本文選題：漂白麥草纖維　切入點(diǎn)：纖維素微纖絲　出處：《陜西科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：纖維素微纖絲(cellulose microfibril,簡(jiǎn)稱CMF)作為一種可再生、性能優(yōu)良的新型納米生物質(zhì)材料,具有廣泛的應(yīng)用價(jià)值和市場(chǎng)前景。然而,在CMF的制備過(guò)程中需要消耗大量的機(jī)械能量對(duì)纖維細(xì)胞壁結(jié)構(gòu)進(jìn)行解離,并且機(jī)械解離作用也會(huì)對(duì)CMF產(chǎn)品的結(jié)構(gòu)和性能產(chǎn)生極大的影響。因此,本課題以漂白麥草纖維為原料,采用酶預(yù)處理結(jié)合高壓均質(zhì)法制備CMF。通過(guò)研究三種不同種類纖維素酶(復(fù)合纖維素酶、內(nèi)切葡聚糖酶和外切葡聚糖酶)對(duì)纖維細(xì)胞壁表面形貌和孔隙結(jié)構(gòu)的影響,以闡明酶預(yù)處理作用機(jī)理;在此基礎(chǔ)上,探討不同酶預(yù)處理對(duì)高壓均質(zhì)的作用效果以及處理?xiàng)l件對(duì)CMF結(jié)構(gòu)和性能的影響;將上述CMF用于薄膜制備,并進(jìn)一步研究CMF薄膜相關(guān)性能,以期實(shí)現(xiàn)CMF高效制備及產(chǎn)品應(yīng)用開(kāi)發(fā)。研究不同纖維素酶對(duì)纖維細(xì)胞壁表面形貌和孔隙結(jié)構(gòu)的影響。結(jié)果表明:經(jīng)三種纖維素酶處理后,纖維表面變得粗糙,細(xì)胞壁外層逐漸脫落,出現(xiàn)橫向溝槽和縱向裂隙,甚至切斷,其原因是由于酶分子從細(xì)胞壁外層逐漸作用于內(nèi)層,細(xì)胞壁結(jié)構(gòu)遭到破壞。同時(shí),當(dāng)酶用量較小時(shí),含有較多孔隙的細(xì)小纖維組分會(huì)優(yōu)先被酶水解,使三種酶水解后纖維總孔容和平均孔徑均減小;隨著三種纖維素酶用量的增加,酶水解向纖維細(xì)胞壁內(nèi)部的進(jìn)一步深入作用,產(chǎn)生新孔隙和破壞孔隙這兩方面的共同作用使纖維平均孔徑等參數(shù)有所變化,但整體上表現(xiàn)出增大的趨勢(shì)。將經(jīng)上述三種纖維素酶水解后的纖維樣品(纖維得率均為75%)再經(jīng)高壓均質(zhì)處理30次制備出CMF。結(jié)果表明:CMF仍具有天然纖維素的基本化學(xué)結(jié)構(gòu)和結(jié)晶結(jié)構(gòu);與纖維原料相比,CMF懸浮液具有良好的分散穩(wěn)定性,其熱穩(wěn)定性有一定程度的提高;與未經(jīng)酶預(yù)處理所制備的CMF相比,經(jīng)酶預(yù)處理所制備的CMF平均直徑由64.2nm顯著下降到28.5nm附近,長(zhǎng)度達(dá)幾微米到十個(gè)微米間,長(zhǎng)徑比明顯增加,經(jīng)酶預(yù)處理制備的CMF結(jié)晶度增加約18%,平均聚合度降低約48%,陽(yáng)離子需求量增加約22%,保水值增加約37%;與其他兩種酶相比,由于復(fù)合纖維素酶預(yù)處理后纖維具有更大的平均孔徑等參數(shù),經(jīng)高壓均質(zhì)更容易解離,所制備的CMF具有更高的結(jié)晶度和聚合度等,且成本相對(duì)低。因此,酶預(yù)處理可以顯著改善后續(xù)均質(zhì)處理效果,且復(fù)合纖維素酶的作用效果較好。采用復(fù)合纖維素酶對(duì)纖維進(jìn)行預(yù)處理,考察均質(zhì)次數(shù)對(duì)CMF結(jié)構(gòu)和性能的影響。結(jié)果表明:隨著均質(zhì)次數(shù)的增加,解離出來(lái)的微纖絲變得更細(xì)更均勻,平均聚合度逐漸減小,陽(yáng)離子需求量逐漸增加,懸浮液的穩(wěn)定性逐漸提高,而結(jié)晶度表現(xiàn)出先增加后逐漸減小的趨勢(shì);當(dāng)均質(zhì)次數(shù)超過(guò)20次后,CMF直徑和平均聚合度下降趨勢(shì)變緩,而陽(yáng)離子需求量增大趨勢(shì)也變緩,再增加均質(zhì)次數(shù)并不能達(dá)到顯著改善CMF性能的效果,反而增加機(jī)械能耗。對(duì)于不同的酶用量預(yù)處理,增加均質(zhì)次數(shù)會(huì)發(fā)生相似的變化趨勢(shì)。因此,酶預(yù)處理后再均質(zhì)20次能夠達(dá)到很好的作用效果。將上述不同CMF制備出一系列CMF薄膜,考察酶預(yù)處理及均質(zhì)處理對(duì)CMF薄膜力學(xué)性能和光學(xué)性能的影響。結(jié)果表明:隨著酶用量或均質(zhì)次數(shù)的增加,CMF薄膜的拉伸強(qiáng)度和斷裂伸長(zhǎng)率表現(xiàn)出先增加后減小的趨勢(shì),透光率表現(xiàn)出持續(xù)增加的趨勢(shì)。在酶用量為15 FPU/g,均質(zhì)次數(shù)為20次時(shí),CMF薄膜(厚度54μm)的拉伸強(qiáng)度和斷裂伸長(zhǎng)率達(dá)到最大值30.65MPa和1.61%,且透光率可達(dá)到約70%。
[Abstract]:The cellulose microfibrils (cellulose microfibril, referred to as CMF) as a kind of renewable, the excellent performance of the new nano biological material, has wide application value and market prospect. However, during the preparation of CMF need to consume a large amount of energy to mechanical dissociation of fiber cell wall structure, and mechanical dissociation will produce great the influence on the structure and properties of the CMF products. Therefore, the bleaching of wheat straw fiber as raw material, using the enzyme pretreatment combined with high pressure homogenization preparation of CMF. through the research of three kinds of cellulase (complex cellulase, endoglucanase and exoglucanase) effect on fiber cell wall surface morphology and pore structure, to clarify enzyme pretreatment mechanism; on this basis, to explore the influence of different enzyme pretreatment effect of high pressure homogenization and processing conditions on the structure and performance of CMF; The CMF is used for film preparation, and further study the related properties of CMF thin films, preparation and application of product development in order to achieve efficient CMF system. To study the effect of different cellulase on the fiber cell wall surface morphology and pore structure. The results show that the three kinds of cellulase treatment, the fiber surface roughness and the outer wall is gradually falling off there, the