparation of base rubber: in a kneader or planetary mixer, 42 parts by weight of methyl vinyl silicone oil with a viscosity of 60000 mPa.Math.s, 26 parts of fumed silica with a BET specific surface area of 300 m.sup.2/g and 7 parts of hexamethyldisilazane, 0.05 parts of tetramethyldivinylsilazane and 3.5 parts of deionized water were thoroughly mixed for 1.5 hours under the protection of an inert atmosphere at a temperature below 80° C., then heated to 140° C. and subjected to vacuuming for 3 hours, kept at a temperature of 160° C. during vacuuming, then cooled to 125° C., added with 21.5 parts of methyl vinyl silicone oil with a viscosity of 60,000 mPa.Math.s, and stirred until homogeneous to obtain base rubber No. 1 of liquid silicone rubber.

[0050] (3) Preparation of masterbatch: 3.8 parts of the premix obtained in step (1) and 100 parts of the base rubber 1 were mixed 10 times on a three-roll mill (the mixture has particle size of 0.1 to 20 microns) to prepare masterbatch No. 1 of conductive liquid silicone rubber;

[0051] (4) Preparation and vulcanization of Components A and B: 100 parts of the above-mentioned masterbatch 1, 18 parts of vinyl-terminated silicone oil with a viscosity of 20000 mPa.Math.s, 5 parts of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 0.02 parts of Karstedt catalyst were stirred and dispersed in a planetary mixer for 35 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component A No. 1 of conductive liquid silicone rubber. 100 parts of the above-mentioned masterbatch 1, 20 parts of vinyl-terminated silicone oil with a viscosity of 20000 mPa.Math.s, 3 parts of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 1.5 parts of hydrogen-containing silicone oil containing SiH at both ends and side chains with a hydrogen content of 0.7%, 1.5 parts of terminal hydrogen-containing silicone oil with a hydrogen content of 0.2%, and 0.1 parts of 3-methyl-1-dodecyn-3-ol were stirred and dispersed in a planetary mixer for 35 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component B No. 1 of conductive liquid silicone rubber. The Component A No. 1 at equal proportion and the Component B No. 1 at equal proportion were uniformly mixed, then cured at 150° C. for 10 minutes to obtain a 2 mm test piece, and the test piece was secondly vulcanized at 200° C. for 4 hours to obtain single-walled carbon nanotube conductive liquid silicone rubber.

Example 2

[0052] In this example, a single-walled carbon nanotube conductive liquid silicone rubber was provided, which was prepared by the following method:

[0053] (1) Preparation of premix: the same as Example 1;

[0054] (2) Preparation of base rubber: in a kneader or planetary mixer, 40 parts by weight of methyl vinyl silicone oil with a viscosity of 60000 mPa.Math.s, 25 parts of fumed silica with a BET specific surface area of 300 m.sup.2/g, 7 parts of hexamethyldisilazane, 0.1 parts of tetramethyldivinylsilazane and 4 parts of deionized water were thoroughly mixed for 1.5 hours under the protection of an inert atmosphere at a temperature of below 80° C., then heated to 140° C. and subjected to vacuuming for 3 hours, kept at a temperature of 160° C. during vacuuming, then cooled to 125° C., added with 23.9 parts of methyl vinyl silicone oil with a viscosity of 60,000 mPa.Math.s, and stirred until homogeneous to obtain base rubber No. 2 of liquid silicone rubber.

[0055] (3) Preparation of masterbatch: 5 parts of the premix obtained in step (1) and 100 parts of the base rubber 2 were mixed 5 times on a three-roll mill (the mixture has particle size of 0.1 to 20 microns) to prepare masterbatch No. 2 of conductive liquid silicone rubber;

[0056] (4) Preparation and vulcanization of Components A and B: 100 parts of the above-mentioned masterbatch 2, 10 parts of vinyl-terminated silicone oil with a viscosity of 3500 mPa.Math.s, 3 parts of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 0.02 parts of Karstedt catalyst were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component A No. 2 of conductive liquid silicone rubber. 100 parts of the above-mentioned masterbatch 2, 7 parts of vinyl-terminated silicone oil with a viscosity of 3500 mPa.Math.s, 1 part of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 3 parts of hydrogen-containing silicone oil containing SiH at both ends and side chains with a hydrogen content of 0.7%, 0.1 parts of 3-methyl-1-dodecyn-3-ol were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component B No. 2 of conductive liquid silicone rubber. The Component A No. 2 at equal proportion and the Component B No. 2 at equal proportion were uniformly mixed, then cured at 150° C. for 10 minutes to obtain a 2 mm test piece, and the test piece was secondly vulcanized at 200° C. for 4 hours to obtain single-walled carbon nanotube conductive liquid silicone rubber.

