Effect of fabric structure on the liquid transport characteristics of nonwoven wound dressings

Nonwoven materials are widely used in medical and hygiene applications, and may demonstrate significant anisotropic characteristics in liquid transport. This study investigates the anisotropic liquid transport in such structures, and establishes a relationship between the structure and anisotropic properties of liquid transport. A comprehensive literature review is concerned with previous work on liquid transport in general with particular reference to its importance in the function of wound dressings. Preliminary experiments using commercial nonwoven wound dressing fabrics demonstrated the anisotropic nature of liquid absorption. After a review of existing steady state and dynamic methods of measuring the liquid transport in fabrics, a novel computer-integrated instrument is described that measures the in-plane liquid transmission in up to eight different directions. Needle-punched and hydroentangled fabrics with different structural parameters (fibre type, fibre diameter, fabric porosity and fibre orientation) were produced and characterised. The anisotropic liquid transport properties of these fabrics were tested using the new instrument. Unique theoretical models were established to predict the specific directional permeability of nonwoven fabrics based on the main fabric structural parameters (fibre diameter, fabric porosity and fibre orientation distribution).