A study of degrees of nonuniformity in physical, repellency and barrier properties of different nonwoven protective apparel fabrics

In this research, physical, repellencyand barrier properties were determined on eight nonwoven fabrics. The uniformity of fabric weight, thickness and air permeability properties were investigated in both fabric machine direction and cross-machine direction by analyzing the data using statistical procedural "Analysis of Variance". Since significant interactions between machine direction and crossmachine direction variables were found in values of fabric weight, thickness and air permeability, only qualitative comparisons of fabric bending length, oil repellency, water spray rating and water impact penetration properties were made.

Eight nonwoven fabrics of three different construction types were obtained in four hundred fifty to nine hundred meter fullwidth rolls. The fabrics consisted of uncoated "Tyvek" which was of the regular and corona treated types; "Sontara" spunlaced fabrics, repellent finished and unfinished; and spunbonded/meltblown/spunbonded (SMS) fabrics at 1.8 and 2.3 oz/yd² (61 and 78 g/m²), both repellent finished and unfinished. Three-meter samples were taken at randomly spaced locations along three hundred to seven hundred meter lengths of each roll. Seven alternate samples taken down the length of the roll were tested for fabric weight, thickness, bending length, air permeability, water impact penetration resistance, and static oil and water repeilency performance properties.

For fabric weight, thickness and air permeability, the variance in cross-machine direction was found to have cyclical trends in the machine direction. Significant interaction effects between machine direction and cross-machine direction was also found by the statistical analyses. These revealed that the relatively large effects of cross-machine direction variability were not constant along the length of the roll. The implications are that researchers should be aware that hidden variations in fabric properties may result in misleading assumptions about the protection offered by fabrics against pesticide penetration.

In the qualitative comparison of fabrics, all repellent finished fabrics appeared to have excellent oil repellency with the oil repellency ratings. The regular and corona treated "Tyvek" fabrics, finished and unfinished "SMS" fabrics and the repellent finished Sontara fabric resulted in virtually no measurable penetration of water in the water impact penetration test, which would indicate that all had good barrier properties. These same fabrics had fairly high water spray ratings which ranged from 70 to 90. However, the repellent finished SMS fabrics in both weights had lower water spray ratings of 70 compared to 90 with the unfinished controls. It was suggested that the mechanical forces encountered in finishing may have broken up the fabric surface structure, and thereby resulted in a greater tendency to hold water on the fabric surface during testing.

The Sontara fabrics had the highest average air permeability values followed by the 1.8 oz/yd^ SMS fabrics, the 2.3 oz/yd² SMS fabrics and finally the two Tyvek fabrics which had no measurable air permeability with the Gurley Permeometer.