Characterizing the Noncellulosics in Developing Cotton Fibers

Abstract

Surface wetting measurements and several analytical techniques including FTIR/ATR, DSC, TGA, and pyrolysis-GC/MS are used to characterize the noncellulosic components of developing cotton fibers as intact components of the fiber structure. Water contact angle measurements are most sensitive to the presence of hydrophobic compounds on the surfaces of cotton fibers of all ages and to their removal by alkaline scouring. In general, FTIR/ATR, DSC, TGA, and pyrolysis-GC/MS provide clear evidence of specific noncellulosic components in developing cotton fibers through the onset of secondary celt wall synthesis. Waxy compounds are evident by their melting endotherms in DSC thermograms, carbonyl bands in FTIR spectra, and mass spectra in the untreated developing fibers between 12 and 17 dpa. Pectins are detected by. FTIR in the 14 dpa and mature fibers. FTIR/ATR measure ments indicate the presence of proteins in untreated fibers up to 16 dpa and water-rinsed fibers up to 18 dpa. The presence of proteins in 14 dpa fibers is also detected by pyrolysis-GC/MS data. Among the analytical techniques, only pyrolysis-GC/MS can detect the presence of noncellulosic compounds in 27 dpa fibers. Detection of noncellulosics by the other techniques diminishes as the proportion of cellulose rapidly increases with the onset of secondary cell wall synthesis.