VIII. Reading and writing.

Exercise 26. Read Text D with a dictionary and put down its translation.

Quality in Flax Production and Processing.

The primary objectives of retting and processing is to break down or remove mechanically the non-celluloic polysaccharides, i.e. pectin’s and non-structural hemicellulose, and in addition partially degrade lignin and associated components. This enables the primary fibres to separate and draft freely during preparation and spinning. However, the non-uniform nature of dew-retting along the top and root ends of the stem, and difficulty in determing accurate endpoint of retting tend to cause variability in fibre quality.

The processing costs of flax fibre are much greater than those of other fibres such as cotton. This is mainly due to need for processing the retted straw with much greater care by scutching, hackling, doubling, roving, chemical treatment and spinning to achieve the quality of yarn.

The proportion of non-cellulosic components associated with fibre will largely determine, spinning limits and the resulting quality of yarn. Consistent quality in terms of strenth and regularity of yarn is necessary to improve efficiency and reduce production cost. Enzymatic treatments of rove bobbins for removing residual pectins and hemicellulose present on fibre substitute caustic boil. With the recent availability of lignin degrading enzymes in a commercial scale, sprit could be removed along with the residual non-cellulosic polysaccharides. If feasible on a commercial scale, this could replace conventional chlorite stage, as the enzyme treated rove bobbins could be bleanched with a mild peroxide process containing a suitable optical brightening agent.

A concerted effort from biochemists, molecular biologists, textile chemists and others is needed to find ways of improving flax cultivars for various characteristics without reducing resistance to lodging and diseases. In addition, an integrated approach to optimize flax processing, should be established in order to prioritize research and development.

Notes:

scutch – тріпало; тріпати, лляти (льон, коноплю)

hackle – чесалка для льону, чесати льон

doubling – кручення, сучення

enzyme – фрагмент, ензим

bobbin - бобина

caustic boil – виварювання у каустичній соді

sprit – кострa

IX. Supplementary reading. Assessment of Quality

Strength, co-efficient of variation of strength, the maximum and minimum breaking loads, regularity, twist factor and appearance are important parameters for assessing yarn quality. Weaving efficiency of a good quality yarn can still be adversely affected, if surface damaged during winding. The relationship between yarn quality and weaving efficiency is complex as the material is not normally exposed to tensions approaching the mean breaking load; breaks could occur at relatively low tensions of half the breaking load or less – at weak links in the yarn, which result in loom stops.

Current procedures based on blending of raw fibre to achieve consistent yarn quality need to be backed up by key physical, chemical and instrumental measurements. This will allow monitoring of the changes in fibre and yarn characteristics for the following:

Physical parameters. The samples need to be analyzed for the following parameters: regularity (thicks and neps), strength, elongation, yarn twist, hairness and microscopic assessment of yarn defects.

Chemical parameters: Analyses for components including cellulose, hemicellulose, lignin, pectin, wax, ash, minerals and degree of polymerization/ fluidity need to be measures for all samples. These parameters will indicate differences in structural and non-structural components of the fibre.

Thermal parameters: Differential thermogravimetry (DTG) can be used for rapid analysis of residual components, such as hemicellulose, pectin and lignin of fibre and yarn. DTG is used to investigate physical and structural changes in the fibre matrix during processing as well.

Near infra-red spectra: The fibre and yarn samples need to be scanned for their compositional characteristics by NIR spectrometers. The hardware and software currently used for analysis of spectral data are very sensitive and powerful.

Multivariate analysis: Recent advances in electronics and computer hardware allow data from various measurements to be analyzed by sophisticated statistical software. The special data can be correlated with key physical, chemical and thermal parameters and relationships between fibre and yarn qualities could be determined. Important fibre or yarn quality parameters can be selected on the basis of their regression co-efficients, which relate to yarn quality, weaving efficiency and quality of the product. An NIR based quality assessment system could be used on the factory floor and this may satisfy the production requirements of spinners and weavers.