A.C. breakdown properties of ice-alcohol mixed system

We have studied the use of ice as electrical insulating material at cryogenic temperature. Ice has excellent electrical breakdown strength. In addition, ice is environment-friendly material and easy to be molded into various shape because it is liquid at room temperature. However, ice has the following problems as electrical insulating material; the mechanical strength is weak, voids or cracks are easily formed. We consider that these problems can be solved by combination of ice and natural fiber. Our laboratory reported the A.C. electrical breakdown strengths of bamboo-ice and kenaf pulp-ice composite systems are almost the same with that of GFRP. In this paper we tried to improve the A.C. breakdown strength of ice itself by mixture of water-soluble material. We chose alcohol as water soluble material; namely ethanol, 1-propanol, 2-propanol, propylene glycol and glycerin. We examined the A.C. breakdown strength of ice-alcohol mixed system at 77K. As the results, the A.C. breakdown strength of ice-2-propanol mixed system shows the highest, 64% higher value than ice itself.