Cotton fibers have poor hygroscopicity when untreated, mainly because air and fibers are coated between hydrophobic fibers such as grease and cotton wax. In order to promote the penetration of the treatment liquid, a surfactant capable of lowering the surface tension and the interfacial tension between water and oil is added. This type of surfactant promotes the rapid wetting of the fiber or fabric surface by the aqueous solution and penetration into the interior of the fiber. Therefore, penetrants and wetting agents are not only mainly used in pre-treatment processes such as desizing, scouring, mercerizing or bleaching, but also widely used in dyeing, printing and finishing processes. Since scouring aids generally require better permeability, many scouring aids can also be used as penetrants. Surfactants used as penetrants and wetting agents are primarily anionic and nonionic surfactants.
The characteristics of the penetrant and wetting agent are generally:
(1) It can withstand hard water, acid or alkali.
(2) Strong penetrability, which can shorten the processing time.
(3) The capillary effect of the treated fabric can be significantly improved.
The application of wetting agents and penetrants should be selected according to the nature of the solution. Taking the acid-base substance of the solution as an example, the pH value will vary within a wide range according to different uses and different process requirements, and some are also used in combination with an oxidizing agent or a reducing agent, and the working fluid conditions are often applied to the penetrant or the moisturizing agent. The requirements of the wet agent are extraordinary. Table 3-1 shows the various penetrants applicable to different dyeing and finishing processes.
