Effects of Dehydration on the Crystalline Structure and Strength of Developing Cotton Fibers

Abstract

Cotton fibers develop a significant crystalline structure during the first week of secondary wall synthesis. Marked increases in the degree of crystallinity, crystallite dimensions, and breaking forces occur between 20 and 30 days post-anthesis (dpa). As the fiber cells mature and dehydrate, the cylindrical tubes collapse into convoluted ribbons. The dried fibers have lower breaking strength and higher breaking elongation. Wide-angle x-ray diffraction and solid-state NMR results show lowered average crystallite dimensions with little change in the overall crystallinity upon dehydration. In developing cotton fibers, dehydration appears to cause decrystallization, distortion of crystal surfaces, and increased disorder in the intercrystal and interfibril regions, driven by removal of water during cell collapse and by the formation of new intermolecular secondary bonding. This, in turn, builds up stress at the molecular level, lowering strength and increasing crimp and elongation in the dried cottons.