Example 3

[0057] In this example, a single-walled carbon nanotube conductive liquid silicone rubber was provided, which was prepared by the following method:

[0058] (1) Preparation of premix: the same as Example 1;

[0059] (2) Preparation of base rubber: in a kneader or planetary mixer, 38 parts by weight of methyl vinyl silicone oil with a viscosity of 100,000 mPa.Math.s, 7 parts of methyl vinyl silicone oil with a viscosity of 60,000 mPa.Math.s, 25 parts of fumed silica with a BET specific surface area of 300 m.sup.2/g, 7 parts of hexamethyldisilazane, 0.15 parts of tetramethyldivinylsilazane and 6 parts of deionized water were thoroughly mixed for 1.5 hours under the protection of an inert atmosphere at a temperature of below 80° C., then heated to 140° C. and subjected to vacuuming for 3 hours, kept at a temperature of 160° C. during vacuuming, then cooled to 125° C., added with 16.8 parts of methyl vinyl silicone oil with a viscosity of 20,000 mPa.Math.s, and stirred until homogeneous to obtain base rubber No. 3 of liquid silicone rubber.

[0060] (3) Preparation of masterbatch: 4 parts of the premix obtained in step (1) and 100 parts of the base rubber 3 were mixed 10 times on a three-roll mill (the mixture has particle size of 0.1 to 20 microns) to prepare masterbatch No. 3 of conductive liquid silicone rubber;

[0061] (4) Preparation and vulcanization of Components A and B: 100 parts of the above-mentioned masterbatch 3, 11 parts of vinyl-terminated silicone oil with a viscosity of 100,000 mPa.Math.s, 3.5 parts of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 0.015 parts of Karstedt catalyst were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component A No. 1 of conductive liquid silicone rubber. 100 parts of the above-mentioned masterbatch 3, 12 parts of vinyl-terminated silicone oil with a viscosity of 100,000 mPa.Math.s, 1.7 parts of hydrogen-containing silicone oil containing SiH at both ends and side chains with a hydrogen content of 0.7%, 0.5 parts of hydrogen-containing silicone oil containing SiH at both ends, 0.08 parts of 1-ethynyl-1-cyclohexanol were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component B No. 3 of conductive liquid silicone rubber. The Component A No. 3 at equal proportion and the Component B No. 3 at equal proportion were uniformly mixed, then cured at 150° C. for 10 minutes to obtain a 2 mm test piece, and the test piece was secondly vulcanized at 200° C. for 4 hours to obtain single-walled carbon nanotube conductive liquid silicone rubber.

Example 4

[0062] In this example, a single-walled carbon nanotube conductive liquid silicone rubber was provided, which was prepared by the following method:

[0063] (1) Preparation of premix: the same as Example 1;

[0064] (2) Preparation of base rubber: the same as Example 3;

[0065] (3) Preparation of masterbatch: 3.5 parts of the premix obtained in step (1) and 100 parts of the base rubber 3 were mixed 10 to 20 times in a three-roll mill (the mixture has particle size of 0.1 to 20 microns) to prepare masterbatch No. 4 of conductive liquid silicone rubber;

[0066] (4) Preparation and vulcanization of Components A and B: 100 parts of the above-mentioned masterbatch 4, 20 parts of vinyl-terminated silicone oil with a viscosity of 20,000 mPa.Math.s, 2 parts of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 0.025 parts of Karstedt catalyst were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component A No. 4 of conductive liquid silicone rubber. 100 parts of the above-mentioned masterbatch 4, 15 parts of vinyl-terminated silicone oil with a viscosity of 20,000 mPa.Math.s, 1 part of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 1 part of hydrogen-containing silicone oil containing SiH at both ends and side chains with a hydrogen content of 0.7%, 0.13 parts of 3-methyl-1-dodecyn-3-ol were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component B No. 4 of conductive liquid silicone rubber. The Component A No. 4 at equal proportion and the Component B No. 4 at equal proportion were uniformly mixed, then cured at 150° C. for 10 minutes to obtain a 2 mm test piece, and the test piece was secondly vulcanized at 200° C. for 4 hours to obtain single-walled carbon nanotube conductive liquid silicone rubber.

