甲酸水解法清洁制备纳米纤维素及其功能性应用和展望

纳米纤维素是一种绿色可再生的生物基纳米材料,由于其特殊的物化性质备受学术界和工业界的广泛关注。清洁高效的纳米纤维素制备方法的建立对实现其规模化生产和商业化应用尤为重要。本文主要综述了甲酸水解法清洁制备纳米纤维素的研究进展。与传统的无机强酸水解法相比,甲酸水解法制备纳米纤维素的主要优点包括：甲酸易回收和回用,可确保整个制备过程的清洁;甲酸在水解纤维素的同时,也与纤维素表面羟基发生反应,从而在纤维素表面引入酯基,同步实现纳米纤维素的制备与表面改性;通过反应条件的控制,可实现纳米纤维素形貌和性质的可控制备。此外,本文还概括介绍了甲酸水解法制备的纳米纤维素的功能性应用和展望。由于其特殊的表面性质,甲酸水解法制备的纳米纤维素在构建异质膜器件、Pickering乳液,以及橡胶和塑料复合材料加填等领域具有广阔的应用前景。     

可控制备纳米微晶纤维素

以纳米纤维素为原料,通过多尺度微观结构设计,形成具有材料梯度和结构梯度的多层次结构,制造出具有超强机械性能的纤维素基复合材料将具有巨大的潜力。制备出性能可控的纳米纤维素原料是实现纳米纤维素功能化利用的前提条件。本研究采用浓硫酸水解法,在一定范围内可控制备了具有特定尺寸的纳米微晶纤维素,在此过程中研究了浓硫酸水解时间对制备的纳米纤维素得率、磺酸基团含量及纤维素降解产物的影响。     

花生壳纳米纤维素的制备与表征

本文以花生壳为原料,在氢氧化钠碱解和亚氯酸钠漂白预处理基础上,通过硫酸水解方法制备花生壳纳米纤维素。采用扫描电镜、透射电镜、红外光谱、X-射线衍射和热失重分析对花生壳纳米纤维素的表征进行研究。结果表明,通过碱解和漂白处理,花生壳半纤维素和木质素被大量去除,花生壳纤维素含量由43.84%增加到86.56%,纤维素直径为10~30μm;花生壳纳米纤维素呈棒状结构,长度为90~210nm,直径为5~25nm;花生壳纳米纤维素制备过程中纤维素结构并未遭到破坏;结晶度随制备过程逐渐增高,花生壳纳米纤维素结晶度为74.71%,呈典型的纤维素I型晶型;花生壳纳米纤维素的起始热分解温度较低,当温度达到500℃时,花生壳纳米纤维素的残余率大于30%。所制备的花生壳纳米纤维素有望在可降解复合材料中得到应用。     

纤维素纳米纤维-丁苯胶乳复合材料的制备与表征

采用共混法制备不同纤维素纳米纤维含量的纤维素纳米纤维-丁苯胶乳复合材料,并通过拉伸性能、扫描电镜、热重分析以及红外光谱检测该复合材料的相关性能。分析结果表明:纤维素纳米纤维能均匀分散在丁苯胶乳溶液中,对丁苯胶乳有较好的补强效果;和丁苯胶乳相比,制得复合材料的裂断伸长率增大,弹性变好;但纤维素纳米纤维的加入对丁苯胶乳热稳定性的影响不明显。     

玉米秸秆纳米纤维素制备的工艺优化

该研究采用弹射式蒸汽闪爆法(High density steam flash-explosion,HDSF)制备玉米秸秆纳米纤维素纤维,研究蒸汽闪爆压力、蒸汽闪爆时间、Na OH浓度对玉米秸秆中的半纤维素、纤维素、木质素含量的影响。以单因素试验为基础,根据中心组合实验设计原理,将纳米纤维素含量作为响应值,通过响应面分析法进行试验设计与数据分析。试验发现：弹射式蒸汽闪爆法制备纳米纤维素的工艺参数为：蒸汽闪爆压力值为1.5 MPa,蒸汽闪爆时间为285 s,氢氧化钠浓度为0.4 mol/L,纳米纤维素含量预测值46.02%,实验验证值为45.88%,与预测值接近,说明预测模型可靠性较高,此时半纤维素含量13.50%,木质素含量11.78%,证明方法合理可行。影响纳米纤维素得率的因素依次为蒸汽闪爆压力值>蒸汽闪爆时间>氢氧化钠浓度。弹射式蒸汽闪爆法有利于分离相互缠绕的半纤维素、纤维素、木质素,具有效率高、成本低、绿色无污染等优点。并且运用此方法制备的纳米纤维素具有较小粒径和良好的水溶性,这使得玉米秸秆纳米纤维素拥有更好的应用前景。     

