Kinetics of swelling of cotton fibers in aqueous ethylenediamine solutions using X‐ray diffraction data

Abstract

AbstractKinetics of swelling of cotton cellulose with 75% (w/w) ethylenediamine (EDA) solution has been studied using X‐ray diffraction. Apparently, the swelling reaction proceeds at three different rates, all obeying the first‐order kinetics. The first rate (k1), which is the fastest one, is hypothetically attributed to the swelling action of EDA–monohydrate in the amorphous region of cellulose; the second rate (k2), which is extremely slow, is responsible for the penetration of swelling species into the crystallites, accompanied by breakage of the hydrogen bonds in these regions; and the third rate (k3), which is faster than k2 but slower than k1, has been assigned to the decrystallization of the crystalline regions. The increase in temperature of swelling (from 10°C to 55°C) brought about increase in all these three rates with shortening of their respective periods. Thus, at temperatures of 35°C and above, k2 and k3 merge, giving a combined rate (k2+3). These results were confirmed from the data on the activation energy values. The changes in crystallinity were comparatively less, when 65% (w/w) EDA solution was used for swelling cotton fibers. The ineffectiveness of 65% (w/w) EDA solution was explained on the basis of the absence of powerful swelling species in the solution. An attempt has also been made to examine the kinetic data on the basis of the model for cotton fiber fine structure consisting of crystalline elementary fibrils and surfaces or regions of varying extents of hydrogen bonding.