The thermal history and inherent properties of the filaments are of utmost importance in spunbonded webs. A good. understanding of the structure and properties development of individual filaments is helpful in comprehending the whole process better. Polypropylene homopolymer and a copolymer were processed using the Reicofil(R) spunbonding line at the Textiles and Nonwovens Development Center of the University of Tennessee, Knoxville. The properties of the filament samples taken before thermal bonding were determined through a variety of thermal analyses, such as differential scanning calorimetry, thermomechanical analysis, thermal deformation analysis, and dynamic thermal analysis, as well as mechanical properties. The performance properties of the bonded nonwoven fabrics from these filaments were evaluated, and the structure and properties of the fibers were compared with those of the bonded fabrics.