本文選題：酶處理 + 機(jī)械法�。� 參考：《南京林業(yè)大學(xué)》2015年碩士論文

【摘要】：納米纖維素具備比強(qiáng)度高、熱膨脹系數(shù)低、易化學(xué)改性、成本低、可再生、可生物降解、環(huán)境友好等特性,是一種理想的用于增強(qiáng)聚合物的材料。使用納米纖維素改性的聚合物材料具備良好的生物可降解性,可以替代傳統(tǒng)的石油化工產(chǎn)品等一些不能生物降解的聚合物材料。傳統(tǒng)的酸解法制備納米纖維素水解劇烈,對(duì)環(huán)境影響大,對(duì)反應(yīng)設(shè)備要求高,因此開(kāi)發(fā)一種簡(jiǎn)單、低成本和對(duì)環(huán)境友好的納米纖維素制備方法極為重要。本研究以紙漿為原料分離纖維素,利用提純纖維素酶使纖維素在溫和的條件下水解,并結(jié)合研磨和高壓均質(zhì)機(jī)械方法制備納米纖維素,利用現(xiàn)代分析技術(shù)表征其形態(tài)和性能;利用制備的納米纖維素添加到聚乙烯醇樹脂中制備納米纖維素/聚乙烯醇復(fù)合薄膜,研究其力學(xué)性能、光學(xué)特性和電學(xué)特性,結(jié)果表明:(1)最佳木聚糖酶處理?xiàng)l件下,產(chǎn)物中纖維素相對(duì)含量為95.45%;最佳堿處理?xiàng)l件下,產(chǎn)物纖維素相對(duì)含量高達(dá)98.12%。堿處理提純的纖維素純度更高。(2)紙漿原料的纖維素結(jié)晶度Cr I值為77.50%。在最優(yōu)木聚糖酶處理?xiàng)l件下產(chǎn)物Cr I達(dá)到81.93%;在最佳堿處理?xiàng)l件下,紙漿中纖維素結(jié)晶度Cr I值上升到85.89%。木聚糖酶處理和堿處理都沒(méi)有使纖維素的晶型發(fā)生轉(zhuǎn)變。(3)經(jīng)硫酸銨分級(jí)沉淀法提純之后,內(nèi)切葡聚糖酶的比活力顯著提高,由0.135IU/mg提高到0.245IU/mg,并且具有高達(dá)84.57%的酶活回收率。纖維素酶和提純纖維素酶的最佳酶添加量均為30IU/g底物。在同樣的酶添加量條件下,提純纖維素酶的酶解得率要低于纖維素酶的酶解得率;無(wú)論是提純后的纖維素酶還是纖維素酶混合酶體系作用于堿法纖維素原料,酶解得率均隨著酶解時(shí)間的增加而變大,在24h之后增長(zhǎng)極為緩慢。(4)經(jīng)過(guò)提純纖維素酶處理后,纖維素晶型仍然保持為纖維素I型。纖維素的結(jié)晶度值隨著酶解時(shí)間的延長(zhǎng)而增大;通過(guò)提純纖維素酶處理,纖維素的平均聚合度有顯著下降。纖維素分子的尺寸粒徑大小都有很大程度的降低。(5)提純纖維素酶處理,以及研磨高壓均質(zhì)處理,都沒(méi)有破壞纖維素的化學(xué)結(jié)構(gòu)和熱穩(wěn)定性。酶處理前后和機(jī)械處理后的三種纖維素在水分散體系中其表面顯電負(fù)性。經(jīng)最優(yōu)處理工藝條件的提純纖維素酶處理之后和后續(xù)機(jī)械研磨均質(zhì)處理,纖維水分散體系的Zeta電位絕對(duì)值分別由16.63m V增大到17.16m V和18.25m V;(6)經(jīng)提純纖維素酶處理以后,纖維素原料纖維長(zhǎng)度急劇減短,被酶水解為短棒狀的纖維,長(zhǎng)徑比小;纖維表面多處出現(xiàn)了較為明顯的斷裂和缺口。再經(jīng)研磨結(jié)合高壓均質(zhì)處理后纖維絲束之間互相纏繞內(nèi)部纖維團(tuán)聚,直徑達(dá)到納米級(jí)別。(7)納米纖維素對(duì)PVA樹脂有增強(qiáng)作用。納米纖維素在納米纖維素/聚乙烯醇復(fù)合薄膜中添加量的增加會(huì)使得薄膜復(fù)合材料的拉伸強(qiáng)度增大和斷裂伸長(zhǎng)率降低。納米纖維素的添加量達(dá)到5%時(shí),復(fù)合材料的拉伸強(qiáng)度增大到105MPa,比純PVA樹脂的拉伸強(qiáng)度相比提升了10.2%;斷裂伸長(zhǎng)率降低到12.0%,相比純凈的PVA樹脂的斷裂伸長(zhǎng)率降低了57.3%。與純凈PVA薄膜相比,納米纖維素/聚乙烯醇復(fù)合薄膜的透光性下降,由95.92%降低到納米纖維素添加量為5%時(shí)的88.2%,減弱幅度較低。納米纖維素的添加量增加會(huì)引起納米纖維素/聚乙烯醇復(fù)合薄膜表面電阻率的增加,并對(duì)其相對(duì)介電常數(shù)和損耗角正切值等介電性能有影響。
[Abstract]:Nanoscale has the characteristics of high specific strength, low thermal expansion coefficient, easy chemical modification, low cost, renewable, biodegradable, environmental friendly and so on. It is an ideal material for strengthening polymers. The polymer materials modified by nanoscale have good biodegradability and can replace traditional petrochemical products. It is very important to develop a simple, low cost and environmentally friendly nanoscale cellulose preparation method, which is very important for the preparation of nanosulcose, which is simple, low cost and environmentally friendly. This study uses pulp as raw material to separate cellulose and use purification of cellulose. Cellulose was hydrolyzed under mild conditions and nanoscale was prepared by grinding and high pressure homogenization. The morphology and properties of the cellulose were characterized by modern analytical techniques. Nanosol / polyvinyl alcohol composite films were prepared by adding nanoscale to the polyvinyl alcohol resin. The mechanical properties and optical properties of the nanofibers were studied. The results showed that: (1) the relative content of cellulose in the product was 95.45% under the optimal xylanase treatment conditions, and the purity of cellulose was higher than that of 98.12%. alkali treatment under the best alkali treatment conditions. (2) the Cr I value of fibrin crystallinity of pulp raw material was 77.50%. at the optimal xylanase treatment conditions. The lower product Cr I reached 81.93%. Under