Adapting additives and crystalline structure for long-lasting melt-blown metallocene polypropylene webs

Abstract

Melt-blown polypropylene (PP) electret webs feature low crystallinity and poor charge stability. This study uses an alpha-nucleating agent (DMDBS), beta-nucleating agent (TMB), and two commercial stearate-based masterbatches, which are denoted as C1 and C2, to modify the crystalline structure, electret behavior and filtration performance of melt-blown metallocene PP webs. XRD and DSC analyses show that the crystalline structure plays a critical role in the stability with which space charges are stored. The use of DMDBS, TMB and stearate-based masterbatches also alters the nature and density of charge traps by changing specific molecular structures and the interaction with the semicrystalline PP matrix. Aging at 70 degrees C for 24 h decreases the efficiency of all webs, but the presence of nucleating agents or masterbatches significantly reduces electrostatic decay. DMDBS/PP exhibits the smallest decrease in efficiency and quality factor but the C2/PP web has the most advantageous combination of high filtration efficiency, low pressure decrease and strong long-term stability, so it the best suited to practical filtration applications. These results show the mechanism whereby nucleation-induced crystallization governs electret performance and allows the design of advanced melt-blown metallocene PP electret filters for respiratory protection and environmental uses.