Study on correlation of filtration performance and charge behavior and crystalline structure for melt‐blown polypropylene electret fabrics

Melt-blown polypropylene (PP) electret fabrics are widely used as air filter media due to the specific mechanism of electrostatic filtering. In this article, two additives, stearate and modified rosin, are doped to PP fabrics during melt-blown process. The filtration performance of doped PP gets improved greatly, with filtration efficiency increased by 6% at room temperature but its temperature stability promoted dramatically. As a result, the filtration efficiency of doped PP still remains above 95% of its initial, whereas that of non-doped PP only remains 58% at 110°C. By XRD characterization the structure modification is observed after doping. The crystallinity increases from 14.17% to 22.64% and 29.62%, respectively. Meanwhile, the crystallite has a smaller size, respectively, 89A and 86A as compared to 107A for non-doping in the direction vertical to lattice plane (110). This demonstrates that additive doping can give rise to larger crystallinity and more fine-grained crystallite. Therefore, doped PP improves its charge storage behavior ascribing to expanding interface between crystallite and amorphous region and then enlarging charge trap density. Furthermore, the effect of additive doping on electret charge storage behavior is investigated by short-circuit TSD, and the filtration performance can be explained relevantly with TSD. A charge storage profile is also adopted to illustrate that the space charge captured by charge traps is in the form of space-charge dipole with the rigidity of crystallite. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42807.