螯合自组装制备生物基阻燃牛皮纸及作用机理

Preparation of Bio-Based Flame-Retardant Kraft Paper by Chelating SelfAssembly and Its Flame-Retardant Mechanism

提高木质纤维材料的阻燃性能、减少对石化基氮磷阻燃剂的使用,在拓展木基材料的同时提高改性木质材料的环保性能具有重要的研究意义。文中利用植酸与壳聚糖,结合无机金属离子Ca螯合的形式在纸张表面以层层螯合自组装制备了生物基高效阻燃涂层。层层螯合阻燃处理后,牛皮纸K-7在垂直燃烧测试时形成了长度仅为29.5 mm的炭层,其极限氧指数相对于对照组提高了17.9%,总热释放量降低了15.4 k J/g,阻燃处理后样品在600℃时的残炭质量显著提高,且阻燃处理后牛皮纸的挺度与撕裂度均得到提升;其燃烧后形成了含有P,N,Ca等元素高石墨化程度的阻燃层,其中含有P=O,P_(2)O_(7)^(2-)等特征官能团。植酸、壳聚糖及Ca^(2+)通过静电吸附及螯合作用在纸张表面形成了层状生物基阻燃层,避免了阻燃处理对纸张强度的影响,减少了亲水基团的暴露,从而降低了阻燃处理造成的材料的吸湿性。在受热时,阻燃层通过气相和凝固相阻燃相结合的方式发挥阻燃功效,有效地赋予了木质纤维材料的阻燃性能,避免了对石化基阻燃剂的依赖。

Improving the flame retardancy of lignocellulose fibers materials and reducing the use of petrochemical nitrogen and phosphorus flame retardants have important research value in expanding wood-based materials and improving the environmental protection performance of modified wood materials. Layer-by-layer chelation selfassembly was prepared on the surface of kraft paper to form a flame-retardant coating, combined with the form of inorganic salt Cachelation. The flame-retardant and mechanical properties of kraft paper before and after flameretardant treatment show that the treated kraft paper K-7 forms a carbon layer with a length of only 29.5 mm during the vertical burning test. Compared with the Control, the limiting oxygen index(LOI)of K-7 is increased by 17.9%and the total heat release is reduced by 15.4 kJ/g. Besides, the stiffness and tearing performance of kraft paper after flame retardant treatment were improved. The analysis of functional groups and micro morphology show that the flame retardant coating on the surface of K-7 contains -NH2group. In addition, the strength of the characteristic peaks of P=O and -HPOcontained in the coating change. At the same time, a flame retardant layer with high graphitization degree having P, N, Ca and other elements was formed after combustion, including P = O, P_(2)O_(7)^(2-) and other characteristic functional groups. Phytic acid, chitosan and Ca^(2+) formed a layered bio-based flame retardant layer on the surface of kraft paper through electrostatic adsorption and chelation. When heated, the flame-retardant layer exerted its flame-retardant effect through the combination of gas-phase and solid-phase flame-retardant, which effectively imparts flame-retardant properties to lignocellulosic materials and avoids dependence on petrochemicalbased flame retardants.