Devices for on-line assessment of nonwovens' basis weights and structures

Two devices for quantifying the basis weight and fiber orientation distribution function in nonwoven webs have been developed and studied. The basis weight device measures the attenuation of a light beam by the fabric. The particular device is implemented, calibrated, and tested at speeds up to 400 m/min. By statistical analysis, this device is accurate enough to use with fabrics that are three or more times less variable than current commercial nonwovens. The device for quantifying web structure measures the orientation distribution function of a static sample by light scattering, and it is sensitive enough to detect subtle differences in spunbonded webs produced with different filament-dispersing hardware. An anisotropy ratio calculated from measured orientation distribution functions correlates well with fabric tensile properties.