I noticed a weight gain when I carried out a chemical resistance test i.e effect of alkali (NaOH) on both treated(alkali treated) and untreated natural fiber.
Weight loss by chemical treatment depends on concentration of chemicals. If the concentration is low, the fiber will swell by water and gain weight. Approx 22% NaOH (Lower NaOH also have similar effect)treatment on cotton fiber, swells the fiber and make the cross-section circular, which is known as Mercerization. If you increase the concentration more and more that will dissolve the fiber....
The soaking time for the alkaline treatment is one of the factors that may influence the natural fiber behavior. The soaking time may either cause the fiber to shrink or swell depending on the characteristic of fiber. Not all fiber tends to react with the alkaline treatment or acidic treatment. Some fiber tends to to be hydrophobic and some tend to hydrophilic. Change in the structure of molecular level can be seen through FTIR spectral to be specific.
http://ajbasweb.com/old/ajbas/2014/Special%2010/332-340.pdf
Pretreatments may make natural fibre hydrophobic or hydrophilic. Thus, if the natural fibre is gaining weight, then pretreatments of natural fibre must have rendered them hydrophilic. Water must have been gained from aqueous alkali media.
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