Structure Gradients Between Fibers and Thermal Point Bonds in Polypropylene Nonwovens, 1999 Nonwovens Conference Proceedings
Stephen Michielsen
School of Textile and Fiber Engineering
Georgia Institute of Technology
Industry continually tries to bond nonwovens more quickly by using higher temperatures for shorter times. As the bonding temperature increases, the processing window narrows and finally closes. The processing window closes either because the nonwoven properties are unacceptable, or because the thermal point bonds are poor, or both. Crossing this major hurdle is complicated by the lack of good analytical techniques to determine what structural changes occur during processing.
This report describes a new technique, Raman microscopy, that is able to measure the crystallinity and birefringence of single fibers within a nonwoven. By making these measurements at small intervals (~10 mm), the rate of structure change can be measured on a single fiber from the non-bonded region into the bonded region. Using this technique, the structure changes and the rate of change can be measured as a function of bonding temperature/time. From this analysis, a good understanding of the process/structure/property relationships can be obtained. It is anticipated that this approach will lead to new fibers and new bonding processes to improve properties and process speeds.