纳米纤维素的制备及其对纸张增强作用的研究

本文以漂白杨木浆为原料,采用硫酸水解与高速机械搅拌相结合的方法制备纳米纤维素,探究其最佳制备条件及对纸张的增强效果。结果表明:制备纳米纤维素的优化条件为:硫酸浓度55%,反应温度55℃,反应时间2h,高速分散时间为10min。在此条件下,所制得的纳米纤维素的得率为74.8%,且微观形态最好。所制备纳米纤维素的长度为68~175nm、宽度为21~55nm。添加所制的纳米纤维素对纸页的抗张强度、撕裂度、耐折度提高非常明显,且增强效果随着纳米纤维素添加量的增加而增加。     

椰子中果皮微晶纤维素的制备工艺

本研究以椰子中果皮为原料,采用硝酸-乙醇法提取纤维素,并将提取的纤维素水解制备微晶纤维素;采用分光光度法测定纤维素含量,滴定法测定微晶纤维素得率。单因素实验结果表明椰子中果皮纤维素提取的适宜工艺条件为:80℃下水浴回流2h、料液比为1∶20（g/m L）、酸醇比为1∶3、该条件下,提取所得纤维素含量为75.24μg/m L。以提取的椰子中果皮纤维素为原料制备微晶纤维素的适宜工艺条件为:水解温度100℃、水解时间70min、盐酸质量分数7%、料液比1∶15（g/m L）,在此条件下,微晶纤维素得率为97.50%;将制备出来的微晶纤维素进行了红外表征。本工艺能够较好地提高椰子中果皮的应用价值。      

气相生长碳纤维/聚酰胺6纳米纤维增强聚乳酸复合材料

研究了气相生长碳纤维（VGCF）的表面功能化处理及其在聚合物中的分散性。通过静电纺丝,制备了不同VGCF含量的聚酰胺6（PA6）纳米纤维毡,并以VGCF/PA6纳米纤维增强聚乳酸（PLA）得到复合材料。研究发现,经过混酸处理的VGCF水溶液,在加入聚合物前后各用超声波处理1小时,VGCF的分散性较好;表面活性剂处理VGCF,明显提高了其在聚合物溶液中的分散效果。在PA6/甲酸溶液中加入VGCF后,纤维毡的力学性能增强,在纺丝液中VGCF质量分数为0.03%时,断裂强度达到最大值(14.68MPa）。随着VGCF/PA6纳米纤维含量的增加,复合材料的断裂强度先增大后减小,并在VGCF/PA6质量分数为7.39%时达到峰值(25.80MPa）。     

椰子中果皮微晶纤维素的制备工艺

本研究以椰子中果皮为原料,采用硝酸-乙醇法提取纤维素,并将提取的纤维素水解制备微晶纤维素;采用分光光度法测定纤维素含量,滴定法测定微晶纤维素得率。单因素实验结果表明椰子中果皮纤维素提取的适宜工艺条件为:80℃下水浴回流2h、料液比为1∶20(g/m L)、酸醇比为1∶3、该条件下,提取所得纤维素含量为75.24μg/m L。以提取的椰子中果皮纤维素为原料制备微晶纤维素的适宜工艺条件为:水解温度100℃、水解时间70min、盐酸质量分数7%、料液比1∶15(g/m L),在此条件下,微晶纤维素得率为97.50%;将制备出来的微晶纤维素进行了红外表征。本工艺能够较好地提高椰子中果皮的应用价值。     

纳米微晶纤维/聚乙烯醇复合薄膜的制备及性能

采用蔗渣为原料制备出粒径大小为20～50nm的纳米微晶纤维素(NCC),并用溶胶/凝胶方法制备出不同NCC含量的纳米微晶纤维素/聚乙烯醇(NCC/PVA)复合薄膜,重点研究了NCC加入量对复合薄膜综合性能的影响。结果表明,NCC的加入能使薄膜的热稳定性有所提高,当NCC的添加量在0.5%时,聚乙烯醇薄膜的拉伸强度提高了115%,吸水性降低了12.0%,断裂伸长率减少了68%。     

