竹浆纤维素纳米纤维对硝化纤维素膜的增强作用

为获得力学性能更好的硝化纤维素膜材料,对竹浆进行2,2,6,6-四甲基哌啶-1-氧基自由基(TEMPO)选择性催化氧化-超声处理,得到直径纳米级、长度微米级的纤维素纳米纤维(cellulose nanofibrils,CNFs)。采用N,N-二甲基甲酰胺(DMF)或DMF/H2O混合溶剂作分散剂,先后将硝化纤维素与酸化和未酸化的CNFs进行充分混合,在不同的分散剂条件下制备出CNFs增强的硝化纤维素膜,采用透射电镜(TEM)、热重(TG)、力学拉伸试验、动态力学热分析(DMTA)等测试表征了CNFs形态尺寸以及CNFs增强的硝化纤维素膜力学性能变化规律。结果表明,CNFs的直径为5～10 nm,长度为500～3000 nm;酸化与未酸化的CNFs在DMF中分散性均好于丙酮溶液;在DMF/H2O分散体系中水的体积分数达到20%时出现了CNFs团聚;在DMF分散剂体系中,加入酸化的CNFs制备出的复合膜拉伸强度为52.0 MPa,断裂伸长率为10.4%,显著高于空白样(36.6 MPa,8.4%)。

Enhancement of Nitrocellulose Membrane by Bamboo Pulp Cellulose Nanofiber

To obtain a nitrocellulose membrane with enhanced mechanical properties, cellulose nanofibrils(CNFs) with nanometer-diameter and micron-length were obtained by 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO) oxidation-sonication treatment of bamboo pulp. The N,N-dimethylformamide(DMF) and DMF/H₂O mixed solvent were used as dispersing agent. And the nitrocellulose was thoroughly mixed with the acidified or unacidified CNFs. CNFs-enhanced nitrocellulose membranes were prepared under different dispersion conditions. In addition, the morphological dimensions of CNFs and the change rule of mechanical properties of CNFs-enhanced nitrocellulose membranes were characterized by transmission electron microscope(TEM), thermogravimetric Analysis(TG), mechanical tensile test and dynamic mechanical thermal analysis(DMTA). Results shows that the diameter and length of CNFs are 5-10 nm and 500-3000 nm, respectively. The acidified and unacidified CNFs have better dispersity in DMF than in acetone. The agglomeration of CNFs occurs when the volume fraction of water in DMF/H₂O reaches 20%. Using DMF as a dispersant, the tensile strength and tensile elongation of the composite membrane prepared by adding acidified CNFs are 52.0 MPa and 10.4% respectively, significantly higher than those of the blank sample (36.6 MPa, 8.4%).