细菌纤维素原位复合芳纶纳米纤维气凝胶的制备与性能分析

Preparation and properties of bacterial cellulose/aramid nanofiber in situ composite aerogel

摘要:

为提升细菌纤维素（BC）气凝胶的力学强度和阻燃性能，以芳纶纳米纤维（ANF）作为增强材料，与原位生长的BC复合制备了BC原位复合ANF（BC/ANF）气凝胶。采用FTIR、XRD和SEM对BC/ANF气凝胶进行结构表征，评价BC/ANF气凝胶的热性能、阻燃性能和拉伸断裂性能，考察了ANF含量（以BC培养基质量计，下同）对BC/ANF气凝胶结构和性能的影响。结果表明，相较于BC气凝胶，ANF含量5.0%的BC/ANF气凝胶（BC/ANF-5.0%）的拉伸强度（946.13 kPa）增加了6.42倍，断裂伸长率（19.61%）提高了6.00倍，极限氧指数（LOI）提高至22.38%，比表面积（78.2688 m2/g）增至1.42倍，导热系数降低至0.0352 W/(m·K)。ANF中的酰胺基团与BC中的羟基形成氢键，增强了二者的结合力；ANF在BC纤维网络中填充、缠绕，会产生范德华力促使相互吸引靠近，进而增强BC/ANF气凝胶的力学性能。ANF与BC纳米级的结合，有效抑制了左旋葡萄糖的形成和分解，促进了炭化，大幅度提升了BC/ANF气凝胶的热稳定性和阻燃性能。

Abstract:

Due to unique three dimensional network structure of superfine fibers, bacterial cellulose (BC) has gained great attention in various areas such as heat insulation, adsorption, energy storage, bioactive scaffold and etc. Low mechanical strength and flammability are bottlenecks in the application of BC aerogel. Therefore, it is necessary to improve flame retardancy and mechanical strength of BC aerogel. In this paper, the BC/aramid nanofibers (ANF) composite aerogel was prepared with in situ grown BC and aramid nanofibers. The structures of BC aerogel and BC/ANF aerogel were characterized by Fourier transform infrared spectrometer, X-ray diffractometer and scanning electron microscope. The thermal properties, flame retardant properties and tensile fracture properties of aerogels were analyzed. The effects of ANF amount on the structure and properties of BC/ANF aerogels were investigated. The results show that compared with BC aerogel, the tensile strength is enhanced by 6.42 times, the elongation at break (19.61%) has increased by 6.00 times, the limiting oxygen index (LOI) of BC/ANF aerogel is increased to 22.38%, the specific surface area is enhanced by 1.42 times and the thermal conductivity is decreased to 0.0352 W/(m·K) at the mass fraction of ANF of 5.0%. The amide groups in ANF form hydrogen bonds with the hydroxyl groups in BC, enhancing the binding force between the two. ANF fills and entangles in the BC fiber network, generating van der Waals forces that cause them to attract and approach each other, thus enhancing the mechanical properties of the BC/ANF aerogel. The nanoscale combination of ANF and BC effectively inhibits the formation and decomposition of levoglucose, promotes carbonization, and significantly improves the thermal stability and flame retardant properties of the BC/ANF aerogel.