本研究分別以「酸水解法」、「臭氧降解法」與「機械研磨」等三種不同的分解方式,探討棉花纖維於不同降解方式下粒徑分布與降解條件的關係。 在酸水解法中,於酸濃度40 % [H2SO4:HCl=3:1(v/v)]、70℃水浴、超音震盪條件下,纖維經24小時降解,其體積平均粒徑由128.7 mm降至13.48 mm,而算數平均粒徑則由3 mm降至1.037 mm。 在臭氧降解法中,反應條件為:溫度80 ℃下、臭氧濃度分別為80 mg/min (反應20小時)與70 mg/min (反應28小時)下。結果顯示高臭氧濃度降解效果較佳且反應時間短,纖維之體積平均粒徑由128.7μm降至49.86μm;算數平均粒徑由3μm降至1.753μm。值得注意的是,小纖維顆粒很容易被降解為多醣或寡醣類之更小的物質。 棉花纖維在不同機械研磨降解的條件中(研磨介質大小0.8 mm、0.3 mm;轉速3000 rpm、3600 rpm),纖維之體積平均粒徑由128.7μm降至2.278μm;算數平均粒徑由3μm變成0.645μm。加快研磨轉速可以減少研磨時間與降低纖維粒子大小,而且當研磨粒徑小於該研磨條件所得粒子降解之極限,須適時增加研磨轉速或降低研磨介質大小。 綜合上述三種降解方式,可知機械研磨方法能免於接觸化學藥品的處理,沒有化學成分污染殘留的問題,且可減短研磨時間與降解效果佳;其中已有25% 的纖維粒子體積平均粒徑小於882 nm,算數平均粒徑小於475 nm。
In the present study the cotton cellulose were degraded for the preparation of nanoscale-cellulose particles by application of three methods: acid hydrolysis, ozonolysis and milling. The relations between the particle size distributions and the degrading methods were investigated. In the acid hydrolysis, the fiber suspended in an acidic solution (H2SO4:HCl=3:1(v/v)) and dealt by supersonic treatment in a water bath at 70 ℃. It resulted that the mean particle size in differential volume was ranged from 128.7 μm to 13.48μm in 24 hours, and its corresponding count mean diameter was 3 μm to 1.037μm. While in the ozonolysis, the cotton fiber was treated by the ozone with concentration 80 mg/min (20 hr) and 70 mg/min (28 hr), respectively, at 80℃. It showed that the rate of degradation was quick and efficient due to high ozone concentration, which resulted in smaller particles. Here, the mean particle size in differential volume was ranged in 49.86~128.7μm, and the count mean diameter was 1.753~3μm.. Note that the smaller particles can be further degraded to oligosaccharides in the ozonolysis. By the application of mechanical milling, the cellulose fiber was degraded to more smaller particle with higher efficiency in comparision with the previous two methods. The mean particle size in differential volume was ranged from 128.7μm to 2.278μm in 3 hours, and more than 25 % particles were smaller than 882 nm. The count mean diameter was from 3μm to 645 nm with more than 25 % particles being smaller than 475 nm. In general, mechanical milling shows the most powerful and efficient method to reach nanoscale-cellulose. As the same degree of degradation was demanded, ozonolysis and acid hydrolysis required longer reaction time to obtain nano-particles.
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