| 摘要 |
A method for preparing a non-crosslinked polypropylene foamed sheet is provided to improve heat resistance, cold resistance, dimension stability, impact absorption, stiffness and chemical resistance, to reduce water absorption and to allow foaming ratio to be controlled. A method for preparing a non-crosslinked polypropylene foamed sheet comprises the steps of mixing 93-98 parts by weight of a polypropylene homopolymer pellet and 0-3 parts by weight of talc as a nucleating agent and melting the mixture at 180-250 deg.C with moving it to the screw of a tandem extruder; changing the temperature of the molten mixture from 170 deg.C to 230 deg.C and from 230 deg.C to 180 deg.C; maintaining the pressure inside an extruder cylinder to be 20-30 kg/cm^2 and injecting 1-4 parts by weight of a butane gas foaming agent; and changing the temperature from 180 deg.C to 150 deg.C and the pressure from 90 kg/cm^2 to 120 kg/cm^2 to allow the mixed mixture to be transferred smoothly to a die.
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