Predicting infiltration into nonwoven felts using measurements of the moisture characteristic curve

 

Wing Kei Rebecca Wong

Department of Physics and Astronomy

University College London

March 2004

Supervisors - Dr A Cottenden and Dr M Landeryou

 

Abstract

In this project, the needs of improving the engineering of reusable incontinence pads is explained; and the prediction of fluid infiltration into nonwoven felts using measurements of the moisture characteristic curve is reviewed experimentally for a range of fibrous materials. The modelling techniques based on Washburn's and Richards' equations are described. It shows that Washburn fails to describe infiltration processes due to lack of information about the wicking properties of fibrous materials.

The experimental methods to find the closure relationships between pressure, moisture level and permeability as an input into Richards' equation (which describes the fluid transport in porous materials) are described. The figures below show the permeability-saturation graph (left), and the numerical simulation of the horizontal wicking measurements (right) of one of the six samples that we investigated:

             

The results show good agreement is observed between analytical fits, numerical solutions and experimental results of the flow of fluid from sources on inclined or horizontal homogeneous fibrous materials. Unfortunately, with the limited time available for this project, the results have not been applied to interpret the spreading of fluid in incontinence pads.

In the future experiment, there are still many challenges for obtaining a complete model of absorption by incontinence pads, including the effects of external loading, deformations of the material in use and leakage from the product.  

The continuation of the project is to complete the capillary pressure characterization measurements for the remaining samples, in order to model the liquid transport in the range of fibrous materials. Relationship between the closure relationships and the absorbent performance of the materials needs to be captured, in order to model the infiltration of liquid in incontinence pads.

Since medical absorbent includes a multiple of scales, it is a challenge to understand the connection between the microscale/structural features and the bulk properties of the absorbent in the future.

 

A more detailed summary of the project can be found in the link below:

Detailed project summary

Contacts: w.wong@ucl.ac.uk