Effects of dehydration on the crystalline structure and strength of developing cotton fibers

Cotton fibers develop a significant crystalline structure during the first week of secondary wall synthesis. Marked increases in the degree of crystal linity, crystallite dimensions, and breaking forces occur between 20 and 30 days post-anthesis (dpa). As the fiber cells mature and dehydrate, the cyl indrical tubes collapse into convoluted ribbons. The dried fibers have lowe r breaking strength and higher breaking elongation. Wide-angle x-ray diffra ction and solid-state NMR results show lowered average crystallite dimensio ns with little change in the overall crystallinity upon dehydration. In dev eloping cotton fibers, dehydration appears to cause decrystallization, dist ortion 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, buil ds up stress at the molecular level, lowering strength and increasing crimp and elongation in the dried cottons.