壳聚糖改性化学纤维的新方法及其微观分析

用H2CO3溶解壳聚糖凝胶后以物理涂覆的形式包裹在化学纤维表面的方法将疏水性的化学纤维改性成亲水性纤维,增强了化学纤维的可抄造性。结果表明,该方法切实可行,通过显微镜和SEM照片对涂覆壳聚糖前后的维纶纤维进行微观分析,发现在化学纤维表面形成的壳聚糖膜薄而均匀,同时增加了化学纤维的表面粗糙度,涂覆效果较好;通过接触角的变化说明纤维的亲水性得到改善;该方法还具有无残留物和对环境友好的优点。     

碳纤维表面特性及其在水中的分散性

对碳纤维的表面形貌、表面基团和表面电荷进行了分析,并就碳纤维长度、分散条件、分散剂种类和用量对碳纤维在水中分散性的影响进行了研究.结果表明,所用碳纤维表面粗糙,带有羟基、羰基等活性基团,表面负电荷密度约为20.3μmol/g;搅拌器打散碳纤维能提高其在水中的分散性,搅拌器内理想的浆液浓度为0.07%;加入APAM分散剂能改善分散,APAM适宜添加量为0.6%～0.8%.     

两亲改性碳纤维制备质子交换膜燃料电池用碳纸的研究

为了提高短切碳纤维在水中的分散性及碳纤维与后期浸渍树脂的相容性,对碳纤维进行了两亲表面处理:首先通过氧化处理使其获得亲水性官能团—OH及—COOH,在此基础上进一步接枝亲油基团,以获得两亲碳纤维,并将其制备碳纸。结果表明,两亲处理的碳纤维表面—OH含量可达8. 2%。在碳纤维表面改性过程中,铬酸氧化在提高碳纤维表面亲水性官能团的同时会降低碳纸的抗张强度;而接枝亲油性官能团能提高碳纤维与树脂的黏结能力,部分弥补了表面处理所造成的负面影响;碳纤维与树脂黏结力的提高有利于碳纸导电性的提高,两亲改性碳纤维制备的碳纸与未处理碳纤维制备碳纸相比电阻率降低了31. 4%,达到10. 5 mΩ·cm。     

天然高分子对化学纤维涂覆改性的新方法

介绍了采用天然高分子对化学纤维进行涂覆，从而改善化学纤维亲水性的方法。主要包括壳聚糖和海藻酸盐的溶胶一凝胶法。壳聚糖和海藻酸盐分子链上都含有大量的羟基等亲水性基团，利用它们的溶解性质可将其均匀地涂覆在化学纤维表面，从而对化学纤维进行亲水化改性。     

高分散水性碳纤维的制备

本研究以壳聚糖盐酸盐（CHI）和十二烷基磺酸钠（SDS）制备改性剂（CHI&SDS）,采用浸渍法对BHM3碳纤维进行表面改性,以提升BMH3碳纤维在水中的分散能力。系统研究了CHI/SDS质量比、CHI&SDS改性剂质量分数及纤维长度对改性BMH3碳纤维在水中分散性的影响,并通过X射线光电子能谱仪和动态接触角测试仪,对改性BMH3碳纤维化学结构和表面润湿性进行了表征。结果表明,BMH3碳纤维经过质量分数0.15%,CHI/SDS质量比=25∶1的CHI&SDS改性剂改性后,纤维长度5 mm的改性BMH3碳纤维在水中的分散率可达96.2%,相较于未改性碳纤维提升了87.5个百分点。改性BMH3碳纤维表面含氧官能团数量显著提升,水接触角明显降低,这是BMH3碳纤维分散性能改善的原因,也是成功实现高分散水性碳纤维制备的基础。     

碳纤维屏蔽纸制造过程中纤维分散性能的研究

通过不同浓度、不同分散剂以及纤维表面化学改性对碳纤维分散性影响的探讨,研究了碳纤维在水中的分散性能。研究结果表明、PEP与CPAM均能明显提高碳纤维的分散性,尤以CPAM为好;碳纤维经过表面化学改性后,表面产生更多的活性基团,进一步提高了纤维的分散性能。     