lateral grooves and longitudinal cracks, even cut off, the reason is because the enzyme molecules from the outer wall to the inner wall of the cell gradually, the destruction of the structure. At the same time, when the enzyme dosage is small, fine fibers containing more pore components is preferentially hydrolyzed to three kinds of fiber volume after enzyme hydrolysis and total pore the average pore size decreases with the increase of three; the amount of cellulase, the further effect of enzyme hydrolysis to fiber cell wall inside the common new pore and pore damage of these two aspects of the The average fiber diameter and other parameters change, but overall showed a tendency to increase. By the above three after hydrolysis of cellulose fiber samples (fiber yield were 75%) by high pressure homogenization treatment 30 times to prepare CMF. results show that the basic chemical structure and crystal structure of CMF still has natural cellulose; comparison with fiber materials, CMF suspension has good dispersion stability, to a certain extent improve its thermal stability; compared with untreated enzyme pretreatment prepared by enzyme pretreatment of CMF, the average diameter of the CMF prepared by 64.2nm was significantly decreased to near 28.5nm, the length of several microns to ten microns. The ratio of length to diameter increased significantly after enzyme pretreatment of CMF crystallization preparation degree increased by about 18%, the average degree of polymerization decreased by about 48%, the cationic demand increased by about 22%, the water retention value increased by about 37%; compared with the other two enzymes, because of complex cellulase pretreatment After the fiber has larger average pore size and other parameters by high-pressure homogenization to dissociate more easily, the prepared CMF has higher crystallinity and degree of polymerization, and the cost is relatively low. Therefore, enzyme pretreatment can significantly improve the subsequent homogenization effect, and the effect of compound cellulase cellulase were used for better. The pretreatment of fiber, the effects of homogenization times on the structure and performance of CMF. The results showed that with the increase of the number of homogeneous, microfibril dissociation became finer and more uniform, the average degree of polymerization decreases, the cationic demand gradually increased, the stability of suspensions increased gradually, while the crystallinity showed first increased gradually after decreased; when the homogeneous number more than 20 times, CMF diameter and average degree of polymerization decreased slowly, while the cationic demand increases trend is slow, and then increase the number of homogeneous and can not achieve significant To improve the performance of CMF, but increased the mechanical energy. For the different dosage of enzyme pretreatment, increased the number of homogeneous change trend similar. Therefore, enzyme pretreatment can reach 20 after homogenizing effect is very good. The different CMF prepared a series of CMF thin film, the effects of enzyme pretreatment and homogenization treatment on the mechanical and optical properties of CMF films. The results showed that with the increase of the amount of enzyme or the number of homogeneous CMF films, tensile strength and elongation showed first increased and then decreased, the transmittance showed increasing trend. The enzyme dosage was 15 FPU/g, the number of homogeneous 20, CMF thin films (thickness 54 m) tensile strength and elongation at maximum 30.65MPa and 1.61%, and the transmission rate can reach about 70%.

【學(xué)位授予單位】：陜西科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ352.79

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本文編號(hào)：1652556