Kinetics of swelling of cotton fibers in aqueous ethylenediamine solutions using moisture regain data

Kinetic studies of swelling of cotton cellulose with 75% (w/w) EDA solution have been carried out. Three rates of the reaction were observed in the temperature range 10–35°C: first, the very fast rate (k₁) lasting for about 10 s; second, the extremely slow rate (k₂) lasting for 30–50 s; and third, once again a fast rate (k₃), k₁ being faster than k₃. k₁ was attributed to the swelling action of EDA–monohydrate in amorphous regions of cellulose; k₂ was assigned to the penetration of swelling species into crystallities accompanied by breakage of H bonds in these regions; and k₃ was assigned to the opening up of the crystallites. Activation energy values confirmed this trend. At higher temperatures (35–55°C), the middle rate k₂ merged with k₃, giving only two rates, k₁ and k₂₊₃, as the higher temperatures brought about simultaneous diffusion of swelling agent into, and decrystallization of, the crystalline portions of cellulose. EDA solution of 65% (w/w) concentration gave only two rates: the initial fast rate assigned to the swelling of the amorphous portion, followed by a slow one, operating in mesomorphous regions of cellulose, without any appreciable decrystallization. This was atributed to the important fact, viz., the absence of EDA–monohydrates in the solution.