碳纤维的改性及其纸基功能材料性能的研究

为了提高碳纤维和所成纸基功能材料的性能,利用一定浓度的硝酸对碳纤维进行了改性。利用X射线衍射（XRD）、扫描电镜（SEM）等分析手段对改性后碳纤维进行分析。结果表明：随着改性的进行,纤维亲水性明显提高,碳纤维在水中的分散性得到改善;碳纤维的石墨特征几乎没有变化,但观察到纤维表面受到明显的侵蚀。对纸基功能材料的物理检测结果表明：随着改性时间延长和温度的提高,碳纤维纸的匀度得到明显的改善,抗张指数呈先增加后降低的趋势,电阻率呈逐渐增大的趋势。综合考虑纤维改性效果和碳纤维纸性能的变化,确定最佳改性温度为60℃,改性时间为90min,此时碳纤维纸的抗张指数为14.2N·m/g,电阻率为0.153Ω.cm。     

提高质子交换膜燃料电池用碳纤维纸均匀性的研究

以聚丙烯腈基短切碳纤维为原料,通过湿法成形工艺制备碳纤维纸（简称碳纸）原纸,利用现代分析仪器表征不同处理条件下碳纤维的表面形貌、化学结构及元素价态,观察不同处理条件下碳纤维的分散性及其制备的碳纸原纸的均匀性,研究了高温空气氧化处理的最佳工艺条件。结果表明,经过高温空气氧化处理后,碳纤维表面的氧元素和含氧官能团的含量均显著提高,碳纤维在水中的分散性明显改善,碳纸原纸的均匀性明显提高,电阻率的离散系数从0.22下降到0.05。因此,最佳高温空气氧化改性碳纤维的条件是氧化温度500 ℃、氧化时间2 h。     

不同化学处理对碳纤维分散及成纸性能的影响

通过联合Zeta电位、吸光度和数码图像分析,考察了碱性预处理和不同试剂表面处理对碳纤维分散性的影响,并以碳纤维配加纸浆制取纸样,检测纸张的物理强度和体积电阻率。实验结果表明:碱性预处理可改善碳纤维分散性,吐温-80和CPAM试剂都可显著提高碳纤维分散性及成纸抗张指数和电导率,但作用机理截然不同。吐温-80通过降低固液表面张力,提高水对纤维的润湿能力,改善碳纤维分散性;CPAM则是通过形成三维空间大网络絮体,阻止碳纤维的运动聚集,来改善其在纸浆中的分散。     

交联对壳聚糖-聚乙二醇-负离子皮革涂饰剂性能的影响

采用物理共混法制备了丙三醇(Glu)、戊二醛(Glu)、氧化石墨烯(GO)化学交联和物理交联(Heat)的壳聚糖-聚乙二醇-负离子(CS-PEG-NOI)复合涂饰剂。结果表明:交联可有效改善复合涂饰剂的性能,物理交联的交联程度较化学交联小,对其性能影响也较低。丙三醇交联可提升分散性与亲水性,但稳定性明显下降;戊二醛交联后,稳定性提升,分散性和亲水性下降;氧化石墨烯则可大幅提升分散性、稳定性,但亲水性大幅下降,成革物理机械性能大幅提升,透水汽性能下降;物理交联可小幅提升分散性,亲水性稍微降低。     

Influence of Hydrocolloids (Dietary Fibers) on Lipid Digestion of Protein‐Stabilized Emulsions: Comparison of Neutral,Anionic, and Cationic Polysaccharides

