Study On Mechanical Degumming And Alkali-H₂O₂ One Bath Processing Of Hemp

Hemp fiber is the most prospective cellulosic fibre in the future. It has many natural healthcare functions such as good bacterial repellency & inhibition, good absorption-air permeability, shielding radiation, it is emollient, frash and comfortable. What's more, the hemp has the ecology-safe-productivity and end-product-recycling. So many experts believe that hemp is the ideal textile fibre and the most prospective cellulosic fibre in the future.Hemp, one of the oldest and most versatile plants, has been used about 5000 years ago, and it was used as a raw material source for the production of rope, canvas, textiles, paper and oil products. Now the researches on hemp have been extensive in recent years for it has advantages both ecologically and biologically for materials such as textiles, composites, paper and building materials etc. It is neutral for the environment, causes no allergies, shows antiseptic properties, high sorption capacity, collects no charges of static electricity, the pectin contained in the fiber protects against the UV radiation and is easy to dye. As a textile fiber, hemp provides all the warmth and softness of other natural textiles but with a superior durability seldom found in other materials. Hemp blended with other fibers easily incorporates the desirable qualities of mixture of textiles.However, hemp fibers consist of both cellulosic and noncellulosic substances, such as hemicellulose, pectin, lignin and wax, and these noncellulosic substances affect the spinning,weaving, dyeing, and finishing of hemp fibers, yarns and fabrics. So to make good use of hemp fibers, removal of the most noncellulosic components is a prerequisite problem.There exist several methods of hemp processing: bacterial, chemical and enzymatic methods. Bacterial processing depends on the weather, water quality, and other factors, and often results in inconsistent fiber quality. Enzymatic processing method was developed for flax in the 1980s, but may not be a feasible method for processing hemp fibers for their high lignin content and these enzymatic techniques have not been put into industry at present. So far, chemical processing method is still widely used for it can much better be controlled and adapted than other processing methods, and considerable research has focused on this method to improve the quality of fiber.A mechanical processing method is developed to remove the gums of hemp. This new method can save time and protect the environment because it processes the raw hemp by rollers only. It can remove about 30% gum of raw hemp.It is known that bleaching or similar processing can improve the appearance of fibers and hydrogen peroxide is often used to bleach the textile fibers.Earlier reports on the vast application of alkali-H2O2 one-bath process were employed in dyeing and finishing. In this paper, alkali-H2O2 one-bath process is introduced to treat hemp. And this method is designed on basis of analysis of the components in the hemp bast. Lignin, hemicellulose and pectins are targeted for effective removal.In this study, hemp is degummed and bleached inone-bath. Alkali and H2O2 work simultaneously to remove most proportions of the noncellulosic components efficiently. MgSC>4 and a stabilizer of H2O2 as auxiliary agents are introduced to protect cellulose from degradation and meanwhile to improve the efficiency of H2O2 greatly. The universal rotatable composite experiment design is employed to get the highly precise regression equations, in which NaOH, H2O2 concentration and the processing time are main technological parameters. The residual gum content and residual lignin content are the evaluation indexes. Based on these 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 NaOH 10.5g/L, H2O2 9.8 g/L and the processing time 127 minutes with 0.1% MgSO4 + 2.7g/L stabilizer of H2O2 at 100°C are the optimum parameters, and then the lowest lignin content, the residual gum content and the best strength and whiteness of hemp fiber can be achieved.