成人做爰免费视频免费看_成人a级高清视频在线观看,成人a大片在线观看,成人a大片高清在线观看,成人av在线播放,一a一级片,一级黄 中国色 片,一级黄 色蝶 片,一级黄色 片生活片

作者： Liheng Chen,   Junyong ZHU,   Carlos Baez,   Peter Kitin and   Thomas J Elder  

 

 

摘要：Here we report the production of highly thermal stable and functional cellulose nanocrystals (CNC) and nanofibrils (CNF) by hydrolysis using concentrated organic acids. Due to their low water solubility, these solid organic acids can be easily recovered after hydrolysis reactions through crystallization at a lower or ambient temperature. When dicarboxylic acids were used, the resultant CNC surface contained carboxylic acid groups which facilitate functionalization and dispersion in aqueous processing. Carboxylic acid group content was 0.1 – 0.4 mmol/g for CNC produced from a bleached eucalyptus kraft pulp (BEP) using oxalic acid at concentrations of 50 – 70 wt%. Onset thermal degradation temperature for the CNC was increased to 322°C from 274°C for the feed BEP fibers, compared with 218°C for CNC produced from the same feed fibers using conventional concentrated sulfuric acid hydrolysis. The low strength (high pKa) of organic acids also resulted in CNC with longer lengths of approximay 275 – 380 nm and higher crystallinity than those produced using mineral acids. Fibrous cellulosic solid residue (FCSR) collected from acid hydrolysis was an excellent feedstock for producing CNF through subsequent mechanical fibrillation with low energy input. The ability to recover the organic acids using a conventional and commercially proven crystallization method makes these organic acids uniquely suited for sustainable and green production of cellulose nanomaterials. The resultant CNC and CNF with high thermal stability and large aspect ratio are excellent for bio-composite applications.