聚吡咯纤维素纳米晶复合导电材料的制备及其性能表征

摘要：通过硫酸水解法由棉纤维制备纤维素纳米晶,再采用原位化学氧化法,在纤维素纳米晶表面进行吡咯的原位聚合,成功制得包裹聚吡咯的纤维素纳米晶复合导电材料。产物的相貌、结构和性能的研究表明：聚吡咯－纤维素纳米晶复合导电材料表现出核壳结构,纤维素纳米晶与聚吡咯间存在着较强的相互作用有利于聚吡咯均匀地包覆纤维素纳米晶;有机掺杂剂DBSNa由于分子体积大,降低了分子间作用力,其电导率不如无机掺杂剂NaCl,但是热稳定性和比电容好于NaCl,并且显著提高了复合体系的电化学容量,做为超级电容器具有良好的应用前景。     

改性纳米TiO2对纤维素包装膜性能及结构的影响

本文利用氯化锂/N,N-二甲基乙酰胺(LiCl/DMAc)溶解纤维素,并与改性、未改性的纳米TiO2进行共混,采用溶胶-凝胶法制备可降解纤维素包装膜.通过红外光谱对改性前后纳米材料的结构进行表征,测试纤维素包装膜的拉伸强度及断裂伸长率,并进行热失重分析;使用扫描电镜和原子力显微镜观察其表面结构.结果表明:改性纳米TiO2比未改性纳米材料在纤维素膜中的分散更均匀,当改性纳米TiO2与纤维素混合比例为0.5∶100时,纤维素包装膜的拉伸强度和断裂伸长率分别为25.6MPa和125％,较加入未改性纳米TiO2的纤维素膜拉伸强度提高了1.45倍,断裂伸长率是原来的1.35倍.     

Nanocellulose preparation via a dissolution and regeneration process and application to wood‐plastic composites as toughness enhancement

In this work, nanocellulose (NC) was prepared by a new route consisting of dissolution of cellulose in phosphoric acid followed by regeneration in water. To facilitate the dissolution, the cellulose was pre-treated with aqueous solution of urea. Although the regenerated cellulose from water had been in nanoscale, its size could be further reduced through ball milling. The composition, structure, and morphology of the materials from different preparation stages were studied by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. NC was then incorporated into the HDPE based wood-plastic composites (WPCs) in a skillful way to guarantee its good dispersion. The influence of addition content of NC on the mechanical and thermal properties of WPCs was investigated comprehensively. WPCs incorporated with NC exhibited an obvious increase in impact strength compared with those without NC. In addition, the Rockwell hardness, Vicat softening temperature and thermal stability of WPCs incorporated with NC were also correspondingly improved. The effect of ball milling on the size of nanocellulose was also investigated. The application results showed that the NC prepared without ball milling was more efficient in enhancing the toughness of WPCs.

     

Preparation and Properties of Cellulose/Tamarind Nut Powder Green Composites

Using biopolymer cellulose as the matrix and tamarind nut powder (TNP) obtained from agricultural waste of tamarind nuts as the filler, the green composites were made. Cellulose was dissolved in environmental friendly solvent of aq. 8 wt. % Lithium hydroxide and 15 wt. % urea which was precooled to ?12 ° C. To the cellulose solutions, TNP was added in 5 wt. % to 25 wt. % of cellulose separately. Each solution was evenly spread on glass plates and the wet composites were prepared by regeneration method using ethyl alcohol coagulation bath. The wet films were dried in air at room temperature. The dried composite films were characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis and also tested for their tensile properties. The tensile strength and the % elongation at break of the composites were higher than those of the matrix and increased with TNP content. While the matrix had a tensile strength of 111.8 MPa, the cellulose/TNP composite loaded with 25 wt.% TNP possessed a tensile strength of 125.4 MPa (12% increase). Though the thermal stability of the composites was lower than cellulose matrix, all the composites were stable up to a temperature of 350 °C.     

