Fibre damage

These long fibres give better product performance although injection moulding machine modifications may be necessary to prevent fibre damage and reduce undesirable fibre orientation effects in the mould. 

It is more difficult to control the enzymatic processing of wool. Hence there is a greater danger of fibre damage compared with cellulosic fibres. Since cellulose is a highly crystalline... 

The traditional method of carbonising with sulphuric acid is environmentally undesirable and can easily lead to fibre damage. Hence it is not surprising that research has been directed towards alternatives in which enzymes are used to remove the cellulosic impurities from wool. Cellulases and lignases are mainly used but others have been proposed [116] ... 

In this table, the lower amounts of sodium hydroxide provide desizing only, whereas the higher concentrations provide oxidative scouring. The concentrations of the various components are critical to ensure efficiency of action without fibre damage. Hickman [143] gives the following guidelines ... 

The parameter most commonly monitored in this research is the extent of hydrogen peroxide decomposition. Measurement of tensile strength and/or the degree of polymerisation can be useful indicators of fibre damage. The effect of iron(III) ion concentration in accelerating the rate of peroxide decomposition is shown in Figure 10.23,... 

The use of sulphamic acid (12.1) has been recommended, resulting in a shift of pH from 1.8 to between 3.0 and 3.5 as the temperature approaches the boil, thus giving rise to less fibre damage. Typically, 6% o.w.f. sulphamic acid is added, together with an auxiliary and sodium sulphate. The change in pH arises as a result of hydrolysis of the sulphamic acid to give ammonium bisulphate (Scheme 12.1) [2,5]. 

Fibre damage was noted at acetylation temperatures above 130 °C. 

Zeronian, S. H., Alger, K. W., Ellison, M. S., and Al-Khayatt, S. M. (1986). Studying the cause and type of fibre damage in textile materials by scanning electron microscopy, in Historic Textile and Paper Materials, Conservation and Characterisation, vol. 212 (H. L. Needles and S. H. Zeronian, Eds.). Washington, DC American Chemical Society, 77-94. 

A variation on the THPC-urea system was developed to produce finishes with less stiffness and fibre damage (Proban process). A precondensate is prepared by the careful reaction of THPC with urea. This precondensate is padded onto the fabric and the fabric is dried to a specific moisture content ( 15 %). The fabric is then exposed to ammonia vapours in a special reaction chamber, followed by oxidation with hydrogen peroxide (Fig. 8.13). The polymer that forms is primarily located in the lumen of the cotton fibre. The final finish provides durable flame retardancy to cotton with much improved fabric properties. It is important to note... 

Vat dyestuff selection some vat dyestuffs are called fibre protectors, others are fibre damagers. The fibre protectors mostly contain nitrogen atoms in their chromophores. These vat dyestuffs have good light fasmess and compensate for the influence of the damagers. The latter and/or their light decomposition products catalyse the fibre damage by photolysis. 

The efficiency of insect resist finishes can be determined by tests that measure the weight loss of the treated fabrics and/or the weight of insect excrement after exposure to insects under controlled conditions. The direct examination of exposed fabrics by microscopic methods to observe fibre damage is also useful. The typical half round bite traces of the moth larvae are observable. Standard methods for evaluating fabrics with insect resist finishes are given in AATCC Test Method 24. Procedures for cultivating the test insects are included in this method. 

Deactivation of cellulases after the desired effects have been achieved is very important. If the enzyme is not completely removed from the fabric, or is not effectively deactivated, the hydrolysis reaction will continue, although at a slower rate. As very large molecules, cellulases cannot diffuse into the crystalline parts of the cellulose fibres. They react on the fibre surface, so fibre damage takes time. But eventually enough hydrolysis will have taken place to weaken the affected fabrics or garments, leading to customer complaints and returns. 

Dalziel KL, Burge SM, Frith PA, Ryan TJ, Mowat A. Elastic fibre damage induced by low-dose D-penicillamine. Br J Dermatol 1990 123(3) 305-12. 

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