利用瀝乾法測量細菌纖維素含水量與乾燥後復水量

Abstract

細菌纖維素因其特殊的奈米纖維結構使其具有高孔隙度與高孔洞表面積，又因纖維素具親水性，因此具有高含水量 (water holding capacity, WHC)的特性，本實驗利用Chen (2015) 所提出之瀝乾法測量細菌纖維素之含水量，並將測量裝置加以改良。 實驗定義瀝乾時間間隔：∆T為水滴落下的時間間隔，當實驗滿足水滴持續∆T min不再落下則瀝乾實驗結束。本研究確立一瀝乾準則：瀝乾時間間隔 ∆T = 6 min, 纖維素面積A = 16 cm2，在此準則下測量細菌纖維素的含水量，其實驗結果能客觀地代表此纖維素的含水量。此時細菌纖維素含水量變異係數 (coefficient of variation)小於5 %，瀝乾時間不超過30 min且實驗過程中蒸發損失小於 1.5 %。 本研究利用已確立之瀝乾準則測量甘油/纖維素膜含有甘油水溶液之能力 (glycerol holding capacity, GHC)，實驗發現隨著甘油濃度增加，甘油/纖維素膜含有溶液的孔洞體積會略微增加，纖維素逐漸膨潤，導致GHC隨之增加。 利用瀝乾法測量熱風乾燥後之甘油/纖維素膜之復水量 (water rehydration capability, WRC)。實驗發現當甘油濃度大於10 wt %時，熱風乾燥後殘留在纖維素結構內的甘油能避免纖維素結構被破壞，使纖維素之復水量提升到未乾燥纖維素含水量的90 %以上。 熱風乾燥後之甘油/纖維素膜，其復水後之孔隙度與通透性相對於熱風乾燥纖維素有明顯的提升，孔隙度由96 %以下提升至 99.3 %以上，而其通透性由2*10-6 ~3*10-6 cm2/sec提升到6*10-6 ~6.5*10-6 cm2/sec，但兩者皆略小於未乾燥之纖維素。

Bacterial Cellulose (BC) of unique nano-fibers structure and strong hydrophilicity is noted for its high water holding capacity (WHC). In this study WHC was measured by a draining method proposed by Chen (2015) with a slight modification. Experimental results suggested that a convenient set of draining criteria: time interval between draining droplets (∆T) = 6 min and the size of BC (A) = 16 cm2 to measure. WHC would satisfactorily result in less than 5 % coefficient of variation, and evaporation loss is less than 1.5 % within 30 mins. Furthermore, GHC (glycerol holding capacity) of gly/BC membrane was measured via this draining method by soaking BC memebrane in glycerol solution of various concentrations. The results showed that as the concentration of glycerol solution increased, GHC of gly/BC increased. Meanwhile, as the concentration of glycerol solution increased, up to 12 % swelling effect was noted. As to WRC (water rehydration capability) of BC dried by hot air, the experimental results showed that the WRC of gly/BC (glycerol concentration 10 wt % or more) could retain at least 90 % of capability compared to only 5 % by hot-air dried BC and 20~40% by freeze-dried BC. The porosity of rehydrated gly/BC was higher than 99.3 % and the permeability was about 6*10-6 ~6.5*10-6 cm2/sec, which were slightly lower than never-dried BC, but far greater than the hot-air dried BC and freeze-dried BC.