Factors affecting opening size and water permeability of Needle punched Nonwovens

1. With increase in needle punch density, opening size and coefficient of water permeability decrease due to increase in compactness of fabric. Water permeability is however unaffected.
2. Opening size and coefficient of water permeability of geotextile reduce with increase in punch density because of increase in compactness. Again water permeability is unaffected.
3. Calendaring treatment of needle punched fabric improves strength significantly. Opening size, air and water permeability of fabric reduce markedly after calendaring.
4. Fabric made out of finer fibres has lower opening size, less air and water permeability, higher strength at break and at low elongation levels than that made from coarser fabric.