Example 5

[0067] In this example, a single-walled carbon nanotube conductive liquid silicone rubber was provided, which was prepared by the following method:

[0068] (1) Preparation of premix: the same as Example 1;

[0069] (2) Preparation of base rubber: in a kneader or planetary mixer, 40 parts by weight of methyl vinyl silicone oil with a viscosity of 60,000 mPa.Math.s, 2.5 parts of polyvinyl silicone oil with a viscosity of 20,0000 mPa.Math.s, 27.5 parts of fumed silica with a BET specific surface area of 300 m.sup.2/g, 8 parts of hexamethyldisilazane, 0.7 parts of tetramethyldivinylsilazane and 4.5 parts of deionized water were thoroughly mixed for 1.5 hours under the protection of an inert atmosphere at a temperature of below 80° C., then heated to 140° C. and subjected to vacuuming for 3 hours, kept at a temperature of 160° C. during vacuuming, then cooled to 125° C., added with 16.8 parts of methyl vinyl silicone oil with a viscosity of 60,000 mPa.Math.s, and stirred until homogeneous to obtain base rubber No. 5 of liquid silicone rubber.

[0070] (3) Preparation of masterbatch: 6 parts of the premix obtained in step (1) and 100 parts of the base rubber 5 were mixed 20 times on a three-roll mill (the mixture has particle size of 0.1 to 20 microns) to prepare masterbatch No. 5 of conductive liquid silicone rubber;

[0071] (4) Preparation and vulcanization of Components A and B: 100 parts of the above-mentioned masterbatch 5, 15 parts of vinyl-terminated silicone oil with a viscosity of 20,000 mPa.Math.s, 6 parts of vinyl-terminated side-chain vinyl silicone oil with a vinyl mass content of 2.36%, 0.018 parts of Karstedt catalyst were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component A No. 5 of conductive liquid silicone rubber. 100 parts of the above-mentioned masterbatch 5, 14.5 parts of vinyl-terminated silicone oil with a viscosity of 100,000 mPa.Math.s, 6.5 parts of hydrogen-containing silicone oil containing SiH at both ends and side chains with a hydrogen content of 0.7%, 0.13 parts of 3-methyl-1-dodecyn-3-ol were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component B No. 5 of conductive liquid silicone rubber. The Component A No. 5 at equal proportion and the Component B No. 5 at equal proportion were uniformly mixed, then cured at 150° C. for 10 minutes to obtain a 2 mm test piece, and the test piece was secondly vulcanized at 200° C. for 4 hours to obtain single-walled carbon nanotube conductive liquid silicone rubber.

Example 6

[0072] In this example, a single-walled carbon nanotube conductive liquid silicone rubber was provided. Compared with Example 4, the only difference was that: when preparing the masterbatch, mixing on a three-roll mill was replaced by the way of mixing with a planetary mixer;

[0073] The specific steps were:

[0074] (1) Preparation of premix: the same as Example 1;

[0075] (2) Preparation of base rubber: the same as Example 3;

[0076] (3) Preparation of masterbatch: 3.5 parts of the premix obtained in step (1) and 100 parts of the base rubber 3 were placed into a planetary mixer and dispersed at a rotation speed of 1200 r/min for 30 min to prepare masterbatch No. 7 of conductive liquid silicone rubber;

[0077] (4) Preparation and vulcanization of Components A and B: 100 parts of the above-mentioned masterbatch 7, 20 parts of vinyl-terminated silicone oil with a viscosity of 20,000 mPa.Math.s, 2 parts of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 0.025 parts of Karstedt catalyst were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component A No. 7 of conductive liquid silicone rubber. 100 parts of the above-mentioned masterbatch 7, 15 parts of vinyl-terminated silicone oil with a viscosity of 20,000 mPa.Math.s, 1 part of side-chain vinyl silicone oil with a viscosity of 1000 mPa.Math.s, 1 part of hydrogen-containing silicone oil containing SiH at both ends and side chains with a hydrogen content of 0.7%, 0.13 parts of 3-methyl-1-dodecyn-3-ol were stirred and dispersed in a planetary mixer for 30 to 40 minutes, mixed until homogeneous and then degassed by vacuuming to obtain Component B No. 7 of conductive liquid silicone rubber. The Component A No. 7 at equal proportion and the Component B No. 7 at equal proportion were uniformly mixed, then cured at 150° C. for 10 minutes to obtain a 2 mm test piece, and the test piece was secondly vulcanized at 200° C. for 4 hours to obtain single-walled carbon nanotube conductive liquid silicone rubber.

Comparative Example 1

[0078] During the preparation process, the mixture of single-walled carbon nanotubes and polyorganosiloxane was not added, and the remaining raw materials and operation steps were completely the same as in Example 1.

