表4-6為不同組成澱粉膜之楊氏模數(E)、抗張強度(σ)與延展性 (ε )。S為澱粉加熱糊化所形成之薄膜；MS為研磨後澱粉加熱糊化形成 薄膜，G則是添加10%甘油，N表示沒有經過加熱糊化直接成膜。
比較未添加研磨纖維素之薄膜， 楊氏模數(E)：MS> MS-N> MSG>
SG> S，而抗張強度(σ)：MS= MS-N= MSG= SG> S，S為機械強度最差 的，表示澱粉經由研磨後，不論是否有經過加熱程序，對於機械強度 上是有幫助的。另外MS-N(經過研磨後的澱粉，無加熱糊化)其機械強 度與MS幾乎相同，表示經由研磨可以代替加熱糊化程序，且研磨過的 澱粉懸浮液乾燥後即可成膜。由表4-6，也可以發現添加甘油可以提高 S的延展性，但是對MS卻沒有明顯的提升，可能是由於澱粉經由研磨 後，粒徑降解，產生許多的小分子，造成更多的OH鍵暴露出來，澱粉 分子與分子間形成更多的分子內氫鍵而結合，已不需要塑化劑幫助分 子間的結合，所以添加甘油對研磨過的澱粉薄膜並沒有明顯的影響。
添加11%研磨纖維素，所有薄膜延展性皆輕微下降，在楊氏模數與 抗張強度除了MS之外，其餘樣品皆上升，可能是由於11%纖維素添加 量對MS已經過多，纖維素反而阻礙了澱粉分子間的結合，造成MS薄
粉薄膜的機械強度，但添加量超過11%可能反造成機械強度的降低。
隨著奈米/次微米纖維素添加暫增加楊氏模數有明顯上升，可是抗 張強度降低，推測可能是纖維素含量過高，纖維素與澱粉分子結合阻 礙澱粉分子與澱粉分子間結合，而形成不穩定的結構。由於薄膜總固 形物含量不變，當纖維素的含量過高，造成澱粉含量相對減少，薄膜 延展性下降，脆度增加，薄膜尚未達到最大斷裂強度時，就已脆斷，
造成機械強度喪失。表4-6可以看出纖維素添加量大於11%之後延展性 呈現劇烈的下降，當超細纖維素添加量達到100%，延展性只有未添加 的1/10。Mondragon等人(2008)研究指出，纖維素結構具彈性可增加澱 粉薄膜的延展性，但是添加量過高纖維素形成網狀結構造成延展性的 降低。由薄膜表面顯微影像圖4-17 (c, f, i)與圖4-18 (c, f, i)也可以證明當 纖維素含量過高時，薄膜表面會出現由纖維素組成網狀結構，造成結 購缺陷，進而喪失機械強度。
表4-6 不同組成之澱粉膜機械強度
Table.4-6. Mechanical properties of starch base films at different component.
Milled cellulose (g/100g starch)
0 11 43 100 SG: Starch with glycerol by cooking,
MSG: Milled starch with glycerol by cooking MS-N: Milled starch uncooking
G: 10%glycerol (glycerol mass/ total dry mass)
*abcd: row within the same parameter; ABCD: column within the same parameter.
Each value presents Mean ± SD, n = 3.
