A laminated cellular electret film with surface charge self-recovery property for reliable wearable devices was developed.

No abstract

Polylactic acid (PLA) is a biodegradable and biocompatible polymer. Melt‐blown PLA electret fabrics have become attractive materials for air filter applications. Its filtration performance mainly depends on the electrostatic effect originating from electrets. How to improve their electret behavior and then to enhance their filtration efficiency has always been challenging. In this article, three melt‐blown PLA fabrics with different morphological or crystal structure are made from different process conditions or ingredient. The electrets are formed by means of corona charging technology. Their crystalline and morphological structure was analyzed, and filtration performance was measured. Their charge‐trapping feature was studied by thermal stimulating discharge technology. The results proved that the air filtration efficiency of three melt‐blown samples improved a lot when electrets were formed. Different crystalline structures of PLA fabrics will result in differences in their electret charge‐trapping feature. The PLA fabrics with semi‐crystalline characteristics display a regular charge‐trapped level distribution and amorphous structure hints the diversity of charge‐trapped levels. The deference in filtration resistance is mainly ascribed to the different fiber diameters and their distributions. More narrow distribution of fiber diameter leads to more compact fabrics and to higher filtration resistance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48309.

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 1108C. 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, 89Å and 86Å as compared to 107Å 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.