| Popis: |
This thesis presents investigations of liquid ingress and vapour uptake in different porous media including textile fabrics and activated carbons, monitored by means of a unilateral NMR instrument. The aim of this work is to assess protective materials which prevent toxic liquid ingress and toxic vapour uptake from contaminating materials and personnel. A high performance fabric made of a combination of coated and not coated fibres can provide extremely high protection against toxic liquids. By incorporating an adsorbent layer between two highly repellent layers, an “intelligent” fabric that can prevent complete penetration through the composite system by toxic vapours can be constructed. This project was undertaken with a low-field unilateral profile NMR Mouse® (MObile Universal Surface Explorer) which can collect signal from a thin and flat sensitive volume (ca. 1.5 cm x 1.5 cm x 0.6 mm) up to 10 mm above it, and in a non-invasive manner. The instrument uses a strong inherent magnetic field gradient (11.38 T.m-1) in conjunction with pulsed radio frequency waves. The method makes use of Fourier Transformed NMR in order to spatially resolve 1D vertical profiles for each measurement over a field of view exceeding 500 µm and with a spatial resolution of 15 µm. One system investigated was a laminate heterogeneous layered fabric, made of a horizontal stack of three individual layers, each 70 μm thick, constructed from entangled fibres of 10 µm in diameter. The top and bottom layers are strongly repellent to the oil used as a model that represents a simulant for a toxic liquid, whilst the middle layer is non-repellent and allows oil to absorb inside. |
