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Compatibility of different finishing chemicalsThere are quite a number of factors making the chemicals / softeners used in a recipe mutually incompatible – the ionic characteristics, solubility, emulsion stability, pH conditions etc. Stabilizers used in an emulsion may be disturbed by ‘new’ / alternate additive in a recipe, thus cause break up of the emulsion. When two or more finishing chemicals in a recipe is contemplated or when recipe is changed for reasons of non-availability of one of the components, it is desirable to check their mutual compatibility in the laboratory before administering in bulk. Strength of the finishing agent It is desirable to apply the recommended level of the softener. Commercial softeners / finishing agents come in different strengths and it is the active matter that is important. Some cases dilution needs to be done to a working concentration level from concentrated pastes / emulsions with the application level fixed, the new consignments of the softeners are to be evaluated for the active content and accordingly recipe should be adjusted to match the standard recipe quantity.
Influence of moisture regain Cotton regains 7 to 8% of moisture. This plays an important role in the feel of the fabric. Over dried fabrics tend to feel relatively harsh despite application of softeners. It is also necessary to have satisfactory moisture regain before finishing by padding methods particularly resin finishes to facilitate better and even diffusion and penetration of the finish. It is desirable to control the drying of the fabrics to moisture regain level using control instruments like Textometers in a stenter operation or cool tumbler in the drying of the garments. There are conditioning cycles in the drying operations in the modern machinery in the batch wise processes also – i.e. like in yarn drying. Selection of softeners to improve crease resistance, antistatic and lubricity properties The simple cationic softeners do not impart any crease resistant properties to cotton. They do help in imparting antistatic properties especially to synthetics. They exhibit a good mixture of hydrophobic and hydrophilic characteristics on the fabric and hence are excellent softeners and also help dissipate static charge at the same time. The cationic softeners provide lubricity by virtue of their hydrophobic fatty component in their molecule, thus reduce the coefficient of friction between the fibers, improve inter fiber slippage and thus the sewability. In the case of silicone, the cross linking of functional siloxanes reacting with hydrogen siloxanes produce a matrix of elastomeric film on top of the fibers which gives the bouncy rubbery softness. This aspect is more pronounced with enhancement in the inner softness, when micro dispersed emulsions are used. These are able to penetrate between the fibers more effectively because of the micron size – 100nm or lower. They also spread uniformly on the surface due to lower particle size. In the case of normal emulsions the micron size have wide disparity ranging from 300nm to 10000nm and much of the finish remains on the surface in heaps and thus has less influence on the smoothness / lubricity in the interior of the yarn. In the case of micro fibers only micro dispersed emulsions may be used. A combination of cationic and silicone based softeners should be established for the specific requirements of a fabric. It would depend on the weight and construction and would be specific to functional requirements i.e. lubricity / sewability feel, extent of hydrophobic / hydrophilic characteristics, crease resistance, etc. Silicone based softeners also give certain level of crease resistance properties to cotton, besides the superior soft finish. In conjunction with resins of the type DMDHEU even with less add on of the resin, the feel, crease recovery, abrasion resistance, tear strength etc. improve considerably. However, the tolerance levels of the free formaldehyde on the finished substrate has become increasingly stringent and hence the formaldehyde based reactive resins find only limited application – i.e. where permissible limits are liberal for certain categories of fabrics. Formaldehyde free poly carboxylic acids based reactive resins find increasing application in crease resistant finishes.
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