The impact of dietary fibers on lipid digestion within the gastrointestinal tract depends on their molecular and physicochemical properties. In this study, the influence of the electrical characteristics of dietary fibers on their ability to interfere with the digestion of protein‐coated lipid droplets was investigated using an in vitro small intestine model. Three dietary fibers were examined: cationic chitosan; anionic alginate; neutral locust bean gum (LBG). The particle size, ζ‐potential, microstructure, and apparent viscosity of β‐lactoglobulin stabilized oil‐in‐water emulsions containing different types and levels of dietary fiber were measured before and after lipid digestion. The rate and extent of lipid digestion depended on polysaccharide type and concentration. At relatively low dietary fiber levels (0.1 to 0.2 wt%), the initial lipid digestion rate was only reduced by chitosan, but the final extent of lipid digestion was unaffected by all 3 dietary fibers. At relatively high dietary fiber levels (0.4 wt%), alginate and chitosan significantly inhibited lipid hydrolysis, whereas LBG did not. The impact of chitosan on lipid digestion was attributed to its ability to promote fat droplet aggregation through bridging flocculation, thereby retarding access of the lipase to the droplet surfaces. The influence of alginate was mainly ascribed to its ability to sequester calcium ions and promote depletion flocculation.     

Enhancing the flame retardant of polyethylene terephthalate (PET) fiber via incorporation of multi-walled carbon nanotubes based phosphorylated chitosan

Phosphorylated chitosan (PCS) were first deposited on the multi-walled carbon nanotubes (MWNTs) surface via chemical modification to obtain functionalized MWNTs-based PCS (PCS-MWNTs). Then, a series of PET fibers with MWNTs or PCS-MWNTs were prepared via melt spinning. The microstructure and molecular structure of PCS-MWNTs were characterized by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy. The morphological structures, mechanical, thermal, and flame-retardant properties of the PET fibers containing MWNTs or PCS-MWNTs were analyzed by FESEM, therogravimetry, differential scanning calorimetry, cone and electronic tension meter method. The results showed that MWNTs were coated with PCS. Compared to PET fiber, when the content of PCS-MWNTs was 0.9 wt.%, the PCS-MWNTs/PET fibers exhibited an efficient flame-retardant capacity, with the lower heat release rate and total release rate values of 81.03 kW/m² and 39.05 MJ/m², respectively, decreasing by 130.06 kW/m² and 11.87 MJ/m². The thermal stability of PCS-MWNTs/PET fibers strengthened, and the char residue increased from 7.21 to 13.52%. Compared to MWNTs/PET fiber, the crystallization property and tensile strength of PCS-MWNTs/PET fiber improved, because of the good dispersion and strong interface binding force with the PET fiber. Overall, the PCS layer endowed the MWNTs with good dispersion and flame-retardant characteristics.     

Hydrothermal Treatment of Wool Fibers with Tetrabutyl Titanate and Chitosan

In order to improve the dye depth of TiO₂-modified wool fibers, chitosan is incorporated with tetrabutyl titanate in preparing the nanosized TiO₂ particles, which are loaded on the surfaces of wool fibers, during hydrothermal process. The TiO₂ coated wool fibers are subsequently dyed with Lansol Blue 3G. The structural changes of wool fibers before and after treatments are characterized by several techniques, such as field emission scanning electron microscope, energy-dispersive X-ray, transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis, and diffuse reflectance spectrum. The properties of tensile, antibacterial activity, yellowness and whiteness indices, dye uptake, K/S value, color fastness to washing, rubbing, and artificial light are also compared. It is found that the as-prepared TiO₂ particles with pure anatase phase are easy to agglomerate because of the introduction of chitosan. Meanwhile, the aggregated particles are deposited on the surface of wool fibers via a simple hydrothermal route. Compared with the original wool fibers, the thermal behaviors of the TiO₂ coated wool fibers change slightly. The performances of UV protection, antibacterial activity, dyeing depth, and color fastness to wet rubbing and artificial light are improved to some degree. However, the tensile properties of wool fibers decrease but not too much.     

Chitosan/whey protein film as active coating to extend Ricotta cheese shelf-life

Shelf-life extension of Ricotta cheese coated with a chitosan/whey protein edible film and stored under modified atmosphere at 4 °C was evaluated. The chitosan/whey protein film had 35% and 21% lower oxygen and carbon dioxide permeability, respectively, and about three times higher water vapor permeability than film prepared with chitosan alone. Over a 30-day storage period, no differences in the pH of control and coated Ricotta cheeses were observed. While the titratable acidity of the control increased linearly during the first two weeks and remained constant for the rest of the storage period, the corresponding values for coated Ricotta cheese did not change significantly during the first 21 days and reached the acidity level (0.34 ± 0.02 milliequivalent/100 g of analyzed sample) of the control only on day 30. The viable numbers of lactic acid bacteria and mesophilic and psychrotrophic microorganisms were significantly lower (p < 0.05) in the chitosan/whey protein coated cheese, compared to the control, at each storage time. Our findings suggest a potential utility of chitosan/whey protein coatings to extend fresh dairy product shelf-life.     

