• additives;
  • degradation;
  • fibers;
  • processing


Hemp is cooked and bleached in alkali-H2O2 one-bath. The analysis of physical and chemical properties related to acid, alkali, and hydrogen peroxide about various types of components in hemp such as hemicelluloses and pectin, and lignin components makes it ascertained. In this one-bath process, alkali and H2O2 have cooperative effects to remove most proportions of the noncellulosic components efficiently. The additive MgSO4 and a stabilizer of H2O2 as auxiliary agents are introduced to protect cellulose from degradation and, meanwhile, they improve the efficiency of H2O2. The universal rotatable composite experiment design is employed to get the highly precise equation, in which the variables of NaOH and H2O2 concentrations, and the processing time are considered to be the main technological parameters of this alkali-H2O2 one-bath process. The residual gum content and residual lignin content of hemp fiber are the evaluation indexes. Based on regression equations, the figures are plotted to analyze the influences of parameters on the evaluation indexes; the optimization multicriteria mathematical model is simultaneously established to obtain the optimum parameters. Finally, an experiment is carried out to further test the acceptance of the calculated optimum values. It is shown that, for the hemp taken from Anhui Province of China, this alkali-H2O2 one-bath process can substantially remove gum and lignin from raw hemp. NaOH 10.5 g/L, H2O2 9.8 g/L, and the processing time of 127 min with 0.1% MgSO4 + 2.7 g/L stabilizer of H2O2 at 100°C are recommended to be the optimum parameters; then, a compromise is achieved among the lowest lignin content, the residual gum content, and the best strength and whiteness of hemp fiber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2279–2285, 2005