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Textile Finishing
Often fibers in textile substrates are deficient in one or more properties or improved properties are desired for the substrate. Textile finishing provides a method whereby deficiencies in the textile can be corrected or specific properties can be introduced. Physical finishing techniques (dry finishing processes) or chemical finishing methods (wet finishing) are used. Physical finishing is usually carried out on the yarn or formed textile substrate, whereas chemical finishes can be added to the spinning bath prior to fiber formation for man-made fibers or applied to individual fibers, yarns, or completed textile structures.
Softening Finishes in Textile
Softening finishes are among the most important of textile chemical after treatments. With chemical softeners, textiles can achieve an agreeable, soft hand (supple, pliant, sleek and fluffy), some smoothness, more flexibility and better drape and pliability. The hand of a fabric is a subjective sensation felt by the skin when a textile fabric is touched with the finger tips and gently compressed. The perceived softness of a textile is the combination of several measurable physical phenomena such as elasticity, compressibility and smoothness.
During preparation, textiles can become embrittled because natural oils and waxes or fiber preparations are removed. Finishing with softeners can overcome this deficiency and even improve on the original suppleness. Other properties improved by softeners include the feeling of added fullness, antistatic properties and sewability.
Disadvantages sometimes seen with chemical softeners include reduced crock-fastness, yellowing of white goods, changes in hue of dyed goods and fabric structure slippage.
Mechanisms of the Softening Effect
Softeners provide their main effects on the surface of the fibres. Small softener molecules, in addition, penetrate the fibre and provide an internal plasticisation of the fibre forming polymer by reducing of the glass transition temperature Tg. The physical arrangement of the usual softener molecules on the fiber surface is important and shown in Fig. It depends on the ionic nature of the softener molecule and the relative hydrophobicity of the fibre surface.
Cationic softeners orient themselves with their positively charged ends toward the partially negatively charged fiber (zeta potential), creating a new surface of hydrophobic carbon chains that provide the characteristic excellent softening and lubricity seen with cationic softeners. Anionic softeners, on the other hand, orient themselves with their negatively charged ends repelled away from the negatively charged fibre surface. This leads to higher hydrophilicity, but less softening than with cationic softeners. The orientation of non-ionic softeners depends on the nature of the fiber surface, with the hydrophilic portion of the softener being attracted to hydrophilic surfaces and the hydrophobic portion being attracted to hydrophobic surfaces.
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| Softening Finishes |
Softening finishes are among the most important of textile chemical after treatments. With chemical softeners, textiles can achieve an agreeable, soft hand (supple, pliant, sleek and fluffy), some smoothness, more flexibility and better drape and pliability. The hand of a fabric is a subjective sensation felt by the skin when a textile fabric is touched with the finger tips and gently compressed. The perceived softness of a textile is the combination of several measurable physical phenomena such as elasticity, compressibility and smoothness.
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| Softener |
Disadvantages sometimes seen with chemical softeners include reduced crock-fastness, yellowing of white goods, changes in hue of dyed goods and fabric structure slippage.
Mechanisms of the Softening Effect
Softeners provide their main effects on the surface of the fibres. Small softener molecules, in addition, penetrate the fibre and provide an internal plasticisation of the fibre forming polymer by reducing of the glass transition temperature Tg. The physical arrangement of the usual softener molecules on the fiber surface is important and shown in Fig. It depends on the ionic nature of the softener molecule and the relative hydrophobicity of the fibre surface.
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| Fig: Schematic orientation of softeners on fibre surfaces. (a) Cationic softener and (b) anionic softener at fibre surface. Non-ionic softener at (c) hydro–phobic and (d) hydrophilic fibre surface. |
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