Electret stability related to the crystallinity in polypropylene

Through mixing isotactic-polypropylene (i-PP) and atactic-polypropylene (a-PP), we have demonstrated the importance of the crystallinity in polypropylene as an electret material. A high degree of crystallinity in polypropylene, used as an electret, gives a better charge stability towards temperature and humidity changes. The semicrystalline i-PP significantly outperforms a-PP regarding charge stability. a-PP is an amorphous polymer. By mixing a-PP and i-PP the degree of crystallinity can be controlled, while all other sample preparation processes and characteristics can be identical. This is important since the performance of an electret material is sensitive to its previous process history.