伍. 結論
1. 澱粉經由介質研磨 120 分鐘後，開始有小於 1 μm 粒子產生
(99.86%)，粒數平均粒徑也從 3.5 μm (90 分鐘)降至 0.1 μm (120 分 鐘)，此時澱粉顆粒被破壞，小粒子懸浮於溶液中，造成粒徑劇烈 變化。
2. 纖維素研磨 30 分鐘之後，已經有小於 1 μm 粒子產生，其粒徑變化
已趨於穩定，研磨60 分鐘後不論是體積或是粒數平均粒徑也都無 顯著的變化。
3. 由掃描式電子顯微鏡 SEM 與穿透式電子顯微鏡 TEM 的顯微影像 可以觀察到澱粉與纖維素奈米微粒的存在，這可印證粒徑分析的結 果，證明經由研磨程序澱粉與纖維素都可降解奈米尺寸。
4. 澱粉與纖維素經由介質研磨後黏度上升，在相同加熱條件(糊化) 下，未經研磨的澱粉黏度(224.4 cP)遠大於研磨後澱粉(59.8 cP)，表 示介質研磨將降低澱粉的糊化度。其流體行為可用Herschel - Bulkley 經驗式描述。
5. 經由介質研磨，澱粉薄膜機械強度提高，且不需要經過加熱糊化程 序，這有助於生物性薄膜的應用。添加超細纖維素，機械強度亦有 改善，不過濃度若是超過11%，反而會降低其機械強度。
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柒、附錄 薄膜機械強度增加，楊氏模數(Young＇s Modulus)由743增加至1505 MPa；添加11%
的超細纖維素，澱粉膜由743 MPa 提高到1075 MPa，顯示介質研磨及超細纖維素 皆能改善澱粉薄膜機械強度。
關鍵字：澱粉、纖維素、介質研磨、薄膜、生物可分解
Influence of media milling and addition of ultrafine cellulose on the mechanical properties of starch-base film
Yu-Chin Shen, An-I Yeh
Institute of Food Science and Technology, National Taiwan University.
Abstract
Plastic materials are generally appled matters in food packaging; however, it resulted in an environmental impact or pollution. Recently, environment friend materials from natural and renewable resources, which are biodegradable and biocompatible, have received great attention. Starch, an edible material with thermoplastic characteristics, is suitable for film formation; however, the starch-based film is too brittle to processing.
Cellulose is an abundant polysaccharide in nature with high crystallinity, which has the potential to enhance the mechanical properties of starch-based film. In the present study, the influence of addition of ultrafine cellulose in starch-based film was studied by the application of media milling technique. Corn starch and cotton cellulose were fractured by media milling, and the static-light-scattering particle analyzer was applied to check the nano/submicron particles. Also, the scanning and transmission electron microscopes were used to observe the image of particles in nano/submicron scales.
The rheological properties of milled starch and cellulose suspension were evaluated by dynamic rheometer. The apparent viscosity of starch and cellulose suspension was increased after media milling. Addition of ultrafine cellulose drove the decrease of apparent viscosity of native gelatinized corn starch. But, the apparent viscosity of gelatinized milled starch increased with ultrafine cellulose addition. The suspensions appeared to be a shear-thinning fluid and can be described by Herschel–Bulkley model. The suspensions were used to prepared starch-based film using casting method. The mechanical properties of films were studies by texture analyzer with tensile test. The Young’s modulus increased from 743 MPa for the native starch film to 1505 MPa for the milled starch film. The Young’s modulus increased from 743 to 1075 MPa as the addition of ultrafine cellulose. increased from 0 to 11% (w/w, base on the weight of starch). Media milling as well as the addition of ultrafine cellulose can enhanced mechanical properties of starch based film.
key words: Starch, Cellulose, media milling, Film, Biodegradable
前言
奈米科技(nanotechnology)於二十世紀中期開始發展，材料奈米化後，比表面 積的大幅提高，表面能也隨之提高，常伴隨著一些特殊的物理化學行為，使材料 具有新的應用。製備奈米等級(nanoscale)材料的方法有二：一是以合成的方式由原 子或分子逐步合成而到達奈米等級，稱為｢由下而上(bottom up)｣；二是將巨觀材料 由大到小，降解(degradation)到奈米等級，稱為｢由上而下(top down)｣。在多種物理 降解法中，針對固體物質以介質研磨較具商業化潛力。
石油化學工業提供許多的高分子材料，可以生產各式各樣的塑膠製品，帶給 我們日常生活上許多便利，但是生物材料具有可生物降解、對環境友善、生物相 容性等優點，受到全球的重視。綠色化學(Green chemistry) 這個名詞始於90年代初 期，概念是利用新的技術方法及替代材料減少石化製品的使用，降低對於人類健 康及自然環境所造成之傷害 (Poliakoff and others, 2002)。
澱粉(starch)主要來自大宗穀物，價格便宜、產量豐富，且具有成膜特性，適
澱粉(starch)主要來自大宗穀物，價格便宜、產量豐富，且具有成膜特性，適