Chemical, microscopic, and instrumental analysis of graded flax fibre and yarn

A series of flax fibre and yarn samples that had been commercially graded l ow, medium, and high quality were analysed by light microscopy, wet chemica l analysis, Raman spectroscopy, and nuclear magnetic resonance (NMR) spectr oscopy to determine characteristics which could be related to quality ratin gs for each sample type. Light microscopy revealed fragments of cuticular a nd epidermal material bound to the fibres. As the quality ratings improved, fewer of these fragments were found and greater separation of the fibre bu ndles to smaller bundles and, in some cases, elementary fibres occurred ind icating more efficient retting. Chemical evaluation showed that, as quality of the yarns increased, amounts of fatty acid and long-chain alcohols as w ell as dihydroxy fatty acids decreased. Chemical data on fibre did not show consistent trends with quality. Raman spectroscopy showed increasing amoun ts of cellulose and decreasing amounts of aromatics and hydrocarbons with i ncreasing quality, which paralleled the chemical data. NMR analysis showed nearly equal amounts of crystalline cellulose regardless of quality for bot h fibre and yarn samples. The strengths and weaknesses of each analytical m ethod are discussed. This initial study suggested that chemical constituent s characteristic of cutin and waxes could be used as an initial marker of q uality. (C) 1999 Society of Chemical Industry.