the optimum alkali treatment conditions, the crystallinity of cellulose Cr I in pulp increased to 85.89%. xylanase treatment and alkali treatment. (3) after purification by ammonium sulfate fractionation, the specific activity of the endosanase was significantly increased from 0.135IU/mg to 0.245IU/mg. The optimum enzyme activity of cellulase and purified cellulase is 30IU/g substrate. The rate of enzymatic hydrolysis of cellulase is lower than that of cellulase in the same amount of enzyme addition. The cellulase or cellulase mixed enzyme system after purification is used in the alkali process. Cellulose raw material, the rate of enzymatic hydrolysis increased with the increase of enzyme hydrolysis time. After 24h, the growth of cellulose was very slow. (4) after purification of cellulase, the crystalline form of cellulose remained the I type of cellulose. The crystallinity of cellulose increased with the prolongation of enzymolysis time; the average degree of polymerization of cellulose by purification of cellulase and the average degree of polymerization of cellulose were obtained. The size of the cellulose molecules decreased greatly. (5) the purification of cellulase treatment, and the high pressure homogenization treatment, did not destroy the chemical structure and thermal stability of the cellulose. The surface of the three cellulose in the water dispersive system after and before and after the enzyme treatment was the best. The absolute value of Zeta potential of fiber water dispersion system was increased from 16.63m V to 17.16m V and 18.25m V, after purification of cellulose enzyme treatment and subsequent mechanical grinding. (6) after purification of cellulase, the fiber length of cellulose fiber was shortened sharply, and the enzyme was hydrolyzed into short rod like fiber, and the ratio of length to diameter was small. There are more obvious breakages and gaps on the surface of the fiber. The fiber bundles are intertwined with the fiber bundles after the grinding and high pressure homogenization. The diameter reaches the nanometer level. (7) the nano cellulose has an enhanced effect on the PVA resin. The addition of nanofibric to the nanofibrine / polyvinyl alcohol composite film will be increased. The tensile strength and elongation at break of the film composite were increased and the elongation at break was reduced. The tensile strength of the composite was increased to 105MPa when the amount of nanoscale was 5%, compared with the tensile strength of the pure PVA resin, the elongation at break was reduced to 12%, and the elongation at break of the pure PVA resin decreased by 57.3%. and purity. Compared with the PVA film, the transmittance of nanoscale / polyvinyl alcohol composite film decreased from 95.92% to 88.2% when the nano cellulose was added to 5%. The increase in the addition of nanoscale would cause an increase in the surface resistance of the nano cellulose / polyvinyl alcohol composite film, and the relative dielectric constant and loss angle of nanoscale cellulose / polyvinyl alcohol composite film. The dielectric properties such as tangent value have an effect.
【學(xué)位授予單位】：南京林業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ352.1;TB383.1

【參考文獻(xiàn)】

相關(guān)期刊論文 前2條

1 藺燾;郭文靜;方露;王正;;3種方法計(jì)算棉稈纖維素結(jié)晶度的比較分析[J];東北林業(yè)大學(xué)學(xué)報(bào);2013年02期

2 汪麗粉;李政;賈士儒;張健飛;;細(xì)菌纖維素性質(zhì)及應(yīng)用的研究進(jìn)展[J];微生物學(xué)通報(bào);2014年08期

相關(guān)博士學(xué)位論文 前1條

1 杜敏;酶水解漂白針葉木纖維結(jié)構(gòu)和性能的研究[D];陜西科技大學(xué);2013年

，

本文編號(hào)：2073899