Development of cotton nonwovens for protective applications

In Part A of this study, ten cotton based laminates were produced by thermally bonding cotton cores placed between melt blown webs and/or spunbond web as the outer layers. Six cotton laminates were repellent finished to further improve barrier properties. All the laminates were tested for barrier, drapability, and strength properties. Six unfinished and finished cotton laminates were tested for Kawabata Evaluation System (KES) analyses, moisture vapor transport rate (MVTR), and synthetic blood penetration test. Repellent finished laminates had better barrier properties and had higher drapability, while the unfinished laminates displayed higher strength. KES analyses showed that the laminate having 80% cotton had the best mechanical hand properties. Laminates having spunbond web had the highest MVTR among all the laminates. Repellent finishing was found to slightly decrease the MVTR of all the laminates having melt blown outer layers. The Wilcoxon Signed Rank test was used to determine if the differences in the properties of the unfinished and finished cotton laminates were statistically significant at the 0.05 level. In the comparison of cotton laminates with commercial Spunbond/Melt Blown/Spunbond (SMS) and Kappler's spunbond/ microporous/spunbond (Pro/Vent®) surgical gowns, it appeared that the SMS gown had better strength properties than the cotton laminates although the cotton laminates displayed better barrier properties. The SMS and the cotton laminates did not pass the synthetic blood test. The Pro/Vent® gown was found to be better than the cotton laminates and the SMS gown in terms of drapability, strength, and barrier properties. Attempts were made in Part B of this research to overcome the two main deficiencies of the thermal bonded laminates (Part A) regarding the stringent barrier requirements and higher processing speeds by thermally and adhesively bonding cotton laminates having microporous films. The thermal bonding and preliminary adhesive bonding (melt blowing a hot melt adhesive between constituent layers using a conventional melt blowing line) of cotton laminates used two commercial microporous films (such as Polytetrafluoroethylene {PTFE} Tetratex^™ and the Polyethylene Exxaire®) and point calendered the laminates using rolls at ambient and slightly elevated temperatures. A few of the thermal and preliminary adhesive bonded laminates passed the synthetic blood penetration test, but did not pass the more rigorous viral penetration test. An adhesive melt blown line was used to coat the constituent layers (Including two weights of Polyethylene Exxaire® film) and the laminates were smooth and point bonded at ambient temperature. The adhesive smooth bonded laminates were most successful In resisting the rigorous blood and viral penetration, had good moisture vapor transmission rates, had much faster processing speeds, and had no restrictions on the number of layers In a laminate. The Wilcoxon Signed Rank Test was used to determine the statistically significant differences between the properties of the adhesive smooth and point bonded laminates at the 0.05 level. Darcy's equation (for flow through porous media) and Textile Research Institute's LIquid-AIr Displacement Analysis Instrumentation was used to theoretically and experimentally, respectively, determine the permeability constant of the cotton laminates. Both techniques determined that laminates having two spunbond webs were the most permeable followed by laminates having one spunbond and one melt blown layer followed by laminates having both melt blown layers.