NaOH/urea预处理对棉纤维乙酰化的影响

Effect of NaOH/urea pretreatment on acetylation of cotton

以废旧棉纤维为原料,对其用NaOH/urea水溶液进行预处理,探讨了NaOH/urea预处理对棉纤维乙酰化的影响规律。NaOH/urea水溶液可使棉纤维表面发生显著变化,表面粗糙,呈絮状;使纤维素晶型发生变化,并且结晶度下降。研究分析表明,与原棉的乙酰化相比,经过NaOH/urea预处理后的棉纤维乙酰化时间更短,产量增多,取代度也明显提高。制备的醋酸纤维素与市售醋酸纤维素的各项性能接近,具有优异的应用价值。最利于棉纤维乙酰化的预处理条件为:反应温度为-15℃,NaOH/urea(质量分数)为7∶12,固液比为2∶50 g/mL。以醋酸纤维素为原料,氧化锌为改性剂,静电纺丝的醋酸纤维膜在紫外灯光照24 h后,亚甲基蓝溶液颜色的降解率均可达到99%以上,达到自清洁目的。

Using waste cotton fiber as raw material,the pretreatment with NaOH/urea aqueous solution was carried out,and the effect of NaOH/urea pretreatment on the acetylation of cotton fiber was discussed.NaOH/urea aqueous solution could significantly change the surface of cotton fiber,with rough and flocculent surface.The crystallinity of cellulose decreased and the crystallinity changed.The results showed that compared with the acetylation of raw cotton,the acetylation time of cotton fiber after NaOH/urea pretreatment was shorter,the yield increased and the degree of substitution significantly increased.The properties of the cellulose acetate prepared are close to those of the commercially available cellulose acetate.The pretreatment conditions most conducive to the acetylation of cotton fiber were the reaction temperature of-15℃,the NaOH∶urea(mass fraction)of 7∶12,and the solid-liquid ratio of 2∶50 g/mL.Moreover,cellulose acetate was used as the raw material,ZnO as the modifier,and the degradation rate of methylene blue solution could reach more than 99%after 24 h of ultraviolet light.