Migration Effects of Fluorochemical Melt Additives for Alcohol Repellency in Polypropylene Nonwoven Materials

The use of bulk polymer melt additives provides a facile, industrially relevant approach to tailor properties of polymer surfaces for many different applications. These melt additives, when blended with polymers prior to melt spinning, migrate to the fiber surface and influence surface functionality. While the use of bulk polymer melt additives to impart hydrophilicity or oleophobicity is well studied, the impact of the fiber formation process on additive migration and resultant repellency of nonwoven media products remains largely unexplored. In this study, we produce fluorochemical melt additive containing meltblown nonwovens, and establish methods for characterization of fiber mat surface composition and repellency. Repellency of low surface tension fluids is a significant challenge and is of particular importance in the creation of medical garments such as surgical gowns and masks which must perform as liquid barriers even when exposed to alcohol based solutions. Similarly, melt additives are also used in the production of electret air filtration devices. Electret filters are imbued with charges to enhance particle capture performance, but this charge can be negated through wetting by low surface tension fluids. To address this challenge, the changing composition of fiber surfaces due to the migration of additives is monitored via X-ray Photoelectron Spectroscopy, then related to repellency of alcohol solutions by contact angle analysis. We demonstrate that for the samples tested a fluorine to carbon (F/C) ratio of 0.35 is sufficient to prevent wicking of isopropanol droplets, and higher surface tension fluids could be repelled by fiber mats with lower fluorine content. Through the use of cross-sectional ToF-SIMS analysis, we find that migration of additives is key to the performance of samples with low additive loadings, and that these phenomena are heavily influenced by many nonwoven manufacturing parameters including fiber size, die-to-collector distance, and polymer resin melt flow rates.