乙酰化处理对含银甲壳胺纤维性能的影响

为改善含银甲壳胺纤维释放银离子的性能,用乙酸酐处理甲壳胺纤维后使纤维中的氨基转换成乙酰胺基,从而减弱纤维对银离子的结合力。比较了未处理纤维和几种不同取代度乙酰化甲壳胺纤维的吸水性及其释放银离子的性能。结果表明,乙酰化处理破坏了甲壳胺纤维的有序结构,使水分更容易进入纤维结构,部分乙酰化的甲壳胺纤维具有很高的吸水性能。由于乙酰化处理使自由氨基转换成乙酰胺基,随着乙酰化度的提高,处理后的甲壳胺纤维在遇水湿润后可释放出更多的银离子。     

Carbon nanotube-polytetrafluoroethylene nanocomposite coating for milk fouling reduction in plate heat exchanger

Cleaning of milk fouling on plate heat exchanger surface causes intermittent downtime to milk processing industry. Fouling occurrence during milk pasteurization potentially reduces the heat transfer rate of plate heat exchanger (PHE), leading to serious energy deficiency. In this study, the development of milk surface foulant was successfully inhibited by superhydrophobic nanoparticulate coating of PHE surfaces. Full dispersion of multiwalled carbon nanotubes (MWCNTs) in hydrophobic polytetrafluoroethylene (PTFE) matrix was completed using ultrasonication and high temperature annealing techniques. Nanomorphology and surface structure of PTFE and CNT-PTFE films on stainless steel surface were interpreted by field emission scanning electron microscope (FESEM). To validate the hydrophobicity of the developed CNT-PTFE nanocomposite coated surface, a water contact angle (WCA) using a simplified sessile drop method, correspondent surface energy, foulant mass, and energy efficiency after milk pasteurization were estimated and compared with stainless steel 316 and polytetrafluoroethylene (PTFE) coated surfaces. Static contact angles for the control, PTFE-coated and CNT-PTFE surfaces increased from 71.2 to 119.6 and 141.1°, respectively. By application of CNT-PTFE nanocomposite coating, the estimated surface energy of heat exchanger surface decreased by 97.0% of its original value. After continuous milk pasteurization for 5 h, the mass of foulant on CNT-PTFE coated heat exchanger surface was 70.3% less than that of the uncoated surface; thus, total energy consumption of test PHE unit also dropped down by 10.2%. Developed CNT-PTFE nanocomposite coated surface will potentially reduce the risk of under-processed milk and decrease the frequency of the routine cleaning-in-place (CIP) program.     

含茶多酚的壳聚糖涂膜对四季豆贮藏品质和 生理生化特性的影响

目的研究壳聚糖联合茶多酚对四季豆涂膜保鲜的可行性。方法以四季豆为实验材料,采用壳聚糖涂膜(浓度为1.5%)、壳聚糖联合茶多酚复合涂膜(1.5%壳聚糖中添加150 mg/kg茶多酚)2种保鲜方式,研究茶多酚对四季豆贮藏品质和生理生化特性的影响。结果茶多酚联合壳聚糖涂膜的四季豆在贮藏期内叶绿素、维生素C、水分含量的下降速率和纤维素含量的上升速率均低于壳聚糖涂膜组,贮藏品质较好。茶多酚联合壳聚糖涂膜的四季豆体内的过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)的活力低于壳聚糖涂膜组,但二者均高于未处理组。结论涂膜处理有利于四季豆的贮藏,涂膜剂中加入茶多酚后保鲜效果更好,和壳聚糖涂膜相比可将四季豆贮藏期延长10 d,和不涂膜组相比可延长20d。