Prediction of core bulk using OFDA instruments

Abstract

The compressibility of a mass of unprocessed wool fibres, termed bulk, is positively related to yarn bulk, and carpet wear resistance and appearance retention of carpets produced from that fibre. As wool bulk is positively related to the dimensional measurements of fibre diameter and fibre curvature it is possible to predict wool bulk from measurements of these characteristics. A series of experiments have shown the best predictor (R² = 85%) of core bulk to be a model containing log_e transformation of mean fibre diameter, mean fibre curvature, (mean fibre curvature)² and small blob percentage derived from an OFDA100 instrument. If a field measurement of greasy wool was required the best predictor (R² = 84%) of core bulk was a model containing log_e transformation of mean fibre diameter, mean fibre curvature, (mean fibre curvature)² and small blob percentage derived from OFDA2000 measurements where the staple was restrained in a wire slide. A number of simpler models were capable of producing significant predictions of core bulk (R² > 80%) using either laboratory or field measurements. The age of the measured sample did not significantly affect its measured core bulk while an assessment of crimp form, as reflected by the ratio of fibre length divided by staple length or the degree of lustre in intact greasy staples, did not improve the prediction model in practical terms.