Foamed polypropylene with orientation holes for piezoelectric material and preparation method of formed polypropylene

The invention discloses foamed polypropylene with orientation holes for a piezoelectric material and a preparation method of the formed polypropylene. The preparation method comprises the following steps: melting polypropylene and then uniformly mixing the melted polypropylene with supercritical fluid to obtain a uniformly-mixed melt, wherein the mass ratio of the polypropylene to the supercritical fluid is 1 to (0.005 to 0.05); injecting the uniformly-mixed melt into a die of which an inner cavity is filled with supercritical carbon dioxide, wherein the pressure of the die inner cavity is 8 to 30 Mpa; injecting the uniformly-mixed melt and then holding the die at the 80 to 140 DEG C for 2 to 120 minutes, raising the temperature to 150 to 170 DEG C, keeping for 30 to 240 minutes and foaming; subsequently, relieving the pressure, cooling and setting to obtain the foamed polypropylene with the orientation holes for the piezoelectric material. A foaming material with high orientation degree can be prepared by ad