STUDIES ON THE APPLICATION OF BMC IN ELEC TRIC APPLIANCES .2. EFFECTIVENESS OF ELECTRIC INSULATION FOR BMC (BULK MOLDING COMPOUNDS) FILLED WITH ALUMINUM TRIHYDRATE

The effectiveness of electric insulation of BMC, filled with 30 wt% Al (OH)3 or not so filled, was investigated. The following results were o btained. (1) Only small differences of the increasing rates in weight of BMC filled with 30 wt% Al(OH)3 and of unfilled BMC were found with the test of absorbing moisture. But the differences of the volume resi stivities or of the dielectric breakdown voltage for the two materials were large. The volume resistivity of BMC filled with 30 wt% Al(OH)3 was reduced 21%, while that of unfilled BMC was only reduced 7%. The d ielectric breakdown voltage of BMC filled with 30 wt% Al(OH)3 was redu ced 55% when that of unfilled BMC was not much changed. (2) The effect iveness of electric insulation for BMC filled with 30 wt% Al(OH)3 was dependent on the decomposition temperature of Al(OH)3. Only small diff erences of electric insulation for BMC filled with 30 wt% Al(OH)3 and unfilled BMC were found during the the heating test at 100 approximate ly 180-degrees-C. But the differences of the decreasing rates in weigh t or of the dielectric breakdown voltage for the two materials were la rge when the heating test was performed at 200-degrees-C. The decreasi ng rates in weight of BMC filled with 30 wt% Al(OH)3 were reduced 11% when that of unfilled BMC was only reduced 2.5%. The dielectric breakd own voltage of BMC filled with 30 wt% Al(OH)3 were reduced 75%, while that of unfilled BMC was reduced 50% during the heating test at 200-de grees-C.