Dielectric material and manufacturing method thereof

A method for manufacturing a dielectric material, comprising,

• subjecting a foamed sphere obtained by a primary foaming to a second foaming in a second molding chamber filled with CO2 at a second temperature of 20° C. below Tm to 5° C. below the Tm and under a second pressure of 15-20 MPa for 30-3600 min to obtain the dielectric material,
• wherein the primary foaming comprises steps of:
• foaming a foaming material sphere with a diameter of 20-800 mm in a first molding chamber filled with CO2 at a first temperature of 80° C. below the Tm to 20° C. below the Tm and under a first pressure of 15-20 MPa to obtain the foamed sphere, and
• the Tm refers to a melting point of a foaming material of the foaming material sphere under normal pressure, and
• wherein a foaming time for the primary foaming meets the following formula:
• t
• ≥
• a
• ×
• (
• d
• /
• 2
• )
• 1.75
• ;
• in which,
• t is the foaming time for the primary foaming, expressed in hour(s);
• a=0.07762 hours/mm1.75;
• and
• d is the diameter of the foaming material sphere, expressed in mm.