Surface modification of nylon fabric and its optimization for improved adhesion in rubber composites

Nylon-6,6 fabric was treated with formic acid for surface roughening and was subjected to Resorcinol Formaldehyde Latex treatment for making rubber composites. Physicochemical effects of surface roughening of nylon were evidenced using scanning electron microscope (SEM), Fourier Transform Infrared spectroscope (FTIR) and differential scanning calorimeter (DSC). Further, the treatment effect on interfacial adhesion was quantified through peel strength test. The process parameters of the formic acid treatment were optimized using Box-Behnken method through geometrical surface roughness obtained through Kawabata evaluation system for micro-surface roughness of nylon to ensure good interfacial adhesion with rubber. Surface modification conditions of 11.2% formic acid concentration, 70 °C temperature and 30 min time were found to yield optimum condition at which surface roughness (SMD) was found to be of 20.1 μm. SEM analysis confirmed the presence of heterogeneous appearance like cracks, etches and micro-rough surfaces on the treated Nylon-6,6 fibre surface. FTIR analysis showed changes in –C = O stretching and –N–H stretching. No significant change was noted in the DSC curve. The peel strength between the rubber and treated fabric was improved to 150% in warp and 124% in weft directions, respectively with reference to the control fabric.     

纤维素/海藻酸钙共混纤维的制备及其性能

针对纤维素纤维易燃烧的问题,首先以离子液体1-烯丙基-3-甲基咪唑氯盐([AMIM]Cl)为溶剂共溶解纤维素与海藻酸,然后以氯化钙溶液为凝固浴,采用干喷湿法纺丝制备了纤维素/海藻酸钙共混纤维。研究了纤维素/海藻酸钙组分比对共混纤维结构和性能的影响。结果表明:纤维素/海藻酸钙共混纤维结构致密,二者之间存在氢键相互作用;虽然海藻酸钙的存在使共混纤维的力学性能降低,但当海藻酸钙质量分数为30%时,共混纤维的断裂强度为123 MPa,离火自熄时间仅为1.1 s,表现出优良的离火自熄特性;纤维素/海藻酸钙共混纤维的吸湿平衡回潮率为7.33%~7.75%,具有类似再生纤维素纤维的优良吸湿性能与服用性能。     

有机溶剂法麦草木质素的化学特性研究

用不同浓度的乙酸-水、甲酸-乙酸-水、甲醇-水及乙醇-水溶液处理脱蜡的麦草,获得的木质素采用FT-IR、~1H-NMR、~(13)C-NMR及化学法研究其化学特性,结果表明,有机酸溶液比有机醇溶液脱木素作用更加广泛,能选择性降解麦草中的纤维素、木质素及半纤维素。甲酸对木质素的溶解有显著影响。随着乙酸或甲酸浓度的增加,愈创木基结构单元增加,木质素缩合。有机醇处理获得的木质素中,含有几乎等量的非缩合型愈创木基和紫丁香基结构单元及少量的对羟苯基结构单元。     

细菌纤维素/聚己内酯微米纤维复合膜的制备及性能

为制备模拟细胞外基质结构的微纳尺度复合材料,利用静电纺丝技术制备了聚己内酯(Polycaprolactone,PCL)微米纤维膜,通过与纳米尺度的细菌纤维素(Bacterial Cellulose,BC)原位复合,制备了BC/PCL复合纤维支架。采用扫描电镜、红外光谱分析、X射线衍射分析对材料的形貌、结构进行了表征。通过单轴力学测试对复合材料力学性能进行了研究,并利用成纤维细胞对复合材料的生物相容性进行评价。结果表明:通过静电纺丝法制备的PCL微米纤维的平均直径,随聚合物纺丝液质量分数的增加有增加的趋势,BC与PCL微米纤维复合后,BC纳米纤维渗透入微米纤维膜内部,实现微纳米纤维较好的复合。红外光谱分析和X射线衍射分析进一步证明BC和PCL微米纤维成功复合。PCL微米纤维膜复合BC膜后,相比PCL微米纤维膜增加了其断裂强度,同时复合支架无明显细胞毒性,可应用于生物医学领域。     

CuO/聚丙烯/乙烯-辛烯共聚物复合熔喷非织造材料的制备及其吸油性能

为高效经济地处理油品泄漏引起的污染问题,利用聚丙烯(PP)与乙烯-辛烯共聚物(POE)共混后制备复合熔喷非织造材料,然后在其表面负载纳米氧化铜(CuO)进行疏水改性.对改性前后非织造材料的形貌、结构、水接触角、吸油和力学性能等进行测试.结果 表明:负载纳米CuO后,CuO/PP/POE复合熔喷非织造材料的结晶度下降,熔...