Silicone rubber with ATH filler
View Patent ↗The present disclosure relates to a filled silicone rubber material 2 including at least 20 wt % of alumina tri-hydrate as a filler 4 dispersed in SiR 5 to below the percolation threshold. The ATH is a mixture of a first ATH powder and a second ATH powder. The particle size distribution of the first and second ATH powders are such that the d 90 value of the second ATH powder is less than the d 10 value of the first ATH powder. The disclosure also relates to an insulator 1 made from the filled SiR material 2 , and to a use of the insulator in a high-voltage direct current application.
1. An electrical insulator made from a filled silicone rubber, SiR, material comprising 20-50 wt % of alumina tri-hydrate, ATH, as a filler dispersed in SiR to below the percolation threshold, wherein the ATH is a mixture of a first ATH powder and a second ATH powder, the particle size distribution of the first ATH powder and the second ATH powder being such that the d 90 value of the second ATH powder is less than the d 10 value of the first ATH powder.
2. The insulator of claim 1 , wherein the first ATH powder or the second ATH powder has an average particle size, d 50 , within a range of at least one of 1-3 nm or 1.3-2.3 nm, and/or a d 10 value within at least a range of 0.3-1 nm or 0.6-0.9 nm, and/or a d 90 value within at least a range of 2-7 nm or 2.2-5.2 nm.
3. The insulator of claim 1 , wherein the first ATH powder has an average particle size, d 50 , within the range of at least one of 5-15 nm, 6-12 nm, or 8-10 nm.
4. The insulator of claim 1 , wherein the second ATH powder has an average particle size, d 50 , within the range of at least one of 5-200 nm, 10-100 nm, 5-20 nm, 40-60 nm, 80-120 nm or 90-110 nm.
5. The insulator of claim 1 , wherein one or both of the first ATH powder and the second ATH powder have been treated to have a hydrophobic surface.
6. The insulator of claim 5 , wherein the hydrophobic surface is by means of silane.
7. The insulator of claim 1 , wherein the SiR material includes at least at least 30 wt % ATH.
8. The insulator of claim 1 , wherein the first ATH powder constitutes 50-90 wt % of the ATH mixture, and wherein the second ATH powder constitutes 10-50 wt % of said ATH mixture.
9. The insulator of claim 1 , wherein the insulator is a high-voltage, HV, electrical insulator.
10. The insulator of claim 9 configured to operate at a voltage within the range of 0.1-10 kV/mm.
11. The insulator of claim 9 configured to encapsulate at least one power electronic device.
12. The insulator of claim 9 , wherein the insulator is used in a high-voltage direct current, HVDC, application.
13. The insulator of claim 12 , wherein the insulator is included in a wall bushing, a transformer bushing, a cable termination, a support insulator, a cable joint or a surge arrestor.
14. A method for preparing an electrical insulator of a filled SiR material, the method comprising:
providing a first ATH powder;
providing a second ATH powder;
dispersing the first and second ATH powders in SiR to 20-50 wt % and below the percolation threshold of the electrically insulating filled SiR material thus formed;
wherein the particle size distribution of the first ATH powder and the second ATH powder are such that the d 90 value of the second ATH powder is less than the d 10 value of the first ATH powder.
15. The method of claim 14 , further comprising:
treating at least one of the first and second ATH powders to obtain a hydrophobic surface, before the dispersing.
16. The insulator of claim 10 configured to encapsulate at least one power electronic device.