Fabric finishing processes

Fabric finishing processes, stabilisation and surface treatments, are carried out to ensure fabric stability and to modify its surface characteristics to regulate the fabric permeability. 

Surface treatments include singeing, calendering and other special treatments designed to give good filtrate clarity and cake discharge characteristics combined with a low cloth resistance and a reduced tendency to blind. 

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Various regulations are valid when dealing with fabric finishing processes. Some important directives are listed below. More information about these directives can be found via the links in the paragraph on sources of further information and advice , the references or in Chapter 1. 

This chapter will provide the reader with a general introduction to the more common types of solid-gas (dust collection) and solid-liquid filtration mechanisms. The raw materials, polymers, fibres, and different types of fabric construction employed in filter media manufacture and some typical fabric finishing processes are discussed in detail. A brief look at filter market developments will also be considered. 

Fabric finishing processes are designed essentially to ensure that the fabric will (a) remain dimensionally stable during use, (b) provide effective cake release during the cleaning cycle, (c) meet the fabric s designed air permeability (a control parameter widely used in the industry) and (d) be protected, as far as possible, from any chemical conditions that may be encountered in the filter. 

These are water-soluble crystalline compounds sold as concentrated aqueous solutions. The methylol groups are highly reactive (118—122) and capable of being cured on the fabric by reaction with ammonia or amino compounds to form durable cross-linked finishes, probably having phosphine oxide stmctures after post-oxidizing. This finishing process, as developed by Albright Wilson, is known as the Proban process. 

Whitening in combination with the finishing process is used primarily for woven fabrics of ceUulosic fibers and their blends with synthetic fibers. 

Finishing may also be viewed as another means for providing nonwovens with additional appHcation-dependent chemical and/or physical properties. Finishing processes bring about value-added fabrics with technically sophisticated properties for specific end use appHcations. 

Smooth surfaces are normally estabflshed by calendering, a process which subjects the fabric at the nip point(s) of two or more roUs to the influence of controlled time, temperature, and pressure. When calendering is used as a thermal-bonding process, the roUs are of the same dimension and composition and are independently driven. However, when calendering is used as a fabric finishing operation, the roUs are frequently of different dimensions and composition and are not always independently driven. 

After the fabric formation process, textiles are generally subjected to either dyeiag or printing and to a variety of mechanical and chemical finishing operations. The specific nature of the dyeiag and finishing operations depends on the fiber type and on the iatended use of the fabric. 

An important chemical finishing process for cotton fabrics is that of mercerization, which improves strength, luster, and dye receptivity. Mercerization iavolves brief exposure of the fabric under tension to concentrated (20—25 wt %) NaOH solution (14). In this treatment, the cotton fibers become more circular ia cross-section and smoother ia surface appearance, which iacreases their luster. At the molecular level, mercerization causes a decrease ia the degree of crystallinity and a transformation of the cellulose crystal form. These fine stmctural changes iacrease the moisture and dye absorption properties of the fiber. Biopolishing is a relatively new treatment of cotton fabrics, involving ceUulase enzymes, to produce special surface effects (15). 

The standard conventional finishing process has been modified to suit the purposes for different fabrics and garments. Eor example, tubular knits are frequently handled using specialized equipment to control tension and to get adequate padding. Some tubular knits are subjected to wet-on-wet padding, dried and cured in large dmm dryers, and steam-treated to achieve a relaxed and nondistorted knit. 

Flame Retardants. The amount of research expended to develop flame-retardant (FR) finishes for cotton and other fabrics has been extremely large in comparison to the total amount of fabrics finished to be flame retardant. The extent of this work can be seen in various reviews (146—148). In the early 1960s, a substantial market for FR children s sleepwear appeared to be developing, and substantial production of fabric occurred. In the case of cotton, the finish was based on tetrakis(hydroxymethyl)phosphonium chloride (THPC) or the corresponding sulfate (THPS). This chemical was partly neutralized to THPOH, padded on fabric, dried under controlled conditions, and ammoniated. The finish was subsequently oxidized, yielding a product that passed the test for FR performance. This process is widely preferred to the THPOH—NH process. 

Stages Basic Chemical Monomers Polymerization Compounding Processing Fabricating Finishing... 

Further problems may arise from the possible effects of residual cyclodextrins on subsequent processes. For example, as described above, a cyclodextrin can be used to remove residual surfactants from a fabric after scouring, yet it is possible that any residual cyclodextrin could itself interfere with subsequent coloration or finishing processes to the same extent as the surfactants that have been eliminated. 

Nonwoven cards, 17 499-500 Nonwoven fabrics, See also Nonwoven materials Nonwovens Nonwoven textile materials global demand for, 17 483t spunbonded, 17 460—494 staple-fiber, 17 495-518 Nonwoven finishing processes,... 

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