Process and property optimization in a spunbonding process

The production of a spunbond fabric involves the inter-relation of numerous process variables. The development of fiber morphology is influenced and controlled by the extrusion variables. Fabric properties are greatly influenced by the properties of the filaments composing them, web structure and the bonding conditions. Understanding the relation between the process parameters and the properties is of utmost importance since, the desired properties of the end-product can be predicted and engineered by adjusting the process conditions.

This study was conducted to understand the effect of process conditions on the structure and properties of the filaments and fabrics, and to postulate the optimum conditions to achieve the desired properties. The change in fiber morphology due to thermal calendering and the rupture mechanisms of the webs were also studied. Four process variables - polymer throughput rate, cooling air speed, web basis weight and bonding temperature were chosen. Filament samples collected before bonding and the bonded fabrics were analyzed for aspects of structure and properties such as crystallinity, birefringence, density, thermo-mechanical stability, tensile properties, tear strength and flexural rigidity. The ruptured fabrics from the tensile tests were observed under a secondary electron microscope to understand the mechanism of rupture. Filament morphology changed with process conditions with consequent changes in fabric properties. Analysis showed the effects of filament morphology, filament orientation in the web and the bonding conditions on the fabric properties. Different rupture mechanisms were observed for different process conditions. Statistical analysis provided a method to predict the properties for different process conditions.