i) Mechanical strength: Mechanical strength depends on temperature and humidity. a) Temperature: High temperature badly affects the mechanical strength of insulating material. While selecting material precautions should be taken that it should withstand high temperature. b) Humidity: Non-hygroscopic materials should be selected, humidity badly affects mechanical strength.
ii) Viscosity: Viscosity is important in liquid dielectrics used in varnishes for impregnation. Low viscosity liquids are more mobile and helpful in transmission of heat by circulation. iii) Porosity: High porosity insulating materials will increase the moisture holding capacity, which is harmful for insulating material, hence porosity is undesired.
iv) Solubility: In some cases, the insulation can be applied only after dissolving, it in some solvent.
v) Mouldability: In manufacturing solid insulating material should have property of easy moulding and machined into required shape and size.