Effect of concentration n rheological properties of media-milled cellulose

本研究主要探討不同濃度纖維素經濕式介質研磨後，對纖維素懸浮液流變性質之影響。實驗所採用的材料為棉花纖維素，其體積平均粒徑為33.19 micrometer，藉由濕式介質研磨將纖維素下降至奈米/次微米等級，配合粒徑分析、流動測試、動態測試、顯微觀察，研究濃度對產品流變性質、介質研磨的影響。 將原料纖維素懸浮液配製成1, 3, 5, 7, 9, 11 %，以粒徑0.8 mm之球形釔鋯珠作為研磨介質研磨180分鐘後，纖維素的體積平均粒徑依濃度分別大幅下降至0.896、0.870、0.804、0.774、0.773、0.769 micrometer，而奈米/次微米的體積百分率也都在68 %以上。 將不同濃度纖維素以動態流變儀進行流動測試與動態測試。將所得的流動曲線進行分析，懸浮液黏度隨纖維素濃度增加而增加，隨剪切速率增加而下降，屬切變致稀性流體，其流體行為可用Williamson 模型描述。在動態頻率掃描發現經研磨後的纖維素懸浮液屬於黏彈性物質，濃度5、7、9、11 %的耗損正切和頻率無關屬黏彈性固體，而濃度1、3 %則分別在1、100 rad/s開始趨向黏彈性流體。 在顯微觀察部份，以穿透式電子顯微鏡(TEM)觀察研磨過的纖維素懸浮液後，發現確實有奈米及次微米纖維素顆粒存在。In this research, the rheological properties of media-milled cellulose suspension at different cellulose concentration had investigated. The raw cotton cellulose with volume mean diameter 33.19 micrometer was the experiment material. The diameter of cellulose was reduce to nano/submicron scale by wet media milling technology. To characterize the rheological properties influenced by cellulose concentration the particle size distribution(PSD), flow test, oscillation test and morphology were performed. Raw cellulose suspension 400 mL was prepared at content atom of 1, 3, 5, 7, 9, 11 % to 400 mL deionized water. Those suspensions were milled by media, YTZ(yttria-stabilized tetragonal zirconia) bead with average diameter 0.8 mm. After 180 min milling, there are significant reduction on volume mean diameter, which are 0.896, 0.87, 0.804, 0.774, 0.773, 0.769 micrometer respectively. And all the volume percentage of nano/submicron particle are more than 68 %. Media-milled suspension with different cellulose concentration were measured by dynamic rheometer by flow test and oscillation test. The viscosity of suspension increased with the concentration, but decreased with increasing shear rate. The suspensions appeared to be shear-thinning fluid and be described by Williamson model. Media-milled cellulose suspension are viscoelastic material and the loss tangent of 5, 7, 9, 11 % suspension were independent on frequency, but 1, 3 % tend to be viscoelastic fluid on 1, 100 rad/s. TEM photo showed the presence of nano and submicron cellulose particle in media-milled cellulose suspension.摘要 IIbstract III錄 V目錄 VII目錄 IX.前言 1.文獻回顧 2.1纖維素 2.2奈米科技 7.3介質研磨 9.3-1介質研磨原理 10.3-2主要影響研磨效益的因素 13.4 粒徑量測 14.4-1穿透式電子顯微鏡 16.4-2掃描式電子顯微鏡 16.4-3動態光散射 16.4-4靜態光散射 17.4-5 粒數平均粒徑與體積平均粒徑 18.5 流變學 20.5-1 流體分類 20.5-2震盪測試 26.材料方法 30.1材料 30.2設備 30.3實驗流程及步驟 32.4原料懸浮液配製 33.5介質研磨 33.6冷凍乾燥 35.7密度量測 35.8顯微鏡樣品製備 35.9纖維素研磨後的體積膨脹測量 35.10纖維素乾物重測量 36.11粒徑分析 36.12流變性質量測 37.12-1靜態測試 37.12-2動態測試 37.結果討論 39.1 纖維素粒徑分析 39.1-1 原料粒徑 39.1-2研磨轉速對粒徑之影響 41.1-3研磨介質對產物粒徑之影響 42.1-4纖維素濃度對粒徑之影響 43.2 研磨前後纖維素的密度 51.3 流動性質分析 52.3-1 纖維素懸浮液的流動曲線 52.3-2 流體模型回歸 55.4 纖維素研磨後的體積膨脹效應 59.5 動態測試 62.6 顯微觀察 66.結論 68.參考文獻 7