| 摘要 |
<p>1385503 Phenolic resin fibres CARBORUNDUM CO 23 May 1972 [1 June 1971] 24098/72 Heading B5B An infusible cured phenolic resin fibre is subjected to sufficient longitudinal tension to cause at least 30% permanent elongation, whereby its tenacity and Young's modulus of elasticity are improved. The cured phenolic resin may be a cured novolac, and the phenolic hydroxyl groups of the resin may be unblocked or blocked, suitably to the extent of at least 50%. The fibres are made by melt-spinning, and may be cured in a solution of paraformaldehyde and hydrochloric acid. Blocking may be effected by acetylation in a mixture of acetic anhydride and concentrated sulphuric acid, and before subjection to tension the fibres may be swelled by a polar organic liquid, e.g. dimethylformamide, in which the fibres may be immersed during stretching. Stretching may be carried out at temperatures up to 200‹ C. Fibres so made have a tenacity of at least 4 g/den.</p> |
