Lynne Wong's PhD thesis

decreasing specific mass loss, the drying is automatically ended as soon as the mean mass
loss of 1 mg drops below 10, 20, 50, 90 and 140 seconds respectively. A built-in printer
records the sample mass, the analysis method, the time and the results in the form of
percentage moisture content or percentage dry matter. The apparatus also provides an
integrated programme for statistical analysis of the last five test results.
4.4.6.2 A rapid method developed to determine residual moisture in fibres by halogen
thermogravimetry
After much experimentation, the following method was found to be precise and suitable for
the rapid determination of moisture in fibres. It consists of the use of a glass fibre filter
previously dried under the same conditions as the sample for use as a cover for the drying
of the sample.
4.4.6.2.1 Equipment
A Whatman GF/C glass fibre filter of 9 cm diameter and a Mettler Toledo (Model HR73)
moisture analyser were used.
4.4.6.2.2 Method of determination of residual moisture in fibres
The integrated balance of the moisture analyser was tared with the aluminium pan on the
balance. A Whatman GF/C glass fibre filter was placed on the pan to dry by using the
standard drying programme at 105 °C and automatic switch-off mode 3. At the end of the
drying programme, the filter was quickly removed with a pair of tweezers, placed in a
petri-dish with cover, and allowed to cool in a desiccator.
After the halogen moisture analyser was cooled to about 65 °C, the balance was quickly
tared with the dried filter, after which, the filter was quickly put back into the petri-dish
and covered. About 0.6 g of the fibre sample was quickly shaken onto the aluminium pan,
spread out evenly with a spatula, and covered with the dried filter. Drying was then started
by using the same standard drying programme as above at 105 °C with automatic switchoff
mode 3. At the end of the heating programme, the moisture content in the sample was
displayed. This method of moisture determination in fibres had the great advantage of
requiring only a few minutes instead of the three hours essential in the standard drying
method.
After the determination, the aluminium pan was wiped with a clean and dry cloth, and any
fibre adhering to the glass filter was shaken off. The above cycle could be repeated for the
next sample by first drying the filter again. This could be done while the moisture analyser
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