Process–Structure–Property relationship of roping in meltblown nonwovens.

For applications such as face masks and medical gowns, defects can pose a threat to the reliability of protective materials. Roping, the entanglement of two or more fibers in a nonwoven, can cause a decrease in pore size uniformity, filtration efficiency, and barrier properties in meltblown nonwovens. In this work, a novel measurement methodology for roping was developed utilizing SEM images, ImageJ software, and statistical analysis with R. The study analyzed 16 different meltblown nonwovens with two different die tips with a 1550 MFR polypropylene, utilizing a full factorial design with 4 factors at 2 levels. A model was developed for the mitigation of roping, and it was determined that the interactions of capillary density with air flow and air flow with die-to-collector distance (DCD) had the greatest impact on the formation of roping in meltblown nonwovens. The fundamental learnings of the effects of the process parameters on roping formation could be applied to industrial applications such as face masks to tailor the balance between filtration efficiency and air permeability. The linear model could be directly applied to applications such as HEPA (High Efficiency Particulate Air) and ULPA (Ultra Low Particulate Air) filters, for operating room and clean room filters, in which nonuniformity and loss of surface area critical to performance, and thus the mitigation of roping would be beneficial. [ABSTRACT FROM AUTHOR]