In this study we explore the feasibility of using of islands-in-the-sea (I/S) fibers in the spunbond process to produce relatively high strength micro-and nanofiber webs. The relationships between the number of islands, percent polymer composition, and the fiber and fabric properties are reported. Nylon 6 (N6) and poly (lactic) acid (PLA) were used as the islands and sea polymers, respectively. Micro-and nanofibers were obtained by dissolving PLA polymer from the final spunbond nonwovens. The fibers with 25% N6 showed a decrease in fiber diameter from 1.3 to 0.36 mm (micron) when the number of islands was increased from 36 to 360. The diameter of fibers with 75% N6 showed a decline from 2.3 to 0.5 mm for the same range. Hydroentangling was found to be the preferred method of bonding of the I/S structures; the bonded structures were able to withstand postprocessing steps required for dissolving of the sea from the resulting nonwovens. Hydroentanged micro-and nanofiber based nonwovens demonstrated high tensile and tear properties, which were insensitive to the N6 fiber size and its mechanical properties. Bonding efficiency and web uniformity were found to be dominant factors influencing the fabric performance. Overall, our study demonstrated that the I/S configuration is a promising technique for high speed and high throughput production of strong and light weight nonwovens comprised of micro-and nanofibers.

Recent research on all aspects of thermally point bonded nonwovens has led to considerable improvements in the understanding of material requirements for these nonwovens, the changes that occur during bonding and the resultant deterioration of the mechanical properties of the nonwoven materials. This paper addresses how one may use a bicomponent fiber technology to overcome the shortcomings of the thermal bonding and obtain high strength spunbond fabrics. In particular, we present the utility of islands-in-the-sea (I/S) bicomponent fibers for optimizing the strength of thermally bonded fabrics. To examine the role of various bonding temperatures on the fabric performance, preconsolidated webs were formed and subsequently, thermally bonded. Thus, any influence introduced by potential variations in the structure was minimized. Point-bonded bicomponent samples made up of nylon-6 (N6) as the islands and low density polyethylene (PE) as the sea showed great promise with respect to their mechanical properties, suggesting that the use of bicomponent fibers can be beneficial for strength optimization of thermally bonded spunbond nonwovens.

The increased emphasis on nano-structured materials is placing an ever increasing demand on sample preparation techniques to unveil such fine structure. Nano-structured fibers are even more difficult because of the ease with which these materials can smear even when prepared under liquid nitrogen (LN2) as shown (Figure 1). This is especially true for the islandin- the-sea structures where it is rather hard to reveal the island structures due to smearing. In the search for a possible solution, a sample preparation technique that has shown great results in other composite structures of different polymer blends was applied to these structures.

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