Influence of Fiber Structure on Properties of Thermally Point Bonded Polypropylene Nonwovens

Carded webs with a basis weight of 30 g/m² are prepared from Hercules T-196 and Hercules T-101 polypropylene fibers, then thermally point bonded with "Novonette" rolls at various temperatures and pressures. A subset of samples is studied in relative detail using various methods. In particular, the distribution of bridging fiber strengths after bonding is measured directly. Bonding at higher temperatures reduces single fiber strength and increases its variability while increasing the effectiveness (strength) of the bonds. These competing effects appear to explain the maximum fabric-strength-versus-bonding temperature relationship. Bonding performance differences between these two fibers appear to depend on the fact that nonfailing bonds can be produced at lower temperatures in the T-196, where fiber strength degradation is less, and possibly to a lesser extent on the higher elongation and concave-down curvature of the stress-strain relationship.