engleski

Reducing Fibrillation Tendency of Man-made Cellulose Fibres Employing Ultrasound Treatment

The positive impact of ultrasound treatment obtained on some polyamide and p-aramide fibre properties, especially the reduction of fibre ageing tendency induced by sunlight and UV-radiation, stimulate the investigations of the possible impact of ultrasound (USN) on the other fibres. The investigation presented determines the impact of ultrasound treatment on cellulose fibre properties, their dimensional, morphological, mechanical, physical and chemical characteristics. The results obtained indicate that ultrasound treatment yields certain amount of fibre shrinkage and raises linear density. The number and intensity of curls, breaking strength and breaking elongation of man-made cellulose fibre also rise after ultrasound treatment has been applied. The paper presents the impact of ultrasound treatment on the reduction of fibrillation tendency of mane-made fibres, especially important for lyocell fibres where the problem of fibrillation is most evident. Fibrillation tendency of cellulose man-made fibres is defined as a locally limited splitting of fibrilles alongside the fibre axis, caused by the influence of water and mechanical stress. The investigations described were performed on samples of viscose and lyocell fibres. Two samples of different fineness were chosen from each fibre type – one of relatively low fineness and another of higher one. Ultrasound treatment was performed in an ultrasound bath SONIC 4 GT, manufacturer ISKRA ; the USN frequency being 30 kHz. Distilled water at room temperature was used as a medium of propagating the ultrasound waves. All the samples were simultaneously subjected to ultrasound waves and the treatment lasted for 30 min. After the treatment, fibre samples were dried and conditioned in a standard atmosphere. In order to cause fibrillation, fibre samples were shaken over a period of 4 hours, in a 250 ml bottle containing 100 ml distilled water. Fibre fibrillation tendency was investigated using modified and developed microscopic method (magnification level 640 x). Based on fibrillation appearance, fibres were assessed and sorted in seven grade groups marked 0, 1, 2, 3, 4, 5, 6, according to the criteria established4]. For a reliable final assessment (uncertainty ≤ 2 %) it is necessary to make approximately 500 measurements per sample. The characteristic images of fibrillation were made with magnification level of 252 x. Calculated indicators of fibrillation intensity are:  total percentage of fibrillated fibres (including all the numerical assessments),  percentage of fibrillated fibres for each numerical assessment and  fibrillation degree DF. Investigation and measuring results indicate that ultrasound treatment yields reduced fibrillation degree and reduced total percentage of fibrillated fibres. This effect was observed on all the fibre samples tested.

cellulose fibres; fibrillation tendency; ultrasound treatment

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