Study On The Sturture And Peoperty Of Bast Fiberswithuntreated And Chemical Degumming

There are many kinds of natural fibers such as hemp, jute and sisal that consist of different proportions of cellulose, hemicelluloses, lignin, pectin and other impurity. What makes the fiber stiff is the existence of lignin, therefore they need to take degumming treatment before used. However, all of the degumming methods have certain limitation during the manufacturing process and don’t obtain good effects. In order to optimize treatment process and guide fiber degumming treatment, it is necessary to find a better degumming characteristic index.The main purpose of chemical degumming is to remove lignin, pectin and impurity from fiber and improve the proportion of cellulose. The structure and property of jute, sisal, kenaf and hemp before and after chemical degumming have been researched. The results of SEM, FTIR, Fiber strength and Bend test are as follows:(1) With the increase of alkali concentration, the fiber fineness reduces gradually, surface become smoother, the quantity of pectin separated from bundle fibers increases. When the concentration is too high, alkali destroys cellulose in fibers, resulting in fiber surface damage and excessive degumming. At the same time, fiber surface becomes rugged, which has an influence on surface smoothness and glossiness. Meanwhile, it is important to note that treatment temperature and time have a deeply effect on fiber fineness and glossiness, so the treatment temperature and time need to be controlled in proper level.(2) The amount of-OH at fibers decrease firstly and then increase with the concentration/time increase. When the concentration is13g/L, the amount of-OH in jute and sisal is smallest, while for kenaf the concentration is10g/L.(3) Chemical treatment has huge influence on S/G ratio of fibers lignin. With the increase of alkali concentration and treatment time, the S/G ratio of S-lignin fiber of jute, sisal, kenaf decrease firstly and then increase. As for hemp fiber, the S/G ratio increase firstly, then decrease and increase lastly.(4) The breaking strength of hemp fiber gradually increases with the increase of concentration. However, for jute and kenaf, the change tendency is complex.(5) After treatment of different alkali concentration, the critical load value and initial modulus value gradually decreases. According to the results, the flexural rigidity value of hemp fiber is rather small, which is between0and13. While the flexural rigidity value of jute and kenaf is high, it reaches dozens of times higher than hemp.(6) According to the dynamic contact angle test of sisal fiber, it can be found that the initial contact angle and spreading time of sisal fiber gradually decrease with the alkali concentration/time increase. After alkali treatment, the wettability of sisal fiber improves a lot.