Fine structure of carbamoylethylated and carboxyethylated cotton cellulosic fibers

Abstract

SynopsisThe fine structure of cotton cellulosic fibers carbamoylethylated and carboxyethylated at 30 and 2OoC in the presence of 3% and 20% sodium hydroxide was investigated by measuring moisture regain, water imbibition, x-ray photograph, degree of crystallinity, spacing, and crystallite size under dry and wet conditions. As carbamoylethyl and carboxyethyl substituents are introduced in amorphous regions of the samples reacted with acrylamide in 3% sodium hydroxide, the fine structure of the crystalline regions is not affected by the reaction. On the other hand, in the samples reacted in 2W0 sodium hydroxide, the substituents are introduced not only in amorphous regions but also in crystalline regions to make them disordered. Although spacing between ( l O i ) planes does not change, spacing between (101) planes increases by the reaction in 20% sodium hydroxide. Comparing crystallite sizes normal to (hkl) planes under dry conditions with those under wet conditions, it is supposed that cohesive forces between (101) planes are different from those between (107) planes, and the former is hydrogen bonds and the latter resemble Van Der Waals forces. As a result, carbamoylethyl and carboxyethyl groups are introduced selectively between (101) planes.

Thermal behavior of drawn acrylic fibers

“…2 The three major reactions taking place during the thermooxidative stabilization of polyacrylonitrile (PAN) in air atmosphere are cyclization of nitrile groups, dehydrogenation, and oxidation (oxygen uptake). 3 The reaction mechanism of the thermal-stabilization process of PAN in air and the effect of copolymerization have been reported by Shimada et al 4 with a combination of Fourier transform infrared (FTIR) and elemental analysis techniques. They suggested that these three reactions, that is, cyclization, dehydrogenation, and oxygen uptake occur almost simultaneously.…”