Study On Technic Of Ultrasonic And Ultraviolet Or Freeze-heat Of Hemp Degumming

Hemp fibers is known as "green fiber" in the world, clothing and mattress made of hemp fibers have such functions as moisture absorption, air permeability, comfort, heat dissipation, mildew resistance, bacteriostasis, radio resistance, UV-ray provention, noise absorption and so on. The clothing made of hemp fibers could have many advantages that general spinning materials do not have. With growing concern on environmental issues, hemp fibers increasingly take people's attraction because of their unique properties with good drapability, fast moisture absorption and wet dissipation, antiseptic deodorization, UV-ray prevention and weak pricking feeling relative to other bast textiles, so hemp fibers are taken seriously.Degumming is the primary problem for hemp fibers as the textile materials.Compared with ramie, the pectin content of hemp is greater than 40%, which increases the difficulty of degumming with the combination of complex structure, the bond between pectin and cellulose, and the high content of lignin with complex structure. Degumming stand or fall, will directly affect the supple, dyeing and a series of following functional problems of hemp fibers. In general, the residual gum should be around 2%.In hemp spinning industry technology, degumming is also the bottleneck problem, and even infuluence profits, output value and so on.At present, chemical ways are mainly used for hemp degumming, needing much more water, chemical reagent and long time and causing pollution of the environment. In this paper, in view of the above questions, it uses degumming of physics and chemistry to simplify the process, protect environment, reduce consumption and save energy.The structure and performance of cellulose and non-cellulose components containing lignin, pectin and hemicellulose were discussed, and the effects of degumming process and chemical reagents on the content of cellulose and non-cellulose were analyzed. The degumming mechanisms of ultrasonic oscillation, UV radiation and freezing-shock heating treatment were discussed, adding ultrasonic and UV radiation method. It uses degumming of ultrasonic oscillation, UV radiation and freezing-shock heating treatment to reach proper gum residual and reduce pollution extremely.Hemp fibers before and after degumming were characterized by field-emission scanning electron microscopy (SEM), thermo gravimetric analysis (TGA) and infrared spectroscopy (IR). The changes of overall performance and structure and chemical composition before and after degumming of hemp fiber were analyzed. It shows that:1) The results indicated that the pectin most fell off from the fiber surface after degumming by ultrasonic oscillation and ultraviolet radiation. The surface morphology of fiber bundles could be observed and the fibers were thoroughly separated, being white and soft. Some minor grooves on the fibers'surface were beneficial for the adhesion of functional additives. The compositions of hemp fibers changed without lignin and hemicellulose. The characteristic peaks of lignin and hemicellulose tended to disappear in IR spectra. The residual gum rate reached to 4.59%.2) After degumming by ultrasonic oscillation and freezing-shock heating treatment, there was a small amount of pectin on fibers surface, and most of lignin was removed. Then the residual gum rate was 3.79% after ammonia cooking.3) After cooking the breaking strength, length and fineness of hemp fibers reduced to some extent, but still meeting the requirements of spinning.