Title :
Development of porous polypropylene blends with NA11 particles and glass hollow spheres by biaxial stretching for electret applications
Author :
Behrendt, Nico ; Altstädt, Volker ; Schmidt, Hans-W ; Zhang, Xiaoqing ; Sessler, Gerhard M.
Author_Institution :
Polymer Eng., Bayreuth Univ.
Abstract :
In the present work, the development of cellular films by stretching isotactic polypropylene (i-PP) filled with NA11 (2,2´-methylene-bis-(4,6-di-tert-butylphenyl)-phosphate) particles and hollow glass spheres is reported. Morphology, electret properties and piezoelectric activity are investigated. An enhancement of the charge storage stability for the cellular films is due to the formation of cavities, which retard the drift of charges through the volume of the film. Furthermore, the cellular stretched i-PP films with hollow glass spheres were made piezoelectric by suitable corona poling method. Films were stretched to draw ratios of 3.5:3.5 (medium stretched) and selected samples were drawn to ratios of 5:5 (highly stretched). The applied draw ratio was found to directly influence the cavity formations and by this the electret and piezoelectric properties. Excellent electret properties were obtained in the case of highly stretched i-PP films containing 10 wt% of NA11, known as a nucleating agent additive for i-PP. Additionally, piezoelectric activity (d33=179 pC/N) was observed in these films. i-PP films with glass spheres showed piezoelectric coefficients between 17 and 170 pC/N, depending on glass sphere size and concentration as well as on draw ratio
Keywords :
corona; dielectric polarisation; electrets; piezoelectricity; polymer blends; polymer films; porous materials; (2,2´-methylene-bis-(4,6-di-tert-butylphenyl)-phosphate) particles; cavity formation; cellular stretched isotactic polypropylene films; charge drift; charge storage stability; corona poling method; electret applications; electret properties; glass hollow spheres; glass sphere size; nucleating agent; piezoelectric activity; piezoelectric coefficients; piezoelectric properties; piezoelectricity; polypropylene morphology; porous polypropylene blends; Calcium; Corona; Electrets; Glass; Impurities; Material storage; Morphology; Piezoelectric films; Polymer films; Stability;
Journal_Title :
Dielectrics and Electrical Insulation, IEEE Transactions on
DOI :
10.1109/TDEI.2006.247824