预处理对麦秸纤维板性能的影响及机理研究

Effects and mechanism of different pretreatments on the properties of wheat-straw medium density fiberboard

比较了热水软化、乙酸、亚硫酸盐和木聚糖酶等不同预处理方法对麦秸中密度纤维板性能的影响;采用傅立叶红外光谱(FTIR)、电子自旋共振波谱(ESR)等分析在不同预处理过程中麦秸纤维表面官能团、纤维表面自由基的变化,并揭示其作用机理。结果表明:与热水软化预处理相比,其他3种预处理对麦秸纤维板的性能均有一定的改善,尤其是内结合强度改善明显。其中木聚糖酶预处理使纤维表面—OH的含量最高,平均长度最长,长宽比最大,所得纤维板的强度最高;亚硫酸盐预处理因磺化作用使得麦秸纤维表面自由基浓度最高;而乙酸的作用则是由于降低了pH和缓冲容量,有利于脲醛树脂的固化,使得结合强度提高。

In this paper, the effects of various wheat straw pretreatment methods （hot-water, acetic acid, sulphite, and xylanase） on the properties of straw fiberboards bonded with UF resin were investigated. The results showed that pretreatment with xylanase was the best in terms of properties of the final boards. Since hemi-cellulose was partially degraded, and fiber cell became easy to swell, fiber quality was accordingly improved while excessive destroying of xylanase pretreated fibers avoided. The fibers had the longest average fiber length and the largest length-to-width ratio. On the other hand fibers from sulphite treatment released the most free radicals since straw lignin was activated. The fibers pretreated by acetic acid demonstrated that acid pretreatment did not remove straw wax and silicon dioxide, but it changed pH value and buffering capacity of the surface of the straws. This helped straw to be easily bonded with UF resin. The boards showed better properties using above three methods than that using hot-water softening especially the internal bond （IB） strength.