The Extraction Of Corn Bract Cellulose And Preparation Of Cellulose Nanowhiskers

Renewable and biodegradable biomass resources are gaining more and more attention with the consumption of non-renewable resources, such as coal, oil and natural gas. Cellulose as an abundant biomass resources in nature, its application can effectively reduce the dependence on three major fossil fuels.In order to develop corn bracts biomass resources rationally, this paper summarizes the general research situation of corn bracts, extraction technology of corn bract fiber and several preparation methods of cellulose nanowhiskers. Then describes some nanowiskers’ application on reinforced material, electrical materials, medical materials and so on. In this paper, corn bracts as raw materials were used to extract corn bract fiber with chemical treatment, then they were used to prepare cellulose nanowhiskers with TEMPO selective oxidation. The main research contents include:(1) Corn bracts were characterized on their basic structures and performances. They were studied on thickness, strength, chemical composition, morphological structure and crystallinity by digital fabric thickness meter, electronic fabrics strength tester, Fourier transform infrared spectroscopy(FTIR), scanning electron microscope(SEM) and X-ray crystal diffraction(XRD).Experimental results show that the thickness, horizontal and longitudinal strength of corn bracts all reduce gradually from outer layer to inner layer, and longitudinal strength is 6-10 times than horizontal strength. Corn bract is mainly composed of cellulose, hemicellulose and lignin. The microscope images show that the surface of corn bract is rough and randomly distributed with holes. The single fiber in corn bract has irregular cross-section and high hollowness. X-ray diffraction analysis show corn bract has the crystal structure of celluloseⅠ, with crystallinity of26.65%.(2) The extraction processes of corn bract fiber were optimized. Through analysising concentration of chemical reagents and reaction time in the corn bract fiber extraction process,optimization scheme was made finally. In addition, the corn bract fiber obtained with optimal process was tested in chemical composition, morphological structure crystallinity and so on.Compared to corn bract, the fiber has higher cellulose content and lower hemicellulose and lignincontent. Due to the removal of impurities, corn bract fiber’ longitudinal surface is smooth. Its crystallinity is nearly twice higher than that of corn bracts, up to 50.55%.(3) The preparation of corn bract cellulose nanowhiskers. The corn bract fiber treated with optimal process was used as raw material, and TEMPO was introduced to selectively oxidze the fiber for preparing cellulose nanowhiskers. Then they were tested by Atomic force microscope(AFM), transmission electron microscopy(TEM), FTIR, XRD and thermogravimetric(TG).The corn bracts, corn bract fiber and corn bract cellulose nanowhiskers were compared on their structure and performance. The AFM pictures show that the shape of corn bract cellulose nanowhiskers is like needle with average length of 86.48 nm, average diameter of 6.90 nm. It is mainly composed of two chemical contents which are cellulose and hemicellulose. Because the cellulose crystal type was not destroyed in TEMPO process, corn bract cellulose nanowhiskers still present cellulose Ⅰ crystal type, with crystallinity of 53.86%. The initial degradation temperature of nanowhiskers is 200℃, and its thermal stability reachs to constant at 310 ℃.The abundant agricultural byproducts corn bracts were selected as raw material in this paper,and cellulose and nanowhiskers were extracted successfully. The research can provide certain theoretical and experimental basis for the preparation of cellulose nanocrystals. It is also useful for the comprehensive utilization of abundant agricultural byproducts resource.