Linear polypropylene specimen and foam and process of preparing the same

The present disclosure provides a process of preparing linear polypropylene foam, comprising the following steps: (a) preparing a specimen comprising at least one linear polypropylene; and at least one nucleating agent selected from the group consisting of alpha nucleating agents and beta nucleating agents; (b) deforming the specimen under a deforming pressure and at a deforming temperature for a period of time; and (c) subjecting the deformed specimen obtained in the step (b) to a foaming process to obtain the linear polypropylene foam. The present disclosure further provides a specimen after PIF treatment and a linear polypropylene foam prepared by the above process.