A study of thermal bonding of melt blown and spunbonded laminates and repellent finishing techniques

In this study more effective methods of applying a fluorochemical finish to relatively inexpensive melt blown/spunbonded (MB/SB) nonwoven laminates produced in the Textile Materials Research Laboratory were investigated with respect to improved performance and lower cost. The two possible end-uses for the MB/SB laminates are operating room drapes and gowns and apparel for agricultural workers, such as, pesticide applicators. In addition to comparing finishing techniques, the thermal bonding sequence of a MB/SB laminate before and after finishing also was studied to determine the effects on repellency, barrier properties, laminate bonding strength, air permeability, and drapability.

Polypropylene melt blown webs produced on the melt blown pilot line at DTK were laminated with an experimental point bonded spunbonded polypropylene fabric obtained from Du Font. Polypropylene melt blown and spunbonded laminate samples were thermally bonded with a smooth roll calender both before and after fluorochemical (FC) finishing by the more conventional padding technique and by two low wet pickup methods, foam finishing and kiss roll applications. Repellency (oil, alcohol and water repellency) and barrier properties (water impact resistance and air permeability), and bonding strengths were examined.

Surprisingly, the MB/SB laminates, which were thermally bonded prior to finishing, picked up substantially less finish due to decreased porosity, and had much improved oil and alcohol repellency. The foam finished laminates had the highest oil and alcohol repellency values followed by those prepared by kiss roll and finally the padding techniques. Although all of the finished MB/SB laminates had excellent water spray ratings and water impact penetration resistance (due to the barrier properties of the melt blown component), the key to oil and alcohol repellency appears to be the concentration of FC finish deposited on the outer surface of the laminate.

Generally, the thermally bonded laminates had somewhat lower air permeability, as compared to the unbonded laminates. The melt blown and the spunbonded components separately had appreciably higher air permeability. However, the air permeability values of the MB/SB laminates, which were thermally bonded before FC finishing were generally higher than a slightly lower weight commercial spunbonded/melt blown/spunbonded (SMS) fabric, which had been thermally point bonded. Laminate bonding strengths were much lower than the commercial point bonded SMS fabric, but were believed to be suitable for protective clothing application.