WET PROCESSING OF FIBRE BLENDS CONTAINING PRE HARVEST RETTED FLAX

Flax fibres obtained from an early-desiccated (mid-point of flowering), stand-retted crop were found to be finer, softer, lighter in colour, and to contain less lignin than the fibres obtained from crops desiccated at the more usual timings of (a) two weeks alter mid-point of flowering and (b) after ripening of the seeds. Infra red analysis of extracted lignin led to the suggestion that a lower lignin content in the middle lamella of early-desiccated crops permits retting to proceed further, to give smaller (finer) bundles of fibres after decortication. Carded fibres were blended and spun into 33/66 flax/wool and flax/polyester yarns. Appropriate, traditional scouring and bleaching processes were established for these blends. The finer, whiter fibres from the early-desiccated crop were found to respond better to the mild bleaching conditions required for the flax/wool blend. In some cases this also led to increased uptake of reactive dyes, compared with fibres from the later-desiccated crops, but in most cases there were no visible differences between dyed samples containing flax fibres produced by the different agronomic pathways. Enzymatic scouring and bleaching routes, which should cause less damage to wool in the flax/wool blend, were investigated. Scouring with pectinases was, however, shown to remove only 5-25% of the flax pectins and it is suggested that lignin in the middle lamella acts as a barrier against enzymatic degradation of pectins. The application of laccase and laccase/mediator systems (after scouring) were shown to degrade flax fibre lignin to the extent that a single, mild (pH 9 at 60°C) bleaching step with hydrogen peroxide/sodium persulphate was sufficient preparation for subsequent dyeing. Unfortunately, when laccase or laccase/mediator systems were used on the flax/wool blend, there was staining of the wool component which was not removed by subsequent bleaching. Further work is suggested to alleviate this problem. Thin-layer wicking tests with polar and non-polar liquids were used to investigate the effects of scouring and bleaching on fibre/yarn surface free energies. The results were influenced by variation in yarn presentation for the wicking experiments and further work, using fabric strips, is recommended.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

2002

Author dc:creator

• Sampaio, Sandra Cristina Fernandes Monteiro

Licence

• https://dora.dmu.ac.uk/bitstreams/6acf00f6-387d-45c9-98a3-9cadf78b00a3/download