Comparative Example 2

[0079] A single-walled carbon nanotube conductive liquid silicone rubber was provided. Compared with Example 1, the only difference was that: single-walled carbon nanotubes were used to replace the premix of single-walled carbon nanotubes and polyorganosiloxane, i.e. single-walled carbon nanotubes were directly mixed with base rubber to prepare the masterbatch.

Comparative Example 3

[0080] A single-walled carbon nanotube conductive liquid silicone rubber was provided. Compared with Example 1, the only difference was that: a premix of polyorganosiloxane and single-walled carbon nanotubes was not prepared, and a masterbatch was not prepared by mixing a premix and a base rubber, instead, directly mixing untreated single-walled carbon nanotubes with Components A and B.

Comparative Example 4

[0081] A single-walled carbon nanotube conductive liquid silicone rubber was provided. Compared with Example 1, the only difference was that after a premix of single-walled carbon nanotubes was prepared, the premix was not mixed with a base rubber to prepare a masterbatch, instead, the premix was directly mixed with Components A and B.

Detection of Liquid Conductive Silicone Rubber

[0082] The conductive liquid silicone rubbers provided by Examples 1 to 7 were detected for their performance.

[0083] The detection method for volume resistance and calculation of volume resistivity adopted GB/T2439-2001; the detection method for tensile strength and elongation at break adopted ASTM D412-1998a(2002)e1; the detection method for hardness adopted ASTM D2240; the detection method for tearing strength adopted ASTM D624; the detection method for resilience rate adopted ASTM D7121-2005 (2012).

[0084] The detection results were shown in Table 1.

TABLE-US-00001 TABLE 1 Performances of product test pieces of conductive liquid silicone rubbers Tensile Elongation Tearing Volume Viscosity Hardness strength at break Resilience strength resistivity (Pa.s) Performance (Shore A) (MPa) (%) rate (%) (kN/m) Ω .Math. cm (@10-1) Example 1 42 8.6 688 46 31 58 235 Example 2 45 8.4 710 48 25 40 220 Example 3 43 9.0 842 44 24 60 310 Example 4 28 7.8 933 36 25 150 310 Example 5 65 8.8 520 52 45 28 290 Example 6 30 6.7 940 31 27 59 295 Comparative 31 9.1 670 50 27 >1.00E+15 168 Example 1 Comparative 47 5.6 513 49 30 −*a 271 Example 2 Comparative 43 5.58 468 49 29.35 −*b 236 Example 3 Comparative 37 4.6 470 50 26.6 36806 223 Example 4 .sup.*a A non-uniform product piece has resulted in a large deviation of the measurement; .sup.*b A non-uniform product piece has resulted in a large deviation of the measurement.

[0085] As can be seen from the results in Table 1, by using the two-step pre-mixing method involving preparing a premix and mixing the premix with a base rubber to obtain a masterbatch, effectively dispersing the single-walled carbon nanotubes in an extremely small amount of addition in the whole system was achieved, and the resulting liquid silicone rubber not only had good electrical conductivity, but also had excellent mechanical properties, including electrical conductivity, tensile strength, elongation at break, etc. On the contrary, the pre-mixing method without the above two steps could not give meaningful measurement results for volume resistivity (as shown in Comparative Example 3), and when the step of mixing single-walled carbon nanotubes with polyorganosiloxane to prepare a premix was not employed, meaningful measurement results of volume resistivity could not be obtained as well (as shown in Comparative Example 2). Even if a premix of single-walled carbon nanotubes and polyorganosiloxane was used, if the step of mixing the premix with a base rubber to prepare a masterbatch was not adopted, the resulted volume resistivity could not meet the application requirements of power grid accessories or electric cable accessories (as shown in Comparative Example 4).

[0086] The conductive liquid silicone rubber provided by the present invention had good electrical conductivity and excellent mechanical strength, and at the same time had the characteristics of low viscosity, good fluidity and easiness of injection molding. By increasing the addition proportion of the premix of single-walled carbon nanotubes within a certain range, the electrical conductivity of the product could be enhanced with less effect on mechanical properties, and the product could fully meet the application requirements for power industry. On the contrary, when the same proportion of single-walled carbon nanotube powder filler was directly added, the carbon nanotubes could not be uniformly dispersed, and the resultant product has shown inhomogeneous appearance and poor tensile properties. By using the way of adding premix, on the one hand, the process was environmentally friendly and clean, on the other hand, the nanotubes were uniformly dispersed, and the product showed excellent mechanical properties and good electrical properties.

[0087] Although the general description, specific embodiments and tests have been used to describe the present invention in detail above, some modifications or improvements can be made on the basis of the present invention, which is obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall into the scope of the present invention.