超低浓度酸水解制备纤维素纳米纤丝的初步研究

以漂白阔叶木浆为原料,通过控制浓度0.1%左右硫酸溶液(以下简称超低酸)水解温度和水解时间以及后续机械球磨时间制备不同特性的纤维素纳米纤丝(CNF),考察了不同过程参数对CNF得率的影响,并使用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、热重分析仪(TGA)和纳米粒度仪分析了CNF的表面形貌、结晶度、热稳定性及粒度均一性变化。结果表明,水解温度由100℃增加到140℃,CNF得率降低了37.6个百分点,CNF的聚合物分散性指数(PDI)数值逐渐减小,CNF中长纤维和块状纤维逐渐减少,当水解温度达到140℃时,CNF长度约100 nm,分布均匀;而CNF的结晶度随水解温度的增加呈先升高后略微降低的趋势;水解时间由1 h增加到3 h,CNF得率从62.8%下降到49.8%,CNF的PDI数值和结晶度值均呈现先上升后下降规律,当水解时间达到3 h时才能获得直径约100 nm左右的CNF;球磨时间由8 h增加到24 h,CNF的直径均已达到100 nm,CNF马尔文粒度的PDI数值不断上升,CNF颗粒均一性下降。球磨16 h制备的CNF热稳定性提高。

Preparation of Cellulose Nanofibrils by Ultra-low Acid Hydrolysis

In this paper,the effect of ultra-low acid hydrolysis pretreatment on the properties of cellulose nanofibril(CNF)prepared by me chanical ballmilling was studied using bleached hardwood pulp as raw material.By varying hydrolysis temperature and time,and the follow ing ball milling time,the yield of CNF was determined.SEM,XRD,TG and nanoparticle size analyzer were used for characterization of the surface morphology,crystallinity,thermal stability and particle size changes of CNF.With the increase of hydrolysis temperature from 100℃to 140℃,the yield of ball milled CNF decreased by 37.6 percent age points,the PDI value of CNF gradually decreased,and the medium and long fibers of CNF gradually decreased.When the hydrolysis temperature reached 140℃,the length of CNF was about 100 nm and had uniform distribution,while the crystallinity of CNF fibers increased first and then decreased slightly with the increase of hydrolysis tempera ture.With the increase of the hydrolysis time from 1 h to 3 h,the yield of CNF prepared by ball milling time decreased from 62.8%to 49.8%.The PDI and crystallinity values of CNF both increased first and then decreased.When the ball milling time reached 3 h,the diam eter of CNF was about 100 nm.With the increase of ball milling time from 8 h to 24 h,the diameter of all of CNF prepared reached 100 nm,the PDI value of the Malvern particle size of CNF kept increasing and the uniformity of CNF particles decreased continuously.The ther mal stability of CNF was improved after ball milling for 16 h.