Influence Of Steam Explosion On Morphology And Physico-chemical Characteristics Of Cotton Stalk Fiber

The steam explosion of liginocellulose materials is an extremely complex processing, which contains numerous chemical reactions and changes in structure of fibers. This study, focus on cotton stalk fibers Treated by steam explosion. The effect of steam explosion on morphology and physico-chemical characteristics of cotton stalk fiber was investigated, so that the optimized processing parameters could be determined.The temperature of steam vapour, residence time, moisture content of raw material before steam explosion and severity which is a comprehensive parameter combined steam temperature and residence time are the main factors in this research. Coordinating different parameters and exploring the effect on fibers morphology and structure after steam explosion. The details effect is described as follow:As for residence time, fibers after steam explosion turn to be decentralization and chaos with increasing residence time. The cell wall become shrink, curve, crack and many small droplets configuration drops formed on the surface of cell wall. When the steam temperature is 210℃, residence time is 13 min, droplets processing under this condition is very small. The degree of crystallinity of cellulose increased with longer residence time. At the same time, the yield of solid material and hemi-cellulose decreased. But the cellulose yield is not much difference with residence time increase, remain near to 40%. Lignin and extractives increased. That means the degradation degree become extensive with prolong of residence time, the cellulose saccharide, xylose and different acid in the liquid which come out from the steam explosion increased.For the moisture content of raw material, The fiber after explosion are fluffy and chaos with high moisture content(220%), but dense when the raw material moisture content(MC) are low as 55%. As the micro-configuration for single cell described, crack are critical for the high moisture content, and with big droplets on the surface of cell wall; in general raw material with 55% MC have high crystallinity; there is a coteau at residence time: 9 min, MC:220%, Temperature: 210℃between high MC and low MC. When the residence time are shorter than 9 min, the material with low MC have a greater fiber yield than high MC material, but when the residence time are longer than 9 min, the trend is converse. High Cellulose yield with 55% MC material, but low hemi-cellulose yield. When the severity is 4.08, it means:under this condition, temperature goes up, the residence time reversely become short, higher temperature and shorter residence time. Fiber after processing have not obviously difference, which means the severity have deterministic role in de-fibration. The transferred lignin carbohydrate complex congregate to big droplets under lower steam temperature, but when the steam temperature goes up, the lignin carbohydrate complex will disperse evenly on the cell wall surface. The relative crystallinity decreased as the increase of processing temperature, which proves that massive degraded substance are residual in the fiber. Cellulose and lignin content increase, but hemi-cellulose decreased. Which mean high steam temperature and short processing time is a good environment for preserve cellulose, and benefit to hemi-cellulose degrading. Under this severity, high temperature is good for produce fiber.In the whole steam explosion processing, lignin experienced water infiltrate, soften, degradation, erupting and re-conglormeration.Comprehensive analyze the configuration of fiber, chemical components, micro-figure, chemical group and the requirement for raw material to manufacture fiber board, a conclusion come out:the steam severity is 4.08, temperature is 210℃, residence time is 7 min, moisture content is 55% or the severity is 4.35, temperature is 210℃, residence time is 13 min, moisture content is 220%, are the best parameter for fiber produce for bindless fiber board. But the latter is the best choice for not only the binding quality but also energy resource saving in bindless fiber board industry.